Efficacy of Early Short-term Training on Thrombogenesis in Patients Following Coronary Bypass Surgery

Introduction

The American College of Cardiology/American Heart Association guidelines suggested that cardiac rehabilitation (CR) should be offered to all eligible patients after coronary bypass surgery (CABG).[1] However, CR use in America is relatively low among Medicare beneficiaries despite convincing evidence of its benefits and recommendations for its use by professional organizations.[2] This neglect is as well evident in Taiwan. Traffic inconvenience and unavailability due to working hours are the common causes. There are ways to mend this situation. One of them is to develop an early, intensive and short-term CR program. The current investigation will adopt an early, intensive and supervised training for male patients following elective CABG due to old myocardial infarction and/or angina pectoris.

Meta-analyses of randomized controlled trials have consistently shown that participation in CR programs improves mortality and morbidity outcomes. It also benefits cardiopulmonary fitness, quality of life, lipid profile, etc.[3] Nonetheless, research regarding its effect on balance of thrombogenesis at rest or in response to vigorous exercise is either incomplete or controversial.

Previous studies found that acute physical exertion may trigger an acute coronary syndrome. The relative risk of cardiac events was 2-6 times higher during strenuous physical exertion (>6 METs) compared with during mild to moderate intensity activities in cardiac patients.[4] One of the possible explanations for this is that acute physical exertion may acutely change the hemostatic milieu in favor of increased coagulation and activation of platelet.[5] Available evidence suggests that strenuous exercise, in both healthy subjects and in various cardiovascular disease states, is associated with activation of platelets and blood coagulation, leading to a prothrombotic or hypercoagulable state.[6, 7] Aspirin is ineffective in attenuating enhanced platelet aggregation and activation induced by exercise.[8]

Regular physical exercise is associated with overall reduced risk of primary cardiac arrest.[4] D Wosornu et al. showed that a three-month aerobic training program (3 sessions per week) decreased resting fibrinogen concentration.[9] A meta-analysis showed that an exercise intervention over 2 weeks is associated with reduced inflammatory activity in patients with coronary artery disease (CAD). C-reactive protein and fibrinogen have provided the strongest evidence.[10] Platelet activation by strenuous exercise has been studied in 12 physically active and 12 sedentary individuals before and after a standardized treadmill exercise test. Among sedentary subjects, exercise caused an augmentation of the platelet activation and reactivity. In contrast, in physically active subjects exercise failed to induce alteration in platelet activation state.[11] Our previous study identified that moderate-intensity exercise training (60% maximal oxygen consumption for 30 min per day, 5 days/week for 8 weeks) reduced resting and strenuous exercise-induced platelet aggregation and platelet adhesion under shear flow in healthy men,[12] which were accompanied by decreased vWF binding to platelets and expression of P-selectin on platelets.[13] Accordingly, our main research question is that whether the short-term CR program in the current investigation ameliorates hemostatic imbalance at rest and platelet and coagulation activation at maximal stress exercise.