Left Ventricular Outflow Tract Velocity Time Integral Research Articles

Correlation between corrected carotid flow time and left ventricular outflow tract velocity-time integral using a novel technique.

Transthoracic echocardiography (TTE) is widely used for assessing patients in the intensive care unit, with cardiac output measurement being crucial for hemodynamic monitoring. This is achieved by measuring the velocity-time integral (VTI) of the left ventricular outflow tract (LVOT), which serves as a surrogate of stroke volume. However, conducting TTE in the critical care setting presents several challenges. Our primary objective was to investigate the relationship between carotid corrected flow time (cCFT) and LVOT VTI. Additionally, we aimed to determine the threshold cCFT value that reliably predicts a normal LVOT VTI. This proof-of-concept study involves a post-hoc analysis from a diagnostic accuracy investigation conducted in a medical-surgical intensive care unit. We included patients admitted to the ICU from December 2021 to January 2022. We used a phased array transducer to measure the cCFT at the left supraclavicular fossa and the LVOT VTI in an apical 5-chamber view. We included 22 patients. The Spearman coefficient between LVOT VTI and cCFT was 0.82 (p < 0.0001). The area under the ROC curve for cCFT to predict LVOT VTI equal to or greater than 17 cm was 0.871 (95% CI 0.660-0.974). A cCFT exceeding 283 ms predicted LVOT VTI equal to or greater than 17 cm with a sensitivity of 93.3% (95% CI 68.1% to 99.8%) and specificity of 85.7% (95% CI 42.1% to 99.6%). The cCFT, measured using a novel technique with a phased array transducer, shows a strong correlation with LVOT VTI. Additionally, cCFT predicts a normal LVOT VTI with good sensitivity and specificity in critically ill patients. Larger studies are warranted to validate these findings.

Centhaquine Increases Stroke Volume and Cardiac Output in Patients with Hypovolemic Shock.

Introduction: Centhaquine is a resuscitative agent that acts on α2B adrenergic receptors. Its effect on cardiac output in hypovolemic shock patients has not been reported. Methods: This pilot study was conducted in 12 hypovolemic shock patients treated with centhaquine who participated in an open-label phase IV study (NCT05956418). Echocardiography was utilized to measure stroke volume (SV), cardiac output (CO), left ventricular outflow tract velocity time integral (LVOT-VTI) and diameter (LVOTd), heart rate (HR), left ventricular ejection fraction (LVEF) and fractional shortening (LVFS), and inferior vena cava (IVC) diameter before (0 min) and 60, 120, and 300 min after centhaquine (0.01 mg/kg) iv infusion for 60 min. Results: SV was significantly increased after 60, 120, and 300 min. CO increased significantly after 120 and 300 min despite a decrease in HR. IVC diameter and LVOT-VTI at these time points significantly increased, indicating the increased venous return. LVEF and LVFS did not change, while the mean arterial pressure (MAP, mmHg) increased after 120 and 300 min. Positive correlations between IVC diameter and SV (R2 = 0.9556) and between IVC diameter and MAP (R2 = 0.8928) were observed, which indicated the effects of an increase in venous return on SV, CO, and MAP. Conclusions: Centhaquine-mediated increase in venous return is critical in enhancing SV, CO, and MAP in patients with hypovolemic shock; these changes could be pivotal for reducing shock-mediated circulatory failure, promoting tissue perfusion, and improving patient outcomes. Trial Registration: CTRI/2021/01/030263 and NCT05956418.

Low left ventricular outflow tract velocity time integral predicts normotensive shock in patients with acute pulmonary embolism

Abstract Funding Acknowledgements None. Introduction In patients with intermediate-risk acute pulmonary embolism (PE) outcomes vary widely, with mortality rates ranging from 3-15% and rates of normotensive shock up to 30%.1-3 Current risk models don't fully capture those at higher risk and identify patients who may benefit from advanced therapies. The left ventricular outflow tract (LVOT) velocity time integral (VTI), a surrogate marker of cardiac output, has been associated with increased mortality in acute PE.4 Our objective was to determine the association between LVOT VTI and its predictive value in identifying normotensive shock in this patient population. Methods Patients who underwent percutaneous mechanical thrombectomy (MT) between August 2020 and March 2023 at a large academic public hospital were considered for the study. Inclusion criteria comprised of normotensive patients (SBP ≥ 90 mmHg) with invasive measures of cardiac index (CI). VTI was obtained by pulsed wave doppler at the LVOT in either the apical 3 or apical 5 chamber view. The primary outcome was the association between LVOT VTI and normotensive shock and a cut off of 15 cm was used to examine this association based on prior studies.4 Results A total of 49 patients with intermediate-risk PE underwent MT, 16 patients had incomplete data, resulting in a final cohort of 33 patients (mean age: 57 ± 13yrs; 38% female). Patients with LVOT VTI of &amp;lt;15 cm were younger (53 vs 62 years p=0.02), had lower systolic blood pressure at presentation (122 vs 134 mmHg, p=0.047), higher heart rate (112.6 vs 96.2 beats/min, p=0.008), a higher composite shock score (CPES) (5 vs 3, p=0.012), lower cardiac index (1.9 vs 3.1 L/min/m2, p&amp;lt;0.001), a higher PASP (61.4 vs 48.9 mmHg, p=0.018), and higher rates of elevated lactate (90% vs 42%, p=0.027). LVOT VTI threshold of &amp;lt;15cm effectively identified patients with normotensive shock (90% vs 8% p&amp;lt;0.001). There was no statistically significant difference in the rates of saddle emboli, left ventricular ejection fraction, sPESI and BOVA scores in patients with VTI above or below 15cm. In patients with normotensive shock, 19/20 (95%) had LVOT VTI ≤ 15cm with a median of 13 cm (IQR 12, 14) (Figure). In patients without normotensive shock, 11/13 (84%) had LVOT VTI &amp;gt;15 with a median of 18 (IQR 17, 21). The area under the curve for LVOT VTI ≤ 15 cm in predicting normotensive shock was 0.89. The sensitivity and specificity of LVOT VTI ≤ 15 cm in predicting normotensive shock was 91.6% and 90.4% respectively. Conclusion Our study suggests that LVOT VTI is a reliable surrogate for cardiac output in patients with acute PE and can effectively identify those in the intermediate-risk group who are at risk for normotensive shock. A LVOT VTI &amp;lt;15cm may identify intermediate-risk patients at higher risk for hemodynamic decompensation and further studies are needed to evaluate whether these patients would benefit from upfront catheter-based therapies.

