A Case of Epicardial Ablation of the Sinus Node for the Treatment of Inappropriate Sinus Tachycardia

DOI: 10.19102/icrm.2025.16093

MAHMOUD ELDESOUKY, MRCP,¹ NOHA ELBANHAWY, MRCP,¹ SHAJIL CHALIL, FRCP,¹ and KHALID ABOZGUIA, PhD,^1,2

¹Cardiology Department, Blackpool Teaching Hospital NHS Trust, Blackpool, UK

²Cardiology Department, Marshall University, Joan C. Edwards School of Medicine, Huntington, WV, USA

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ABSTRACT. Despite advancements in medical therapy, managing symptomatic inappropriate sinus tachycardia (IST) remains challenging. The role of catheter ablation in addressing this condition remains ambiguous according to multiple cardiac society guidelines. In this case study, we illustrate the efficacy of a hybrid approach involving sinus node modification and ablation in a patient with refractory symptoms, while also addressing the associated challenges and safety considerations of this procedure. A 58-year-old female patient was troubled with recurrent palpitations secondary to IST. Due to the proximity of the target ablation site to the phrenic nerve, this area was not amenable to complete ablation endocardially. To alleviate symptoms, an ablation procedure was planned, aiming for epicardial sinus node modification and displacement of the phrenic nerve from the target site. The procedure was completed under general anesthesia. The conventional subxiphoid technique was deemed challenging even with a surgical approach due to the patient’s body habitus and significantly increased body mass index; hence, she underwent a 5-cm right anterior thoracotomy to establish access to the pericardium. The sinoatrial (SA) node was ablated surgically by direct application under vision of the right atrium around the area of the SA node to avoid the phrenic nerve. Modification and ablation of the sinus node in patients exhibiting features of IST may be considered to help alleviate patients’ symptoms. Further follow-up and assessments with large cohorts and powered randomized controlled studies are needed. Our case represents an example where a hybrid invasive approach resulted in a safe procedure with immediate symptomatic benefit.

KEYWORDS. Case report, hybrid ablation, inappropriate sinus tachycardia, surgical window.

Dr. Eldesouky’s current post at the University of Leicester is partially funded by Boston Scientific. The remaining authors report no conflicts of interest for the published content. No funding information was provided. Drs. Eldesouky and Elbanhawy contributed equally to the paper. ORCID ID: M.E., 0009-0000-0317-1428.
Manuscript received March 28, 2025. Final version accepted June 10, 2025.
Address correspondence to: Mahmoud Eldesouky, 88 Clare Hill, Huddersfield, HD1 5BP, UK. Email: mahmoud.eldesouky2@nhs.net.

Introduction

Despite medical therapy advancements, managing symptomatic inappropriate sinus tachycardia (IST) remains challenging. The role of catheter ablation remains ambiguous according to multiple guidelines.^1,2 We illustrate the efficacy of a hybrid approach to sinus node modification, addressing the procedure’s challenges and safety considerations.

Case presentation

A 58-year-old female patient was troubled by recurrent palpitations secondary to IST despite multiple rate-control medications at maximum tolerated doses (10 mg of bisoprolol twice a day, 125 μg of digoxin once a day, and 7.5 mg of ivabradine twice a day). The patient had ischemic cardiomyopathy, and a biventricular (BiV) implantable cardioverter-defibrillator was implanted for primary prevention given the persistent severe left ventricular systolic dysfunction and left bundle branch block despite guideline-directed medical therapy. Her past medical history revealed hypothyroidism, type 2 diabetes mellitus, mixed hyperlipidemia, essential hypertension, and a high body mass index (>40 kg/m²).

The patient underwent an extensive evaluation and was discussed in multiple multidisciplinary team meetings. All potential triggers, including obstructive sleep apnea, anemia, and ischemia, were excluded. Management of her comorbidities was optimized medically.

She remained symptomatic with palpitations and New York Heart Association (NYHA) class III. The BiV pacing percentage was significantly low due to a high sinus rate. The BiV device was programmed to the VVI mode as the patient had a high percentage of tracked elevated sinus tachycardia, which was poorly tolerated. This was to help avoid tracking the sinus tachycardia by pacing only the ventricles, reducing unnecessary pacing-induced tachycardia episodes.³ The adjustment was necessary to prevent rapid atrial tracking resulting in hemodynamic instability and increased myocardial oxygen demand.^4,5 The patient was thus listed for an electrophysiology (EP) study and sinus node modification with a view toward lowering the sinus rate, aiming to improve the BiV pacing percentage. Three-dimensional (3D) mapping confirmed the diagnosis of IST. The EP study ruled out an accessory pathway with evidence of dual atrioventricular (AV) node physiology and single echo.

The 3D activation mapping showed the earliest atrial signal in an area close to the sinus node. An endocardial ablation attempt was made. Due to the proximity of the target ablation site to the phrenic nerve, this area was not amenable to complete ablation endocardially. Device interrogations continued to show persistent sinus tachycardia (Figure 1). The patient was highly symptomatic, and BiV pacing was inhibited because of high intrinsic rates.

