Silent myocardial ischemia monitoring predicts late as well as perioperative cardiac events in patients undergoing vascular surgery.

In a previous study we have shown that perioperative monitoring for silent myocardial ischemia can noninvasively identify those patients undergoing peripheral vascular surgery who are at significantly increased risk for perioperative myocardial infarction. In the present study a group of 385 patients undergoing peripheral vascular surgery was studied long-term as well as short-term to determine whether perioperative monitoring for silent ischemia can identify those patients who are at significantly increased risk of late cardiac death or late cardiac complications as well as those patients at increased risk of perioperative myocardial infarction. All patients were monitored before, during, and after operation and were divided into two groups on the basis of results of monitoring: patients whose total duration of silent ischemia as a percentage of the total duration of perioperative monitoring was 1% or greater (group I, n = 120) and those for whom this value was less than 1% (group II, n = 265). Among patients in group I 13.3% (16 of 120) suffered a perioperative myocardial infarction in contrast to only 1.1% (3 of 265) patients in group II (p less than 0.001). Multivariate logistic regression analysis of preoperative and perioperative characteristics showed that the presence of a total perioperative percent time ischemic 1% or greater and age were the only significant predictors of perioperative myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Beta blockade to decrease silent myocardial ischemia during peripheral vascular surgery

The incidence and duration of intraoperative silent myocardial ischemia have been shown to be significantly correlated with the incidence of perioperative myocardial infarction in patients undergoing peripheral vascular surgery. To assess the effectiveness of intraoperative beta blockade in limiting such silent myocardial ischemia, a group of 48 patients was treated with oral metoprolol immediately prior to peripheral vascular surgery. The total duration of intraoperative silent myocardial ischemia, the percentage of intraoperative time silent myocardial ischemia was present, the number of intraoperative episodes of silent myocardial ischemia, and the intraoperative heart rate in the treated patients were compared with those in 152 similar but untreated peripheral vascular surgery patients. The patients treated with oral metoprolol had significantly less intraoperative silent ischemia with respect to relative duration and frequency of episodes, a significantly lower intraoperative heart rate, and less intraoperative silent myocardial ischemia in terms of total absolute duration. These results suggest that beta-adrenergic activation may play a major role in the pathogenesis of silent myocardial ischemia during peripheral vascular surgery.     

Silent myocardial ischemia is not predictive of myocardial infarction in peripheral vascular surgery patients

Continuous ambulatory ECG (CAECG) monitoring has been advocated as an effective low-cost preoperative method for detecting silent myocardial ischemia in patients undergoing peripheral vascular surgery. In addition, silent ischemic events are associated with an increased incidence of postoperative myocardial infarctions. Ninety-six patients (mean age 73 years) admitted for elective aortic (24) or infrainguinal (72) operations over a 2-year period underwent 24-hour two- or three-lead CAECG monitoring. Results were reviewed by a single cardiologist blinded to the study. The criterion for ischemia was ST segment depressions of 1 mm or greater for 40 seconds or more 60 msec after the J point. Postoperative myocardial infarction was determined by ECG changes and/or elevated serum creatinine phosphokinase with positive MB isoenzymes. Risk factors included hypertension (71%), history of coronary artery disease (66%), smoking (61%), and diabetes mellitus (47%). Nine out of 96 patients (9.4%) had a positive CAECG test for silent myocardial ischemia. Only one patient (11.1%) developed postoperative myocardial infarction and there were no deaths in this group. The incidence of postoperative myocardial infarction in the nonischemic group was 16.1% (14/87). However, the mortality in this group was 6.9% (6/87). New and malignant arrhythmias requiring preoperative medical intervention were observed in seven patients (7.4%): two cases of ventricular tachycardia and five cases of atrial flutter/fibrillation. Contrary to previous reports, CAECG monitoring for silent ischemia was not a significant predictor of postoperative myocardial infarction or mortality in our patient population. However, we continue to recommend the preoperative use of CAECG monitoring as a diagnostic tool for unsuspected malignant arrhythmias.Presented at the Seventeenth Annual Meeting of the Peripheral Vascular Surgery Society, Chicago, Ill., June 7, 1992.     