Risk assessment by acute bedside echocardiography prior to acute coronary angiography in patients with ST-elevation myocardial infarction: a feasibility study

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Novo Nordisk Foundation. Background Early risk assessment by hemodynamic measurements in patients with ST-elevation myocardial infarction (STEMI) could be useful for early detection of patients at risk of developing hemodynamic instability after primary percutaneous coronary intervention (pPCI). Anterior STEMI patients have larger infarct size and may be of particular interest. Transthoracic echocardiography (TTE) is a quick, non-invasive, and available tool, however, evidence regarding the use of acute TTE prior to acute coronary angiography (CAG) is limited. Purpose To assess the feasibility of acute bedside hemodynamic assessment in the cath. lab. by TTE in addition to clinical examination, and blood samples in STEMI patients without CS at arrival in the cath. lab. Methods STEMI patients without CS at hospital arrival and treated with pPCI were included in the study during a five week period. Clinical examination (Killip class), blood sampling (lactate, troponin T (TNT), proB-type natriuretic peptide (proBNP), and focused bedside 2D TTE with Doppler were performed prior to the acute CAG. The TTE protocol was focused (approx. 5 minutes) on hemodynamic measurements, infarction related complications, and differential diagnoses e.g. aortic dissection. The TTE was performed during preparation for the acute CAG. Patients were stratified in anterior- vs. non-anterior STEMI based on the culprit artery and prehospital ECG. Feasibility was estimated by all of the following echocardiographic parameters; left ventricular ejection fraction (LVEF), left ventricular outflow tract (LVOT) velocity time integral (VTI), and right ventricular function (tricuspid annular plane systolic excursion (TAPSE)). Results A total of 60 STEMI patients (aged mean 63 years, 18% female) were included, and 47% had an anterior STEMI. No differences in baseline characteristics between the two groups were found including comorbidities, clinical parameters, and time from cath. lab. arrival to first wire over the culprit lesion (median (IQR) 28 (23; 38) vs 32 (24; 40) minutes). Admission biomarkers of blood glucose, lactate, and proBNP plasma concentrations were similar between the two groups. Whereas admission TNT were higher for patients with anterior STEMI (median (IQR) 110 (37; 449) vs. 37 (20; 94) ng/L, p=0.01). The feasibility of TTE-study protocol was 93%. Patients with anterior STEMI had lower LVEF (mean: 36±11 vs. 48±9%, p=0.0003; missing: n=0), and a trend to lower LVOT VTI (19 (6.4) vs. 22 (5.0) cm, p=0.06; missing: n=4). No difference in parameters of diastolic function or TAPSE (missing: n=0) were found. None of the included patients had echocardiographic visible complications related to the infarction. Conclusion Acute TTE is to a high degree feasible and does not delay time to acute revascularization in STEMI patients. Patients with anterior STEMI have significantly higher admission TNT levels, lower LVEF, and a trend to lower LVOT VTI compared with non-anterior STEMI patients.

Diagnostic accuracy of left ventricular outflow tract velocity time integral versus inferior vena cava collapsibility index in predicting post-induction hypotension during general anesthesia: an observational study.

Point of care ultrasound (POCUS) is being explored for dynamic measurements like inferior vena cava collapsibility index (IVC-CI) and left ventricular outflow tract velocity time integral (LVOT-VTI) to guide anesthesiologists in predicting fluid responsiveness in the preoperative period and in treating post-induction hypotension (PIH) with varying accuracy. In this prospective, observational study on included 100 adult patients undergoing elective surgery under general anesthesia, the LVOT-VTI and IVC-CI measurements were performed in the preoperative room 15 minutes prior to surgery, and PIH was measured for 20 minutes in the post-induction period. The incidence of PIH was 24%. The area under the curve, sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of the two techniques at 95% confidence interval was 0.613, 30.4%, 93.3%, 58.3%, 81.4%, 73.6% for IVC-CI and 0.853, 83.3%, 80.3%, 57.1%, 93.8%, 77.4% for LVOT-VTI, respectively. In multivariate analysis, the cutoff value for IVC-CI was >51.5 and for LVOT-VTI it was ≤17.45 for predicting PIH with odd ratio [OR] of 8.491 (P=0.025) for IVCCI and OR of 17.427 (P<0.001) for LVOT. LVOT-VTI assessment was possible in all the patients, while 10% of patients were having poor window for IVC measurements. We recommend the use of POCUS using LVOT-VTI or IVC-CI to predict PIH, to decrease the morbidity of patients undergoing surgery. Out of these, we recommend LVOT-VTI measurements as it has showed a better diagnostic accuracy (77.4%) with no failure rate.

