Tapio Hakala

Intravenous Administration of Metoprolol Is More Effective Than Oral Administration in the Prevention of Atrial Fibrillation After Cardiac Surgery

Background— Atrial fibrillation (AF) is the most common arrhythmia to occur after cardiac surgery, with an incidence of 20% to 40%. AF is associated with postoperative complications, including increased risk of stroke and need of additional treatment, as well as prolonged hospital stay and increased costs. It has been shown that prophylactic oral administration of β-blocker therapy reduces the incidence of postoperative AF after cardiac surgery. However, it is possible that absorption of drugs is impaired after cardiopulmonary perfusion associated with cardiac surgery. The purpose of this prospective, controlled, randomized trial was to study compare intravenous and per oral metoprolol administration in the prevention of AF after cardiac surgery. Methods and Results— 240 consecutive patients who were scheduled to undergo their first on-pump coronary artery bypass graft (CABG), aortic valve replacement, or combined aortic valve replacement and CABG were randomized to receive 48-hour infusion of metoprolol or oral metoprolol starting on the first postoperative morning. Patients were excluded if they had contraindications for β-blocker or had to stay >1 day in the intensive care unit. Dosage of metoprolol was adjusted according to heart rate. The dosage was 1 to 3 mg/h in the intravenous group and from 25 mg twice per day to 50 mg 3 times per day in the oral group. The incidence of postoperative AF was significantly lower in the intravenous group than in the oral group (16.8% versus 28.1%, P=0.036). No serious adverse effects were associated with intravenous metoprolol therapy. Conclusions— Our study suggests that intravenous metoprolol is well-tolerated and more effective than oral metoprolol in the prevention of AF after cardiac surgery.

Predicting the risk of atrial fibrillation after coronary artery bypass surgery.

Atrial fibrillation (AF) is the most common arrhythmia, with an incidence of 17–33%, after coronary artery bypass grafting (CABG) and it increases the cost of operative treatment. β‐Blocker therapy reduces markedly the incidence of postoperative AF. The more effective preventive methods, e.g. amiodarone therapy or atrial pacing, are not cost‐effective for all the patients. Thus, identification of patients at high risk of AF after CABG would be helpful. This review summarizes the predictors of postoperative AF and the current methods for risk stratification. In summary, identification of the patients at high risk of postoperative AF remains a challenge. The clinical usefulness of most of the conventional factors, e.g. age or history of AF, is low. Even attempts to build logistic regression models based on the pre‐ and intraoperative variables have failed to provide powerful predictors for postoperative AF after CABG. From the new predictors, the P‐wave duration in signal‐averaged ECG looks promising. Sensitivity and negative predictive value are high, positive predictive value remains low, which limits its usefulness. Contrary, even detailed analysis of standard 12‐lead ECG or measure of heart rate variability has failed to provide useful information for risk stratification. A new method for risk stratification has been developed in our centre. The diagnostic accuracy of high‐rate atrial pacing seems to be sufficient to identify a group of patients to whom prophylactic treatment could be proactively targeted. Further experience is, however, warranted to verify significance of this method in everyday clinical practice.

Early and late outcome after coronary artery bypass surgery in diabetic patients

Objective. To determine the impact of diabetes on outcome after coronary artery bypass surgery. Design. We matched 866 diabetic patients with non-diabetic controls in regards to gender, age, left ventricular ejection fraction, body mass index, presence of unstable angina and history of myocardial infarction, and day of surgery. The 30-d mortality and morbidity were evaluated with univariate analysis and survival and freedom from cardiac death were assessed with the Kaplan–Meier method. Results. Follow-up time was 69±37 months. The 30-d mortality was 2.0% in the diabetic group and 1.0% in the non-diabetic group (p=0.15). Postoperative morbidity did not differ between groups. Cumulative 5- and 10-year survival rates were 89 and 71% in diabetics and 94 and 84% in non-diabetics (p=0.001). During follow-up, there was no difference between groups in regards to repeat revascularization. Conclusions. The 30-d mortality was equally low in diabetic and non-diabetic patients with severe coronary artery disease. However, long-term survival was significantly lower in the diabetic group than in the non-diabetic group.

