Scintigaraphic assessment of viability of the ischemic myocardium while carrying out nitroglycerine-mediated and orthostatic tests

The work deals with diagnostic possibilities of single photon emission computed tomography (SPECT) of the heart and ECG-synchronized planar scintigraphy (ECG-PS) with 99mTc-tetrophosmine used to determine viability of the ischaemic myocardium in patients presenting with postmyocardium infarction cardiosclerosis. A total of 20 patients diagnosed with Ischaemic heart disease (IHD), functional class III-IV angina of effort, postmyocardium infarction cardiosclerosis were examined. All the patients underwent SPECT of the heart with 99mTc-tetrophosmine, which was carried out at rest and on the background of sublingual administration of nitroglycerine, as well as planar ECG-synchronized scintigraphy of the myocardium according to the protocol: rest - nitroglycerine-mediated - orthostatic tests. Repeat examinations at rest were performed 4-6 weeks after the coronary artery bypass (CAB). The obtained findings showed that sensitivity of perfusion SPECT with 99mTc-tetrophosmine of the myocardium amounted to 85%, specificity to 76%, and diagnostic accuracy to 82%. Calculating the diagnostic parameters of perfusion while using ECG-PS with sublingual administration of nitroglycerine demonstrated that sensitivity of the method amounted to 71%, specificity to 91%, and diagnostic accuracy to 83%. Analyzing the orthostatic test yielded sensitivity equalling 72%, specificity - 84% and diagnostic accuracy - 81%. Sensitivity of assessing myocardial contractility by means of ECG-PS using nitroglycerine amounted to 83%, with specificity of 86% and diagnostic accuracy of 85%. At the same time, sensitivity of the orthostatic test amounted to 80%, specificity to 92%, and diagnostic accuracy to 88%. Hence, carrying out SPECT and ECG-synchronized planar scintigraphy of the heart with 99mTc-tetrophosmine on the background of sublingual administration of nitroglycerine and the orthostatic test makes it possible to simultaneously assess the reserve of myocardial contractility and perfusion, thus strongly suggesting a high informative value of the techniques involved in detecting myocardial viability in patients with postmyocardium infarction cardiosclerosis.