A roundup of breaking cardiac news

SEPTEMBER 11, 2008
Revisiting patient stratification: Fiscal and clinical components of using MTWA to identify ICD candidates
Using microvolt T-wave alternans (MTWA) to stratify which patients would most benefit from implantable cardioverter-defibrillator (ICD) therapy could have important cost and policy implications, say researchers from the University of Michigan Cardiovascular Center and the Ohio Heart and Vascular Center. In addition, this research also indicates that as many as one third of the patients receiving the implanted devices could forego the operation without raising their risk of sudden death.

Left ventricular ejection fraction has long been used to identify patients at high and low risk of sudden cardiac death, but this technique is limited by low specificity. Building on their earlier research that showed that MTWA is an independent predictor of all-cause, risk-adjusted mortality in patients with ischemic cardiomyopathy, Paul Chan, MD, MSc, and colleagues evaluated whether ICD benefit occurred only in those higher-risk patients who test positive or inconclusive with MTWA.

The study drew on data from 768 patients who were candidates for ICD implantation who had survived myocardial infarctions but had ischemic cardiomyopathy. Each patient received an MTWA test, among others, during their evaluation. Half of the patients went on to receive ICDs, although the MTWA test results were not used in the decision-making process. Patient outcomes were followed for up to 3 years.

In all, 67% of patients had positive or inconclusive MTWA test results. Of them, the patients who went on to receive an ICD were 55% less likely to die in the follow-up period than those who had not received an ICD. They were also 70% less likely to die suddenly from a heart-rhythm disruption. But at the same time, the one third of patients who had negative MTWA tests and then received ICDs were no less likely to die than those with similar test results who did not receive ICDs.

If these findings hold up in larger studies, the financial impact could be enormous. As ICDs have been shown to reduce the overall risk of sudden cardiac death, they have been approved by the Food and Drug Administration and are now covered by Medicare and other insurers. In fact, in 2004, Medicare expanded the group of patients who were eligible for ICD therapy, leading to estimates that 50,000 new patients each year can qualify for the devices based on criteria relating to their heart rhythm and pumping capability. But if every Medicare participant who qualified for an ICD under current guidelines received one, it would cost the Medicare system an additional $2.9 billion to treat all of them for life.

The authors of an accompanying editorial point out that the study may not have been adequately powered to detect ICD benefits in the MTWA-negative group, and that it was not a randomized, prospective one.

Nevertheless, the questions raised by such a study point out the conflicts inherent in modern medicine. As the authors note when speaking specifically about ICDs, “The challenge for policy makers and clinicians alike is to find effective risk-stratification strategies that further define which patients are most and least likely to benefit.” In today’s technology-heavy but cost-constrained environment, this challenge is faced by every branch of medicine.

The study is published in The Journal of the American College of Cardiology. 2007;49(1):50-58.

February is American Heart Month
Once again, as it has every year since 1963, February has been declared American Heart Month. In addition to increasing general awareness of heart disease and encouraging healthier lifestyles, the month is also an occasion for volunteers from the American Heart Association to visit neighbors and raise funds for research and education, and pass along information about heart disease and stroke.

Reducing work-related stress—at work
Italian workers facing the stress of layoffs were able to reduce arterial blood pressure and achieve small but significant changes in heart rate variability through a work-sponsored stress management program.

Of the 91 recruits to the year-long program, 26 self-enrolled in weekly 1-hour stress management sessions during lunch breaks (the active program), while 25 enrolled in a sham program that offered articles and monthly e-mails on stress reduction techniques. The weekly stress management sessions focused on mental relaxation techniques, as well as cognitive restructuring exercises and coping skills to face life stressors—including work-related stress. These participants were compared with a second group of 79 healthy volunteers from outside the company who did not complain of any work-related problems.

Researchers led by lead author Massimo Pagani, MD, professor of medicine at the University of Milan, Italy, had participants fill out a self-administered questionnaire indicating their perceived levels of overall stress, tiredness perception, and stress-related symptoms. Researchers also tested the autonomic nervous system by using a single-lead electrocardiogram (ECG), a scaled down version of the usual multiple-lead ECG.

At baseline, the workers had significantly higher stress and tiredness scores than controls, averaging 5.20 versus 2.94 for stress and 5.28 versus 3.27 for tiredness. Workers also reported more stress-related symptoms such as difficulty in sleeping, pounding of the heart, or gastrointestinal problems. Compared with controls, the stressed workers had altered values in the ECG measurement that assesses nervous system regulation of heart rate. So, as expected, workers facing layoffs were feeling more stress and their heart rhythm was showing signs of that stress.

At the end of the year, workers’ scores on a test measuring perceived stress were significantly lower than baseline scores. Moreover, workers said they felt less tired than they did before the stress management training.

Because individuals spend so much time at work, this type of approach may have multiple benefits. By addressing stress “at work, where stress occurs, rather than in a clinic, we may be able to prevent these workers from becoming patients,” said Dr Pagani.

Because the study was small in scale and the participants self-selecting, the authors caution that the findings should not be considered definitive. “The practical long-term impact of this approach on symptoms, well-being, and health of interested workers requires further specific longitudinal studies on large populations,” cautioned Dr Pagani.

Nevertheless, “our study provides a potential model for the assessment of work-related stress at an individual level and suggests that stress management programs can be implemented at the worksite.”

The findings appear in the February 2007 issue of Hypertension.

An obesity paradox in acute heart failure hospitalization
All physicians, especially cardiologists, regularly counsel patients regarding the health benefits of weight loss. But surprisingly, extra weight can have a beneficial effect for patients hospitalized for heart failure (HF).

Researchers led by Gregg C. Fonarow, MD, of the Ahmanson-UCLA Cardiomyopathy Center, David Geffen School of Medicine at UCLA, analyzed HF hospitalization data from the Acute Decompensated Heart Failure National Registry (ADHERE), finding 108,927 episodes between October 2001 through December 2004. Patients with documented height and weight were divided into body mass index (BMI) quartiles.

In-hospital mortality rates decreased across successively higher BMI quartiles even after adjustment for such factors as age, sex, blood urea nitrogen, blood pressure, creatinine, sodium, heart rate, and dyspnea at rest. For every 5-unit increase in BMI, the odds of risk-adjusted mortality was 10% lower.

Although other studies have demonstrated an inverse relationship between BMI and long-term mortality in HF, this study is notable for demonstrating this affect during the course of a single hospitalization. The reasons for this relationship are unclear, although the authors posit it may be due to patients with higher BMI presenting at a less advanced stage of the disease; that the healthy-weight patients may have inadequate nutritional intake to help combat the disease; or that obesity alters the pharmacokinetics of HF medications.

Whatever the causes, the authors caution against taking the study findings as a rationale against weight reduction in overweight and obese patients. 



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