A 72-year-old man has ongoing dyspnea on exertion since his non-ST-segment elevation myocardial infarction (NSTEMI) 1 year ago. At the time of his NSTEMI, he had an 80% left anterior descending artery lesion that was stented and minor disease elsewhere. He finds he gets short of breath when he walks on any incline but is fine on the flat. The dyspnea is not getting any worse over time, but he is worried that his shortness of breath means that he has something wrong and is too worried to exercise. He has no orthopnea, paroxysmal nocturnal dyspnea, ankle swelling, or angina. His risk factors for heart disease include that he is an ex-smoker for some years with a 20-year pack history of smoking, hypertension, and dyslipidemia. These have been well-managed since his NSTEMI. He is on dual antiplatelet treatment (aspirin 81 mg daily and clopidogrel 75 mg daily), atorvastatin 80 mg daily, ramipril 2.5 mg daily, and metoprolol CD 47.5 mg daily.
On examination, you notice that he looks frailer, and he admits to being more sedentary since his heart attack. His body mass index is 29 kg/m2, his blood pressure is 128/70 mmHg, and his heart rate is 65 bpm sinus rhythm. His chest is clear, he has no murmurs, and there is no clinical indication of failure. His hemoglobin is 147 g/dL, B-type natriuretic peptide and thyroid function tests are normal, and he has stage II chronic kidney disease. An exercise stress echocardiogram shows structurally normal heart and a left ventricular ejection fraction of 55% with mild diastolic dysfunction and normal pulmonary artery pressure. He has an appropriate chronotropic response to exercise. He felt short of breath in early stage 2 of the normal Bruce protocol, but there were no arrhythmia or electrocardiographic changes of ischemia. Lung function tests show mild chronic obstructive pulmonary disease (COPD) (FEV1 88% predicted). Diffusing capacity of the lungs for carbon monoxide is normal, and there is no response to salbutamol. A chest X-ray was normal.
What intervention is likely to be the most beneficial to the patient?
The correct answer is: C. An exercise regime aiming to gradually increase his walking to 30 minutes per day 5 days a week at a moderate pace.
The most common causes of chronic dyspnea in this age group are pulmonary and cardiac causes. In this patient, the most common causes of dyspnea (atypical angina, arrhythmias, heart failure, asthma, COPD, anemia, thyroid disorder, and kidney disease) have been excluded.
Stopping the beta-blocker is not likely to have much effect because the patient has mild COPD with no reversibility with salbutamol.
Exercise test and chest X-ray are normal, and his dyspnea is not progressive. It is unlikely that his dyspnea is related to arrhythmias. A high-resolution computed tomography scan could be considered if the dyspnea were progressive, but he has normal diffusing capacity of the lungs for carbon monoxide, suggesting that interstitial lung disease is highly unlikely.
A cardiopulmonary test could be useful to assess the workload that the patient can achieve, the degree of dyspnea experienced, the peak oxygen uptake, cardiac output (calculated from carbon dioxide production and oxygen uptake), and relationship of minute ventilation to carbon dioxide production. However, this test is unlikely to lead to changes in management.
The patient is most likely to benefit from increasing his exercise level and improving his conditioning. This will have a long-term impact on improving his symptoms regardless of the cause by improving his exercise capacity as well as reducing anxiety. There is a downside to over-medicalizing his symptoms and heading toward further tests that are unlikely to yield important information. This may lead to further loss of confidence and increased anxiety. Regardless of whether his dyspnea is due to a combination of deconditioning and a pathological process, increasing his exercise level is beneficial.
In the STABILITY (Stabilization of Atherosclerotic Plaque by Initiation of Darapladib Therapy) trial, there was reduction in mortality from increasing habitual exercise intensity and/or exercise duration relative to current activity levels in patients with stable coronary artery disease. This was greater in participants who reported limitation of exercise by dyspnea and in those at higher risk of adverse cardiovascular events estimated from the STABILITY CHD risk score. The STABILITY study suggests that modest levels of exercise are likely to improve his prognosis.
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