Abstract 11444: Pattern of VE/VCO2 Abnormalities in Chronic Thromboembolic Pulmonary Hypertension

IntroductionBreathing efficiency (VE/VCO2 slope or nadir) predicts mortality in heart failure (HF). The usual pattern of VE/VCO2 vs. exercise intensity is a characteristic “shallow bowl” configuration allowing estimate of a VE vs. VCO2 slope both in normal controls (C) and HF patients. Slope or nadir in HF is generally > 33 vs. 25-30 in C. This pattern of VE/VCO2 may not be true for other CV diseases. ObjectiveCompare VE/VCO2 versus exercise time curves in patients with history of chronic thromboembolic pulmonary hypertension type 4 (PHT4) to HF and C referred for dyspnea on exertion. MethodsWe identified 40 consecutive cases of PHT4 versus 40 HF and 40 C over the same age range retrospectively selected from our cardiopulmonary exercise test (CPX) database. VE/VCO2 was plotted against exercise time (minutes of exercise ≈ METs), and groups were compared statistically for VE/VCO2 and peak VO2 by ANOVA followed with Tukey test, with significance set at P < .05. ResultsFigure shows higher VE/VCO2 in PHT4 vs. HF and C with a different pattern vs. exercise intensity. In severe cases (example shown) VE/VCO2 may increase continuously without plateau reaching peak values > 80. There was statistically significant difference between peak VO2 between C group vs HF and PHT4, but not among HF and PHT4, although VE/VCO2 was significant different among the three groups. Age and sex was not different among them. ConclusionVE/VCO2 was elevated in PHT4 compared to HF and C. We interpret continuously increasing VE/VCO2 as a marker of progressively worsening ventilationperfusion mismatch. Interpretation of VE/VCO2 in PHT4 cannot be based simply on nadir or slope as in HF, but a plot of the data should be visually examined to gain full understanding of the ventilatory abnormality.