Left Ventricular Velocity Time Integral Research Articles

Echocardiographic evaluation of ventricular performance in VA-ECMO weaning: results from a observational multicentric prospective study

Abstract Funding Acknowledgements None. Background Although temporary mechanical circulatory support devices are increasingly used in the management of cardiogenic shock (CS), several open question regarding the kind of support and timing of institution/weaning remains open. Echocardiography is widely applied to drive the weaning process from VA-ECMO although there are no standardized protocols. Purpose We sought to evaluate the accuracy of echocardiographic indices in predicting successful weaning from VA-ECMO in CS patients. We tested total isovolumic time (tIVT), an index of ventricular performance(1,2), and longitudinal function (MAPSE) on top of the commonly used parameters (left ventricular ejection fraction, LVEF; E/e’ at mitral valve; left ventricular velocity time integral, LV VTI; TAPSE; right ventricular S’ at tissue Doppler imaging, RV S’). Methods Multicentric prospective study on adults receiving VA-ECMO due to refractory CS and/or cardiac arrest (CA) from 2012 to 2020. Echocardiography was performed at VA-ECMO placement and during the weaning trials. Waning trials were performed daily starting from 48 hours after VA-ECMO institution. A stepwise decrease of VA-ECMO blood flow was applied, until reaching 1 or 1.5 L/min. Successful weaning was defined as removal of VA-ECMO with no requirement for further MCS in the following 30 days. Results 76 patients were enrolled (23.8% female, 54.2±10.6 years-old), 52.6% due to CA. Median duration of VA-ECMO was 58 hours; 47 (61.8%) had intra-aortic balloon pump (IABP) inserted upfront. In-hospital mortality was 62.4% overall, 40% for CS without CA. 6 of the 32 weaned patients died in hospital for multiorgan failure due to septic shock. The baseline echocardiographic parameters associated with successful weaning were (Figure 1-A): stroke volume (SV) >13.2 ml (HR 4.12 [1.71-9.95], p 0.002), tIVT >23.6 min/sec (HR 0.14 [0.02-1.03], p 0.053), LV VTI >6.6 cm (HR 4.99 [1.94-12.87], p<0.001), MAPSE >6.15 mm (HR 4.42 [1.90-10.24], p 0.001), TAPSE >11 mm (HR 10.13 [1.37-7.02], p 0.023), RV S’ >7 cm (HR 5.40 [1.45-20.12], p 0.012). LVEF, E/e’ and S’ at mitral valve did not reach the statistical significance. Figure 1-B shows Kaplan-Meier analysis on echocardiographic indices collected during the last weaning trial; figure 2 details HR of all these parameters. Conclusions Echocardiography is pivotal in defining cardiac recovery and monitoring the weaning trial. Indices reflecting ventricular performance and delivered flow from LV were associated with weaning success both at VA-ECMO institution and throughout the weaning trials. Parameters reflecting ventricular activation and systo-diastolic interaction already demonstrated superiority in defining ventricular performance. Considering the known limitations of LVEF (HR, loading and LV dyssynchrony dependence), tIVT and MAPSE should be introduced in the standard evaluation in the acute setting.

Change in left ventricular velocity time integral during Trendelenburg maneuver predicts fluid responsiveness in cardiac surgical patients in the operating room.

Fluid responsiveness is an important topic for clinicians. We investigated whether changes in left ventricular outflow tract (LVOT) velocity time integral (VTI) during a Trendelenburg position (TP) maneuver can predict fluid responsiveness as a non-invasive marker in coronary artery bypass graft (CABG) surgery patients in the operating room. This prospective, single-center observational study, performed in the operating room, enrolled 65 elective CABG patients. Hemodynamic data coupled with transesophageal echocardiography monitoring of the LVOT VTI and the peak velocity were collected at each step [baseline 1, TP, baseline 2 and fluid challenge (FC)]. Patients whose VTI increased ≥15% after FC (500 mL of Gelofusine infusion within 30 min) were considered responders. Twenty-eight (43.1%) patients were responders to fluid administration. VTI changes during the TP maneuver predicted fluid responsiveness with an area under the receiver operating characteristic curve (AUC) of 0.90 (95% CI, 0.79-0.96), with a sensitivity of 100%, and a specificity of 70% at a threshold of 10% (gray zone, 8-15%). The increase in VTI during the TP was correlated with the VTI changes induced by FC (r=0.61, P<0.0001). Changes in peak velocity and pulse pressure during the TP were poorly predictive of fluid responsiveness, with an AUC of 0.72 (95% CI: 0.60-0.82) and 0.66 (95% CI: 0.53-0.77), respectively. An increase in VTI induced by the TP could predict fluid responsiveness in CABG patients in the operating room. However, changes in peak velocity and pulse pressure stimulated by the TP could not reliably predict fluid responsiveness.

