Significance of ST segment depression during paroxysmal supraventricular tachycardia.

During paroxysmal supraventricular tachycardia, patients frequently experience chest pain and marked ST segment depression suggesting acute myocardial ischemia. The purpose of this study was to assess whether ST depression during supraventricular tachycardia is caused by myocardial ischemia as reflected by net myocardial lactate production. Twenty-five patients (14 men, 11 women) who had a history of paroxysmal supraventricular tachycardia and a mean age (+/- SD) of 38 +/- 14 years underwent electrophysiologic testing. Twenty-four of these patients had no evidence of coronary disease, whereas one patient had undergone previous coronary bypass surgery. Nineteen patients had orthodromic and six patients had atrioventricular node reentrant tachycardias. A 12 lead electrocardiogram and simultaneous femoral artery and coronary sinus blood samples for lactate determinations were obtained at baseline and at 5 and 10 min of supraventricular tachycardia. Mean baseline heart rate of 83 +/- 12 beats/min increased to 180 +/- 25 beats/min during supraventricular tachycardia. All patients had 1 to 8 mm of ST segment depression in 1 to 9 of the 12 leads. Chest pain occurred in 64% of patients during supraventricular tachycardia. Baseline myocardial lactate extraction was 28 +/- 13% with no significant change at 5 or 10 min of tachycardia. In contrast, in a comparison group of seven patients with known coronary artery disease, atrial pacing at 168 +/- 26 beats/min in five patients resulted in greater than or equal to 1 mm ST depression in 2 to 7 of the 12 leads and a change in lactate extraction from a baseline of 29 +/- 13% to -27 +/- 20% (p less than 0.05) indicating net myocardial lactate production.(ABSTRACT TRUNCATED AT 250 WORDS)