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)     

The value of silent myocardial ischemia monitoring in the prediction of perioperative myocardial infarction in patients undergoing peripheral vascular surgery

Real-time electrocardiographic monitoring for silent myocardial ischemia was performed on 200 patients undergoing peripheral vascular surgery to try to better define those at high risk of perioperative myocardial infarction. The patients were divided into those undergoing abdominal aortic aneurysm or lower extremity revascularization procedures (group I, n = 120) and those undergoing carotid artery endarterectomy (group II, n = 80). Silent ischemia was detected during the preoperative, intraoperative, or post-operative periods in 60.8% of group I and 67.5% of group II patients. Six group I and three group II patients suffered an acute perioperative myocardial infarction with two cardiac deaths. In both groups I and II a variety of parameters based on monitoring of silent myocardial ischemia were compared between the subgroups of patients who had myocardial infarction and those who did not. The results show that in both groups there was a significantly (p less than or equal to 0.05) greater total duration of perioperative ischemic time, total number of perioperative ischemic episodes, and total duration of perioperative ischemic time as a percent of total monitoring time in patients who suffered a perioperative myocardial infarction compared to those who did not. Multivariate logistic regression analysis of preoperative characteristics in all 200 patients showed the occurrence of preoperative silent myocardial ischemia and angina at rest to be the only significant predictors of perioperative myocardial infarction. Thus perioperative monitoring for silent myocardial ischemia might noninvasively identify those patients undergoing peripheral vascular surgery who are at increased risk for perioperative myocardial infarction, permitting implementation of timely preventive measures in selected patients.     

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.     

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)     

Postoperative myocardial ischemia in patients undergoing coronary artery bypass graft surgery. S.P.I. Research Group

Cardiac morbidity and mortality after coronary artery bypass graft (CABG) surgery continue to be significant problems. To determine the prevalence, characteristics, and prognostic importance of postoperative myocardial ischemia after CABG surgery, the authors monitored 50 patients continuously for 10 perioperative days with the use of two-lead electrocardiography (ECG). ECG changes consistent with ischemia were defined as a reversible ST depression of 1 mm or greater or an elevation of 2 mm or greater from baseline, lasting at least 1 min. Baseline was adjusted for positional changes and temporal drift. All episodes were verified, with the use of the ECG monitor printout (ECG complexes), by two independent blinded investigators. Clinical care was not controlled by study protocol, and clinicians were unaware of the research data collected. Twenty-six of 50 patients (52%) had 207 episodes of perioperative ischemia (3,409 ischemic minutes). Postoperatively, ischemia developed in 48% of patients, compared with 12% preoperatively and 10% intraoperatively before bypass. Postoperative ischemia was most common in the early period (postoperative days [PODs] 0-2; 38% of patients), peaking during the first 2 h after revascularization, and less common during the late postoperative period (PODs 3-7; 24% of patients). Almost all (120 of 122; 98%) postoperative episodes (after tracheal extubation) were asymptomatic: only 9 of 70 (13%) early episodes were detected by clinical ECG monitoring. Postoperative ischemia did not appear to be related to acute changes in myocardial oxygen demand: only 39% of the postoperative episodes were preceded by a greater than 20% increase in heart rate. However, tachycardia persisted throughout the postoperative week (22-33% of all heart rates greater than 100 beats per min), and patients with postoperative ischemia (POD 0) more frequently had tachycardia (median 43% vs. 12% of the time; P less than 0.01). Five adverse cardiac outcomes occurred on the day of surgery; all five were preceded by postoperative ischemia, three by intraoperative ischemia before bypass, and none by preoperative ischemia. Patients with late postoperative ischemia did not have an adverse cardiac outcome. The authors conclude the following: 1) ischemia is more prevalent postoperatively than preoperatively or intraoperatively before bypass; 2) the incidence of postoperative ischemia peaks shortly after revascularization, during which time it is symptomatically silent, difficult to detect, and related to adverse cardiac outcome; 3) late postoperative ischemia also is silent, but it is less prevalent and not associated with in-hospital adverse cardiac outcome; and 4) a relationship between ischemia and persistently elevated postoperative heart rate may exist and warrants additional investigation.     

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.     

