The ratio of right ventricular activity to left ventricular activity (RV/LV uptake ratio) measured from SPECT myocardial perfusion images can be used to identify patients with high pulmonary artery pressure or right ventricular hypertrophy, according to a study published in the December issue of the Journal of Nuclear Medicine Technology .
The utility of 99mTc-tetrofosmin myocardial SPECT for assessment of pulmonary hypertension and RV thickness has not been well studied. The ratio of 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, hypothesized Reza M. Mazraeshahi, MD, from the division of cardiovascular diseases at the University of Cincinnati, and colleagues.
Mazraeshahi and colleagues identified 33 patients with normal findings on stress 99mTc-tetrofosmin LV myocardial perfusion imaging who had a complete 2D echocardiographic study within three weeks of the SPECT study.
Two 6 x 6 pixel regions of interest were placed in the RV and LV free walls of both non-attenuation-corrected and attenuation-corrected SPECT images. Mazraeshahi and colleagues examined the correlation of RV/LV uptake ratio with echocardiographic right ventricular free-wall thickness and with pulmonary artery systolic pressure.
The researchers found that RV/LV uptake ratio, measured on non-attenuation-corrected images, correlated significantly with both pulmonary artery systolic pressure and RV wall thickness. 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 percent confidence interval).
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. “On the basis of the results of this study and previous observations, we believe that it is reasonable to use only non-attenuation-corrected images to assess right ventricular hypertrophy and estimate pulmonary artery hypertension,” wrote Mazraeshahi and colleagues.
Quantitative analysis of 99mTc-tetrofomin myocardial SPECT images may be useful for detection of pulmonary hypertension and right ventricular hypertrophy in patients with cardiac and pulmonary diseases, concluded Mazraeshahi and colleagues.