A 40-year-old woman has Ebstein’s anomaly and right-sided heart failure. In the past year, she has had periodic episodes of a rapid heart rate; these have increased in frequency in the past two months. According to the patient, these episodes occur spontaneously without provocation, last for approximately 10 to 15 seconds, and are now an almost daily occurence. Severe lightheadedness and dyspnea accompany each episode. She has never had syncope. 

The patient’s most recent echocardiogram documented Ebstein’s anomaly with severe tricuspid valve regurgitation, severe right ventricular dilatation, moderate left ventricular dysfunction, moderate mitral valve regurgitation, and a left ventricular ejection fraction of 35%. Medical history is remarkable for hypothyroidism, ascites secondary to right-sided heart failure, and chronic renal insufficiency.

The patient is gainfully employed and married, and she does not smoke or drink. Current medications include torsemide, warfarin, digoxin, spironolactone, levothyroxine, and potassium chloride. She has no known drug allergies.

The review of systems is positive only for some increase in abdominal girth over the preceding month. She denies shortness of breath, chest pain, orthopnea, dyspnea on exertion, peripheral edema, diarrhea, abdominal pain, nausea, vomiting, joint pain or swelling, or pregnancy. Her last menstrual period began four days ago. She denies headaches, seizures, or mental status changes.

Physical examination reveals a weight of 189 lb; height, 68”; blood pressure, 120/80 mm Hg; pulse, 70 beats/min; respiratory rate, 16 breaths/min; and O₂ saturation, 95% on room air. Her temperature is 98.9°F. She is a very pleasant woman in no distress and is alert and ­oriented.

Pertinent physical findings include bounding jugular venous pulses with the jugular venous pressure at the angle of the jaw. The lungs are clear to auscultation bilaterally, and the cardiac exam is remarkable for an irregular pulse at a rate of 70 beats/min with a grade III/VI holosystolic murmur best heard at the apex. The abdomen is soft and nontender, with mild to moderate ascites present. The extremities are warm with no edema, cyanosis, or clubbing. The neurologic exam is grossly intact without focal signs.

An ECG is obtained and reveals the following: a ventricular rate of 70 beats/min; PR interval, 186 ms; QRS duration, 152 ms; QT/QTc interval, 512/553 ms; P axis, –1°; R axis, 106°; and T axis, –65°. What is your interpretation of this ECG?

ANSWER

The ECG is remarkable for normal sinus rhythm with occasional premature ventricular complexes, a single premature atrial complex, rightward axis, and nonspecific intraventricular conduction block.

Looking at the rhythm strip of lead II, the fifth and 11th beats exhibit an unusual and wide QRS with a bizarre axis and a large T wave with opposite polarity as the QRS complex, consistent with premature ventricular complexes. Though difficult to see in this tracing, P waves precede each QRS complex. The eighth beat on the rhythm strip in lead II is a premature atrial complex. The QRS complex is narrow and similar to intrinsic conduction; however, it occurs earlier in the cycle, with a pause following the QRS complex.

A rightward axis is illustrated by an R-wave axis between 90° and 180° and is present due to right ventricular hypertrophy in this case. Finally, nonspecific intraventricular conduction block is evidenced by a QRS duration of more than 100 ms in the absence of criteria for specific right or left bundle branch or fascicular block.