Limits of arterial myocardial revascularization

A prospective study of myocardial blood perfusion after coronary artery bypass graft (CABG) was conducted in two groups of patients. In group 1, a two-year assessment by exercise thallium myocardial scintigraphy without medical treatment was performed in 122 patients who consecutively underwent CABG with exclusive use of both internal mammary arteries (IMA) and gastroepiploic artery (GEA). In group 2, myocardial function and perfusion were determined by radionuclide investigations performed before and one year after CABG in 100 patients with preoperative LV dysfunction (defined as LV ejection fraction (LVEF) less than 0.40), comparing results of myocardial revascularization performed with either exclusive arterial grafts (arterial group, 54 patients) or one arterial graft (IMA) associated with a sequential vein graft (vein group, 46 patients). In group 1, 21% of patients presented silent residual electric ischemia during exercise stress testing and 26% had reversible scintigraphic ischemic defect despite complete revascularization, 18% of those in the inferior wall bypassed with GEA and 8% in the anterior wall bypassed with the right IMA. In group 2, the significant preoperative ischemia significantly decreased in both the vein group and the arterial group. LV function was significantly improved in the vein group; in contrast there was no modification of LV function in the arterial group. A multivariate analysis showed that the surgical technique used and the preoperative LVEF were independent prognostic factors of the postoperative myocardial outcome, with a positive impact of the vein use on the postoperative myocardial function recovery. It is important to recognize that arterial grafts have some limitations in the ability to supply blood flow for coronary circulation that may induce postoperatively silent residual myocardial ischemia and a lack of LV function recovery.     

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.     

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.     

The influence of propofol versus sevoflurane anesthesia on outcome in 10,535 cardiac surgical procedures

OBJECTIVE: The purpose of this study was to evaluate the possible cardioprotective effect of sevoflurane versus propofol anesthesia in patients undergoing cardiac surgery. METHODS: Ten thousand five hundred thirty-five consecutive single cardiac surgical procedures from 3 cardiac centers were reported to a common registry from 1999 to 2005. The registry was established by the National Board of Health, and reporting was obligatory for all public heart centers in Denmark. The patients were stratified according to preoperative risk factors (EuroSCORE parameters). The outcome parameters were 30-day mortality, the incidence of postoperative myocardial infarction, and the incidence of postoperative arrhythmias. RESULTS: Overall, the 30-day mortality was lower after sevoflurane (2.84%) versus propofol (3.30%), although not significantly so (p = 0.18). No difference was found in the incidence of postoperative myocardial infarction (sevoflurane, 7.76%/propofol, 7.47%). Patients with preoperative unstable angina and/or recent myocardial infarction, and thus already "preconditioned," did not show any difference in mortality between anesthetic groups, whereas patients without these predictors showed a lower postoperative mortality after sevoflurane (2.28% v 3.14%, p = 0.015), which can at least partly be explained by a preconditioning-like effect. The data suggest that patients suffering relatively severe preoperative ischemic stress benefited from propofol anesthesia, which can be related to the antioxidant effects of propofol. Patients in the sevoflurane group had a higher incidence of postoperative atrial fibrillation (28.75% v 24.87%, p < 0.001), whereas patients in the propofol group showed a higher incidence of all other arrhythmias. CONCLUSION: Sevoflurane and propofol both possess some, although different, cardioprotective properties. Sevoflurane appears to be superior to propofol in patients with little or no ischemic heart disease, such as noncoronary artery bypass graft (CABG) surgery and CABG surgery without severe preoperative ischemia, whereas propofol seems superior in patients with severe ischemia, cardiovascular instability, or in acute/urgent surgery.     

Infusion of nifedipine after coronary artery bypass grafting decreases the incidence of early postoperative myocardial ischemia

We performed a randomized study on patients undergoing elective coronary bypass grafting to examine whether postoperative infusion of nifedipine (n = 25) could reduce the incidence of isolated transient myocardial ischemia, myocardial infarction, or both. The control group (n = 25) received nitroglycerin. Hemodynamic and Holter monitoring and serial assessment of enzymatic and electrocardiographic changes were performed for all patients. Both groups showed comparable preoperative and operative data. The incidence of myocardial infarction was significantly lower in the nifedipine group (n = 1) as compared with the control group (n = 4), whereas the number of patients with isolated transient myocardial ischemia was similar in both groups (nifedipine, 3; control, 4). At the time of peak activity, levels of creatine kinase (350 +/- 129 versus 511 +/- 287 IU/mL), creatine kinase-MB (8.4 +/- 5.4 versus 17.1 +/- 11.0 IU/mL), and glutamate-oxaloacetate-transaminase (30.4 +/- 4.4 versus 41.0 +/- 7.9 IU/mL) were markedly lower in the nifedipine group (p less than 0.05). We conclude that infusion of nifedipine after elective coronary artery bypass grafting effectively decreases the incidence of myocardial infarction and the extent of myocardial necrosis during the early postoperative period.     

