September 2003 News -EP Lab Digest

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July 25, 2008

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September 2003 News

Industry News and Products: September 2003 News -

Cell Phones & Pacemakers: Reducing Risk Study Shows Some External Defibrillators Are Easier, Quicker To Use By Untrained People Study Findings Suggest Revised Approach to Therapy for Atrial Fibrillation Schizophrenia Drugs Linked to Increased Risk of Heart Attack Small, Implantable Heart Monitor May Provide More Accurate Diagnosis of Fainting Causes and Reduce Healthcare Costs Cell Phones & Pacemakers: Reducing Risk Digital mobile telephones have long been suspected of possibly causing some heart pacemakers to malfunction. The concern is that the devices, which ensure regular heart rhythm, can interpret the phone's electromagnetic signals as the heart's own beats. Does that mean you shouldn't use a cellular phone if you have a pacemaker? No, say leading experts, because the risk is generally low and can be further reduced with some simple measures. A new study indicates that pacemakers equipped with special ceramic filters may eliminate all potential danger. No Hang-ups “Electromagnetic interference is something that is ever present in the environment and comes in various forms, and cellular phones are another potential interaction,” says Mark H. Schoenfeld, MD, Director of the Cardiac Electrophysiology and Pacer Laboratory at the Hospital of Saint Raphael in New Haven, Connecticut. “But when it's been closely looked at, it's more of a theoretical concern than what has been previously appreciated. The risk is very low and cellular phones are present part of our lives, and have proven to be useful,” he says. “I wouldn't want to recommend pacemaker patients to not use them. It's different if we're talking about different type of electromagnetic interference that comes from an MRI, which is an absolute no-no for those with pacemakers.” Schoenfeld, Clinical Professor of Medicine at Yale University School of Medicine and past President of the North American Society of Pacing and Electrophysiology, recommends that pacemaker patients keep digital phones at least six inches away from the pacemaker site. Older analog phones have never been suspected of interfering with pacemaker function. “If you really want to be on the safe side, hold the phone to the ear opposite the side of where the pacemaker is located. But the concern is even less for patients who are not absolutely dependent on pacemakers. In some patients without a pacemaker there is no heart rhythm whatsoever. For others, their pacemakers kick in periodically to prevent that occasional spell where the heart can't beat on its own, and their risk is very low.” Study Shows Some External Defibrillators Are Easier, Quicker To Use By Untrained People Average time to lifesaving shock was shortest with Medtronic LIFEPAK® CR Plus As automated external defibrillators (AEDs) continue to be placed in more public locations for potential use by people with little or no AED training, new research indicates that the design of the defibrillator and the clarity of its instructions may make a difference in how effectively an AED can be used by untrained people to save a life. AEDs help to save lives by accurately recognizing and treating the most common cause of sudden cardiac arrest, which each year claims the lives of up to 450,000 Americans. New research reported in the July issue of the journal Resuscitation strongly validates efforts by governments and organizations such as the American Heart Association to encourage easy access and wider use of AEDs, which are becoming as ubiquitous in their wall cabinets as fire extinguishers. The new study tested and timed the performance of 24 men and women, all untrained, in delivering lifesaving therapy with three currently available, competitive brands of defibrillators. If the device detects a life-threatening heart rhythm, it will prompt the user to push a button to deliver life-saving therapy. The study was conducted by researchers at the Wellington School of Medicine and Health Sciences of the University of Otago in Wellington, New Zealand, The defibrillators were the Medtronic Physio-Control LIFEPAK® CR Plus, the Zoll AED Plus, and the Philips HeartStart® OnSite. “To overcome possible problems with safety and effective operation by the lay public, AED use must be intuitive,” the researchers said. “This requires a simple design, with clear, unambiguous instruction. The AED must be easy to activate and allow for rapid delivery of a shock.” Study Findings Suggest Revised Approach to Therapy for Atrial Fibrillation The preferred and most frequently used initial therapy for the common heart rhythm disorder atrial fibrillation (AF) is a strategy to restore and maintain a normal heart rhythm. However, a study supported by the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health found that this “heart rhythm” strategy prevents no more deaths than the alternative, often secondary, approach to treatment which merely controls the rate at which the heart beats, and may have some disadvantages, including more hospitalizations and adverse drug effects. Furthermore, the rhythm approach does not result in a lower risk of stroke, improved quality of life, or improved cognitive function, all of which had been presumed to be benefits over the “heart rate” strategy. These results, from the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) trial were published in The New England Journal of Medicine. “This study has important implications for treatment,” said NHLBI Director Claude Lenfant, MD. “It appears that the preferred therapy for many patients with atrial fibrillation may be a strategy to control the heart rate,” he added. Drugs used to control heart rate are usually less expensive, according to D. George Wyse, MD, Chair of the AFFIRM steering committee and Professor of Cardiology at the University of Calgary, Alberta. “The rate control approach may also be less costly due to a difference in the number of hospitalizations,” he added. “We found that patients in the rhythm control group were more likely to be hospitalized, and hospital costs account for the majority of total medical costs.” Wyse also noted that although statistically