(Summary based on an article by Sadi Güleç, MD; Fatih Ertab, MD, Remzi Karaoouz, MD, Muharrem Güldal, MD, Ahmet Alpman, MD; Dervip Oral, MD originally published in American Journal of Cardiology, February 1, 1999, pages 458-460.)

Few studies have investigated the role of coronary artery disease (CAD) and myocardial ischemia in the development of ST-segment depression during paroxysmal supraventricular tachycardia (PSVT). These investigators evaluated 39 patients, all at least 45 years of age, with ST-segment depression during PSVT. Exercise testing and/or thallium scintigraphy and coronary angiography were employed for all subjects and, based on these data, investigators determined that CAD and myocardial ischemia are "...one, but not the only, mechanism involved in the genesis of ST-segment depression during PSVT in patients >45 years old."

Following admission to the emergency department, patients were divided into one of two groups: Patients with ST-segment depression during PSVT (Group I, n=21) or patients without ST-segment depression during PSVT (Group II, n=18). Patients in Group I had ST-segment depression of >1 mm at 80 ms after the J point in any lead during PSVT.

Baseline characteristics were similar for all patients, regardless of ST-segment depression. All 39 patients performed treadmill exercise testing and/or thallium stress scintigraphy, and all patients in Group I underwent coronary angiography. No patients had clinical evidence of CAD upon admission.

CAD was detected in 33% (7/21) of patients in Group I. Additionally, "all patients with significant artery stenosis had evidence of myocardial ischemia on exercise thallium scintigraphy, whereas 6 had >1 mm ST-segment depression during exercise testing." No electrocardiographic parameter indicative of CAD was found. Furthermore, in Group I, only coronary risk score (the mean number of risk factors for each patient) was different between patients with or without CAD (higher in CAD patients).

Of interest, "...patients with CAD had much more significant ST depression during PSVT than during peak exercise." And, although other studies have demonstrated a positive correlation between heart rate and ST depression during PSVT, this study did not.

Overall, the investigators suggested that in PSVT patients more than 45 years of age, multiple factors, including CAD and myocardial ischemia, are involved in the genesis of ST-segment depression during PSVT and that, "The presence of
<1 mm ST-segment depression during PSVT should be considered an indication for exercise testing or thallium stress scintigraphy, even in the absence of symptoms suggesting CAD."