Coronary Heart Disease and Exercise:What’s the evidence?

Yeong Yeh LeeMD MRCP(UK) MMed

May 2009

Basics

Exercise & the Heart

Complex circulatory response, resulting in a great increase in cardiac output (CO) proportional to the increased metabolic demands

This is to ensure

1. The metabolic needs of muscle are met,

2. Hyperthermia is avoided and

3. Blood flow to essential organs are protected

HR response to exercise

HR may rise to 160-240 bpm CO increase is more due to an increase in HR

than in SV SV reaches max when CO has increased only

half, further increase in CO is by increasing in HR

Distribution of CO during Exercise The kidney and splanchnic circulation

Extracts 10-25% of O2

The heart Extracts 75% O2

The brain Extracts 25-30% of O2

Distribution of CO during Exercise termination On stopping exercise,

there is marked reduction in HR and CO, mainly from removal of sympathetic drive and reactivation from vagal activity.

However, systemic vascular resistance remains low for some time due to persistence of vasodilation in the muscle vasculature bed.

BP drops and remains lower for upto 12 hrs, BP is stabilized by baroreceptors

CV response to different type of exercises Isotonic exercises (dynamic)

Muscular contraction of large muscle groups that results in movement Primarily places a volume load on the heart Characteristically causes an increase in CO, O2 consumption and a fall in

systemic vascular resistance

Isometric exercises (static) Constant muscle contraction of smaller muscle groups without movement Results more in pressure load than in volume load on the heart Acutely increases systemic vascular resistance and blood pressure while

causing only minimal changes in CO and O2 consumption

Resistance exercises – a combination of the above

Clinical

Coronary Heart Disease

Definition A disease of the

coronary vessels causing stenosis and obstruction of coronary circulation

May be atheromatous or non atheromatous

Risk Factors

HPT Smoking Dyslipdaemia DM Age > 60 y/o Sex – Male &

Postmenopausal women Family history of CHD

Men < 55 y/o Female <65 y/o

Diet Exercise Obesity and weight Estrogen deficiency Homocysteinemia Fibrinogen

Diagnosis

I. Silent angina

II. Stable angina

III. Unstable angina

IV. Non ST elevation MI

V. ST elevation MI

VI. Sudden Cardiac Death

Symptoms

Felt as a pressure, squeezing, constriction, fullness, or heavy weight versus a sharp or stabbing pain

Precordium, all over chest; Not localised Radiate to other areas to the upper abdomen,

shoulders, arms, neck and throat, or lower jaw and teeth

Aggravated with exertion and relieved with rest Is usually not tender, not increased by taking a deep

breath, or by standing or sitting Is not relieved by antacids or food

Symptoms

May be associated with other factors that increase the workload of the heart, such as exposure to cold, emotional stress, sexual intercourse, or meals

Other associated symptomsshortness of breath, belching, nausea, indigestion, sweating,dizziness, lightheadedness, clamminess, or fatigue

Diagnosis

History and Physical Examination ECG Blood test- Cardiac enzymes CK, CKMB,

Troponin T CXR EST Coronary Angiogram

Rx

Non Pharmacological1. Weight loss

2. Low fat diet

3. Exercise

4. Stop smoking

5. Modification of risk factors

Rx

Medical – drugs Thrombolytics Antiplatelets Anticoagulants Nitrates Beta Blockers Calcium Channel

Blockers

Angiotensin Converting Enzyme inhibitors

Lipid lowering agents – fibrates, HMG Co A inhibitors

Oxygen

Rx

Interventional Cardiology Balloon Angioplasty Stenting

Surgery CABG surgery

Others Growing new vessels Etc

Trials

CHD & Exercise

Inadequate physical activity has been recognized as an independent risk factor for premature development of CHD

Physical inactivity is associated with at least a twofold increase in the risk for coronary events

Powell KE et al Annu Rev Public Health 1987; 8:253

The medical profession supports the concept of reduction of CHD via exercises through recommendation of regular physical exercise both as a primary and as a secondary measure.

CHD & Exercise

The evidence is thus far inadequateinadequate Problems :1. Adherence to study protocol;

it is not possible from an ethical or practical standpoint to prevent those assigned to the control group from engaging in exercise (drop-ins).

noncompliance (drop-outs).  2. The randomized trials which have been carried out have

had inadequate numbers of patients to show a significant benefit.

CHD & Exercise

There is a transient increased risk of sudden death among healthy subjects associated with an episode of vigorous exercise, the AR of sudden death during any particular episode of exercsie is low (1 per 1.51 million episodes of exercise)

Habitual exercise diminishes the risk of sudden death even further, and overall the benefits of exercise outweigh the small risks.

