A 20-year-old man with a history of Marfan syndrome presents for a routine clinic visit. A CT scan performed one year ago revealed an ascending aortic aneurysm measuring 4.7 cm. An echocardiogram performed six months ago showed no evidence of aortic insufficiency, left ventricular enlargement, or mitral regurgitation. An echocardiogram performed prior to today’s visit documents a left ventricular ejection fraction of 56% and no changes in left ventricular size or in aortic or mitral valve function.

The patient states that he has some degree of fatigue and occasional palpitations, but denies syncope, near-syncope, orthopnea, paroxysmal nocturnal dyspnea, or lower extremity edema. His medical history is remarkable for a fractured ankle sustained at age 6.  He is a student at a local community college who does not smoke and consumes alcohol occasionally on weekends. His only medication is lisinopril (1.25 mg/d); however, he often forgets to take it. He has no known drug allergies and does not use recreational drugs or herbal therapies.

Physical examination reveals a pleasant, tall, thin man in no acute distress. He is 187 cm tall and weighs 55.5 kg. His blood pressure is 122/70 mm Hg, and his pulse is 100 beats/min. He is afebrile. Pertinent physical findings include a very visible point of maximum impulse (PMI), which is located in the left anterior axillary line. There are no murmurs or rubs. He does not have lens subluxation on his eye exam, but does have very flexible joints in both hands. Indeed, he delights in showing his ability to “bend my fingers backwards.”  The remainder of the exam is unremarkable.

An ECG obtained prior to today’s echocardiogram shows the following: a ventricular rate of 100 beats/min; PR interval, 218 ms; QRS duration, 106 ms; QT/QTc interval, 360/464 ms; P axis, 51°; R axis, 43°; and T axis, 55°. What is your interpretation of this ECG?

ANSWER

The ECG reveals sinus tachycardia with a first-degree atrioventricular (AV) block and large QRS voltages in all leads. Sinus tachycardia occurs at rates of 100 beats/min or greater, with the impulse originating within the sinus node. First-degree AV block is evidenced by a PR interval of at least 200 ms.

The most pertinent findings, large QRS voltages in all (ie, limb and precordial) leads, are due to the patient’s body habitus. Voltages appear accentuated in tall, thin patients and are differentiated from ventricular enlargement by the presence of large QRS complexes in all leads.

Finally, careful inspection of the P waves (particularly in limb lead II and in V₁) suggests the possibility of left atrial enlargement. However, this was not documented on the echocardiogram. This finding can also be attributed to the patient’s body habitus.