Introduction
Angina is chest discomfort that occurs when the oxygen supply to the myocardium is
insufficient to meet its metabolic demands. Classically, the patient will present with a
history of substernal chest discomfort (often not described as a "pain" but as a
tightness, squeezing, or pressure-like sensation) occurring with exertion and relieved
within minutes with rest. This discomfort may radiate to the neck, jaw, or either arm and
may be associated with shortness of breath. The diagnosis of angina depends largely on
history. Physical exam and laboratory studies are often normal in the chronic stable
angina patient. The electrocardiogram (ECG) will be normal in over a third of patients who
are pain free on presentation, but may show evidence of prior infarction, an
intraventricular conduction delay, or nonspecific ST-T wave abnormalities.
Differential Diagnosis
The differential diagnosis of angina includes a broad range of both cardiac and
noncardiac causes of chest discomfort. These include gastroesphageal reflux, diffuse
esophageal spasm, pericarditis, aortic dissection, musculoskeletal pain, and pulmonary
embolus. By considering the quality, duration, location, and precipitating factors of the
chest discomfort, it is usually possible to distinguish angina from these other causes of
chest pain.
Causes of Angina
After establishing a diagnosis of angina, you should consider possible etiologies.
The leading cause is certainly atherosclerotic coronary artery disease. As critical
stenosis develops within the coronary arteries, myocardial oxygen supply/demand
relationships with exertion are not met and angina occurs. Uncommon causes of angina in
our active duty population include hypertrophic obstructive cardiomyopathy, severe aortic
stenosis, pulmonic stenosis, pulmonary hypertension, and Prinzmetal's vasospastic angina.
Descriptions of these entities may be found in standard medicine and cardiology texts.
Also consider other factors that could produce angina like symptoms including anemia,
thyrotoxicosis, underlying infection with tachycardia, and hypoxemia.
Management considerations
Unstable angina requires aggressive management. Unstable angina is variously
defined as new onset angina at a low level of activity with significant worsening of a
patient's existing anginal pattern, and angina at rest for patients with a suspected
unstable angina syndrome. Urgent consultation with a subspecialist is needed. Through
appropriate consultation, the required level of care for the unstable angina patient will
be decided. Many of these patients will require admission to a coronary care unit for
intravenous heparin, nitroglycerin, beta-blockers, aspirin, and telemetry monitoring. For
discomfort persisting longer than 20-30 minutes, myocardial infarction should be excluded
with serial enzymes and ECG's. The use of Spectralä slides for Myoglobin, CKMB, and Troponin may be available on some platforms.
Initial management of unstable
angina
If faced with an unstable angina patient in the field or on a ship, start treatment
by administering oxygen (if available), have the patient chew one aspirin 325mg,
administer sublingual nitroglycerin or nitropaste, and start an intravenous line. Ensure
the systolic blood pressure remains above 90 mmHg. A beta-blocker
should be initiated if
not contraindicated. If there is ongoing pain and ST depression, an IV beta-blocker is
preferred. Consider starting intravenous nitroglycerin or a heparin drip, if available.
Arrange for urgent MEDEVAC.
Low molecular weight (LMW) heparin, enoxaprin, has been proven to be equally effective
as titrated unfractionated heparin with simpler dosing at 1 mg/kg subcutaneous every 12
hours.
Management of chronic stable
angina
If presented with a patient diagnosed as chronic stable angina, treatment may be
initiated with one aspirin/day and some combination of antianginal medications--nitrates, beta-blockers, or calcium channel
blockers, tailored to your given patient. For the chronic
stable angina patient, an aspirin/day, a low dose B-blocker (tenormin 50 mg PO BID or
metropolol 50 mg PO QID), and SL nitroglycerin on an as needed basis is a reasonable
starting point. Attention should be given to concomitant cardiac risk factors, for example
hypertension, diabetes, tobacco abuse, and hypercholesterolemia. For the newly diagnosed
chronic, stable patient, timely referral for exercise stress testing is appropriate to
further risk-stratify the patient and aid in determination of suitability for full duty.
Initial presentation is usually unhelpful in distinguishing patients with angina due to
single vessel coronary artery disease from those with left main or three-vessel disease.
Some patients will need cardiac catheterization, and possible interventional treatment or
coronary artery bypass surgery.
Summary
Chronic stable angina can be managed comfortably by the general medical
officer with timely subspecialty consultation. Patients with unstable angina syndromes
require urgent referral to a higher echelon of medical care. In cases with diagnostic
uncertainties, obtain an ECG, chest X-ray, and labs, and then phone consultation to the
next higher level of care.
References
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Braunwald, Eugene, Heart Disease. 4th Edition 1992 W.B. Saunders.
Silverman, K and Grossman, W. Angina Pectoris. NEJM 1984; 310:1712-17.