Albert CM et al Physician Health study N Engl J Med 2000; 343:1355.

CHD & Exercise

Much of the evidence for the benefit of exercise comes from long-term observational studies showing that those who exercise regularly have significantly less CHD and a reduced risk of primary cardiac arrest

Lemaitre RN et al Arch Intern Med 1999; 159:686.

Despite these limitations, regular exercise can be justified on its own merits.

CHD & Exercise -benefits

Improvement in cardiovascular and general physical fitness and an overall enhancement in the quality of life are ample reasons to embrace physical exercise

Beneficial effects on weight control and several other important cardiovascular risk factors

Fletcher GF et al. Statement on exercise: Benefits and recommendations for physical activity programs for all Americans. A statement for health professionals by the Committee on Exercise and Cardiac Rehabilitation of the Council in Clinical Cardiology, American Heart Association. Circulation 1996; 94:857.

Fletcher GF et al. Exercise standards. A statement for healthcare professionals from the American Heart Association. Circulation 1995;91:580

CHD & Exercise – Additional benefits1. Lipid profile 2. Blood pressure 3. Rx and possible prevention of type 2 DM4. Enhancement of endothelium-dependent

dilation(increased release of nitric oxide in young normotensive and hypertensive

men)

5. Reduction of atherogenic activity (decrease in the production of atherogenic cytokines and an increase in

atheroprotective cytokines )

CHD & Exercise – Additional benefits5. Antithrombotic effect

(reduction in plasma fibrinogen and plasminogen activator inhibitor and an increase in tissue plasminogen activiator)

6. Improvement in autonomic function (increase in baroreflex sensitivity and HR variability d/t reduction in sympathetic

tone and catecholamine release)

7. Anti-ischemic effect (an improvement in the balance between myocardial oxygen supply and

demand by reduction in HR and BP which decreases myocardial work)

8. Antiarrhythmic effects(which possibly result from the anti-ischemic benefits and improved autonomic

function)

PRIMARY PREVENTION

PRIMARY PREVENTION

A number of studies have shown a strong inverse relationship between habitual exercise and fitness and the risk of coronary disease and death

Although most observations were made in men, a similar cardiovascular benefit from fitness in women has been found in women

Harvard alumni health studyPaffenberger et al. NEJM 1993; 328:538.Sesso et al Circ 2000; 102:975.Lee et al Circ 2000; 102:981

Physical activity habits were analyzed in 10,269 Harvard alumni in a retrospective study over 12 years

Those men who engaged in moderately vigorous sports activity (defined as total physical activity levels >4200 kJ/week or brisk walking, recreational cycling or swimming, home repair, and yard work for 30 min/day on most days) had a 23 percent lower risk of death than those who were less active.

The improvement in survival with exercise was equivalent and additive to other lifestyle measures such as cessation of smoking, control of hypertension, and avoidance of obesity

This reduction in risk was also seen in men with multiple coronary risk factors

Changes in physical fitness and all-cause mortality.

A prospective study of healthy and unhealthy men. Blair JAMA 1995; 273:1093.

Another study prospectively evaluated 9777 men with two clinical examinations (mean interval between examinations, 4.9 years) to assess the association of change or lack of change in physical fitness with the risk of mortality during a mean 5.1 year follow-up after the second examination

The age-adjusted all-cause death rate was approximately three times higher in men who were unfit at both examinations compared to those who were physically fit at both examinations (122 versus 40 per 10,000 man-years).

An intermediate rate (68 per 10,000 man-years) occurred in men who improved from unfit to fit between the first and subsequent examinations.

Finnish Twin Cohort study Kujala et al. JAMA 1998; 279:440

The Finnish Twin Cohort study of almost 8000 same sex twin pairs

Odds ratio for death of 0.66 in occasional exercisers and 0.44 in conditioning exercisers compared with their sedentary twins

Nurses' Health studyManson JE at al NEJM 1999; 341:650. Lee IM et al JAMA 2001; 285:1447

The Nurses' Health study of 72,488 women between 40 to 65 years of age found that brisk walking or vigorous exercise were inversely related to the risk of a coronary event;

In a multivariate analysis, women in increasing quintile groups for energy expenditure had age-adjusted relative risks for coronary events of 0.88, 0.81, 0.74, and 0.66, indicating a graded benefit from exercise

Sedentary women who became active in mid life or later had a lower incidence of coronary events compared to those who remained active.

