Background: Cardiac positron emission tomography (PET) offers non-invasive assessment of perfusion and left ventricular (LV) function from a single dynamic scan. However, no prior assessment of mitral regurgitation severity by PET has been presented. Application of indicator dilution techniques and gated image analyses to PET data enables calculation of forward stroke volume and total LV stroke volume. We aimed to evaluate a combination of these methods for measurement of regurgitant volume (RegVol) and fraction (RegF) using dynamic 15O-water and 11C-acetate PET in comparison to cardiovascular magnetic resonance (CMR).

Results: Twenty-one patients with severe primary mitral valve regurgitation underwent same-day dynamic PET examinations (O-15-water and C-11-acetate) and CMR. PET data were reconstructed into dynamic series with short time frames during the first pass, gated O-15-water blood pool images, and gated C-11-acetate myocardial uptake images. PET-based RegVol and RegF correlated strongly with CMR (RegVol: O-15-water r = 0.94, C-11-acetate r = 0.91 and RegF: O-15-water r = 0.88, C-11-acetate r = 0.84, p < 0.001). A systematic underestimation (bias) was found for PET (RegVol: O-15-water - 11 +/- 13 mL, p = 0.002, C-11-acetate - 28 +/- 16 mL, p < 0.001 and RegF: O-15-water - 4 +/- 6%, p = 0.01, C-11-acetate - 10 +/- 7%, p < 0.001). PET measurements in patients were compared to healthy volunteers (n = 18). Mean RegVol and RegF was significantly lower in healthy volunteers compared to patients for both tracers. The accuracy of diagnosing moderately elevated regurgitant volume (> 30mL) was 95% for O-15-water and 92% for C-11-acetate.

Conclusions: LV regurgitation severity quantified using cardiac PET correlated with CMR and showed high accuracy for discriminating patients from healthy volunteers.