Postoperative 12-lead ECG predicts peri-operative myocardial ischaemia associated with myocardial cell damage

Peri-operative myocardial ischaemia is the single most important risk factor for an adverse cardiac outcome after non-cardiac surgery. The present study examines whether intermittent 12-lead ECG recordings can be used as an early warning tool to identify patients suffering from peri-operative myocardial ischaemia and subsequent myocardial cell damage. Fifty-five vascular surgery patients at risk for or with a history of coronary artery disease were monitored for peri-operative myocardial ischaemia using intermittent 12-lead ECG recordings taken pre-operatively and at 15 min, 20 h, 48 h, 72 h and 84 h postoperatively. The effectiveness of the 12-lead ECG was gauged by examining concordance with continuous 3-channel Holter monitoring and capturing peri-operative myocardial ischaemia by serial analyses of creatine kinase myocardial band isoenzyme and cardiac troponin T and I. The incidence of peri-operative myocardial ischaemia detected by 12-lead ECG was 44% and was identifiable in most patients (88%) 15 min after surgery. The incidence of peri-operative myocardial ischaemia detected by continuous monitoring was 53%, with the most severe episodes occurring intra-operatively and during emergence from anaesthesia. The concordance of the 12-lead method with continuous monitoring was 72%. The concordance of creatine kinase myocardial band isoenzyme activity with the 12-lead method was 71% and with Holter monitoring 57%. The concordance of mass concentration of creatine kinase myocardial band with 12-lead ECG recordings was 75%, and the corresponding value for Holter monitoring was 68%. The concordance of cardiac troponin T and I levels with the 12-lead method was 85% and 87%, respectively, and concordance with Holter monitoring was 72% and 66%, respectively. The postoperative 12-lead ECG identified peri-operative myocardial ischaemia associated with subsequent myocardial cell damage in most patients undergoing vascular surgery.     

Early postoperative myocardial morbidity in patients with coronary artery disease undergoing major non-cardiac surgery: correlation with perioperative ischaemia

As a part of a study assessing early postoperative myocardial morbidity in 50 patients with active coronary artery disease undergoing major non-cardiac surgery, the ECG was monitored continuously for 24 hr after the onset of anaesthesia, using a frequency modulated (FM) Holter monitor. Concurrent automated blood pressure and pulse were measured non-invasively at three-minute intervals during anaesthesia and subsequently at five-minute intervals. Thirty patients were monitored with two-site ECG recordings, from modified V1 and V5 (Group A). Twenty patients had seventeen-site ECG monitoring, multiplexing a four by four array of precordial electrodes onto one channel of the frequency modulated recorder (Group B). Tapes were analyzed for noise, supraventricular and ventricular dysrythmias, runs of tachy- and bradycardia, and ST segment changes. These data were correlated with serial standard 12-lead ECGs and CK-MB assay in the 72 hr after surgery. Seven tapes from Group A could not be analyzed. Change (greater than 1 mm) on ST monitoring from both Groups A (14/23), B (14/20), correlated with serial 12-lead ECG and/or CK-MB changes. The majority of first ST change 19/28 (70%) occurred after anaesthesia. In 14/28 (50%) ST change occurred during episodes of tachycardia and elevated blood pressure (greater than 20% above baseline). Nine patients (9/23) in Group A had no ST change; however, six had serial 12-lead ECG and/or CK-MB changes. Six patients (6/20) in Group B had no ST changes, and none of these patients had any change of serial 12-lead ECGs or CK-MB assay. No patient complained of chest pain during the Holter monitoring period. Continual monitoring of heart rate and blood pressure and accurate ST monitoring are essential to detect and treat perioperative myocardial ischemia. A multiple-lead precordial system is substantially more sensitive than traditional two-lead ECG holter monitoring in detecting myocardial ischaemia.     

