Intra-institutional prediction of outcome after cardiac surgery: comparison between a locally derived model and the EuroSCORE.

OBJECTIVE: To construct models for predicting mortality, morbidity and length of intensive care unit (ICU) stay after cardiac surgery and to compare the performance of these models with that of the EuroSCORE in two independent validation databases. METHODS: Clinical data on 4592 cardiac surgery patients operated between 1992 and 1996 were retrospectively collected. In order to derive predictive models and to validate them, the patient population was randomly divided into a derivation database (n=3061) and a validation database (n=1531). Variables that were significant in univariate analyses were entered into a backward stepwise logistic regression model. The outcome was defined as mortality within 30 days after surgery, predefined morbidity, and the length of ICU stay lasting >2 days. In addition to the retrospective database, the models were validated also in a prospectively collected database of cardiac surgical patients operated in 1998-1999 (n=821). The EuroSCORE was tested in two validation databases, i.e. the retrospective and prospective one. Hosmer-Lemeshow goodness-of-fit was used to study the calibration of the predictive models. Area under the receiver operating characteristic (ROC) curve was used to study the discrimination ability of the models. RESULTS: The overall mortality in the retrospective and the prospective data was 2 and 1%, and morbidity 22 and 18%, respectively. The created predictive models fitted well in the validation databases. Our models and the EuroSCORE were equally good in discriminating patients. Thus, in the prospective validation database, the mean areas under the ROC curve for our models and for the EuroSCORE were similar, i.e. 0.84 and 0.77 for mortality, 0.74 and 0.74 for morbidity, and 0.81 and 0.79 for the length of intensive care unit stay lasting for 2 days or more, respectively. CONCLUSIONS: Our models and the EuroSCORE were equally good in discriminating the patients in respect to outcome. However, our model provided also well calibrated estimation of the probability of prolonged ICU stay for each patient. As was originally suggested, the EuroSCORE may be an appropriate tool in categorizing cardiac surgical patients into various subgroups in interinstitutional comparisons. Our models may have additive value especially in resource allocation and quality assurance purposes for local use.

Conduction defects after coronary artery bypass grafting--a disappearing problem?

BACKGROUND AND AIMS: To evaluate the incidence of conduction defects (CDs) following coronary artery bypass grafting (CABG) in three different patient populations, to assess the etiologic factors associated with CDs, and to find out their effect on immediate postoperative outcome of the patient. MATERIAL AND METHODS: Three patient populations were prospectively studied: cohort A consisted of 180 CABG-patients operated between 1990-91, cohort B of 100 patients operated during the year 1993 and cohort C of 118 patients operated from April 1997 to June 1997. Cold crystalloid cardioplegia was used throughout the study years. In the first cohort A, two separate cavae were cannulated and clamped, venting through the right upper pulmonary vein was used, iced cold saline was used in pericardium, and cardioplegia was given until a myocardial temperature of 10-15 degrees of Celcius was attained. In the two later cohorts, two-stage venous cannula and aortic root venting were used and cardioplegia was given only until the activity of the myocardium stopped. Proximal anastomoses were performed after aortic declamping in cohort A, and during aortic occlusion in the two later cohorts. RESULTS: The incidence of permanent CDs in cohort A was 36%, in cohort B 5% and in cohort C 1%. Permanent atrioventricular (AV-) and left-sided blocks disappeared first. Left main coronary artery stenosis and low myocardial temperatures were associated with CDs. Patients with permanent CDs had more often low cardiac output after the operation, their values of cardiac enzymes were higher, and they had more often postoperative infarction than patients without CDs. CONCLUSIONS: The disappearance of all long lasting AV- and left-sided blocks simultaneously with decreasing plasma levels of cardiac enzymes is evidence that protection of both conduction tissue and myocardium had considerably improved in the two later cohorts. Giving cardioplegia in smaller amounts and more often at the same time when raising the general temperature during perfusion were the main reasons for the disappearance of postoperative CDs.

Angiographic predictors of graft patency and disease progression after coronary artery bypass grafting with arterial and venous grafts.

