Strong linear relationship between heart rate and mean pulmonary artery pressure in exercising patients with severe precapillary pulmonary hypertension.
Chemla D, Castelain V, Hoette S, Creuze N, Provencher S, Zhu K, Humbert M, Herve P.
1EA4533-APHP-Reanimation medicale.
Abstract
The contribution of heart rate (HR) to pulmonary artery hemodynamics has been suggested in pulmonary hypertension. Our high-fidelity pressure, retrospective study tested the hypothesis that HR explained the majority of mean pulmonary artery pressure (mPAP) and pulse pressure (PApp) variation in twelve severe precapillary pulmonary hypertension patients performing incremental-load cycling while supine. Seven idiopathic pulmonary arterial hypertension and five chronic thrombo-embolic pulmonary hypertension were studied. Four-to-five PAP-thermodilution cardiac output (CO) points (mean 4.4) were obtained. Heart period was computed at 1,000Hz. At rest, mPAP was 57±9mmHg, PApp=51±11mmHg, HR=90±12bpm, stroke volume SV=50±22mL. At peak exercise, mPAP was 76±10mmHg, PApp=67±11mmHg and HR=125±19bpm (i.e.,71±10% of maximum heart rate) (each P<0.05) while SV=51±20mL (P=NS). The input resistance did not change (mPAP/CO=14.1±4.1 vs 13.5±4.4 mmHg/L/min). The relative increase in mPAP was related to the relative increase in HR (n=12; r² = 0.74), not in CO. The mPAP was linearly related to CO in 8/12 patients (median r²=0.83) and to HR in 12/12 (median r²=0.985). The parsimony principle favored the latter fit. The PApp was linearly related to mPAP in 12/12 patients (median r²=0.985), HR in 10/12 (median r²=0.97), CO in 7/12 (median r²=0.87) and SV in 1/12. Strong linear relationship between HR and mPAP was consistently documented in severe precapillary pulmonary hypertension performing supine exercise. The limited value of thermodilution CO to predict mPAP could be explained by unavoidable precision errors in CO measurement, unchanged/decreased SV on exercise, curvilinearity of the mPAP-CO relationship at high flow, or flow-independent additional mechanisms increasing mPAP on exercise.
KEYWORDS: exercise, heart rate, pulmonary artery pressure, pulmonary hypertension, right ventricle
PMID:23792679