RESUMO
Left ventricular (LV) mass:volume ratios indexed to body size (Mi/Vi) provide risk stratification for cardiac events. We sought to determine whether Rb-82 PET mass and volume indices are similar to MRI normal values for low likelihood subjects, and whether abnormal indices are related to abnormal myocardial blood flow (MBF). Data were analyzed retrospectively for 194 patients referred for rest/stress Rb-82 PET. LV EF, volume and mass values were calculated and mass:volume ratios were indexed to patients' height and weight. MBF was computed from the first pass dynamic component of PET data. 53 patients at low likelihood of CAD had PET Mi/Vi = 1.35 ± 0.27, consistent with the MRI literature range of 1.0-1.5. Compared to patients with normal indexed volume (Vi), patients with abnormally high Vi had lower rest MBF (0.56 ± 0.24 vs 0.93 ± 0.57 ml/g/min, p = 0.0001), and lower stress MBF (0.97 ± 0.52 vs. 1.83 ± 0.96 ml/g/min, p < 0.0001). Stress EF < 50% predicted abnormal Vi with 90% accuracy. Patients with Mi/Vi < 1.0 had abnormally low rest EF (45 ± 16% vs. 60 ± 15%, p < 0.0001) and low rest MBF (0.58 ± 0.25 vs. 0.96 ± 0.59 ml/g/min, p < 0.0001). In our study population, abnormal LV volume and mass correlated with lower rest and stress MBF and EF, suggesting that the pathophysiologic explanation of these patients' increased risk is more extensive obstructive CAD.
