Implantable defibrillators in cardiomyopathy: a clarification

Cate Swannell
Med J Aust
Published online: 23 March 2020

A CLARIFICATION of the 2018 guidelines from the National Heart Foundation and the Cardiac Society of Australia and New Zealand, which provide evidence-based direction for the management of heart failure in Australia, has been published online today by the Medical Journal of Australia.

Professor Peter Kistler, Head of Electrophysiology at Alfred Health in Melbourne, and his co-authors wrote that a response to the guidelines’ original publication had questioned “the weak recommendation for the implantation of a defibrillator in the primary prevention of mortality in dilated cardiomyopathy (DCM) with a left ventricular ejection fraction (LVEF) of 35% or below”.

“We welcome this opportunity to clarify the basis for the Australian guidelines recommendation,” Kistler and colleagues wrote.

“To understand the heart failure disease process, it is fundamental to recognise the differences in mechanisms of death and prognosis in ischaemic cardiomyopathy (ICM) versus DCM.

“Sudden cardiac death is more frequently responsible for mortality in ICM compared with pump failure and death from non-cardiac causes in DCM.

“As such, defibrillators that provide shocks for ventricular arrhythmias are expected to significantly reduce mortality when sudden cardiac death is the major contributor. Combined with recent clinical trial data, this is the foundation for the current guidelines in primary prevention, making a strong recommendation for a defibrillator in reducing mortality in ICM compared with a weak recommendation for DCM.

“Implanting physicians are cognisant of potential harm, with Australian data reporting [implantable cardioverter defibrillator (ICD)]-related complications requiring rehospitalisation or re-operation in 10% of patients. Battery longevity and defibrillator lead durability are additional considerations.

“Careful patient selection is required to identify patients with DCM likely to benefit from ICD therapy. The 2018 Australian guidelines draw attention to the increased efficacy of ICD therapy in patients younger than 70 years.

“The weak recommendation for ICDs for the primary prevention of mortality provides the support for a considered decision between patient and physician, balancing the absence of randomised controlled trial data with the morbidity of an ICD implant,” Kistler and colleagues concluded.

  • Cate Swannell



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