II: Perioperative Holter monitoring: clinical relevance and practice

Perioperative, mostly silent ischaemia in patients with coronary heart disease is difficult to detect by clinical examinations. Methods. During the clinical evaluation (part I of this study) we monitored patients with prior myocardial infarction (MI) by continuous electrocardiographic (ECG) recording from the evening before until the first 24?h after operation. Excluded from Holter ECG studies were patients with a bundle branch block, pacemaker, valvular heart disease, cardiomyopathy, severe hypokalaemia, and digitalis treatment. Data were recorded with a Holter 8500 recorder (Marquette Electronics) using modified V2, V4, and V5 leads (Fig. 1). Holter tapes were analysed twice with a Holter computing system (Software 5.8, Marquette Electronics), first by a blinded technician and then by the authors themselves. We defined the following criteria as pathological ST segment changes and as ischaemic episodes [7]: horizontal or downsloping ST depression of at least 1?mm or elevation of 2?mm of at least 1?min duration measured at the J-point plus 60?ms. To quantify individual levels of ischaemia we used the definition “ischaemic load” [3]: ischaemic min/h monitored per patient. The statistic evaluation did not differ from that used in part I. Results. Out of 160 patients, 100 could be examined by Holter monitoring. Because of technical problems we could not record a Holter ECG in 2 of 6 patients with reinfarction. We found one or more perioperative episodes of ST-segment depression in 25 patients (25%). Ischaemic episodes were detected in 15 patients preoperatively, in 12 intraoperatively, and in 10 postoperatively. Three patients had ischaemic episodes during all periods. Patients with pathological ST segments suffered significantly more reinfarctions (3 of 25 vs. 1 of 75 patients) and were older (mean age difference 7 years, P<0.05). Patients with ischaemic episodes and a clinical diagnosis of reinfarction (n=3) demonstrated a dramatic postoperative increase in ischaemic load. Preoperative use of beta-blocking agents did not influence the incidence of ischaemic events. The sensitivity of postoperative Holter ECG monitoring in the diagnosis of reinfarction was 50%, the specificity 92%. Conclusions. Perioperative Holter ECG monitoring is time-consuming, expensive, not very sensitive, and therefore not generally applicable for all patients with prior MI.     

How silent is perioperative myocardial ischemia? A hemodynamic, electrocardiographic, and biochemical study in patients undergoing coronary artery bypass graft surgery

OBJECTIVE: To analyze the relationship among Holter electrocardiogram (ECG) recordings, hemodynamic measurements indicative of global myocardial oxygen balance, and serum cardiac troponin I concentrations (cTnI) in the early postoperative period after coronary artery bypass graft (CABG) surgery. DESIGN: Prospective observational study. SETTING: University teaching hospital. PARTICIPANTS: Thirty patients undergoing CABG surgery. INTERVENTIONS: ECG measurements consisted of Holter and standard ECG recordings. Hemodynamic measurements included heart rate, systolic and diastolic blood pressure (SBP, DBP), pulmonary capillary wedge pressure, and cardiac index (CI). Derived indices included tension time index (TTI), rate-pressure product, pressure work index (PWI), and endocardial viability ratio (EVR). Serial measurements of cTnI concentrations were measured postoperatively; the area under the cTnI concentration time curve was calculated for each patient (AUC cTnI). MEASUREMENTS AND MAIN RESULTS: Episodes of myocardial ischemia were associated with small but significant rises in SBP (p = 0.01), DBP (p = 0.001), and TTI (p = 0.005) compared with periods without ischemia in the same patients. Serum cTnI concentrations 24 hours after cardiopulmonary bypass (p = 0.03) and AUCcTnI (p = 0.01) values were greater in patients who developed ECG myocardial ischemia compared with patients who did not. CONCLUSIONS: The small changes in hemodynamics seen, although statistically significant, are unlikely to be the primary cause of the ischemia. They more likely reflect an independent process that causes or occurs as a result of ischemic episodes. Ischemic episodes detected by the Holter monitor are associated with significant release of cardiac troponin from the myocardium.     

