Fick Cardiac Output Research Articles

Comparison between invasive cardiac output and left ventricular assist device flow parameter.

Evaluate the correlation between left ventricular assist device flow parameter and invasive cardiac output measurements. We retrospectively evaluated right heart catheterization examinations performed in left ventricular assist device patients from 2 tertiary medical centers. We evaluated the correlation between cardiac output measurement methods (indirect Fick and thermodilution) and pump flow parameter using linear regression, agreement was graphically displayed using Bland-Altman plot technique. Clinical, echocardiographic, pump and haemodynamic parameters were compared between patients with and without discordance, defined as at least 20% difference between measurements. The study population consisted of 102 patients (median age 58 [51-64], 86% males, 17 ± 12 months post left ventricular assist device implantation) with a total of 544 measurement compared. Discordance between measurements were present in 102 of 226 (45%) comparisons between indirect Fick and pump flow and in 72 of 161 (48%) between thermodilution and pump flow. A comparison of indirect Fick and left ventricular assist device exhibited a statistical correlation of R = 0.751, and that of thermodilution and left ventricular assist device of R = 0.789. Parameters associated with the presence of discordance between cardiac output measurements included a higher rate of aortic valve opening, lower indirect Fick and higher thermodilution cardiac output. After excluding the lowest tertile of indirect Fick cardiac output values, the correlation between measurements improved (thermodilution: R = 0.879 and indirect Fick: R = 0.843, p < 0.001). The current left ventricular assist device flow parameter provides an estimation of cardiac output that correlates well with indirect Fick and exhibits the strongest correlation with thermodilution. This correlation was stronger after excluding lower cardiac output values.

Abstract 17833: Characterization of Central versus Peripheral Predominance of Exercise Limitation in Patients With Heart Failure and Preserved Ejection Fraction

Background: Heart failure with preserved ejection fraction (HFpEF) is a heterogenous disorder in which abnormalities in both cardiac output (CO) and peripheral oxygen extraction (CavO 2 ) contribute to impaired oxygen uptake (VO 2 ). We investigated the predominant limitation to VO 2 , according to distinct HFpEF criteria, by examining the CO vs. VO 2 relationship during incremental exercise. Methods: Participants underwent Cardiopulmonary Exercise Testing (CPET) with invasive hemodynamic assessment and were diagnosed with HFpEF based on characteristic symptoms and NTproBNP ≥125pg/mL, Supine PCWP ≥15mmHg, PCWP/CO ≥2mmHg/L/min or Peak PCWP ≥25mmHg. Calculated direct Fick CO versus VO 2 slope and peak exercise data were stratified by the expected relationship of CO(L/min) = 5хVO 2 (L/min) +5. The Mann Whitney U Test and t-test characterized those limited by cardiac output (Slope &lt;5L/min) vs. peripheral extraction (Slope &gt;5L/min). Results: In 425 dyspneic individuals meeting biomarker and/or hemodynamic criteria for HFpEF, 36% had predominantly peripheral limitation (Measured Peak CO &gt; Expected). Among those with NTpro-BNP ≥125pg/mL or resting PCWP ≥15mmHg, or both (N=220) , 31% were peripherally limited. 41% of those with a PCWP/CO ≥2mmHg/mL/min or Peak PCWP ≥25mmHg, or both (N=205) , were peripherally limited. Among all peripherally limited patients (N=151), the percentage of females, NTpro-BNP levels, Hb levels, rest and peak Ca-vO 2 , and rest and peak PVR were significantly lower compared to the cardiac limited group (Table, N=274), while resting PCWP, LVEF and HR were similar (Table). Conclusion: Despite meeting concurrent biomarker and/or hemodynamic criteria for HFpEF, peripheral-predominant limitation to exercise capacity is common which merits consideration when deploying interventions to augment exercise capacity in HFpEF.

Abstract 14195: Right Ventricular Outflow Tract Diameter Increase With the Low-Moderate Workload: A Prospective Simultaneous Exercise Echocardiography and Invasive Cardiopulmonary Exercise Testing Study

Background: While cardiac output at rest can be estimated non-invasively with echocardiogram, change in left ventricular or right ventricular outflow tract diameter (RVOTd) with exercise makes the cardiac output estimation inaccurate. Hypothesis: RVOTd increases with exercise proportionally with an incremental workload and is determined by stroke volume augmentation. Aims: 1. Define a workload-based change in RVOTd in subjects undergoing invasive cardiopulmonary exercise test (iCPET). 2. Correlate RVOTd at exercise stages with iCPET metrics. Methods: 20 subjects undergoing simultaneous echocardiogram and iCPET were enrolled in a prospective study. Exercise datapoints were acquired at 25 W (n=20), 50W (n=16), 75W (n=14), 100W (n=6). Three hemodynamic groups included: HFpEF (n=12), PAH (n=5), controls (n=3). Utilizing iCPET-based direct Fick cardiac output and stroke volume, RVOTd was reverse engineered with RVOT velocity time integral, per ASE guidelines. Pearson correlation was used to assess correlation of RVOTd with hemodynamic metrics. p&lt;0.05* Results: In overall cohort, age was 64±12 years, BMI 31.2±4.9 Kg/m 2 , female 60%, peak VO 2 13.7±5.7 mL/Kg.min -1 and V E /VCO 2 37±8. Increase in RVOTd with exercise is represented in the Figure. In comparison to rest, RVOTd increased significantly even at low-25W (+4.1±13.6%*) and moderate-50W (+7.6±17.2%*) workloads. Overall, RVOTd increased by 4-5% every 25W. At high workload (100W), the diameter increased by 24% (n=6). There were no differences in RVOT diameter between subgroups. RVOTd at four exercise stages (25W, 50W, 75W, 100W) correlated significantly with stroke volume index (r=0.68*, 0.80*, 0.23, 0.64) and cardiac output (r=0.50*, 0.80*, 0.08, 0.68), but non-significantly with heart rate (r=-0.15, 0.19, -0.10, 0.68). Conclusion: RVOTd increases by 4-5% every 25W on an incremental workload protocol. This behavior is predominantly associated with an increase in stroke volume index with exercise.

