RAPID ATRIAL-PACING FOR DETECTING PROVOKABLE DEMAND ISCHEMIA IN ANESTHETIZED PATIENTS

A stress test that can be performed intraoperatively might be valuable for cardiac risk stratification in patients needing urgent noncardiac surgery and for early evaluation of coronary reserve in patients unde rgoing aortocoronary bypass surgery. Therefore, we evaluated the sensi tivity and safety of rapid atrial pacing combined with electrocardiogr aphy and transesophageal echocardiography for inducing and detecting p rovokable demand ischemia in 20 anesthetized patients with multivessel coronary artery disease. Rapid atrial pacing induced ST segment chang es or new segmental wall motion abnormalities (SWMA), which were defin ed as evidence of induced ischemia in 15 of the 20 patients. Unexpecte dly, the new SWMA normalized during the first beat after abrupt cessat ion of pacing in three patients who did not show any ST segment change s. Simultaneously, left ventricular preload was severely mediately whe n pacing was abruptly discontinued. Rapid atrial pacing was safe in al l patients, but the target heart rate could not be achieved because of heart block or arterial hypotension in 4 of the 20 patients. These fi ndings raise the question of whether rapid atrial pacing is the most a ppropriate approach for inducing provokable demand ischemia in anesthe tized patients. However, its potential usefulness for predicting adver se cardiac outcomes has not been evaluated and would require larger st udies. In addition, the immediate normalization of new SWMA after abru pt cessation of pacing in some patients calls into question the validi ty of new SWMA as evidence of myocardial ischemia when left ventricula r preload is severely decreased.