Design and Clinical Evaluation of Pharmacologic Stress-Test with Dalargin for SPECT Detection of Viable Myocardium in Patients after Myocardial Infarction

Abstract

Purpose: To develop a functional stress-test with Dalargin used as a pharmacological stress agent and to study its diagnostic capabilities for quantifying the general and segmental systolic function of the left ventricle in patients with IHD using SPECT and echo methods. Material and methods: The study comprised 29 male patients with CHD-angina of 2-3 functional classes, studied on 15–25 days (on average 20 ± 2.8 days) after a large-focal myocardial infarction. A fractional step-wise injection of Dalargin was performed with step doses as 0.1 mg / kg (1 ml up to a total of 8 ml, with intervals of 90 seconds, for a total of 12 minutes), in a supine position. After each dose of Dalargin, blood pressure, heart rate, ECG were recorded, and an echocardiographic assessment of hemodynamic parameters and local contractility was carried out. At the peak of the effect of dalargin, 99mTc-Tetrofosmin was administered intravenously (370 – 540 MBq), followed by chest SPECT. Results: The optimal dose of dalargin for assessing the contractility of the LV was 0.3 mg/kg. From the data of myocardial perfusion SPECT, at dalargin test, the number of segments with normal regional blood supply increased statistically significantly from 56,0 % to 64,7 %, the number of hypoperfused segments decreased from 41.0% to 33.7% as compared to rest, and the number of non-perfused ones – from 3.0 % to 1.6 %. Spearman’s correlation coefficient between segmental contractility and local perfusion at the top dalargin inotropic effect was high and significant (R=0.67, p<0.01). The sensitivity and specificity of the pharmacological test with intravenous administration of dalargin for prediction of postoperative improvement of perfusion and contractility of the viable myocardium were: sensitivity 78.8 %, specificity 76.4 %, diagnostic accuracy 77.6 %. Conclusion. The use of the agonist of the μ - and δ-opioid receptors dalargin as a pharmacological stress-agent at perfusion SPECT and Stress Echocardiography to assess the contractile reserve of a dysfunctional viable myocardium is informative and appropriate. In patients with IHD who have suffered a myocardial infarction and are referred to myocardial revascularization, dalargin can be employed as an effective stress-agent for assessing the reserve of perfusion and contractility of dysfunctional left ventricular myocardium using perfusion SPECT and echocardiography.