Cardiopulmonary Performance Among Heart Failure Patients Before and After Left Ventricular Assist Device Implantation

BackgroundPatients with heart failure with reduced ejection fraction (HFrEF) have persistent impairments in functional capacity after continuous-flow left ventricular assist device (CF-LVAD) implantation. ObjectivesThis study aims to characterize longitudinal changes in exercise hemodynamics and functional capacity among patients with HFrEF before and after CF-LVAD implantation. MethodsTen patients underwent 3 invasive cardiopulmonary exercise tests on upright cycle ergometry with pulmonary artery catheterization: 1) Visit 1 before CF-LVAD implantation; 2) Visit 2 after device implantation with CF-LVAD pump speed held constant at baseline speed; and 3) Visit 3 with increases in pump speed during exercise (median: 1,050 rpm [IQR: 750-1,150 rpm] and 220 rpm [IQR: 120-220 rpm] for HeartMate 3 and HeartWare VAD, respectively). Hemodynamics and direct Fick cardiac output were monitored using pulmonary artery catheterization. Gas exchange metrics were determined using indirect calorimetry. ResultsMaximal oxygen uptake (Visits 1, 2, and 3: 10.8 ± 2.5 mL/kg/min, 10.7 ± 2.2 mL/kg/min, and 11.5 ± 1.7 mL/kg/min; P = 0.92) did not improve after device implantation. Mean pulmonary arterial and pulmonary capillary wedge pressures increased significantly during submaximal and peak exercise on preimplantation testing (P < 0.01 for rest vs peak exercise) and remained elevated, with minimal change on Visits 2 and 3 regardless of whether pump speed was fixed or increased. ConclusionsAmong patients with HFrEF, cardiovascular hemodynamics and exercise capacity were similar after CF-LVAD implantation, regardless of whether patients exercised at fixed or adjusted pump speeds during exercise. Further research is needed to determine methods by which LVADs may alleviate the HFrEF syndrome after device implantation. (Effect of mechanIcal circulatoRy support ON exercise capacity aMong pAtieNts with heart failure [IRONMAN]; NCT03078972)

Exertional Cardiac and Pulmonary Vascular Hemodynamics in Patients With Heart Failure With Reduced Ejection Fraction

BackgroundExertional dyspnea is a cardinal manifestation of heart failure with reduced ejection fraction (HFrEF), but quantitative data regarding exertional hemodynamics are lacking. ObjectivesWe sought to characterize exertional cardiopulmonary hemodynamics in patients with HFrEF. MethodsWe studied 35 patients with HFrEF (59 ± 12 years old, 30 males) who completed invasive cardiopulmonary exercise testing. Data were collected at rest, at submaximal exercise and at peak effort on upright cycle ergometry. Cardiovascular and pulmonary vascular hemodynamics were recorded. Fick cardiac output (Qc) was determined. Hemodynamic predictors of peak oxygen uptake (VO2) were identified. ResultsLeft ventricular ejection fraction and cardiac index were 23% ± 8% and 2.9 ± 1.1 L/min/m2, respectively. Peak VO2 was 11.8 ± 3.3 mL/kg/min, and the ventilatory efficiency slope was 53 ± 13. Right atrial pressure increased from rest to peak exercise (4 ± 5 vs 7 ± 6 mmHg,). Mean pulmonary arterial pressure increased from rest to peak exercise (27 ± 13 vs 38 ± 14 mmHg). Pulmonary artery pulsatility index increased from rest to peak exercise, while pulmonary arterial capacitance and pulmonary vascular resistance declined. ConclusionsPatients with HFrEF suffer from marked increases in filling pressures during exercise. These findings provide new insight into cardiopulmonary abnormalities contributing to impairments in exercise capacity in this population. Clinical Trial Registrationclinicaltrials.gov identifier: NCT03078972

Cardiac output assessment methods in left ventricular assist device patients: A problem of heteroscedasticity

Equipoise remains about how best to measure cardiac output (CO) in patients with left ventricular assist devices (LVAD). In this study, direct Fick CO was compared with thermodilution (TD) and indirect Fick (iFick) CO in 61 LVAD patients. TD and LaFarge iFick showed moderate correlation with direct Fick (R2=0.49 and R2=0.38, p < 0.001 for both), while Dehmer and Bergstra iFick showed poor correlation with direct Fick (R2=0.29 and R2=0.31, p < 0.001 for both). Absolute bias between all CO estimation techniques and direct Fick CO was lowest for TD compared to iFick methods but significant for all methods. All methods tended to overestimate CO compared to direct Fick, with greatest overestimation present in those with the lowest measured direct Fick CO. Bias and frequency of significant discrepancy were least using TD and Lafarge iFick CO estimation methods in this study, with TD CO demonstrating modestly better correlation and less heteroscedasticity compared to Lafarge.

