These effects can readily lead to angina. In addition, elderly patients may not present with a typical clinical picture of thyrotoxicosis. Therefore, this possibility should be considered in the setting of minimal risk factors accompanied by a history of typical angina, particularly in older patients. Sympathomimetic toxicity, of which cocaine is the prototype, not only increases myocardial oxygen demand but, through coronary vasospasm, simultaneously decreases supply, sometimes leading to infarction in young patients. Sustained tachycardia, either ventricular or supraventricular, may also increase myocardial oxygen demand.
Paroxysmal tachycardias are more frequent conditions that contribute to angina.
Unfortunately, they are often more difficult to diagnose. Conditions that reduce myocardial oxygen supply must also be considered in the differential diagnosis of patients with angina. Anemia reduces the oxygen-carrying capacity of the blood and also increases the cardiac workload. Obstructive sleep apnea should be seriously considered in patients with only nocturnal symptoms. Conditions that are associated with increased blood viscosity can increase coronary resistance and thereby decrease coronary artery blood flow, precipitating angina in patients without severe coronary stenoses.