An 18-year-old woman has abused cocaine and alcohol for four years. She has been followed for two years for a dilated cardiomyopathy, presumably precipitated by substance abuse, but she frequently fails to keep her appointments. She has no structural abnormalities of the heart.

She arrives at the emergency department following two days of progressive shortness of breath, fatigue, and lethargy. This morning, she awoke with a fever and shaking chills. She admits to binge drinking for the past week and trying heroin once.

Her medical history is remarkable for anxiety and depression. The patient has been raised by several foster families since age 2, making a family history unobtainable. She dropped out of school in 11th grade and has been living with friends since. She occasionally smokes marijuana. 

The patient refuses to take prescribed medications other than oral contraceptives. A toxicology screen is positive for cocaine, heroin, cannabis, and ecstasy. She has no known drug allergies.

Physical examination reveals a woman in moderate distress who appears quite ill. Vital statistics include a height of 5’6”; weight, 112 lb; blood pressure, 96/50 mm Hg; temperature, 38.8°C; respiratory rate, 26 breaths/min; and O2 saturation, 95% on room air. Pertinent cardiac findings include jugular venous distention to the angle of the jaw, tachycardia with a regular rhythm, and a summation gallop but no murmur. The abdominal exam is remarkable for a pulsatile liver edge and a palpable, tender spleen. She has no abnormal neurologic findings.

A summary of her admission laboratory data reveals normal serum electrolyte levels, elevated liver function studies, serum glucose measurement of 158 mg/dL, blood urea nitrogen concentration of 77 mg/dL, creatinine level of 2.1 mg/dL, and white blood cell count of 15,800/mL. A chest x-ray shows cardiomegaly and a small left pleural effusion. An echocardiogram shows severe biventricular enlargement with a left ventricular ejection fraction of 20%, mild pulmonary hypertension with pulmonary artery systolic pressures of 40 to 50 mm Hg, an elevated right atrial pressure of 20 mm Hg, and a left ventricular thrombus measuring 1.5 x 3.0 cm.

The ECG shows the following: a ventricular rate of 117 beats/min; PR interval, 156 ms; QRS duration, 104 ms; QT/QTc interval, 346/482 ms; P axis, 65°; R axis, 148°; and T axis, 35°. What is your interpretation of this ECG?

ANSWER

The ECG shows sinus tachycardia, right atrial enlargement, and right axis deviation. Sinus tachycardia is defined as a sinus rhythm (consistent, single P wave for each QRS complex) at a rate exceeding 100 beats/min. Right atrial enlargement criteria include a P-wave amplitude exceeding 2.5 mm in lead II and/or exceeding 1.5 mm in V₁.

Right-axis deviation is defined as a QRS axis of more than 90°. Note that the normal QRS axis is between –30 and 90°, while a QRS axis more negative than –30° is designated a left-axis deviation. Right-axis deviation is evident when the electrical vector forces are moving to the right more than normally—in our patient, as a result of right atrial enlargement and right ventricular hypertrophy. Finally, the presence of a left ventricular mass is not seen on an ECG, as it has no electrical properties.