PO-672-06 SIMULTANEOUS HIS BUNDLE, LATERAL LV AND LATERAL RV PACING IN A PATIENT WITH REPAIRED TETRALOGY OF FALLOT

Patients with repaired Tetralogy of Fallot (ToF), who have RBBB and predominant right ventricular (RV) dysfunction may benefit from RV electromechanical resynchronization. We describe the case of a patient with repaired ToF, biventricular (BiV) dysfunction and ineffective cardiac resynchronization therapy (CRT) in whom His bundle pacing (HBP) fused with RV wall pacing achieved RV CRT and acute hemodynamic improvement. N/A 58 YOF with repaired ToF and BiV dysfunction presented with decompensated heart failure (HF). BiV implantable cardioverter-defibrillator (ICD) with RA, RV and coronary sinus (CS) leads (Biotronik, Berlin, Germany) was placed at an outside facility one year ago. Underlying EKG showed sinus rhythm with 1stdegree AVB (PR 240 ms), RBBB (QRSd 200ms) and left posterior fascicular block. With presenting CRT, QRS was wider (QRSd 240). Chest Xray revealed RV ICD lead in the right ventricular outflow tract (RVOT) and the CS lead in the anterior interventricular vein with the tip electrode also near RVOT. Given concern for suboptimal CRT, defibrillation vector and limited alternative options, we pursued individualized CRT optimization. Activation mapping showed latest RV activation in the basal lateral tricuspid annulus. Pacing from this site simultaneously with the His Bundle narrowed the QRS significantly and improved RVEF and dyssynchrony on intracardiac echocardiography. Fick cardiac output and index improved to 4.4 and 2.4 respectively from 3.7 and 2.0 at baseline. Thus, we removed the old CS lead and replaced the ICD lead with a new DF-1 defibrillator lead (Medtronic, Minneapolis, MN) in the RV apical septum. Then, we placed a SelectSecureTM His lead (3830 model, Medtronic, Minneapolis, MN). Non-selective His capture threshold was 1.0 V at 0.4 ms. Then, we placed a SelectSecureTM lead (3830 model, Medtronic, Minneapolis, MN) in the RV basal lateral wall and this was Y-adapted to a new LV lead (4196Y model, Medtronic, Minneapolis, MN) which was placed on a lateral branch of the CS. HBP fused with LV and RV lateral wall pacing resulted in a QRS of 120ms. At one year follow up, she has not had HF admissions. Simultaneous HBP and RV basal lateral wall pacing may be a feasible strategy for RV CRT in patients with ToF, RBBB and predominant RV dysfunction.

A Single Center Analysis Of Correlation Of Heartmate 3 Lvad Flows To Indirect Fick Method Derived By Swan-ganz Catheter

Background Heartmate 3 left ventricular assist device (LVAD) has been approved for end stage heart failure patients. The LVAD flows are calculated and are presumed to represent a surrogate for cardiac output (CO). We investigated if cardiac output measured by indirect fick method correlates with the LVAD flows in the peri-operative period to make clinical decisions. Methods This was a single center, retrospective analysis of patients post destination therapy LVAD implantation. LVAD flow (LF) derived from the LVAD was compared to the cardiac output calculated via indirect fick. Patients were also sub-categorized to opening of the aortic valve with use of echocardiogram. Additional data of each patients age, sex, height, weight,intermacs stage, pulmonary artery oxygenation saturation, peripheral arterial oxygenation,heart rate, hemoglobin and hematocrit were also reviewed. The LF, indirect fick CO measurements and opening of aortic valve were all measured within the first 72 hours post LVAD implant Results A total of 27 patients were used in the analysis of this study. The mean indirect fick calculated CO was 5.68 liters per minute (lpm) and the mean LVAD flow (LF) was 4.12lpm. Using Bland-Altman analysis, the fick derived CO systematically over-estimated cardiac output compared to the LVAD PF method (DeltaCO) by 1.56±1.11 L/min (95% CI 1.12 to 2.00,P < 0.001). The difference between the delta CO was not influenced by the flow from the aortic valve with P= 0.56 derived from the overall model. Additional sub-analysis of age, sex, height,weight, a low flow cardiac index of less than 2.2 L/min/m 2, low venous oxygenation, low hemoglobin values did not show statistical correlation of LVAD PF to indirect fick CO. Conclusion There was no significant correlation between the LVAD flow and an indirect fick CO in the first 72 hours post LVAD implant. LVAD flow should not be independently used to make relevant clinical decisions without hemodynamic guidance from swan-ganz catheter. Heartmate 3 left ventricular assist device (LVAD) has been approved for end stage heart failure patients. The LVAD flows are calculated and are presumed to represent a surrogate for cardiac output (CO). We investigated if cardiac output measured by indirect fick method correlates with the LVAD flows in the peri-operative period to make clinical decisions. This was a single center, retrospective analysis of patients post destination therapy LVAD implantation. LVAD flow (LF) derived from the LVAD was compared to the cardiac output calculated via indirect fick. Patients were also sub-categorized to opening of the aortic valve with use of echocardiogram. Additional data of each patients age, sex, height, weight,intermacs stage, pulmonary artery oxygenation saturation, peripheral arterial oxygenation,heart rate, hemoglobin and hematocrit were also reviewed. The LF, indirect fick CO measurements and opening of aortic valve were all measured within the first 72 hours post LVAD implant A total of 27 patients were used in the analysis of this study. The mean indirect fick calculated CO was 5.68 liters per minute (lpm) and the mean LVAD flow (LF) was 4.12lpm. Using Bland-Altman analysis, the fick derived CO systematically over-estimated cardiac output compared to the LVAD PF method (DeltaCO) by 1.56±1.11 L/min (95% CI 1.12 to 2.00,P < 0.001). The difference between the delta CO was not influenced by the flow from the aortic valve with P= 0.56 derived from the overall model. Additional sub-analysis of age, sex, height,weight, a low flow cardiac index of less than 2.2 L/min/m 2, low venous oxygenation, low hemoglobin values did not show statistical correlation of LVAD PF to indirect fick CO. There was no significant correlation between the LVAD flow and an indirect fick CO in the first 72 hours post LVAD implant. LVAD flow should not be independently used to make relevant clinical decisions without hemodynamic guidance from swan-ganz catheter.

