A 65-year-old male presents to the Emergency Department with cough, malaise, and fevers to 39°C. His past medical history is notable for hypertension, diabetes, and a drug-eluting stent placed into his distal right coronary artery 5 years before angina. He has no anginal symptoms at rest. He takes aspirin, atorvastatin, metoprolol, lisinopril, and metformin. Testing with viral panel in the Emergency Department resulted in positive PCR for Influenza A. Electrocardiogram shows:
and a Troponin-T is <0.01 ng/mL. Over the course of the first 2 hours after presentation, he becomes increasingly hypoxemic, ultimately transferred to the ICU after intubation. His chest radiograph before intubation shows bilateral infiltrates. Oxygenation slowly improves over the next 12 hours. The morning after admission, he is noted to have a short run of wide complex tachycardia. Electrocardiogram shows new left bundle branch block (LBBB). He then continues to have frequent regular wide complex tachycardias, causing hemodynamic instability. Troponin-T now increases to 0.48 ng/mL.
Which of the following is the BEST next step in managing his cardiac status?
A. Cardiac catheterizationCorrect Answer: A
The recurrent tachyarrhythmias that appear to be ventricular in origin in association with hemodynamic instability and rising troponin-T is concerning for active myocardial ischemia. This supports performing cardiac catheterization for diagnosis and potential reperfusion. In the absence of hemodynamic instability, a more conservative approach with echocardiogram and serial troponin-T would be a reasonable alternative. However, LBBB would cause paradoxical septal motion on echocardiography, which may confound assessment of focal wall motion abnormalities as part of the ischemic evaluation.
Though prior guidelines associate a new LBBB with ischemia, recent studies have questioned this assumption. Studies show that a new LBBB is rarely caused by acute transmural ischemia. Thus, the 2013 ST elevation myocardial infarction guidelines urge a more holistic assessment based on cardiac biomarkers, ECG criteria for myocardial infarction, and clinical scenario.
Though cardiac MRI is being evaluated as an alternate diagnostic modality for ischemia, it currently has no role in a hemodynamically unstable patient. A CT Pulmonary Angiogram would be useful if pulmonary embolism was being considered but is unlikely based on this patient’s clinical presentation.
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