Arrhythmogenic right ventricular cardiomyopathy with atrial tachycardia and sick sinus syndrome: A case report

Abstract

BACKGROUND

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited cardiomyopathy that may involve the right ventricle, left ventricle, or both. To the best of our knowledge, the combination of ARVC with sick sinus syndrome, para-Hisian focal atrial tachycardia (AT), and demonstrable atrial myocardial involvement has not been previously reported.

CASE SUMMARY

A 57-year-old male was hospitalized with palpitations and was diagnosed with definite ARVC in 2021. He presented initially with sustained ventricular tachycardia and declined implantable cardioverter-defibrillator implantation. Later he developed focal AT with 2:1 atrioventricular conduction and ischemic stroke. During hospitalization endocardial substrate ablation of extensive low-voltage and scarred areas along the right ventricle free wall was performed, followed by successful ablation of a para-Hisian focal AT. A post-ablation electrophysiological study revealed prolonged sinus node recovery time (1660 milliseconds), marked sinus bradycardia after AT termination, and extensive right atrial low-voltage and scarred areas involving the free wall, posterior wall, and sinus node area. Sick sinus syndrome and right atrial myocardial involvement were diagnosed. As of the most recent follow-up in 2025 he had suffered two ischemic strokes with no ventricular tachycardia.

CONCLUSION

A thorough assessment of atrial involvement is essential for ARVC patients.

Key Words: Electrophysiology; Arrhythmogenic right ventricular cardiomyopathy; Sick sinus syndrome; Atrial tachycardia; Case report

Core Tip: This case highlights a rare arrhythmogenic right ventricular cardiomyopathy (ARVC) with sick sinus syndrome, para-Hisian focal atrial tachycardia, and extensive right atrial myocardial scarring confirmed by electroanatomic mapping. Beyond ventricular involvement, the patient demonstrated profound atrial electrical and structural remodeling, sinus node dysfunction and ischemic strokes despite successful ventricular tachycardia control. Therefore, atrial myocardial involvement in ARVC may have important clinical implications and systematic evaluation for arrhythmic and thromboembolic risk is valuable.

INTRODUCTION

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a hereditary cardiomyopathy that mostly affects the right ventricle (RV), left ventricle (LV), or both. We report a rare case of ARVC involving both the right atrium (RA) and RV. The patient not only presented with ventricular tachycardia (VT) originating from the RV, but also with sick sinus syndrome (SSS) and focal atrial tachycardia (AT) adjacent to the His bundle. We performed radiofrequency ablation to modify the low-voltage and late-potential areas within the RV, followed by comprehensive RA mapping and focal AT trigger mapping and ablation, which demonstrated clear evidence of atrial myocardial involvement. Notably, the distribution of arrhythmogenic substrate was confined to the right heart, closely overlapping with areas corresponding to the second heart field during cardiac development. To the best of our knowledge, this uncommon pathological pattern has not been previously reported.

CASE PRESENTATION

Chief complaints

A 57-year-old male patient had recurrent palpitations for more than 30 years, with worsening for one day.

History of present illness

The patient presented to our hospital with palpitations. The emergency electrocardiography (ECG) showed sustained VT with left bundle branch block morphology and inferior axis, consistent with RV origin (Figure 1A). He began experiencing recurrent palpitations 30 years ago. He denied chest pain, chest tightness, dizziness, syncope, or radiating pain to the shoulder or left arm.

Figure 1 Electrocardiography of the patient. A: Emergency electrocardiography (ECG) at presentation showing sustained ventricular tachycardia (VT), heart rate 228 bpm; B: Emergency ECG in 2021 showing sustained VT, heart rate 192 bpm; C: Following electrical cardioversion ECG in 2021 showing Epsilon waves in leads II, III (blue arrows), aVR, aVF, inverted T waves in leads V1, V2, V3; D: Admission ECG during hospitalization for ischemic stroke in 2023 showing atrial tachycardia with 2:1 atrioventricular conduction.

