Abstract 4949: Impaired Contractility Reserve in Response to Dobutamine Stress -Preclinical Indicator for Right Ventricular Dysfunction in Asymptomatic Patients with Pulmonary Regurgitation
To maintain adequate right ventricular (RV) function in patients with pulmonary regurgitation (PR), pulmonary valve replacement (PVR) should be considered before ventricular function deteriorates. Previous studies demonstrated that RV dysfunction might be evident before symptoms occur. RV dysfunction in asymptomatic patients may be recognized early by BNP levels or exercise testing. The purpose of our study was to assess the functional reserve during low-dose dobutamine-stress by preload-independent conductance-catheter technique in asymptomatic pediatric patients with chronic PR who did not match any of the current criteria for PVR. Pressure-volume loops were recorded in 12 patients (NYHA I) (mean age 12.8 years; 7.5 – 17.9 years). All patients had PR after surgical repair of tetralogy of Fallot (10 pat.), pulmonary atresia and vsd (1 pat.), or pulmonary stenosis (1 pat.). Regurgitant fraction by MRI was 36%, and mean end-diastolic RV-volume (RVEDVI) 130ml/m2 (+/− 19; range 83–147) ml/m2. Mean QRS duration was 147 (+/− 25) ms, and mean BNP level 29.3 (+/− 16.3) pg/ml. Indexes of RV function were derived at baseline level and during dobutamine. Contractility was calculated by the slope of the endsystolic pressure-volume relation (ESPVR). An increase in ESPVR during dobutamine was considered to indicate contractility reserve. ESPVR was 0.39 (+/− 0.33; SEM 0.09) mmHg/ml at baseline and 0.68 (+/− 0.42; SEM 0.12) mmHg/ml during dobutamine. Significant increase in contractility was documented only in 7/12 children (p=0.005). In the remaining 5 patients no significant increase in contractility was found following dobutamine indicating impaired contractility reserve of the RV. There was no correlation between contractility reserve and RVEDVI, QRS duration or BNP levels. Preload-independent assessment of RV contractility reserve provides preclinical information concerning RV dysfunction in asymptomatic patients with chronic PR before alterations in BNP levels appear, and before RV dimensions meet the thresholds for PVR. Low-dose dobutamine stress testing is well tolerated and may be a useful additional diagnostic tool to assess RV function in patients with chronic PR.