Population Health Research Institute

Understanding the causes of heart rhythm disorders

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Atrial fibrillation is the most common serious rhythm disorder which affects 1% of the population and seriously increases the risk of stroke.  Sudden death is the leading causes of death in patients with reduced cardiac function.


The Arrhythmia research group at the Population Health Research Institute is a world leader in clinical trials of stroke prevention in atrial fibrillation and trials of cardiac rhythm device therapy.  At the present time, the Arrhythmia group at PHRI is involved in several important areas of research. The Arrhythmia Research Group at the PHRI uses the techniques of randomized clinical trials and large patient registries to explore the causes and consequences of heart rhythm disorder and to identify which treatments reduce important cardiac outcomes. They aim to discover how best to treat patients with serious cardiac rhythm disorders including atrial fibrillation and ventricular arrhythmia.

Key Discoveries

This study was the largest randomized trial of antithrombotic therapy in atrial fibrillation. The results of the study, which have recently been presented, showed that a regimen of clopidogrel plus aspirin is not as effective as warfarin for prevention of vascular events in atrial fibrillation.

DINAMIT (Defibrillators IN Acute Myocardial Infarction Trial)
The DINAMIT trial demonstrated the lack of benefit of implantable defibrillators in patients with recent acute myocardial infarction. This large, multi-national trial defines one of the key limitations of implantable defibrillator therapy as prophylactic therapy and its findings have been incorporated into all major treatment guidelines.

OPTIC (The Optimal Pharmacologic Therapy in Implantable Cardioverter defibrillator patients)
This international study demonstrated the benefits of combining anti-arrhythmic drug therapy with defibrillators for improving the outcomes of patients with life threatening ventricular arrhythmias. It also dispelled a major myth regarding the lack of safety of amiodarone in defibrillator patients.


Main Publications

Connolly SJ, Kerr CR, Gent M, Roberts RS, Yusuf SM, Gillis AM, Sami MH, Talajic M, Tang ASL, Klein  J, Lau C, Newman DM on behalf of the CTOPP investigators. Comparison of the effects of physiologic pacing versus ventricular pacing on cardiovascular death and stroke. N Engl J Med 2000; 342:1385-1391. 

Connolly SJ, Gent M, Roberts RS, Dorian P, Roy D, Sheldon R, Mitchell LB, Green M, Klein G, O'Brien B on behalf of the CIDS Investigators. Canadian Implantable Defibrillator Study (CIDS): A randomized trial of the implantable cardioverter defibrillator against amiodarone. Circulation 2000; 101: 1297- 1302.

Connolly SJ, Sheldon R, Thorpe KE, Roberts RS, Ellenbogen KA, Wilkoff BL, Morillo C, Gent M on behalf of the VPS II investigators. The Second Vasovagal Pacemaker Study (VPSII): A double-blind randomized controlled trial of pacemaker therapy for the prevention of syncope in patients with recurrent severe vasovagal syncope. JAMA 2003; 289:2224- 2229

Hohnloser SH., Kuck, KH, Dorian, Roberts RS, Hampton R, Hatala R, FainE, Gent M, Connolly SJ, on behalf of the DINAMIT Investigators. Prophylactic Use of an Implantable Cardioverter-Defibrillator after Acute Myocardial Infarction. N Engl J Med 2004; 351: 2481-2488.

Connolly SJ, Dorian P, Roberts RS, Gent M, Bailin S, Fain ES, Thorpe K, Champagne J, Talajic M,  Coutu B, Gronefeld GC, Hohnloser SH; Optimal pharmacological Therapy in Cardioverter Defibrillator Patients (OPTIC) Investigators. Comparison of betablockers, amiodarone plus beta-blockers, or sotalol for prevention of shocks from implantable cardioverter defibrillators: the OPTIC Study: a randomized trial. JAMA 2006; 295(2): 165-171.

ACTIVE Writing Group on behalf of the ACTIVE Investigators; Connolly S, Pogue J, Hart R, Pfeffer M, Hohnloser S, Chrolavicius S, Pfeffer M, Hohnloser S, Yusuf S. Clopidogrel plus aspirin versus oral anticoagulation for atrial fibrillation in the Atrial fibrillation Clopidogrel Trial with Irbesartan for prevention of Vascular Events (ACTIVE W): a randomized controlled trial. Lancet 2006. 367(9526): 1903-12.

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