Association of Shock Index with Echocardiographic Parameters in Cardiac Intensive Care Unit

BackgroundA high shock index (SI), the ratio of heart rate (HR) to systolic blood pressure (SBP), has been associated with unfavorable outcomes. We sought to determine the hemodynamic underpinnings of an elevated SI using 2-D and doppler Transthoracic Echocardiography (TTE) in unselected cardiac intensive care unit (CICU) patients. MethodsWe included Mayo Clinic CICU admissions from 2007 to 2018 who were in sinus rhythm at the time of TTE. The SI was calculated using HR and SBP at the time of TTE. Patients were grouped according to SI: <0.7, 4012 (64%); 0.7–0.99, 1764 (28%); and ≥ 1.0, 513 (8%). Pearson's correlation coefficient was used to assess associations between continuous variables. ResultsWe included 6289 unique CICU patients, 58% of whom had acute coronary syndrome. The median age was 67.9 years old and 37.8% were females. The mean SI was 0.67 BPM/mmHg. As the SI increased, markers of left ventricular (LV) systolic function and forward flow decreased, including left ventricular ejection fraction (LVEF), fractional shortening, left ventricular outflow tract (LVOT) velocity time integral (VTI), stroke volume, LV stroke work index, and cardiac power output. Biventricular filling pressures increased, and markers of right ventricular function worsened with rising SI. Most TTE measurements reflecting LV function and forward flow were inversely correlated with SI, including LV stroke work index (r = −0.59) and LVOT VTI (r = −0.41), as were both systemic vascular resistance index (r = −0.43) and LVEF (r = −0.23). ConclusionCICU patients with elevated SI have worse biventricular function and systemic hemodynamics, particularly decreased stroke volume and related calculated TTE parameters. The SI is an easily available marker that can be used to identify CICU patients with unfavorable hemodynamics who may require further assessment.

Impact of Premature Ventricular Complex (PVC) Burden on the Left Ventricle in the Structurally Normal Heart: Hemodynamic Alterations of Idiopathic PVC on Echocardiography.

Premature ventricular complex (PVC) without structural heart disease is mostly viewed as a benign arrhythmia. However, the high burden of PVC causes cardiomyopathy due to intraventricular dyssynchrony. The effects of ectopic contraction on left ventricular (LV) hemodynamics in the structurally normal heart are unclear. To examine the effect of PVC burden on LV dimension, LV systolic function, and intraventricular blood flow, and to determine whether ectopic ventricular contraction affects LV hemodynamics. Patients aged ≥ 18 years with PVC ≥ 5% on Holter recording were enrolled and divided into groups G1 (5-10%), G2 (10-20%), and G3 (≥ 20%). We excluded patients with structural heart diseases, pacemakers, and LV systolic dysfunction [LV ejection fraction (LVEF) < 50%]. Clinical characteristics and routine transthoracic echocardiography parameters were compared. The end-systolic LV internal dimension increased according to the PVC burden from G1 to G3 (p = 0.001). LVEF was inversely associated with PVC burden from G1 to G3 (p = 0.002). The same pattern was seen for LV outflow tract (LVOT) maximal velocity (p = 0.005) and maximal pressure gradient (PG) (p = 0.005), LVOT velocity time integral (VTI) (p = 0.03) and LV stroke volume index (LVSI) (p = 0.008). Systolic function and LV end-systolic dimension were inversely associated with PVC burden. Decreased LVOT flow velocity and PG were related to increased PVC burden. LVOT VTI and LVSI were smaller when the PVC burden exceeded 20%. These negative hemodynamic manifestations of idiopathic PVC were considerable even in structure normal hearts, hence the early elimination of PVC is strongly advised.

Fluid Responsiveness in Critically Ill Patients Using Carotid Peak Systolic Velocity Variability: A New Frontier.

Background and objectives A fluid responder is a patient who can increase his stroke volume/ cardiac output by more than 10%-15% after a fluid bolus. Left ventricular outflow tract (LVOT) velocity time integral (VTI) variability is widely used as an adynamic parameter of fluid responsiveness, but a transthoracic echo view of LVOT VTI is often time-consuming and, at times, difficult to achieve. So, in the quest for another parameter that might equally be a good surrogate marker of stroke volume variation, carotid peak systolic velocity (CPSV) variation has been studied. The objective was to assess CPSV variation in patients who are already fluid responders. Methods The sample size was calculated considering a minimum correlation coefficient of 0.5. Adult patients in whom the physician wanted to give a fluid bolus and whose average LVOT VTI was more than 15% over 3 respiratory cycles were included in the study. Demographic variables, along with hemodynamic parameters such as heart rate, blood pressure, the need for vasopressors, mode of breathing (spontaneous or mechanical ventilation), andCPSV variation,were noted and averaged over three respiratory cycles. Fluid bolus (Plasmalyte) 6 ml/kg bolus over 10-15 minutes. Post-fluid hemodynamic variables, along with averaged LVOT VTI over three respiratory cycles and averaged CPSV variation over three respiratory cycles, are noted. Results Thirty adult patients were evaluated in the study. In spontaneously breathing patients (n=12), the average CPSV variation expressed as mean + standard deviation before and after fluid administration of 6ml/kg of ideal body weight was 14.1 ± 3.4 and 5.4 ± 2.6, respectively (p < 0.05). In mechanically ventilated patients (n=18), the average CPSV variation expressed as mean + standard deviation before and after fluid administration of 6ml/kg of ideal body weight fluid was 15 ± 5.3 and 6.5 ± 3.1, respectively (p <0.005). Overall, there was a statistically significant positive correlation between LVOT VTI variation and CPSV variation before fluid therapy (correlation coefficient 0.56 and p-value 0.001) and a statistically significant moderate positive correlation post-fluid therapy (correlation coefficient 0.37 and p-value 0.043). Conclusion We found a significant decrease in CPSV variation post-fluid administration in patients who are fluid responders, which mimics a decrease in stroke volume variation after fluid administration in patients who are fluid responsive.

