Kussmaul's Sign Correlates with Pulmonary Vascular Pathology and Reduced Exercise Right Ventricular Output Reserve

Abstract

Kussmaul's sign has been associated with right ventricular (RV) pathophysiology, and yet, a pre-heart transplantation Kussmaul's sign predicts poor outcomes even post-heart transplant, suggesting a pulmonary vascular role. The current study assesses whether Kussmaul positivity primarily reflects pathology of the RV or pulmonary vasculature, or both. In this study, 35 patients referred for right heart catheterization (RHC) for suspicion or evaluation of known pulmonary hypertension (PH) were prospectively assessed. All patients underwent resting and invasive exercise RHC hemodynamic testing, same-day cardiac magnetic resonance imaging, and RV pressure-volume loop assessment. Kussmaul sign was assessed by measuring right atrial pressure during deep inspiration. Kussmaul sign positivity was correlated to markers of RV and pulmonary vascular pathology. Of the 35 patients studied, 26 were diagnosed with PH, with 20/26 having group I pulmonary arterial hypertension (PAH). Among all subjects, Kussmaul positive patients at rest had higher pulmonary artery (PA) pressures and pulmonary vascular resistance, lower cardiac output, and higher pulmonary effective arterial elastance (Table). Kussmaul positivity did not correlate with measures of RV diastolic function (peak flow rate normalized to end-diastolic volume, tau(suga), dP/dt-min) (Table). During exercise, Kussmaul patients had higher peak pulmonary pressure and resistance, lower cardiac output, and worsened ventilatory inefficiency (Table). Among PH patients only, Kussmaul positivity no longer predicted elevated pulmonary vascular pressure, but remained correlated to deficient resting and exercise cardiac output as well as worsened ventilatory inefficiency during exercise (Table). Kussmaul positivity corresponds more closely with advanced pulmonary vascular pathology, leading to reduced right ventricular output reserve both at rest and during exercise.