Abstract 2159: Cardiac MRI Correlates of Exercise Function in Patients With Ebstein’s Anomaly
Background: Patients with Ebstein’s anomaly (EA) have reduced peak predicted oxygen consumption (%VO2) compared to healthy controls. Exercise function has been criteria for determining surgical intervention in adolescents and adults with EA. However, the relationship between exercise function and right ventricular size and function is unknown.
Purpose: To determine the relationship between the EA patient’s exercise function and cardiac MRI-derived measurements.
Methods: Paired data from cardiac MRI and exercise tests (ET) of all patients who had these studies within 12 months of each other between 11/2002 and 3/2009 were retrospectively reviewed. Univariate regression analysis was used to examine the relationship between MRI and ET variables. MRI variables included right ventricular (RV) ejection fraction (EF), left ventricular (LV) EF, RV and LV end diastolic volume Z scores, and tricuspid regurgitation fraction.
Results: A total of 35 patients age 25.6 ± 13.3 years (range 8.4 – 62.6 years) met inclusion criteria. Aerobic capacity was depressed: VO2 averaged 24.9 ± 6.2 ml/kg/min (range 15.2 to 41.8); 73.2 ± 15.0% of predicted normal values (range: 46.0–104.9%); p<0.001. O2 pulse, a surrogate for forward stroke volume at peak exercise, was also depressed: 9.6 ± 3.1 ml/beat (range 4.9 to 17.8); 78.0 ± 17.3% of predicted normal values (range: 46.0 – 120.0%); p<0.001. Evidence of right to left atrial shunting (O2 saturation ≤94%) was present in 13 patients (37%). Atrial shunting did not influence %VO2. There was a trend toward lower %predicted O2 pulse with lower LVEF (r=0.26; p=0.09). Significant relationships did not exist between %VO2 or %predicted O2 pulse and any other MRI variables.
Conclusion: In patients with EA, MRI measurements at rest do not correlate with exercise function or forward stroke volume at peak exercise. The ability of the EA patient’s heart to accommodate the hemodynamic demands of exercise cannot be predicted on the basis of MRI studies. Decisions regarding surgical intervention should take this into account.