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Prof. François Carré
In cardiac patients, the benefit of moderate regular exercise far outweigh its risks and must always be encouraged. However cardiovascular events are acutely and transitorily increased during intensive physical exercise. Physicians must 1) evaluate individual risk 2) prescribe an individualised physical activity program 3) provide good patient education. Aerobic exercise must be the most important part of training but well done resistance training must also be encouraged.
Moderate and regular physical activity is beneficial in cardiac patients. However, in the general population, the risk of acute cardiovascular events is transitorily increased during intense exercise and even moreso in the cardiac patient. Data collected from patients in cardiac rehabilitation show that the risk of sudden death is approximately one in 115 00 patients/hour and the risk of acute myocardial infarction is 1/220 000 patients/hour (1).
The most important risk of sudden death is ventricular arrhythmias (≥80%). It is well explained by the physiopathology of arrhythmias. Indeed, we know that ventricular arrhythmias depend on three interrelated factors: 1) arrhythmogenic substrates, which are present in every cardiac patient 2) a trigger - in the present case, it is physical exercise and 3) environmental conditions such as autonomic nervous systems, catecolamines, rehydration, which are altered during exercise.
Regarding myocardial infarction, the risk of plaque dysruption during exercise is increased because of hemodynamic and mechanical constraints are increased and moreover regarding the endothelium, several blood alterations such as oxydative stress, cytokines and inflammation levels are increased.
The physician has two main roles in deciding on exercising modalities. First, he or she must evaluate the patient's individual risk and his physical capacity, second, provide good patient education regarding physical activity.
The cardiovascular evaluation of patients must comprise a clinical examination, with a good history mainly regarding the disease, a physical examination and verification of treatment. Once the clinical examination is completed, if the patient presents as unstable, physical activity will be temporarily excluded. In stable patients, on the other hand, complementary testing is necessary :
The examination of the pulmonary and osteoarticular systems are recommended as they often can be involved in the patients' decision to cease physical activity, with the patient experiencing articular or pulmonary discomfort for example. Regarding resting echocardiography, the right and left ventricles must be examined, and more precisely, ejection fraction, diastolic function and observation of pulmonary hypertension. Regarding exercise testing and CPX tests, they must be conducted while the patient is under usual treatment. In both cases, we look for the presence of ischemia or arrhythmias. Individual physical capacity is only estimated with classical exercise testing, and only CPX tests offer the true value of physical capicity with peak VO2 and individual ventilatory threshold measurements. Moreover, CPX testing will give specific hemodynamic information such as exercise pulmonary hypertension.
Upon the completion of patient evaluation, the patient may be classified into one of three levels of risk (Table 1). Physiological adaptations during dynamic (aerobic) and isometric static exercise in healthy individuals are presented (Figure1).
Table 1 : Low Risk, Moderate and High Risk
Mild symptom at low level of exercise ‹ 5 METs History of cardiac arrest or SD Complicated myocardial infarction or revascularization procedure Ejection fraction ‹ 40 % High level of silent ischemia during exercise Complex ventricular arrhythmias at rest and/or exercise Abnormal exercise hemodynamics Functional capacity ‹ 70 % predicted value
Supervised rehabilitation sessions are recommended for all cardiac patients, except for cardiovascular primary prevention and hypertensive patients. In all cases, regular patient follow-up is required. Certain important recommendations such as refraining from training will be issued to patients in the presence of fever, abnormal asthenia or symptoms. In cases of abnormal symptoms they must visit their physicians before resuming any physical activity. Main physiological cardiovascular adaptations are summarised in figure
Figure 1 : Acute cardiovascular adapations in healthy population during exercise (2).
Regarding dynamic exercise modalities, individual training level intensity can be determined directly with ventilatory threshold from CPX testing. A Borg scale or talk test during classical exercise testing can be used when CPX testing is not available. Positive scoring using the Borg scale is between 12 and 14 on a scale of 6 to 20.
Figure 2 : The Borg scale
Heart rate is the most often used parameter for individual training level testing. Of course, heart rate can only be used in patients with a sinus rhythm. It will be the ventilatory threshold heart rate or a value of ten beats below ischemia heart rate or arrhythmic heart rate. The heart rate is also often used. Target heart rate must be between 60 to 70% of the Karvonen formula (expressed in beats per minute) (Table 2). Lastly, use of heart rate as an individual parameter requires the use of a heart rate monitor. Table 2 : The Karvonen fomula
THR = target heart rate MHR = individual maximal heart rate RHR=individual resting heart rate
Table 3 : Duration, frequency and type of dynamic exercise (4).
Regarding resistance exercise modalities, a light, well-performed exercise program is no longer forbidden in cardiac patients (Myers, Jonathan Journal Heart Failure Review 2008). However, the first sessions must be supervised in order to verify that exercise is well done. Resistance exercise modalities are summarised in Table 4. Table 4: Resistance exercise modalities (5).
In cardiac patients, benefits of moderate regular exercise far outweigh its risks and must always be encouraged. However CV events are acutely and transitorily increased during intensive physical exercise. Physicians must 1) evaluate individual risk 2) prescribe an individualised physical activity program 3) provide good patient education. Aerobic exercise must be the most important part of training but well done resistance training must also be encouraged.
1) Haskell WL, Thompson PD, et al; Physical activity and public health: updated recommendation for adults from the American College of Sports Medicine and the American Heart Association. American College of Sports Medicine; American Heart Association.Circulation. 2007 Aug 28;116(9):1081-93. Epub 2007 Aug 1. 2) Mitchell JH, Haskell W, Snell P, Van Camp SP. Task Force 8: classification of sports. J Am Coll Cardiol. 2005 Apr 19;45(8):1364-7. 3) Tabet JY, Meurin P, Ben Driss A, J Cardiovasc Prev Rehabil. 2006 Aug;13(4):538-43. Determination of exercise training heart rate in patients on beta-blockers after myocardial infarction.
4) Arena R, Myers J, Guazzi M. The clinical and research applications of aerobic capacity and ventilatory efficiency in heart failure: an evidence-based review. Heart Fail Rev. 2008 Jun;13(2):245-69. 5) Williams MA, Haskell WL, Ades PA, Amsterdam EA, Bittner V, Franklin BA, Gulanick M, Laing ST, Stewart KJ; Resistance exercise in individuals with and without cardiovascular disease: 2007 update: a scientific statement from the American Heart Association Council on Clinical Cardiology and Council on Nutrition, Physical Activity, and Metabolism Jul 31;116(5):572-84. Epub 2007 Jul 16.
Dr François Carré is a sports cardiologist at the Centre Hospitalo-Universitaire (CHU) of Rennes, France.
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