The primary purpose of an implantable cardioverter-defibrillator (ICD) is to stave off a heart attack.
But a study published in the Sept. 4 issue of the New England Journal of Medicine (NEJM) will have patients wondering about the benefits of these devices because the study concludes that heart failure patients with an ICD who receive therapeutic shocks from the device have a "substantially higher" risk of death than those who do not receive shocks.
Responding to the study, various industry organizations were quick to emphasize the continuing therapeutic importance of ICDs.
Using data from the Sudden Cardiac Death in Heart Failure Trial, Jeanne Poole, MD, and her colleagues followed the cases of 811 people with defibrillators and found that any shock increased the risk of death.
The study found that those receiving an appropriate life-saving shock were six times more likely to die, compared to those not receiving a shock. Additionally, the study found that 30% of these deaths come within a day of the jolt, the researchers found.
Additionally, an inappropriate ICD shock, as compared with no inappropriate shock, was associated with a significant increase in the risk of death. And for patients who survived longer than 24 hours after an appropriate ICD shock, the risk of death remained elevated
The study authors said the most common cause of death among patients who received any ICD shock was progressive heart failure.
Poole, of the University of Washington (Seattle), said, "The most important thing to remember is that the defibrillators save lives," and that a defibrillator shock may be a danger signal that patients and doctors should heed.
The Heart Rhythm Society (HRS; Washington) issued a statement with its interpretation of the findings: that the patients who received shocks were in worse health than those who did not need to be shocked. Thus, HRS interpreted the increased death rate as related to the patient's overall health rather than the device itself. HRS said that ICDs are 99% effective in stopping life-threatening arrhythmias, calling the devices the most successful therapy to treat ventricular fibrillation, the major cause of sudden cardiac arrest.
The Advanced Medical Technology Association (AdvaMed; Washington) issued a statement saying it is important to put the study results in the context of the significant overall patient benefit of ICDs. "First and foremost, ICDs are incredibly successful in achieving their primary purpose: saving lives," said David Nexon, senior executive VP of AdvaMed, in the statement.
In an editorial accompanying the study, Jeff Healey, MD, and Stuart Connolly, MD, say it is "somewhat disturbing to realize that actually receiving a shock is such an important predictor of death." However, they note that it should not be surprising that many patients in whom sudden death from arrhythmia is averted by an ICD ultimately die from heart failure.
"In severe chronic conditions, most worthwhile interventions only modestly delay death. If a specific therapy is effective against only one cause of death and does not address the underlying disease process, then death from competing causes is inevitable," Healey and Connolly write. They also note that it is plausible, though unlikely, that ICD shocks somehow have an adverse effect on myocardial function.
Study: CAS as effective as CAE medium term'
Two studies appearing in the Sept. 6 issue of The Lancet Neurology concludes that to prevent ipsilateral stroke in patients with stenosis of the cartoid artery, carotic angioplasty with stenting (CAS) shows a similar level of effectiveness as the surgical procedure for clearing the carotid, termed carotid artery enarterectomy (CAE). Both trials conclude that CAS is an appropriate alternative to CAE in the medium term. However, they also found a greater risk for stroke following CAE 30 days after the procedure and that this must be taken into consideration. This risk can be reduced, the studies conclude, through a better set of criteria to select patients.
Thus far, CAE has been considered the standard procedure. The less-invasive CAS procedure widens and reinforces the vessel using a stent, but the procedure may not remove the plaque or it may loosen debris, providing a risk of stroke and other complications.
Researchers in the Stent-Protected Angioplasty Versus Carotid Endarterectomy (SPACE) randomized trial examined CAE and CAS in 1,214 patients in Germany, Austria, and Switzerland. The rates of ipsilateral ischemic stroke and restenosis were measured up to two years after the procedure, with blockage recurrence of at least 70% of the vessel diameter evaluated by ultrasound.
In patients with stents, blockage recurrence was more common (10.7%) in comparison with patients who had the CAE procedure (4.6%). But, there was no significantly increased risk in this group for ipsilateral ischemic stroke in comparison with the surgery patients (9.5% vs. 8.8%).
