Impaired Pulmonary Vascular Reserve in Adults with Repaired Coarctation of Aorta: Prevalence, Correlates, and Association with Disease Severity.

Background: Pulmonary hypertension is associated with cardiovascular events, but when assessed at rest, it has limited sensitivity. Pulmonary vascular reserve can be assessed noninvasively using exercise echocardiography, but this has not been studied in adults with coarctation of aorta (COA). We hypothesized that adults with COA had worse pulmonary vascular reserve compared to controls, and that impaired pulmonary vascular reserve was associated with clinical indices of disease severity independent right ventricular (RV) indices at rest.

Method: We assessed pulmonary vascular reserve using mean pulmonary artery pressure/cardiac output (mPAP/CO) slope derived from exercise echocardiogram in 41 COA patients and 41 controls. RV contractility was assessed using RV end-systolic pressure-area ratio (RVESPAR), and RV contractile reserves was assessed as ratio of RVESPAR at peak exercise versus rest (RVESPAR_peak/rest).

Results: COA group had impaired pulmonary vascular reserve (i.e., higher mPAP/CO slope, 2.49±1.02 versus 1.03±0.59 mmHg/l/min, p<0.001) compared to controls. Impaired pulmonary vascular reserve was associated with worse aerobic capacity (lower peak oxygen consumption), neurohormonal activation (higher NT-proBNP), and worse RV contractile (lower RVESPAR_peak/rest), independent of echocardiographic indices at rest. Echocardiographic estimation of mPAP/CO slope was feasible in 85% [35/41]. Of note, the assessment of RV afterload at rest was feasible in 39 (95%) and 33 (81%) patients in the COA and control groups, respectively, but decreased to 32 (78%) and 26 (63%) patients at peak exercise in the COA and control groups, respectively, due to inability to measure tricuspid regurgitation velocity at peak exercise in some patients.

Conclusions: Patients with COA had impaired pulmonary vascular reserve, as defined by mPAP/CO slope, and higher mPAP/CO slope was associated with worse indices of disease severity.