Jerry M. Obaldo,
Raymund Augustus O. Conlu Related Institution
Publication Sub Type
Journal Article, Original
Philippine Heart Center Journal
BACKGROUND: The ability to identify patients with severe coronary artery disease by analysis of perfusion defects alone is limited. The presence of both a perfusion abnormality and an enlarged scintigraphic LV cavity size was found to be more predictive of late cardiac events than either scintigraphic variable alone. LV cavity dilatation is a secondary indicator of LV dysfunction and indicates significant CAD.
OBJECTIVE: This study aims to establish and validate different scintigraphic parameters for LV cavity dilatation as well as cut-off values of these parameters that could be most predictive of LV cavity dilatation using the echocardiogram as gold standard.
MATERIALS AND METHODS: Patients referred for either stress or dipyridamole thallium scintigraphy at the Philippine Heart Center, 30 to 80 years of age, diagnosed with CAD, from August 2003 to August 2004. Different scintigraphic parameters used included measurement of LV cavity size in 3 orthogonal planes (L V cavity area using the short axis at the mid-LV level and distance between inner borders of the myocardium at the mid-LV level using both vertical and horizontal axes) and inferential or indirect signs of LV cavity enlargement such as absolute number of short axis slices on the scintigram, increased lung-to-heart thallium ratio and presence of significant right ventricular uptake (hypertrophy). Comparison of mean values of the different parameters were done using independent t-test. Different cut-off points were established and validation of these different parameters and cut-off values were computed.
RESULTS: A total of 100 patients, who had CAD or were CAD suspects, were included in the study. The best cutoff value for LV cavity dilatation (LV cavity area) on short axis was > 5 sq. cm with 100 percent sensitivity and 94 percent specificity. Vertical and horizontal axes measurements best correlated with 2-D echo at cut-off value of > 2.5 cm for both axes with 100 percent sensitivity, 94 percent specificity and 95 percent sensitivity, 96 percent specificity, respectively. A cut-off point of > 15 for the absolute number of short axis slices on the scintigram was noted with 85 percent sensitivity and 86 percent specificity. For abnormal lung-to-heart thallium ratio, sensitivity and specificity were 69 percent and 100 percent respectively. Prominent right ventricular uptake, suggestive of hypertrophy, was 52 percent sensitive and 100 percent specific for LV cavity enlargement.
CONCLUSION: This simple method for measurement of LV cavity size obtained from SPECT and the different inferential scintigraphic signs for L V cavity dilatation may provide important adjunct to SPECT myocardial perfusion study in identification of patients with extensive CAD and could further risk-stratify patients as to likelihood for future cardiac events.
This study aims to establish and validate different scintigraphic parameters for LV cavity dilatation as well as cut-off values of these parameters that could be most predictive of LV cavity dilatation using the echocardiogram as gold standard.