Aortic Pulsatility Index, A New Hemodynamic Assessment, Predicts Cardiovascular Death At 1 Year.

<h3>Introduction</h3> Heart failure with reduced ejection fraction (HFrEF) remains one of the leading causes of cardiovascular death and morbidity. Identifying patients most at risk for death remains a key component in the decision making in implementing advanced therapies. In this study, we evaluate the aortic pulsatility index to risk stratify patients. <h3>Methods</h3> : A total of 79 consecutive patients with reduced systolic function undergoing right heart catherization for HFrEF were identified in 2019. Statistics were performed with clinical characteristics and continuous variables were expressed as means +/- standard deviations (STD) or medians with interquartile ranges and compared with either Student t tests or Mann-Whitney U (Wilcoxon) tests. <h3>Results</h3> : Seventy-nine patients were included in the final analysis. Aortic pulsatility index average +/- STD across all patients was 2.53 +/- 1.72. Cardiac power output (CPO) average +/- STD was 0.79 +/- 0.32. Ten patients had expired at 1 year and API was predictive of death at 1 year, p = 0.013 while CPO, Fick cardiac output (FCo), and thermodilution cardiac output (ThCo) did not, p = 0.52, 0.79, 0.073 respectively (Figure 1a). Fourteen patients required advanced therapies, defined as heart transplant, left ventricular assist device, or inotropic therapy. API, but not CPO, FCo, or ThCo was associated with need for advanced therapies or death at 1 year, p = 0.006 vs p = 0.92, 0.25, 0.34 respectively (Figure 1b). In deceased patients, average API was 1.44 +/- 0.3 vs 2.7 +/- 1.78 in surviving patients, p<<0.001 (Figure 1c). A receiver operating curve was plotted for API vs death, with area under the curve being 0.745, p = 0.013 (Figure 2). <h3>Conclusion</h3> : API provides discriminatory information over standard hemodynamic measurements including isolated measurements of right and left filling pressures, CPO, and FCo or ThCo for cardiovascular death or need for advanced therapies at 1 year. API can be used to aid decision making in identifying patients at highest risk for death in order to direct advanced therapies to these patients most in need.

Metabolic and Hemodynamic Determinants of Exercise with the HeartMate 3 LVAD

<h3>Purpose</h3> Several studies have reported that peak oxygen consumption (pVO2) is diminished after continuous flow (CF) LVAD support and recent data shows that pVO2 post LVAD predicts outcomes. It has been suggested that augmentation of native cardiac output (NCO) and not LVAD flow supports exercise. Using simultaneous metabolic and hemodynamic measures, we further studied the determinants of maximal exercise with the Heartmate 3 (HM3) LVAD. <h3>Methods</h3> Subjects underwent maximal upright bicycle exercise testing utilizing a 10-15 W ramp protocol with hemodynamic measurements from a right heart and radial arterial catheter, and CPET testing with a metabolic cart (Metalyzer 3B, Cortex, Germany). Mid-point hemodynamics were acquired to plot pressure/flow relationships. NCO was calculated by subtracting LVAD flow from Fick cardiac output (FCO). Arterial lactate and regional tissue oxygenation (rSO2) with the NIRS SenSmart™ were also measured. <h3>Results</h3> Six HM3 subjects (43-76 yrs) were studied at least 12 weeks post implant, all were on at least 2 neurohormonal agents. All patients performed maximal exercise (RER 1.10-1.34). Most did not demonstrate chronotropic incompetence; achieving median 80.8 (63.5- 90.9) % of predicted heart rate. We saw robust oxygen extraction, with median peak A-VO2 difference 14.2 (10.5-15.8) mL/100mL with no change in rSO2 and median peak lactate 6.5 (3.5-9.9) mmol/L. However, 5/6 subjects achieved pVO2 ≤14 ml/kg/min. During exercise, there was minimal augmentation of LVAD flow (0.4-1.6 L/min) while NCO increased by 2.0-7.1 L/min. Mean pulmonary artery (mPA)/FCO relationships were available for 5 subjects (Fig.1), demonstrating abnormal rate of rise of mPA in all patients (slope 3.7-7.0, normal < 3). <h3>Conclusion</h3> Neither chronotropic response nor peripheral extraction appeared to limit exercise. Steep rise in mPA suggests either impaired pulmonary vasoreactivity and or cardiac reserve may be the key determinants of exercise capacity during HM3 support. Further study will clarify these factors.