there was no significant difference between the two groups' death rates, there was a trend toward better survival in the rate control group after the first year. “This was surprising and the causes of deaths are currently being reviewed to try to better understand these results,” he said. Strokes were uncommon in both groups, according to Wyse, and tended to occur in patients not taking an anticoagulant or “blood thinner” like warfarin, or who were taking a dose that was too low. Wyse recommended continuous warfarin use in most patients with AF and risk factors for stroke, and he emphasized the importance of periodic monitoring of the dose. “The AFFIRM study has profound implications for the management of atrial fibrillation. For many physicians it should fundamentally alter their approach to treatment,” said Michael Domanski, MD, Cardiologist with the NHLBI and Head of the Institute's Clinical Trials Group. Domanski also acknowledged that the findings may not apply to every patient, particularly younger patients or those without risk factors for complications from AF. “Patients should discuss these findings with their doctor to see if they are relevant to them, and they should certainly not stop their medication without checking with their physician,” he added. AF is a common type of heart arrhythmia affecting over 2 million persons in the United States, many of them elderly. The disorder is increasingly prevalent — particularly in the older population — and is an important risk factor for stroke. Symptoms include palpitations, breathlessness, and dizziness. The disorder may sometimes be asymptomatic. AF occurs when electrical signals in the heart's upper chambers (the atria) are fired in a very fast, uncontrolled manner. Electrical signals then arrive in the heart's lower chambers (the ventricles) in an erratic pattern, creating an irregular heartbeat. The rapid and irregular beating, as well as the loss of coordination between the upper and lower chambers of the heart, affects the heart's ability to pump blood. The blood flow can become slow and stagnant, causing clots to form inside the heart. If these blood clots break away and block blood vessels, stroke or other organ damage can occur. Stroke prevention is a key component of therapy for AF, and both the “rate control” and “rhythm control” treatment strategies also use an anticoagulant drug to reduce the formation of blood clots. In the heart rate control strategy, therapy is aimed at controlling the rate at which the lower chambers of the heart (ventricles) beat, while allowing the atria to continue to fibrillate. Specific classes of medications used to control and slow the heart rate include digitalis, beta blockers, and calcium channel blockers. The rhythm control strategy uses antiarrhythmic drugs such as amiodarone, sotalol, and propafenone to try to convert the heart back to normal rhythm and then maintain normal rhythm. Rhythm control may also involve delivering an electrical shock to the heart, a procedure called cardioversion. Until AFFIRM, there had not been a large clinical trial comparing these two strategies. Between 1995 and 1999, AFFIRM investigators enrolled 4,060 patients at 213 U.S. and Canadian sites. Participating patients were followed until October 31, 2001. The Clinical Trial Coordinating Center was Axio Research Corporation in Seattle, WA. All patients in the study had AF and at least one other risk factor for stroke or death. Risk factors included age 65 or older, hypertension, diabetes, and congestive heart failure. Patients were randomly assigned to a rhythm control or rate control treatment strategy and were followed for an average of 3 ½ years. Both groups were treated with warfarin. Study physicians were allowed to choose among currently available therapies within the assigned treatment strategy. When drugs failed or could not be tolerated, non-drug therapies could be used when appropriate. These included electrical cardioversions; implantation of a permanent heart pacemaker; ablation, which uses radiofrequency energy to correct the rapid heartbeat; surgery; or combinations of these non-drug therapies with drugs. A relatively small number of patients were treated with non-drug therapies. Patients in AFFIRM could be switched to the alternate rate or rhythm control strategy when clinically indicated. The specific drugs initially chosen were: 1) Rate control group: digoxin, beta blockers, calcium channel blockers; or 2) Rhythm control group: amiodarone, sotalol, propafenone, procainamide, quinidine, flecainide, disopyramide, moricizine. More patients initially assigned to rhythm control crossed over to the rate control group than the reverse. This finding reinforces other studies that found antiarrhythmic drug therapies frequently fail, report the investigators. At the conclusion of the study, a total of 356 patients in the rhythm control arm had died from all causes compared to 310 in the rate control group. There was no difference observed when both strokes and deaths and other major events were considered together. During the study, there were 1,374 patients in the rhythm control group who were hospitalized compared to 1,220 in the rate control group. Adverse drug effects, which were more common in the rhythm control group, included bradycardia (abnormally low heart rate) and lung problems. All important subgroups that were analyzed, including "age greater than or equal to 65 years" and "presence of coronary artery disease or hypertension" showed either non-significant differences between groups or a benefit with rate control. Schizophrenia Drugs Linked to Increased Risk of Heart Attack Schizophrenic patients who take antipsychotic drugs are more likely to have experienced cardiac arrest or ventricular arrhythmia than non-schizophrenic patients, according to researchers at the University of Pennsylvania School of Medicine. While previous research has linked several of these drugs to irregular electrocardiogram results, the Penn researchers used billing data to uncover a link between the drugs and cardiac arrest. Their findings are presented in the British Medical Journal. The study's primary comparison was between thioridazine, which has a marked effect on the electrocardiogram, and haloperidol, which has less of an effect. “Overall, the risk with