[Relation between the QT interval and the severity of ventricular arrhythmias in the early phases of myocardial infarct].

The purpose of our research was to evaluate the relationship between the severity of ventricular arrhythmias in the first hours of myocardial infarction and the duration of electrical systole (QT). Twelve-lead resting electrocardiograms (ECGs) of 66 non-consecutive patients admitted to our Coronary Care Unit for myocardial infarction were retrospectively evaluated. Criteria for retrospective selection of patients were the following: 1) admission to the coronary care unit within 12 hours from the onset of myocardial infarction symptoms; 2) appropriate ECG changes suggesting acute transmural infarction (pathologic Q waves, envolving ST changes) and diagnostic elevation of serum enzymes activity; 3) good-quality ECG recordings with sinus rhythm and no conduction defects, recorded before the beginning of therapy and within the first hours after the onset of symptoms. After this first selection, the following criteria of exclusion were applied: 1) abnormal values of serum Ca++ and K+; 2) historical and/or electrocardiographic findings of a previous myocardial infarction; 3) chronic treatment with antiarrhythmic or beta-blocking drugs, digitalis or other drugs affecting the QT interval; 4) administration of drugs affecting the QT interval before admission; 5) clinical signs of left ventricular failure or cardiogenic shock at admission or during the hospitalization; 6) development of severe ventricular arrhythmias after 24 hours from the onset of symptoms. Three subgroups were individuated : group A: 39 patients with non life-threatening ventricular arrhythmias; group B: 12 patients with episodes of ventricular tachycardia within the first 12 hours of myocardial infarction; group C: 15 patients with episodes of ventricular fibrillation within the first 12 hours of myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)