The patient is a 42-year-old woman with a history of a ventricular septal defect that was surgically corrected when she was 3. Five years ago, she underwent a Ross procedure (in which the native aortic valve is replaced with the patient’s own pulmonic valve and a valved homograft is inserted in the pulmonic position). Postoperatively, she was found to have high-grade atrioventricular block but was -asymptomatic.

Today, she presents to the echocardiography laboratory for a routinely scheduled electrogram as follow-up to her Ross procedure. She now reports a four-month history of progressive dyspnea on exertion; she is only able to walk slowly for about five minutes on flat ground, while previously she could walk approximately five miles without difficulty. She also notes increasing lower extremity edema and lightheadedness with exertion. She denies palpitations, and she has had no episodes of near-syncope or syncope. Her history is also significant for pulmonary hypertension and systemic hypertension.

Her current medications include lisinopril (10 mg bid), aspirin (81 mg/d), furosemide (40 mg/d), and a multivitamin.

On physical examination, her temperature is 35.9°C; blood pressure, 140/68 mm Hg; heart rate, 50 beats/min; respiratory rate, 20 breaths/min; and oxygen saturation, 94% on room air. She is in no acute distress. There is no visible jugular venous distention when the patient sits up in bed. The chest is clear to bilateral auscultation. The cardiac exam reveals frequent extra systoles. The first and second heart sounds are distant but sound normal. There are no murmurs, rubs, or gallops. The abdominal exam is benign, and there is no peripheral edema.

The transthoracic echocardiogram reveals a dilated left ventricle with a left ventricular ejection fraction of 25% and questionable perivalvular aortic insufficiency. A follow-up transesophageal echocardiogram is performed and preliminarily demonstrates a normal prosthetic aortic valve.

An ECG shows the following: a ventricular rate of 53 beats/min; PR interval, not measurable; QRS duration, 172 ms; QT/QTc interval, 550/516 ms; P axis, 46°; R axis, –6°; and T axis, 184°. What is your interpretation of this ECG?

ANSWER

The ECG shows sinus rhythm with complete heart block, premature ventricular complexes, and a left bundle branch block (LBBB). (Although the progressive PR intervals may resemble Wenckebach block, the sinus node depolarizes in a regular manner, at a rate of 60 beats/min. Therefore, the patient does not have a Wenckebach block.) LBBB is characterized by QRS complexes of 0.12 or more sec, a QRS that is predominantly negative in lead V₁, and ST depressions and T-wave inversions indicative of repolarization changes. Finally, the eighth QRS complex on this ECG is a premature ventricular complex.

With high-degree and intermittent complete atrioventricular block, a low ejection fraction, and New York Heart Association class III symptoms with a wide QRS, this patient meets criteria for cardiac resynchronization therapy (see January 2008 ECG Challenge).