Electrocardiographic pseudo-infarction pattern: appearance with a large posterior pericardial effusion after cardiac surgery.

Two patients with a large posterior pericardial effusion after cardiac surgery presented with electrocardiographic precordial Q waves without evidence of myocardial infarction. Resolution of the pericardial fluid resulted in the disappearance of the Q waves. Changes in conductivity and orientation of the heart within the pericardial space, along with a decrease in QRS voltage, could lead to the loss of initial R waves in the precordial leads, eventually resulting in a QS complex. Care should be taken in interpreting the electrocardiogram after cardiac surgery in patients with a large posterior pericardial effusion. The clinical course along with serial electrocardiographic and echocardiographic tracings should be helpful in identifying this false infarction pattern.