Impaired cardiac reserve in asymptomatic patients with moderate pulmonary restenosis late after relief of severe pulmonary stenosis: evidence for diastolic dysfunction.

Background: Patients with moderate pulmonary valve restenosis late after relief of severe pulmonary stenosis (PS) may show decreased exercise tolerance. To elucidate the mechanism of decreased exercise tolerance, we evaluated cardiac response to physical and pharmacological stress in these patients and compared results with those of patients with native moderate PS.

Methods: Twenty asymptomatic patients with moderate PS were divided into 2 groups: Group I (late after relief of severe PS, n=9), and Group II (no previous intervention, n=11). All patients underwent an exercise test, dobutamine stress (DS) MRI, and delayed contrast enhanced MRI. The response to physical and pharmacological stress was compared between both groups.

Results: Group I showed impaired exercise capacity compared to Group II (VO2max=72.8% ± 3.5% vs. 102.5% ± 16.3%, p<0.001). During DS-MRI, RV-SV increased in Group II, but not in Group I (+13 ± 8 ml, -5 ± 8 ml, p<0.001). RV end-diastolic volume decreased significantly in Group I patients (p=0.006) while it did not significantly change in Group II patients. The amount of RV-SV increase (∆ RV-SV) correlated negatively with the period of moderate PS existence and the current PG in Group I (r=-0.82, p=0.007, and r=-0.68, p=0.04, respectively) but not in Group II (r=0.45, p=0.1, and r=0.40, p=0.2, respectively). Furthermore, ∆ RV-SV correlated negatively with the PG before valvuloplasty (r=-0.76, p=0.02).

Conclusion: Impaired exercise capacity in patients with moderate pulmonary restenosis after relief of severe PS is probably caused by inability to increase RV-SV. Disturbed RV filling properties, worsening in time, might play a role.