Abstract
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Objectives: Diabetes is considered a coronary heart disease equivalent because of the increased association of diabetes and coronary artery disease (CAD). Coronary microvascular dysfunction is the initial pathological change associated with development of coronary artery disease linked with diabetes. Conventional methods like electrocardiogram or imaging methods like echocardiogram, coronary angiogram or cardiac computed tomography has limited utility in diagnosing the microvascular dysfunction associated with coronary microvasculature. This study was conducted to assess the utility of 13N-NH3 cardiac PET (stress-rest perfusion imaging) in detecting coronary microvascular dysfunction in long-standing diabetic patients without documented CAD and its comparison with non-diabetic individuals without CAD.
Methods: 30 diabetic patients without documented CAD and 28 symptomatically normal subjects without diabetes and CAD were recruited prospectively for dynamic rest-stress myocardial perfusion imaging (MPI) using 13N-NH3. HbA1c of all the patients within 1 month of the study was documented. After clinical examination, all the patients underwent dynamic rest MPI using 13N-NH3. Rest study followed by stress MPI was done in the same sitting using adenosine as coronary vasodilator. Both studies were acquired in list mode for 10 minutes and was later binned and reconstructed using 3D PET algorithm. The reconstructed data was then processed using commercially available software (Corridor 4DM version 2013.1.1.39, by Invia Solutions) for calculation of myocardial blood flow (MBF) and myocardial flow reserve (MFR). Visual interpretation of scans was also performed for myocardial perfusion defects.
Results: There were 30 patients (19 men, 11 women; mean age: 57.4 ± 8.5 years; mean duration of diabetes: 9.1 ± 6.1 years; mean HbA1c: 9.2 ± 2.2) in the diabetic group and 28 patients (5 men, 23 women; mean age: 52.9 ± 12.4 years; mean HbA1c: 5.7 ± 0.4) in the non-diabetic group. 11 subjects (36.7%) had perfusion defects in diabetic group, whereas only 6 subjects (21.4%) had the same in non-diabetic group. There was significant difference of perfusion defect quantification between the groups (mean: 20.7 ± 10.4% in diabetic group and 7.3 ± 2.4% in non-diabetic group; p=0.007). There were no statistically significant differences in global stress MBF (mean: 2.35 ± 0.6 ml/gm/min in diabetic group and 2.9 ± 0.5 ml/gm/min in non-diabetic group; p=0.63) and global MFR (mean- 2.3 ± 0.7 in diabetic group and 2.7 ± 0.6 in non-diabetic group; p=0.23) between the groups. But there was statistically significant negative correlation between diabetes and MBF during stress (r = -0.426; p=0.001). Diabetes was also found to have a significant negative correlation with global MFR (r = -0.273; p=0.038).
Conclusions: The present study shows the significance of estimation of myocardial blood flow and myocardial flow reserve in diabetic patients asymptomatic for CAD. Based on our study, rest and stress MPI using 13N-NH3 cardiac PET serves to be a valuable modality in early detection of coronary microvascular dysfunction in asymptomatic diabetic patients. This modality could be of great help in understanding both the coronary blood flow abnormalities as well as the detection of coronary artery disease in diabetic patients asymptomatic for coronary artery disease.