The Case:
A 72yo M presents via EMS for chest pain that started while chopping wood. Initially, an ECG was sent by EMS en route with concern for ST-segment elevation. 324 mg PO aspirin and 400 mcg of sublingual nitroglycerin were administered prior to arrival. Vitals per EMS were notable for bradycardia and hypotension.
Rate?
Rhythm?
Axis?
Intervals?
QRST?
Interpretation:
Bradycardia with ventricular rate of approximately 35 bpm, 3rd-degree heart block with desynchrony of p waves and QRS complexes, normal axis, normal QRS/QT with PR not calculated, 2-3mm ST segment elevation in II/II/aVF with reciprocal depression in the precordial leads and aVL.
Case Conclusion:
The patient’s bradycardia was managed with 0.5mg of atropine without effect, followed by transcutaneous pacing at a rate of 60 with capture at 70mA. Point-of-care echocardiography was notable for bradycardia with global hypokinesis and dissociation of atrial and ventricular contractions. Interventional cardiology was already present in the ED, and the cath lab was activated. The patient went to the cath lab 19 minutes after arrival.
Discussion:
This ECG demonstrates an inferior STEMI with associated AV nodal block/3rd-degree heart block. Fortunately, he remained relatively hemodynamically stable but was started on transcutaneous pacing due to MAP <65. This ECG demonstrates several hallmarks of an inferior STEMI, including the commonly seen ST segment changes in the inferior leads, reciprocal changes in aVL, and 3rd-degree heart block (1). Commonly, the heart block is transient and can respond to atropine. The traditional teaching is to avoid medications that alter preload (such as nitroglycerin) in patients with right-sided infarction, as this can lead to hemodynamic instability (2).
In this patient, ST segment depression is noted in the precordial leads, which may indicate posterior extension of the inferior STEMI. This patient had global CAD with CABG/PCI 10 years prior, but interestingly, the cath report noted only a distal RCA occlusion.
Authored by Stewart Pine, MD
References:
Warner MJ, Tivakaran VS. Inferior Myocardial Infarction. [Updated 2023 Feb 12]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK470572/
Lizzo JM, Chowdhury YS. Posterior Myocardial Infarction. [Updated 2023 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK553168/