European Journal of Cardiovascular Medicine

Atrioventricular re-entrant tachycardia (AVRT) is a form of paroxysmal supraventricular tachycardia caused by the presence of an accessory pathway (AP) connecting the atrium to the ventricle, bypassing the atrioventricular (AV) node.[1-3] AVRT accounts for 30–40% of all PSVT cases and is the characteristic arrhythmia of Wolff–Parkinson–White (WPW) syndrome, where patients demonstrate pre-excitation on the electrocardiogram (ECG) with a short PR interval and delta wave.[1-3] Accessory pathways can be categorized as manifest (with pre-excitation evident on baseline ECG, constituting classic WPW syndrome) or concealed (conducting only in the retrograde direction, without visible pre-excitation at rest, accounting for approximately 30% of SVTs referred for electrophysiologic studies).[3, 4]

Patients with AVRT typically present with sudden-onset, regular palpitations at heart rates exceeding 150 bpm, often accompanied by dyspnea, chest discomfort, or presyncope.[5]

The clinical presentation can be paroxysmal, with episodes spontaneously terminating or persisting until medical intervention is required. Initial acute management includes vagal maneuvers and adenosine administration; however, for symptomatic patients seeking long-term cure or those with recurrent episodes despite antiarrhythmic therapy, catheter-based radiofrequency ablation has emerged as the definitive treatment of choice.[1, 2]

Radiofrequency catheter ablation of accessory pathways has achieved remarkable success rates of 94–99% with major complication rates of only 1–2%, demonstrating excellent safety and efficacy.[1, 5, 6] The procedure employs 2D electrophysiological mapping to precisely localize the accessory pathway by site (left free wall, posteroseptal, right free wall, or anteroseptal), followed by targeted energy delivery to create an ablation lesion that permanently blocks retrograde conduction through the AP.[4, 7] Despite these excellent international outcomes, data from Himalayan and tribal hill populations remain sparse, as geographic and resource constraints often limit access to specialized electrophysiology services in remote regions.[1]

This study addresses this knowledge gap by describing the prevalence, characteristics, and outcomes of accessory pathway-mediated AVRT in the hill population of Sikkim, a Himalayan state in Northeast India. We present a series of 77 patients with AVRT who underwent 2D electrophysiological study and radiofrequency ablation at STNM Hospital, Gangtok, with particular emphasis on the high clinical success rate and excellent short-term durability of the procedure in this unique population.

2.1 Study design and setting

This was a hospital-based descriptive cross-sectional study conducted in the Department of Cardiology, STNM Hospital, Gangtok, a tertiary care government center and teaching hospital in Sikkim, India. The analysis focuses specifically on the subset of 59 patients with accessory pathway-mediated AVRT who underwent 2D electrophysiological study and RFA between January 2019 and December 2025.

2.2 Study population and eligibility

All consecutive patients with AVRT (documented narrow complex tachycardia with accessory pathway participation, either manifested as WPW syndrome or concealed) who were discharged on antiarrhythmic medication and planned for elective 2D EPS and RFA were eligible. Patients with incomplete records on key variables (age, sex, accessory pathway characteristics, or ablation status) were excluded. The final analytic sample comprised 77 AVRT patients, drawn from a larger cohort of 185 PSVT patients who underwent EPS during the study period.

2.3 Data collection and variables

Standardized records and procedure forms were used to extract:

• Demographic variables: age, sex.

• Community/ethnicity as documented in hospital records.

• Accessory pathway characteristics: manifest (pre-excitation on baseline ECG) versus concealed (retrogradely conducting only).

• Ablation details: The ablation procedure was performed using the Workmate Claris System ( Jude Medical Inc.) with EP4 Cardiac Stimulator for electrophysiological testing and Ampere RF generator for energy delivery. Multiple catheters were employed in accordance with standard radiofrequency ablation protocol. The Decapolar EP catheter (Biosense Webster Inc.) was positioned in the coronary sinus for comprehensive electrogram mapping and to localize left-sided accessory pathways; the Fixed Quadripolar EP catheter (Biosense Webster Inc.) was placed across the AV node to record His bundle electrograms and guide ablation timing; and the Ablation MAP catheter (Biosense Webster Inc.) with integrated temperature feedback via the Thermocouple C curve catheter (Biosense Webster Inc.) was used for precise lesion delivery at the AP site, with temperature-guided radiofrequency energy titrated to typically 50–70°C and power output of 30–50 watts for 30–60 seconds per lesion.