To alleviate symptoms, an ablation procedure was planned, aiming for epicardial sinus node modification and displacement of the phrenic nerve from the target site. This option was more invasive, but we predicted difficulty in obtaining percutaneous pericardial access with the standard subxiphoid technique given the patient’s body habitus, and thus we arranged for the cardiothoracic surgical team to assist with a surgical window.

The procedure was performed under general anesthesia in a hybrid EP lab equipped with 3D mapping capability and a surgical facility. Baseline electrocardiogram showed sinus tachycardia (Figure 2). Ultrasound guidance was used for right femoral vein access. 3D voltage and activation maps (Figure 3) were created using the CARTO^® 3 mapping system (Biosense Webster, Inc., Diamond Bar, CA, USA) and a high-density mapping catheter (PentaRay^® NAV Catheter; Biosense Webster). Isoprenaline was used during mapping to identify the sites of fastest sinus activity. The earliest signal was confirmed to be in the sinus node region in an area with phrenic nerve capture, which previously precluded endocardial ablation (Figure 3). The patient underwent a 5-cm right anterior thoracotomy, establishing access to the pericardium.

The SA node was ablated surgically using the cryoICE cryotherapy probe (AtriCure Inc., Mason, OH, USA) by direct application under vision of the right atrium around the area of the SA node to avoid the phrenic nerve. Multiple single-application freezes with temperatures ranging between −50°C and −70°C were achieved to guarantee irreversible tissue damage. A number of lesions were performed epicardially. Further lesions were created as directed by the EP team to achieve electrical modification and ablation of the sinus node.

At this point in the procedure, the heart rate went down from 100 to 60 bpm and the rhythm changed to a junctional rhythm (Figures 4A and 4B). Slow pathway modification was also performed during sinus rhythm in view of dual AV node physiology and echoes. Remapping of the right atrium confirmed the area of earliest activation to be in the His region (Figure 5A). The incision was closed surgically. The device was then programmed to DDD pacing at 80 bpm with consistent BiV pacing, with plans to gradually reduce the heart rate in stages as an outpatient. This is given that gradual rate reduction allows the autonomic nervous system and cardiac conduction pathways to adjust more smoothly, thereby reducing the risk of destabilizing arrhythmic events.⁶ On follow-up, device interrogation showed a predominantly paced atrial and BiV rhythm at the programmed base rate with a physiologic increase in rates that were sensor-driven (Figure 5B). After the procedure, the patient exhibited a dramatic improvement in her symptoms of palpitations with an optimal percentage of BiV pacing. A perceived improvement in heart failure symptoms to NYHA class II was also observed.

Consent for publication was obtained, in line with the Committee on Publication Ethics best practice guidelines, and the individual who is being reported on is aware of the possible consequences of that reporting.

Discussion

The patient in this case met the criteria for the diagnosis of IST as defined in the guidelines and consensus statements.^7–9 Her average heart rate exceeded 90 bpm as seen in the ventricular rate histogram prior to ablation, and she had distressing symptoms. With continuous monitoring, her heart rates showed fluctuation and included normal and increased resting rates at times but excessive rates with exercise; intermittent rapid unexplained rates occurred with or without positional changes.

The mechanisms of IST are either related to the dysregulation of autonomic inputs to the sinus node or intrinsic sinus node disease. Different theories exist, including the presence of a β-receptor–stimulating autoantibody, a β-receptor super-sensitivity, a muscarinic (M2) receptor abnormality, impaired baroreflex control, a blunted response to adenosine with or without autonomic blockade, a reduction in and/or alteration of baroreflex gain, and abnormalities in parasympathetic function despite the preservation of sympathovagal balance and vagal denervation.^7,10

There is still debate regarding the clinical impact of high resting heart rates. In the Tromsø study, elevated resting heart rates were associated with an increased risk of myocardial infarction and mortality.¹¹

A meta-analysis from the Asia Pacific Cohort Studies Collaboration concluded that a resting heart rate of >65 bpm had a strong independent effect on premature mortality and stroke.¹²

The patient’s debilitating symptoms despite optimal medical management prompted the more-invasive approach. Options considered were AV node ablation or modification/ablation of the sinus node. Because AV node ablation was less physiologic and unlikely to control the tachycardia, as the device would most likely exhibit upper tracking rate behavior, ablation strategies targeting the sinus node were more favored.

Surgical and catheter ablation of the sinus node are not currently recommended but may be considered in the most symptomatic patients after the failure of other therapies.^1,13

In our case, the limitation of endocardial ablation due to potential damage to the phrenic nerve led us to consider a surgical hybrid approach. While more invasive, this method eliminates that risk by allowing direct visualization and avoidance of the phrenic nerve during ablation. Percutaneous epicardial access with phrenic nerve displacement using a balloon was also considered,¹⁴ but it was deemed technically challenging due to body habitus.

