Quantitation of mitral regurgitation using positron emission tomography

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).

Twenty-one patients with severe primary mitral valve regurgitation underwent same-day dynamic PET examinations (¹⁵O-water and ¹¹C-acetate) and CMR. PET data were reconstructed into dynamic series with short time frames during the first pass, gated ¹⁵O-water blood pool images, and gated ¹¹C-acetate myocardial uptake images. PET-based RegVol and RegF correlated strongly with CMR (RegVol: ¹⁵O-water r = 0.94, ¹¹C-acetate r = 0.91 and RegF: ¹⁵O-water r = 0.88, ¹¹C-acetate r = 0.84, p < 0.001). A systematic underestimation (bias) was found for PET (RegVol: ¹⁵O-water - 11 ± 13 mL, p = 0.002, ¹¹C-acetate - 28 ± 16 mL, p < 0.001 and RegF: ¹⁵O-water - 4 ± 6%, p = 0.01, ¹¹C-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 ¹⁵O-water and 92% for ¹¹C-acetate.

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