Abstract 3030: Cardiac MRI Correlates of Exercise Function in Patients with Repaired Tetralogy of Fallot
Background: In patients with repaired tetralogy of Fallot (rTOF), cardiac magnetic resonance imaging (MRI) can provide accurate measurements of ventricular mass, volumes and ejection fraction (EF), and the pulmonary regurgitation fraction (PRF). Past studies have found that, of these variables, LVEF and RVEF are the strongest independent factors associated with a poor New York Heart Association functional class. The relationship between cardiac MRI measurements and exercise function, however, has not been studied.
Purpose: To determine the relationship between the rTOF patient’s exercise function and cardiac MRI-dervied measurements.
Methods: The cardiac MRI and exercise test data of all patients who had these studies within 13 months of each other (without an intervening procedure) between 1/04 and 4/06 were retrospectively reviewed. Univariate regression analysis was used to examine the relationship between MRI and exercise test variables. The MRI variables studied included: RVEF, LVEF, PR fraction, RV and LV end diastolic volume Z scores, RV mass and RV mass:volume ratio.
Results: A total of 36 patients age 25.6±12.2 (range 10–56 yrs) were identified who met the inclusion criteria. Their aerobic capacity was depressed. Peak oxygen consumption (VO2) averaged 26.7±8.7 ml/kg/min (range: 14.3 – 53.6); 72.4±18.5% of predicted normal values (range: 47–113%). RVEF was the strongest correlate of %predicted peak VO2 (r=0.37; p=0.02). The correlation between %predicted peak VO2 and LVEF was weak (r=0.07; p=0.69). Significant relationships also did not exist between %predicted peak VO2 and any of the other MRI variables. A statistically significant correlation was also found between oxygen pulse at peak exercise (an index that reflects the forward stroke volume at peak exercise) and RVEF (r=0.46; p<0.01). No other MRI variable correlated with oxygen pulse at peak exercise.
Conclusion: In patients with rTOF, the RVEF at rest is the strongest MRI correlate of exercise function and forward stroke volume at peak exercise. These data suggest that clinical strategies designed to preserve RVEF are most likely to successfully maintain the rTOF patient’s exercise function.