ABC | Volume 114, Nº5, May 2020

Arq Bras Cardiol. 2020; 114(5):943-987 Guidelines Brazilian Cardiovascular Rehabilitation Guideline – 2020 CPET, by allowing analysis of the oxygen pulse response, provides increased sensitivity and specificity for the diagnosis of myocardial ischemia. 169 When there is an occurrence of an early plateau of oxygen pulse or, particularly, a drop during exertion, the exercise prescription should be limited to loads below that alterations. Thus, CPET is considered the gold‑standard assessment method to support exercise prescription and should be used whenever it is available. 169-171 In patients who complete a CPET, the prescribed exercise intensity should lie between the ventilatory thresholds and increase progressively from there. Regarding the volume of exercise, at least 150 minutes/week are recommended, distributed across 3 to 5 sessions. Depending on tolerance, adaptations to training, and individual preferences, as well as consideration of clinical status, this volume may be increased to 300 minutes or more per week. For resistance training, the gold-standard method to determine the optimal intensity is 1RM testing. However, in practice, many rehabilitation programs do not perform this test due to time constraints or clinical limitations, such as in patients who have undergone CABG andmay thus be limited not only by sternotomy but also by saphenectomy. In such cases, subjective perceived exertion is a practical and useful alternative. In patients who have undergone sternotomy, upper body exercise should be limited to low intensity and performed with restricted loads for 5 to 8 weeks. Exercises involving the full range of motion of the arms may be allowed after this period if there is no sternal instability, although recent and ongoing studies are evaluating the safety of earlier exercise after CABG. 172,173 Patients should always be instructed on how to correctly perform movement and breathing, avoiding the Valsalva maneuver. The interval between series can range between 45 s and 1 min, depending on the load applied and the patient’s tolerance. 6.3.4. Special Considerations for the Prescription and Follow-Up of Physical Exercise Programs 6.3.4.1. Refractory Angina Refractory angina is defined as disabling angina of over 3 months’ duration, despite optimized clinical treatment, with documentation of myocardial ischemia in a patient who is not considered eligible for percutaneous and/or surgical coronary intervention. 174,175 Such patients are generally not referred to CVR programs due to fear of adverse events during physical training, although rehabilitation has already been considered a feasible and safe possibility for these patients. 175 The objective of therapeutic interventions in this setting is to improve quality of life and facilitate performance of the activities of daily living. 176-178 A single controlled study has evaluated CVR in patients with refractory angina. The study randomized 42 subjects to a CVR exercise program or usual care for 8 weeks. Patients in the CVR group were prescribed training to a target HR between 60 and 75% of HR reserve (for those with preserved ventricular function) or between 40 and 60% of HR reserve (when LVEF was <40%). Patients in the rehabilitation group increased their total distance on the shuttle walk test by 50 m, with no change in severity or frequency of angina. There were no adverse events in either group. 161 An ongoing Brazilian randomized trial 162 will evaluate the safety and efficacy of a 12-week supervised exercise program in patients with refractory angina, carried out in a hospital environment with continuous ECG monitoring. Exercise prescription is individualized, on the basis of CPET findings and the ischemia and/or angina threshold. To date, 42 patients have been included, and no exercise-emergent cardiovascular events or hospitalizations related have been documented. Serum levels of high-sensitivity troponin T, a known predictor of worse prognosis, 179 did not change in 32 patients who completed a 40-minute acute aerobic exercise session (at the ischemia threshold) at the time of study enrollment ( unpublished data ). In patients with refractory angina and a low ischemic threshold, administration of rapid-acting nitrates before the start of each physical training session can help prolong the duration of training and even allow exercise at higher intensities. 180 6.3.4.2. Exercise Training with Myocardial Ischemia Traditionally, there is a recommendation that physical exercises in patients with CAD be performed below the clinical and electrocardiographic ischemic threshold; however, this can be difficult to control. Previous studies have shown that physical exercise, even when prescribed according to literature recommendations, can trigger scintigraphic perfusion defects which are not demonstrable on ECG and do not trigger angina, 181,182 because changes in contractility and perfusion defects precede clinical and electrocardiographic ischemic changes. 183,184 The functional significance of ischemic defects visible only on myocardial perfusion imaging is still unclear, but some studies of training above the ischemic threshold have been carried out. In one study of a single 20-minute training session conducted above the ischemic threshold, no evidence of acute myocardial damage was identified. 185 Other authors demonstrated in a small series of patients with CAD that, after 6 weeks of training, repetitive ischemic stimuli did not result in significant damage, myocardial dysfunction, or arrhythmias. 186,187 Therefore, there is evidence to suggest that interval training, a modality that has proven to be safe and effective in improving physical fitness, endothelial function, and left ventricular function with results superior to those obtained with moderate-intensity continuous training (MICT), may be feasible in patients with stable CAD. 187,188 Additionally, there is evidence of the superiority of combined aerobic and resistance training as opposed to aerobic training alone in patients with CAD. 189 6.3.4.3. Drug Adjustments in Response to Physical Exercise Patients with stable CAD usually rely on medications for symptom relief, reduction of ischemia, improvement of endothelial function, stabilization of atherosclerotic plaque, control of risk factors, and maintenance of adequate hemodynamics. For example, high SBP and/or HR levels (increased double product) lead to clinical deterioration. On the other hand, systolic hypotension and bradycardia produce reduced cardiac output, which can cause abnormalities due to a drop in coronary flow. 959