A Tour around Angina Pectoris
(Date of publication 06 February 2004)

The pain of angina has been described as "like having a refrigerator sitting on your chest and hot pokers burning the backs of both arms". The chances are that this description will be familiar to a sizeable number of readers, because the incidence of the condition is high; for example, in the USA it affects more than 6,000,000 individuals. The cause is myocardial ischaemia, or reduced blood flow to the heart muscle, usually as a result of atherosclerosis. The Cardiology Channel site describes the two main types. In stable angina, pain is brought on by increased physical activity that increases the heart's requirement for oxygenated blood, but subsides if the patient rests. Unstable angina is more serious and constitutes a medical emergency; the pain is more frequent, lasts longer, can occur at any time and may lead to a heart attack (myocardial infarction).

In the Emergency Department, the diagnosis of myocardial ischaemia as a cause of chest pain is based on the patient's history, risk factors and, to a lesser extent, ECG. Among the ECG changes that may be seen during anginal episodes are transient ST segment elevations, dynamic T-wave changes and ST depressions. The goals of treatment are to preserve the patency of the coronary arteries, augment blood flow and reduce myocardial oxygen demand. Patients are given anti-platelet agents, and those with evidence of continuing ischaemia receive aggressive medical intervention until signs and symptoms recede.

From previous stops on this tour you will be aware of another, less common cause of ischaemic chest pain, Prinzmetal's Angina, which results from intense spasm of a coronary artery. The New England Journal of Medicine includes a case history of a 39 year old sufferer in whom it produced frequent episodes of pain, shortness of breath and sweating (diaphoresis) while at rest. This page includes Real Media videos of his ECG recording, showing dynamic ST-segment elevation. A word of warning though; unless you have a high speed internet connection it may not work.

The Merck Manual has a comprehensive overview of the signs and symptoms, diagnosis and treatment of angina, as well as the different types. It makes the point that in stable patients, even those with three-vessel disease, the prognosis is surprisingly good if ventricular function is normal. The section on exercise testing, used to determine the functional and ECG response to graded stress, is particularly detailed. In patients with angina, the ECG typically demonstrates a flat or downward-sloping ST segment depression. The ischaemic trace near the bottom of this page illustrates horizontal depression in the V6 lead.

The exercise ECG is the second step (after the clinical presentation) in the rational diagnostic procedure described by Dr Eugenio Picano for screening patients with known or suspected coronary artery disease. He quotes a trial which found that a negative exercise ECG (i.e. no pain or ECG abnormalities) is associated with a 99.3% survival after 5 years in patients with normal resting function, and that survival is only slightly lower in patients with a history of myocardial infarction. He recommends that patients with a positive exercise ECG should undergo stress echocardiography to determine the severity and extent of the suspected ischaemia; a negative result here indicates that organic coronary artery disease is unlikely to be present. In higher risk patients who have a positive result, coronary angiography is warranted.

Coronary angiography is a diagnostic x-ray procedure designed to visualise the smaller arteries of the heart, those between 1 and 3 mm in diameter. A fine wire is inserted via a needle in the femoral artery and threaded back through the arterial tree into the aorta, its position being confirmed by x-ray fluoroscopy. An angiogram catheter is passed over the wire and positioned at the mouth of the coronary arteries, just above the aortic valve. A dye is then injected and its passage through the arteries monitored using x-rays, so that any narrowing (stenosis) or obstruction can be seen. A blockage of more than 50% of a vessel's diameter is considered significant. This presentation about this procedure, complete with sound, at is simple and straightforward; there is appreciably more detail and some x-ray pictures of severe arterial occlusion here. Additional radiographs can be seen here.

A newer, non-invasive method of quantifying the extent of atherosclerosis is by using electron beam computerised tomography (EBCT) to visualise intra-coronary calcium deposits. The St Francis Heart Study concluded that coronary calcium scores predicted coronary disease with considerably more accuracy than standard risk factors, and other recent studies have suggested a relationship between coronary calcification scores and coronary events.

The British National Formulary has an account of the pharmaceutical treatment of angina patients. In stable angina, sublingual glyceryl trinitrate is used to manage acute attacks, and regular drug therapy may include aspirin, beta-blockers, calcium channel-blockers and nitrates. The management of unstable angina is also outlined, but this has already been covered on the emedicine site.

If an arterial blockage is not severe, it may be treated by percutaneous transluminal coronary angioplasty (PTCA) to increase the size of the lumen. The procedure is very similar to that of coronary angiography, and indeed may be carried out immediately afterwards. Essentially, the surgeon passes a tiny deflated balloon through a catheter from the groin to the blockage in the coronary vessel. It is then inflated to compress the atheromatous plaque against the wall of the artery, so that blood can flow more freely. Today, surgeons usually then place a stent - an expandable metal mesh tube - at the site to keep the artery open. The procedure is explained on the University of Maryland Medicine site, but if you prefer the hi-tech alternative there is an impressive Shockwave animation, complete with commentary.

When the artery is almost completely occluded the patient is likely to be offered bypass surgery, in which grafts are implanted to carry blood from the aorta to the affected coronary arteries beyond the blockage. Sometimes the internal mammary artery is harvested and anastomosed to the coronary vessel, and sometimes the saphenous vein from the leg is used to create a new vessel. These photographs make it easy to understand the procedure, but are not for the squeamish! Traditionally, the patient was put on a heart-lung machine and the heart stopped, but surgeons may now perform the operation on a beating heart; this is technically more difficult but less damaging to the myocardium and reduces the stress on the patient. It is even possible to complete the procedure using robotic arms and minimally invasive surgery. Perhaps it is just as well that the patient is unconscious at the time!

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