Pulmonary Artery Wedge Pressure Respiratory Variation Predicts Hemodynamic Response to Systemic Vasodilators

Purpose Obesity and lung disease may enhance pulmonary arterial wedge pressure (PAWP) respiratory variation during right heart catheterization (RHC). However, physiologic factors leading to PAWP respiratory variation (PAWPvar) are unknown, as are the implications of PAWPvar. We hypothesized that PAWPvar is associated with baseline PAWP and would predict response to sodium nitroprusside (SNP). Methods We performed a retrospective study of 88 RHC studies in 79 cardiomyopathy patients free of severe lung disease, 51 with SNP challenge, at MUSC from 2012 to 2019. PAWPvar was defined as expiratory minus inspiratory PAWP. Results Baseline %PAWPvar was inversely correlated with baseline PAWP (R = -0.5) (Figure 1A). SNP administration led to increased %PAWPvar (+27%, p median) did not (-0.6 ± 4 mmHg; p=0.003). Those who had >median PAWPvar increase with SNP had greater cardiac output (CO) augmentation compared with those who had Conclusion PAWPvar declines with elevated PAWP. Further, PAWPvar increases as PAWP declines with systemic vasodilation, and those with reduced baseline PAWPvar realize greater augmentation of PAWPvar with SNP. This demonstrates that PAWPvar is reflective of both the relative left heart preload and afterload states and not due to obesity and/or pulmonary processes alone. Thus, for any given left heart filling pressure, patients with high PAWPvar or low PAWPvar may represent disparate physiologic states with different responses to afterload reduction. Indeed, we found that patients with lower baseline PAWPvar and greater SNP-induced augmentation of PAWPvar realized more SNP-associated improvement in CO. Our findings indicate that PAWPvar is a meaningful physiologic parameter which may predict response to systemic vasodilation.