thioridazine was no worse than that with haloperidol. Thioridazine may, however, represent an elevated risk at high doses,” said Sean Hennessy, PharmD, PhD, Assistant Professor at Penn's Department of Biostatistics and Epidemiology. “To reduce cardiac risk, thioridazine should be prescribed at the lowest dose needed to obtain an optimal therapeutic effect.” Hennessy and colleagues conducted a cohort study of billing data collected between 1993 and 1996 from three Medicaid programs. The researchers included patients with more than one prescription for oral thioridazine and haloperidol, as well as the antipsychotic drugs risperidone and clozapine, plus at least two instances of a schizophrenia diagnosis. They compared the records of these patients with two control groups — one group of glaucoma patients and one group of psoriasis patients — since both patient types require periodic prescriptions and are not associated with cardiovascular problems. In all, they looked at data taken from over 120,000 patients. “We compared the frequency of cardiac arrest and ventricular arrhythmia associated with different antipsychotic drugs versus the control groups,” said Hennessy. “Our findings clearly link patients with treated schizophrenia to higher rates of cardiac arrest, ventricular arrhythmia, and death.” According to Hennessy, the elevated risk could be a result of either the disease or its treatment. While haloperidol and thioridazine both presented a similar overall risk in this study, the effect with thioridazine seemed to be dose-related. “Therefore, to minimize the risk of arrhythmia, it seems prudent to suggest that physicians prescribe the lowest dose of thioridazine possible,” said Hennessy. Separate data presented to FDA have suggested that thioridazine may have a greater effect than haloperidol on the QT interval as recorded on an electrocardiogram (ECG). The QT interval is defined as the time between the Q wave (when the heart's ventricles contract) and T wave (when the ventricles relax again). While QT prolongation is often used as a surrogate marker of a drug's cardiac risk, the true relationship is unknown. This study helps to clarify that relationship. “If our findings are confirmed, they would support the use of QT prolongation as a marker for a drug's risk,” said Hennessy, “There are still plenty of questions to be asked. Is there a certain subset of the population more at risk for developing a QT irregularity with certain drugs? Is there a role for regular ECG monitoring in individual patients? Obviously, we shouldn't be keeping QT on the Q.T.” Small, Implantable Heart Monitor May Provide More Accurate Diagnosis of Fainting Causes and Reduce Healthcare Costs Unexplained fainting affects 1 million Americans annually at a cost of $1 billion The use of a small, implantable monitor in patients who experience episodes of unexplained fainting (syncope) can lead to a diagnosis at a lower cost than conventional testing strategies, according to a study published in the Journal of the American College of Cardiology. Unexplained fainting affects more than 1 million Americans each year, is the cause of approximately 10 percent of falls by elderly persons and costs the U.S. healthcare system more than $1 billion annually. "People who suffer from mysterious fainting episodes often live in fear, and the time and testing efforts by physicians to help identify a diagnosis consume considerable healthcare resources," said Andrew Krahn, MD, the study's Principal Investigator and Associate Professor in the Division of Cardiology at the University of Western Ontario. "Our research shows that the Medtronic Reveal® Insertable Loop Recorder is both a cost-effective and quality diagnostic tool for many patients." To evaluate the benefits of the implantable monitor, investigators at the University of Western Ontario conducted a randomized clinical trial in 60 patients who were undergoing cardiac testing for unexplained fainting. Of the patients who received the Reveal monitor, 47 percent were successfully diagnosed, while only 20 percent who received conventional testing were accurately diagnosed. In new cost-effectiveness data published, the cost-per-diagnosis in those who were randomized to receive one year of monitoring with the Medtronic Reveal monitor was 30 percent less than the cost-per-diagnosis in those who received conventional testing. Conventional testing included two to four weeks of monitoring with an external loop recorder followed by tilt table and invasive electrophysiologic testing. The study authors concluded that the Reveal Insertable Loop Recorder (ILR) should be considered as an early-stage diagnostic tool for people without major structural heart disease who experience unexplained fainting spells. "We've already seen evidence that the insertable loop recorder is an effective tool for identifying why many people have syncopal episodes," said Krahn. "Now, we also have demonstrated a substantial cost savings related to use of the small implanted monitor compared to conventional diagnostic strategies that are often inconclusive." In another study about the diagnosis of syncope published in the New England Journal of Medicine in September 2002, researchers found that 10 percent of study participants with cardiac syncope would have died in six months without proper diagnosis and treatment for their cardiac condition. The second-generation Medtronic Reveal® Plus is an implantable cardiac monitor available to record the heart's rate and rhythm at the time of an unexplained syncopal episode. Placed just under the skin of the chest area using local anesthesia during a simple outpatient procedure, the monitor performs a function similar to that of a "black box" on an airplane, recording important data that can be saved and evaluated later to determine a diagnosis. It continuously monitors and can record the heart's electrical activity for up to 14 months. The Reveal Plus ILR may help diagnose whether symptoms like fainting, dizziness, palpitations and unexplained seizure-like episodes have a cardiovascular cause, or if the patient should be referred to another specialist, such as a neurologist.

EP Lab Digest - ISSN: 1535-2226 - Volume 3 - Issue 7: September - September 2003 - Pages: 40 - 44

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