History of past illness

He once experienced sudden fatigue followed by loss of consciousness while working, but received no treatment at the time. In 2021, he was taken to the emergency department due to VT and sinus rhythm was restored after electrical cardioversion (Figure 1B and C). He was diagnosed with definite ARVC after undergoing Holter (Figure 2), echocardiography (Figure 3A), cardiac magnetic resonance (Figure 3B), and genetic testing. In 2023, he was hospitalized with ischemic stroke and ECG showed AT with 2:1 atrioventricular conduction (Figure 1D). He had no history of hypertension, diabetes mellitus, coronary artery disease, or other chronic medical conditions.

Figure 2 Holter monitoring of the patient. Twenty-four-hour Holter showing atrial premature beats (208, single, paired), brief atrial tachycardia (1 episode), ventricular premature beats (120, single, multifocal, paired once).

Figure 3 Results of echocardiography and cardiac magnetic resonance. A: Contrast echocardiography showing no significant abnormalities in left ventricular wall motion, right ventricle (RV) wall motion abnormalities, RV fractional area change measured at approximately 30%, RV aneurysm (blue arrows); B: Cardiac magnetic resonance showing fatty infiltration of the RV free wall and the RA (blue arrows).

Personal and family history

The patient had no history of smoking or alcohol abuse. His father and elder brother had both died suddenly from unexplained causes.

Physical examination

Physical examination revealed no remarkable abnormalities. Following admission, the patient had reverted to sinus rhythm with a regular heart rate and rhythm. Cardiac auscultation showed no murmurs and no edema in the lower extremities.

Laboratory examinations

Laboratory tests showed the following: Cardiac troponin T (1478.0 ng/L), cardiac troponin I (10.29 ng/mL), and C-reactive protein (13.1 mg/L). Coagulation parameters, brain natriuretic peptide levels, potassium and thyroid function test results showed no discernible abnormalities.

Imaging examinations

Echocardiography revealed cardiac chamber enlargement, mild mitral regurgitation, moderate-to-severe tricuspid regurgitation, reduced right ventricular systolic function, and a left ventricular ejection fraction of 58%. RV angiography revealed a ventricular aneurysm near the tricuspid annulus on the free wall of the RV (Video).

FINAL DIAGNOSIS

Arrhythmogenic right ventricular cardiomyopathy, SSS, and para-Hisian focal atrial tachycardia.

TREATMENT

We adopted the method described by Wu et al[1] to induce VT through fast-rate (≥ 250 beats/minute) right ventricular burst stimulation. However, the patient could not tolerate the process, and induction was terminated. Endocardial substrate mapping during sinus rhythm showed extensive scarring and low-voltage areas on the RV free wall (ventricular scar was defined as bipolar electrogram amplitude between 0.5 mV and 1.5 mV during sinus rhythm and dense scar was defined as < 0.5 mV)[2]. Low-frequency, fractionated late potentials were observed along the right ventricular free wall, extending from the tricuspid annulus at the 10 o’clock position down to the low 6 o’clock position (Figure 4A). Concurrently, C-type isolation ring ablation was performed in the low-voltage areas, and homogenization modification was conducted targeting the areas with low-frequency, fractionated late potentials within the isolation rings (Figure 4B).

Figure 4 Electroanatomic mapping and ablation. A: Low-frequency, fractionated late potentials; B: Homogenization modification; C: Para-Hisian focal atrial tachycardia ablation; D and E: Extensive low-voltage and scarred areas on the right atrial free wall, posterior wall, and the sinus-node region, corresponding to the signal of cardiac magnetic resonance in Figure 3B.