Frequency of electrocardiographic changes indicating myocardial ischemia during elective cesarean delivery with regional and general anesthesia: detection based on continuous Holter monitoring and serum markers of ischemia

STUDY OBJECTIVE: To determine the frequency of electrocardiographic (ECG) changes and to assess the occurrence of myocardial ischemia during elective cesarean delivery with either regional or general anesthesia. DESIGN: Randomized, prospective, single-blinded clinical trial. SETTING: Large referral hospital. PATIENTS: 40 ASA physical status I and II term parturients. INTERVENTIONS: Patients were divided randomly into two groups as follows: the regional anesthesia group (group 1, n = 20) and the general anesthesia group (group 2, n = 20). MEASUREMENTS: In each case, continuous ECG was done using a 7-lead Holter monitor in the operating room, continuing for 24 hours after surgery. All Holter traces were analyzed by a study-blinded cardiologist. Blood samples were collected preoperatively (baseline) and at one, 5, and 24 hours postoperatively. Serum troponin T, creatinine kinase-MB, and myoglobin levels were measured. MAIN RESULTS: Two patients in group 1 (10%) and one patient in group 2 (5%) showed one mm ST-segment depression for two to 5 minutes. In all 40 cases, troponin T levels were in the normal range at all time points studied. In both groups, mean serum creatinine kinase-MB and myoglobin levels at one and 5 hours postoperatively were significantly higher than at baseline (P < 0.05). These high CK-MB and myoglobin levels were returned to normal ranges at the end of the study period; none of these women showed ST-segment changes. CONCLUSION: The ST-segment changes are not frequent in healthy women undergoing elective cesarean delivery during either regional or general anesthesia, and we found no evidence of myocardial injury.     

Association between early postoperative coagulation activation and peri-operative myocardial ischaemia in patients undergoing vascular surgery

We investigated the association of peri-operative myocardial ischaemia with activation of coagulation and endogenous fibrinolysis in patients undergoing vascular surgery. In 50 patients, continuous Holter monitoring was performed to assess peri-operative myocardial ischaemia and 12-lead electrocardiography was recorded preoperatively and 72 h postoperatively to assess myocardial infarction. Serial blood samples were drawn peri-operatively to determine the concentrations of fibrin monomers (for activation of coagulation), D-dimer (for endogenous fibrinolysis) and cardiac troponin T and I. Patients with myocardial ischaemia showed higher concentrations of fibrin monomers at 48 h, and higher concentrations of d-dimer preoperatively and at 24 and 48 h postoperatively. In patients with peri-operative myocardial ischaemia, strong positive correlations were observed between fibrin monomer and D-dimer concentrations at 15 min and 4 h postoperatively, and cardiac troponins at 15 min and at 4, 24, 48 and 72 h postoperatively. Early postoperative activation of coagulation and fibrinolysis is associated with peri-operative myocardial cell damage among patients who are at risk for, or have a history of, coronary artery disease plus peri-operative myocardial ischaemia.     

Segmental wall-motion abnormalities after an arterial switch operation indicate ischemia

We prospectively studied 29 consecutive neonates undergoing an arterial switch operation to determine if segmental wall motion abnormalities (SWMA) represented myocardial ischemia. Intraoperative transesophageal echocardiogram was recorded at baseline and twice after cardiopulmonary bypass. Cardiac troponin I (cTnI) levels were measured before sternal incision and 3, 6, 12, 24, 48, and 72 h after removal of the aortic cross-clamp. Immediate postoperative Holter and 15-lead electrocardiograms (ECG) were evaluated for ischemia. Transthoracic echocardiograms were obtained before hospital discharge. At bypass termination, immediately after protamine administration, segmental wall motion was normal in nine neonates and abnormal in 20. SWMA were transient in five and present at the time of chest closure in 15 neonates. Neonates in whom SWMA were present at chest closure had more segments involved than those in whom SWMA were transient (P > 0.001). Neonates with SWMA at chest closure had higher cTnI levels postoperatively versus neonates with normal wall motion (P = 0.02). Postoperative ECG data were available in 26 neonates. There was ECG evidence of myocardial ischemia in two of eight neonates with normal wall motion, one of five with transient SWMA, and nine of 13 with SWMA at chest closure. CTnI levels at 12, 24, and 48 h and intraoperative SWMA were predictive of postoperative SWMA. We believe these data indicate that SWMA, which persist at the completion of an arterial switch operation, and which are present in multiple myocardial segments, correlate with myocardial ischemia. Further follow-up of these patients is needed to determine if increased intraoperative myocardial ischemia correlates with long-term outcomes.     

