Main Messages
Chapter 12: The Molecular Base of Exercise
The pathogenesis of exercise intolerance in car- diovascular diseases is more complex than previ- ously thought. In coronary artery disease (CAD) it was commonly believed that the degree of epicar- dial coronary stenoses correlated with the sever- ity of myocardial ischemia. This is, however, not necessarily the case. With the increasing knowl- edge about endothelial dysfunction it has become evident that even mild stenoses may cause criti- cal ischemia when combined with pathologic endothelial vasoconstriction in response to cate- cholamines or exposure to cold temperatures.
Basically, regional myocardial hypoperfusion in CAD results from a combination of four basic pathogenetic components: vascular stenosis, coro- nary vasomotion, microrheology and hemostasis, and mobilization of endothelial progenitor cells (EPCs). Exercise training has the potential to affect all components. Although regression of vas- cular stenoses is rarely observed, exercise clearly retards the progression of atherosclerotic lesions.
Endothelial function is dramatically improved by training interventions as a result of increased expression/activation of the key enzyme endothe- lial nitric oxide synthase (eNOS) and reduction of reactive oxygen species. Microrheology is improved and hemostasis reduced. Novel data from both animal experiments and clinical studies indicate that exercise enhances the release of EPCs from the bone marrow into the circulation. These cells contribute to the formation of new vessels in
ischemic tissue areas and repair endothelial lesions in atherosclerotic vessels.
In chronic heart failure (CHF) the degree of left ventricular dysfunction is unrelated to the extent of exercise intolerance. Peripheral factors like the neurohormonal system, endothelial dysfunction, and an inflammatory peripheral myopathy play a much greater role in determining the exercise limitations associated with CHF. Exercise training programs favorably affect neurohormonal activa- tion by reducing circulating catecholamines, angiotensin II, and aldosterone by up to one-third.
Endothelial function is significantly improved, leading to reduced peripheral resistance and a hemodynamically relevant afterload reduction.
Finally, the inflammatory/catabolic activation found in skeletal muscle biopsies of patients with CHF is reversed and muscle wasting halted by endurance training programs.
Thus, in both CAD and CHF exercise-based interventions have the potential to interfere with the underlying disease processes and to improve the patient’s prognosis.
Chapter 13: Exercise and Fitness
The body of epidemiologic research demonstrat- ing the health benefits of physical activity spans more than five decades. A sedentary lifestyle, lack of physical fitness, or both, are major precursors for cardiovascular disease (CVD). Even relatively modest increases in levels of fitness or physical activity patterns are associated with substantial health benefits. However, in countries that have reported evidence supporting the role of physical
Section II
Exercise Testing in Heart Disease
66 Exercise Testing in Heart Disease
activity in health the majority of citizens do not get enough physical activity to achieve health benefits. Likewise, only a small percentage of pa- tients who are eligible for cardiac rehabilitation are referred to a program.
The state of being sedentary and low levels of fitness are in and of themselves CVD risk factors.
Therefore, mechanisms underlying the health benefits of regular exercise include counteracting the state of being sedentary, and the potential increases in fitness level that occur with activity.
Other mechanisms are the favorable influence on CVD risk, including reductions in blood pres- sure and body weight, improved lipid profile, inflammatory markers and insulin sensitivity.
Exercise training appears to have a profound effect on endothelial dysfunction and thus on the vasodilatory properties of the vasculature.
Western societies have become more sedentary in the last two decades, which has led to an increase in the prevalence of several chronic con- ditions. Efforts are required from government agencies, healthcare providers, and health organi- zations in order to offset this trend. This chapter provides an overview of the epidemiologic evi- dence associating physical activity and fitness level with better health outcomes, and the physio- logic benefits of activity.
Chapter 14: Exercise Testing in Coronary Heart Disease
Exercise testing is probably the most often per- formed diagnostic test for persons with suspected coronary heart disease. It provides not only infor- mation about ST-segment depression, heart rate, and blood pressure during and after exercise but more importantly information also on the overall exercise performance in relation to the expected performance adjusted for age and gender, which is of greater prognostic importance than a limited look at the ST segments. Exercise testing provides additional prognostic information particularly in persons with an intermediate pretest probabil- ity of disease. This chapter provides a thorough overview of the different types of exercise testing from treadmill exercise to different imaging modalities, and is aimed at the interested new-
comer in this area as well as the expert, already familiar with the details of the most recent modifications. Introduction to exercise testing is an introduction to cardiology!
Chapter 15: Cardiopulmonary Exercise Testing in Chronic Heart Failure
Cardiopulmonary exercise testing (CPX) provides major insights regarding the degree of functional impairment, the overall circulatory response to exercise, the prognosis, and the effect of treatment in patients with heart failure. Although peak oxygen uptake (peak VO2) is the most important variable used to evaluate exercise capacity and prognosis, CPX provides a lot of information besides peak VO2. This chapter gives clues on how to utilize this information, which now has an important place in the evaluation of the patient with heart failure. It is a rather inexpensive and safe procedure with the potential to provide infor- mation that is of key importance for these patients and their physicians: how much oxygen can be delivered to the tissues and what are the potential best treatment modalities?
Chapter 16: Exercise Testing in Valvular Heart Disease
Although more often performed in patients with suspected or proven coronary artery disease, exercise testing is also of great value in patients with valvular heart disease. It has an important role in eliciting symptoms in asymptomatic patients, in evaluating atypical symptoms, and in assessing true exercise capacity. Exercise testing is not only of prognostic importance but is also useful for advising patients about their physical activities and exercise limits. It also gives clues about where and how to start medical therapy (heart rate or blood pressure control). After valve interventions or valve surgery an exercise test is advised prior to starting an exercise training program, to assess its safety but also to evaluate the medical management. Exercise testing should be used more often to optimize clinical management in patients with valvular heart disease.