• Short-term outcomes: arrhythmia recurrence at 6 months and 1-year post-ablation.

* Age was grouped as, 22–40 and  years to reflect adolescence/early adulthood, peak working age and older adults. Long-term procedural and clinical outcomes were assessed at 6 months and 1 year follow-up.

2.4 Statistical analysis

Data was entered into a spreadsheet and checked for internal consistency. Categorical variables are presented as frequencies and percentages. For ablated patients, success and recurrence rates were calculated from the 77 AVRT patients who underwent RFA. No formal hypothesis testing was undertaken, as the primary objective was descriptive.

2.5 Ethical considerations

This analysis was planned as a service evaluation. Administrative approval was obtained from hospital authorities, and Ethical approval was obtained from Institutional Ethics Committee for retrospective approval in line with national guidance. Patient identities were anonymized, and no identifiable information is reported.

3.1 Electrophysiological diagnosis and RFA outcomes

Table 1 summarizes the Electrophysiological diagnosis and RFA outcomes for the entire PSVT cohort. Of 185 PSVT patients, 77 (41.6%) had accessory pathway-mediated SVT (AVRT), while 108 (58.4%) had AVNRT or other non-pathway tachycardia. RFA was performed in 158 patients (85.4%), and 155 of these (98.1%) remained asymptomatic at 6 months and 1 year, with only 3 patients (1.9%) experiencing recurrence.

Table 1. Electrophysiological Diagnosis and RFA Outcomes in Total PSVT Cohort (N = 185)

Represents the breakdown of the complete PSVT cohort (n=185) showing that AVRT accounts for 41.6% of all diagnoses.

3.2 Demographic characteristics

Of the 77 AVRT patients, the mean age was 37.5 years with distribution as follows: 12 patients (15.5%) were aged  years, 32 patients (41.5%) were aged 22–40 years, and 33 patients (43.8%) were aged above 40 years. The cohort was nearly equally distributed by sex, with 38 males (49.3%) and 39 females (50.6%), demonstrating an absence of marked gender predominance in accessory pathway-mediated PSVT within this hill population. This balanced sex distribution contrasts with some international series that report female predominance in PSVT overall.[5, 8]

3.3 Accessory pathway characteristics and AVRT-specific outcomes

Among the 77 AVRT patients, 54 (70.1%) had manifested accessory pathways (evident as WPW pattern on resting ECG), while 23 (29.8%) had concealed accessory pathways that conducted only retrogradely during tachycardia. All 77 patients underwent successful 2D electrophysiological localization of the AP and subsequent radiofrequency ablation with a 100% procedural completion rate.

Among these, 76 patients (98.7%) were asymptomatic at both 6-month and 1-year follow-up with no recurrence of AVRT. Only 1 patient (1.3%) experienced recurrence of accessory pathway-mediated AVRT within the first-year post ablation. The acute success rate of RFA in the AVRT cohort was 98.7%, defined as elimination of accessory pathway conduction (loss of pre-excitation in manifest pathways and failure to induce AVRT on repeat EP testing). No major complications including AV block, cardiac tamponade, or stroke were reported in this cohort.

3.4 Community/ethnicity distribution in AVRT patients

The 77 AVRT patients reflected the multiethnic composition of Sikkim, with representation across 12 different communities. Detailed demographic, ethnic, and outcome characteristics are presented in Table 2.

Table 2. Demographic, Sex, Age, Ethnicity, and RFA Outcome Characteristics in AVRT Patients (n = 77)

Percentages are calculated over n = 77 AVRT patients.

*Fold difference = (Cohort %) / (Census %); values >1.0 indicate over-representation. Notable enrichment observed for Bhutia (2.7×), Scheduled Caste (3.8×), and Rai (1.6×), while under-representation noted for Chettri/Bahun (0.2×). Census % from Sikkim census data 2011.[9, 10]

This single-center study documents the high prevalence and excellent outcomes of accessory pathway-mediated AVRT in a Himalayan hill population. Among 185 consecutive patients with PSVT, 77 (41.6%) had AVRT, representing a substantial proportion comparable to published international series reporting AVRT prevalence of 30–40% in unselected PSVT cohorts.[1] In certain geographic regions such as China, AVRT prevalence can be even higher, suggesting variable epidemiological patterns across populations.[3, 11] The predominance of manifest pathways in 70.1% of our AVRT patients reflects the high diagnostic clarity afforded by recognizing WPW pattern on baseline ECG, while concealed accessory pathways (29.8%) underscore the importance of comprehensive electrophysiological testing to unmask pathways that only conduct retrogradely.[3, 4]

