Treatment of atrial fibrillation with a dual defibrillator in heart failure patients (TRADE HF): protocol for a randomized clinical trial

Electrical treatment of atrial arrhythmias in heart failure patients implanted with a dual defibrillator CRT device. Results from the TRADE-HF study

BACKGROUND

Ventricular and atrial arrhythmias commonly occur in heart failure patients and are a significant source of symptoms, morbidity and mortality. Some specific generators referred to as dual defibrillators, Dual CRT-Ds, have the ability to treat atrial and ventricular arrhythmias. TRADE-HF is a prospective two-arm randomized study aimed at assessing the benefits of complete automatic management of atrial arrhythmias in patients implanted with a dual CRT-D.

METHODS

Primary objective of the TRADE-HF study was to document reduction of unplanned hospital admission for cardiac reasons or death for cardiovascular causes or progression to permanent AF, by comparing fully-automatic device driven therapy for atrial tachycardia or fibrillation (AT/AF) to an in-hospital approach for treatment of symptomatic AT/AF. Randomized Patients were followed every 6months for 3years to assess the primary objective.

RESULTS

Four-hundred-twenty patients have been enrolled in the study. At the end of the study 30 subjects died for cardiovascular causes, 60 had at least one hospitalization for cardiovascular causes and 14 developed permanent AF. Eighty-seven patients experienced a composite event. Hazard Ratio for device-managed automatic therapy arm compared to traditional was 0.987 (95% CI: 0.684-1.503; p=0.951). The primary endpoint analysis resulted in no difference between the device managed and in-hospital treatment arm.

CONCLUSION

The TRADE-HF study failed to demonstrate a reduction in the composite of unplanned hospitalizations for cardiovascular causes or death for cardiovascular causes or progression to permanent AF using automatic atrial therapy compared to a traditional approach including hospitalization for symptomatic episodes and/or in-hospital treatment of AT/AF.

Hybrid therapy in the management of atrial fibrillation

Atrial fibrillation is the most common sustained arrhythmia. Because of the sub-optimal outcomes and associated risks of medical therapy as well as the recent advances in non-pharmacologic strategies, a multitude of combined (hybrid) algorithms have been introduced that improve efficacy of standalone therapies while maintaining a high safety profile. Antiarrhythmic administration enhances success rate of electrical cardioversion. Catheter ablation of antiarrhythmic drug-induced typical atrial flutter may prevent recurrent atrial fibrillation. Through simple ablation in the right atrium, suppression of atrial fibrillation may be achieved in patients with previously ineffective antiarrhythmic therapy. Efficacy of complex catheter ablation in the left atrium is improved with antiarrhythmic drugs. Catheter ablation followed by permanent pacemaker implantation is an effective and safe treatment option for selected patients. Additional strategies include pacing therapies such as atrial pacing with permanent pacemakers, preventive pacing algorithms, and/or implantable dual-chamber defibrillators are available. Modern hybrid strategies combining both epicardial and endocardial approaches in order to create a complex set of radiofrequency lesions in the left atrium have demonstrated a high rate of success and warrant further research. Hybrid therapy for atrial fibrillation reviews history of development of non-pharmacological treatment strategies and outlines avenues of ongoing research in this field.

Is An Atrial Defibrillator Still An Option In Treating Patients With Atrial Fibrillation?

Atrial fibrillation (AF) is a common disorder associated with significant morbidities and presents several challenges for the control of symptoms and prevention of long-term implications. Atrial defibrillators (ADs), used for rhythm control in patients with symptoms refractory to medical therapy, can detect recurrences of the arrhythmia, allow prompt patient-directed treatment, and have the potential to reduce hospitalizations and improve quality of life. The efficacy of this form of therapy is highest in patients with paroxysmal AF, and with the use of a coronary sinus shocking lead. While R-wave synchronized shocks are a prerequisite for a safe use, the procedure is well tolerated and usually not associated with long-term psychological side effects. Limitations of ADs include acute and chronic complications related to cardiac rhythm device implantation, the requirement in some cases for more than one shock to terminate AF, the discomfort from shocks, as well as the need for sedation to alleviate pain from the shocks. With the ever-expanding role of catheter-based therapies for AF, it seems that the role of ADs in this regard is rather limited.

Methods for the development and assessment of atrial fibrillation and heart failure dog models

Objective

To report Medtronic experiences with the development of animal models for atrial fibrillation (AF) and chronic heart failure (CHF) using high-rate pacing for AF and microemboli for CHF.

Methods

For the AF model, an atrial lead was attached to a Medtronic Synergy™ neurostimulator, which was programmed to stimulate at 50 Hz in an on-off duty cycle. Atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and N-terminal pro brain natriuretic peptide (NT-proBNP) were assayed at select time points. For CHF model, a serial injection of 90 µm polystyrene microspheres at 62,400 beads/mL (Polybead, Polysciences, Inc.) was performed to induce global ischemia, either with weekly monitoring and embolization schedule (group 1, n = 25) or with biweekly monitoring and emboliation schedule (group 2, n = 36 ). Echocardiograms were used along with ventriculograms and magnetic resonance imaging scans weekly to assess cardiac function and ANP, BNP and NT-proBNP were monitored.

Results

For the AF model, the days to sustained AF for four animals following surgery were 7, 25, 21 and 19, respectively; For the CHF model, the days to meet CHF endpoints were 116 in group 1 and 89 in group 2. For both AF and CHF models, NT-proBNP correlated well with the development of disease states.

Conclusion

Our experience for the development and assessment of AF and CHF dog models may help researchers who are in search for animal model for assessing the safety and efficacy of a device-based therapy.