Published on
Download the article PDF: Clinical Image Challenges May 2026
Differential Diagnosis
- Atrial fibrillation
- Sinus tachycardia
- Supraventricular tachycardia
- Multifocal atrial tachycardia
- Atrial flutter
Diagnosis
The diagnosis in this case is atrial fibrillation with rapid ventricular response. The ECG reveals an irregularly irregular rhythm with narrow QRS complexes and a ventricular rate of 125 beats per minute. There are no discernible P waves.
Discussion
The presence of an irregularly irregular rhythm is indicated by R-R interval irregularity with no discernible pattern to the irregularity. The differential diagnosis for an irregularly irregular rhythm includes atrial fibrillation (most common), atrial flutter with variable conduction, and multifocal atrial tachycardia. Both atrial flutter and multifocal atrial tachycardia show organized atrial activity, whereas atrial fibrillation does not.
Atrial fibrillation is the most common arrhythmia, with an annual incidence in patients older than 65 years of 24 per 1,000 person-years.1 There are many causes including valvular pathology, hypertension, heart failure, ischemia, electrolyte derangements, thyrotoxicosis, and excessive alcohol consumption.2 Management is guided by identifying and treating primary pathology, rate or rhythm control, and stroke risk reduction.
Atrial fibrillation increases stroke risk approximately fivefold.3 The mainstay of stroke prevention is anticoagulation. Tools like the CHA2DS2-VASc score can help with risk stratification and guide anticoagulation decisions.2 Patients with onset of atrial fibrillation within 12-48 hours might be candidates for early cardioversion, and emergency department referral should be considered. In the absence of alternative primary pathology, rate control (ie, heart rate goal of less than 110 beats per minute) with atrioventricular nodal blocking agents can be pursued but should be performed in a monitored setting.2,4,5 Patients with hemodynamic instability (eg, hypotension, altered mental status, ischemic chest pain, or acute heart failure) should be immediately cardioverted.
This patient was referred to an emergency department, where the providers elected to perform rate control.
What To Look For
- Irregularly irregular rhythms are defined by randomly changing R-R intervals over time (ie, no discernable pattern).
- The differential for irregularly irregular rhythms includes atrial fibrillation, atrial flutter with variable conduction, and multifocal atrial tachycardia.
- Early management of new-onset atrial fibrillation involves identification of underlying pathology and potentially rhythm or rate control.
Pearls For Initial Management, Considerations For Transfer
- Refer symptomatic patients or patients needing urgent identification and/or treatment to an appropriate emergency department.
- Place pads on the patient if unstable while awaiting transport.
- Cardioversion is the preferred strategy for hemodynamically unstable atrial fibrillation.
References
- Khurshid S, Ashburner JM, Ellinor PT, et al. Prevalence and Incidence of Atrial
Fibrillation Among Older Primary Care Patients. JAMA Netw Open. 2023; 6(2):e2255838. doi:10.1001/jamanetworkopen.2022.55838 - Joglar JA, Chung MK, Armbruster AL, et al. 2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Atrial Fibrillation: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. Circulation. 2024;149(1):e1-e156. doi:10.1161/CIR.0000000000001193
- Wolf PA, Abbott RD, Kannel WB. Atrial fibrillation as an independent risk factor for stroke: the Framingham Study. Stroke. 1991;22(8):983-988. doi:10.1161/01.str.22.8.983
- Andrade JG, Aguilar M, Atzema C, et al. The 2020 Canadian Cardiovascular Society/Canadian Heart Rhythm Society Comprehensive Guidelines for the Management of Atrial Fibrillation. Can J Cardiol. 2020;36(12):1847-1948. doi:10.1016/j.cjca.2020.09.001
- Van Gelder IC, Rienstra M, Bunting K V, et al. 2024 ESC Guidelines for the management of atrial fibrillation developed in collaboration with the European Association for Cardio-Thoracic Surgery (EACTS). Eur Heart J. 2024;45(36):3314. doi:10.1093/eurheartj/ehae176
