A 53-year-old white man is referred for an adenosine myocardial perfusion scan stress test prior to left femoral popliteal bypass graft surgery.

An ECG obtained one month ago was interpreted as normal. A transthoracic echocardiogram at that time revealed a normal left ventricular ejection fraction (> 55%) with normal wall motion and no pathologic valvular heart disease. 

The patient is in distress due to left lower extremity vascular ischemic rest pain. He admits that earlier this morning, he was slightly dyspneic. However, he denies chest pain.

He admits to not taking aspirin (162 mg Q day) as prescribed for the past two days. He also reports an 88–pack-year smoking history. Pulmonary function tests support mild obstructive emphysematous changes.

The patient is 68” tall and weighs 128 lb (BMI, 19.5). His vital signs include: a blood pressure of 128/82 mm Hg; ventricular rate, 94 beats/min; respiratory rate, 20 breaths/min; and O₂ saturation, 90% on room air. He is afebrile.

Pertinent physical findings include no jugular venous distention and no bilateral carotid, femoral, or abdominal bruits. The neurologic exam is unremarkable.

The cardiac exam reveals a regular rate and rhythm with an S3 gallop; there is no S4, murmur, or click. There is no peripheral edema. Femoral pulses are +1. Pedal pulses are absent.

Stat cardiac enzymes reveal a normal CK-MB (3.3 U/L) and an elevated troponin T level (0.117 μg/L; normal, 0.00 to 0.03). The complete blood count, prothrombin time/partial thromboplastin time/INR tests, and other chemistry panels all yield normal results.

This patient’s ECG shows the following: a ventricular rate of 90 beats/min; PR interval, 135 ms; QRS duration, 96 ms; QT/QTc interval, 394/476 ms; P axis, 67°; R axis, 68°; and T axis, 172°. What is your interpretation of this ECG?

ANSWER
The ECG is diagnostic for a septal and anterolateral ST-elevated myocardial infarction (STEMI), suggestive of a recent MI versus left ventricular aneurysm. The ECG is also diagnostic for a recent inferior wall STEMI.

There are Q waves in leads V₁ to V₅ and a 2-mm ST elevation in V₂ to V₆, as well as a T-wave inversion (TWI) in V₂ to V₆ and lead 1. A 1-mm ST elevation, TWI, and small Q waves are noted in leads II, III, and aVF (inferior leads).

The patient’s abnormal troponin T level assisted with the differential diagnosis. The patient’s normal CK-MB pattern, combined with an elevated troponin T with ECG changes and chest pain reported about one week earlier, supported the diagnosis of a recent acute MI (within the past week). 

The stress test was canceled. Cardiac catheterization was performed and showed a 100% mid left anterior descending (LAD) stenosis, with left to left collaterals, and an 80% right coronary artery (RCA) stenosis. No left ventricular aneurysm was noted.

Interventions included an urgent percutaneous intervention (PCI) coronary stent placement to the LAD and a staged PCI to the RCA at a later date.