Prediction of atrial fibrillation after coronary artery bypass grafting by measuring atrial peptide levels and preoperative atrial dimensions

OBJECTIVE We prospectively tested the hypothesis that atrial enlargement and increased level of atrial natriuretic peptide, N-terminal atrial natriuretic peptide and brain natriuretic peptide would predict atrial fibrillation after coronary artery bypass grafting. METHODS Eighty-eight elective coronary artery bypass grafting patients had preoperative echocardiographic assessment. The level of atrial natriuretic peptide, N-terminal atrial natriuretic peptide and brain natriuretic peptide were measured preoperatively. Patients were ECG- monitored during the whole hospital stay. RESULTS Thirty one (35.2%) patients had postoperative atrial fibrillation. In univariate analysis increased age (P=0.003), enlargement of left and right atria (P=0.002 and P=0.004, respectively) and increased level of preoperative atrial natriuretic peptide and N-terminal atrial natriuretic peptide (P=0.016 and P=0.03, respectively) were associated with postoperative atrial fibrillation. There was correlation between the age and level of N-terminal atrial natriuretic peptide (r=0.45 and P<0.001). In multivariate analysis only age and the left atrial enlargement were independent predictors of postoperative atrial fibrillation (P=0.02 and P=0.01). CONCLUSION Left atrial enlargement was independent predictor for postoperative atrial fibrillation. However, atrial peptides were associated with age and did not independently predict postoperative atrial fibrillation. In addition, the wide variation of the peptide levels renders the implementation of this measure in clinical practice superfluous.

Metoprolol Versus Amiodarone in the Prevention of Atrial Fibrillation After Cardiac Surgery: A Randomized Trial

BACKGROUND Current guidelines recommend β-blockers as the first-line preventive treatment of atrial fibrillation (AF) after cardiac surgery. Despite this, 19% of physicians report using amiodarone as first-line prophylaxis of postoperative AF. Data directly comparing the efficacy of these agents in preventing postoperative AF are lacking. OBJECTIVE To determine whether intravenous metoprolol and amiodarone are equally effective in preventing postoperative AF after cardiac surgery. DESIGN Randomized, prospective, equivalence, open-label, multicenter study. (ClinicalTrials.gov registration number: NCT00784316) SETTING 3 cardiac care referral centers in Finland. PATIENTS 316 consecutive patients who were hemodynamically stable and free of mechanical ventilation and AF within 24 hours after cardiac surgery. INTERVENTION Patients were randomly assigned to receive 48-hour infusion of metoprolol, 1 to 3 mg/h, according to heart rate, or amiodarone, 15 mg/kg of body weight daily, with a maximum daily dose of 1000 mg, starting 15 to 21 hours after cardiac surgery. MEASUREMENTS The primary end point was the occurrence of the first AF episode or completion of the 48-hour infusion. RESULTS Atrial fibrillation occurred in 38 of 159 (23.9%) patients in the metoprolol group and 39 of 157 (24.8%) patients in the amiodarone group (P = 0.85). However, the difference (-0.9 percentage point [90% CI, -8.9 to 7.0 percentage points]) does not meet the prespecified equivalence margin of 5 percentage points. The adjusted hazard ratio of the metoprolol group compared with the amiodarone group was 1.09 (95% CI, 0.67 to 1.76). LIMITATIONS Caregivers were not blinded to treatment allocation, and the trial evaluated only stable patients who were not at particularly elevated risk for AF. The withdrawal of preoperative β-blocker therapy may have increased the risk for AF in the amiodarone group. CONCLUSION The occurrence of AF was similar in the metoprolol and amiodarone groups. However, because of the wide range of the CIs, the authors cannot conclude that the 2 treatments were equally effective. PRIMARY FUNDING SOURCE The Finnish Foundation for Cardiovascular Research and the Kuopio University EVO Foundation.

Analysis of Heart Rate Variability does not Identify the Patients at Risk of Atrial Fibrillation after Coronary Artery Bypass Grafting

Objective : Analysis of heart rate variability (HRV) is a non-invasive method for assessing cardiac autonomic regulation. This study was designed to investigate whether preoperative short-term HRV analysis could identify the patients at high risk of atrial fibrillation (AF) after coronary artery bypass grafting (CABG). Design : HRV measurement was performed preoperatively for 92 elective CABG patients. Results : Thirty patients had AF postoperatively while 62 remained in sinus rhythm (SR). Logistic regression analysis identified two independent predictors for AF after CABG: increased age with an odds ratio (OR) 1.06 per year and higher body mass index (BMI) with an OR 1.18 per unit. However, no measured parameters of HRV analysis differed significantly between AF and SR groups. Conclusion : The patients at high risk of AF after CABG cannot be identified by preoperative short-term HRV analysis performed during standardized physiological conditions. Advanced age and higher BMI were independent risk factors of AF after CABG in this study.

