Electrocardiographic patterns in slight coronary attacks.

The seriousness of cardiac infarction can be assessed on clinical grounds. Prolonged pain refractory to morphia, severe shock with fall of blood pressure to dangerous levels, and the early onset of cardiac failure are unequivocal signs of a severe attack. In many patients regarded as suffering from cardiac infarction there are none of these signs, and the diagnosis is based on coronary pain accompanied by electrocardiographic changes of acute myocardial ischaemia. Were it not for the persistent electrocardiographic signs such attacks would be more suggestive of prolonged bouts of angina at rest than cardiac infarction proper. The clinical term " slight coronary attack " applied to this condition seems thus appropriate, for the symptoms are slight and the name disregards the problematic existence of actual thrombosis and myocardial necrosis. Slight coronary attack implies cardiac pain for half an hour or more, arising at rest and not relieved by trinitrin, always accompanied by persistent electrocardiographic signs of myocardial ischaemia but not by the clinical and laboratory signs of extensive myocardial necrosis (Papp, 1949) Similar conditions have been variously described. "Coronary insufficiency without occlusion" is the term used by Master (1946) for a condition more severe than angina of effort but lighter than acute myocardial infarction-for the latter he proposes the name " acute coronary insufficiency with acute occlusion ". He lists a great number of exciting causes restricting coronary blood flow and responsible for the attack. But these have only exceptionally played any part in our series, in which the attacks were as sudden and devoid of cause as in the classical acute coronary occlusion. "Coronary failure " is the name given by Freedberg, Blumgart, Zoll and Schlesinger (1948) for the " clinical syndrome intermediate between angina pectoris and acute myocardial infarction ". This syndrome is of wide range and comprises some of our cases. However, in coronary failure the electrocardiographic changes are slight or absent, except in the more severe cases where they may persist for hours and then revert to normal. This was not so in the majority of our series where a diagnosis of cardiac infarction was made on the basis of persistent electrocardiographic changes showing the initial signs of acute myocardial ischiemia with subsequent serial changes typical of such lesions for weeks or months after the acute attack. The purpose of the present investigation is, first, to determine the incidence of slight coronary attacks and how far there is an agreement between the slight clinical and electrocardiographic features; secondly, to investigate the prognosis of the attack and the incidence of the early complications, and thirdly, to draw conclusions regarding treatment.