Appropriately prescribed exercise is indicated for most people with a clinically stable heart condition after relevant screening. Conditions where exercise is contra-indicated or should be undertaken with caution, are detailed in the table below. In most instances, light-to-moderate intensity exercise offers a very high benefit-to-risk ratio, and is much safer than a prolonged sedentary lifestyle. However, some cardiovascular conditions require stabilisation and further medical intervention before exercise can safely be performed. Also see Guidelines for exercise program participation regarding indications for program entry and details on programming for different clinical conditions.

Table 1: Conditions where exercise is contra-indicated

bpm = beats per minute; HR = heart rate, METS = metabolic equivalents, NYHA = New York Heart Association, W = watts

Adapted from the American Association of Cardiovascular and Pulmonary Rehabilitation Guidelines for Cardiac Rehabilitation and Secondary Prevention Programs[#american-association-of-cardiovascular-and-pulmonary-rehabilitation.-2013]

Risk stratification is a means of ensuring the benefits from regular exercise clearly outweigh the risk of adverse events during exercise. A number of respected authorities, including the American College of Sports Medicine,[#american-college-of-sports-medicine.-2013] provide detailed criteria. The risk of an exercise-related cardiac event is commonly divided into low, moderate and high categories.

Important notes about risk stratification:

• Clinical risk may change quickly and therefore should be reviewed at each supervised exercise session
• Classification of risk is not always clear cut and many individuals may straddle categories. When in doubt, seek medical advice and apply a higher risk category until proven otherwise
• Patients who have any of the high-risk criteria should ideally commence exercise in a hospital-based program, if available. However, many patients may be unable or unwilling to do this, in which case a conservative exercise schedule in a community environment may be appropriate
• If not all necessary information is available for comprehensive risk stratification, the default approach should be to treat apparently low-risk patients as high risk, prescribing exercise conservatively at first. In cases already known to be high risk, delay exercise prescription until the required further information is obtained

TIP: Never assume risk is static, or that the most recent clinical presentation which was a long time ago suggests low risk. Risk may increase over time due to disease progression or clinical deterioration. When in doubt, seek medical advice.

Low risk (all must be present in order to consider low risk):

• Resting ejection fraction ≥50%
• Uncomplicated MI or revascularisation procedure
• Absence of complicated ventricular arrhythmias at rest or during exercise
• Absence of signs or symptoms of post-event/procedural ischaemia
• No untreated coronary lesion >50% on angiography
• Normal haemodynamics during exercise testing and recovery (i.e., appropriate increases and decreases in HR and systolic BP with increasing workloads and recovery)

Moderate risk (any of these findings places patient as at least moderate risk):

• Ejection fraction 30-50%
• Ejection fraction <30% with an implantable cardioverter defibrillator (ICD) in situ
• Untreated coronary lesion of 50-70% on angiography

High risk (any of these findings places patient at high risk):

• Ejection fraction < 30% without an ICD
• Untreated coronary lesion > 70% on angiography
• History of cardiac arrest
• Complex arrhythmias at rest or exercise
• Complicated MI or revascularisation procedure
• NYHA classification functional class III-IV symptoms
• Congestive HF requiring hospitalisation in the past 2 months
• Unstable or exercise-induced angina in the past 2 months
• Non-cardiac vascular events in the past 2 months
• Complex congenital heart disease associated with oxygen desaturation at rest or during exercise
• Silent ischaemia (ECG changes during exercise testing in the absence of symptoms)
• Advanced renal failure

Adapted from the American Association of Cardiovascular and Pulmonary Rehabilitation Guidelines for Cardiac Rehabilitation and Secondary Prevention Programs[#american-association-of-cardiovascular-and-pulmonary-rehabilitation.-2013] to assist clinical reasoning when deciding risk for cardiovascular complications relating to exercise.

Patients recognised as 'high risk' may not always be 'high risk' and it is important to note that a low ejection fraction does not imply poor exercise tolerance due to poor correlation in peripherally well-compensated individuals.

Categories of risk are a guide only and should always be combined with a clinical judgement of exercise tolerance.

For patients with HF, despite historical concerns regarding the effect of hydrostatic pressure on left ventricular filling pressure and preload, recent evidence suggests that aquatic exercise performed in thermo-neutral water (32-34°C) to the level of the xiphisternum is safe in appropriately selected  patients.[#caminiti-g-volterrani-m-marazzi-g-et-al.-2011]

Aquatic exercise improves exercise capacity, muscle strength and quality of life, and may provide an effective alternative for those unable to participate in traditional land-based programs.[#adsett-j-mudge-a-morris-n-et-al.-2015]

Current evidence suggests avoiding aquatic exercise for those with biventricular HF and/ or pulmonary hypertension. Decompensated HF remains an absolute contraindication.

There are currently no published guidelines with respect to swimming and HF due to the lack of specific research in this area. Clinicians should therefore use clinical judgement when advising patients about swimming, and supervision may be recommended for certain individuals. 

See water-based exercise and heart conditions.

Prescribed cardiac medications may impact on exercise response and medication titration commonly affects exercise tolerance.  While angiotensin-converting enzyme (ACE) inhibitors, beta-blockers, digoxin and nitrates tend to improve functional capacity in the longer term, dose increases often cause a transient decrease in exercise tolerance.

Symptoms such as dizziness, increased dyspnoea and fatigue may necessitate a temporary reduction in exercise intensity and duration until the patient adapts and symptoms resolve. Persistent symptoms following up-titration of medication may warrant returning to the previous dose at the discretion of the supervising doctor.

Impaired thermoregulation is a consequence of the reduced cardiac reserve in HF patients, and many notice a dramatic decrease in exercise tolerance in hot or humid conditions.

Common medications such as beta-blockers, anti-adrenergic agents and diuretics may exacerbate the problem. Therefore, the exercise prescription should be modulated in hot weather. Patients may be required to relax their fluid restriction slightly and should wear appropriate clothing to facilitate heat loss and to aid evaporative cooling through sweating. Exercise and manual activities outdoors should be avoided on hot days.

HF is characterised by fluctuations in clinical status, with periods of decompensation occurring more frequently as the condition progresses. The decrease in exercise tolerance may be quite profound and require hospitalisation. In some instances, exercise may need to be substantially reduced or avoided completely. After medical clearance, exercise can be gradually re-introduced and the patient encouraged to progress toward optimal levels as tolerated.

Some cardiac patients with advanced disease or co-existing respiratory disease may benefit from supplemental oxygen during exercise training. Recording oxygen saturation will help determine this need. Patients on long-term oxygen therapy should always train with supplemental oxygen. Oxygen should only be prescribed by those with knowledge and experience in this field. 

If unwell, patients should refrain from exercising until their symptoms resolve and they can then gradually re-introduce their exercise program. A rule of thumb is to spend the same length of time gradually building back up to pre-ailment levels of exercise as the period of the ailment.

Patients with HF are particularly susceptible to common infections, which can lead to rapid and substantial deterioration in their exercise capacity. Accordingly, these patients should routinely receive the flu vaccine. 

TIP: Many factors can disrupt exercise programs in patients, requiring a decrease in intensity or even a temporary cessation of exercise. As soon as the condition is stabilised, recommend exercise to be restarted at a reduced intensity and then build from there.

Exercise prescription for patients with cardiac disease should consider common co-morbidities including:

• Other cardiac conditions such as Ischaemic heart disease and a arrhythmias
• Diabetes
• Chronic respiratory disease (see The Australian Lung Foundation Pulmonary Rehabilitation Toolkit)
• Peripheral vascular disease
• Musculoskeletal disorders

See also co-morbidities and related conditions.