Significance of ST-segment Depression during Paroxysmal Supraventricular Tachycardia.

ABSTRACT

Background: ST-segment depression in ECG is a common finding during paroxysmal supraventricular tachycardia. The exact mechanism and etiology of this ST-segment depression is not always evident. In this study we have tried to evaluate the significance of ST-segment depression during supraventricular tachycardia. Methods: Hospitalized patients for elective electrophysiological study with previous (EPS) history of supraventricular tachycardia with or without ST-segment depression were evaluated clinically, by coronary angiogram and EPS. Data were analyzed by appropriate statistical methods and comparison made between groups with ST-segment depression (Group A) and without ST-segment depression (Group B). Results: Total number of patients was 66. Equal number of patients (33) was in each group. The mean age of patients was 43.8 years. There was female predominance (MF ratio 23). The mean heart rate during supraventricular tachycardia was 161 beats/min. Age, sex, coronary artery disease risk factors and heart rate during an episode of supraventricular tachycardia did not have any significant influence on ST-segment depression. Significant coronary artery disease was found in two patients in Group A and one patient in Group B. Electrophysiological study revealed that Atrio ventricular reentry tachycardia (AVRT) and AV nodal reentry tachycardia (AVNRT) were present in 28 (42.4%) and 38 (57.6%) cases respectively. Patients of group A exhibit AVRT significantly more than patients of group B.The sensitivity of ST-segment depression in correctly diagnosing coronary artery disease (CAD) was 66.7% while the specificity was 50.8%. The sensitivity of ST-segment depression in correctly differentiating AVRT was 83.3% while the specificity was 66.7%. The positive predictive value (PPV) and Negative predictive value (NPV) of the test were 75% and 76.9% respectively. Conclusion: ST-segment depression during episode of supraventricular tachycardia is a poor indicator of coronary artery disease. Presence of ST-segment depression can differentiate AVRT from AVNRT. However, >2 mm ST-segment depression was proved to be an excellent predictor of AVRT.