Malignant ventricular arrhythmias appearing during acute myocardial ischaemia, are the most frequent mechanism of
sudden death. ST-T alternans is the result of an intraischaemic conduction delay and is frequently associated with those potentially lethal arrhythmias. In fact, such a phenomenon was seen in 35% of 46/86 patients with
Prinzmetal's variant angina who showed ventricular arrhythmias during ischaemia, while it was never observed in the remaining 40 patients without arrhythmias during ischaemia. Therefore ST-segment alternans should be considered a reliable marker of the possible occurrence of ventricular arrhythmias during myocardial ischaemia. ST-T-segment alternans is associated with R alternans, as clearly demonstrated by thoracic maps, and this phenomenon is due to a 2:1 intraischaemic block. The patients with
Prinzmetal's variant angina who present ventricular arrhythmias during ischaemia, show a more prominent increase of the positive area of the QRS (411.75 +/- 102.5 vs 294.05 +/- 80.3 mu volts ms), that is, a more relevant intraischaemic conduction delay. The effects of different pretreatments (
lidocaine,
propranolol and
diltiazem) on arrhythmias related to vasospastic myocardial ischaemia induced by
ergonovine maleate, were evaluated in four patients with
Prinzmetal's variant angina. As in experimental observations, neither a 'pure' antiarrhythmic agent like
lidocaine, nor a betablocking agent like
propranolol, prevented acute ischaemic ventricular arrhythmias. Only the
calcium antagonist,
diltiazem, seemed to prevent such arrhythmias. However, these findings necessitate further confirmation.