BACKGROUND: There are few data about angiographic determinants of functional graft patency and native artery disease progression after coronary artery bypass grafting operation with arterial grafts compared with venous grafts. METHODS: Baseline and follow-up coronary angiograms at a mean of 2 years after operation in 91 patients with 194 arterial and 204 venous graft anastomoses were analyzed. RESULTS: Ninety-two percent of the arterial and 87% of the venous graft anastomoses were patent at follow-up angiography (p = 0.05, odds ratio = 2.63). Unlike that of arterial grafts, the patency rate of venous graft anastomoses correlated negatively with decreasing severity of the bypassed lesion. In contrast to venous grafts, in which angiographic graft function was basically dichotomous (fully patent or occluded), compromised flow of the arterial graft anastomoses was registered in 12%. Progression of the disease was more common in segments bypassed with venous grafts than with arterial grafts (p = 0.001, odds ratio = 2.03). CONCLUSIONS: Angiographic determinants of functional graft patency and progression of occlusive changes in the bypassed artery segments are different for arterial and venous grafts.

Significance of coronary artery bypass grafting-associated conduction defects.

The incidence of permanent atrioventricular conduction defects (CDs) caused by coronary artery bypass grafting (CABG) varies from 5% to 43% if cold crystalloid or blood cardioplegia is used for myocardial preservation. However, the long-term effects of CDs on clinical outcome are not well known. In this study we compared the outcome of 52 patients with permanent CABG-associated CDs (CD+) to 47 patients without CDs (CD-) after a 3-year follow-up. Recovery of CDs was found in 2 patients during the follow-up. There were no significant differences between groups in late mortality, cardiac or neurologic events, or capability to work. Although exercise capacity was similar, the exercise-limiting symptom more often was chest pain or dyspnea in the CD+ group than in the CD- group (p = 0.001). Left ventricular ejection fractions at rest and at 50-W workload level were lower in the CD+ group (p = 0.03 to 0.05). In addition, CD+ patients with left bundle branch block or cardiac pacemaker had significantly lower ejection fraction at maximal workload level than patients without CDs (p = 0.03). No significant differences were observed between the groups in the potential risk for ventricular arrhythmias according to signal-averaged electrocardiograms. In conclusion, the clinical outcome of patients with CDs after CABG operations is almost comparable to those without CDs during a 3-year follow-up. However, patients with CDs have lower left ventricular systolic function and more often have chest pain or dyspnea as the exercise-limiting symptom than patients without CDs.

Predictors of conduction disturbances after coronary bypass grafting.

One hundred sixty-nine patients undergoing coronary artery bypass grafting were included in a prospective study to test the effect of coronary pathology on conduction disturbances (CD). At the same time, several other proposed preoperative and intraoperative predictors of CD were collected. From the angiograms, the vascularization of the interventricular septum was classified according to Mosseri and colleagues. Ninety-four patients (56%) had type II coronary pathology, which does not allow full revascularization of the interventricular septum. The tested classification did correlate with the state of coronary disease, resulting in more left main coronary stenoses and more numerous peripheral anastomoses in type II patients. However, there was no correlation between the classification and CD. Patients with permanent CD (34%) had more left main coronary artery stenoses (29% versus 14%; p = 0.03). Their measured maximal myocardial temperatures were lower in all three myocardial regions measured (p = 0.01 to 0.07), and their creatine kinase MB fraction values on the day of operation were also higher (92 versus 70 IU; p = 0.002). In multivariate logistic regression analysis, the maximal temperature of the left circumflex artery region and the presence of left main coronary artery stenoses were the only independent predictors of permanent CD. We conclude that excessively low myocardial temperatures during cardioplegia may cause CD.

Reversed left internal mammary artery graft for coronary bypass. Evaluation of function with digital subtraction angiography and radionuclide imaging.

Reversed left internal mammary artery grafting with retrograde flow to the left anterior descending coronary branch was used in five of 500 consecutive bypass operations. The indications were significant stenosis in the left subclavian artery (3 patients) or the proximal left internal mammary artery (1) and proximal damage to the left internal mammary artery during dissection from the thoracic wall (1). The postoperative clinical course was smooth in all five patients, with no evidence of myocardial ischemia. In follow-up averaging 14 months four patients were asymptomatic. The reversed internal mammary artery graft was visualized with digital subtraction angiography in four cases. Radionuclide imaging during exercise confirmed graft patency in all but the symptomatic patient, who was found to have an area of reversible ischemia anteriorly in the left ventricle.

Clinical characteristics and coronary anatomy in refractory unstable angina pectoris leading to coronary artery bypass grafting. The Kuopio experience.

