Objectives: We examined the clinical implications of phase-contrast cardiac magnetic resonance imaging (CMR) to quantify aortic regurgitation (AR).

Background: In chronic AR, (surgical) treatment is recommended before the manifestation of significant left ventricular (LV) dilation and systolic dysfunction. Echocardiography is considered as one of the gold-standards to quantify AR - because of an often limited image quality and difficulties in the measurement of regurgitant volume, echocardiographic estimation of AR may be inconclusive in several patients. Due to its good reproducibility in the assessment of LV volumes, LV function and myocardial fibrosis as well as the ability to measure regurgitant fraction and -volume using phase-contrast imaging, CMR appears as an excellent diagnostic tool to evaluate severity of AR.

Methods: 411 patients with chronic aortic regurgitation were retrospectively enrolled. They underwent echocardiography and phase-contrast CMR within one year. The severity of AR was initially classified by echocardiography. After CMR a reclassification was performed depending on the regurgitation fraction (RF) measured in phase-contrast CMR direct aortic flow: RF < 20% for mild AR (I), RF = 20-39% for moderate AR (II) and RF > 39% for severe AR (III).

Results: After initial echocardiographic grading, 171 patients had a mild, 183 a moderate and 57 patients a severe AR (Table 1). CMR led to a reclassification in 173 patients (42.1%). In mild AR only 20 patients (11.7%) were reclassified, while in moderate and severe AR 153 patients (63.8%) were reclassified.

After CMR, 39 patients were classified with severe AR, 113 patients with moderate and 259 patients with mild AR. Patients with severe AR were significantly younger, had more often a bicuspid aortic valve, a lower LV ejection fraction and a greater LV end-diastolic volume (all p<0.05). Furthermore, patients with moderate and severe AR had significantly more segments with myocardial fibrosis (p<0.05).

Conclusions: Quantification of AR by phase-contrast CMR compared to echocardiography is leading to a reclassification in numerous patients. Further investigations are needed to examine its prognostic value. 

Table 1 Crosstab for the comparison of patients with AR classified by echo (rows) and CMR (columns)