ECG Challenge

Woman with Metabolic Syndrome

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A 50-year-old woman with metabolic syndrome presents for a routine clinic appointment. You quickly review the five criteria of metabolic syndrome: • Fasting blood glucose ≥ 110 mg/dL • Waist circumference ≥ 40” in men or ≥ 35” in women • Triglycerides ≥ 150 mg/dL • HDL cholesterol < 40 ¬mg/dL in men or < 50 mg/dL in women • Blood pressure ≥ 130/85 mm Hg. The patient’s last clinic visit was four months ago; since then, she has done well and has no specific complaints or concerns. She denies angina, palpitations, dizziness, syncope, or dyspnea. Medical history is significant for New York Heart Association class III heart failure and cardiomyopathy secondary to myopericarditis with small-vessel coronary artery disease, as well as depression with anxiety. She also has a history of obstructive sleep apnea, but refuses to use a constant positive airway pressure (CPAP) machine at night due to claustrophobia. She attempts to control her diabetes with diet and exercise but admits she isn’t very compliant. Her medication list includes amlodipine, furosemide, carvedilol, lisinopril, isosorbide dinitrate, hydralazine, spironolactone, simvastatin, citalopram, omeprazole, and oxybutynin. She is allergic to ampicillin, methocarbamol, and codeine. The patient’s family history is unknown, as she was adopted. She works as a comptroller for a municipality in the suburbs, is recently divorced, and does not smoke or drink. Her review of systems is remarkable for headaches, anxiety, and loneliness following her divorce. She denies thoughts of injuring herself or suicide. Physical examination reveals a blood pressure of 118/64 mm Hg; pulse, 88 beats/min and irregular; respiratory rate, 16 breaths/min-1; and temperature, 99.2°F. Her weight is unchanged from her last visit. Her lungs are clear bilaterally, the jugular venous pressure is approximately 4 cm, and her cardiac exam reveals no murmurs, rubs, or extra heart sounds. Her abdomen is benign, and she has strong pulses bilaterally with 1+ pitting edema in both lower extremities, limited to the ankles. Laboratory data demonstrate chemical and lipid profiles and complete blood count within normal limits. An echocardiogram performed at her previous visit showed a left ventricular ejection fraction of 45%, with a mildly enlarged left ventricle, normal right ventricular size and function, and no valvular anomalies. It has been a year since her last ECG, so you decide to order one. It reveals the following: a ventricular rate of 87 beats/min; PR interval, 138 ms; QRS duration, 86 ms; QT/QTc interval, 388/466 ms; P axis, 61°; R axis, 43°; and T axis, 9°. What is your interpretation of this ECG?


 

ANSWER
The correct interpretation of this ECG includes sinus rhythm with frequent premature ventricular complexes (PVCs), a T-wave ­abnormality suggesting lateral ischemia, and a prolonged QT interval.

PVCs occur when conduction of the ventricular myocardium occurs without involving the normal His-Purkinje system. They are responsible for the patient’s irregular pulse.

A prolonged QT interval is evidenced by a QTc interval > 440 ms. The QTc is calculated from Bazett’s formula, which states the QTc = QT interval divided by the square root of the previous R-R interval. The normal range for a QTc is generally considered to be 350 to 440 ms.

Inverted T waves in leads V3 to V6 are suggestive of lateral ischemia. However, they are also seen in subacute or old pericarditis and myocarditis, so clinical correlation is required. The patient has had no recent or remote episodes of chest pain or chest discomfort in the past year.

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