Electrocardiographic changes during cesarean section under regional anesthesia.

To determine electrocardiographic changes and whether myocardial ischemia occurs during cesarean section, electrocardiograms were recorded continuously using Holter monitoring in 25 patients undergoing elective cesarean section under either spinal or epidural anesthesia. In addition, in 13 of the patients, two-dimensional precordial echocardiography was carried out before and during cesarean section. ST segment depression suggestive of myocardial ischemia occurred in 16 patients including 8 of the 13 with echocardiograms. Wall motion remained entirely normal during episodes of ST segment depression. Patients in whom ST depression developed had significantly more rapid heart rates at delivery than those who did not experience ST depression. We conclude that ST segment depression is a common feature of the electrocardiogram during cesarean section under regional anesthesia and is not the result of myocardial ischemia.     

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.     

Failure to predict intraoperative myocardial ischaemia in patients with coronary artery disease

Patients with severe coronary artery disease were studied to determine if the preoperative assessment or intraoperative haemodynamic monitoring could predict the occurrence of myocardial ischaemia. Thirty-eight patients undergoing coronary artery surgery who had normal electrocardiograms before induction of anaesthesia were included. Leads II and CS5 were recorded on a Holter monitor and radial arterial and pulmonary artery catheters were used to measure haemodynamic variables. Eight patients developed ST-segment changes greater than or equal to 0.1 mV before sternotomy. Preoperative factors could not be used to predict which patients would develop ST-segment changes. In all 38 patients haemodynamic determinants of myocardial oxygen supply and demand remained within an optimal range despite evidence of ischaemia in eight. This syndrome of ECG changes in the absence of tachycardia and hypertension resembles the syndrome of silent ischaemia documented in awake patients. Our findings suggest that myocardial ischaemia may be caused by decreases in coronary blood flow not associated with changes in haemodynamic variables.     

Peri-operative myocardial injury in patients undergoing surgery for critical limb ischaemia.

INTRODUCTION: Although up to a half of patients undergoing abdominal aortic aneurysm (AAA) repair suffer myocardial injury, as indicated by a rise in cardiac troponin I (cTnI), this is infrequently accompanied by a rise in creatine kinase (CK)-MB fraction or electrocardiogram (ECG) changes. This study compares for the first time peri-operative cTnI, CK-MB and ECG changes in patients undergoing surgery for critical lower limb ischaemia (CLI). METHODS: Twenty-nine patients (20 men, median age 75 [range, 57-95] years) were studied prospectively. cTnI, CK/CK-MB ratio and ECG were performed pre-operatively and on post-operative days 1, 2 and 3. RESULTS: Eleven (38%) patients had an elevated cTnI >0.5 ng/ml. Five (17%) patients had an elevated CK-MB fraction >4% and all of these patients had an elevated cTnI. Eleven (38%) patients had ischaemic changes on ECG including seven of 11 (64%) patients with elevated cTnI and all five patients with elevated CK-MB fraction. There was no relationship between pre-operative cardiac status, antiplatelet use or type of anaesthesia and post-operative cTnI rise. Patients with a cTnI rise were younger (p=0.01), and were more likely to have presented with gangrene (p=0.04) and have a longer operation time (p=0.01) than patients who did not demonstrate a cTnI rise. Four patients developed clinically apparent cardiac complications: cardio-pulmonary arrest (n=1), cardiogenic shock (n=1), acute CCF (n=1) and rapid atrial fibrillation (n=1). Survival at 6 months was 26 of 29 (90%) patients. CONCLUSION: These data demonstrate that over a third of patients operated for CLI sustain peri-operative myocardial injury, many of which are not clinically apparent. Pre-operative medical optimisation may improve prognosis in this group of patients.     

