A Predictor of Positive Drug Provocation Testing in Individuals With Saddle-Back Type ST-Segment Elevation

Background: A drug provocation test is performed to unmask a type 1 electrocardiogram (ECG) in individuals with saddle-back type ST-segment elevation in the right precordial leads (SB-ECG). The study investigated predictors of positive responders (PR) by drug testing. Methods and Results: A total of 58 consecutive individuals with SB-ECG in lead V2 were enrolled and drug testing was performed. In leads V2 at standard and the third intercostal space (V2IC3), the QRS duration was measured, the amplitudes of r' wave (r'), ST-segment 20 and 40 ms after the r' wave (r'20 and r'40, respectively), the bottom of the ST-segment (STb), the differences between r' and r'20 (r'-r'20), r' and r'40 (r'-r'40), r' and STb (r'-STb), and the descending rate of the ST-segment [(r'-r'20)/r'; DR20, (r'-r'20)/(r'-STb); DR20-STb] were also measured. Thirty-five PR had significantly longer QRS duration, larger r'20 and r'40, and smaller r'-r'20, DR20, and DR20-STb than negative responders. DR20 and DR20-STb in leads V2 and V2IC3 were most significantly different between 2 groups. The positive and negative predictive values of `DR20-STb in lead V2IC3