A 72-year-old male with a past medical history of hypertension, type 2 diabetes, hyperlipidemia, atrial fibrillation, coronary artery disease (CAD) with triple-vessel disease, heart failure with a known ejection fraction (EF) of approximately 30%, chronic mesenteric ischemia, and liver cirrhosis presents to the emergency department (ED) with complaint of bilateral lower extremity swelling. An initial ECG was obtained in triage (Figure 1).
Interpretation:
Rate: 42 bpm; Rhythm: atrial fibrillation with bradycardia, PVCs, incomplete versus total right bundle branch block, and left anterior fascicular block; Axis: indeterminate to left axis deviation (I: eqv., II: neg., aVF: neg) Intervals: PR: absent; QRS: 110-120, wide; QT: 457, prolonged; P-Waves: absent; QRS Complex: low voltage, wide; ST Segment/T-waves: T wave flattening in limb leads, no ST elevations or depressions, no abnormal T wave inversions
The patient states that he is taking aspirin, atorvastatin, empagliflozin, furosemide, hydralazine, lisinopril, isosorbide mononitrate, and rivaroxaban. He is not taking any rate controlling agents. The blood pressure in triage is 133/91, and the patient is not currently experiencing any cardiopulmonary symptoms.
A brief chart review revealed that the patient had known atrial fibrillation with slow ventricular response (SVR) and had previously been evaluated by both Cardiology and Electrophysiology (EP). The patient had previously been offered but declined permanent pacemaker (PPM), coronary artery bypass graft (CABG), and implantable cardioverter-defibrillator (ICD) placement.
Aside from the heart rate, what is concerning about this patient’s initial ECG? What are your next steps in management?
Discussion:
Patients with multiple electrophysiological abnormalities, as seen on this index ECG, and significant coronary artery disease can be extremely difficult to management in the ED. The approach to management of atrial fibrillation with SVR also requires a nuanced approach to ensure the patient remains hemodynamically stable throughout management.
In this case, the patient had a history of triple-vessel CAD and significant heart failure, and the index ECG has three significant electrophysiological abnormalities to make note of:
Atrial fibrillation with bradycardia,
Incomplete versus total right bundle branch block (RBBB), and
Left anterior fascicular block (LAFD)
Right bundle branch block is defined as a QRS >120ms; RSR’ pattern in leads V1-V3; and slurred S wave in leads I, aVL, and V5-V6. Left anterior fascicular block is defined as left axis deviation (I: pos., II: eqv./neg., aVF: neg); qR complexes in leads I and aVL; and rS complexes in leads II, III, and aVF (Figure 2).
Figure 2. Index ECG with identification of notable EP abnormalities.
Bifascicular block is attributed to ischemic heart disease in 40-60% cases and has a 50-80% association with structural heart disease. Specifically, RBBB + LAFB is typically caused by CAD to a single coronary artery vessel - namely, the left anterior descending (LAD) artery - to the anterior fascicle. RBBB + LAFB carries an annual risk of progression to complete heart block in 1-4% of cases (1).
The low voltage of this ECG makes some of these ECG findings hard to clearly determine. However, given the clinical context of known ischemic heart disease (CAD with triple-vessel involvement), structural heart disease (heart failure with reduced EF of 30%), bradycardia, and possible bifascicular block, these findings should be highly concerning for near-total heart block requiring Cardiology consultation for PPM placement.
Atrial fibrillation with SVR may also be a sign of atrioventricular (AV) nodal blockade, which is frequently found to be caused by AV nodal blocking drugs, electrolyte abnormalities, or hypothermia (2). However, in this case, none of these extrinsic factors were present, leaving intrinsic conduction system disease as the likely cause. The importance of promptly addressing this ECG finding was demonstrated in a study conducted in 2023. The outcomes of a total of 496 patients (mean age, 73±11 years; male, 53.7%) who presented with atrial fibrillation-related stroke were evaluated. Thirty-one patients (6.2%) had SVR. Despite no difference in demographics or vascular risk factors compared to patients with normal atrial fibrillation or atrial fibrillation with rapid ventricular response (RVR), these patients also had higher initial NIHSS scores, larger DWI lesion volumes on CT, and larger left atrial diameters compared to those without SVR (3).
Take Away Points:
All patients with new atrial fibrillation with SVR should be admitted for Electrophysiology evaluation and Cardiology consultation.
Common causes for atrial fibrillation with SVR include electrolyte abnormalities, hypothermia, and AV nodal blocker use/overdose. Less commonly, intrinsic causes (i.e. ischemic versus structural heart disease) are at play.
All bifascicular blocks (especially those, as in this case, with a third “blocked” pathway with decreased AV nodal conduction) should be managed in consultation with Cardiology.
Authored by Michael Hohl, MD; Taylor Wahrenbrock, MD; and Ari Edelheit, MD.
References:
Burns, E., Buttner, R., & Buttner, E. B. and R. (2024, October 8). Bifascicular Block. Life in the Fast Lane • LITFL. https://litfl.com/bifascicular-block-ecg-library/
Dobariya V, Ezeh E, Suliman MS, Singh D, Teka S. Unusual Presentation of Atrial Flutter With Slow Ventricular Response. Cureus. 2021;13(6):e15801. Published 2021 Jun 21. doi:10.7759/cureus.15801
Ha SH, Jeong S, Park JY, et al. Association Between Slow Ventricular Response and Severe Stroke in Atrial Fibrillation-Related Cardioembolic Stroke. J Stroke. 2023;25(3):421-424. doi:10.5853/jos.2023.01753