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

Abstract

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.

Introduction

Isolated pulmonary valve stenosis (PS) is a relatively common abnormality occurring in 7–12% of all congenital heart diseases (CHD) [1], [2]. Traditionally, pulmonary valve replacement was the most effective management choice [3]. However, due to the excellent results of balloon valvuloplasty [4], [5], low thresholds are currently being employed for intervention in adults. By current guidelines, any PS with a transvalvular pressure gradient > 64 mmHg is now considered a candidate for valvuloplasty. In case of a pressure gradient < 64 mmHg, management of patients is more complicated. Intervention is advocated (as a class IIa recommendation) in symptomatic patients, in patients with decreased right ventricular (RV) function and in patients with additional right to left shunting (i.e. atrial septal defect or ventricular septal defect) [2]. The New York Heart Association functional (NYHA) classification is generally used to assess symptoms, with exercise testing as an additional tool. Reduced exercise capacity has been shown in asymptomatic (according to the NYHA scale) patients with moderate PS [6], [7], although it may be difficult in clinical practice to assign this feature to the condition of PS alone. Moreover, the condition of moderate PS may differ between patients with restenosis after relief of severe PS and patients with native moderate PS. Especially patients with moderate pulmonary restenosis have shown reduced exercise capacity in previous studies [6], [7]. The underlying mechanisms for decreased exercise capacity in these patients are incompletely understood. RV function is generally normal at rest. However, assessment of cardiac reserve may unmask pathological conditions which could be responsible for decreased exercise capacity, as has been shown in several other conditions with RV pressure overload [8], [9], [10], [11]. Accordingly, we compared exercise capacity and cardiac reserve between patients with moderate pulmonary restenosis, late after relief of severe PS, and patients with native moderate PS.