Bailus Walker Jr., PhD, MPH, Department of Community and Family Medicine, College of Medicine, Howard University, Washington, DC, USA.
Charles Mouton, MD, MS, Department of Community and Family Medicine, College of Medicine, Howard University, Washington, DC, USA.

In the late 1990s, it became increasingly clear that air pollution, even at the lower ambient concentrations prevalent in many urban areas, is associated with increased mortality and other serious health effects. More recently, considerable research has focused on particulate air pollution as studies have linked a growing number of health effects to fine particles. Hundreds of studies now indicate that breathing fine particles discharged by vehicles, factories, and power plants can trigger a cardiac event and exacerbate respiratory disease in vulnerable populations. Older adults are one subgroup considered more susceptible to the effects of airborne particles. This sensitivity can be attributed to a number of factors including loss of pulmonary functional reserve and compensation due to age or disease. Although a number of mechanisms have been proposed to explain the adverse impact of particles on cardiovascular health, many questions remain. Their answers will require further transdisciplinary research.
Key words: heart disease, air pollution, smog, particulates, older adults.

Robert S. Sheldon, MD, PhD, FRCP(C) and Satish R. Raj, MD, FRCP(C), Cardiovascular Research Group, University of Calgary, Calgary, AB.

Implantable cardioverter-defibrillators are pacemaker-like devices that sense and treat ventricular tachycardia and ventricular fibrillation, and are generally used in an aging population. They have been proven in large randomized clinical trials to prevent death in patients who have already survived a life-threatening episode of ventricular arrhythmias. Recent studies have expanded their indications to the prevention of arrhythmic death in patients who have risk factors for this disorder. How widely they will be used, and at what cost, is unknown.
Key words: implanted defibrillator, arrhythmia, sudden death, anti-arrhythmic therapy, heart disease.

Two studies, recently published in the New England Journal of Medicine, have suggested a role for radiation therapy in the treatment of restenosis. Every year, thousands of patients undergo balloon angioplasty to open clogged arteries. In 60% of these cases, physicians also insert a stent to keep the artery propped open. Unfortunately, in 35% of cases, restenosis occurs and the patient has to undergo another angioplasty or a bypass operation. Both studies investigated the use of placing radioactive materials into the arteries for a short period of time, and then removing them. Where the studies differ is in the type of radiation that is used. In the first study, the researchers used beta radiation, considered safer because it does not penetrate past the body of the patient. In the second study, gamma radiation was used, and health-care workers had to be shielded.

In the study of beta radiation, 181 patients were treated who had undergone angioplasty for the first time. Once the blockage had been cleared, a radioactive coil was inserted into the artery and was subsequently removed, after a few minutes. Patients were given heart scans six months later and it was found that restenosis had occurred in only 29% of patients who had received the lowest dose of radiation, and in 15% of those who had received a dose that was two times as high.

In the second study, patients had already undergone a previous angioplasty procedure. In 131 patients, after undergoing a new angioplasty, a tiny ribbon containing gamma radiation was inserted and was removed after 20 minutes. In another 121 patients, the procedure was replicated with an identical looking ribbon that contained no radiation. At 6 months post-procedure, 28% of the patients in the radiation treatment group had restenosis, as compared to 44% in the comparison group. Unfortunately, several months after the procedure, 5% of radiation patients developed dangerous blood clots, as compared to only 1% in the control group.

The technique would mean that many patients could be spared bypass surgery or repeated angioplasties, but is obviously associated with several caveats. Further studies with larger numbers of patients are required before any definitive conclusions can be made regarding the effectiveness of the technique. In addition, the possible development of cancers, as a side effect of the radiation treatment in these patients, is of major concern.

Sources

1. Verin, V et al. Endoluminal Beta-Radiation Therapy for the Prevention of Coronary Restenosis after Balloon Angioplasty. NEJM 2001;344:243.
2. Leon, MB et al. Localized Intracoronary Gamma-Radiation Therapy to Inhibit the Recurrence of Restenosis after Stenting. NEJM 2001;344:250.

Lilia Malkin, BSc

Heart disease is a major cause of morbidity and mortality in the geriatric population. According to Health Canada, myocardial infarction (MI) and ischemic heart disease (IHD) accounted for over one-third of deaths in men and women aged 65 and older in 1995, once again firmly establishing coronary artery disease (CAD) as the leading cause of mortality in Canada. In Ontario, 23 percent of patients die within one year of experiencing MI and one-third of congestive heart failure (CHF) patients succumb within one year of being hospitalized for CHF. Importantly, as Dr. David Naylor, co-editor of the 1999 Institute for Clinical Evaluative Sciences (ICES) Cardiovascular Atlas points out, the Canadian demographic profile is shifting toward a larger geriatric population, potentially greatly increasing the number of Canadians vulnerable to heart disease. Therefore, it is imperative that both primary and secondary prevention methods be used as extensively as possible to reduce the morbidity and mortality due to CAD.

Anna Liachenko, BSc, MSc

A large body of observational evidence suggested that estrogen replacement therapy (ERT) after menopause decreases a women's lifetime risk of death from myocardial infarction by 35 to 50 percent and increases life expectancy by 2 to 3 years. However, a recent major clinical trial concluded that estrogen plus progestin therapy did not decrease the overall risk of myocardial infarction and coronary death among postmenopausal women with previous heart disease. The main question raised by the results of the trial is whether doctors should change their prescribing patterns and which patient populations will be affected. While there is no simple answer, it is important to consider the issues involved such as, How serious were the limitations of the observational research? Did the trial look at the right group of patients? How far can we extrapolate the results? And what are the future implications?

The Heart and Estrogen/progestin Replacement Study (HERS) trial was a randomized, blinded, placebo-controlled trial designed to test the efficacy and safety of hormone replacement therapy (HRT, estrogen plus progestin) on secondary prevention of heart disease. The trial involved 2763 postmenopausal women with established coronary artery disease. In the HRT group, the rate of coronary events increased by 50% in the first year of the trial and subsequently decreased by 40% in the forth and fifth years, yielding no significant effect overall.

Lilia Malkin, BSc

Contrary to popular belief, heart disease is not predominantly a "male" illness: according to Health Canada, nearly 20,000 Canadian women, compared to approximately 24,000 men, died of causes related to ischemic heart disease in 1995.

As awareness of women's vulnerability to cardiovascular disease increases, so does the number of clinical studies that address potential differences between men and women in coronary heart disease (CHD) presentation, course, and treatment. Notably, Dr. Beth Abramson, Director of Women's Cardiovascular Health in the Division of Cardiology at St. Michael's Hospital in Toronto emphasized that there are many issues in cardiology where treatment is irrespective of gender. However, recent research shows that several cardiac health issues may be specific to women, such as risk perception, heart disease presentation, use of diagnostic and treatment procedures, as well as some unique risk factors.

Unfortunately, many North American women do not perceive cardiovascular disease as a considerable health risk and focus their attention predominantly on illnesses affecting reproductive organs, as well as breast cancer. However, CHD is the leading cause of death in Canadian women, especially older women. It is estimated that 1 in 3 North American women will die of heart disease, while 1 in 25 will succumb to breast cancer.