Pulsed field ablation (PFA) is an emerging ablation modality that is rapidly growing in popularity. One of the main advantages of PFA is its preferential tissue ablation characteristics, which allow for avoiding phrenic nerve injury.¹⁵ There is still a need for appropriate caution, however, as there are still only limited data available in the literature quantifying the effects of PFA on phrenic nerve stunning and their long-term impact.¹⁶

Our case represents an example where a hybrid invasive approach resulted in a safe procedure with immediate symptomatic benefit. Modification and ablation of the sinus node in patients exhibiting features of IST may be considered to help alleviate symptoms. Further assessment with large cohorts and powered randomized controlled studies is needed.

References

1. Page RL, Joglar JA, Caldwell MA, et al. 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. Circulation. 2016;133(14):e506–e574. [CrossRef] [PubMed]
2. Ahmed A, Pothineni NVK, Charate R, et al. Inappropriate sinus tachycardia: etiology, pathophysiology, and management: JACC review topic of the week. J Am Coll Cardiol. 2022;79(24):2450–2462. [CrossRef] [PubMed]
3. Doppalapudi H. Timing cycles of implantable devices. In: Ellenbogen KA, Wilkoff BL, Kay GN, Lau CP, Auricchio A, eds. Clinical Cardiac Pacing, Defibrillation and Resynchronization Therapy. Philadelphia, PA: Elsevier; 2017:961–1030. [CrossRef]
4. Hayes DL, Levine PA. Pacemaker timing cycles. In: Ellenbogen KA, Wood MA, eds. Cardiac Pacing and ICDs. 4^th ed. Hoboken, NJ: Wiley; 2005:265–321. [CrossRef]
5. Almehairi M, Baranchuk A, Johri A, Caldwell J. An unusual cause of automatic mode switching in the absence of an atrial tachyarrhythmia. Pacing Clin Electrophis. 2014;37(6):777–780. [CrossRef]
6. Wang RX, Lee HC, Hodge DO, et al. Effect of pacing method on risk of sudden death after atrioventricular node ablation and pacemaker implantation in patients with atrial fibrillation. Heart Rhythm. 2013;10(5):696–701. [CrossRef] [PubMed]
7. Olshansky B, Sullivan RM. Inappropriate sinus tachycardia. Europace. 2019;21(2):194–207. [CrossRef] [PubMed]
8. Ruzieh M, Moustafa A, Sabbagh E, Karim MM, Karim S. Challenges in treatment of inappropriate sinus tachycardia. Curr Cardiol Rev. 2018;14(1):42–44. [CrossRef] [PubMed]
9. Sheldon RS, Grubb BP, Olshansky B, et al. 2015 Heart Rhythm Society expert consensus statement on the diagnosis and treatment of postural tachycardia syndrome, inappropriate sinus tachycardia, and vasovagal syncope. Heart Rhythm. 2015;12(6):e41–e63. [CrossRef] [PubMed]
10. Boyett MR, Honjo H, Kodama I. The sinoatrial node, a heterogeneous pacemaker structure. Cardiovasc Res. 2000;47(4):658–687. [CrossRef] [PubMed]
11. Sharashova E, Wilsgaard T, Løchen ML, Mathiesen EB, Njølstad I, Brenn T. Resting heart rate trajectories and myocardial infarction, atrial fibrillation, ischaemic stroke and death in the general population: the Tromsø Study. Eur J Prev Cardiol. 2017;24(7):748–759. [CrossRef] [PubMed]
12. Woodward M, Webster R, Murakami Y, et al. The association between resting heart rate, cardiovascular disease and mortality: evidence from 112,680 men and women in 12 cohorts. Eur J Prev Cardiol. 2014;21(6):719–726. [CrossRef] [PubMed]
13. Marrouche NF, Beheiry S, Tomassoni G, et al. Three-dimensional nonfluoroscopic mapping and ablation of inappropriate sinus tachycardia. Procedural strategies and long-term outcome. J Am Coll Cardiol. 2002;39(6):1046–1054. [CrossRef] [PubMed]
14. Kumar S, Barbhaiya CR, Baldinger SH, et al. Epicardial phrenic nerve displacement during catheter ablation of atrial and ventricular arrhythmias: procedural experience and outcomes. Circ Arrhythm Electrophysiol. 2015;8(4):896–904. [CrossRef] [PubMed]
15. Ekanem E, Reddy VY, Schmidt B, et al. Multi-national survey on the methods, efficacy, and safety on the post-approval clinical use of pulsed field ablation (MANIFEST-PF). Europace. 2022;24(8):1256–1266. [CrossRef] [PubMed]
16. Howard B, Haines DE, Verma A, et al. Characterization of phrenic nerve response to pulsed field ablation. Circ Arrhythm Electrophysiol. 2022;15(6):e010127. [CrossRef] [PubMed]