The nearly equal sex distribution (49.3% male, 50.6% female) in our AVRT cohort is notable and differs from some published series that report female predominance in PSVT overall.[5, 8] This balanced distribution may reflect population-specific epidemiological factors or differences in treatment-seeking behavior across genders in the hill population of Sikkim. The age distribution demonstrates substantial representation across all age groups, with nearly 40% of patients in the peak working years (22–40), emphasizing the clinical impact of AVRT on productivity and quality of life in this economically active population.

The acute radiofrequency ablation success rate of 98.7% in this study is at the forefront of international performance standards. Contemporary large multicenter series report acute RFA success rates for accessory pathway ablation ranging from 93–99%, with our result aligning closely with these benchmarks.[1, 2, 6, 12] The 1-year recurrence rate of 1.3% (1/77 patients) is remarkably low and compares favorably with published rates of 3–12%, suggesting excellent technical execution and durable lesion formation.[5-7, 13]

The complete absence of major complications in this 77-patient AVRT cohort is noteworthy. While international series report major complication rates of 1–3% for accessory pathway ablation (including AV block, tamponade, stroke, and perforation), our center’s zero major complication rate reflects meticulous procedural technique, careful patient selection, and real-time monitoring capabilities afforded by the Workmate Claris System with integrated 2D electrophysiological mapping.[1, 2, 4, 6, 12] The use of temperature-guided radiofrequency energy delivery (50–70°C, 30–50 watts, 30–60 seconds per lesion) minimized the risk of collateral damage and procedural complications.

The ethnic composition of the AVRT cohort reveals important variations compared to 2011 Sikkim census data (Table 2).[9, 10] The Bhutia community showed 2.7-fold enrichment (23.3% vs. 8.57%), Scheduled Castes 3.8-fold enrichment (7.7% vs. 2%), and Rai 1.6-fold enrichment (22.0% vs. 13.4%). Conversely, Chettri/Bahun (5.1% vs. 19.2%, 0.2× representation) and Tamang (5.1% vs. 6.8%, 0.7× representation) were under-represented in the AVRT cohort. These variations likely reflect differences in hospital catchment patterns, differential access to tertiary care services, community-specific treatment-seeking behaviors, or possibly true epidemiological differences in AVRT prevalence across ethnic groups. Such data are clinically important for understanding equitable access to advanced cardiac services, identifying potential barriers to care in specific communities, and designing targeted public health interventions in diverse hill populations.

A key strength of this series is the high proportion of manifested accessory pathways (70.1%) with clear pre-excitation on resting ECG, which simplifies diagnosis but also indicates a relatively younger and symptomatic patient population seeking curative treatment. The younger median age of AVRT patients compared to AVNRT-predominant series reflects the natural history of accessory pathway disease, which typically manifests clinically in adolescence and young adulthood.[3, 5, 8] Left free wall accessory pathways, which account for approximately 53% of all AP locations, generally have higher success rates and lower recurrence compared to posteroseptal and right-sided pathways; future stratification by AP location in our cohort would further contextualize our excellent outcomes.[7]

4.1 Limitations

Limitations include the descriptive nature of this analysis, lack of a comparison arm, and absence of systematic quantitation of procedure duration, fluoroscopy time, and minor complication rates. Longer-term follow-up beyond 1 year would strengthen conclusions about late recurrence and the durability of accessory pathway ablation in this population. Additionally, the high baseline symptom burden and selection of symptomatic patients may limit generalizability to asymptomatic individuals with pre-excitation. The variation in ethnic distribution compared to census data warrants further investigation to determine whether this reflects true epidemiological differences or healthcare access disparities. Despite these limitations, the series demonstrates that accessory pathway ablation in a hill state tertiary center can achieve outcomes fully comparable to major international electrophysiology programs.

