Published in UAB Insight, Summer 2008
Highlights From the Rigorously Evidence-Based Recommendations
Cardiac device technology is a rapidly evolving area of clinical practice. In 2005 US patients with cardiac rhythm abnormalities received an estimated 180,000 pacemakers and 91,000 implantable cardioverter-defibrillators (ICDs). "The expansion of indications for device implantation necessitates education and guidance to ensure that their prescription is evidence based," says UAB cardiologist Andrew E. Epstein, MD, who chaired the writing committee for new device-based therapy guidelines.
These guidelines incorporate expert analysis of recent studies that have increased knowledge of cardiac arrhythmias and major advances in device technology. They are the most recent comprehensive examination of device-based therapy indications for life-threatening cardiac arrhythmias, heart failure, congenital heart disease, and sudden cardiac arrest. The American College of Cardiology (ACC), American Heart Association (AHA), and Heart Rhythm Society (HRS) jointly released the recommendations in May and posted the full text on their Web sites (www.acc.org, www.americanheart.org, www.hrsonline.org).
"The ACC/AHA/HRS 2008 Guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities" take a patient-centered approach and will help physicians determine the most appropriate and effective treatments for individual patients. The recommendations are thoroughly evidence-based, incorporating data on efficacy and clinical outcomes from dozens of clinical trials and advances in pacemaker and ICD therapies. The task force considered patient-specific modifiers such as comorbidities, patient preferences, and cost-effectiveness. The authors also note the importance of follow-up of these devices.
Throughout the guidelines the authors emphasize achieving optimal drug therapy before device implantation. "First and foremost patients must be on the appropriate drugs titrated to optimal doses. Too often drugs are not titrated for maximum effect; for example, half of patients on long-term anticoagulation therapy are out of therapeutic range a significant portion of time," Epstein says.
Pacemakers
The writing committee clearly defined indications for pacemaker use for commonly recognized reasons of slow heart rates and for emerging indications such as heart failure (so-called cardiac resynchronization therapy [CRT]). In the last 5 years cardiologists have increasingly understood the deleterious clinical effects that occur with right ventricular apical (RVA) pacing. Studies have demonstrated an association between RVA pacing and higher risk of atrial fibrillation, heart failure, ventricular arrhythmias, and death during ICD therapy. The authors encourage optimized pacemaker programming to minimize unneeded RV pacing.
Cardiac Resynchronization Therapy
Given the enthusiasm for CRT, the committee provided guidance on the requirement that these devices be prescribed only when heart failure patients still experience significant symptoms while being treated with optimal recommended medical therapy. CRT pacing is not appropriate for asymptomatic patients. Notably CRT may also serve as a bridge to cardiac transplantation.
Biventricular pacing improves functional capacity and quality of life and decreases hospitalizations and mortality for selected patients. Guideline authors' analyses of clinical experiences and larger subsequent trials confirm a 30% decrease in hospitalization and a mortality benefit of 24% to 36% with CRT.
The COMPANION (Comparison of Medical Therapy, Pacing, and Defibrillation in Heart Failure) trial found that CRT with defibrillation reduced mortality by 36% in patients with New York Heart Association (NYHA) class III symptoms and a left ventricular ejection fraction (LVEF) of ≤35%. The authors conclude that for patients with a LVEF ≤35%, CRT with or without an ICD is indicated for treatment of NYHA functional class III or ambulatory class IV heart failure symptoms.
To achieve the most favorable outcomes with CRT, left ventricular leads must be positioned correctly, heart failure management with neurohormonal antagonists and diuretic therapy must continue, and device parameters may need periodic reprogramming.
Implantable Cardioverter-Defibrillators
Revised ICD indications reflect new developments and consider voluminous literature related to device efficacy in treatment and prevention of sudden cardiac death due to life-threatening ventricular arrhythmias. Early studies showed ICDs decrease mortality when implanted in patients who have been resuscitated from a cardiac arrest. More recent large randomized studies have established that ICDs also improve survival in selected patients who have not had a cardiac arrest or sustained ventricular tachycardia, ie, primary prevention.
