Coronary artery disease results from an inadequate supply of blood to the myocardium, most commonly arising from an obstruction of the coronary arteries due to atherosclerosis.
The clinical manifestations of coronary artery disease show a wide range of variation, with some individuals being completely asymptomatic, whilst others may develop stable or unstable angina pectoris. A large number of people may present with myocardial infarction (MI), whereas congestive heart failure and cardiomyopathies are not unusual outcomes. Patients may even present with sudden cardiac death.
The predominant symptom seen in coronary artery disease patients is chest pain (stable angina) that is retrosternal in location and commonly radiates to the left arm and neck  . Often associated with shortness of breath, this pain is aggravated by activity and rapidly relieved by rest/nitrates  .
Unstable angina is characterized by severe and more frequent episodes of chest pain. Chest pain may also be evident on rest.
MI patients often report a protracted course of anginal pain associated with increased sweating. Intermittent claudication, mesenteric angina, transient ischemic attacks and strokes are some of the other common ways in which coronary artery disease presents.
On examination, tachycardia, tachypnea and an irregular pulse may be present. Hypertension or hypotension may be found in these patients. Signs suggestive of congestive cardiac failure may be seen such as limb edema, pulmonary congestion, diaphoresis, abdominal swelling, etc . Murmurs and extra sounds (the third and fourth heart sounds) may also be present. Other signs include central obesity, xanthelasmas, livedo reticularis or diagonal ear creases.
Coronary artery disease requires emergency management and must be strongly suspected in patients presenting with any of the symptoms mentioned.
An electrocardiogram (ECG) is the most important investigation to be performed for such individuals within 10 minutes of presentation. ST segment elevations ≥ 1 mm present in 2 or more contiguous leads is strongly suggestive of an ST-segment elevation MI (STEMI)  . Pathologic Q waves may develop over time. With a specificity of 90%, serial ECG measurements may help confirm the diagnosis or may even guide the treatment strategy. A pulse oximetry and chest radiography may aid in diagnosis.
Detection of serum cardiac markers suggestive of myocardial necrosis are highly suggestive of MI. Troponins I and T are the markers of choice and show a high sensitivity and specificity (can detect levels as low as 1 pg/ml) at detecting STEMI . Other serum cardiac markers that may be helpful include myoglobin and creatine kinase-MB.
A diagnostic coronary angiography combined with percutaneous coronary intervention (PCI) procedures has proven to be life-saving for people with MI. Patients with STEMI may benefit from PCI (angioplasty, placement of stents) when they present within 3 hours of onset of angina. Long term outcomes for unstable angina and NSTEMI patients are also improved by delayed (within 24-48 hours) coronary angiography.
Routine investigations aren’t of much help in coronary artery disease; however, a fasting lipid profile must be done in all such patients. Cardiac stress testing, echocardiography and/or cardiac nuclear imaging studies may also be beneficial in these individuals.