Exercise cardiovascular magnetic resonance imaging allows differentiation of low-risk pulmonary arterial hypertension

Background: Patients with pulmonary arterial hypertension (PAH) have a decreased ability to compensate for demands on increased cardiac output, such as during exercise. In this study we aimed to differentiate cardiac exercise responses in patients with PAH, stratified according to known measurements of disease severity.

Methods: Right and left ventricular end-diastolic volume and end-systolic volume, stroke volume (SV), and cardiac output were measured in 20 patients with PAH and a lower risk of mortality with 6-month intervals using cardiovascular magnetic resonance (CMR) imaging during rest and during ergometer exercise (totaling 44 scans). Exercise measurements were compared with resting cardiac conditions and clinical assessment using mixed model statistics.

Results: SV response during exercise was associated with disease severity. World Health Organization functional class (WHO FC) I and right ventricular end-diastolic volume (RVEDV) <221 ml were associated with increased SV during exercise (WHO FC I: 7% increase in SV; p < 0.001). In contrast, WHO FC II was associated with an 8% decrease in SV (p = 0.02), and SV response declined progressively with right ventricular dilation (7-ml decrease in SV per 100-ml increase in RVEDV; p < 0.001).

Conclusions: Assessment of right ventricular function with CMR during exercise stratifies patients currently perceived as having a low risk of mortality into different degrees of right ventricular inotropic reserve. Reduced SV during exercise is a plausible factor to increased risk of decompensation, possibly warranting targeted therapy intensification to restore right ventricular functional reserve.