A novel method of calculating stroke volume using point-of-care echocardiography

BackgroundPoint-of-care transthoracic echocardiography (POC-TTE) is essential in shock management, allowing for stroke volume (SV) and cardiac output (CO) estimation using left ventricular outflow tract diameter (LVOTD) and left ventricular velocity time integral (VTI). Since LVOTD is difficult to obtain and error-prone, the body surface area (BSA) or a modified BSA (mBSA) is sometimes used as a surrogate (LVOTDBSA, LVOTDmBSA). Currently, no models of LVOTD based on patient characteristics exist nor have BSA-based alternatives been validated.MethodsFocused rapid echocardiographic evaluations (FREEs) performed in intensive care unit patients over a 3-year period were reviewed. The age, sex, height, and weight were recorded. Human expert measurement of LVOTD (LVOTDHEM) was performed. An epsilon-support vector regression was used to derive a computer model of the predicted LVOTD (LVOTDCM). Training, testing, and validation were completed. Pearson coefficient and Bland-Altman were used to assess correlation and agreement.ResultsTwo hundred eighty-seven TTEs with ideal images of the LVOT were identified. LVOTDCM was the best method of SV measurement, with a correlation of 0.87. LVOTDmBSA and LVOTDBSA had correlations of 0.71 and 0.49 respectively. Root mean square error for LVOTDCM, LVOTDmBSA, and LVOTDBSA respectively were 13.3, 37.0, and 26.4. Bland-Altman for LVOTDCM demonstrated a bias of 5.2. LVOTDCM model was used in a separate validation set of 116 ideal images yielding a linear correlation of 0.83 between SVHEM and SVCM. Bland Altman analysis for SVCM had a bias of 2.3 with limits of agreement (LOAs) of − 24 and 29, a percent error (PE) of 34% and a root mean square error (RMSE) of 13.9.ConclusionsA computer model may allow for SV and CO measurement when the LVOTD cannot be assessed. Further study is needed to assess the accuracy of the model in various patient populations and in comparison to the gold standard pulmonary artery catheter. The LVOTDCM is more accurate with less error compared to BSA-based methods, however there is still a percentage error of 33%. BSA should not be used as a surrogate measure of LVOTD. Once validated and improved this model may improve feasibility and allow hemodynamic monitoring via POC-TTE once it is validated.

Ultrasound assessment of volume responsiveness in critically ill surgical patients: Two measurements are better than one.

The intended physiologic response to a fluid bolus is an increase in stroke volume (SV). Several ultrasound (US) measures have been shown to be predictive. The best measure(s) in critically ill surgical patients remains unclear. This is a prospective observational study in critically ill surgical patients receiving a bolus of crystalloid, colloid or blood. A transthoracic echocardiogram was performed before (pre-transthoracic echocardiogram) and after. A positive volume response (+VR) was defined as a ≥15% increase in SV. Predictive measures were: left ventricular velocity time integral (VTI), respiratory SV variation (rSVV), passive leg raise SVV (plr SVV), positional internal jugular (IJ) vein change (0-90 degrees) and respiratory variation in the IJ sitting upright (90 degrees IJ). For each measure the area under the receiver operating curve (AUROC) was assessed and the best measure(s) determined. Between November 2013 and November 2015, 199 patients completed the study. After the pilot analyses, plr SVV was abandoned because it could not be reliably assessed. VTI, rv 90 degrees IJ, 0 degree to 90 degrees IJ, were all significantly associated with VR (p < 0.05), rSVV and rv inferior vena cava were not. For VTI AUROC was 0.71 (95% confidence interval [CI], 0.64-0.77). For rv 90 degrees, it was 0.65 (95% CI, 0.57-0.71), and 0.61 (95% CI, 0.54-0.69) for 0 degrees to 90 degrees IJ. When VTI and rv 90 degrees were considered together, the AUROC rose to 0.76 (95% CI, 0.69-0.82) for the population as a whole and 0.78 (95% CI, 0.69-0.85) in mechanically ventilated patients. The positive predictive value for combined assessment was 80% and the negative 70%. In a clinically relevant heterogeneous population, US is moderately predictive of VR. Inferior vena cava diameter change is not predictive. IJ change and VTI are the best measures, especially when used together. Future work should focus on combination metrics and the IJ. Diagnostic test, level II.