Therapy insight: prophylaxis, monitoring and treatment of perioperative myocardial ischemia with emphasis on urological surgery

Unrecognized or silent perioperative myocardial ischemia is common in patients who undergo high-risk surgery, including cystectomy, and could predict cardiac morbidity and mortality in postoperative patients. This disorder is not merely a marker of extensive coronary disease but has a close association with perioperative myocardial infarction (PMI). In a review of published data, including meta-analyses, in the context of high-risk urological surgery, up to 50% of PMIs were found to go unrecognized if only clinical signs and symptoms are considered. Prevention and treatment of these previously unrecognized cardiac events might significantly reduce long-term morbidity and mortality. The emergence of reliable markers of PMI, such as increased levels of troponin I, could help in the detection of events that would have otherwise remained unnoticed. In this Review we examine the effect of these developments in the context of high-risk urological surgery. Changes to preoperative assessment, perioperative management, and prophylaxis of PMI are critically assessed. We performed a prospective audit using postoperative troponin I levels to assess the rate of silent perioperative myocardial ischemia and infarction. An increasingly proactive attitude towards perioperative monitoring for myocardial ischemia and infarction has evolved, and postoperative serial screening with troponin I might be beneficial in high-risk patients undergoing major urological surgery.     

Perioperative myocardial ischemia in patients with peripheral arterial occlusive diseases

Patients with peripheral vascular disease (PVD) often have coronary artery disease (CAD) which means an increased risk during anesthesia. The prevalence of CAD is nearly 50% among such patients. Owing to claudication, diagnostic stress tests can rarely be performed in PVD patients. In order to evaluate the frequency of transient perioperative myocardial ischemia, Holter monitoring was performed in 30 consecutive PVD patients with ASA II-III and AVK scale (Fontaine) II-IV who were undergoing femoropopliteal bypass surgery. Patients who had left bundle branch block and left ventricular hypertrophy or were taking digitalis medication were excluded from Holter monitoring. The ST-segment analysis of the frequency modulated recordings (n = 19) revealed episodes of myocardial ischemia in 26% of the patients. Most (75%) of the episodes occurred preoperatively, and 25%, during or after the anesthesia or during preparation for it. Risk factors for CAD were more often found in patients with ST segment alterations than in patients without ST segment deviations, even though the preoperative antianginal medication administered was comparable in the two subgroups. It is concluded that in a considerable subset of PVD patients silent myocardial ischemia occurs, which can be related to the different perioperative intervals by means of ST segment analyses of Holter recordings. The ST segment may allow a better insight into the cardiac state of PVD patients. Further studies are necessary in larger populations to test our suspicion.     

Clinical Predictors of Intraoperative Myocardial Ischemia in Patients with Coronary Artery Disease Undergoing Non-Cardiac Surgery

In order to detect the incidence of myocardial ischemia during the perioperative period and to determine during which situation it ocurred, continuous monitoring of the electrocardiogram by the Holter method was used in 51 patients with coronary artery disease who were undergoing a vascular surgical procedure. Clinical parameters measured preoperatively were evaluated as predictors of the occurrence of myocardial ischemia during the perioperative period. Twenty of 51 patients demonstrated 36 episodes of myocardial ischemia, which started in 11 cases during induction. Fourteen of 16 patients with disabling angina pectoris (Class III and IV) developed myocardial ischemia, whereas only six patients out of 35 with Class II or less or no angina experienced preoperative ischemic episodes ( P < 0.001). All the patients without or with only mild angina who experienced perioperative ischemia showed ST-T abnormalities at the preoperative resting electrocardiogram. Our data suggest that the risk of intraoperative myocardial ischemia can be predicted during the preoperative period by the degree of disability exhibited by patients with coronary artery disease.     

The value of radionuclide angiography as a predictor of perioperative myocardial infarction in patients undergoing abdominal aortic aneurysm resection

To define the group of patients at high risk for myocardial infarction (MI) and death associated with abdominal aortic aneurysm repair, resting gated blood pool studies were obtained on 50 such aneurysm patients preoperatively. The results indicated that three groups could be distinguished among these patients by cardiac ejection fraction. Group I (n = 25) had preoperative ejection fractions ranging from 56% to 85%. None of the patients in group I suffered an acute perioperative MI. Group II (n = 20) comprised patients with ejection fractions ranging from 36% to 55%. There was a 20% incidence of MI in group II but no cardiac deaths. Group III included five patients with ejection fractions ranging from 27% to 35%. There was an 80% incidence of perioperative MI in these patients, with one cardiac death and one cardiac arrest. All perioperative MIs occurred within the first 48 hours after surgery. In addition there was a 50% incidence of perioperative MI among all those patients who were 80 years of age or older. These results indicate guidelines for the management of patients undergoing abdominal aortic aneurysm repair based on their preoperative ejection fraction. The data further suggest that the noninvasive gated blood pool method of determining ejection fraction may serve a more broadly useful function in helping to determine which of those patients about to undergo major surgical procedures are at high risk for perioperative MI.     