Healthy women also benefit from light to moderate exercise; the benefit is again related to the duration of exercise

American Heart Association (AHA)Circulation 1997; 96:355

Based upon these and other observations, the American Heart Association (AHA) has issued a Science Advisory on implementation of physical activity in primary and secondary prevention

It recommends institution of regular physical activity in the early school years and throughout life. Physicians are advised to provide exercise prescriptions to patients including plans for activities when on business trips and vacation.

SECONDARY PREVENTION

SECONDARY PREVENTION –

There are a number of observational studies suggesting that exercise and fitness are also beneficial in patients who have coronary heart disease

Wannamethee studied 772 men (mean age 63) with documented coronary heart disease who were followed for up to five years

He found that the lowest incidence of all-cause and cardiovascular mortality was seen in those who engaged in light and moderate activity; this activity included recreational (nonsporting) activity (> or =4 hours/week), regular walking (>40 min/day), or moderate or heavy gardening (adjusted relative risk 0.42 and 0.47 compared to inactivity or occasional light activity)

Circulation 2000; 102:1358

Meta analysisOldridge et al. Cardiac rehabilitation after myocardial infarction. Combined experience of randomized clinical trials. JAMA 1988; 260:945.

A meta analysis of ten trials of exercise and risk factor reduction among survivors of acute MI demonstrated a 24 percent reduction in all-cause mortality and a 25 percent reduction in cardiovascular death

No difference was shown for nonfatal myocardial infarction. These results support a comprehensive rehabilitation program but

do not separate the benefit of exercise from other risk factor interventions.

National Exercise and Heart Disease Project Circulation 1999; 100:1764Am J Cardiol 1981; 48:39

The protective effect of exercise may be short lived. This was illustrated in the results of the National Exercise and Heart Disease Project, a three year supervised exercise program that randomized 651 men with a myocardial infarction to a regular exercise program or no exercise

After a three year follow-up, there was a nonsignificant 37 percent reduction in mortality in those who exercised (4.6 versus 7.3 for the no exercise group)

There was no difference in the incidence of myocardial infarction. The benefit of exercise on mortality diminished as time since participation

increased; the relative risk for exercisers compared to non-exercisers at 10, 15 and 19 years was 0.95, 1.02, and 1.09, respectively and the same trend was seen for cardiovascular mortality

American Heart Association (AHA) The AHA guidelines on physical activity in

secondary prevention after myocardial infarction (MI), bypass surgery and clinical ischemia recommend attendance at supervised facilities where symptoms, heart rate, and blood pressure can be monitored

A symptom-limited exercise test is essential in all patients before starting an exercise program.

THE EXERCISE PRESCRIPTION

Practical recommendations for exercise programs and for classification of exercise risk, which determine the need for supervision and monitoring, have recently been published

Primary Prevention

a life-long appropriate physical activity would be 30 to 60 minutes of exercise, 30 to 60 minutes of exercise, four to six times a weekfour to six times a week.

Endpoints indicating an adequate degree of exercise include:

BreathlessnessBreathlessness FatigueFatigue SweatingSweating

Achievement of goal heart rate is not necessary

Primary Prevention

Exercise can be performed for short periods several times a day and integrated into the course of one's daily life.

The focus is on total aerobic activity, which should amount to at least 30 minutes a day, at least five days a week.

Examples of lifestyle exercise are brisk walking at 4.8 to 6.4 km (3 to 4 miles) per hour for most healthy adults, active yard work, and dancing

Exercises such as bicycling, jogging, and other leisure sports can also be performed.

Aerobic exercise may be sustained or intermittent such as walking up stairs.

In addition, resistive exercises with free weights or exercise equipment consisting of 10 to 15 repetitions of each exercise for arms, shoulders, chest, trunk, back, hips and legs should be carried out two to three times a week.

Secondary prevention

The degree of activity depends upon an assessment of risk, such as the presence or absence of ischemia, arrhythmia, or heart failure.

Secondary prevention

Summarized briefly, Early activity after an MI can include walking and

range of motion exercises. Late activity depends upon the level of risk:

1. Low-risk patients with no ischemia or arrhythmia should exercise under supervision to achieve a heart rate 60 to 80 percent of the heart-rate reserve (maximal minus resting heart rate) above the resting heart rate. With training and increased tolerance, the intensity of exercise can be increased and eventually include resistance exercise with relatively low risk.

2. High-risk patients with ischemia or arrhythmia require close supervision to achieve a heart rate at least ten beats per minute below the rate associated with the abnormality.

Conclusion

1. Exercise has been classified as a category II intervention

2. Intervention against physical inactivity is "likely to lower" cardiovascular disease risk based upon strong, consistent epidemiologic evidence and moderately strong supporting evidence from clinical trials.