ACUTE CARDIAC TAMPONADE

ACUTE CARDIAC TAMPONADE: Etiology: This is an uncommon medical emergency which results from rapid collection of fluid in the pericardial cavity. Occasionally, the process is slower and in such circumstances massive quantities of fluid may accumulate in the pericardial sac before features of cardiac tamponade appear. The fluid can be serous, purulent.or haemorrhagic and may be due to a variety of causes, the commonest being tubercular, at any rate, in this part of the world. The circulatory embarrassment results from defective diastolic filling of the heart with corresponding drop in stroke output and blood pressure.

Clinical Features. The onset may be acute (as in haemopericardium and purulent pericarditis) or gradual (e.g.,tubercular effusion). In the former event, even small effusions of 200-250 ml may produce acute distension of the pericardium and interfere with flow of blood into the ventricles. On the other hand, with slowly developing effusions, large quantities (over a litre) may accumulate without serious consequences and then suddenly patient may develop collapse and cardiogenic shock.
Clinically, acute cardiac tamponade is suggested by a triad of signs comprising increasing venous pressure, a falling arterial pressure and a quiet heart. The patient is markedly dyspnoeic, anxious, restless, appears pale and has marked tachycardia. There is often evidence of paradoxical pulse and the blood pressure is greatly reduced, pulse pressure being often 20 mm Hg or less. In severe cases shock may supervene.
When collection of fluid has been somewhat gradual, there may be additional evidence of systemic venous congestion indicated by engorged jugular veins, enlarged liver and puffiness of face with cyanotic lips. In such cases examination of the heart will also reveal an increase in the area of cardiac dullness and muffled heart sounds. The electrocardiogram is of further help and shows elevation of RS-T segment in all or any of the standard leads and precordial leads, Without reciprocal depression in other leads, as occurs in cases of acute myocardial infarction. In chronic cases of pericardial effusion, T waves may also be inverted in all the’ standard leads.

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