Perioperative myocardial ischemia: importance of the preoperative ischemic pattern

Previous studies investigating the incidence of myocardial ischemia in patients undergoing coronary-artery bypass grafting (CABG) surgery have not considered the potential significance of the preoperative ischemic pattern in the development of intra- and postoperative myocardial ischemia and infarction. Accordingly, the authors compared the frequency and severity of pre-, intra-, and postoperative ischemic episodes (ST-segment depression greater than or equal to 0.1 mV or elevation greater than or equal to 0.2 mV) in 50 men with severe coronary artery disease scheduled for elective CABG. All subjects were monitored by continuous electrocardiography (ECG) (Holter monitor) for 2 preoperative days, intraoperatively, and 2 postoperative days (total monitoring time = 4,363 h). Routine anti-anginal medications were continued until the morning of surgery, and the anesthetic management of the patient was not controlled. During the preoperative period, 42% of the patients had ECG ischemic episodes, 87% of which were clinically silent. Only 18% developed intraoperative ischemia. Postoperatively, the incidence increased to 40%. The number of ischemic episodes/hour (epis/h) of monitoring among the three monitoring periods was similar (0.09 +/- 0.12 epis/h preoperatively, 0.11 +/- 0.20 epis/h intraoperatively, and 0.05 +/- 0.08 epis/h postoperatively; P = NS). The median duration of ischemic episodes was similar pre- and intraoperatively (16 vs. 18.5 min, P = NS), but greater postoperatively (41 min, P less than 0.05). Seventy-six per cent of the perioperative ECG ischemia occurred without acute change (+/- 20% of control) in blood pressure or heart rate.(ABSTRACT TRUNCATED AT 250 WORDS)     

Myocardial ischemia detected by transesophageal echocardiography in a patient undergoing peripheral vascular surgery

Prevention and early treatment of myocardial ischemia remain among the primary goals of the anesthesiologist taking care of high-risk patients, such as those undergoing vascular surgery. Guidelines have been published to assist in directing preoperative evaluation and optimization of cardiovascular status. Although perioperative monitoring allows early detection of ischemic events, all monitors have limitations that must be understood before they can be used effectively. We present a case of severe intraoperative myocardial dysfunction detected only by transesophageal echocardiography in a patient undergoing a peripheral vascular procedure. Preoperative and intraoperative management is also discussed.     

Automated, continuous ST segment analysis in the ECG as a monitor of myocardial ischemia during aortocoronary bypass surgery

Patients with coronary artery disease (CAD) who are subjected to cardiac and major noncardiac surgical procedures have a high incidence of perioperative myocardial ischemia. Earlier studies in patients undergoing coronary artery bypass graft surgery (CABG) indicated the frequency of postoperative myocardial infarction to be directly proportional to the incidence and severity of pre-bypass myocardial ischemia. METHODS. We investigated the incidence of pre-bypass ischemia in 50 patients undergoing elective CABG using an automated ST segment monitoring system (Marquette 7010). Analyzing leads I, II, and V5, this device measures ST segment deviations 60 ms after the J-point. Occurrence of myocardial ischemia was defined as follows: new ST segment deviations larger than 1 mm = 0.1 mV that lasted for more than at least 10 consecutive heartbeats. RESULTS. In 19 out of 50 patients (38%) we found 96 episodes of myocardial ischemia in the pre-bypass period; 47% of all ischemic episodes were associated with significant hemodynamic changes, e.g., tachycardia, hypertension, or hypotension. The incidence of ischemia was different between population sub-groups: patients with a previous infarction had a lower incidence of ischemia (35%) than patients without infarction (44%). Patients with preoperative left ventricular end diastolic pressure (LVEDP) less than 15 mm Hg had a lower incidence of ischemia (29%) than patients with LVEDP greater than 15 mm Hg (50%). Patients treated preoperatively with beta-blockers showed a significantly lower incidence of ischemia (9%) when compared to untreated patients (46%, p less than 0.05). No difference was found between patients with or without unstable angina pectoris or between patients of NYHA classes II, III, or IV. Postoperative myocardial infarction occurred in 2 patients, both with evidence of pre-bypass myocardial ischemia. CONCLUSION. Our study confirms that automated ST segment analysis is able to detect myocardial ischemia similarly to that documented in previous studies using conventional ECG lead analysis.     