Accessory pathway-mediated atrioventricular re-entrant tachycardia represents 41.6% of PSVT cases in the Himalayan hill population of Sikkim. The AVRT cohort demonstrates a balanced age distribution and equal sex representation, with a predominance of manifested accessory pathways (70.1%) amenable to diagnosis via resting ECG. Ethnic analysis reveals notable enrichment for Bhutia and Rai communities as well as Scheduled Castes compared to census data, suggesting differential access or epidemiological patterns requiring further investigation. Two-dimensional electrophysiological study combined with radiofrequency ablation demonstrates exceptional and durable efficacy, with acute success rates of 98.7%, short-term recurrence rates of only 1.3%, and a zero major complication rate. These outstanding outcomes validate the clinical value and safety of advanced electrophysiology services in resource-limited hill regions and support expansion of such programs to improve equitable access to definitive AVRT therapy across all ethnic communities in remote areas. Future prospective studies with longer follow-up, systematic complication tracking, and detailed ethnic and geographic analysis are warranted to establish best practices for AP ablation in Himalayan and tribal populations.

1.       Katritsis DG, Boriani G, Cosio FG, Hindricks G, Jais P, Josephson ME, et al. European Heart Rhythm Association (EHRA) consensus document on the management of supraventricular arrhythmias, endorsed by Heart Rhythm Society (HRS), Asia-Pacific Heart Rhythm Society (APHRS), and Sociedad Latinoamericana de Estimulación Cardiaca y Electrofisiologia (SOLAECE). Eur Heart J. 2018;39(16):1442-5.

2.       Scheinman MM, Huang S. The 1998 NASPE prospective catheter ablation registry. Pacing Clin Electrophysiol. 2000;23(6):1020-8.

3.       Chhabra L, Goyal A, Benham MD. Wolff-Parkinson-White Syndrome.  StatPearls. Treasure Island (FL): StatPearls Publishing

4.       Copyright © 2023, StatPearls Publishing LLC.; 2023.

5.       Backhoff D, Klehs S, Müller MJ, Schneider HE, Kriebel T, Paul T, et al. Long-Term Follow-Up After Catheter Ablation of Atrioventricular Nodal Reentrant Tachycardia in Children. Circulation: Arrhythmia and Electrophysiology. 2016;9(11):e004264.

6.       Hedayati Goudarzi MT, Akbarian M, Bhia I, Saravi M, Soltaninejad H. Radiofrequency Catheter Ablation in Patients with Supraventricular Tachycardia: A Cohort Study on Efficacy, Safety, Anxiety, and Quality of Life Outcomes. Iran J Med Sci. 2025;50(10):672-80.

7.       Ibrahim Ali Sherdia AF, Abdelaal SA, Hasan MT, Elsayed E, Mare'y M, Nawar AA, et al. The success rate of radiofrequency catheter ablation in Wolff-Parkinson-White-Syndrome patients: A systematic review and meta-analysis. Indian Heart J. 2023;75(2):98-107.

8.       Chen YJ, Chen SA, Tai CT, Chiang CE, Lee SH, Chiou CW, et al. Long-term results of radiofrequency catheter ablation in patients with Wolff-Parkinson-White syndrome. Zhonghua Yi Xue Za Zhi (Taipei). 1997;59(2):78-87.

9.       Rehorn M, Sacks NC, Emden MR, Healey B, Preib MT, Cyr PL, et al. Prevalence and incidence of patients with paroxysmal supraventricular tachycardia in the United States. J Cardiovasc Electrophysiol. 2021;32(8):2199-206.

10.    Office of the Registrar General & Census Commissioner I, Ministry of Home Affairs, Government of India. C-01: Population by religious community, Sikkim - 2011. In: Ministry of Home Affairs GoI, editor. 2021.

11.    Office of the Registrar General & Census Commissioner I, Ministry of Home Affairs, Government of India. ST-14 A: Scheduled tribe population by religious community (State/UT level), Sikkim - 2011. 2021.

12.    Wan Q, Wu N, Fan W, Tang YY, Jin L, Fang Q. Clinical manifestations and prevalence of different types of supraventricular tachycardia among Chinese. Chin Med J (Engl). 1992;105(4):284-8.

13.    Kobza R, Kottkamp H, Piorkowski C, Tanner H, Schirdewahn P, Dorszewski A, et al. Radiofrequency ablation of accessory pathways. Contemporary success rates and complications in 323 patients. Z Kardiol. 2005;94(3):193-9.

14.    Dionne A, Gauvreau K, O'Leary E, Mah DY, Abrams DJ, Alexander ME, et al. Risk Factors for Early Recurrence Following Ablation for Accessory Pathways: The Role of Consolidation Lesions. Circ Arrhythm Electrophysiol. 2020;13(11):e008848.