The primary aim of cardiac rehabilitation is to enable the patient to regain full physical, psychological and social status after a cardiac event. Cardiac rehabilitation can optimize the long term prognosis by secondary prevention.
Patient groups for cardiac rehabilitation
Following patient groups may benefit by cardiac rehabilitation programs:
Following an acute cardiac event
Awaiting or post revascularisation
Stable heart failure
Post valve surgery
Post heart transplantation
Post ICD (implantable cardioverter defibrillator) insertion
Benefits of cardiac rehabilitation
Benefits from a cardiac rehabilitation program will include a reduction in angina, blood pressure, anxiety and depression as well as hospital admissions. There is an improvement in the lipid profile, functional capacity, better compliance with lifestyle modification, increase in level of confidence, earlier return to work and leisure activities.
Myocardial effects of exercise
Myocardial oxygen consumption (MO2) depends on the double product. Double product = HR x SBP (heart rate multiplied by systolic blood pressure; double product determines the myocardial work load).
Rise in HR and SBP is determined by the VO2 (oxygen consumption) expressed as a percentage of the VO2max (maximum oxygen consumption) rather than the absolute value of VO2. VO2max increases with exercise training. Hence the rise in heart rate and systolic blood pressure and consequently the myocardial oxygen consumption for a given level of activity decreases as the exercise training program progresses.
1 MET (metabolic equivalent) = 3.5 ml oxygen/Kg/min. 1 MET is the basal metabolic oxygen consumption. Cardiac output can increase almost 6 times with maximal exercise. Oxygen extraction from arterial blood can increase almost 3 times with peak exercise. Hence oxygen consumption can increase about 18 times (VO2max). But in case of coronary circulation, oxygen extraction is maximum even at rest so that increase in oxygen supply can occur only by an increase in flow. A person with maximum exercise capacity of less than 2 METs will be in class IV. Those with an exercise capacity of 2-5 METs will be in class III and those with a capacity between 5-7 METs will be in functional class II. If a person has more than 7 METs of exercise capacity, the functional class will be I.
Phases of cardiac rehabilitation
Conventionally there are 4 phases for cardiac rehabilitation. The first phase starts during the hospital stay for the acute event or surgery. Phase II is after discharge from hospital and is usually carried out at home as per the advice of the rehabilitation team. Phase III, typically after 2-6 weeks, is either at the hospital cardiac rehabilitation facility or a community based program. Phase IV is long term maintenance, most often taken care of by leisure services.
Components of a cardiac rehabilitation program
A comprehensive cardiac rehabilitation program can include proper medications for secondary prevention and symptom limitation, graded exercise programs, advice on healthy eating, including participation in weight loss support groups, relaxation / stress management, general information on the disease process and a training on cardiopulmonary resuscitation for the relatives.
Potential risks of exercise program
Exercise programs do carry risks of worsening of ischemia, left ventricular dysfunction and potential for life threatening arrhythmias. Hence a proper risk stratification is needed prior to initiation of the exercise component of cardiac rehabilitation.
Contraindications to the exercise component of cardiac rehabilitation
Exercise component of the cardiac rehabilitation should be deferred in case of unstable angina, resting BP above 200 / 110 mmhg, significant drop in BP during exercise, resting tachycardia > 100 bpm, uncontrolled atrial or ventricular arrhythmias, unstable heart failure, unstable / uncontrolled diabetes and febrile illness. Program can be resumed after stabilization of these situations.