The Canadian Implantable Defibrillator Study (CIDS) is an on-going randomized multicenter clinical trial that compares implantable cardioverter-defibrillator (ICD) therapy against amiodarone in patients with prior cardiac arrest or hemodynamically unstable ventricular tachycardia. Eligible patients are equally randomized to receive or not receive an ICD as initial management. Those not receiving an ICD receive amiodarone. All patients are seen in follow-up every 6 months. The primary outcome event cluster is arrhythmic death or any other death occurring within 30 days of therapy initiation. Secondary outcomes are all-cause mortality and nonfatal occurrences of ventricular tachycardia or fibrillation. The goal of the study is to recruit 400 patients over 4 years. All patients will be followed to the end of the year. This will result in an 80% chance of detecting a reduction in arrhythmic death of 58% by ICD if such a difference in truth exists. Recruitment began in October 1990 and 184 patients have been enrolled to date.
BACKGROUND: Evidence suggests that physiologic pacing (dual-chamber or atrial) may be superior to single-chamber (ventricular) pacing because it is associated with lower risks of atrial fibrillation, stroke, and death. These benefits have not been evaluated in a large, randomized, controlled trial. METHODS: At 32 Canadian centers, patients without chronic atrial fibrillation who were scheduled for a first implantation of a pacemaker to treat symptomatic bradycardia were eligible for enrollment. We randomly assigned patients to receive either a ventricular pacemaker or a physiologic pacemaker and followed them for an average of three years. The primary outcome was stroke or death due to cardiovascular causes. Secondary outcomes were death from any cause, atrial fibrillation, and hospitalization for heart failure. RESULTS: A total of 1474 patients were randomly assigned to receive a ventricular pacemaker and 1094 to receive a physiologic pacemaker. The annual rate of stroke or death due to cardiovascular causes was 5.5 percent with ventricular pacing, as compared with 4.9 percent with physiologic pacing (reduction in relative risk, 9.4 percent; 95 percent confidence interval, -10.5 to 25.7 percent [the negative value indicates an increase in risk]; P=0.33). The annual rate of atrial fibrillation was significantly lower among the patients in the physiologic-pacing group (5.3 percent) than among those in the ventricular-pacing group (6.6 percent), for a reduction in relative risk of 18.0 percent (95 percent confidence interval, 0.3 to 32.6 percent; P=0.05). The effect on the rate of atrial fibrillation was not apparent until two years after implantation. The observed annual rates of death from all causes and of hospitalization for heart failure were lower among the patients with a physiologic pacemaker than among those with a ventricular pacemaker, but not significantly so (annual rates of death, 6.6 percent with ventricular pacing and 6.3 percent with physiologic pacing; annual rates of hospitalization for heart failure, 3.5 percent and 3.1 percent, respectively). There were significantly more perioperative complications with physiologic pacing than with ventricular pacing (9.0 percent vs. 3.8 percent, P
Comment In: ACP J Club. 2000 Nov-Dec;133(3):89
Comment In: N Engl J Med. 2000 Nov 9;343(19):1417-8; discussion 141811183885
Comment In: N Engl J Med. 2000 Nov 9;343(19):141811183886
Sudden cardiac incapacitation of a driver may lead to the death or serious injury of passengers or bystanders. This has raised public safety concerns and has led to the creation of legislation to protect the public. Some jurisdictions in Canada and the United States have introduced mandatory physician reporting of patients who may be unfit to drive for medical reasons. The impact on motor vehicle accident (MVA)-related morbidity and mortality of mandatory physician reporting for at-risk cardiac patients is unknown.
To determine the impact of mandatory physician reporting legislation (for cardiac patients) in Ontario (population 10.3 million) on MVA-related morbidity and mortality.
Reporting data were obtained from the Ontario Ministry of Transportation. Incidence and prevalence data were taken from Ontario Ministry of Health sources and from the literature (MEDLINE). Data for modelling were taken from the literature (MEDLINE) and from the Canadian Cardiovascular Society's Consensus Conference document on cardiac illness and fitness to drive.
Licence suspension data (correlated with medical illness) were taken directly from government documents. These were then applied to a 'risk of harm' formula used to calculate the risk posed to bystanders and passengers by the suspended patients if they had continued to drive. Canadian licence suspension guidelines were then reviewed in conjunction with cardiac disease incidence and prevalence data to arrive at the number of patients who should have been suspended. Physician compliance with the legislation was then calculated, along with the potential impact on MVA-related morbidity and mortality in the scenario of 100% physician compliance.
All Ontario drivers who had licence suspensions in 1996 for reasons of cardiac disease were included in the analysis.
Nine hundred and ninety-four licences were suspended for cardiac reasons in 1996, compared with an estimated 72,407 that should have been suspended if Canadian guidelines had been followed (1.4%). Less than one death or serious injury was avoided as a result of the legislation (from the 'risk of harm' formula). If all drivers with cardiac illness had been suspended from driving, up to 29.2 such events could potentially have been avoided. However, only 13 of 929 (1.4%) road fatalities in Ontario in 1996 were attributed to a driver with a medical illness.
Mandatory physician reporting of patients with cardiac illness has a negligible impact on MVA-related morbidity and mortality.
This study examined the effect of physiologic pacing on the development of chronic atrial fibrillation (CAF) in the Canadian Trial Of Physiologic Pacing (CTOPP).
The role of physiologic pacing to prevent CAF remains unclear. Small randomized studies have suggested a benefit for patients with sick sinus syndrome. No data from a large randomized trial are available.
The CTOPP randomized patients undergoing first pacemaker implant to ventricular-based or physiologic pacing (AAI or DDD). Patients who were prospectively found to have persistent atrial fibrillation (AF) lasting greater than or equal to one week were defined as having CAF. Kaplan-Meier plots for the development of CAF were compared by log-rank test. The effect of baseline variables on the benefit of physiologic pacing was evaluated by Cox proportional hazards modeling.
Physiologic pacing reduced the development of CAF by 27.1%, from 3.84% per year to 2.8% per year (p = 0.016). Three clinical factors predicted the development of CAF: age > or =74 years (p = 0.057), sinoatrial (SA) node disease (p or =74 years, SA node disease and prior AF predicted the development of CAF. Patients with structurally normal hearts appear to derive greatest benefits.