One hundred patients with high-risk unstable and medication-resistant angina pectoris underwent coronary artery by-pass grafting. In 35 cases the angina was of early post-infarction type, in 60 it was progressive after previous stability and in five it was of recent onset. All had abnormal ECG in association with anginal attacks (ST depression in 76, ST elevation in 5, T-wave inversion in 15 and left bundle branch block in 4). The left main coronary artery was stenosed in 33 patients, and the respective figures for three-vessel, two-vessel and one-vessel disease were 53, 9 and 5. The average number of inserted peripheral grafts/patient was 4.6. The perioperative mortality rate was 1%. Seven patients had confirmed or probable perioperative myocardial infarction and two had late infarction during the hospital stay, but none had angina pectoris on discharge. Of 60 patients re-examined after 1 year, 47 were angina-free. Five had NYHA class III angina, but all were improved. In refractory unstable angina pectoris there is severe coronary artery involvement, but bypass grafting can give good results.

Changes occurring in the postinfarction ECG in relation to age, sex, and previous myocardial infarction.

Minnesota codes (MC), expressing Q-QS, ST segment, and T wave abnormalities in ECGs taken during the acute event and at a 1-year follow-up were studied in 256 survivors of myocardial infarction (MI). On the 1-year ECGs large Q waves (MC 1.1) were more common in patients with a history of previous MI than in those with a first MI. Regression of Q-QS, ST segment, and T wave changes occurred more extensively in first MIs, whereas progression of MC Q-QS and ST segment signs tended to be common in those with recurrent MI. On the acute ECGs large Q waves were more frequent in men (52%) than in women (36%), but ST segment depression of 1 mm or more (MC 4.1) was predominant in women in both the acute and 1-year ECGs. This ECG sign was related to the advanced age of the patients. There was no significant sex difference in the regression of the Q-QS signs, but the disappearance of ST and T wave changes occurred more extensively in men. The ECG returned to normal in 12% of men with a first MI but only infrequently in women and men with recurrent MI.

Enalapril in chronic heart failure, a double-blind placebo-controlled study.

The efficacy of enalapril, a new angiotensin-converting enzyme inhibitor, was investigated in a double-blind placebo-controlled study in 24 patients with chronic heart failure. The patients belonging to NYHA functional class II-IV and treated with digoxin and diuretics were randomized to enalapril (12 patients) or placebo (12 patients) treatment for a 12-week period. Assessments were carried out at baseline and at 4 and 12 weeks during the treatment period. Complete data could be obtained on 10 patients receiving enalapril and on 11 patients receiving placebo. NYHA functional class improved by at least one class in 6 of 10 patients in the enalapril group, but only in 1 of 11 patients in the placebo group (chi 2 = 6.54; p less than 0.05). Duration of bicycle ergometer exercise increased significantly in the enalapril group from 8.8 +/- 3.4 to 11.3 +/- 4.2 (4 weeks) and to 11.2 +/- 3.6 min (12 weeks; p less than 0.05 for both), whereas it remained unchanged in the placebo group. Left ventricular ejection fraction by radionuclide ventriculography in the enalapril group increased significantly (baseline: 33.5 +/- 19.9%, 4 weeks: 40.0 +/- 20.0% (p less than 0.001), 12 weeks: 39.6 +/- 20.1% (p less than 0.01], whereas in the placebo group it did not change significantly from the baseline of 48.8 +/- 16.7%. The results indicate that enalapril induces a sustained relief of symptoms and improves exercise capacity in patients with heart failure. This subjective improvement appears to be accompanied by an increase in ejection fraction.

Sotalol-induced prolongation of the Q-T interval and attacks of unconsciousness.

A case history is reported of a patient who had several episodes of unconsciousness (because of ventricular extrasystole) while on antiarrhythmic and antihypertensive therapy consisting of quinidine (200 mg b. i. d.), sotalol (80 mg b. i. d.) and hydrochlorothiazide (50 mg g. d.). The syncopal attacks continued after discontinuation of quinidine but ended when sotalol was replaced by metoprolol and later on by verapamil. Marked prolongation of the previously normal Q-Tc interval (up to 0.71 s) was observed during the therapy with sotalol alone or combined with quinidine. The syncopal attacks were preceded by feeling of cardiac arrhythmia and they were most likely caused by torsade de pointes tachycardia. The prolongation of the Q-Tc interval by sotalol alone or combined with quinidine was obviously related to the tendency to cardiac arrhythmia and consequent episodes of unconsciousness.

Antiarrhythmic efficacy of combined intravenous and oral mexiletine in acute myocardial infarction. A double blind placebo-controlled study.

