ANGINA OF EFFORT

ANGINA OF EFFORT
Treatment of Attacks.—It is unusual for a patient to be seen by his doctor
while actually in the throes of effort angina. The attacks are of short duration and occur while the patient is about his daily business, and even if a doctor is summoned the pain is likely to have abated spontaneously before he reaches the patient. When pain has lasted without intermission for half an hour or more it should be regarded as a case of myocardial infarction and treated as such. The same applies to patients previously free from angina or suffering from attacks of only moderate severity who suddenly develop attacks of great frequency on slight exertion. Such cases are commonly labelled acute coronary insufficiency. Some at least suffer occlusion of coronary arterial twigs, leading to patchy infarction and later to small scars in the myocardium.
The patient who is habitually seized with praecordial pain while walking soon realizes that continued effort aggravates his discomfort, and learns that he must stand still when pain comes on. In many cases this suffices to relieve the pain promptly, and no medication is required. In more severe or resistant cases one or other of the quickly acting nitrites usually affords relief, and the subjects of effort angina frequently carry such preparations for emergency use. The traditional remedy is amyi nitrite in small capsules or " perles " containing 0-2 to 0-3 ml. (3 to 5 min.). A capsule in its fabric cover can be broken in the fingers, and the vapour inhaled. Speedy relief from pain is common, but not all cases respond. Further, the side-effects and conspicuous odour render it unpopular. For these reasons the drug has been largely replaced by nitroglycerin, which is more reliable and, being taken orally, is less liable to cause embarrassment. The familiar chocolate-coated tablets of nitroglycerin have been replaced in the B.P.
by white tablets incorporating mannitol as a stabilizer. The dose required to abort an attack varies in different cases, but it is convenient to prescribe the B.P. tablets of glyceryl trinitrate containing 0-5 mg., and to adjust the" number of tablets taken to secure the appropriate dose. While relief may follow the taking of as little as 0-25 mg. 0-5 mg. usually required and sometimes 1 mg. or even exceptionally 2 mg. may be necessary. It is important to instruct the patient to chew and suck the tablets, as absorption has been proved to be most rapid from the buccal mucous membrane.
Both amyi nitrite and nitroglycerin have a brief action, lasting a few minutes only, so that it is understandable that longer acting analogues have been sought. Of these, considerable numbers have been introduced in recent years and each has for a time enjoyed some popularity, backed as each has been successively by the persuasive advertising of the drug firms. It is appropriate here to remind the reader that however potent a vasodilator may be for the coronary vessels of healthy animals, its action on the rigid, sclerosed or calcified coronary arteries of anginal subjects is to say the least problematical. The relief from pain afforded by many vasodilators (not excluding nitroglycerin) may be due rather to peri¬pheral action and decreased cardiac load than to direct action on the coronary vessels. Examples of long-acting coronary vasodilators include pentaery-thritol tetranitrate, prescribed in doses of 20 to 60 mg. twice or thrice daily, of which the vasodilator action is certainly longer than that of nitroglycerin, yet carefully controlled clinical trials of its action in angina have shown it to be less effective. Khellin (oral dose 25 mg.) and other preparations of the Egyptian plant Amni visnaga have proved similarly somewhat ineffective, and these drugs produce nausea in such a high proportion of cases that their use is commonly contraindicated. One of the most promising of the long-acting preparations is nitroglycerin dispensed in tablets specially prepared to release the drug in small • quantities over a prolonged period. These tablets contain much larger doses than the ordinary therapeutic single dose of 0-5 mg. The gradual solution of the matrix in the gut over a number of hours produces a prolonged effect. These slow-release tablets are naturally not recommended for quick relief of an acute attack of angina, but are designed to afford protection from attacks over several hours. Various mono-amine oxidase inhibitors (iproniazid, isocarboxazid, nialamide) have been claimed to be effective long-acting coronary vasodilators, but such action as they possess is outweighed by their potential toxicity.
After subsidence of an episode of pain many patients are able to resume walking or other activity where they left off, but should be warned to adopt a slower pace than that which provoked the pain.