The pressure rate quotient is not an indicator of myocardial ischemia in humans. An echocardiographic evaluation.
Overview
abstract
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.
