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Biomedical subjects

Mario Talajic

Publications and source records attributed to Mario Talajic.

At least 19 recordsLinked to original sources
PubMed2006

Prevention of Syncope Trial (POST): a randomized, placebo-controlled study of metoprolol in the prevention of vasovagal syncope.

BACKGROUND: Previous studies that assessed the effects of beta-blockers in preventing vasovagal syncope provided mixed results. Our goal was to determine whether treatment with metoprolol reduces the risk of syncope in patients with vasovagal syncope. METHODS AND RESULTS: The multicenter Prevention of Syncope Trial (POST) was a randomized, placebo-controlled, double-blind, trial designed to assess the effects of metoprolol in vasovagal syncope over a 1-year treatment period. Two prespecified analyses included the relationships of age and initial tilt-test results to any benefit from metoprolol. All patients had >2 syncopal spells and a positive tilt test. Randomization was stratified according to ages <42 and > or =42 years. Patients received either metoprolol or matching placebo at highest-tolerated doses from 25 to 200 mg daily. The main outcome measure was the first recurrence of syncope. A total of 208 patients (mean age 42+/-18 years) with a median of 9 syncopal spells over a median of 11 years were randomized, 108 to receive metoprolol and 100 to the placebo group. There were 75 patients with > or =1 recurrence of syncope. The likelihood of recurrent syncope was not significantly different between groups. Neither the age of the patient nor the need for isoproterenol to produce a positive tilt test predicted subsequent significant benefit from metoprolol. CONCLUSIONS: Metoprolol was not effective in preventing vasovagal syncope in the study population.

Adrenergic beta-Antagonists↗
PubMed2006

Comparison of beta-blockers, amiodarone plus beta-blockers, or sotalol for prevention of shocks from implantable cardioverter defibrillators: the OPTIC Study: a randomized trial.

CONTEXT: Implantable cardioverter defibrillator (ICD) therapy is effective but is associated with high-voltage shocks that are painful. OBJECTIVE: To determine whether amiodarone plus beta-blocker or sotalol are better than beta-blocker alone for prevention of ICD shocks. DESIGN, SETTING, AND PATIENTS: A randomized controlled trial with blinded adjudication of events of 412 patients from 39 outpatient ICD clinical centers located in Canada, Germany, United States, England, Sweden, and Austria, conducted from January 13, 2001, to September 28, 2004. Patients were eligible if they had received an ICD within 21 days for inducible or spontaneously occurring ventricular tachycardia or fibrillation. INTERVENTION: Patients were randomized to treatment for 1 year with amiodarone plus beta-blocker, sotalol alone, or beta-blocker alone. MAIN OUTCOME MEASURE: Primary outcome was ICD shock for any reason. RESULTS: Shocks occurred in 41 patients (38.5%) assigned to beta-blocker alone, 26 (24.3%) assigned to sotalol, and 12 (10.3%) assigned to amiodarone plus beta-blocker. A reduction in the risk of shock was observed with use of either amiodarone plus beta-blocker or sotalol vs beta-blocker alone (hazard ratio [HR], 0.44; 95% confidence interval [CI], 0.28-0.68; P<.001). Amiodarone plus beta-blocker significantly reduced the risk of shock compared with beta-blocker alone (HR, 0.27; 95% CI, 0.14-0.52; P<.001) and sotalol (HR, 0.43; 95% CI, 0.22-0.85; P = .02). There was a trend for sotalol to reduce shocks compared with beta-blocker alone (HR, 0.61; 95% CI, 0.37-1.01; P = .055). The rates of study drug discontinuation at 1 year were 18.2% for amiodarone, 23.5% for sotalol, and 5.3% for beta-blocker alone. Adverse pulmonary and thyroid events and symptomatic bradycardia were more common among patients randomized to amiodarone. CONCLUSIONS: Despite use of advanced ICD technology and treatment with a beta-blocker, shocks occur commonly in the first year after ICD implant. Amiodarone plus beta-blocker is effective for preventing these shocks and is more effective than sotalol but has an increased risk of drug-related adverse effects.Clinical Trials Registration ClinicalTrials.gov Identifier: NCT00257959.

