Evaluation of lactate dehydrogenase isoenzyme patterns in serum of patients undergoing cardiac surgery.

Serial determinations of serum lactate dehydrogenase (LD) isoenzymes were performed in 50 patients undergoing cardiac surgery for coronary artery bypass and heart valve replacement. A sequence of LD isoenzyme patterns was established in the patients with uncomplicated recovery. These patterns served as controls for the detection of abnormal patterns associated with clinical complications. Perioperative myocardial infarction was detected in seven patients by a characteristic reversal of the LD1:LD2 ratio. These studies established that accurate determination of LD isoenzymes improved their diagnostic specificity. These isoenzymes were determined by (1) using the same technique for tissues and for serum samples, (2) applying a volume of serum containing a standard amount of enzymatic activity, and (3) making a clear separation, which allows accurate quantitation. This test can provide useful information to the surgeon for the evaluation of operative procedures and to the clinician for the appropriate management of the patient undergoing cardiac surgery.