Medical Device Daily Associate

The 2006 Guidelines for Management of Patients with Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death (SCD) were jointly released Tuesday by the American College of Cardiology (ACC; Bethesda, Maryland), American Heart Association (AHA; Dallas) and the European Society of Cardiology (ESC; Sofia Antipolis, France).

The European Heart Rhythm Association and the Heart Rhythm Society (Washington) also collaborated on the statement.

The purpose of the document is to update and combine the previously published recommendations into one source approved by the major cardiology organizations in the U.S. and Europe. This document completes the triad of arrhythmia-based guideline topics cosponsored by the ACC, AHA and ESC. In addition to ventricular arrhythmias and SCD, management of patients with supraventricular arrhythmias and atrial fibrillation (AF) also has been addressed in separate documents, with AF considered earlier this month

Ventricular arrhythmias (VA) are abnormal rapid heart rhythms (arrhythmias) that originate in the lower chambers of the heart (the ventricles) and often lead to SCD.

In 90% of adult victims of sudden cardiac death, two or more major coronary arteries are narrowed by fatty buildups. Scarring from a prior heart attack is found in two-thirds of victims. When sudden death occurs in young adults, other heart abnormalities are more likely causes including genetic diseases. Adrenaline released during intense physical or athletic activity often acts as a trigger for SCD when these abnormalities are present. Under certain conditions, various heart medications and other drugs – as well as illegal drug abuse – can lead to abnormal heart rhythms that cause sudden death.

According to the statement, the term “massive heart attack” is often wrongly used outside the physician community to describe sudden death. The term “heart attack” refers to death of heart muscle tissue due to the loss of blood supply and therefore oxygen, not necessarily resulting in a cardiac arrest or the death of the heart attack victim. A heart attack may cause cardiac arrest and SCD, but the terms are not synonymous.

The new guidelines outline recommendations on the evaluation and treatment of patients who have or may be at risk for VA. Evaluation includes noninvasive and invasive techniques such as electrocardiography and electrophysiological testing. Possible therapies include pharmacological (drugs), devices, ablation, surgery and revascularization.

Prognosis and management are individualized according to symptom burden and severity of underlying heart disease in addition to clinical presentation. In addition to recommendations in patients with specific pathology, cardiomyopathy and heart failure, specific populations are also covered, such as athletes, pregnant women, the elderly and pediatric patients.

One of the most important updates in the 2006 document is that the implantation of devices now has a range of ejection fractions. Ejection fraction (EF) measures how effectively the heart's left ventricle pumps blood to the body. A normal, healthy heart has an EF in the range of about 50% to 70%.

“Prior to this document,” said Douglas Zipes, MD, co-chair of the guideline writing committee, “practitioners faced inconsistent recommendations for prophylactic ICD implantation based on ejection fractions, for example. The inconsistencies occurred because clinical investigators chose different ejection fractions for enrollment in trials of therapy, average values of the ejection fraction have been substantially lower than the cut off value for enrollment and subgroup analysis of clinical trial populations based on ejection fraction have not been consistent in their implications. The result was substantial differences among guidelines.”

Cambridge Heart (Bedford, Massachusetts) reported that the guidelines recommend that the T-Wave Alternans receive a Class IIa guideline under the section, Electrocar-diographic Techniques and Measurements.

Microvolt T-Wave Alternans are the first diagnostic tools cleared by the FDA to non-invasively measure microvolt levels of T-wave alternans, subtle beat-to-beat fluctuations in a person's heartbeat.

The consensus guideline says, “It is reasonable to use T-Wave Alternans for improving the diagnosis and risk stratification of patients with ventricular arrhythmias or who are at risk for developing life-threatening ventricular arrhythmias. (Level of Evidence: A).”

“This new societal guideline validates the importance of our diagnostic test,” said David Chazanovitz, president and CEO of Cambridge Heart. “It provides assurance to the cardiology community of the efficacy of the test and the role it can play in managing patients at risk of sudden cardiac death. It serves to answer the concern of practicing cardiologists with respect to integrating the Alternans test into their practices as the societies have formally given guidance on MTWA testing for the first time.”

In the guidelines on AF announced earlier this month, the authors recommended that risk factors for stroke should be used to determine whether anti-clotting therapy is given to people with AF.

The most recent AF guidelines, published in 2001 recommended using several patient characteristics – age, gender, heart disease risk and concurrent conditions – to decide proper anti-clotting therapy for these patients. The new approach recommends that the risk for stroke should be the main factor.

“We focused on stroke risk because AF is associated with increased long-term risk for stroke,” said Valentin Fuster, MD, PhD, co-chair of the guidelines writing committee, fellow of all three associations, and professor of medicine and director of the Mount Sinai Cardiovascular Institute (New York). “About 15% to 20% of strokes occur in people with AF, and those strokes are especially large and disabling.”

In the U.S. and Europe, hospital admissions for AF have increased by 66% during the last 20 years. It also is expensive, with total costs approaching EUR 13.5 billion (about U.S. $15.7 billion) in the European Union alone, according to the statement. No figures are available for total U.S. costs.

Another significant new addition to the AF guidelines is catheter ablation – a procedure that corrects irregular heartbeat with radio frequency energy. The joint statement found catheter ablation to be “a reasonable alternative to drug therapy to treat AF in patients with little or no left atrial enlargement, and in whom drug treatments did not stop the rhythm disturbance,” said Fuster.

The executive summary for the new VA guidelines and the prevention of SCD will be published in the Sept. 5 issues of the Journal of the American College of Cardiology, and Circulation: Journal of the American Heart Association, and the first September issue of the European Heart Journal. The full-text guideline is published in Europace and e-published in the same issue of the journals noted above, as well as posted on the ACC, AHA and ESC web sites.