Adrenergic beta-Antagonists↗
PubMed2006

Concordance between an electroanatomic mapping system and cardiac MRI in arrhythmogenic right ventricular cardiomyopathy.

A 29-year-old man presenting with syncopal ventricular tachycardia was diagnosed with arrhythmogenic right ventricular (RV) cardiomyopathy. Cardiac magnetic resonance imaging (MRI) revealed an unequivocal dyskinetic segment at the basal portion of the RV lateral free wall. Three-dimensional electroanatomic voltage mapping using the EnSite NavX system recorded a low voltage area corresponding to the diseased portion of the right ventricle identified by MRI. This report describes concordance between cardiac MRI and this novel mapping system in arrhythmogenic RV cardiomyopathy.

Adult↗
PubMed2006

Arrhythmias in adult congenital heart disease.

Recent advances in pediatric cardiology and cardiac surgery have allowed a rapidly expanding population of patients with congenital heart disease to thrive well into their adult years. Often after prolonged uneventful clinical courses as children and adolescents, arrhythmias may surface later in life. These arrhythmias are a major source of morbidity. In addition, sudden death is the leading cause of mortality in adult patients with congenital heart disease. This review highlights the various types of brady- and tachyarrhythmias encountered in the more common forms of adult congenital heart disease and explores prognostic implications and therapeutic options.

Adult↗
PubMed2005

Progression to chronic atrial fibrillation after the initial diagnosis of paroxysmal atrial fibrillation: results from the Canadian Registry of Atrial Fibrillation.

BACKGROUND: After its initial diagnosis, atrial fibrillation (AF) may progress from paroxysmal to chronic AF (CAF). The rate of progression and risk factors for progression are not clearly defined. METHODS: The Canadian Registry of Atrial Fibrillation (CARAF) enrolled patients from 6 Canadian cities at the time of their first electrocardiographic diagnosis of AF. Comprehensive clinical and echocardiographic data were collected and patients were followed annually, carefully documenting clinical outcomes, recurrence of paroxysmal AF, and progression to CAF. Baseline clinical, electrocardiographic, and echocardiographic variables were evaluated by univariate Cox proportionate hazards analysis. A stepwise approach was used to model the association between echocardiographic and clinical variables with progression to CAF. RESULTS: A total of 757 patients with a baseline diagnosis of paroxysmal AF were evaluated. Median follow-up was 8.0 years (range 2 days to 11.1 years). The probability of progression to CAF by 1 year was 8.6% and thereafter there was a slow but steady progression to 24.7% by 5 years. By 5 years, the probability of documented recurrence of any AF (chronic or paroxysmal) was 63.2%. Increasing age, significant aortic stenosis or mitral regurgitation, left atrial enlargement, and diagnosis of cardiomyopathy were independently associated with progression to CAF. A more rapid heart rate during AF was associated with decreased risk of progression. CONCLUSIONS: After the initial diagnosis of paroxysmal AF, there is a slow but steady progression to CAF. Baseline echocardiographic variables, age, cardiomyopathy, and heart rate were independently associated with progression to CAF.

Adolescent↗
PubMed2005

Anodal right ventricular capture during left ventricular stimulation in CRT-implantable cardioverter defibrillators.

BACKGROUND: Cardiac resynchronization therapy (CRT) has been shown to improve symptoms of patients with moderate to severe heart failure. Optimal CRT involves biventricular or left ventricular (LV) stimulation alone, atrio-ventricular (AV) delay optimization, and possibly interventricular timing adjustment. Recently, anodal capture of the right ventricle (RV) has been described for patients with CRT-pacemakers. It is unknown whether the same phenomenon exists in CRT systems associated with defibrillators (CRT-ICD). The RV leads used in these systems are different from pacemaker leads: they have a larger diameter and shocking coils, which may affect the occurrence of anodal capture. METHODS: We looked for anodal RV capture during LV stimulation in 11 consecutive patients who received a CRT-ICD system with RV leads with a true bipolar design. Fifteen patients who had RV leads with an integrated design were used as controls. Anodal RV and LV thresholds were determined at pulse width (pw) durations of 0.2, 0.5, and 1.0 ms. RESULTS: RV anodal capture during LV pacing was found in 11/11 patients at some output with true bipolar RV leads versus 0/15 patients with RV leads with an integrated bipolar design. Anodal RV capture threshold was more affected by changes in pw duration than LV capture threshold. In CRT-ICD systems, RV leads with a true bipolar design with the proximal ring also used as the anode for LV pacing are associated with a high incidence of anodal RV capture during LV pacing. This may affect the clinical response to alternative resynchronization methods using single LV stimulation or interventricular delay programming.

