A 67-year-old man awoke with severe lightheadedness and nausea. About 30 minutes later, he had an episode of emesis, followed by crushing pressure in his anterior chest and shortness of breath. His wife contacted EMS, and paramedics arrived within four minutes. They administered two sublingual nitroglycerin tablets, which resulted in prompt resolution of all symptoms, and transported the patient to your facility.

The patient has coronary artery disease (CAD), diagnosed three years ago. A cardiac catheterization at that time showed a right coronary artery dominant circulation with a discrete 30% stenosis of the distal left main coronary artery, diffuse disease in the left anterior descending artery, 50% stenosis in the mid-circumflex artery, and a left ventricular ejection fraction of 54%. The patient was managed medically and has been asymptomatic for two years.

Medical history is also remarkable for type 1 diabetes, hypertension, obstructive sleep apnea, chronic renal insufficiency, and recurrent polyarticular gout in both ankles. Surgical history includes an umbilical hernia repair and a left carpal tunnel release.

The patient does not smoke and rarely drinks alcohol. His medications include insulin glargine, insulin lispro (sliding scale), isosorbide mononitrate, lisinopril, diltiazem, furosemide, aspirin, rosuvastatin, and colchicine as needed. He uses a bilevel positive air pressure device when sleeping and has no drug allergies.

Physical examination reveals a blood pressure of 114/50 mm Hg; pulse, 50 beats/min; respiratory rate, 18 breaths/min; temperature, 36.6°C; and O2 saturation, 99% on 2 L of O2. His weight is 345 lb.

The pulmonary exam reveals scattered dry crackles at the right base that clear with a deep breath. The cardiovascular exam is significant for bradycardia with a regular rhythm, distant heart sounds, a grade II/VI systolic ejection murmur best heard at the right upper sternal border, and no gallops or rubs. There is no jugular venous distention. Pulses are equal in all extremities, and trace pedal edema is present bilaterally. The neurologic exam is intact, and there are no skin lesions.

Stat lab results include a first cardiac troponin T level < 0.04 ng/mL and a creatinine kinase level of 94 IU/L. An ECG shows the following: a ventricular rate of 48 beats/min; PR interval, 160 ms; QRS duration, 106 ms; QT/QTc interval, 418/373 ms; P axis, 41°; R axis, 59°; and T axis, 50°. What is your interpretation of this ECG?

ANSWER

The correct diagnosis is marked sinus bradycardia. The rhythm originates in the sinus node and conducts normally down the atrioventricular node and His-Purkinje system. The R-R intervals are regular, all waveforms are present, and there is one P wave for every QRS complex. ST elevations may appear to be elevated in leads V1 to V3 but are not diagnostic.

The patient subsequently had cardiac enzyme elevations and underwent cardiac catheterization, which revealed significant left anterior descending coronary artery disease. He was treated with two coronary artery stents.

This case illustrates the value of serial ECG to make an accurate diagnosis of acute coronary syndrome. Reliance on this ECG alone would have missed the diagnosis; fortunately for this patient, subsequent ECGs were taken during his visit.