Correlation Between Venous Oxygen Saturations Obtained From Pulmonary Artery Catheter And Peripherally Inserted Central Catheter In Patients Receiving Inotrope Support

Correlation Between Venous Oxygen Saturations Obtained From Pulmonary Artery Catheter And Peripherally Inserted Central Catheter In Patients Receiving Inotrope Support

Exercise Blood Pressure in Heart Failure With Preserved and Reduced Ejection Fraction

ObjectivesThis study aimed to evaluate hemodynamic correlates of inducible blood pressure (BP) pulsatility with exercise in heart failure with preserved ejection fraction (HFpEF), to identify relationships to outcomes, and to compare this with heart failure with reduced ejection fraction (HFrEF). BackgroundIn HFpEF, determinants and consequences of exercise BP pulsatility are not well understood. MethodsWe measured exercise BP in 146 patients with HFpEF who underwent invasive cardiopulmonary exercise testing. Pulsatile BP was evaluated as proportionate pulse pressure (PrPP), the ratio of pulse pressure to systolic pressure. We measured pulmonary arterial catheter pressures, Fick cardiac output, respiratory gas exchange, and arterial stiffness. We correlated BP changes to central hemodynamics and cardiovascular outcome (nonelective cardiovascular hospitalization) and compared findings with 57 patients with HFrEF from the same referral population. ResultsIn HFpEF, only age (standardized beta = 0.593; P < 0.001), exercise stroke volume (standardized beta = 0.349; P < 0.001), and baseline arterial stiffness (standardized beta = 0.182; P = 0.02) were significant predictors of peak exercise PrPP in multivariable analysis (R = 0.661). In HFpEF, lower PrPP was associated with lower risk of cardiovascular events, despite adjustment for confounders (HR:0.53 for PrPP below median; 95% CI: 0.28-0.98; P = 0.043). In HFrEF, lower exercise PrPP was not associated with arterial stiffness but was associated with lower peak exercise stroke volume (P = 0.013) and higher risk of adverse cardiovascular outcomes (P = 0.004). ConclusionsIn HFpEF, greater inducible BP pulsatility measured using exercise PrPP reflects greater arterial stiffness and higher risk of adverse cardiovascular outcomes, in contrast to HFrEF where inducible exercise BP pulsatility relates to stroke volume reserve and favorable outcome.

Abstract 13282: Oxygen Uptake and Cardiac Output Exhibit Delayed Recovery After Maximum Incremental Ramp Exercise in Patients With Exercise Pulmonary Hypertension

Introduction: In individuals with dyspnea on exertion (DOE) and suspected exercise pulmonary hypertension (exPH), oxygen uptake (VO 2 ), cardiac output (CO), peripheral oxygen extraction (Ca-vO 2 ), and mean pulmonary artery pressure (mPAP) have been well characterized during incremental exercise but less is known about the kinetics of post-exercise recovery patterns. Hypothesis: Exercise recovery cardiac output kinetics are slowed in patients with exPH. Methods: Upright maximum incremental ramp cycle ergometry cardiopulmonary exercise testing with invasive hemodynamic monitoring and serial blood gas measurements during exercise and recovery was performed in 50 consecutive patients referred for evaluation of DOE of unclear etiology. VO 2 , arterial and venous oxygen content (Ca-vO 2 ), Fick cardiac output, and mPAP were analyzed from rest, peak exercise, and 2 minutes post-exercise. ExPH was defined in a consistent manner with recent consensus statements (ΔmPAP/ΔCO &gt;3.0 mmHg/L/min) from rest to peak exercise. Results: Among 50 patients with DOE, [62% female, Age 61.7±11.8, BMI 30.7±8.2] 2-min post-exercise VO 2 was -56±11%, CO: -22±19%, Ca-vO 2 :-42±15% compared to peak exercise values. The % fall in CO at 2min was significantly lower in the 26 patients with exPH compared to the 24 patients without exPH (Table). The average mPAP remained elevated at 2 min post-exercise (&gt;20mmHg) in exPH despite normal average resting values. Conclusions: Patients with exPH demonstrate slowed CO recovery kinetics in conjunction with persistent PAP elevation 2-min post-exercise. Persistent elevation in blood flow through the pulmonary circuit at a time conducive to non-invasive assessment of PAP (i.e. by echocardiography) may lend itself to non-invasive detection of exercise-PH in patients undergoing evaluation of dyspnea on exertion.