Vascular comorbidities and demographics of patients with ruptured abdominal aortic aneurysms

BACKGROUND The results of previous studies reporting the epidemiology of ruptured abdominal aortic aneurysm (RAAA) are highly heterogeneous. Furthermore, although RAAA and the preceding abnormal dilation of the abdominal aorta (AAA) are associated with other cardiovascular comorbidities, the demographic profile of all patients with RAAA has not been thoroughly investigated. OBJECTIVE To document accurately the epidemiology, survival, and demographic data (including vascular comorbidities and previous use of health care services) in RAAA-patients. MATERIAL AND METHODS We conducted a comprehensive retrospective register study of all RAAA patients (operatively treated RAAA patients as well as in- and out-of-hospital nonsurvivors) in a well-defined geographic area during an 11-year period. RESULTS We found 488 RAAA cases in a catchment area of 689,000. The annual incidence of RAAA was 6.5/100,000. Of these patients 43.2% were underwent surgery. Overall mortality was 79.5%, and 27.5% of the population died out-of-hospital. Age was the only independent risk factor affecting survival (P < .0001). The mean age at the time of RAAA was 73.6 years for men and 82.3 years for women. Off all unexpected RAAA patients, 40% had a previous history of cardiovascular disease (most often coronary artery disease: 32%), and 38% had visited a physician within the previous year. CONCLUSION RAAA remains a highly lethal condition with age as the only significant risk factor for mortality. The proportion of women increases strongly with age. A large proportion of patients with unexpected RAAA have history of cardiovascular disease.

Preoperative alterations in correlation properties and complexity of R-R interval dynamics predict the risk of atrial fibrillation after coronary artery bypass grafting in patients with preserved left ventricular function.

Introduction: We evaluated whether there are constant preoperative alterations in nonlinear R–R interval dynamics that associate with the risk of postoperative atrial fibrillation in patients with preserved left ventricular function.

Intraoperative high-rate atrial pacing test as a predictor of atrial fibrillation after coronary artery bypass surgery

BACKGROUND Atrial fibrillation (AF) is a common complication after coronary artery bypass grafting (CABG) operations. The aim of this prospective trial was to test the hypothesis that intraoperative high-rate atrial pacing may induce AF by mimicking rapid atrial tachycardia and can identify the patients at risk for postoperative AF. METHODS; Eighty patients having on-pump CABG without additional procedures were included in the study. After cannulation but before initiation of cardiopulmonary bypass two pacing wires were placed on the lateral surface of the right atrium. The right atrium was paced with the rate of 200 beats per minute for 10 seconds. If the patient was in sinus rhythm after the high-rate pacing, the pacing test was repeated with the rate of 250 and finally 300 beats per minute. RESULTS Postoperatively AF developed in 28 patients (35%). The high-rate atrial pacing test induced AF in 27 patients (33.7%). Of the 28 patients who experienced AF during the postoperative period, 17 patients were inducible in the atrial-pacing test (sensitivity 0.61). Of the 52 patients who did not develop AF postoperatively, 42 patients were not inducible in the atrial-pacing test (specificity of the test was 0.81). Positive and negative predictive values of the test were 0.63 and 0.79, respectively. CONCLUSIONS The intraoperative high-rate atrial pacing test turned out to be a simple, safe, and fast way to identify the patients at risk for AF after CABG. The diagnostic accuracy of this test is sufficient to identify a group of patients to whom prophylactic treatment could be directed.

Rewarming a Patient With Accidental Hypothermia and Cardiac Arrest Using Thoracic Lavage

The optimal treatment for severe accidental hypothermia is cardiopulmonary bypass because this offers the most rapid rate of rewarming. However, cardiopulmonary bypass therapy is not available in every hospital. In these circumstances, rewarming has to be achieved with other methods. We present a patient who was successfully rewarmed with thoracic lavage after he had been found with a core temperature of 21°C and asystole.