Diagnostic Invasive Coronary Angiography in Patients with Small Myocardial Perfusion Defects with Low Exercise Tolerance

Abstract

Background: The diagnostic and prognostic value of stress myocardial perfusion scintigraphy is well established in literature. The sensitivity and specificity of the test depends on multiple factors. The workload achieved during treadmill exercise is one of the most important determinants. Hence, we thought to assess the coronary anatomy in a group of patients with low exercise tolerance that showed small perfusion defects on stress MPI studies. Material and methods: We prospectively enrolled 50 patients with mild perfusion defects and a poor exercise tolerance. An invasive coronary angiography was done according to the clinical decision of the treating physician. All patients were subjected to full history and clinical examination. Stress SPECT Tc99m Sestamibi scintigraphy was done on basis of a 2 day stress/rest imaging protocol (Exercise duration, age predicted maximal heart rate (APMHR %), ejection fraction (EF%), transient ischemic dilatation and duke treadmill score(DTS)) were recorded. A coronary stenosis ≥ 75% was considered significant. In the current study, APMHR 0.05 is considered significant. Results: Among the study cohort, a total of 6 patients (12%) had significant CAD. In presence of a small perfusion defect in the setting of low exercise tolerance, significant CAD was observed more frequently in patients with exercise duration ≤ 7 min, APMHR <85%, transient stress induced LV cavity dilatation and moderate/high DTS. The six patients with significant angiographic lesions demonstrated single vessel disease in the whole group. Distribution of the angiographic lesions was as follows: RCA (4 patients) 66.7%, the LAD (one patient) 16.65%, and the LCX (one patient) 16.65%. Conclusion: In the setting of low exercise tolerance, negative MPI/small sized perfusion defect may not exclude significant CAD. Several clinical, stress, and SPECT-MPI findings may help to predict high risk patients. Consideration of these factors may improve the overall assessment of the likelihood of significant CAD in patients undergoing stress SPECT- MPI.