A simplified echocardiographic formula to estimate cardiac index in the intensive care unit

Abstract Funding Acknowledgements Type of funding sources: None. Background Measurement of cardiac index (CI) is crucial in the hemodynamic assessment of critically ill patients. Pulmonary artery catheterization (PAC) remains the gold standard for CI evaluation, but it's invasive. Doppler trans-thoracic echocardiography (TTE) has been proposed as an accurate bedside non-invasive alternative to PAC for CI estimation, based on measurement of left ventricular outflow tract velocity time integral (LVOT-VTI) and diameter (LVOT-d). However, intrinsic limits of geometrical assumptions and practical limitations related to the intensive care unit (ICU) setting may lead to inaccurate CI calculation, mainly due to errors in LVOT-d. A body surface area (BSA)-based formula to predict LVOT-d has been proposed and validated. Including the predicted LVOT-d in the CI equation we obtained a new "simplified formula" for TTE CI estimation: CI=2,17*LVOT-VTI*HR/1000. Purpose This study aimed to assess the accuracy of a new TTE-based simplified formula, only requiring LVOT-VTI and HR, for TTE estimation of CI. Methods We prospectively enrolled all consecutive patients admitted to the ICU requiring PAC from January to December 2021 (n=74). We measured TTE-based CI method using both the "traditional formula" (traditional CI TTE) and the new "simplified formula" (simplified CI TTE), and compared the accuracy of both with the PAC-derived CI (CI PAC) as the reference method. Results As shown in Figure 1a, there was a moderate correlation (r = 0.70, p &amp;lt; 0.001) between traditional CI TTE and the CI PAC. A plot of the differences between traditional CI TTE and the CI PAC is illustrated in Figure 2a, resulting in a mean difference of -0.18 ± 0.58 L/min/m2, and 95% limits of agreement of -1.32 to +0.96 L/min/m2. The correlation between simplified CI TTE and CI PAC was strong (r = 0.81, p &amp;lt; 0.001) (Figure 1b) and resulted significantly greater than the traditional CI TTE and CI PAC correlation (p &amp;lt; 0.05). On Bland-Altman plot analysis (Figure 2b), the mean difference between simplified CI TTE and CI PAC was +0.19 ± 0.48 L/min/m2 with 95% limits of agreement of -0.74 to +1.13 L/min/m2. Conclusion In this study, we validated an easy-to-use and practical approach, leveraging on TTE LVOT-VTI and HR only, for non-invasive estimation of CI in ICU patients. In this peculiar setting, our formula was more reliable than the traditional CI TTE formula. However, despite the strong correlation with CI PAC, our formula introduces a slight but systematic overestimation of CI (+0.19 L/min/m2), as illustrated in the Bland-Altman plot. Therefore, this formula may be particularly useful in longitudinal CI assessment rather than precisely quantifying CI on a single measurement. This approach may thus be apt to quickly assess the hemodynamic response to pharmacological and mechanical supports during longitudinal assessment.

Efficacy and Safety of Leadless Pacemakers for Atrioventricular Synchronous Pacing: A Systematic Review and Meta-Analysis

Leadless pacemakers with an atrioventricular synchrony algorithm represent a novel technology for patients qualified for VDD pacing. The current evidence of their performance is limited to several small-scale observational studies. This systematic review and meta-analysis aimed to evaluate the efficacy and safety of this new technology. We systematically searched the PubMed, Embase, and Cochrane library databases from their inception to 12 September 2022. The primary efficacy outcome was atrioventricular synchrony after implantation, whereas the secondary efficacy outcome was the change in cardiac output represented by the left ventricular outflow tract velocity time integral (LVOT-VTI). The primary safety outcome was major complications related to the procedures and the algorithm. Means or mean differences with 95% confidence interval (95% CI) were combined using a random-effects model or a fixed-effects model. Finally, 8 published studies with 464 participants were included in the qualitative analysis. The pooled atrioventricular synchrony proportion was 78.9% (95% CI 71.9-86.0%), and a further meta-regression did not screen factors that contributed significantly to the heterogeneity. Additionally, a significant increase in atrioventricular synchrony of 11.3% (95% CI 7.0-15.7%, p < 0.01) was achieved in patients experiencing programming optimization. LVOT-VTI was significantly increased by 1.9 cm (95% CI 1.2-2.6, p < 0.01), compared with the VVI pacing mode. The overall incidence of complications was approximately 6.3%, with major complications related to the algorithm being extremely low. Overall, leadless pacemakers with atrioventricular synchronous pacing demonstrated favorable safety and efficacy. Future data on their long-term performance are required to facilitate their widespread adoption in clinical practice.

End-expiratory Occlusion Test and Mini-fluid Challenge Test for Predicting Fluid Responsiveness in Acute Circulatory Failure.

Predicting which patients with acute circulatory failure will respond to the fluid by an increase in cardiac output is a daily challenge. End-expiratory occlusion test (EEOT) and mini-fluid challenge (MFC) can be used for assessing fluid responsiveness in patients with spontaneous breathing activity, cardiac arrhythmias, low-tidal volume and/or low lung compliance. The objective of the study is to evaluate the value of EEOT and MFC-induced rise in left ventricular outflow tract (LVOT) velocity time integral (VTI) in predicting fluid responsiveness in acute circulatory failure in comparison to the passive leg-raising (PLR) test. Hundred critically ill ventilated and sedated patients with acute circulatory failure were studied. LVOT VTI was measured by transthoracic echocardiography before and after EEOT (interrupting the ventilator at end-expiration over 15 s), and before and after MFC (100 ml of Ringer lactate was infused over 1 min). The variation of LVOT VTI after EEOT and the MFC was calculated from the baseline. Sensitivity, specificity, and area under the receiver-operating characteristic (AUROC) curve of LVOT VTI after EEOT and MFC to predict fluid responsiveness were determined. After PLR, stroke volume (SV) increased by ≥12% in 49 patients, who were defined as responders and 34 patients in whom the increase in SV <12% were defined as nonresponders. A cutoff of 9.1% Change in VTI after MFC (ΔVTIMFC) predicted fluid responsiveness with an AUROC of 0.96 (P < 0.001) with sensitivity and specificity of 91.5% and 88.9%, respectively. Change in VTI after EEOT (ΔVTIEEOT) >4.3% predicted fluid responsiveness with sensitivity and specificity 89.4% and 88.9%, respectively, with an AUROC of 0.97 (P < 0.001), but in 17 patients, EEOT was not possible because triggering of the ventilator by the patient's inspiratory effort. In conclusion, in mechanically ventilated patients with acute circulatory failure Δ VTIMFC and Δ VTI EEOT accurately predicts fluid responsiveness.

