PURPOSE: Heart rate recovery (HRR) after exercise is the result of vagal reactivation. HRR is independent of workload or age, blunted with left heart failure, and accelerated in athletes. An attenuated HRR after exercise has been shown to be predictive of mortality in congestive heart failure. We sought to study HRR after CPET in patients with pulmonary arterial hypertension (PAH).
METHODS: 27 patients [6 males and 21 females, mean age 52+/- 14 yrs] with confirmed PAH (WHO group 1); mean pulmonary Artery pressure ≥25mmHg and pulmonary capillary wedge pressure ≤18mmHg who underwent CPET were studied. Controls [n=73] were patients who underwent CPET for complaints of ‘dyspnea of uncertain origin’ but had FEV1/FVC >75 and FVC >80% predicted. HRR was defined as the difference in heart rate between peak exercise and 1 minute later; a value 12 beats/ minute (bpm) was considered abnormal. Analysis was performed with SAS®.
RESULTS: PAH patients as compared to controls (Mann-Whitney test) had lower peak oxygen consumption (VO2 Max) [12.4 vs. 20.4 ml/kg/min], lower oxygen uptake per heartbeat at peak exercise [7.3 vs. 11.3 ml/ beat]; increased ventilatory equivalent for CO2 (VE/Vco2) [41.7 vs. 34.2]; reduced partial pressure of end-tidal carbon dioxide (PETCO2) [28.5 vs. 34.5 mmHg] (p<0.001 for all comparisons). Time to achieve a recovery >12 bpm was estimated using the product-limit method. Patients with PAH, took longer to achieve a recovery of >12 bpm, although this difference was not significant (log-rank test, p<0.0791).
CONCLUSIONS: Our study reconfirms the potential clinical value of CPET in patients with PAH. In these patients measures of peak oxygen consumption and pulmonary gas exchange efficiency (VE/VCO2 and PETCO2) are reflective of underlying right ventricular dysfunction and may provide valuable prognostic insight. The data also suggests that heart rate recovery after exercise is delayed in patients with PAH.
CLINICAL IMPLICATIONS: Heart rate recovery as a prognostic variable in PAH deserves further investigation particularly to determine its role in assigning risk and assessing therapy.
DISCLOSURE: The following authors have nothing to disclose: Arunabh Talwar, Ali Sadoughi, Purvesh Patel, Tara George, Donna Tsang, Nina Kohn
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