The "giant R waves" ECG pattern of hyperacute phase of myocardial infarction. A case report.

The author describes a rarely appreciated electrocardiographic (ECG) pattern of the hyperacute phase of myocardial infarction, characterized by the transient development of very tall R waves merging with maximally elevated ST-segments, and the reduction of the depth, or complete disappearance of S waves. Similar ECG findings are frequently recorded in epicardial and precordial tracings in the animal laboratory, immediately following experimental occlusion of a coronary artery. In patients with acute myocardial infarction, the "giant R waves" ECG pattern is seen very early in the clinical course. Often the ECG appearances described above are missed either because patients suffering a myocardial infarction do not present to the hospital shortly after the inception of symptoms, or are attributed to conduction abnormalities of the classic variety or to ventricular tachycardia. The incidence of the giant R waves ECG pattern in the setting of clinical acute myocardial infarction is not known. Also its pathophysiologic, clinical, and prognostic correlates remain to be defined by appropriately designed research protocols.