The Role of Left Ventricular Ejection Fraction and Left Ventricular Outflow Tract Velocity-Time Integral in Assessing Cardiovascular Impairment in Septic Shock.

Background: the role of echocardiography in septic shock remains controversial, since depressed cardiac afterload may overestimate left ventricular (LV) systolic performance and mask septic cardiomyopathy (SC). We hypothesized that afterload-adjusted LV ejection fraction (LVEF) and LV outflow tract velocity-time integral (VTI) values for given systemic vascular resistances (SVR) could provide novel insights into recognizing and stratifying the severity of SC. Methods: in this observational, monocentric study, we prospectively included 14 mechanically-ventilated patients under septic-shock who all had a Pulse index Continuous Cardiac Output (PiCCO) system in place for hemodynamic monitoring. Echocardiographic and PiCCO longitudinal examinations (71 measurements overall) were performed simultaneously at the onset of septic shock and every 12 h for 60 h overall. Results: VTI-derived stroke volume (SV) and cardiac output (CO) were significantly correlated with PiCCO measurements (r ≥ 0.993, both p < 0.001). LVEF and VTI showed linear and exponential inverse correlation to SVR (R2 = 0.183 vs. 0.507 and p < 0.001 vs. p < 0.001, respectively). The equations LVEF = 86.168 − 0.011 × SVR and VTI = 41.23 × e(−0.0005×SVR) were found to provide “predicted” values for given SVR. Measured to predicted LVEF ratios (for given SVR), the afterload-adjusted LVEF defined the severity of SC (mild ≥ 90%, 80% ≤ moderate < 90% and severe < 80%). Mild SC demonstrated normal/supra-normal LVEF, normal VTI and SVR. Moderate SC showed lower LVEF and SVR, yet increased LV end-diastolic volume (LVEDV), VTI, SV and CO compared with mild SC (all p < 0.05). Severe SC was distinguished from moderate SC by markedly reduced LVEF, LVEDV, VTI, SV, CO and significantly increased SVR (all p < 0.05). LVEF and VTI decreased over time in mild SC, LVEF decreased in moderate SC, and LVEF and VTI increased over time in severe SC (p ≤ 0.038). LVEF and VTI demonstrated significant performance in identifying severe SC [cut-off < 61.5%, area under the curve (AUC) = 1 ± 0.0, sensitivity/specificity = 100/100, p < 0.001 vs. cut-off < 17.9 cm, AUC = 0.882 ± 0.042, sensitivity/specificity = 80/77, p < 0.001, respectively]. VTI but not LVEF demonstrated significant diagnostic performance in identifying both SVR < 800 dynes·s·cm−5 and SVR > 1500 dynes·s·cm−5 (cut-off > 24.46 cm, AUC = 0.889 ± 0.049, sensitivity/specificity = 75/100, p < 0.001; cut-off < 16.8, AUC = 0.0.857 ± 0.082, sensitivity/specificity = 83/86, p = 0.002, respectively).Conclusions: our study suggests that ICU bedside echocardiographic assessment of LVEF, VTI and their adjusted to corresponding SVR values provides valuable insights for the comprehension of SC phenotypes, underlying vasoplegia and cardiac output fluctuations in septic shock.

Clinical and prognostic significance of left ventricular outflow tract velocity time integral (LVOT-VTI) in patients with chronic heart failure

Abstract Background The echocardiographic evaluation of cardiac output relies on the product of the flow across the left ventricular outflow tract (LVOT), estimated through its velocity time integral (LVOT-VTI), and its cross-sectional area, estimated through the formula πr2. Considering the geometrical assumption behind such formula, LVOT-VTI has been proposed as a more reproducible surrogate of cardiac systolic function and showed prognostic value in the critical care setting. However, the role of such measure in patients with chronic heart failure (HF) remains unexplored. Objective To assess the clinical and prognostic significance of LVOT-VTI in a contemporary cohort of patients with chronic HF. Methods Outpatients with chronic HF with a LV ejection fraction &amp;lt;50% were prospectively enrolled to undergo a clinical, echocardiographic, and biohumoral assessment, and were followed-up for the endpoint of all-cause death. Results Finally, 971 patients were enrolled (71±12 years, 72% men, 50% ischemic etiology, LVEF 35±9%). Most patients showed a NYHA class I-II (74%) and were treated with ACE-inhibitors/ARBs or ARNI (81%), beta-blockers (95%), and mineralocorticoid receptor antagonists (71%). Patients were distinguished in three subgroups according to LVOT-VTI tertiles &amp;lt;19 (n=324), 19–24 (n=324), or ≥24 (n=323). Compared with the other two subgroups, patients with LVOT-VTI &amp;lt;19 showed worse NYHA class, lower LVEF and tricuspid annular plane systolic excursion (TAPSE), and higher E/e', left atrial volume index (LAVi), estimated systolic pulmonary arterial pressure (sPAP), and NT-proBNP concentration (all p&amp;lt;0.001). No differences were observed as for patients' age, HF etiology, and therapies (all p&amp;gt;0.05). Over a median follow-up of 22 (9–34) months, 103 (11%) patients met the primary endpoint. LVOT-VTI significantly stratified the risk of death, observing 65 (20%), 21 (7%), and 17 (5%) events across the subgroups with values &amp;lt;19, 19–24, or ≥24 (log-rank 33, p&amp;lt;0.001). At multivariable regression analysis, LVOT-VTI &amp;lt;19 (HR 2.06 [95% 1.21–3.49], p=0.008), but not LVEF &amp;lt;30% (p=0.614) was an independent predictor of all-cause death in a model adjusted for age, sex, ischemic etiology, renal function, hemoglobin, E/e', LAVi, TAPSE, sPAP, and NT-proBNP. Conclusion LVOT-VTI is associated with disease severity and is a strong predictor of all-cause death in patients with chronic HF. Funding Acknowledgement Type of funding sources: None.

