SINGAPORE - Exercise is good for the heart - even for people who have had a heart attack, been diagnosed with cardiovascular disease (narrowing of the heart arteries) or heart failure.
What exercise cannot do is increase their heart function - how efficiently and powerfully the heart can work to pump blood around the body - in the long term.
Nor can exercise reverse the damage caused to the heart muscles by a heart attack or cardiovascular disease.
But exercise for this group of patients has been proven to be cardio-protective, preventing further damage to the heart and strengthening the organ, said Adjunct Assistant Professor Tong Khim Leng of Yong Loo Lin School of Medicine at National University of Singapore, and chief of the department of cardiology at Changi General Hospital.
Exercise also helps to prevent recurrent heart attacks. It does this by improving the function of the endothelium, the innermost lining of the blood vessels, explained Dr Jason Chia, head of the Sports Medicine & Surgery Clinic at Tan Tock Seng Hospital.
The endothelium is affected when fat deposits accumulate on it, causing the arteries to harden and making it harder for blood to flow through them.
Studies show that exercise can reduce the risk of such plaque forming on the endothelium.
With its direct benefit to the blood vessels and overall cardiovascular fitness, exercise will help speed up recovery for heart patients and lower the risk of a second heart attack for those who have had a prior attack.
Prof Tong said cardiovascular exercise can, in fact, extend the survival of many heart patients, reducing the chance of adverse cardiovascular events, including heart attacks, by as much as 20 per cent.
For someone who has ischaemic heart disease - where there is reduced blood flow to the heart muscles causing part of them to die -- exercise is a form of lifestyle modification that has multiple benefits such as lowering cholesterol, keeping weight gain at bay, improving diabetes control and keeping a person happy, said Prof Tong, who is a sports cardiologist.
HOW MUCH TO DO
Having said that, people at risk of a heart attack should bear in mind that over-strenuous and excessive training, especially in previously sedentary individuals, can sometimes trigger an attack, she said.
"This is why one needs to pay attention to one's body and look out for all the warning symptoms," she said.
These include chest pain, dizziness, palpitations, fainting and unaccustomed breathlessness. But the benefits of exercise outweigh the risk of death.
Heart patients, who have suffered a recent heart attack, or who have undergone recent procedures such as coronary angioplasty and coronary artery bypass surgery, are encouraged to enrol in cardiac rehabilitation programmes tailored for them.
"These programmes allow these recuperating patients to gradually restore their functional capacities, in a safe, supervised environment, within an inpatient or outpatient hospital setting," said Prof Tong.
The intensity of aerobic exercise needs to be tailored to the person's fitness level, said Dr Chia, and the heart disease should also be stable and controlled.
Only after about six weeks to three months, when they are comfortable with the routine, do doctors recommend that patients continue the exercise by themselves, said Prof Tong.
For others with milder heart conditions who are allowed by their doctors to exercise, they should start gently with low-intensity exercises, such as walking, she added.
They can start with five- to 10-minute sessions of walking each day, five days a week.
The duration can be slowly increased by one to five minutes per session or 10 to 20 per cent more each successive week, until they can get to the recommended target of 150 minutes of moderateintensity exercise a week, said Prof Tong.
Moderate intensity means the person can still talk in short sentences, but cannot sing, while doing the exercise.
"I usually suggest that each exercise session last between 20 and 60 minutes," said Prof Tong.
Aerobic exercise is the mainstay, but can be supplemented by resistance exercise, such as weight training.
EXERCISING ON MEDICATION
Patients should continue to take their medication while exercising. In fact, for patients with ischaemic heart disease that reduces blood flow to the heart muscles, it is important that they do not skip their medication before exercising, said Prof Tong.
Patients should also always ensure that they have their vasodilators on them, she said. Many heart patients are familiar with glyceryl tri-nitrate (GTN) vasodilator medication, she added.
These drugs dilate the artery walls, prevent muscles from tightening and the walls from narrowing.
As a result, blood flows more easily through the arteries and improves blood supply to the heart.
Patients should take such medication when they feel chest discomfort, which can manifest as chest tightness or pain.
On the other hand, some drugs that treat hypertension may affect the body's heart-rate response to exercise and aggravate post-exercise hypotension (low blood pressure), which may cause dizziness and weakness.
An extended cooling down period after one's workout is recommended to avoid this, said Prof Tong.
Some types of medication may also affect the response of the heart rate to exercise.
For instance, when a heart patient is on a beta-blocker drug, it weakens the heart-rate response to exercise.
"Then the heart-rate response to exercise is not reliable," said Prof Tong.
For such patients, the heart-rate targets are usually based on exercise tests performed while on medication.
For those without prior exercise testing, Prof Tong suggests starting gently, with their target exercise heart rate taken as their resting heart rate plus another 20 beats per minute.
They can then increase it slowly as long as they feel fine.
Other types of medication, such as diuretics, which increase the volume of urine, may affect the body's control of water and electrolyte balance. Electrolytes are chemicals in the body that regulate important physiological functions.
For these patients, doctors will monitor their water and electrolyte levels as well as control their fluid intake and exercise environment.
For instance, it would be preferable for these patients to exercise in cooler places, so they do not become dehydrated.
As not all heart patients are suitable for exercise, they should consult their doctors first before starting any exercise programme on their own.
For example, exercise is not advisable for severe heart conditions such as uncontrolled heart failure or hypertension, heart rhythm abnormalities or residual significant narrowing of heart arteries, said Prof Tong.
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