Adult↗
PubMed2005

Canadian Cardiovascular Society/Canadian Heart Rhythm Society position paper on implantable cardioverter defibrillator use in Canada.

The Canadian Heart Rhythm Society in conjunction with the Canadian Cardiovascular Society is committed to the promotion of evidence-based practice in Canada. Since the last Canadian guidelines on the management of sudden cardiac death were published in 2000, several well-conducted clinical trials evaluating the implantable cardioverter defibrillator have been completed and published. The Canadian Cardiovascular Society Council has granted permission to review and update guidelines for the indications for implantable cardioverter defibrillators. Furthermore, data are emerging on the potential benefits of biventricular pacing therapy (cardiac resynchronization) for heart failure; recommendations for the use of this therapy have been included in the present paper. Ethical considerations and the economic implications of these recommendations are also included. Canada's heart rhythm specialists, represented by the Canadian Heart Rhythm Society, have been joined by two heart failure specialists, a medical ethicist and an economist, to develop the present position paper. Members of the Canadian Heart Rhythm Society participated in the discussion of these recommendations in open forum meetings and by electronic communication.

Death, Sudden, Cardiac↗
PubMed2005

Implanted cardioverter defibrillators for the prevention of sudden death.

Implantable cardioverter defibrillators (ICDs) are effective in preventing sudden death from ventricular arrhythmias. Recent clinical trials have demonstrated reductions in all-cause mortality in ICD-treated patients, especially those with severe left ventricular dysfunction. However, selecting appropriate patients for ICD implantation, especially for the primary prophylaxis of all-cause death, is a challenge. Patients with recent myocardial infarction (less than 40 days) or those that have just undergone coronary artery bypass graft surgery do not benefit from ICD implantation. On average, annual death rates are reduced by 1.5% to 3.0%, but the risk of death in an individual patient is hard to quantify. Poor left ventricular function is the best predictor of both mortality risk and ICD benefit. Other risk predictors need to be identified.

Death, Sudden, Cardiac↗
PubMed2005

Atrial fibrillation: basic and clinical research at the Montreal Heart Institute.

The present article reviews pertinent contributions from the Montreal Heart Institute, Montreal, Quebec, to the understanding of the mechanisms and treatment of atrial fibrillation. The article discusses the usefulness of anticoagulant therapy, antiarrhythmic drug therapy for sinus rhythm maintenance, the electrophysiological basis of atrial fibrillation and the investigation of new energy sources for catheter ablation. Future directions at the Montreal Heart Institute are also briefly addressed.

Academies and Institutes↗
PubMed2005

Drug therapy for termination of atrial fibrillation and maintenance of sinus rhythm.

Antiarrhythmic drug therapy to maintain sinus rhythm has not been demonstrated in randomized clinical trials to improve prognosis or prevent thromboembolic complications in patients with atrial fibrillation (AF). Therefore, drug therapy to restore and maintain sinus rhythm should be limited to those patients who have a greater symptomatic burden of AF. Patients with AF may be completely unaware of their arrhythmia or may present with palpitations, poor exercise tolerance or symptoms of congestive heart failure. In general, younger patients with paroxysmal arrhythmia and patients with decreased left ventricular compliance tend to be more symptomatic. The present article outlines the mechanisms of action of antiarrhythmic drugs in AF. Drugs that are recommended and frequently used to convert AF and maintain sinus rhythm are reviewed, and the toxicity of antiarrhythmic drug toxicity is discussed.

Anti-Arrhythmia Agents↗
PubMed2005

Management of atrial fibrillation in the emergency department and following acute myocardial infarction.