Aortic valve morphology and the double envelope phenomenon in continuous Doppler echocardiography of aortic stenosis: a computerized model

Abstract Introduction Visualization of a double envelope (DE) is a relatively common issue in aortic transvalvular continuous-wave Doppler (CW) traces. In 1997, Song et al proposed that velocity time integral (VTI) measured at the edge of the inner envelope (IE) might equal that of the left ventricular outflow tract (LVOT). This surrogate measurement would be especially interesting in patients with irregular heart rhythms, as both LVOT and valvular VTIs could be obtained from the same beat, thus avoiding inter-beat variability when assessing aortic valve area (AVA) with continuity equation. In contrast, based on clinical data and 3D-printed models, they raised concern that DE method in dome-shaped valves could lead to significant overestimation of LVOT velocities (about 40%). Later studies, including a Partner trial subanalysis, question the validity of this measurement. Purpose We created a computerized aortic valve model to reproduce the CW tracing, and analysed how valve morphology may lead to a valid, well defined inner envelope or, by contrast, produce overestimation of LVOT velocities. Methods The simulation code was created using Python (v3.9.6) along with NumPy and Matplotlib libraries. For each simulation, an aortic valve scheme was created (LVOT diameter: 2 cm; TSVI length: 1 cm; LVOT peak velocity 1.1 m/s; varying morphologies and lengths of the aortic cusps). The longitudinal axis between LVOT base and valve tip was divided in sections or levels (at least 300 per emulation). To recreate the CW trace, for each level, luminal diameter and peak velocity (according to continuity equation) were calculated, and an array of points was generated representing the aortic waveform during the entire systole. Slight random dispersion (standard deviation 0.05 times original values) was added to produce a more realistic image. Data points were represented as scatter plot over black background with transparency, simulating CW tracings (Figure 1) Results Figure 2 represents the plots of various aortic valve configurations (1st row AVA 1.6 cm2; 2nd: 1.2 cm2; 3rd: 0.8 cm2). Note that the innermost portion of the trace results in hollow space, as these velocities are produced in portions of ventricle and aorta which are not included in the simulation. Pink dashed line represents actual LVOT velocities. In a short-length flat valve (A), the IE is well defined and shows good correlation with LVOT velocity. In a cone-shaped 6mm length valve (B), there is a progressive brightness reduction, with no recognizable contour. With long (6 mm) dome-shaped valves, an ill-defined IE is produced at higher velocities than LVOT, which could result in overestimation. Conclusion DE method could accurately assess LVOT velocities when a sharp-defined IE is present and a dome-shaped valve can be excluded (e.g. rheumatic or some bicuspid valves). Measurements in a blurred DE or in a dome-shaped valve would produce overestimation of LVOT velocities and AVA. Funding Acknowledgement Type of funding sources: None.

Accuracy of continuity equation in aortic stenosis and irregular heart rhythm (5–10 beats average)

Abstract Introduction Continuity equation is the cornerstone of aortic valve area (AVA) calculation in patients with aortic stenosis (AS). In patients with irregular rhythms (IR) - especially atrial fibrillation (AF)-, values of velocity-time integral (VTI) at left ventricular outflow tract (LVOT) and aortic valve (AV) vary between heart beats. The usual recommendation is to average the measurements of 5 or 10 beats in both locations. However, original papers describing continuity equation, from which that recommendation arises (refs 1 &amp; 2), only included 3 and 2 AF patients, respectively. To our knowledge, there are not clinical studies to support this procedure and its accuracy has not been established. In contrast, in a previous study our team had evaluated the accuracy of the double envelope technique to assess both LVOT and AV VTI in the same beat, with a 7.8% (CI 95%: 5.8–10.3) difference (error) in the estimation of AVA when compared to pulsed wave of LVOT in patients with stable sinus rhythm. Purpose To evaluate how dispersion in VTIs due to IR impacts on variability of AVA calculations. Methods For each patient, we recorded multiple measurements of VTI in both LVOT and AV (mean 36.8 beats, range 29–47) per patient and location). Reference AVA was estimated using the average of all these measurements. To estimate the accuracy of averaging 5 or 10 heart beats, we created a computer code which simulated the AVA calculation using random samples of these measurements, and calculated the difference between true AVA and that obtained in the simulation (expressed as percentage of the true value). The process was iterated 10,000 times to obtain the distribution of differences and to estimate its mean value. Data handling and graphic representation was performed with Python 3.9.6 and Pyodbc, Pandas, NumPy, Matplotlib and Seaborn libraries. Results We included data from 8 patients with AS and IR (Age: 71 to 89, mean 82.5 years; Aetiology: degenerative (100%); Sex: 3 males / 5 females; Rhythm: AF [7], atrial flutter [1]; Severity: severe [3], moderate [4], mild [1]). Mean difference in AVA calculations was 8.2% (range: 5.1–13.5%). With 10 beats, mean difference was 5.7% (range: 3.6–9.5%). Figute 1 shows violin plot with distribution in each patient of recorded VTIs at both AV (left) and LVOT (right). To ease visualization, data are expressed as percentage of mean values. Fig 2 shows how that variability results in inaccuracy of AVA calculations with 5 (left) or 10 beats (right). Note that in many cases, possible results are located on both sides of the severity threshold of 1 cm2 (red line). Conclusion AVA assessment using 5 beats average results in a mean difference (error) of 8.2%, which can be reduced to a mean of 5.7% using 10 beats. These differences are comparable with the previously observed with the double envelope technique (7.8%). Funding Acknowledgement Type of funding sources: None.

