Chaliki, Kalyan

Background/Objectives: The peak oxygen consumption (VO2) during cardiopulmonary exercise testing (CPET) is a strong predictor of all-cause mortality. The cardiac output, a key determinant of VO2, can be assessed using resting echocardiographic parameters. The heart rate recovery and ventilatory efficiency (VE/VCO2 slope) from CPET offer additional insights into cardiovascular fitness. Methods: This study aimed to identify resting echocardiographic parameters that predict the percentage of predicted peak VO2, heart rate recovery, and VE/VCO2 slope in a general cardiology population. This retrospective analysis included 1909 patients who underwent echocardiography within 3 months of CPET from 2017 to 2022. Patients with potentially confounding co-morbid conditions were removed. Spearman correlations were used to compare 19 echocardiographic parameters to peak VO2, heart rate recovery, and the VE/VCO2 slope, followed by multiple linear regression of peak VO2. Results: Eleven echocardiographic parameters correlated with peak VO2, with the strongest correlations seen with the left ventricular stroke volume index (R = 0.284, p < 0.001), mitral valve medial annular a’ wave velocity (R = 0.142, p < 0.0001), and mitral E-to-e’ ratio (R = −0.117, p < 0.0001). The left ventricular diastolic parameters and mitral E/A ratio correlated strongly with the heart rate recovery and VE/VCO2 slope. The multiple linear regression analysis identified the left ventricular mass index, stroke volume index, mitral valve E wave velocity, tricuspid valve regurgitation peak systolic velocity, tricuspid lateral annular systolic velocity S’, and left atrial volume index as independent predictors of peak VO2 (R2 = 0.191). Conclusions: The left ventricular stroke volume, diastolic function, and RV systolic function markers are significant predictors of cardiopulmonary fitness, aiding clinical decision-making in patients without CPET data.

Background: Cardiopulmonary Exercise Testing (CPET) analyzes physiologic information with gas exchange during exercise. Peak oxygen volume consumption (absolute peak VO2 and percent predicted peak VO2), minute ventilation divided by carbon dioxide volume (VE/VCO2 slope) and heart rate reduction after 1 minute of recovery (heart rate recovery, HRR) all have well-established prognostic cardiovascular implications. Aim: Given the wider use of echocardiography, we aimed to see if important CPET data could be determined from resting transthoracic echocardiography (TTE). Methods: In this retrospective study, cardiology patients above 18 years who underwent both resting TTE and a max-effort CPET within 3 months of each other (2017-2022) were included. Patients with a history of coronary artery bypass grafting, valve surgery, pacemakers, congenital heart disease, severe valve dysfunction and pulmonary hypertension were excluded before analysis. Univariate analysis with Spearman correlations was used to assess the relationship between 4 CPET measurements {absolute peak VO2 per kg, percent predicted peak VO2/kg (adjusted for age, sex and body surface area), HRR, and VE/VCO2}; and 22 quantitative TTE parameters. Bonferroni correction was applied within each set of correlations, with significance set at p-values <0.025. Multivariate linear regression models were built for all the related TTE measurements to assess relationship with the 4 CPET parameters, adjusting for age and sex. Results: Table 1 shows, out of 1909 patients analyzed, our regression model is strongest for absolute peak VO2/kg (R-squared=0.57), with 3 significantly associated TTE parameters. For percent-predicted peak VO2 per kg, 4 TTE variables were significantly associated. For heart rate recovery, only LV stroke-volume index was correlated. No TTE parameters were associated with VE/VCO2. Conclusion: Notably, echocardiographic stroke volume and tricuspid valve regurgitation peak velocity exhibited a strong correlation with absolute peak VO2/kg and percent predicted peak VO2/kg. LV stroke volume index was correlated with heart rate recovery. VE/VCO2 was not associated with any resting echocardiographic parameters, suggesting this parameter is truly exercise-dependent.

Introduction: Metabolic equivalents (METs), a measure of energy use during a specified exercise intensity, and volume of oxygen consumed (VO2) are key measurements in cardiopulmonary exercise tests (CPETs). METs are traditionally converted to VO2 via multiplying METs by 3.5 ml/kg/min when VO2 data is not available, due to the fact that the latter requires more-expensive, accurate measurements of volume of inspired and expired oxygen and CO2. However, it is unclear which populations have significant variation between peak METs and peak VO2. Research Question: In a general cardiology population, do older women have a weaker relationship between peak METs and peak VO2? Methods: We present a retrospective study analyzing the relationship of peak METs and peak VO2 achieved on a CPET. Patients presenting to the cardiology clinic who received a CPET from 2017-2022 were included. Patients with severe valvular dysfunction, congenital heart disease, prior coronary artery bypass grafting, or ejection fraction < 50% were removed to limit confounding. A Spearman correlation coefficient was calculated for the whole sample comparing peak METs and peak VO2. Subsequently, a subgroup of women age 65 or greater were compared to the general sample by a fisher’s z transformation. Results: 1907 patients were included. There was a strong positive correlation between peak VO2 and peak METs in the whole sample (r(1860) = 0.914), p<0,001), shown in Figure 1. Women age 65 or greater had a weaker correlation (r(190)=0.808, p<0.0001) compared to the those who were not (r(1668) = 0.915, p<0.0001; z = -5.656, p<0.001), shown in Figure 2. Conclusions: Peak METs and peak VO2 have an extremely strong positive correlation in a general cardiology population. However, these relationships weaken for women age 65 or greater. METs are an accurate, cost-effective proxy measurement of VO2 in a general population, however may lack reliability for certain demographics.

Background: Patient-prosthesis mismatch (PPM) is still a frequently encountered problem after aortic valve surgery for aortic stenosis(AS). Advanced planning for prevention of PPM would be beneficial. We hypothesized that identification of severe PPM based on chosen surgical valve will predict development of severe PPM after surgery. Methods: Fifty one patients (74±13yrs) with severe aortic valve stenosis who underwent aortic valve surgery had postoperative echocardiogram (TTE) within 6 months. Severe PPM was defined as effective orifice area index (EOAI)<0.65 cm2/m2.We calculated predicted severe PPM using published references values of the prosthetic valve. We used mean value and the values one standard deviation above and below. We compared these values to the actual PPM based on postoperative TTE. Results: All patients had severe AS (MG50±7 mm Hg) and an LV EF of 56±15%. Forty four patients had tissue valves implanted and 7 had mechanical valves implanted. Mean time between postoperative TTE and surgery was 39± 60 days. When the mean reference values for the valve implanted was used, only 1 patient (2%) was predicted to have severe PPM. However, based on postoperative TTE, 6 patients (13%) had severe PPM. There was no correlation between EOAI based on postop TTE and mean published reference values (Figure).When the EOAI below one SD of the published reference value was chosen, the predicted incidence of severe PPM was 38%. When the EOAI above one SD was chosen for the reference value none of the patients were predicted to have PPM. Sensitivity and specificity to identify severe PPM was 17% and 100% for mean published reference value while it was 0% and 100% for +1 SD and 83% and 68% for -1 SD. Conclusions: 1) Use of mean published reference values markedly under estimate the true incidence of post-operative PPM and has unacceptably low sensitivity. 2) Predicted occurrence of PPM was widely variable (0% to 38%) based on the published reference values. Larger studies are needed.