Atrial fibrillation (AF) is the most common arrhythmia managed by emergency physicians and there is increasing evidence that selected patients with acute AF can be safely managed in the emergency department without the need for hospital admission. The principles of management are identification and treatment of precipitating or underlying causes, hemodynamic stabilization/rate control, reduction of thromboembolism risk and the conversion/maintenance of sinus rhythm. A strategy of rate or rhythm control should be chosen based on the patient's clinical status, the duration of AF, the experience of the treating physician and the status of anticoagulation. Before either electric or pharmacological cardioversion, anticoagulation should be considered. Most patients should be given heparin or low molecular weight heparin while preparing for cardioversion. All patients should be considered for long-term anticoagulation based on their thromboembolic risk and bleeding risk from antithrombotic therapy. Following restoration of sinus rhythm, a decision regarding the use of antiarrhyhmic drugs should be made based on the estimated frequency of recurrence and degree of symptoms. In the setting of acute myocardial infarction, beta-blockers should be administered whenever possible. If beta-blockers are contraindicated, the rate can be slowed with digoxin or amiodarone. Cardioversion should be performed if the patient is hemodynamically unstable. Class IC antiarrhythmic drugs should not be administered in this setting.

Atrial Fibrillation↗
PubMed2004

Prognostic significance of newly acquired bundle branch block after aortic valve replacement.

There is controversy concerning the prognostic significance of conduction delays that occur after aortic valve replacement (AVR). We retrospectively reviewed 389 consecutive patients who underwent AVR at our institution between April 1995 and March 1997. Adverse events were defined as the occurrence of complete atrioventricular block, syncope, or sudden cardiac death. Among 262 patients included in our database, 31 (11.8%) had a preoperative bundle branch block (BBB) and 41 (15.6%) developed new BBB postoperatively. At a mean follow-up of 54 months, the event rate was 1.6% (3 of 190) in patients with no BBB versus 17% (7 of 41, p = 0.0004) in patients who developed new BBB after surgery. There were 4 events (4 of 15 = 26.6%, p = 0.0006) in patients who developed new left BBB and 3 (3 of 26, 11.5%, p = 0.02) in those who developed new right BBB after AVR. There was also an increased adverse event rate in patients who had preoperative BBB (3 of 31, 9.7%, p = 0.037). By multivariate analysis, a new and persistent BBB acquired after surgery was the only independent predictor of adverse events during follow-up (odds ratio 8.85, p = 0.0004). The highest event rate was seen in patients who developed new left BBB and left axis deviation after surgery. Most events occurred during the first year of follow-up. A new and persistent BBB acquired after AVR is associated with an increased adverse event rate. This finding suggests that early prophylactic pacemaker implantation should be considered in these patients.

Aged↗
PubMed2004

Beta-radiation for the creation of linear lesions in the canine atrium.

BACKGROUND: Creating linear lesions is important for the treatment of arrhythmias such as atrial flutter and fibrillation. Making these lesions with standard radiofrequency catheters can be difficult and may result in charring and thrombosis. The purpose of this study was to evaluate beta-radiation as a novel energy source for creating linear myocardial lesions. METHODS AND RESULTS: Eight dogs with intact conduction across the cavotricuspid isthmus were studied. The isthmus was irradiated (25 to 50 Gy) with strontium/yttrium-90 delivered via a deflectable 7F catheter (Novoste Corporation). There were no immediate effects, but bidirectional conduction block developed during follow-up studies in 7 of 8 dogs. The dog without conduction block received 25 Gy. After the animals were euthanized, histology revealed transmural, linear areas of fibrosis without any thrombus. CONCLUSIONS: Beta-radiation can safely and effectively create linear lesions that are contiguous and nonthrombogenic. This energy source may become an interesting adjunct to radiofrequency for the treatment of atrial flutter and fibrillation.

Animals↗
PubMed2004

Prognostic differences between atrial fibrillation and atrial flutter.

This report presents the outcome of a cohort of 94 patients with atrial fibrillation from the Canadian Registry of Atrial Fibrillation, in which we paid particular attention to the probability of stroke and death. We also evaluated warfarin use over time and compared left atrial dimensions in patients with atrial flutter with those with atrial fibrillation.

Aged↗
PubMed2004

Canadian Trial of Physiological Pacing: Effects of physiological pacing during long-term follow-up.

