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ARTICLE CONTRIBUTORS

BM Glover MD Consultant Cardiologist and Electrophysiologist

Clinical Articles, Lead Article

HEART RHYTHM CONGRESS 2011

Dr Ben Glover, Consultant Cardiologist and Electrophysiologist, reports from the Heart Rhythm Congress 2011, held recently in San Francisco. He highlights some of the advances in cardiac devices, a novel computational mapping system for AF ablation, as well as the role of genetic testing in inherited conditions.

The sloping hills of San Francisco played host to the 32nd annual Heart Rhythm Congress from 4th to 7th May 2011. Attended by approximately 13,000 individuals the meeting combined late breaking trials, live electrophysiology cases as well as basic and translational science sessions. Dr Bruce Wilkoff, Staff Cardiologist and Director of Cardiac Pacing and Tachyarrhythmia Devices in the Department of Cardiovascular Medicine at the Cleveland Clinic, was nominated as the president for the forthcoming year taking over from Dr Doug Packer. Dr Wilkoff, who has been a member of HRS since 1985, plans to continue to promote development of arrhythmia management and in particular research and development of novel technologies. Despite the huge volume of presentations the key topics were as follows.

A prospective trial across 19 centres randomised 186 patients who underwent AV junctional ablation to either cardiac resynchronisation therapy (CRT) or right ventricular (RV) apical pacing. Current guidelines recommend CRT for patients with an ejection fraction of 35% or less, NYHA III or higher, and a QRS duration of 120 milliseconds or greater. Approximately 25% of patients met CRT guidelines and 75% did not. After a median of 20 months of follow up, the CRT group had a lower mortality from heart failure (hazard ratio 0.37), less worsening of heart failure (HR 0.27), and fewer hospitalisations for heart failure (HR 0.20). Overall mortality was similar in the two groups and this may provide further data to support the extension of CRT to a larger patient population.

The issues surrounding the potential detrimental effects of inappropriate implantable cardioverter defibrillator discharges were addressed in the ALTITUDE study.  It has been previously shown that there is an increased mortality in patients who have received both inappropriate and appropriate shocks. The difficulty is ascertaining whether it is the shock that results in myocardial dysfunction or whether the delivery of a shock is solely a marker related to more significant cardiac dysfunction. In this study researchers compared patients who received their first shock versus patients who did not receive a shock and matched them for other confounding variables.

Follow up occurred over a mean duration of 25 months. The most common arrhythmias which resulted in delivery of a shock, were sustained monomorphic ventricular tachycardia (VT) in 36% of cases, and polymorphic VT/ventricular fibrillation (VF) in 16% of cases. The most common reasons for inappropriate shocks were atrial fibrillation (AF)/atrial flutter in 18% of cases, supraventricular tachycardia (SVT)/sinus tachycardia in 17% of cases, and artifact in 5% of cases. Essentially the results showed that patients who received a shock for sinus tachycardia or artifact had no increase in mortality while those who received a shock for any arrhythmia including VT (sustained and non sustained), VF and AF had an increased mortality. This data implies that the increase in mortality is likely to be associated with the underlying condition rather than any detrimental effects of the shock.

Guidelines regarding the management of implantable devices during and after surgical or medical procedures were published. There are no large randomised control trials regarding this topic and therefore the guidelines are largely based on case series, case reports and expert opinion. The general features of the guidelines discuss the evaluation of the potential problems, which may occur in patients with implantable devices as well as recommendations for the appropriate preoperative evaluation as well as intraoperative and postoperative management of these patients. These guidelines will be published in the June edition of Heart Rhythm Journal.

The CONFIRM trial (Conventional Ablation For Atrial Fibrillation With Or Without Focal Impulse And Rotor Modulation) examined a novel computational mapping system used to visualise electrical rotors involved in AF allowing localised ablation (Focal Impulse and Rotor Modulation; FIRM) to be delivered. This was studied in 103 patients with a history of AF who received either FIRM, followed by Wide Area Circumferential Ablation (WACA) or WACA alone. Following this 41% of patients had an implantable loop recorder while the remainder had continuous ambulatory ECG’s at 3, 6, 9, 12 and 24 months. Rotors or focal beats were seen in 98% of patients with sustained AF during the procedure. FIRM alone terminated AF to sinus rhythm (often in less than 10 minutes) or acutely lengthened AF cycle length by >10%. Rotors or focal beat drivers were seen in almost all AF patients and targeted FIRM terminated or slowed AF and improved AF free survival when added to WACA. This introduces another potential exciting technology in the management of AF.

The incidence of symptomatic and asymptomatic AF was reported in 50 patients in 8 Canadian centres who had loop recorders implanted 3 months prior to and 18 months following pulmonary vein isolation. All patients were symptomatic prior to ablation and kept a diary of their symptoms. This was correlated with downloads from the implantable loop recorders. There was a reduction in AF/atrial flutter burden by 86% following ablation. The proportion of asymptomatic AF increased significantly post ablation. Asymptomatic episodes were shorter than symptomatic episodes. Overall this study demonstrates than measuring success based on symptoms is not particularly useful and may be somewhat misleading.

Risk stratification in Brugada syndrome using programmed electrical stimulation remains a controversial subject and overall risk stratification of patients is often challenging.  The PRELUDE prospective registry was designed to assess the accuracy of ventricular arrhythmia inducibility and identify additional predictors in Brugada syndrome. In order to help further risk stratification 308 patients with a type I ECG were followed over an average of 34 months.  Of the 14 patients who had a ventricular arrhythmia only 5 had a positive electrophysiology study suggesting that this was not particularly useful in predicting a ventricular arrhythmia (Positive Predictive Value 4%, sensitivity 35.7%). Multivariate analysis showed that as well as the presence of a type I ECG and a history of syncope two novel risk factors are a ventricular refractory period of less than 200 msec as well as QRS fragmentation.

There is an increasing role for genetic testing in inherited conditions with a predisposition to arrhythmias. In response to this HRS in conjunction with the European Heart Rhythm Association have released guidelines regarding patients who should be screened. This document focuses primarily on the state of genetic testing for long QT, Brugada syndrome, catecholaminergic polymorphic VT, hypertrophic Cardiomyopathy, AF, Short QT, Arrhythmogenic Right Ventricular cardiomyopathy, progressive cardiac conduction disease, left ventricular noncompaction, dilated cardiomyopathy and restrictive cardiomyopathy. The relative diagnostic, prognostic and therapeutic impact of the genetic test result for each entity is discussed. In general terms these guidelines help guide clinicians in patient selection and help guide treatment decisions based on the results in combination with the clinical scenario.

My personal highlights at this meeting included an excellent presentation by Dr Andre d’Avila  discussing the practical approaches to epicardial VT ablation, the VT symposium featuring presentations by world leaders in this field including Dr William Stevenson and Dr Francis Marchlinski and a superb session correlating ablation with basic anatomy.  This meeting is always of great educational importance and helps guide our clinical practice. San Francisco is a wonderful city and certainly worth a visit. I look forward to next year’s conference in Boston.

Published on: June 8, 2011

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ENDORSED BY

  • ArrhythmiaAlliance
  • Stars
  • Anticoagulation Europe
  • Atrial Fibrillation Association
 

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