A man, 57, with a history of ischemic cardiomyopathy underwent orthotopic cardiac transplantation eight years ago. He presents for a routine posttransplant clinic visit, first presenting to the catheterization lab for a routine myocardial biopsy.

The patient has had no problems since his hospitalization six months ago for International Society of Heart and Lung Transplantation grade 3A rejection (treated with IV corticosteroids and cyclosporine optimization). He specifically denies fevers, chills, night sweats, headache, chest pain, palpitations, cough, shortness of breath, nausea, vomiting, or diarrhea.

His medical history is remarkable for dyslipidemia, left subclavian vein thrombosis, posttransplant renal insufficiency, and posttransplant hypertension. His medications include cyclosporine, azathioprine, prednisone, aspirin, beclomethasone spray, gemfibrozil, ferrous sulfate, lansoprazole, magnesium oxide, metoclopramide, rosuvastatin, trimethoprim/sulfamethoxazole, and fluconazole. He is allergic to penicillin.

Physical examination reveals a weight of 60.8 kg (a 1-kg increase since his last visit, one month ago); blood pressure, 146/100 mm Hg; pulse, 110 and regular; temperature, 37°C; respiratory rate, 14 breaths/min; and O₂ saturation, 98% on room air. The patient looks well compared to previous visits and is alert and in no distress.

The right internal jugular vein biopsy puncture site is covered with a dry dressing, and there is no evidence of bleeding or hematoma. He has no jugular venous distention or lymphadenopathy.

The cardiovascular exam reveals a regular rhythm with no murmur, rub, or gallop. The S₁ and S₂ are normal; there is no S₃ or S₄. The lungs are clear bilaterally without adventitious sounds. There is no peripheral edema.

Results of his right heart catheterization include a right atrial pressure of 1 mm Hg; pulmonary artery systolic/diastolic pressure, 22/12 mm Hg; mean pulmonary artery pressure, 15 mm Hg; pulmonary wedge pressure, 5 mm Hg; and cardiac output and index as determined by the Fick method, 3.4 L/min and 2.0 L/min/m².

An ECG is obtained and shows a ventricular rate of 117 beats/min; PR interval, 166 ms; QRS duration, 78 ms; QT/QTc interval, 338/471 ms; P axis, 70°; R axis, 81°; and T axis, 75°. What is your interpretation of this ECG?

The correct interpretation includes sinus tachycardia, a prolonged QT interval, and a nonspecific T-wave abnormality. Sinus tachycardia is defined as a heart rate of more than 100 beats/min arising from the sinus node. Cardiac transplant patients have a resting sinus tachycardia and a blunted chronotropic response to exercise due to a denervated sinus node as a result of transplantation. 

A prolonged QTc is defined as 440 ms or less. The QT interval is measured from the onset of the QRS complex to the point where the T wave returns to the baseline. Because the QT interval is markedly affected by heart rate, the QTc (corrected QT interval) may be calculated by Bazett’s formula (QTc = QT divided by the square root of the R-R interval) or derived from tables. QT intervals also vary with gender; females normally have a 10% longer QT interval. The QT interval is affected by autonomic tone. In the denervated transplanted heart, this is not unusual. Finally, a nonspecific T-wave abnormality is common in tachycardia and is not significant in this patient.