Myocardial SPECT images for diagnosis of pulmonary hypertension and right ventricular hypertrophy

The utility of (99m)Tc-tetrofosmin myocardial SPECT for assessment of pulmonary hypertension and right ventricular thickness has not been well studied. We hypothesized that a ratio of right ventricular activity to left ventricular activity (RV/LV uptake ratio) from SPECT myocardial perfusion images could identify the presence of increased right ventricular wall thickness and elevated systolic pulmonary artery pressure with or without the use of attenuation correction. We identified 33 patients with normal findings on stress (99m)Tc-tetrofosmin left ventricular myocardial perfusion imaging who had a complete 2-dimensional echocardiographic study within 3 wk of the SPECT study. Two 6 × 6 pixel regions of interest were placed in the right and left ventricular free walls of both non-attenuation-corrected and attenuation-corrected SPECT images. We examined the correlation of RV/LV uptake ratio with echocardiographic right ventricular free-wall thickness and with pulmonary artery systolic pressure. RV/LV uptake ratio, measured on non-attenuation-corrected images, correlated significantly with both pulmonary artery systolic pressure (r = 0.63 and P < 0.001) and right ventricular wall thickness (r = 0.6 and P < 0.001). Receiver-operating-characteristic analysis of the use of RV/LV uptake ratio to detect significant pulmonary hypertension showed that the area under the curve was 0.78 (95% confidence interval, 0.62-0.95). However, no significant correlation of RV/LV uptake ratio with pulmonary artery systolic pressure or right ventricular wall thickness was found on attenuation-corrected images. RV/LV uptake ratio measured on SPECT images can be used to identify patients with high pulmonary artery pressure or right ventricular hypertrophy.