Body Habitus Considerations During Right Heart Catheterization

BackgroundObese and overweight body habitus are common among patients undergoing right heart catheterization for suspected pulmonary hypertension, but previous studies have described only patients with severe obesity. This study examined the effect of body habitus on intracardiac pressures, thermodilution cardiac output (TDCO), indirect Fick (iFick) cardiac output (CO), and pulmonary vascular resistance (PVR) in subjects with normal cardiopulmonary hemodynamics. MethodsA retrospective analysis was conducted on healthy volunteers and patients referred for right heart catheterization for dyspnea of unknown origin with normal hemodynamics. Of the 65 subjects (53 ± 14 years; 51% female), 31% were normal weight, 49% were overweight, and 20% had obesity, as defined by a body mass index of 30-39.9 kg/m2. Mixed venous oxygen saturations and intracardiac pressures were compared across body mass index categories. Agreement between iFick CO calculated by 3 formulae, and TDCO and PVR was examined. ResultsNo differences in intracardiac pressures were observed, but mixed venous oxygen saturations were lower in the obese group. iFick CO underestimated TDCO, particularly with the LaFarge formula, with a systematic difference of 0.33 L/min for every 1 L/min increase in CO. This difference was largest in the obese group—on average by 23% ± 10%, translating to an overestimation of PVR by 34% ± 16% on average. ConclusionsIn individuals without severe obesity, intracardiac pressures are not different, but mixed venous oxygen saturations are lower. Obesity confounds estimations of CO and PVR by iFick methods, which could result in inappropriate hemodynamic classification. These data can inform best practices in hemodynamic assessment of populations with obesity.

Estimated versus Actual Oxygen Consumption in Patients Supported with LVADs

PurposeAccurately measured cardiac output (CO) is critical to medical decision making in heart failure patients. The most recent OPTN listing criteria incorporate CO in determining allocation priority. CO is frequently calculated using the Fick equation, in which the key variable of oxygen consumption (VO2) can be directly measured, but is more commonly estimated. The accuracy of these VO2 estimations have been questioned in heart failure patients and have not been validated in LVAD patients. We sought to determine the comparative accuracy of estimated versus measured VO2 in a cohort of LVAD patients using three common formulae.MethodsData were prospectively collected in consecutive LVAD patients who underwent right heart catheterization with direct measurement of resting VO2 using an MGC Diagnostics Ultima CardiO2® gas-exchange analysis cart. We estimated VO2and Fick CO using the formulae proposed by Dehmer et al., LaFarge and Miettinen, and Bergstra et al., and compared these values with directly measured VO2, Fick CO, and thermodilution CO.ResultsFour male patients with HeartMate 3® LVADs underwent right heart catheterization with VO2 measurement. The mean differences in estimated versus measured VO2 and CO were smallest with the formulae proposed by Dehmer et al. and LaFarge and Miettinen, which both modestly underestimated directly measured CO (-0.2 ± 0.3). The error in calculated CO was substantial when utilizing the Bergstra et al. formula (0.5 ± 0.4) and the thermodilution method (-0.8 ± 0.2).ConclusionResting oxygen consumption in LVAD patients, as directly measured by gas-exchange analysis, can be estimated within an acceptable degree of error by the formulae proposed by Dehmer et al. and LaFarge and Miettinen. By comparison, the assumed VO2 by the Bergstra et al. formula appears less accurate in LVAD patients and the degree of error in calculated Fick CO using this equation may be unacceptable for clinical decision making. Accurately measured cardiac output (CO) is critical to medical decision making in heart failure patients. The most recent OPTN listing criteria incorporate CO in determining allocation priority. CO is frequently calculated using the Fick equation, in which the key variable of oxygen consumption (VO2) can be directly measured, but is more commonly estimated. The accuracy of these VO2 estimations have been questioned in heart failure patients and have not been validated in LVAD patients. We sought to determine the comparative accuracy of estimated versus measured VO2 in a cohort of LVAD patients using three common formulae. Data were prospectively collected in consecutive LVAD patients who underwent right heart catheterization with direct measurement of resting VO2 using an MGC Diagnostics Ultima CardiO2® gas-exchange analysis cart. We estimated VO2and Fick CO using the formulae proposed by Dehmer et al., LaFarge and Miettinen, and Bergstra et al., and compared these values with directly measured VO2, Fick CO, and thermodilution CO. Four male patients with HeartMate 3® LVADs underwent right heart catheterization with VO2 measurement. The mean differences in estimated versus measured VO2 and CO were smallest with the formulae proposed by Dehmer et al. and LaFarge and Miettinen, which both modestly underestimated directly measured CO (-0.2 ± 0.3). The error in calculated CO was substantial when utilizing the Bergstra et al. formula (0.5 ± 0.4) and the thermodilution method (-0.8 ± 0.2). Resting oxygen consumption in LVAD patients, as directly measured by gas-exchange analysis, can be estimated within an acceptable degree of error by the formulae proposed by Dehmer et al. and LaFarge and Miettinen. By comparison, the assumed VO2 by the Bergstra et al. formula appears less accurate in LVAD patients and the degree of error in calculated Fick CO using this equation may be unacceptable for clinical decision making.