Artificial intelligence (AI) versus expert: A comparison of left ventricular outflow tract velocity time integral (LVOT-VTI) assessment between ICU doctors and an AI tool.

PurposeThe application of point of care ultrasound (PoCUS) in medical education is a relatively new course. There are still great differences in the existence, quantity, provision, and depth of bedside ultrasound education. The left ventricular outflow tract velocity time integral (LVOT‐VTI) has been successfully used in several studies as a parameter for hemodynamic management of critically ill patients, especially in the evaluation of fluid responsiveness. While LVOT‐VTI has been broadly used, valuable applications using artificial intelligence (AI) in PoCUS is still limited. We aimed to identify the degree of correlation between auto LVOT‐VTI and the manual LVOT‐VTI acquired by PoCUS trained ICU doctors.MethodsAmong the 58 ICU doctors who attended PoCUS training from 1 September 2019 to 30 November 2020, 46 ICU doctors who trained for more than 3 months were enrolled. At the end of PoCUS training, each of the enrolled ICU doctors acquired echocardiography parameters of a new ICU patient in 2 h after new patient was admitted. One of the two bedside expert sonographers would take standard echocardiogram of new ICU patients within 24 h. For ICU doctors, manual LVOT‐VTI was obtained for reference and auto LVOT‐VTI was calculated instantly by using an AI software tool. Based on the image quality of the auto LVOT‐VTI, ICU patients was separated into ideal group (n = 31) and average group (n = 15).ResultsLeft ventricular end‐diastolic dimension (LVEDd, p = 0.1028), left ventricular ejection fraction (LVEF, p = 0.3251), left atrial dimension (LA‐d, p = 0.0962), left ventricular E/A ratio (p = 0.160), left ventricular wall motion (p = 0.317) and pericardial effusion (p = 1) had no significant difference between trained ICU doctors and expert sonographer. ICU patients in average group had greater sequential organ failure assessment (SOFA) score (7.33 ± 1.58 vs. 4.09 ± 0.57, p = 0.022) and lactic acid (3.67 ± 0.86 mmol/L vs. 1.46 ± 0.12 mmol/L, p = 0.0009) with greater value of LVEDd (51.93 ± 1.07 vs. 47.57 ± 0.89, p = 0.0053), LA‐d (39.06 ± 1.47 vs. 35.22 ± 0.98, p = 0.0334) and percentage of decreased wall motion (p = 0.0166) than ideal group. There were no significant differences of δLVOT‐VTI (|manual LVOT‐VTI – auto LVOT‐VTI|/manual VTI*100%) between the two groups (8.8% ± 1.3% vs. 10% ± 2%, p = 0.6517). Statistically, significant correlations between manual LVOT‐VTI and auto LVOT‐VTI were present in the ideal group (R2 = 0.815, p = 0.00) and average group (R2 = 0.741, p = 0.00).ConclusionsICU doctors could achieve the satisfied level of expertise as expert sonographers after 3 months of PoCUS training. Nearly two thirds of the enrolled ICU doctors could obtain the ideal view and one third of them could acquire the average view. ICU patients with higher SOFA scores and lactic acid were less likely to acquire the ideal view. Manual and auto LVOT‐VTI had statistically significant agreement in both ideal and average groups. Auto LVOT‐VTI in ideal view was more relevant with the manual LVOT‐VTI than the average view. AI might provide real‐time guidance among novice operators who lack expertise to acquire the ideal standard view.

Automated versus manual B-lines counting, left ventricular outflow tract velocity time integral and inferior vena cava collapsibility index in COVID-19 patients.

ABSTRACTBackground and Aims:The incorporation of artificial intelligence (AI) in point-of-care ultrasound (POCUS) has become a very useful tool to quickly assess cardiorespiratory function in coronavirus disease (COVID)-19 patients. The objective of this study was to test the agreement between manual and automated B-lines counting, left ventricular outflow tract velocity time integral (LVOT-VTI) and inferior vena cava collapsibility index (IVC-CI) in suspected or confirmed COVID-19 patients using AI integrated POCUS. In addition, we investigated the inter-observer, intra-observer variability and reliability of assessment of echocardiographic parameters using AI by a novice.Methods:Two experienced sonographers in POCUS and one novice learner independently and consecutively performed ultrasound assessment of B-lines counting, LVOT-VTI and IVC-CI in 83 suspected and confirmed COVID-19 cases which included both manual and AI methods.Results:Agreement between automated and manual assessment of LVOT-VTI, and IVC-CI were excellent [intraclass correlation coefficient (ICC) 0.98, P < 0.001]. Intra-observer reliability and inter-observer reliability of these parameters were excellent [ICC 0.96-0.99, P < 0.001]. Moreover, agreement between novice and experts using AI for LVOT-VTI and IVC-CI assessment was also excellent [ICC 0.95-0.97, P < 0.001]. However, correlation and intra-observer reliability between automated and manual B-lines counting was moderate [(ICC) 0.52-0.53, P < 0.001] and [ICC 0.56-0.69, P < 0.001], respectively. Inter-observer reliability was good [ICC 0.79-0.87, P < 0.001]. Agreement of B-lines counting between novice and experts using AI was weak [ICC 0.18, P < 0.001].Conclusion:AI-guided assessment of LVOT-VTI, IVC-CI and B-lines counting is reliable and consistent with manual assessment in COVID-19 patients. Novices can reliably estimate LVOT-VTI and IVC-CI using AI software in COVID-19 patients.

