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Background: The pressure rate quotient (PRQ; mean arterial pressure/heart rate [MAP/HR]) less than one (PRQ < 1) has been proposed as a simple, clinically available hemodynamic index of myocardial ischemia. Recent investigations using electrocardiography (ECG) detection of myocardial ischemia have not found this index reliable. We prospectively compared PRQ < 1 to detection of myocardial ischemia via transesophageal echocardiography (TEE) and ECG in patients undergoing elective coronary artery bypass graft., Methods: Forty-six of 50 patients admitted into the study had acceptable data acquisition. Calibrated ECG leads II and V5 were recorded with a computerized ST-segment analyzer. Hemodynamic data were stored at 2-min intervals. After tracheal intubation, a 5.0-MHz TEE probe was inserted. Electrocardiography-detected ischemia was defined as new onset ST-segment deviation (> or = 1 mm) lasting for > 1 min. Transesophageal echocardiography determination of ischemia was worsening of wall motion > or = 1 grade and lasting > 1 min. PRQ < 1 was compared to ECG and/or TEE as a predictor or indicator of myocardial ischemia., Results: Electrocardiography ischemia occurred during 230 intervals in 10 patients, and in only 41 of 230 (18%) was PRQ < 1. Transesophageal echocardiography-defined ischemia occurred during 592 intervals in 9 patients, and in 119 of 592 (20%) PRQ < 1. Compared to ECG and TEE, PRQ < 1 had a low sensitivity (21%) and poor positive predictive value (25%)., Conclusions: Pressure rate quotient < 1 is an unreliable indicator and predictor of myocardial ischemia when evaluated by ECG, TEE, and the combination of these modalities in patients undergoing coronary artery bypass graft surgery.

Perioperative myocardial ischemia is associated with an increased risk of perioperative myocardial infarction (PMI). Several attempts have been made to define intraoperative hemodynamic predictors of myocardial ischemia. In a canine preparation with coronary stenosis, a pressure rate quotient (PRQ = mean arterial pressure/heart rate) less than one (PRQ less than 1) indicated subendocardial myocardial ischemia. The authors tested this hypothesis in patients undergoing elective coronary artery bypass graft operation (CABG), using electrocardiogram (ECG) ST-segment changes (leads II/V5) to diagnose myocardial ischemia. Sixty (n = 60) patients having CABG surgery were prospectively studied before initiation of cardiopulmonary bypass. Calibrated ECG leads II and V5 (diagnostic mode) were monitored continuously and recorded with the use of a Hewlett-Packard computer ST-segment analyzer. In addition, arterial and pulmonary artery pressures were monitored. Ischemia was defined as new-onset ST deviation (greater than or equal to 1 mm from the baseline ECG). ECG and hemodynamic data were stored at 2-min intervals for subsequent computer analysis. Serial creatinine phosphokinase (CPK) X MB (%) determinations and 12-lead ECGs were collected for the initial 3 postoperative days. Of the 3,463 intervals (2 min) available for study, 3,322 (96%) were satisfactorily recorded for 60 patients. Ischemia occurred during 65 intervals in 9 patients (9 of 60), of which only 34% (22 of 65) were associated with a PRQ less than 1 (P less than 0.01). In contrast, there were 466 intervals during which PRQ was less than 1, but without ECG evidence of ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)