Preoperative evaluation of cardiac risk using dobutamine-thallium imaging in vascular surgery

Coronary artery disease is frequently present in patients undergoing evaluation for reconstructive peripheral vascular surgery. Dobutamine-thallium imaging has been shown to be a reliable and sensitive noninvasive method for the detection of significant coronary artery disease. Eighty-seven candidates for vascular reconstruction underwent dobutamine-thallium imaging. Forty-eight patients had an abnormal dobutamine-thallium scan. Twenty-two patients had infarct only, while 26 had reversible ischemia demonstrated on dobutamine-thallium imaging. Fourteen of 26 patients with reversible ischemia underwent cardiac catheterization and 11 showed significant coronary artery disease. Seven patients underwent preoperative coronary artery bypass grafting or angioplasty. There were no postoperative myocardial events in this group. Three patients were denied surgery on the basis of unreconstructible coronary artery disease, and one patient refused further intervention. Ten patients with reversible myocardial ischemia on dobutamine-thallium imaging underwent vascular surgical reconstruction without coronary revascularization and suffered a 40% incidence of postoperative myocardial ischemic events. Five patients were denied surgery because of presumed significant coronary artery disease on the basis of the dobutamine-thallium imaging and clinical evaluation alone. Thirty-nine patients with normal dobutamine-thallium scans underwent vascular reconstructive surgery with a 5% incidence of postoperative myocardial ischemia. Dobutamine-thallium imaging is a sensitive and reliable screening method which identifies those patients with coronary artery disease who are at high risk for perioperative myocardial ischemia following peripheral vascular surgery. Presented at the Annual Meeting of the Peripheral Vascular Surgery Society, New York, New York, June 17, 1989.     

Resting gated pool ejection fraction: a poor predictor of perioperative myocardial infarction in patients undergoing vascular surgery for infrainguinal bypass grafting

Ventricular ejection fraction is widely regarded as a prognostic indicator of perioperative myocardial infarction. To evaluate this premise the prevalence of perioperative myocardial infarction or cardiac death was analyzed in relation to preoperative resting gated pool ejection fraction in 85 patients undergoing vascular surgery for infrainguinal bypass grafting. Patients were divided into three groups on the basis of ejection fraction. Group I consisted of 50 patients with ejection fractions of 56% to 92%. Nine (18%) perioperative myocardial infarctions occurred in group I, and there were no cardiac deaths. Group II consisted of 20 patients with ejection fractions of 37% to 55%. Three (15%) myocardial infarctions occurred in this group, and there were no cardiac deaths. Group III included 15 patients with ejection fractions of 20% to 35%. Three (20%) cardiac events occurred in group III including one nonfatal myocardial infarction and two (13%) cardiac deaths. Statistical analysis showed no significant difference in prevalence of cardiac events between any group. These results suggest that resting ejection fraction is a poor predictor of perioperative myocardial infarction in patients undergoing vascular surgery. Patients with normal ejection fractions, but underlying coronary artery disease, are still at significant risk for a perioperative cardiac event.     

Perioperative rate-related silent myocardial ischemia and postoperative death

A case is presented that demonstrates heart rate (HR)--related silent myocardial ischemia occurring preoperatively, subsiding intraoperatively, then recurring and leading to a post-operative cardiac death in a patient undergoing peripheral vascular surgery. This case illustrates that patients may have an ischemic threshold for HR whereby recurrent depression of the ST segment may occur during increase of HR to rates as low as 80 to 85 beats per minute (bpm), even in the absence of acute blood pressure (BP) changes. Myocardial ischemia may be HR related; however, the authors are not aware of a case that demonstrates repeated episodes of rate-related ischemia occurring at HRs well below the 100 bpm traditional definition of tachycardia. The authors conclude that patients at risk for perioperative myocardial ischemia should be identified and the hemodynamic management of these patients should include control of HR. This implies control of the physiologic variables that influence HR, along with the use of beta-adrenergic blockers. This case also demonstrates the value of Holter monitoring for ischemia, which, when done preoperatively, can detect patients at risk for unfavorable cardiac outcomes. Ischemia monitoring also may be useful during the intraoperative and postoperative periods, a time when ischemia is often silent and undetected. The early recognition of ischemia would allow for anti-ischemic interventions, which could decrease the morbidity and mortality of patients at risk for perioperative cardiac complications.     