BACKGROUND: The Canadian Trial of Physiological Pacing (CTOPP) reported that the risk of stroke or cardiovascular death was similar between patients receiving ventricular versus physiological pacemakers at the end of the original follow-up period of 3 years. However, the occurrence of atrial fibrillation was significantly less frequent with physiological pacemakers. To assess a potential delayed benefit of physiological pacing, follow-up of patients in this study was extended to 6 years. METHODS AND RESULTS: A total of 1474 patients requiring a pacemaker for symptomatic bradycardia were randomized to receive ventricular and 1094 to physiological pacemakers. The primary outcome was stroke or cardiovascular death. The study was completed in July 1998, and follow-up was extended to July 2001. At a mean follow-up of 6.4 years, there was no difference between treatment groups in the primary outcome of cardiovascular death or stroke. There was no significant difference in total mortality or stroke between groups. There was a significantly lower rate of development of atrial fibrillation in the physiological group, with a relative risk reduction of 20.1% (CI, 5.4 to 32.5; P=0.009). CONCLUSIONS: The CTOPP extended study does not show a difference in cardiovascular death or stroke, or in total mortality, or in stroke between patients implanted with ventricular or physiological pacemakers over a mean follow-up of >6 years. However, there is a persistent significant reduction in the development of atrial fibrillation with physiological pacing.

Atrial Fibrillation↗
PubMed2004

The association of left atrial size and occurrence of atrial fibrillation: a prospective cohort study from the Canadian Registry of Atrial Fibrillation.

BACKGROUND: The effect of left atrial (LA) dimension on the recurrence of atrial fibrillation (AF) has been examined in small studies. We evaluated the effect of LA dimension on the occurrence of AF using 2- and 4-year echocardiographic data in a large cohort of patients with new onset AF. METHODS: The Canadian Registry of AF (CARAF) enrolled subjects with AF at the first electrocardiographically confirmed diagnosis. Patients were classified at 2 and 4 years as no recurrent AF (No RAF), paroxysmal AF (PAF), or chronic AF (CAF) based on clinical symptoms and electrocardiographic documentation. The association between baseline, 2-, and 4-year LA dimensions with occurrence of AF as determined by echocardiography was evaluated using a multivariate analysis. RESULTS: The No RAF group (n = 176) had a significantly smaller LA dimension (36.9 +/- 6.8 mm) at baseline compared to the CAF group (n = 227) (42.8 +/- 7.5 mm, P <.0001). The No RAF and PAF (n = 153) groups did not have a significant change in LA dimension at 2 or 4 years. Only those with CAF had a significant increase in LA dimension at 2 and 4 years, +1.39 mm (95% CI 0.01-2.8) and +3.48 mm (95% CI 1.8-5.2), respectively. CONCLUSIONS: A larger baseline LA dimension is associated with progression to CAF. Patients with no or paroxysmal recurrence had no change in LA dimension over a 4-year period. These findings have implications in tailoring modes of therapy in patients with AF.

Aged↗
PubMed2004

Thromboembolic events occur despite sinus rhythm maintenance in patients treated for atrial fibrillation: The Canadian Trial of Atrial Fibrillation experience.

BACKGROUND: Anticoagulation reduces the risk of stroke in patients with atrial fibrillation. It is not clear whether patients who revert and are maintained in sinus rhythm should continue to receive warfarin. The recommendation is to anticoagulate these patients for a minimum of four weeks after cardioversion. Whether warfarin should be maintained for a longer period of time is unknown. METHODS AND RESULTS: To address this question, data from the Canadian Trial of Atrial Fibrillation were reviewed. Among the 403 patients, 81.9% had at least one risk factor for stroke, of whom only 60% were on warfarin. Nine thromboembolic events occurred in nine patients (2.2%): all had at least one risk factor for stroke. Six events occurred in patients who were either not anticoagulated (n=4) or for whom the international normalization ratio was subtherapeutic (n=2). Eight of the nine patients were in sinus rhythm at the last follow-up visit before and at the time of evaluation of the thromboembolic event. CONCLUSIONS: Anticoagulants are underused in atrial fibrillation patients at risk of stroke. Thromboembolic events are most often associated with suboptimal levels of anticoagulation and they occur despite the appearance of sinus rhythm maintenance.

Aged↗