Two wrongs sometimes do make a right: errors in aortic valve stenosis assessment by same-day Doppler echocardiography and 4D flow MRI.

This study aims to systematically verify if the simplified geometry and flow profile of the left ventricular outflow tract (LVOT) assumed in 2D echocardiography is appropriate while examining the utility of 4D flow MRI to assess valvular disease. This prospective study obtained same-day Doppler echocardiography and 4D flow MRI in 37 healthy volunteers (age: 51.9 ± 18.2, 20 females) and 7 aortic stenosis (AS) patients (age: 64.2 ± 9.6, 1 female). Two critical assumptions made in echocardiography for aortic valve area assessment were examined, i.e. the assumption of (1) a circular LVOT shape and (2) a flat velocity profile through the LVOT. 3D velocity and shape information obtained with 4D flow MRI was used as comparison. It was found that the LVOT area was lower (by 26.5% and 24.5%) and the velocity time integral (VTI) was higher (by 28.5% and 30.2%) with echo in the healthy and AS group, respectively. These competing errors largely cancelled out when examining individual and cohort averaged LVOT stroke volume. The LVOT area, VTI and stroke volume measured by echo and 4D flow MRI were 3.6 ± 0.7 vs. 4.9 ± 1.0 cm2 (p < 0.001), 21.2 ± 3.0 vs 15.2 ± 2.8cm (p < 0.001), and 75.6 ± 15.6 vs 72.8 ± 14.1ml (p = 0.3376), respectively. In the ensemble average of LVOT area and VTI, under- and over-estimation seem to compensate each other to result in a 'realistic' stroke volume. However, it is important to understand that this compensation may fail. 4D flow MRI provides a unique insight into this phenomenon.

Echocardiographic Correlates of Mortality Among Cardiac Intensive Care Unit Patients With Cardiogenic Shock.

Prior studies have shown worse outcomes in patients with cardiogenic shock (CS) who have reduced left ventricular ejection fraction (LVEF), but the association between other transthoracic echocardiogram (TTE) findings and mortality in CS patients remains uncertain. We hypothesized that Doppler TTE measurements would outperform LVEF for risk stratification. Retrospective analysis of cardiac intensive care unit patients with an admission diagnosis of CS and a TTE within 1 day of admission. Hospital survivors and inpatient deaths were compared, and multivariable logistic regression was used to analyze the associations between TTE variables and hospital mortality. We included 1,085 patients, with a median age of 69.5 (59.6, 77.5) years; 37% were females and 62% had an acute coronary syndrome. Most patients (66%) had moderate or severe left ventricular (LV) systolic dysfunction, and 48% had moderate or severe right ventricular (RV) systolic dysfunction. Hospital mortality occurred in 31%, and inpatient deaths had a lower median LVEF (29% vs. 35%, P < 0.001). Patients with mild or no LV or RV dysfunction were at lower risk of adjusted hospital mortality (P < 0.01). The LV outflow tract (LVOT) velocity-time integral (VTI) was the single best predictor of hospital mortality. After multivariable adjustment, both the LVEF and LVOT VTI remained strongly associated with hospital mortality (P < 0.001). Early comprehensive Doppler TTE can provide important prognostic insights in CS patients, highlighting its potential utility in clinical practice. The LVOT VTI, reflecting forward flow, is an important measurement to obtain on bedside TTE.

Cardiac output monitoring using transthoracic echocardiography in children after cardiac surgery-an observational study of feasibility and concordance with transpulmonary thermodilution

Abstract Background Transthoracic echocardiography (TTE) is commonly used after pediatric cardiac surgery to monitor cardiac function and adequacy of surgery; however it depends on the availability of good echo window and operator skill [1]. Transpulmonary thermodilution (TPTD) is feasible along with calibrated continuous cardiac output measurement in children but seldom used due to cost and the need for a specialized catheter [2]. We hypothesized that TTE would be as good as TPTD, but limited in feasibility following pediatric cardiac surgery. Hence, the concordance, agreement as well as feasibility and trending of cardiac output monitoring by TTE was compared against a reference TPTD method in real-world usage in children after congenital heart surgery. Methods This was a secondary analysis of data from a previously registered and conducted study in our unit. TPTD monitoring was instituted in children undergoing congenital heart disease repair on cardiopulmonary bypass with a 3F femoral arterial cannula and a central venous injectate temperature sensor. Cardiac output was also measured by transthoracic echocardiography by measurement of the left ventricular outflow tract (LVOT) diameter, LVOT velocity time integral (VTI) and the heart rate as previously described [3,4]. Measurements were taken after arrival in the ICU, and every 12 hours till after extubation. Correlation, Bland-Altman analysis and polar analysis was done for cardiac output measured by TPTD and TTE. Results TTE and TPTD measurements of cardiac output correlated well (Pearson's correlation coefficient 0.94; 95% CI 0.90–0.96) (Fig. 1A). Bland Altman analysis showed a mean bias of 0.15 l/min and upper and lower limits of agreement of 0.81 and −0.51 l/min respectively (Fig. 1B). Cardiac output measurement by TTE was possible in 72 instances while TPTD allowed measurement in all 113 instances. Hence, TTE was not feasible in 41 instances across 14 patients, including 19 instances in acyanotic and 22 instances in cyanotic patients. Polar analysis revealed acceptable trending. Conclusions TTE derived cardiac output demonstrated good correlation, minimal bias and narrow limits of agreement versus TPTD, and was feasible in most cases. This suggests TTE is an acceptable cardiac output measurement modality post pediatric cardiac surgery, as in adults [5]. TPTD-based continuous cardiac output monitoring might have a complementary role in pediatric cardiac critical care, particularly in high risk cases. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): Institutional Special Research Grant from Postgraduate Institute of Medical Education and Research, Chandigarh, India. Figure 1