Cardiac arrhythmias and silent myocardial ischemia during hemodialysis

Cardiac arrhythmias are noted in a significant proportion of chronic renal failure (CRF) patients on hemodialysis (HD), and may contribute to cardiovascular mortality. A number of factors have been implicated in the genesis of these arrhythmias. The role of silent myocardial ischemia (SMI), however, has not been evaluated systematically. We prospectively studied 38 unselected CRF patients on regular HD by continuous Holter monitoring starting 24 hours before HD, lasting through the dialysis session and continued for 20 hours thereafter. The recordings were analyzed for frequency, timing and severity of supraventricular and ventricular arrhythmias and SMI as identified by ST-segment depression. Ventricular arrhythmias during HD were noted in 11 (29%) patients (group I), and were potentially life-threatening (Lown Class III and IVa) in 13%. The remaining 27 patients (group II) had no ventricular arrhythmias during HD. There was no difference in the age, sex ratio, duration of HD, blood pressure, fluctuations in weight, hematocrit, predialysis creatinine, sodium, potassium, calcium or inorganic phosphate levels between patients in the two groups. The number of patients with clinical ischemic heart disease was significantly greater in group I. SMI was noted in 72% and 33% of group I and II patients respectively (p = 0.026). 46% of those with and 25% of those without ST changes during HD developed ventricular arrhythmias during HD. Both SMI and ventricular arrhythmias were noted most frequently during the last hour of dialysis. Hypertension, diabetes mellitus and ischemic heart disease were observed more frequently amongst patients with SMI. Ventricular arrhythmias are detected in a significant proportion of CRF patients on HD. These are probably related to coronary artery disease since silent myocardial ischemia is also noted more frequently during HD in these patients. Further studies incorporating coronary angiography are needed in a larger number of patients to establish a definite causal relationship.     

The breakdown of fractal heart rate dynamics predicts prolonged postoperative myocardial ischemia

Patients with myocardial ischemia after noncardiac surgery have a three- to ninefold increased risk of adverse cardiac events. In this study we tested the hypothesis that altered preoperative heart rate variability (HRV) predicts postoperative prolonged myocardial ischemia (>10 min) in elderly surgical patients. Thirty-two patients, age 60 yr or older, admitted to hospital for surgical repair of a traumatic hip fracture with preoperative night and daytime Holter recordings were included. Holter monitoring was initiated at arrival at hospital and continued until the third postoperative morning. Conventional HRV measures along with analysis of short-term fractal scaling exponent (alpha(1)) of RR intervals were assessed for night (from 2 AM to 5 AM) and day (7 AM to 12 AM) periods in each patient. Preoperative alpha(1) was significantly lower (i.e., increased randomness in HRV) during the nighttime compared with daytime (mean +/- SEM; 0.92 +/- 0.08 versus 1.03 +/- 0.06; P = 0.002) in patients with postoperative myocardial ischemia. Patients without ischemia had no such difference. In stepwise multivariate logistic regression analysis, increased preoperative night-day difference of alpha(1) was the only independent predictor of postoperative prolonged ischemia. The odds ratio for an increase of 0.16 U in night-day difference of alpha(1) (corresponding to interquartile range) was 7.7 (95% confidence interval, 1.9-51.4; P = 0.0018). Breakdown of fractal-like heart rate dynamics is predictive for postoperative prolonged myocardial ischemia in elderly patients having emergency surgery for traumatic hip fracture. IMPLICATIONS: Night and daytime Holter recordings before surgical repair of traumatic hip fracture were analyzed with linear and nonlinear heart rate variability methods. Preoperatively increased randomness in heart rate variability was predictive for postoperative, silent prolonged myocardial ischemia. Prolonged myocardial ischemia increases the risk for adverse cardiac events.     

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.     

