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Dr. Raimundas Lekas
Permanent atrial fibrillation patients with bimodal or polymodal R wave to R wave interval histogram patterns may be suitable candidates for radiofrequency catheter modification of the AV node.
Chaotic electrical and mechanical activity in the heart causing impaired contractility defines atrial fibrillation (AF). Prevelance in the developed world is 1.5–2% and with it, ensue hemodynamic and thromboembolic events that are responsible for significant morbidity and mortality (1-2).Catheter techniques are used for ablation of usually existing, so-called fast or slow AV nodal pathways for the treatment of tachyarrhythmias. The ablation of not all the atrioventricular (AV) node but part (one or more than one) of AV pathways is referred to as AV node modification - i.e modification of AV conductivity.The atrioventricular (AV) nodal dual-pathway theory holds that AV nodal pathways associated with chronic atrial fibrillation are present on rhythmogram (3). Meanwhile, more than one third (38.8%) of patients with permanent atrial fibrillation in previous studies had two, three, or four AV nodal pathways (4,5). We suggest that the number of AV nodal pathways discovered in our study subjects represents the number that would be found in the atrial fibrillation population at large (usually two or more) (5,15). Furthermore, we suggest that the number of peaks on RR interval histogram shows the number of AV pathways, and allow us to make a decision regarding recommendation for treatment- ablation or modification of the AV node.
Analysis of heart rate variability, RR interval histograms and Lorenz plots are among the methods to assess RR intervals however, to identify the underlying atrial fibrillation pathomechanisms and predict the best therapy and its efficacy, various methods have been suggested:
Our study included 64 patients with AF only suitable for recording R-R intervals histograms and its analysis (not treatment). Recruited patients were already treated for AF in Kaunas Clinics. Sinus rhythm was restored by catheter ablation in 19 patients. Coronary artery disease was commonly associated with the atrial fibrillation; concomitant disease in 67% of patients was hypertensive heart disease. In all patients with atrial fibrillation and patients with restoration of sinus rhythm by catheter ablation, 500 RR intervals were recorded in each position: supine during an active orthostatic test, upright, and again in the supine position and after exercise tests (9). Following successful ablation using radiofrequency energy, the examination of patients was repeated the next day (Fig. 1). The long succession of RR intervals was analysed using a von Neuman method (10) and computerised rhythmogram analysis for diagnosing atrial fibrillation (11, 12). In all histograms between 0.2 s and 1.2 s, the RR intervals were classified into 0.025 or 0.05 s wide subgroups. According to the number of peaks, three types of RR interval histograms were distinguished: (a) unimodal, (b) bimodal, (c) and polymodal. The number of peaks in each patient’s RR interval histogram was measured.
The mean age of patients was 64+-9 years, 26% of them were female. The duration of chronic atrial fibrillation was 8.8+-7.3 years. Computer-based analysis of the histograms in patients with atrial fibrillation showed that a single peak was present in 45% of patients, 40% of patients had two peaks, and 15% of patients had three or more peaks. After radiofrequency ablation, ventricular rate (before ablation RR1=0.79+-0,14s, after ablation RR2=0,99+-0.12s) and general heart rate variability (before ablation +-1=0.16+-0.03s, after ablation +-2=0.03+-0.01s) decreased with loss of the peak of short RR cycles after ablation. Presented values are means ± SD. In patients with atrial fibrillation with bimodal and polymodal histograms, the number of peaks decreased in all cases after successful radiofrequency catheter ablation (Fig. 2). Therefore our data showed that two or more peaks on the RR interval histogram with atrial fibrillation suggest the presence of multiple AV nodal pathways.We compared our results from derived from RR interval histogram computer-based analysis with data from other studies that included patients with atrial fibrillation with unimodal, bimodal, and polymodal RR interval histograms (3, 5, 13, 14). The number of peaks differs in various studies. Our investigations showed that radiofrequency catheter ablation is an effective and fast method for treatment of patients with chronic atrial fibrillation. According to our and literature data (8), this method may prove to be useful in selecting patients with atrial fibrillation who are considered appropriate candidates for radiofrequency modification of AV nodal conduction as opposed to AV nodal ablation. The patients with bimodal or polymodal pattern of RR interval histogram may be more suited for radiofrequency catheter modification of the AV node. Patients with a unimodal pattern may be inappropriate candidates for radiofrequency modification of the AV node and should be referred primarily for AV junction ablation and pacemaker implantation (9).
