Regularly irregular rhythm
Also calledpatterned irregularity · grouped beating · group beating
Definition
A rhythm whose R-R intervals are unequal but vary in a repeating pattern rather than randomly, so the irregularity itself recurs. A classic example is second-degree AV block Mobitz I (Wenckebach): the PR interval lengthens while the R-R intervals shorten until a P wave is blocked, and the cycle repeats, producing grouped (group) beating. Premature beats that recur in a fixed pattern give another repeating pattern, for example ventricular bigeminy (a premature ventricular complex after every normal QRS) or trigeminy (one after every two normal QRS complexes).
Clinical noteA fixed conduction ratio, such as steady 2:1 block, gives a regular ventricular rhythm; the ventricular rhythm becomes irregular when the degree of block varies.
Sources
- Margulescu AD, Enescu OA, Vinereanu D. A regularly irregular rhythm: what is the diagnosis? Neth Heart J. 2016;24(2):156-158. doi.org/10.1007/s12471-015-0789-z
- Kusumoto FM, Schoenfeld MH, Barrett C, et al. 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay. Circulation. 2019;140(8):e382-e482. doi.org/10.1161/CIR.0000000000000628
- Samesima N, God EG, Kruse JCL, et al. Brazilian Society of Cardiology guidelines on the analysis and issuance of electrocardiographic reports - 2022. Arq Bras Cardiol. 2022;119(4):638-680. doi.org/10.36660/abc.20220623
- Koester C, Ibrahim AM, Cancel M, Labedi MR. The ubiquitous premature ventricular complex. Cureus. 2020;12(1):e6585. doi.org/10.7759/cureus.6585
- Goodacre S, Irons R. ABC of clinical electrocardiography: atrial arrhythmias. BMJ. 2002;324(7337):594-597. doi.org/10.1136/bmj.324.7337.594
Last reviewed 2 October 2026. Every definition in the EKG Dictionary cites the guideline, consensus statement or original paper it comes from.