Predictors of postoperative myocardial ischaemia The role of intercurrent arterial hypertension and other cardiovascular risk factors

One hundred and eighty-three patients were studied to examine the role of a number of risk factors in the development of silent ischaemia after general anaesthesia for general and vascular surgery. We collected evidence of cardiovascular risk factors using a binary questionnaire. The patients were monitored pre- and postoperatively using a Holter ECG monitor. Usable data were collected on 140 patients. Pre-operative silent myocardial ischaemia was found to be strongly associated with postoperative silent myocardial ischaemia (odds ratio: 10.8, 95% confidence intervals: 3.8–30.7). A history of hypertension, indicated by treatment with antihypertensive drugs, was associated with increased risk (odds ratio: 2.58, 95% confidence intervals: 1.12–5.96). A linear trend was found for risk associated with increasing admission systolic blood pressure (odds ratio: 1.20 for each 10-mmHg increase in systolic pressure, 95% confidence intervals: 1.01–1.42). An association between vascular surgery and postoperative silent myocardial ischaemia was also confirmed (odds ratio: 2.36, 95% confidence intervals: 1.1–5.1).     

Perioperative ST-segment depression and troponin T release. Identification of patients with highest risk for myocardial damage

BACKGROUND: Patients undergoing major vascular surgery are at constant risk of developing perioperative myocardial complications, especially myocardial infarction. The following study was performed to answer the question whether ST segment changes, analysed by Holter monitoring and ST segment analysis, are accompanied by release of cardiac troponin T, a highly specific marker of myocardial damage. METHODS: Twenty patients undergoing elective aortic resection were studied by performing Holter ECG, including ST segment analysis, beginning on the evening before surgery until the third postoperative day. Within this period serum levels of cardiac troponin T were determined at 8 timepoints. RESULTS: A total of 8/20 of the patients (40%) showed significant ST depressions (range -0.17/-0.68 mV), without any clinical symptom, with a median of 9 episodes (range 2-24). In 3 of the 8 patients, each with repetitive periods of ST depression, elevated troponin T levels were found (0.45/0.52/1.69 micrograms/l). No troponin T release nor cardiac events were noticed in the remaining patients. No dependency could be found between troponin T release and the magnitude of ST depression or the number of ST depression episodes. CONCLUSION: Haemodynamic changes, oxygen imbalance and stress during major vascular surgery frequently lead to an ischaemic burden, which is indicated by ST segment changes during ECG ST analysis. Longlasting ST depression reaching an individual critical cut-off limit followed by structural myocardial damage may be verified by elevated levels of cardiac troponin T. Prolonged periods of ST depression should be followed by determination of cardiac troponin T.     

Peri-operative silent myocardial ischaemia in patients undergoing lower limb joint replacement surgery: an indicator of postoperative morbidity or mortality?

One hundred and twenty-seven patients undergoing major lower limb joint replacement surgery were studied to determine the incidence of silent myocardial ischemia and to ascertain any link between pre-operative cardiac risk factors, silent myocardial ischaemia and postoperative morbidity. Patients underwent ambulatory ECG monitoring for 4 days (on the pre-operative night and for 3 days postoperatively). Postoperative cardiorespiratory symptomatology and morbidity was assessed by questionnaire at 3 months. Eighty-seven patients had risk factors for silent myocardial ischaemia; 42 patients (30 with risk factors) had peri-operative silent myocardial ischaemia. The median ischaemic loads (range) were 1.04 (0.32-13.31) min.h-1 pre-operatively and 5.53 (0.26-56.39), 6.69 (0.04-42.71) and 1.23 (0.1-53.74) min.h-1 on postoperative days 1-3, respectively. Risk factors did not predict the occurrence of silent myocardial ischaemia or an increased ischaemic load pre-operatively or overall postoperatively. New symptoms (chest pain, palpitations, breathlessness or fatigue) were associated with both silent myocardial ischaemia and ischaemic load (p < 0.05). Thus cardiac risk factors do not predict the occurrence of silent myocardial ischaemia or adverse outcome. Peri-operative silent myocardial ischaemia was associated with increased postoperative fatigue.     

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)     

Painless myocardial ischemia in chronic hemodialysed patients: a real event?

