The additive value of transient left ventricular dilation using two-day dipyridamole 99mTc-MIBI SPET for screening coronary artery disease in patients with otherwise normal myocardial perfusion: a comparison between diabetic and non-diabetic cases

The prognostic value of transient ischemic dilation (TID) has been previously confirmed; however, its clinical significance for screening coronary artery disease (CAD) with balanced ischemia, as a cause of false negative myocardial perfusion imaging (MPI), is unclear. The goal of this study was to determine the additive diagnostic value of TID ratio for screening CAD in separate subgroups of diabetic and non-diabetics with normal perfusion. Eighty six patients with intermediate probability of CAD who had TID more than one in the presence of otherwise normal MPI using two-day technetium-99m methoxy isobutyl isonitrile (Tc-99m-MIBI) single photon emission tomography (SPET) and dipyridamole stress (summed stress score<3 and left ventricular cavity<90mL) were included in a prospective cohort study comprising two subgroups of diabetic and nondiabetic patients. An inclusive work-up with multiple noninvasive tests was performed for all patients from whom 38 cases subsequently underwent coronary angiography and 48 cases were categorized in the group with a very low likelihood (<5%) of CAD on the basis of clinical and paraclinical data over a minimum of 18 months follow up. The TID ratio was calculated using automated software. Gensini score (GS) as an indicator of severity/extent of stenosis and coronary artery index (CAI) as the number of arteries with more than 50% narrowing were calculated based on angiographic findings. Our results showed that only in diabetic patients with three-vessel disease, TID ratio (1.47 +/- 0.23) differs significantly from the other groups of CAD. In diabetic patients subgroup, TID ratio correlated strongly with GS (r=0.957, P<0.0001) and CAI (r=0.659, P=0.001), while such correlations were not seen in the non-diabetic patients. On the basis of receiver operating characteristic curve analysis for screening CAD in diabetic patients with normal myocardial perfusion, 100% sensitivity and 77.8% normalcy rate were achieved when TID more than 1.16 was regarded as abnormal. No distinct cut-off value for abnormal TID was obtained in the non-diabetic patients. In conclusion, TID in diabetic patients without regional myocardial perfusion abnormality is an important sign of CAD especially when TID ratio exceeds 1.16. The higher TID ratio in these cases may predict increasing possibility of severe and extensive CAD. The value of TID in non-diabetic patients with otherwise normal MPI is not clearly determined.