Myocardial ischemia correlates with reduced fibrinolytic activity following peripheral vascular surgery

STUDY OBJECTIVES: To evaluate the relationship between perioperative ischemia and serial concentrations of D-dimer, which is a sensitive and specific marker of fibrinolytic activity. Myocardial ischemia and infarction are well-recognized complications of peripheral vascular surgery. We hypothesized that patients at increased risk of perioperative myocardial ischemia might be identified preoperatively by abnormal hemostatic indices. DESIGN: Prospective clinical outcomes study. SETTING: A 1,124-bed tertiary care medical center.Patients: 42 ASA physical status II, III, and IV patients undergoing peripheral vascular surgery. INTERVENTIONS: Serial D-dimer concentrations were measured preoperatively, and at 24 and 72 hours postoperatively. Continuous 12-lead ST-segment monitoring (Mortara Instrument, Inc., Milwaukee, WI) was performed with the acquisition of a 12-lead ECG every 20 seconds for 72 hours. MEASUREMENTS AND MAIN RESULTS: D-dimer measurements were performed in duplicate using the Dimer Gold assay (American Diagnostica, Greenwich CT). Ischemic episodes, as defined by continuous 12-lead ST-segment monitoring, occurred in 49% of patients. There were no demographic differences between ischemic and nonischemic groups. Although baseline D-dimer concentrations were not statistically significantly different between groups, patients experiencing perioperative myocardial ischemia generated significantly less D-dimer during the perioperative period (p = 0. 014). CONCLUSIONS: Patients with an impaired fibrinolytic response, as defined by reduced generation of D-dimer, experienced an increased incidence of perioperative myocardial ischemia.     

Silent myocardial ischemia in patients undergoing peripheral vascular surgery: incidence and association with perioperative cardiac morbidity and mortality

Atherosclerosis is a systemic disorder and coronary artery disease is highly prevalent in patients treated for lower-extremity obstructive vascular disease. Myocardial ischemia and infarction represent the most frequent and most clinically important complications of surgical procedures for lower-extremity revascularization. Despite attempts in several areas, no practical, sensitive, and specific method for identifying patients at highest risk for myocardial events postoperatively has been found before now. This study reports observations on a consecutive series of 50 patients who underwent continuous perioperative electrocardiographic monitoring with a microprocessor-based electrocardiographic ischemia monitor. Thirty-eight percent of the patients were found to have episodes of ischemia; most of these episodes were painless and would not otherwise have been recognized. Ischemia was most prominent in the postoperative rather than the preoperative or intraoperative phases. Tachycardia was often associated with ischemia. Significantly more cardiac-related morbidity and deaths occurred in patients who were documented to have silent myocardial ischemia. In fact, no cardiac events occurred in the 31 patients without ischemia (p less than 0.02). This type of ischemia monitoring represents a potential method for segregating patients at high risk for cardiac-related morbidity and death during lower-extremity revascularization.     

The effect of heart rate control on myocardial ischemia among high-risk patients after vascular surgery

