Modification of left ventricular isovolumic relaxation time during dobutamine echocardiography as a diagnostic method for ischemic heart disease

Background: The diagnostic ability of dobutamine stress two-dimensional echocardiography is limited by the clarity of the echocardiographic image. In this study, left ventricular isovolumic relaxation time (IVRT) was modified and the effect of this modification on the diagnostic accuracy of dobutamine echocardiography (DE) in detecting ischemia was assessed. Methods: DE was performed in 59 subjects (34 and 25 in the control and patient group, respectively). The results were compared with coronary angiography and stress scintigraphy. We focused on the changes of the IVRT, the corrected IVRT which was the IVRT corrected for heart rate, and the modified IVRT which is the corrected IVRT modified by a new-designed equation. Results: These isovolumic relaxation variables shortened with the increment of dobutamine, dosage and were markedly prolonged when ischemia developed. The sensitivity and specificity of DE were 84% and 74%. However, using the prolongation of corrected IVRT and modified IVRT as indicators of ischemia, the specificity increased (from 74% to 91% and to 94%, respectively), without a significant reduction in sensitivity (from 84% to 76% and to 84%, respectively). Patients with positive results for these variables, as compared with negative results, had a significant result of more ischemic segments and a tendency of more diseased vessels. Conclusion: The prolongation of these isovolumic relaxation variables during myocardial ischemia improves the diagnostic accuracy of DE and is also well correlated with the severity of ischemia.