Thermodilution vs indirect fick cardiac output measurement in clinical practice: insights from a tertiary centre

Abstract Introduction Thermodilution (TD) and indirect Fick (IF) methods are widely used to measure cardiac output (CO). They are often used interchangeably to make critical clinical decisions, yet few studies have compared these approaches concerning agreement and comparative prognostic value as applied in medical practice. Purpose To assess agreement between TD and IF methods and to compare how well these methods predict mortality. Methods Retrospective cohort study including all consecutive right heart catheterizations performed in a referral pulmonary hypertension (PH) centre from 2010 to 2018. Cardiac index (CI) was calculated by indexed CO to body surface area. PH was classified according to the new definition of the 6st World Symposium on Pulmonary Hypertension 2018 [mean pulmonary arterial pressure (mPAP) &amp;gt;20 mmHg]. Patients with cardiac or extra-cardiac shunts or significant (moderate to severe or severe) tricuspid regurgitation were excluded. All-cause mortality over 1 year after right heart catheterization was recorded. Logistic regression was used to identify predictors of the adverse event. Results From a total of 569 procedures, 424 fulfilled the inclusion criteria: mean age 56.7±15.4 years, 67.3% female. Haemodynamic parameters were diagnosed of PH in 86.2% of cases: mPAP 35.3±15.3 mmHg, 83.6% pre-capillary subtype, 42.9% belonging to group 4 (chronic thromboembolic pulmonary hypertension) and 26.6% to group 1 (pulmonary arterial hypertension). Mean values of CO and CI were, respectively, 4.5±2.8 L/min and 2.5±0.8 L/min/m2 measured by TD and 4.6±2.4 L/min and 2.6±1.3 L/min/m2 measured by IF method. There was a median difference (IF minus TD) of - 0.03 / min to CO and - 0.05 L/min/m2 to CI but both meausres correlated only modestly (r=0.6 to TD and r=0.5 to IF). One-year all-cause mortality rate was 5.4% (median time to death was 50.5 days). Lower values of CO and CI assessed by TD were significantly associated with all-cause mortality occurrence (CO TD: 4.5±1.3 L/min versus 3.6±1.0 L/min, p&amp;lt;0.01; CI TD: 2.6±0.7 L/min/m2 versus 2.1±0.4 L/min/m2, p&amp;lt;0.01). No association was observed between CO (p=0.31) and CI (p=0.42) measured by IF method and the adverse event. Logistic regression identified 2 independent predictors of all-cause mortality: TD CO (OR 0.55, 95% CI 0.38–0.79, p&amp;lt;0.01) and TD CI (OR 0.34, 95% CI 0.17–0.67, p&amp;lt;0.01). Similar results were obtained when patients diagnosed with PH were independently analyzed. Conclusions There is only modest agreement between TD and IF CO and CI estimates. Despite being more time-consuming, TD measurements were predictors of all-cause mortality and present a highest prognostic value. These findings favored their used over IF in clinical practice. Funding Acknowledgement Type of funding source: None

A Case of Suspected Covid 19 Related Cardiomyopathy

BackgroundThe novel SARS-CoV-2 virus causing COVID-19 has been associated with diverse cardiovascular pathology. We present a case of cardiomyopathy due to possible COVID-19 resulting in cardiogenic shock.CaseA 54 year-old male presented to the hospital with 4 weeks of progressive dyspnea, leg swelling, and weight gain. His symptoms began 4 weeks after experiencing influenza-like symptoms after a trip to China during the height of their COVID-19 outbreak. He was admitted to the COVID unit in cardiogenic shock and was later intubated for acute hypoxic respiratory failure. Laboratory data demonstrated acute kidney injury, elevated transaminases, lactic acidosis, elevated pro-BNP N-Terminal to 3932pg/mL, and high sensitivity troponin to 72ng/L. Transthoracic echocardiogram showed severe biventricular failure with a LVEF of 10% and a LVIDd 5.2cm. SARS-CoV-2 RNA was negative twice, but SARS-CoV-2 IgG AB and SARS-CoV-2 IgA AB were positive. Urgent right and left heart catheterization was performed demonstrating non-obstructive coronary artery disease and hemodynamics consistent with cardiogenic shock. While supported with an intra-aortic balloon pump (IABP) and norepinephrine, he had a fick cardiac output 3.1 L/min, fick cardiac index 1.6 L/min/m2, pulmonary capillary wedge pressure 37mmHg, right atrial pressure 25mmHg, and pulmonary arterial pressures 65/40mmHg. Given persistent cardiogenic shock on IABP and inotropes, he was later transitioned to Veno-Arterial Extracorporeal Membrane Oxygenation (VA ECMO) and an Impella CP for left ventricular unloading. He continued to have persistent INTERMACS I shock and underwent successful implantation of a HeartMate 3 LVAD with percutaneous temporary right ventricular assist device (RVAD). Pathology of the left ventricular apical core demonstrates polyclonal endocardial infiltration of B-Cells, CD4 and CD8 positive T-Cells, eosinophils, macrophages, and plump reactive endothelial cells (Figure 1). He is currently recovering in the ICU off of vasoactive support with subsequent removal of percutaneous RVAD.ConclusionThis is a suspected case of COVID-19 associated cardiomyopathy presenting as new on-set heart failure with reduced ejection fraction complicated by cardiogenic shock. There is still much to learn about the cardiac manifestations of COVID-19 and further studies are needed to determine appropriate diagnostics and management of such cases.