慢性胆囊炎伴窦性心动过缓及心肌缺血手术前后心电图改变93例的临床分析

目的探讨慢性胆囊炎伴有窦性心动过缓及心肌缺血发生比率及其术后的心电图改变。方法手术前后常规行心电图检查，对心电图异常者定期随访。对经手术及病理证实的２５０例慢性胆囊炎病人手术前后心电图所示的窦性心动过缓与心肌缺血性改变进行临床分析。结果窦性心动过缓５３例、心肌缺血４６例。随访资料完全者９３例，其中恢复正常８５例，好转３例，无改变５例。治愈好转率达９５％。结论慢性胆囊炎对心脏确有一定影响，对慢性胆囊炎，特别是已有心电图异常改变时，应积极手术治疗。     

Resistant hypertension and preoperative silent myocardial ischaemia in surgical patients

We studied 325 patients undergoing elective noncardiac surgerywho had preoperative ambulatory ECG monitoring performed fora duration of 5130 h (range 8–24 h; mean 15.8h). Sixty-foursubjects (20%) had one or more episodes of ST segment depressionconsistent with myocardial ischaemia. Of all preoperative cardiovascularvariables measured, the presence of elevated arterial pressure,despite patients being maintained on long term antihypertensivetherapy, was the only factor associated significantly with thepresence of preoperative silent myocardial ischaemia (P<0.002).This correlation was confirmed when arterial hypertension wasdefined in four separate ways. The incidence of silent ischaemiain these patients was 33–55%. We suggest that admissionarterial pressure may therefore be a useful screening test toidentify patients at risk of preoperative myocardial ischaemia.      

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.     

Technetium stannous pyrophosphate myocardial scintigrams in the recognition of myocardial infarction in patients undergoing coronary artery revascularization.

Myocardial imaging using technetium 99m stannous pyrophosphate (99mTc-PYP) has been utilized preoperatively and three to five days postoperatively to detect myocardial infarction in 48 patients undergoing aortocoronary bypass grafting, including 7 having valve replacement (5 aortic, 2 mitral) in addition to revascularization. In the total group of patients operated on there were 3 deaths (6%). Preoperatively, 26 patients had unstable angina and 10 had severe left main coronary artery disease. Eleven of the 48 (23%) were women. ECG and enzyme-proved infarctions occurred in 6 of the 48 patients (12%), but the addition of 99mTc-PYP myocardial imaging demonstrated scintigraphic evidence of infarction in 15 patients (31%), including 2 who died in the operating room. The 99mTc-PYP myocardial imaging technique, which has proved safe, simple, and relatively inexpensive in these patients, suggests that the incidence of infarction after coronary bypass operations is somewhat higher than has been previously recognized from just ECG and enzyme changes. This technique also has been of value in helping to exclude myocardial infarction in difficult clinical situations such as postoperative arrhythmias and the postpericardiotomy syndrome.     

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.     

Clinical experience with preoperative myocardial nutrition management

Three hundred and twelve elective adult coronary artery surgery patients were divided into five groups differing as to preoperative glucose or fat loading. The control group (n = 54) had a mean myocardial glycogen level of 880 mg/100 gram heart weight, a 18.5% incidence of serious ventricular arrhythmias, 24.2% dependence on vasopressors, a mean peak postoperative SGOT level of 100 IU, and a 3.7% perioperative transmural myocardial infarction rate. The 10% glucose loading group (n = 67) had elevated myocardial glycogen of 1180 mg/100 gram heart, 14.9% serious ventricular arrhythmias but a lessened dependence on vasopressors (17.9%), a peak post bypass SGOT of 74 IU, and 2.9% transmural infarction rate. A 20% glucose overnight loading group (n = 65) had myocardial glycogen level of 1270 mg/100 gram heart, a 23.0% incidence of serious ventricular arrhythmias, a significant reduction in vasopressor dependence (3.1%), no transmural myocardial infarctions, and peak post bypass SGOT of 53 IU. The intravenous fats (10% Intralipid) group (n = 57) had the highest glycogen level of 1509 mg/100 gram heart, the lowest peak SGOT of 51 IU, no infarctions, a low vasopressor dependence (5.2%), but high rate of serious ventricular arrhythmias (22.8%). The oral fat and 20% glucose loading group (n = 69) had a myocardial glycogen of 1486 mg/100 gram heart, a low vasopressor dependence rate of 4.3%, no infarctions, a peak SGOT of 66 IU, and the lowest serious ventricular arrhythmia rate of 4.3%. These results suggest that it is possible to alter prebypass myocardial substrate levels against the stresses of cardiac surgery with fat and/or glucose loading and that myocardial protection is evident.(ABSTRACT TRUNCATED AT 250 WORDS)