CR leads in cardiac emergencies. A preliminary study. The purpose of this study was to find a set of simplified electrocardiographic (ECG) leads that would be useful in cardiac emergencies. In 27 ambulatory cardiac patients and in 15 patients admitted to the hospital, we found that ECG records obtained with six bipolar CR leads were, in most respects, similar to records obtained previously in the same patients with six V leads. Records obtained with two abdominal-upper extremity leads, tested as possible alternatives to limb leads 2 and 3, were quite similar to records obtained with leads 2 and 3 in patients with an inferior wall infarction. Records obtained with leads CR7, CR8, and CR9 in a patient with a posterior wall infarction revealed a QS pattern that was not seen in the conventional 12-lead hospital record. In patients with anterolateral and inferior myocardial infarctions and in patients with unstable angina, the diagnostic patterns recorded with 11 bipolar leads described in this report were identical to patterns recorded with 12-lead ECGs. Although a larger number of observations, including patients with arrhythmias, would be required to reach a definitive conclusion, our results provide preliminary evidence that cardiac potentials may be adequately analyzed by using only two electrodes, using CR and abdominal leads, in succession. The technique described in this report, in which the reference electrode is attached to the right arm, and the exploring electrode is moved successively over nine preselected chest sites and over the umbilicus, can be completed in less than 3 minutes in a given patient, and provides records that are comparable to those obtained with the conventional 12-lead system. 