Prognostic importance of postbypass regional wall-motion abnormalities in patients undergoing coronary artery bypass graft surgery. SPI Research Group

Dynamic predictors of perioperative risk. Study of Perioperative Ischemia (SPI) Research Group

Reduction in perioperative cardiac morbidity requires new approaches to the management of cardiac surgery patients or high-risk noncardiac surgery patients. Studies that have addressed the perioperative dynamic predictors of risk suggest a number of conclusions. Intraoperative hypotension and tachycardia appear to be risk factors for perioperative cardiac morbidity, whereas the role of hypertension remains controversial. It has recently been shown that ischemia occurring prior to bypass doubles or triples the risk of subsequent myocardial infarction. Electrocardiographic determination of ST segment depression is used as an indicator of ischemia, as are changes in ventricular filling pressure. Although increases in left ventricular end-diastolic pressure have proved to be reliable indicators of ischemia, changes in pulmonary capillary wedge pressure or pulmonary artery diastolic pressure have not. Perioperative segmental wall-motion or wall-thickening abnormalities appear to provide the most sensitive clinical measure of ischemia. Preliminary data also suggest that transesophageal echocardiographic wall-motion abnormalities may predict adverse outcome following cardiac surgery. Recent information regarding dynamic predictors of perioperative cardiac morbidity stresses the importance of the postoperative period.

Myocardial ischemia following surgery: preliminary findings. Study of Perioperative Ischemia (SPI) Research Group

Humoral changes, changes in hemodynamics, and the incidence of ischemia appear to be highest during the postbypass-postoperative period. Preliminary data also suggest that postbypass ischemia detected by transesophageal echocardiography may be predictive of outcome. Our previous experience with postoperative hypertension following coronary artery surgery has led us to increase analgesic medication of patients during and following anesthetic emergence. Patterns of postoperative ischemia observed in patients undergoing noncardiac and cardiac surgery suggest that extension of anesthesia to the postoperative period may be beneficial with respect to suppression of ischemia. It appears that by maintaining a continuous infusion of a high dose of narcotic, postoperative myocardial ischemia can be modified. The implication is that by blunting activation of the sympathetic nervous system in the postoperative period, and preventing the resultant endocrine, metabolic, and hemodynamic changes, the imbalance of myocardial oxygen supply and demand can be shifted away from ischemia. Further investigation is needed to confirm these data, and to address the effects of modification of postoperative myocardial ischemia on eventual postoperative cardiac outcomes.

Transesophageal echocardiography: is it for everyone?

Intraoperative use of transesophageal echocardiography (TEE) to detect ischemia is more predictive of a postoperative myocardial infarction than is ECG, and two-dimensional (2-D) TEE has been shown to be more sensitive than ECG in detecting regional wall-motion abnormalities, which are highly suggestive of ischemia. More recent studies have demonstrated that postbypass TEE ischemia is predictive of an adverse outcome. Other potential diagnostic uses of TEE include evaluation and identification of intraoperative ventricular aneurysms and assessment of papillary muscle function. Intraoperative detection of thrombus and atrial myxoma has been significantly enhanced using 2-D TEE and, in the postoperative period, TEE is a more sensitive measure of pericardial tamponade than changes in hemodynamic variables. In cardiac surgery, contrast TEE has been reported to be useful in evaluating the adequacy of the delivery of cardioplegia as well as aiding in the detection of air emboli. The incorporation of Doppler into TEE probes now enhances the clinician's ability to diagnose and treat patients with valvular heart disease. The value of TEE must be weighed against cost-effectiveness and outcome as it becomes more widely used.

Intraoperative monitoring of regional wall motion abnormalities for detecting myocardial ischemia by transesophageal echocardiography

Transesophageal two-dimensional echocardiography has been used for intraoperative monitoring of regional wall motion of the left ventricle. Regional wall motion abnormality is a sensitive indicator of myocardial ischemia and the use of two-dimensional transesophageal echocardiography may have a substantial advantage for early detection of myocardial infarction and thus for initiating timely and appropriate therapy in preventing postoperative myocardial ischemia. With an expected increase in the use of intraoperative transesophageal echocardiography for monitoring regional wall motion, we described the practical aspects of transesophageal echocardiography: (1) insertion technique of transesophageal echocardiographic probe; (2) the technique for obtaining an optimal short-axis view of the left ventricle; and (3) the method for evaluating regional wall-motion abnormality and myocardial ischemia. Regional wall motion abnormality is best monitored at the mid-papillary muscle level where all three coronary arteries meet. In obtaining this view, the transesophageal echocardiographic probe was found to be predominantly located in the stomach. Failure in obtaining short-axis view of the left ventricle at this level occurred in patients with left ventricular dilatation or obesity. Because of the anatomical reason, the echocardiographic transducer cannot reach a proper plane. In anesthetized patients, air can be pushed into the stomach during induction and may disturb the visualization. The pitfalls in examining regional wall motion abnormalities include: (1) shifting of the center of left ventricular contraction; (2) inadequate direction of the scanning plane; and (3) paradoxical septal movement. Three cases are presented to demonstrate the usefulness of transesophageal echocardiography in managing coronary artery surgical patients.

Characteristics of electrocardiographic ischemia in high-risk patients undergoing surgery. Study of Perioperative Ischemia (SPI) Research Group

Perioperative cardiac morbidity remains a significant problem in both cardiac and noncardiac surgical patients. The role of perioperative myocardial ischemia appears to be important and is under active investigation. In a series of studies in 200 high-risk patients undergoing noncardiac surgery or coronary artery bypass graft (CABG) surgery, we measured the pre-, intra-, and post-operative electrocardiographic (ECG) ischemic patterns using either continuous 2-lead ambulatory (Holter) monitoring or continuous 12-lead (modified treadmill) monitoring. Electrocardiographic ischemic episodes were defined as reversible ST-segment changes lasting at least 1 min and involving a shift from baseline (adjusted for positional changes) of greater than or equal to 0.1 mV of ST depression (with slope less than or equal to 0) at J + 60 ms or 0.2 mV of ST elevation at the J-point. During the 2-day period preceding surgery, ECG ischemic changes were common, clinically silent, and usually independent of changes in myocardial oxygen demand. Intraoperatively, using continuous 12-lead ECG, we found a 25% incidence of ischemia, for which modified leads V5, V4, and II were the most sensitive. Most ECG ischemic episodes were supply-dependent, not demand-dependent. Comparing the pattern of intraoperative ischemia with the chronic ambulatory preoperative pattern, we found that, under conditions of strict hemodynamic control, intraoperative ischemia apparently recapitulated the preoperative pattern, and that the stresses of anesthesia and surgery contributed less than previously thought. The highest incidence of ischemia occurred postoperatively, ranging between 30% and 60%, in both cardiac and noncardiac surgical patients.(ABSTRACT TRUNCATED AT 250 WORDS)