Patients undergoing vascular surgery have a high risk of suffering major postoperative cardiac events. Preoperative myocardial ischemia as detected by Holter monitoring identifies a high-risk subgroup whose postoperative ischemia, similarly detected, seems to herald major cardiac events. In this study, we determined whether systematic, patient-specific postoperative heart rate control with beta-adrenergic blocker therapy decreases the incidence of postoperative ischemia among high-risk vascular surgery patients. A total of 26 of 150 patients who underwent elective vascular surgery and were monitored preoperatively by 24-h Holter were found to have significant myocardial ischemia as defined by ST-segment depression. The minimal heart rate at which this ST-segment depression occurred was identified (ischemic threshold), and these 26 patients were then randomized to receive continuous i.v. beta-blockade with esmolol or placebo plus usual medical therapy, aiming to reduce the postoperative heart rate to 20% below the ischemic threshold. All patients were monitored by Holter for 48 h postoperatively. Postoperative Holter readings were analyzed for the incidence of ischemia and for the number of hours during which heart rate was controlled below the ischemia threshold. Patients had a median of two episodes of preoperative ischemia lasting a median of 30 min (range 1-155 min). A total of 15 patients were randomized to receive esmolol, and 11 were randomized to receive placebo. The two groups were comparable with respect to clinical characteristics and incidence and duration of preoperative ischemia. Ischemia persisted in the postoperative period in 8 of 11 placebo patients (73%), but only 5 of 15 esmolol patients (33%) (P < 0.05). Of the 15 esmolol patients, 9 had mean heart rates below the ischemic threshold, and all 9 had no postoperative ischemia. A total of 4 of 11 placebo patients had mean heart rates below the ischemic threshold, and 3 of the 4 had no postoperative ischemia. There were two postoperative cardiac events among patients who had postoperative ischemia (one placebo, one esmolol) and whose mean heart rates exceeded the ischemic threshold. Our data suggest that patient-specific, strict heart rate control aiming for a predefined target based on individual preoperative ischemic threshold was associated with a significant reduction and frequent elimination of postoperative myocardial ischemia among high-risk patients and provide a rationale for a larger trial to examine this strategy's effect on cardiac risk. IMPLICATIONS: Patients who undergo peripheral vascular surgery often experience transient cardiac complications and/or permanent heart damage just after surgery because of inadequate myocardial blood flow. In this study, we identified patients at high risk of cardiac complications after vascular surgery and showed that if their heart rate was carefully controlled for 48 h after surgery, myocardial ischemia, a common marker of heart injury, was markedly reduced.     

Significance of right bundle branch block in the diagnosis of myocardial ischemia in patients undergoing coronary artery bypass grafting.

BACKGROUND: Perioperative diagnosis of myocardial ischemia following cardiac surgical procedures remains a challenging problem. Particularly, the role of new conduction disturbances as markers of postoperative ischemia is still questionable. The goal of this study was to elucidate the diagnostic significance of new postoperative right bundle branch block (RBBB) for the detection of perioperative myocardial ischemia in patients undergoing elective coronary artery bypass grafting (CABG). METHODS: In 169 consecutive patients, three-channel Holter monitoring and serial assessment of serum enzymes were performed for 48 h, and 12-lead ECG repeated for up to 5 days postoperatively. Postoperative events were classified as either myocardial infarction (MI), transient ischemic events (TIE) or various conduction disturbances. RESULTS: Transient (n=9) or permanent (n=4) RBBB occurred in 13 patients (8%); 14 patients (8%) showed signs of perioperative MI and 18 patients (11%) evidence of TIE. Peak activity of creatine-kinase (CK, 561+/-135 vs. 316+/-19, P<0.05) and CK-MB (22.7+/-3.2 vs. 13.4+/-0.8, P<0.01) were higher in patients with RBBB than in patients without perioperative ischemic events. Peak CK-MB levels were significantly higher in patients with MI as compared to those with RBBB (33.4+/-7.6 vs. 22.7+/-3.2, P<0. 05). Patients with TIE had similar perioperative enzyme levels as patients with no events. CONCLUSION: It is concluded that the combined assessment of repeated 12-lead ECG, continuous Holter monitoring and enzyme analysis allows a reliable diagnosis of perioperative myocardial ischemia and conduction disturbances. The occurrence of new RBBB following elective CABG is indicative of perioperative myocardial necrosis and thus serves as a valuable tool for the diagnosis of new, perioperative ischemic events.     

Cardiac arrhythmias and myocardial ischemia after thoracotomy for lung cancer.

