Electrical alternans induced by a brief period of myocardial ischemia during percutaneous coronary intervention: The characteristic ECG morphology and relationship to mechanical alternans

Background Electrical alternans (EA) has not been fully studied in the current percutaneous coronary intervention (PCI) procedure. Objective The purpose of this study was to evaluate visible EA and the morphology of ST segment during PCI. Methods The incidence of visible EA and ST-segment morphology were studied while the coronary artery was occluded for 20 seconds. When data were available, the relationship between EA and blood pressure was analyzed. The clinical and electrocardiographic data were compared with those of the age- and sex-matched controls. Results During balloon inflation, visible EA was observed in 5 of 306 patients (1.6%) in the last 2 years. EA was limited to PCI in the proximal left anterior descending artery. The ST segment elevated to 10.1 ± 3.2 mm, followed by an alternating QRS complex with a lower ST segment (5.6 ± 1.9 mm; P = .0047) with characteristic ST-segment morphology, which is known as lambda pattern . The mean age of the 5 patients was 68 ± 20 years, and 4(80%). were men. After the release of inflation, the ST-segment level returned rapidly to baseline, followed by normalization of J point. Compared with controls, the maximal elevated ST segment was significantly higher in patients with EA (5.7 ± 2.7 mm; P = .0028). The occlusion of the proximal left anterior descending artery with more severe ischemia seemed to be a prerequisite for developing EA. A higher ST segment was associated with a lower blood pressure and vice versa. Conclusion A short period of ischemia during PCI may induce visible EA and alternating QRS complexes with a characteristic ST-segment morphology. A higher ST segment was associated with a lower blood pressure and vice versa.