The Prognostic Significance of Pulmonary Arterial Capacitance in Pulmonary Arterial Hypertension: Single‐Center Experience

Abstract

This study explores the prognostic utility of pulmonary arterial capacitance (PAC) in a diverse cohort of patients with pulmonary arterial hypertension (PAH) from a tertiary referral center and compares it with the prognostic utility of other hemodynamic parameters. PAC is a strong independent predictor of mortality in patients with PAH.Keywords: pulmonary arterial hypertension, pulmonary arterial capacitance, prognosis.Pulm Circ 2016;6(4):608-610. DOI: 10.1086/688900.The importance of pulmonary arterial capacitance (PAC) in the pathogenesis and prognostication of pulmonary arterial hypertension (PAH) is increasingly recognized. 1 PAC is a strong predictor of mortality in patients with idiopathic PAH as well as in patients with PAH related to systemic sclerosis. 2,3 However, the prognostic ability of PAC has not been demonstrated in other subtypes of PAH nor has it been compared with the prognostic ability of other hemodynamic parameters in patients with different subtypes of PAH. This report aims to address these objectives in a diverse, well-characterized cohort of patients with PAH. METHODSWe identified all consecutive, adult patients with World Health Organization (WHO) group 1 PAH (both incident and prevalent disease) from the Tufts Medical Center Pulmonary Hypertension (PH) Registry who underwent a right heart catheterization (RHC) between July 1, 2001, and December 31, 2012. Patients who had WHO group 2, 3, 4, or 5 PAH were excluded from this analysis. Parameters measured during the RHC included heart rate (HR), mean right atrial pressure (RAP), mean pulmonary artery pressure (mPAP), pulmonary capillary wedge pressure (PCWP), and cardiac output (CO) by thermodilution method. These parameters were determined by manual review of the tracings. The pulmonary vascular resistance (PVR) was calculated as (mPAP − PCWP)/CO (Wood units), cardiac index (CI) as CO/body surface area (L/min/m 2 ), pulmonary artery pulse pressure as PA systolic − PA diastolic, and PAC as stroke volume/pulmonary artery pulse pressure (mL/mmHg). Patients were followed up until death or October 1, 2015. None of the patients was lost to follow-up, and all patients who were still alive were censored at the end of follow-up.Categorical variables were summarized as numbers and percentages, whereas continuous variables were summarized as mean value ± standard deviation (SD) or median (interquartile range [IQR]), as appropriate. Receiver-operating characteristic (ROC) curves were used to evaluate the ability of PAC, mRAP, mPAP, CI, and PVR to discriminate between patients who had died within the first year after RHC and those who were still alive. The area under the ROC curve (AUC) was compared using the DeLong method. Cox proportional hazards models were used to estimate hazard ratios for these hemodynamic parameters and mortality. These models were then adjusted for age, sex, and etiology of PAH. All analyses were conducted in R version 3.2.1. RESULTSA total of 105 patients were identified in the database and included in the analysis...

Does pulmonary artery pulsatility index predict mortality in pulmonary arterial hypertension?

“…PAC has been studied and shown reasonable prognostication ability. [19][20][21] A prior study showed an AUC of 0.61 for discrimination of 1 year mortality; discriminatory ability was similar for PAC, mRAP, mean pulmonary arterial pressure, cardiac index, and PVR. 21 Cardiac index and stroke volume have been acknowledged to be strong predictors of prognosis but were not significant for prediction of mortality in our study (Table 2).…”

Multimodal assessment of right ventricle overload-metabolic and clinical consequences in pulmonary arterial hypertension

“…The most feasible option to obtain PAC is a ratio of stroke volume to pulmonary artery pulse pressure measured by RHC. Despite of the fact that this method overestimates real compliance, hence does not include amount of blood flow from the pulmonary circulation into the capillary bed during systole, it was proven as significant prognostic factor in PAH [ 23 ]. Interestingly, some studies confirmed that low PAC (and worse prognosis) was observed in PAH patients, even when PVR was normal.…”

Assessment of pulmonary arterial compliance evaluated using harmonic oscillator kinematics

“…Although PA compliance is a major determinant of RV work 14 and has great impact on prognosis in various cardiac diseases, 1 – 4 its estimation has remained challenging. Therefore, in the present study, we chose to assess PA compliance using the PPP.…”

“…Traditional catheterization-based measures of PA compliance PA compliance has traditionally been calculated using two methods: designated systolic PA compliance (sPAC), which is determined from measures of pulse pressure and stroke volume indexed to BSA and expressed as stroke volume / Pmax -Pmin (mL/mmHg Á m 2 ), [1][2][3][4] where Pmax -Pmin is the difference between the minimum and maximum PAP; and diastolic PA compliance (dPAC), which is estimated based on a two-element Windkessel model that assumes that compliance and hemodynamic resistance are constant during the measurement. 6,7 PA compliance can also be estimated based on the PAP profile during diastole.…”

“…Lower pulmonary arterial (PA) compliance has recently been shown to be strongly associated with worse survival in patients with various cardiac diseases, including pulmonary arterial hypertension (PAH), 1 congenital heart disease, 2 and left ventricular dysfunction. 3 , 4 Consequently, accurate determination and serial follow-up of PA compliance are important in the management of patients with heart failure.…”