A 39-year-old man is transferred from an outside hospital with coagulase-negative Staphylococcus (CoNS) endocarditis. He has a history of a dilated cardiomyopathy with a left ventricular ejection fraction of 25%, first diagnosed three years ago, and New York Heart Association class IIb heart failure. An implantable cardioverter defibrillator (ICD) system was placed one year ago for symptomatic, sustained ventricular tachycardia. There have been no device therapies. 

The patient has had multiple hospitalizations during the past year for decompensation of his heart failure, acute renal failure, and hyperkalemia. One week prior to his presentation to the transferring hospital, he developed rigors and dyspnea on exertion. Following admission, blood cultures revealed CoNS bacteremia, and a transthoracic echocardiogram documented a new right atrial mass. 

At your hospital, repeat blood cultures confirm CoNS bacteremia, despite initiation of IV antibiotics prior to transfer, and a transesophageal echocardiogram shows a large 2 x 3–cm mass arising from the ventricular defibrillator lead directly above, but not involving, the tricuspid valve.

The patient’s history also includes type 2 diabetes mellitus, hypothyroidism, microcytic anemia, renal insufficiency, cholecystitis, morbid obesity with sleep apnea, and gout. The surgical history is remarkable for ICD implantation and a cholecystectomy. Family history is significant for familial dilated cardiomyopathy and diabetes. The patient is married, denies tobacco use, and drinks alcohol sparingly. 

Medications include digoxin, enalapril, metoprolol, torsemide, potassium chloride, warfarin, insulin glargine, levothyroxine, ferrous sulfate, and allopurinol. Prior to transfer, he was started on IV vancomycin. He is allergic to penicillin and sulfa.

On examination, the patient’s blood pressure is 110/68 mm Hg; pulse, 90 beats/min; temperature, 37.4°C; respiratory rate, 14 breaths/min; and O2 saturation, 96% on room air. He is alert, in no apparent distress, and oriented. Respirations are decreased in both bases.

The cardiovascular exam shows no evidence of jugular venous distention; the S1 and S2 are diminished, and there are no murmurs, rubs, or extra heart sounds. The left pectorally placed ICD system incision is well healed without erythema, ecchymosis, induration, or hematoma. The abdominal and neurologic exams are unremarkable, and there is no peripheral edema.

An ECG reveals the following: a ventricular rate of 92 beats/min; PR interval, 244 ms; QRS duration, 152 ms; QT/QTc interval, 388/479 ms; P axis, 16°; R axis, –10°; and T axis, 135°. What is your interpretation of this ECG?

ANSWER

The correct interpretation of this ECG includes sinus rhythm with a first-degree atrioventricular (AV) block and a left bundle branch block (LBBB). Normal sinus node depolarization with a resultant PR interval greater than 200 ms is called first-degree AV block. An LBBB is diagnosed by the presence of a QRS duration of 120 ms or higher, with terminal S waves in lead V₁ and terminal, monophasic R waves in leads I, aVL, and V₆.

These ECG findings are a result of the patient’s dilated cardiomyopathy and not the presence of the intra-atrial mass.