Clinical significance of pulmonary arterial capacitance calculated by echocardiography in patients with advanced heart failure

Background: Advanced left heart failure (HF) often accompanies post-capillary pulmonary hypertension related to RV afterload. Although pulmonary arterial capacitance (PAC), a measure of pulmonary artery compliance, reflects right ventricular (RV) afterload, the clinical utility of PAC obtained by echocardiography (echo-PAC) is not well established in advanced HF. Methods and Results: We performed right heart catheterization in advanced HF patients (n=30), calculating echo-PAC as stroke volume/(tricuspid regurgitation pressure gradient-pulmonary regurgitation pressure gradient). The difference between the echo-PAC and catheter-measured PAC values was insignificant (0.21±0.17 mL/mmHg, P=0.23). Echo-PAC values predicted both pulmonary arterial wedge pressure (PAWP) ≥18 mmHg and pulmonary vascular resistance ≥3 Wood units (P=0.02, area under the curve: 0.88, cutoff value: 1.94 mL/mmHg). Next, we conducted an outcome study with advanced HF patients (n=72). Patients with echo-PAC <1.94 mL/mmHg had more advanced New York Heart Association functional class, higher B-type natriuretic peptide plasma levels, larger RV and lower RV fractional area change than those with echo-PAC ≥1.94 mL/mmHg. They also had a significantly higher rate of ventricular assist device implantation or death, even after adjustment for indices related to HF severity or RV function during a 1-year follow-up period (P<0.01). Conclusions: Decreased PAC as measured by echocardiography, indicating elevated PAWP and RV dysfunction, predicted poorer outcomes in patients with advanced HF.