Pre-ejection period by radial artery tonometry supplements echo doppler findings during biventricular pacemaker optimization

BackgroundBiventricular (Biv) pacemaker echo optimization has been shown to improve cardiac output however is not routinely used due to its complexity. We investigated the role of a simple method involving computerized pre-ejection time (PEP) assessment by radial artery tonometry in guiding Biv pacemaker optimization.MethodsBlinded echo and radial artery tonometry were performed simultaneously in 37 patients, age 69.1 ± 12.8 years, left ventricular (LV) ejection fraction (EF) 33 ± 10%, during Biv pacemaker optimization. Effect of optimization on echo derived velocity time integral (VTI), ejection time (ET), myocardial performance index (MPI), radial artery tonometry derived PEP and echo-radial artery tonometry derived PEP/VTI and PEP/ET indices was evaluated.ResultsSignificant improvement post optimization was achieved in LV ET (286.9 ± 37.3 to 299 ± 34.6 ms, p < 0.001), LV VTI (15.9 ± 4.8 cm to 18.4 ± 5.1 cm, p < 0.001) and MPI (0.57 ± 0.2 to 0.45 ± 0.13, p < 0.001) and in PEP (246.7 ± 36.1 ms to 234.7 ± 35.5 ms, p = 0.003), PEP/ET (0.88 ± 0.21 to 0.79 ± 0.17, p < 0.001), and PEP/VTI (17.3 ± 7 to 13.78 ± 4.7, p < 0.001). The correlation between comprehensive echo Doppler and radial artery tonometry-PEP guided optimal atrioventricular delay (AVD) and optimal interventricular delay (VVD) was 0.75 (p < 0.001) and 0.69 (p < 0.001) respectively. In 29 patients with follow up assessment, New York Heart Association (NYHA) class reduced from 2.5 ± 0.8 to 2.0 ± 0.9 (p = 0.004) at 1.8 ± 1.4 months.ConclusionAn acute shortening of PEP by radial artery tonometry occurs post Biv pacemaker optimization and correlates with improvement in hemodynamics by echo Doppler and may provide a cost-efficient approach to assist with Biv pacemaker echo optimization.

Intramural Dyssynchrony from Acute Right Ventricular Apical Pacing in Human Subjects with Normal Left Ventricular Function

Ventricular pacing causes early myocardial shortening at the pacing site and pre-stretch at the opposing ventricular wall. This contraction pattern is energetically inefficient and may lead to decreased cardiac function. This study was designed to describe the acute effects of right ventricular apical (RV(a)) pacing on dyssynchrony and systolic function in human subjects with normal left ventricular (LV) function and compare these effects to pacing from alternate ventricular sites. Patients (n = 26) undergoing an electrophysiology evaluation were studied during atrial pacing (AAI) and dual chamber pacing from the RV(a), left ventricular free wall (LV(fw)), and the combination of RV(a) and LV(fw) (BiV). Tissue Doppler imaging was used to measure intramural dyssynchrony by utilizing an integrated cross-correlation synchrony index (CCSI) from the apical 4-chamber view. RV(a) and BiV pacing significantly reduced systolic function as measured by longitudinal systolic contraction amplitude (SCA(long)) (p < 0.05) and LV velocity time integral (VTI) (p < 0.05) compared to AAI and LV(fw) pacing. RV(a) (and to a lesser extent BiV) pacing resulted in septal and lateral intramural dyssynchrony as indicated by significantly (p < 0.05) lower CCSI values as compared to AAI. CCSI was significantly (p < 0.05) worse during RV(a) than LV(fw) pacing. In patients with normal LV function, acute ventricular pacing in the RV(a) alone, or in conjunction with LV(fw) pacing (BiV), results in impaired regional and global LV systolic function and intramural dyssynchrony as compared to LV(fw) pacing alone.

Correlation of Echo-Doppler Optimization of Atrioventricular Delay in Cardiac Resynchronization Therapy With Invasive Hemodynamics in Patients With Heart Failure Secondary to Ischemic or Idiopathic Dilated Cardiomyopathy

This study investigated the optimal echocardiographic indexes to determine the most hemodynamically appropriate atrioventricular (AV) delay in cardiac resynchronization therapy (CRT) for heart failure. Doppler echocardiographic optimization of AV delay in CRT has not been correlated with invasive hemodynamic indexes. In 30 patients who underwent CRT, invasive left ventricular (LV) pressure measurements with a sensor-tipped pressure guidewire and Doppler echocardiographic examination were performed <24 hours after pacemaker implantation. Invasively, the optimal sensed AV delay was determined by LV dP/dt(max). The Doppler echocardiographic methods evaluated were the velocity-time integral (VTI) of the transmitral flow (EA VTI), diastolic filling time (EA duration), the VTI of the LV outflow tract or aorta (LV VTI), and Ritter's formula. Biventricular pacing with optimized interventricular and AV delay increased LV dP/dt(max) from 777 +/- 149 to 1,010 +/- 163 dynes/s (p<0.0001). The optimal AV delay with the EA VTI method was concordant with LV dP/dt(max) in 29 of 30 patients (r = 0.96), with EA duration in 20 of 30 patients (r= 0.83), with LV VTI in 13 patients (r = 0.54), and with Ritter's formula in none of the patients (r = 0.35). In conclusion, to obtain the optimal acute hemodynamic benefit of CRT, Doppler echocardiography is a reliable tool to optimize the AV delay compared with the invasive LV dP/dt(max). The measurement of the maximal VTI of mitral inflow is the most accurate method.