Fig. 1 A: RR intervals during atrial fibrillation in supine position, B: RR intervals in supine position after restoration of sinus rhythm by radiofrequency ablation. Nr – serial number of RR interval. S – time scale in seconds.Fig. 2 A: Bimodal RR interval histogram during atrial fibrillation, B: Unimodal RR interval histogram after restoration of sinus rhythm by radiofrequency ablation. The curves on A and B represents Gaussian and experimental RR intervals distribution modes. Hr – heart rate, S – time scale in seconds.
1. ESC Guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation: The Task Force for the management of acute coronary syndromes (ACS) in patients presenting without persistent ST-segment elevation of the European Society of Cardiology (ESC).Hamm CW et al. Eur Heart J 2011;32:2999-3054.2. ACC/AHA/ESC guidelines for the management of patients with atrial fibrillation. A Report of the American College of Cardiology/ American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines and Policy Conferences (Committee to Develop Guidelines for the Management of Patients With Atrial Fibrillation). JACC 2001;38:1-70.3. Double-sector Lorenz plot scattering in an R-R interval analysis of patients with chronic atrial fibrillation: incidence and characteristics of vertices of the double-sector scattering.Oka T, Nakatsu T, Kusachi S, et al. Electrocardiol 1998;31(3):227-35.4. AV nodal pathways in the R-R interval histogram of the 24-hour monitoring ECG in patients with atrial fibrillationWeismuller P, Kratz C, Brandts B, Kattenbeck K, Trappe HJ, Ranke C. Ann Noninvasive Electrocardiol 2001;6(4):285-9.5. Multiple AV nodal pathways with multiple peaks in the RR interval histogram of the Holter monitoring ECG during atrial fibrillation. Pacing Clin Electrophysiology 2000;23(11 Pt 2):1921-4. Weismuller P, Braunss C, Ranke C, Trappe HJ.6. Methodological aspects of the use of heart rate stratified RR interval histograms in the analysis of atrioventricular conduction during atrial fibrillation.Cai NS, Dohnal M, Olsson SB. Cardiovasc Res 1987;21(6):455-62.7. Bimodal RR interval distribution in chronic atrial fibrillation: impact of dual atrioventricular nodal physiology on long-term rate control after catheter ablation of the posterior atrionodal input. Tebbenjohanns J, Schumacher B, Korte T, et al. J Cardiovascular Electrophysiology 2000;11(5):497-503.8. Atrioventricular node modification in patients with chronic atrial fibrillation: role of morphology of RR interval variation. Rokas S, Gaitanidou S, Chatzidou S, et al. Circulation. 2001; 103(24):2942-8.9. A non-invasive method for the detection of dual atrioventricular node physiology in chronic atrial fibrillation. Rokas S, Gaitanidou S, Chatzidou S, et al. Am J Cardiol 1999;84:1442-5.10. Analysis of RR intervals in patients with atrial fibrillation at rest and during exercise.Bootsma B, Hollen A, Strackee J, et al. Circulation 1970;41:783-94.11.Von Neuman J. Distribution of the ratio of the mean square successive difference to the variance. Ann Math Stat 1941;12:367-95.12. Peculiarities of heart rate variability and autonomic nervous control during atrial fibrillation and after restoration sinus rhythm by electrical cardioversion, medical and catheter ablation. Vaičiulytė R., Lekas R. Proceadings of International Conference “Biomedical Enginering”, Kaunas, 2009;p.45-4713. RR interval histograms and power spectrum components in atrial fibrillation.Vaičiulytė R, Kaukėnas J, Pečiulienė I.. Scandinavian Baltic Meeting on Cardiac Arrhythmias held in Stockholm, Sweden, 1994; p. 102.14. Analysis of surface electrocardiograms in atrial fibrillation: techniques, research, and clinical applications. Bollmann A, Husser D, Mainardi L, Lombardi F, et al. Europace 2006;8(11):911-26.15. Multiple AV nodal pathways in patients with AV nodal reentrant tachycardia-more common than expected? Heinroth KM, Kattenbeck K, Stanbenow I, Weismuller P. Europace 2002 4(4):375-82.
Rūta Vaičiulytė, Raimundas Lekas, Genuvaitė Civinskienė, Viktoras Lekas, Jonas Andriuškevičius, Jurga BernatonienėCorrespondence:Lekas RaimundasLUHS, Institute of Cardiology50009 Kaunas, Eiveniu 4, LithuaniaAuthors' disclosures: None declared