The records of 598 patients undergoing a thoracic surgical procedure for lung cancer from 1975 through 1989 were reviewed for occurrence of cardiac arrhythmias and myocardial ischemic events. Atrial tachycardias occurred in 16% (94/598); atrial fibrillation was preponderant (87%), followed by supraventricular tachycardia and atrial flutter. Patients with recurrent episodes of dysrhythmias had a significantly higher mortality rate than those without episodes or with a single episode only (17% versus 2.4%; p less than 0.01). Transient ischemic electrocardiographic changes were documented in 23 patients (3.8%) and myocardial infarction in 7 (1.2%). An abnormal preoperative exercise test result and intraoperative hypotension were strongly associated with both dysrhythmia and ischemia (p less than 0.01). Pneumonectomy, ischemic changes on the electrocardiogram, and cardiac enlargement were also associated with arrhythmias (p less than 0.01). A weaker association (p less than 0.05) was found between postoperative arrhythmias and old myocardial infarction (greater than 6 months), arterial hypertension, and heart failure. Pulmonary function had no predictive value in this respect. A history of angina or old myocardial infarction was predictive of transient postoperative myocardial ischemia but not myocardial infarction. Despite improved anesthetic and monitoring techniques and more frequent use of the intensive care unit postoperatively in the last decade, the incidence of arrhythmias after thoracotomy has not decreased. More effective prevention is needed, particularly for patients with defined preoperative and perioperative risk factors.     

Comparison of cardiac morbidity between aortic and infrainguinal operations. Study of Perioperative Ischemia (SPI) Research Group.

We prospectively compared the differences in perioperative cardiac ischemic events in 140 patients undergoing major abdominal (n = 53) versus infrainguinal (n = 87) vascular operations. Preoperative dipyridamole thallium cardiac scintigraphy was performed in a subset of 38 of these patients, with treating physicians blinded to the test results. Myocardial ischemia was measured during operation with use of continuous 12-lead electrocardiography (ECG) and transesophageal echocardiography. Continuous two-lead ambulatory ECG (Holter monitoring) was performed before, during, and after operation for 4 days. Outcome events were cardiac death, nonfatal myocardial infarction, unstable angina, ventricular tachycardia, and congestive heart failure. Results of the study indicated that most demographic variables, such as age, hypertension, cigarette smoking, serum cholesterol, were comparable between patients having aortic or infrainguinal arterial operations. However, in the infrainguinal group more patients had diabetes, second vascular operations, angina pectoris, heart failure, dysrhythmias, and used digitalis. Abnormalities in preoperative Holter monitoring, ECGs, and thallium scan abnormalities were equivalent between groups. During operation, whereas Holter and ECG abnormalities were comparable, more patients undergoing aortic procedures suffered ischemia as determined by transesophageal echocardiography (26% vs 10%, p = 0.019). After operation there were 21 (24%) outcome events in patients having infrainguinal bypasses compared with 15 (28%) patients having aortic procedures (p = NS). Ischemia by Holter monitoring (n = 133) occurred after operation in 46 (57%) patients having infrainguinal operations compared with 16 (31%) patients having aortic reconstructions (p = 0.005). Because preoperative cardiac disease and adverse cardiac outcomes occurred with similar or even greater frequency in both groups of patients, we conclude that the risk for postoperative cardiac ischemic events in lower extremity vascular operations is at least as great as for aortic operations.     

Does perioperative myocardial ischemia lead to postoperative myocardial infarction?

To determine if a relationship exists between perioperative myocardial ischemia (ST segment depression greater than or equal to 0.1 mV) and postoperative myocardial infarction (PMI), nonparticipating observers recorded all ECG, hemodynamic, and other events between arrival of patients in the operating room and onset of cardiopulmonary bypass during 1,023 elective coronary artery bypass operations (CABG). The roles of preoperative patient characteristics, quality of the operation limited by disease as rated by the surgeon and duration of ischemic cardiac arrest as risk factors for PMI also were quantified. ECG ischemia occurred in 36.9% of all patients, with almost half the episodes occurring before induction of anesthesia. PMI was almost three times as frequent in patients with ischemia (6.9% vs. 2.5%) and was independent of when ischemia occurred. Ischemia was related significantly to tachycardia but not hypertension nor hypotension and was frequent in the absence of any hemodynamic abnormalities. The anesthesiologist whose patients had the highest rate of tachycardia and ischemia had the highest rate of PMI. Although neither single nor multiple preoperative patient characteristics related to PMI, suboptimal quality of operation and prolonged ischemic cardiac arrest increased the likelihood of PMI independent of the occurrence of myocardial ischemia. The authors conclude that perioperative myocardial ischemia is common in patients undergoing CABG, occurs randomly as well as in response to hemodynamic abnormalities, and is one of three independent risk factors the authors identified as related to PMI. PMI is unrelated to preoperative patient characteristics such as ejection fraction and left main coronary artery disease, and its frequency will relate primarily to perioperative management rather than patient selection.