"At this time 80% of ICD implantation is for primary prevention, but there is some degree of under-referral," Epstein says. "Physicians may not be aware of the survival benefit for primary prevention or may think their patient is not sick enough to warrant a device." Because of overlap between primary and secondary indications for ICDs, guideline authors combined recommendations for all such devices and made recommendations easier to use.
Criteria for ICD implantation rely heavily on the measured LVEF; therefore, ICD implantation recommendations rely heavily on results of primary prevention trials such as MADIT I and II (Multicenter Automatic Defibrillator Implantation Trials), SCD-HeFT (Sudden Cardiac Death in Heart Failure Trial), and DEFINITE (Defibrillators in Nonischemic Cardiomyopathy Trial). Analyses of trials support the conclusion that ICD therapy in high-risk individuals with coronary artery disease results in a 20% to 30% reduction in total mortality.
The authors acknowledge that commonly used clinical techniques of LVEF determination vary and suggest clinicians use the method that is most clinically accurate and appropriate at their institution. The indication for ICDs in those with ischemic cardiomyopathy and LVEF ≤30% is elevated to class I (beneficial, useful, and effective) in accord with MADIT II findings. ICD indications in nonischemic cardiomyopathy are clarified using data from SCD-HeFT and DEFINITE.
Secondary prevention trials are robust and consistently demonstrate improved survival with ICD therapy compared with antiarrhythmic drug therapy regardless of the type of underlying structural heart disease. Large prospective secondary prevention trials - AVID (Antiarryhthmics Versus Implantable Defibrillators), CASH (Cardiac Arrest Study-Hamburg), and CIDS (Canadian Implantable Defibrillator Study) - associate ICD implantation with a 50% relative risk reduction for arrhythmic death and a 25% relative risk reduction in all-cause mortality (N Engl J Med. 1997;337:1576-1583; Am Heart J. 1994;127:1139-1144; Circulation. 200;101:1297-1302).
Humanistic Approach
Epstein describes the recommendations, rewritten "from stem to stern," as humanistic and patient oriented. The authors have formally articulated the importance of discussing risks and benefits of implanted devices, life expectancy, and quality of life issues with patients and families to ensure that expectations of the results of therapy are appropriate. "Lack of patient understanding and adherence may adversely affect treatment outcomes," the authors write. "Physicians must make every effort to engage patients in active participation in prescribed medical regimens and lifestyles."
Given the broader primary prevention ICD indications and increased use of the devices, the task force emphasizes the critical importance of understanding the causes and frequency of inappropriate shocks and devising management strategies that mitigate both inappropriate therapies and their psychological and quality of life consequences.
As physicians, patients, and families increasingly are faced with decisions about device-based therapies in older adults, consideration must be given to life expectancy estimates, comorbidities, procedural risk, and patient preference. Only patients receiving optimal medical therapy who have a reasonable expectation of survival with good functional capacity for >1 year should be considered for device therapy.
Few clinical trials of device-based therapy have included many patients aged >75 years with multiple comorbidities. Older patients may derive less benefit from ICD therapy than younger individuals. For patients with advanced heart failure, the authors state that when ICDs and CRT are discussed, the likelihood of life-saving and inappropriate shocks should be placed in the context of the overall anticipated mortality from heart failure, the expected duration of life prolongation after therapy, and the natural progression of symptoms, and ultimately, death.
"The likelihood of meaningful prolongation of life by prevention of sudden cardiac death must be assessed against the background of other factors that limit patient function and survival. Aspects such as repeated hospitalizations and comorbidities in the setting of kidney dysfunction or advanced age influence the value patients place on quality versus length of life remaining," Epstein says.
Cardiologists who implant devices need to discuss end-of-life issues and device deactivation with patients, as these are increasingly encountered clinical concerns. Patients and families fear devices will deliver uncomfortable defibrillations during the dying process.
"Pacemakers, ICDs, and CRT devices are all life-sustaining treatments," he says. "To impose them on patients who do not want them is not right, and indeed, unethical. As technology advances, indications for ICD and CRT device implantation will evolve. These guidelines extend and clarify current best practices and offer the best evidence available for treating patients with heart disease."
FOR MORE INFORMATION:
Dr. Andrew Epstein
1.800.UAB.MIST
mist@uabmc.edu