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Pulmonary arterial hypertension (PAH) results in chronic right heart failure, which is associated with an increase in sympathetic tone. This may adversely affect cardiac autonomic control. We investigated the changes in cardiac autonomic nervous activity in relation to disease severity in patients with PAH.In 48 ) and 41 controls, cardiac autonomic nervous activity was evaluated by measurement of heart rate variability (HRV) and baroreflex sensitivity. All patients underwent cardiopulmonary exercise testing (peak oxygen uptake 13.2¡5.1 mL?kg, minute ventilation/carbon dioxide production slope 47¡16).In patients with PAH, spectral power of HRV was reduced in the high-frequency (239¡64 versus 563¡167 ms 2 ), low-frequency (245¡58 versus 599¡219 ms 2 ) and very low-frequency bands (510¡149 versus 1106¡598 ms 2 ; all p,0.05). Baroreflex sensitivity was also blunted (5.8¡0.6versus 13.9¡1.2 ms?mmHg; p,0.01). The reduction in high-frequency (r50.3, p50.04) and lowfrequency (r50.33, p50.02) spectral power and baroreflex sensitivity (r50.46, p,0.01) was related to the reduction in peak oxygen uptake.Patients with PAH have a marked alteration in cardiac autonomic control that is related to exercise capacity and may, therefore, serve as an additional marker of disease severity.

AimsPulmonary hypertension is a clinical syndrome characterized by a progressive increase in pulmonary vascular resistance leading to right ventricular failure and death. Pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH) are key subgroups of this disorder with comparable clinical and pathological findings. Resting pulmonary haemodynamics correlate only moderately with functional parameters and do not predict prognosis in these patients sufficiently accurately. We therefore correlated exercise haemodynamics with peak oxygen uptake (peakVO 2 ) and determined their prognostic significance. Methods and resultsThirty-six consecutive patients (21 female, 54 + 15 years) with PAH (n ¼ 21) or inoperable CTEPH were studied. The mean follow-up period was 1709 + 837 days. All patients underwent right heart catheterization at rest and during exercise, and cardiopulmonary exercise testing. Patients had severe pulmonary hypertension at rest (mean pulmonary artery pressure 46 + 11 mmHg, cardiac index 2.2 + 0.6 L/min/m 2 , pulmonary vascular resistance 861 + 330 dynes/s/cm 5 ). Exercise cardiac index correlated with peakVO 2 (r ¼ 0.59, P , 0.001) and was the only independent predictor of peakVO 2 on multivariate stepwise linear regression analyses (P , 0.001). PeakVO 2 was the strongest predictor of survival (x 2 ¼ 14.5, P ¼ 0.003). Among haemodynamic variables, only exercise cardiac index (x 2 ¼ 5.6, P ¼ 0.018) and the slope of the pressure/flow relationship (x 2 ¼ 4.1, P ¼ 0.04) were significant prognostic indicators. ConclusionThe ability of the right ventricle to increase the cardiac index during exercise is an important determinant of exercise capacity in patients with pulmonary hypertension. It also predicts prognosis and might therefore be useful in the clinical assessment of these patients.--

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