We investigated the incidence of painless (silent) myocardial ischemia, manifested as S-T segment deviation, by Holter ECG monitoring in patients with chronic renal failure undergoing regular hemodialysis. Forty-five patients underwent Holter ECG monitoring for a continuous 48-hour period covering dialysis and the intermediate period of everyday activity at home. ECG criteria for ischemia were found in 15.5% of patients mainly during and immediately after dialysis with a simultaneous increase of R,S,R + S amplitude. There was no correlation of S-T segment deviation with the existence of cardiac dysfunction and coronary artery disease proved by hemodynamic and angiographic studies. It is concluded that hemodialysis itself seems to play an important role in the genesis of the above ECG findings, possibly by means of serum K and Mg changes.     

Factors associated with post-operative myocardial ischaemia in elderly patients undergoing major non-cardiac surgery

Forty patients (> 65 years) undergoing hip arthroplasty or peripheral vascular surgery both associated with high risk for post-operative myocardial ischaemia were randomized to receive either spinal or general anaesthesia. Ambulatory ECG recording (Holter) until the third post-operative morning, a daily 12-lead ECG and serum creatine kinase and troponine concentraItions were obtained. The number of ischaemic episodes, total duration of ischaemia and ischaemic minutes per hour were noted for each patient peri-operatively. Sixteen of the patients (40%) had post-operative myocardial ischaemia. An intra-operative increase in the plasma concentration of norepinephrine but not epinephrine was detected in the patients who later developed post-operative myocardial ischaemia. The increase in plasma norepinIephrine concentrations correlated with the decrease in core temperature. The type of anaesthesia had no effect on the incidence of myocardial ischaemia during or after surgery. Our results suggests that intra-operatively decreased core temperature and the increase in plasma concentration of norepinephrine probably caused peripheral vasoconstriction leading to latent cardiac dysfunction. These events should be avoided in the patients at risk of post-operative cardiac ischaemia.     

Scintigraphic demonstration of myocardial perfusion and ischaemia associated with coronary artery bypass grafting

OBJECTIVES: To assess if myocardial perfusion scintigraphy (MPS) at rest can be of value in elucidating myocardial perfusion, ischaemia and perioperative myocardial infarction (PMI) associated with coronary artery bypass graft (CABG) surgery. DESIGN: This was a prospective randomized study of patients undergoing elective CABG. Forty-eight patients in the control group underwent serial ECG recordings and measurements of CK-MB and cTnT. Fifty-four patients in the study group were additionally examined with MPS preoperatively and 2-4 days and 6 weeks postoperatively. RESULTS: The study showed a highly significant (p < 0.001) improvement in myocardial radionuclide uptake from preoperatively to 2-4 days postoperatively. Judged from ECG and enzymatic changes, two control patients and one study patient only had PMI and no additional cases of PMI were demonstrated by MPS. CONCLUSION: MPS at rest showed that CABG significantly improved myocardial perfusion, by demonstrating an increase in radionuclide uptake. In diagnosing PMI, we found that MPS provided no additional information beyond cardiac biochemical markers and ECG changes.     

ST segment depression during labor and delivery.

ECG changes suggestive of myocardial ischemia are common during cesarean delivery under regional anesthesia. To determine the time course, duration, and significance of these ECG changes, we monitored 111 parturients with continuous ambulatory ECG (Holter) during and after cesarean delivery. Twenty-two parturients undergoing vaginal delivery were similarly monitored. ST segment depression was present in 25% of patients undergoing cesarean delivery but was not found in those patients delivering vaginally. ST segment elevation was not detected in either group. The incidence of ST segment depression during cesarean delivery was similar with epidural (29%), spinal (17%), and general (18%) anesthesia, occurring most commonly in the 30 min following delivery (P less than 0.001). Transthoracic echocardiographic imaging was performed in 23 patients undergoing cesarean section. Five of the 23 patients had seven episodes of intraoperative ST segment depression. Regional wall motion abnormalities were not present in any patient. A decrease in ejection fraction area greater than 15% from baseline or from previous interval ejection fraction area was present during four episodes of ST change. Three episodes of ST depression were not associated with significant decreases in ejection fraction area. Precordial Doppler monitoring for detection of venous air embolism in 25 patients revealed no association between the occurrence of venous air embolism and ST segment depression. We conclude that although significant myocardial impairment during cesarean delivery does not occur, episodes of ST depression may not all be merely an artifact of parturition.