A long-term follow-up looked at 527 patients at 30 different centers in France to find the composite outcome of any stroke, or death within 30 days of undergoing CAS (265 patients) or CAE (262 patients). Though stented patients had twice the risk of this outcome, stroke was usually soon after the procedure (within 30 days) and there was no difference in risk of ipsilateral stroke after a stroke occurred in this group. After this initial period, in the medium term, therefore, CAS seems as effective as CAE.
In an accompanying commentary, A. Ross Naylor of the Leicester Royal Infirmary recommended future directions for research in the field of CAS. He wrote: "The mid-term to long-term results ... add substantially to the body of data from randomized trials that compare CEA with CAS for the management of patients with severe carotid disease who have recently developed symptoms."
He said that the most important findings from the studies "is recognition that the average annual risk of ipsilateral stroke is 1% or less, irrespective of whether the patient was treated by CEA or CAS."
Study downplays side effects of ICD therapy
Contrary to the above report, another study in the same issue of the NEJM offered a significantly positive view of this therapy, concluding that ICDs not only reduce the risk of death but also offer no significant alteration in the patient's quality of life.
Researchers at Duke University Medical Center (Durham, North Carolina), say their study is the longest and most comprehensive analysis of ICD use and that the findings should ease physician and patient concerns about the side effects of this therapy.
"Basically, we wanted to find out if ICD therapy improves longevity but only at the cost of worse quality of life," says Dr. Daniel Mark, a cardiologist at Duke and the lead author of the study.
Mark and colleagues studied 2,521 patients enrolled from 1997 to 2001 in the Sudden Cardiac Death in Heart Failure Trial, with all participants receiving what was billed as "state-of-the-art" medical therapy for heart failure. One-third of the patients were randomly assigned to receive an ICD, a second group was assigned to receive the anti-arrhythmia drug amiodarone, and a third group took an amiodarone placebo. Researchers interviewed each participant four times over a 30-month period to assess disease status, physical and social activity levels, psychological well-being and ability to perform routine daily tasks.
While members of all groups had essentially the same scores on psychological well-being at the beginning of the study, patients with the ICDs had somewhat higher quality of life scores at three and 12 months, when compared to those in the other groups. Scores of other quality-of-life measures also improved over a short term among ICD users, but all differences diminished over time and disappeared at 30 months.
Multiple molecular markers point to MI
A study led by investigators from Massachusetts General Hospital (MGH; Boston) and the Broad Institute of Harvard and MIT (Cambridge) concludes that a new technique that measures hundreds of molecular markers in the blood can identify those released when cardiac tissue is injured by a lack of oxygen. The report appears in the October Journal of Clinical Investigation.
Senior author Robert Gerszten, MD, of the MGH division of cardiology and Center for Immunology and Inflammatory Diseases, said, "Right now there are no blood markers for reversible myocardial injury in clinical use, and the only available markers are not detectable until hours after the onset of tissue damage. Because our treatments for heart attacks are most effective in the first hours after symptoms occur, these newly identified markers could help us apply treatments sooner and help more patients."
The research team took advantage of a procedure that is, in essence, a planned heart attack. In a condition called hypertrophic cardiomyopathy, bloodflow out of the heart is obstructed by a massive thickening of the wall between the left and right sides. This tissue overgrowth can be treated with the technique of septal ablation that destroys the excess tissue, a scenario that mimics the damage that happens to heart muscle when its blood supply is cut off.
The researchers analyzed blood samples from 36 patients taken before and at several time points after septal ablation. Using advanced mass spectrometry that can assess hundreds of metabolites in as little as 10 minutes, they identified several that significantly changed right after the ablation process, a time period during which currently available markers remained unchanged. The changes seen in the first 10 minutes persisted an hour later, and analysis of blood from veins in the coronary circulation confirmed that the heart was the source of the changes.
Comparing the results of these "planned" heart attacks with blood samples from patients with spontaneous coronary blockages found four metabolites that increased in response to ablation and also were elevated in patients with true heart attacks, confirming them as markers of myocardial damage.