Exercise as it relates to Disease/Survival of Coronary Patients: Surgery versus Exercise Interventions

A critical analysis of the article "Percutaneous Coronary Angioplasty Compared With Exercise Training in Patients With Stable Coronary Artery Disease" by Hambrecht, R et al.

This has been created by u3117317. '

=Background=

What is Coronary Heart (artery) Disease?
Coronary artery disease (CAD) is a leading cause of death and is commonly the source of angina (chest pain) and heart attacks. It is triggered by atherosclerotic plaque build-up on the inside of artery walls. This narrows and even blocks the blood vessels, decreasing blood supply to the heart.

Prevalence
According to the Australian Bureau of Statistics heart disease is one of the leading causes of death worldwide. In 2011, CAD contributed to 15% of all deaths in Australia and accounted for almost 1 in 2 cardiovascular disease deaths.

Risk factors of CAD

 * High blood cholesterol/blood pressure
 * Diabetes
 * Obesity
 * Smoking
 * Physical inactivity

Surgery, Exercise and CAD
Advances in surgical strategies have made percutaneous coronary intervention (PCI) with stent implantation a treatment of choice among CAD patients. PCI is a procedure in which a thin flexible tube inserts a stent to improve blood flow through vessels that have been narrowed by plaque buildup. Studies have shown that regular exercise for stable CAD patients improves blood flow through the heart and inhibits progression of CAD. Results from Hambrecht's study compare the intervention methods described above. Cost of PCI surgery is a barrier to recovery for patients with CAD. This article provides the reader strategies to combat CAD without the cost of surgery.

=The Study at Hand=

Where is the research from?
This study originates from Lepzig University. It was written in correspondence with Rainer Hambrecht a Professor of Medicine, and was published by the American Heart Association in March 2004.

What kind of study is it?
This study was a randomised controlled trial in which a total of 101 male patients aged 70 years and over were employed following a routine coronary angiography and randomly assigned to either 12 months of exercise training or to PCI. Randomised trials aim to distribute participants randomly into different conditions. They are often considered one of the higher standards for clinical research. The study was carried out between March 1997 and March 2001.

What did the research involve?
Male patients were clinically tested (for stable CAD) and chosen to participate in the study, only participants who lived within a 25 km radius of the institution were chosen for practicality. Patients were randomly assigned either stent angioplasty (PCI) or exercise training by drawing an envelope with the treatment assignment enclosed.

Interventions
Two interventions were used, PCI surgery involved the implantation of a stent into problem arteries. The exercise training program involved an initial supervised stage where patients exercised for 10 minuted 6 times a day on a bicycle ergometer at 70% of the symptom-limited maximal HR. Patients were then asked to exercise on the bicycle ergometer close to their symptom-limited maximal HR for 20 minutes per day and to participate in one 60-minute group training session per week.

Assessments of clinical status
Assessments were performed prior to intervention and again after 12 months of prescribed treatment:
 * Myocardial scintigraphy → An examination of cardiac muscle assessed how blood flows though the heart.
 * Cardiac catharization → Insertion of a thin flexible tube into arteries to assess results of coronary intervention in the PCI group and progression of CAD in both groups. Cardiac catheterization provides accurate and detailed information when compared to other diagnostic tests.
 * Scoring system of disease progression → A narrowing of vessels <10% was classified as unchanged. A decrease in diameter of the vessel of >10% was graded as regression and an increase of >10% was graded as progression.

Survival rates
The number of ischemic events within each group determined survival.

Ischemic events were defined as one of the following:
 * Death of cardiac cause
 * Stroke
 * Resuscitation after cardiac arrest
 * Coronary artery bypass grafting (CABG)
 * Angioplasty
 * Worsening angina that resulted in hospitalisation

Cost effectiveness
Calculation of cost-effectiveness was based on the total cost of the intervention.

=Results= In both groups, clinical symptoms improved significantly during the study period.

Survival rates: Disease progression: Cost per year of intervention:
 * Event-free survival of 70% in the PCI group
 * Event-free survival of 88% in the training group
 * Patients in the exercise training group showed a mean progression of 0.30±0.
 * Patients in the PCI group showed a mean progression of 0.81±0.20
 * $6086±370 per PCI patient
 * $3708±156 per exercise training patient

=Conclusions= When compared to PCI, regular exercise resulted in better event-free survival rates at lower cost. Such conclusions were drawn from lower incidence of rehospitalisation and increased vascularisation in patients assigned to the exercise intervention.

This study has clear limitations: Essentially, the sample used is not an accurate representation of all CAD patients.
 * No control group was used so there were no baseline results for either intervention.
 * Only participants living within a 25-km radius of the institution were involved. Therefore, the living status of participants may not be representative all CAD patients.
 * Only male participants with stable CAD were involved in the study.

Replication of such a study is unlikely. The investigational protocol for this study was approved by the ethics committee for human studies at the University of Leipzig. However, present day ethics committees are unlikely to approve another trial of this type, as it is unethical to put the likelihood of survival up to chance.

=Practical Advice= The sample used for this study is not representative of all CAD patients, thus exercise in female and unstable CAD patients may not have the same outcomes. It is crucial to consider the severity of CAD when prescribing exercise interventions. A qualified medical practitioner should evaluate CAD patients prior to engaging in any exercise program. Patients identified as high risk for cardiovascular complications during exercise should defer exercise training until problems are controlled.

This study highlights methods to combat CAD after it presents, however measures to decrease risk of developing CAD should be a priority. Physical activity is a recognised preventative measure for atherosclerosis. The Australian Physical Activity guidelines recommends accumulating 150–300 minutes of moderate intensity or 75– 150 minutes of vigorous physical activity or an equivalent combination each week. Dietary intake impacts risk of CAD, and according to the National Cholesterol Education Program the most important dietary recommendations are as follows: Smoking increases CAD risk and should be avoided, including exposure to secondhand smoke.
 * Body mass index below 25 kg/m2.
 * Consume <10% of energy from saturated fat and <2% from trans fat.
 * Eat fish at least once a week.
 * Eat ≥400 g of vegetables/fruits per day.
 * Limit salt consumption to <6 g/d.

Further resources
For further information on CAD follow the links below:
 * Heart Foundation: http://heartfoundation.org.au/about-us/what-we-do/heart-disease-in-australia
 * Nutrition Australia: Nutrition and Cardiovascular disease: http://www.nutritionaustralia.org/national/resource/cardiovascular-health

References: