A50-year-old man had an electrocardiogram interpreted by the machine as "abnormal" (Figure 1). The rate and rhythm were normal, but the limb leads resembled those of right axis deviation—the P waves and QRS complexes were positive in aVF and negative in lead I. In addition, precordial leads V4, V5, and V6 showed strikingly low voltage. Initially, the clinical diagnosis was limb lead reversal, but after reviewing the patient's chest film, the correct diagnosis became obvious—dextrocardia with situs inversus—the heart is in the right hemithorax, with a right-sided aortic arch and gastric air bubble (Figure 2).

Points to remember: Test results are interpreted best when viewed in light of the associated clinical and laboratory findings. In this case, for example, the chest film was the key to the correct electrocardiographic diagnosis.