Cardiovascular MR dobutamine stress in adult tetralogy of Fallot: disparity between CMR volumetry and flow for cardiovascular function.

PURPOSE

To evaluate the MR agreement of cardiac function parameters between volumetric (cine SSFP) and phase contrast flow (PC-flow) assessment in patients with repaired tetralogy of Fallot (r-TOF) and chronic pulmonary regurgitation (PR) at rest and under dobutamine stress (DS-MR).

MATERIALS AND METHODS

We studied 18 patients with r-TOF and severe chronic PR (34 ± 12.7 years, PR fraction([flow]) 44 ± 15%) by cardiac MR at rest, 10 and 20 μg/kg/min of dobutamine. We compared analogous functional parameters by volumetry and PC-flow: (i) Systemic output [left ventricle stroke volume (LV(SV)) versus aortic forward flow (AO(FF))], (ii) Pulmonary output [right ventricle stroke volume (RV(SV)) versus pulmonary forward flow (PA(FF))], (iii) PR volume [(RV(SV)-LV(SV)) versus pulmonary backward flow (PA(BF))], (iv) PR fraction [(RV(SV)-LV(SV)/RV(SV)) versus (PA(BF)/PA(FF))].

RESULTS

We found excellent Bland-Altman agreement (mean difference ± limits of agreement, mL/beat/m(2)) at rest for both the systemic (-0.8 ± 5.7) and pulmonary strokes volumes (-0.1 ± 7.6), which slightly deteriorates during DS-MR. The PR volume showed acceptable agreement at rest (-3.6 ± 15.1), but also further deteriorated during stress (5.4 ± 24). In contrast, the PR fraction showed poor agreement equally at rest (-5.6 ± 22.8) and DS-MR (3.2 ± 19.2).

CONCLUSION

In r-TOF with chronic PR, analogous functional parameters should not be used interchangeably between volumetric and PC-flow assessment during DS-MR evaluation.