Fick principle and exercise pulmonary hemodynamic determinants of the six-minute walk distance in pulmonary hypertension.

The six-minute walk test is widely used to assess the severity and prognosis of pulmonary hypertension. However, the pathophysiology underlying a compromised six-minute walk distance is incompletely characterized. The purpose of this study is to evaluate the Fick principle and pulmonary hemodynamic determinants of the six-minute walk distance in patients with suspected pulmonary hypertension. Twenty-nine patients were retrospectively studied and underwent a right heart catheterization for the evaluation of suspected pulmonary hypertension. With the pulmonary artery catheter in place, patients were moved to a treadmill and completed a six-minute walk test. Fick cardiac output and indices of right heart afterload were calculated using continuous measurements of pulmonary vascular pressures, gas exchange, and mixed venous blood samples. Fifteen subjects who walked ≤ 348 m were compared to 14 subjects who walked > 348 m. Systemic oxygen delivery was impaired in six-minute walk distance ≤ 348 m compared to six-minute walk distance > 348 m (15.2 ± 6.2 vs. 23.2 ± 6.8 mL/kg/min, p < 0.01). Impaired oxygen delivery was due to a depressed cardiac index and decreased cardiac reserve demonstrated by the change in the stroke volume index (3.0 ± 14 vs. 17 ± 15 mL/min/m2, p = 0.02). The six-minute walk distance positively correlated with oxygen delivery (r = 0.501, p = 0.006) and inversely correlated with oxygen extraction (r = 0.369, p = 0.049). A decreased six-minute walk distance was associated with an increased total pulmonary resistance (r = 0.502, p = 0.006) and pulmonary vascular resistance (r = 0.530, p = 0.003). In patients with suspected pulmonary hypertension, a decreased six-minute walk distance is due to compromised oxygen delivery, decreased cardiac reserve, and increased right ventricular afterload.

A Pilot Study Comparing Aortic Valve Area Estimates Derived from Fick Cardiac Output with Estimates Based on Cheetah-NICOM Cardiac Output

Cardiac output during cardiac catheterization is often estimated using the modified Fick method (COFick). In this proof-of-concept, prospective non-randomized study carried out in a single academic healthcare centre, we examined whether replacing COFick in the Gorlin formula with Cheetah-NICOM monitor cardiac output (COCheetah) could produce an accurate and precise estimate of aortic valve area in patients with severe aortic stenosis. In twenty-six subjects, COFick and COCheetah were obtained concurrently. A spot and 3-minute running average of COCheetah was used. Bland and Altman analysis was used to derive bias, 95% limits of agreement (LOA) and confidence intervals (CI). The mean difference (bias) between AVACheetah (average) and AVAFick was 0.11 cm2 and the 95% LOA were ±0.42 cm2. The 95% CI of the bias was 0.02–0.2 cm2. The bias and 95% LOA of AVACheetah (spot value) were 0.14 ± 0.42cm2, with a 95% CI of 0.06–0.23 cm2. No proportional bias was present. AVACheetah thus appears to be a reasonably accurate measure of AVA in patients with severe aortic stenosis compared to AVAFick measured using a modified Fick CO. However, the limits of agreement were not narrow enough to consider AVACheetah and AVAFick interchangeable.

Hemodynamic Response to Exercise in Patients Supported by Continuous Flow Left Ventricular Assist Devices

ObjectivesThis study sought to characterize the hemodynamic response to exercise in LVAD-supported patients and identify parameters most strongly associated with peak oxygen consumption (VO2). BackgroundDespite improved survival for heart failure patients afforded by continuous flow left ventricular assist devices (LVADs), peak exercise capacity remains impaired. Mechanisms underlying this reduced functional capacity remain poorly understood. MethodsPatients referred for post-VAD hemodynamic optimization from December 2017 through June 2019 were enrolled. Swan Ganz catheters were inserted and upright incremental bicycle ergometry with respiratory gas analysis was performed. Hemodynamic measurements, mixed venous saturation, and arterial blood pressure were recorded every 3 min during exercise. Linear correlations were performed between peak VO2 (ml/min) and peak Fick cardiac output (CO), peak device flow, the assumed intrinsic CO derived as Fick CO-device flow, peak pressure differential across the LVAD (mean arterial pressure−pulmonary capillary wedge pressure), peak pressure differential across right ventricle (mean pulmonary artery pressure − right atrial pressure) and systemic vascular resistance. ResultsForty-five patients supported by axial flow pumps (n = 12) and centrifugal flow pumps (n = 33) were studied. There were 34 men and 11 women. Age averaged 60 ± 10 years. Peak VO2 averaged 10.6 ± 3.1 ml/kg/min. Fick CO had the greatest correlation with peak VO2 with r = 0.73 (p < 0.0001) followed by intrinsic CO (r = 0.67; p < 0.0001). Multivariate model that best predicted peak VO2 included Fick CO and peak arterial venous oxygen (AVO2) difference. ConclusionsLVAD supported patients have severely impaired peak exercise capacity. The peak Fick cardiac output was the best correlate of peak exercise performance.