Detecting Restenosis after Percutaneous Coronary Intervention Using Exercise-Stress Electrocardiogram Findings Including QT Dispersion

Despite the advent of drug-eluting stents in Japan, bare metal stents or conventional balloon angioplasty are still indicated in some patients needing elective percutaneous coronary intervention (PCI) and in patients with acute coronary syndrome if these patients develop side effects while taking ticlopidine. In such patients, restenosis is a problem that is difficult to diagnose. To investigate the comparative diagnostic accuracy of the exercise-stress electrocardiogram (ECG) for detecting restenosis after PCI, we measured conventional ST-segment changes and QT dispersion during exercise-stress testing in 173 patients with elective PCI (63 ± 10 years old). Exercise-stress testing was performed 3 to 6 months after successful PCI, and restenosis was confirmed by follow-up coronary angiogram. There were 98 patients with a prior myocardial infarction (prior MI group and 76 patients with no prior myocardial infarction (no MI group). Restenosis was found in 45 patients (46% in the prior MI group and 26 patients (34%) in the no MI group. Conventional ST-segment depression (>1:0 mm, J 60 ms indicating exercise-induced myocardial ischemia had a sensitivity of around 50% and a specificity of around 70% for diagnosing restenosis in both groups. In the prior MI group, QT dispersion was increased by exercise-stress testing in both patients with and without restenosis, whereas in the no MI group, QT dispersion increased only in patients with restenosis. With a cut-off value of >60 ms, QT dispersion had a sensitivity of 54% and a specificity of 68% for detecting restenosis in the no MI group; these values were comparable to those seen with conventional ST-segment changes. In conclusion, due to its low cost, exercise-stress ECG remains useful for diagnosing restenosis following PCI if the clinician understands its limited sensitivity and specificity. The presence of a prior MI must be considered when QT dispersion during exercise-stress testing is used for detecting restenosis.