Abstract
Introduction: In this study, we report novel methods to investigate impact of pulmonary arterial (PA) afterload with impedance and ventricular interdependency with myocardial strain on right ventricular (RV) reserve with exercise and RV:PA coupling. Hypothesis: In pre-capillary pulmonary hypertension (PH), RV is conditioned to a higher contractility (end-systolic elastance: Ees) due to increased impedance and RV reserve is independent of left ventricle. However, in isolated post-capillary PH (Ipc-PH), RV is not conditioned due to lower impedance, yet contractility reserve is poor due to lower interventricular septal strain. Methods: In 4 subjects (Table 1), we performed invasive cardiopulmonary exercise tests with simultaneous echocardiogram for impedance quantification with spectral analysis, followed by real-time RV pressure volume loops (Figure 1A: data recorded at rest and every 25 watts till peak-exercise). Cardiac MRI was performed within 24-hours to assess myocardial function, strain, and 4D flow at rest and exercise in the bore. Results: The augmentation of RV contractility (Ees) with exercise is poor in Ipc-PH, despite an afterload (Ea) similar to the normal subject. The left ventricular septal strain is reduced in Ipc-PH which may indicate enhanced interventricular dependency. Due to increased afterload in pre-capillary PH, RV is conditioned to higher contractility (Ees), and RV reserve is possibly independent of the left ventricle. Conclusion: Our novel methods provide an opportunity to investigate mechanisms of poor RV reserve with exercise in different phenotypes of PH. We will further validate these preliminary findings in our ongoing studies.
Published Version
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