The antiarrhythmic efficacy of mexiletine in acute myocardial infarction (AMI) was studied in 99 patients randomized to mexiletine or placebo treatment. The loading dose was 250 mg i.v. and 400 mg orally followed by 200 mg orally 2 h later, and thereafter 200 mg t.i.d. up to 42 h. Arrhythmias occurring during 48 h were analysed from continuous electrocardiographic recordings. AMI was verified in 35 of 50 mexiletine patients and in 38 of 49 placebo patients. No deaths or instances of ventricular fibrillation occurred in the AMI patients. The number of patients who had any event of accelerated idioventricular rhythm (AIVR; P less than 0.05) runs of ventricular premature beats (VPBs; P less than 0.01), ventricular tachycardia (P less than 0.01) and Ron T beats (P less than 0.05) was smaller in the mexiletine group than in the placebo group. The number of all VPBs (P less than 0.05), hours with occurrence of AIVR (P less than 0.05), runs (P less than 0.01) and Ron T beats (P less than 0.05) was smaller in the mexiletine than in the placebo group. Serum levels of mexiletine tended to be low throughout the study. The half-life of the elimination was 13.7 +/- 7.2 h (means +/- S.D.). Adverse effects were infrequent, and the treatment was well-tolerated. Combined iv. and oral mexiletine prophylaxis significantly suppressed repetitive ventricular tachyarrhythmias and Ron T beats. However, no clinical benefit from mexiletine treatment could be shown in a coronary care unit with a low frequency of primary ventricular fibrillation.

In-hospital death from ischaemic heart disease.

The clinical course and the clinical and pathological factors were studied in a series of 112 in-hospital patients who died of acute myocardial infarction. A necropsy was performed in 101 cases. 44% of the victims were concluded to have been past the possibility of recovery at the time of admission, as the treatment of early ventricular fibrillation or asystole did not lead to a satisfactory result, or as a refractory heart failure or shock dominated from admission to death. Resuscitations due to early ventricular fibrillation were performed in the emergency department mainly on patients living near the hospital. On the other hand, an early heart failure was more frequent among those whose transit distance was over 15 km. Prior use of beta-receptor blockers seemed to protect against early complications. The cardiac functions of the remaining patients were normal or could be normalized at the beginning of the hospitalization. The great majority of them were later lost as a result of extensive damage of the myocardium leading to a refractory heart failure and some due to a rupture caused by infarction (8%) or due to embolic complications (10%). Only 11 patients (10%) succumbed to late ventricular fibrillation without heart failure, rupture, or embolism. The cardiac disease revealed by the necropsy was more severe in patients with a refractory heart failure than in those who died of late ventricular fibrillation or rupture without a preceding heart failure. Various arrhythmias were frequent during the hospitalization. 74% of the dysrhythmias were preceded or followed by symptoms of a heart failure.

Early pronounced ST segment depression with marked J point decline heralding acute lethal clinical myocardial infarction: Necropsy-electrocardiographic correlative study.

Marked ST segment depression (greater than or equal to 2 mm J point decline with horizontal or downsloping ST) was correlated with necropsy findings in 105 cases. Acute myocardial infarction (AMI) was most frequently (70%) responsible for development of the abnormal ST pattern, thereby indicating the diagnosis and severe prognosis of the AMI. In 23% of patients the ST segment depression pattern was associated with chronic heart disease without AMI; all were severely ill with 92% receiving digitalis. Sudden worsening of the basic heart disease or circulatory shock were frequently found to coincide with the abnormal ST pattern; necropsy revealed extensive old MI or myocardial fibrosis in these patients. Marked ST segment depression was also found in five patients without underlying heart disease at autopsy; an acute cerebral accident or circulatory shock was considered to have produced the abnormal ST segment pattern.

Changes in the QRS complex and ST segment in transmural and subendocardial myocardial infarctions. A clinicopathologic study.

The QRS complex and ST segment in the ECGs of 80 patients who died of an acute myocardial infarction (MI) were studied in relation to the extent of the MI (subendocardial vs. transmural). Changes in the QRS complex developed in nine out of the 15 cases with an acute subendocardial MI. Five of these cases fulfilled the conventional QRS criteria for a myocardial infarction. A definite ST segment depression (a J point depression of 2 mm. or more in at least one lead, and a horizontal or downward sloping ST segment with a minimum duration of 0.08 sec.) occurred most frequently in connection with a circumferential subendocardial MI (88 per cent), but it was also found in a regional subendocardial (43 per cent) and transmural MI (43 per cent). In 17 per cent of the cases with a transmural MI, this was the only ECG abnormality. It is concluded that cases with a subendocardial MI cannot always be distinguished from transmural MI on the basis of the presence or absence of the QRS changes, and that an ST segment depression, as defined in this study, can give additional information in the evaluation of an acute phase of an MI.