Continuous vectorcardiographic changes in relation to scintigraphic signs of reperfusion in patients with acute myocardial infarction receiving thrombolytic therapy.

摘要

OBJECTIVES. Changes in the electrical activity of the heart reflecting the infarct process can be recorded by continuous vector-ECG, a method which is now clinically available for cardiac supervision. Shifts of the ST-segment and QRS-vector reflect ischaemia and necrosis of the myocardium. Continuous vector-ECG changes were evaluated against myocardial scintigraphy in 18 patients with acute myocardial infarction treated with streptokinase in order to study the impact of improved myocardial perfusion. DESIGN. Myocardial perfusion was analysed with 99Tcm-Sestamibi (Cardiolite, DuPont Scandinavia AB, Kista, Sweden) single photon emission computerized tomography (SPECT). Registrations were performed before and after thrombolysis in order to estimate the amount of myocardium with impaired perfusion initially (threatened myocardium) and the degree of perfusion improvement in this myocardial area. X, Y, Z vectors were registered continuously by Frank leads (Ortivus Medical, Taby, Sweden). QRS-vector difference, and the time to plateau phase and the ST-vector magnitude were used as a measurement of ischaemia and size of the myocardial infarction. RESULTS. In seven out of 11 patients treated within 3 h of onset of symptoms, an improvement in myocardial perfusion in the initially hypoperfused areas was achieved in contrast to none of the seven patients treated > 3 h after onset of pain (P < 0.05). In the whole patient material, there was a negative correlation between the time to plateau level for the QRS-vector and the improvement in myocardial perfusion (r = -0.53, P < 0.05). Among patients treated within 3 h, there was a negative correlation between the plateau level for the QRS-vector magnitude compared to the improvement in myocardial perfusion (r = -0.61, P < 0.05) and a negative correlation between the plateau level and the myocardial perfusion level after therapy (r = -0.69, P < 0.05). In these patients, there were also negative correlations between the maximal ST-vector magnitude and the myocardialperfusion both before and after thrombolysis (r = -0.81, P < 0.05 and r = -61, P < 0.05, respectively). CONCLUSION. Patients with marked improvement in myocardial perfusion indicating successful thrombolysis reach their plateau levels of the QRS-change faster and have lower total QRS-vector differences than patients without successful thrombolysis as reflected by myocardial scintigraphy. Patients with a high ST-vector magnitude have low perfusion levels both before and after therapy indicating a pronounced ischaemic damage of the myocardium. Thus, VCG-changes reflect impairment in myocardial perfusion during acute myocardial infarction.