Temporal effects of an infusion of dobutamine hydrochloride in horses anesthetized with halothane

Abstract Objective To evaluate temporal hemodynamic effects of dobutamine in horses anesthetized with halothane. Animals 8 adult Thoroughbreds. Procedure Anesthesia was induced by IV administration of romifidine and ketamine and maintained using halothane in oxygen. After 60 minutes, dobutamine was administered IV for 60 minutes at 4 μg/kg of body weight/min. Measurements of left ventricular function were obtained by transesophageal echocardiography and cardiac catheterization. Results Mean, systolic, diastolic, aortic, pulmonary arterial, and left and right ventricular end-diastolic and systolic pressures, maximal rate of increase of intraventricular pressure (LVdp/dtmax), maximum acceleration (dv/dtmax) and velocity (Vmax) of aortic blood flow, cardiac output, and left ventricular velocity time integral were significantly increased, whereas left ventricular pre-ejection period and ejection time significantly decreased. Cardiac output, LVdp/dtmax, Vmax, and dv/dtmax increased throughout infusion. Heart rate was significantly less after 10 minutes and significantly greater at 60 minutes than before infusion. Supraventricular tachycardia developed in 2 horses. Cardiac output, LVdp/dtmax, Vmax, dv/dtmax, left ventricular and aortic systolic pressures, and mean aortic pressure had not returned to control values 30 minutes after infusion was discontinued. Conclusions At this dosage, dobutamine did not achieve peak effect on many hemodynamic variables within 40 minutes of commencing infusion, and effects of 60-minute infusion persisted after infusion was discontinued. Clinical Relevance Dobutamine has a hemodynamic profile suited to treatment of low cardiac output in anesthetized horses; however, sustained administration may be associated with supraventricular tachycardia and a protracted time to peak effect. (Am J Vet Res 1998;59:1027–1032)

Haemodynamic effects of a sixty minute infusion of dopamine hydrochloride in horses anaesthetised with halothane.

To describe the haemodynamic effects of a 60 min infusion of dopamine 4 microg/kg bwt/min during halothane anaesthesia, 7 mature Thoroughbred horses were studied. The infusion began 1 h after induction of anaesthesia by romifidine (100 microg/kg) and ketamine (2.2 mg/kg bwt). Throughout the period of dopamine infusion and for 30 min after its discontinuation, the horses were ventilated by intermittent positive pressure to maintain PaCO2 between 4.6-5.4 KPa. Inspired halothane concentration was adjusted to maintain an end tidal halothane concentration of 0.9%. Haemodynamic variables were measured using intracardiac strain gauge transducers sited in the left and right ventricle, aorta, and pulmonary artery. Left ventricular pressure was differentiated to obtain maximal rate of increase of intraventricular pressure (LVdp/dtmax). Transoesophageal Doppler echocardiography was performed to measure maximum aortic blood flow velocity (vmax) and acceleration (dv/dtmax), left ventricular velocity time integral (vTI) and cardiac output (CO), and left ventricular pre-ejection period (PEP) and ejection time (ET). Measurements were made during the 60 min infusion, and for 30 min after the infusion was discontinued. Infusion of dopamine 4 microg/kg/min significantly decreased mean aortic pressure, while left and right ventricular end-diastolic pressure and mean pulmonary artery pressure remained unchanged. There was a small, but significant, increase in heart rate during dopamine infusion. Maximum acceleration of aortic blood flow, CO and vTI were also significantly increased by dopamine infusion. Maximal rate of increase of intraventricular pressure (LVdp/dtmax) was significantly decreased 10 min after commencing infusion, but then returned to baseline for the remainder of the study. Left ventricular pre-ejection period (PEP) decreased during dopamine infusion whilst ejection time (ET) significantly increased. All measured variables except LVET had returned to baseline values within 30 min of discontinuing the infusion. This study demonstrated beneficial effects of dopamine infusion upon left ventricular systolic function. However, the therapeutic value of the drug is likely to be limited in clinical anaesthesia due to the simultaneous falls in arterial blood pressure which accompany its administration.