Exercise testing for evaluating right ventricular (RV) function in pulmonary hypertension – A review

Figures

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  Figure 1. Schematic representing the functional, structural, and cellular phenotypes of RV adaptation in patients with Pulmonary Hypertension (PH). On exercise testing, the normal heart exhibits efficient O2 delivery, intact RV-PA coupling, normal stroke volume, TAPSE, and RV strain. Pressure changes in pulmonary hypertension initially lead to the compensated phenotype, illustrating the extra effort by the heart to prevent detrimental remodeling without compromising the ejection fraction required for effective oxygen delivery. This is grossly shown by RV hypertrophy at a higher energy cost for better contractility, consequent myocardial fibrosis, and an increased risk of myocardial ischemia.[787980] If stress persists, maladaptive changes may occur, including RV dilation leading to systolic dysfunction and tricuspid dilatation.[80] The septal tissue may also become flattened and shift to the left, affecting LV function as well.[79] Exercise testing in such a failing heart may demonstrate RV-PA uncoupling and reduced RAP. Cellular changes range from upregulation of injury-response cytokines (e.g., IL-6, TNFα) and enhanced mitochondrial function in the adaptive state to mitochondrial…

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  Figure 2. Non-invasive and invasive exercise testing modalities to evaluate Right Heart Function in patients with Pulmonary Hypertension (PH). [CPET – Cardiopulmonary Exercise Testing, iCPET – Invasive Cardiopulmonary Exercise Testing, 6MWT – 6-Minute Walk Test, mPAP – Mean Pulmonary Artery Pressure, PCWP – Pulmonary Capillary Wedge Pressure, CO – Cardiac Output, PVR – Pulmonary Vascular Resistance, VO2 – Oxygen Consumption, VE/VCO2 – Ventilatory Equivalent for Carbon Dioxide, ETCO2 – End-Tidal Carbon Dioxide, O2 pulse – Oxygen Pulse (VO2 ÷ Heart Rate), RV – Right Ventricle, TAPSE – Tricuspid Annular Plane Systolic Excursion, sPAP – Systolic Pulmonary Artery Pressure, FAC – Fractional Area Change, CMR – Cardiac Magnetic Resonance Imaging]

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  Figure 3. Sample CPET curve comparing VO2 vs. workload in a normal subject (blue), a PH patient without RV dysfunction (orange), and a PH patient with RV dysfunction (red). Note the steady rise in VO2 with incremental workload in the normal subject, a steep slope that is flattened in the two diseased states. The anaerobic threshold (AT) is marked by X on each curve, occurring earliest in the patient with RV dysfunction (~25 W), followed by the PH patient (~50-75 W), and last in the normal subject (~75-100 W). Observe how the VCO2 curve becomes steeper beyond AT, reflecting the shift to anaerobic (glycolytic) metabolism. 1 MET = 3.5 mL/kg/min.[62]