After confirming bidirectional block and adequate substrate modification, sustained AT was induced during the withdrawal of the mapping catheter. Activation mapping localized the earliest atrial activation site to the para-Hisian region focal AT below the interatrial septum. Mechanical friction around the target site could repeatedly terminate and re-induce AT, long RR pauses and marked sinus bradycardia were observed after AT termination. Electrophysiological study (EPS) showed a sinus node recovery time of 1660 milliseconds. Detailed mapping around the target site identified the earliest atrial activation occurring 37 milliseconds earlier than the surface ECG. Local ablation was performed in sinus rhythm with temperature control of 20 W and a flow rate of 2 mL/minute (500 U/500 mL heparinized saline), and resulted in atrioventricular (AV) prolongation from 120 milliseconds to 220 milliseconds within 20 seconds. As peripheral consolidation ablation was prone to AV prolongation, ablation was terminated (Figure 4C).

Repeated atrial programmed stimulation and burst stimulation, as well as ventricular programmed stimulation, failed to induce the clinical AT or VT. Substrate mapping of the RA revealed extensive low-voltage and scarred areas on the right atrial free wall, posterior wall, and the sinus-node region (atrial dense scar was defined as bipolar electrogram voltage < 0.5 mV during sinus rhythm, and the low-voltage area was defined as abnormal myocardial tissue with voltages < 0.5 mV)[3] (Figure 4D and E). These findings were consistent with the abnormal signal regions seen on pre-procedural cardiac magnetic resonance (CMR) imaging. The post-ablation diagnosis was para-Hisian focal AT and SSS.

OUTCOME AND FOLLOW-UP

An implantable cardioverter defibrillator (ICD) was recommended per European Society of Cardiology (ESC) guidelines (class I indication)[4], but the patient declined and was discharged on oral aspirin therapy. At the time of writing, no recurrent atrial or ventricular arrhythmias have since been recorded. However, the patient experienced a second ischemic stroke. At the most recent follow-up, the patient remained at persistent risk due to refusal of ICD implantation and recurrent thromboembolic events, his long-term prognosis remains guarded. A disease timeline is presented in Table 1.

Table 1 Disease timeline of the patient.

Time	Clinical events	Results
November 2021	Admitted for palpitations. ARVC was diagnosed after complete examination	Requested conservative treatment, discharged
October 2023	Admitted for ischemic stroke. ECG showed AT with 2:1 AV conduction	Symptoms improved, discharged
April 2024	Admitted for palpitations. ECG showed VT and underwent radiofrequency ablation	Declined ICD implantation, discharged
August 2025	Admitted for a second ischemic stroke with no VT	Symptoms improved, discharged

AT: Atrial tachycardia; AV: Atrioventricular; VT: Ventricular tachycardia; ARVC: Arrhythmogenic right ventricular cardiomyopathy; ECG: Electrocardiography; ICD: Implantable cardioverter defibrillator.

DISCUSSION

ARVC is an inherited cardiomyopathy caused by mutations in desmosomal protein genes. It is a major cause of sudden cardiac death in young adults and athletes. The clinical presentation of ARVC varies widely, and its arrhythmic manifestations are often complex, which can pose considerable diagnostic challenges[5,6]. The diagnostic criteria for ARVC have progressed from the original 1994 task force criteria to the revised 2010 Task Force Criteria, and most recently, to the 2020 Padua Criteria. The condition involves morpho-functional ventricular abnormalities, structural myocardial abnormalities, repolarization and depolarization abnormalities, ventricular arrhythmias, and family genetics[7]. Electrocardiographic repolarization abnormalities, particularly T-wave inversion in the right precordial leads (V1-V3), are among the earliest and most common findings in ARVC. The extent of T-wave inversion usually correlates with the degree of fibrofatty replacement in the RV[8]. The epsilon wave is a low-amplitude deflection that occurs immediately after the end of the QRS complex and before the onset of the T wave, it reflects delayed RV activation due to fibrofatty replacement of the RV free wall myocardium. Although its diagnostic sensitivity and specificity are debated, it remains an important clue suggestive of ARVC[4,8]. Echocardiography and CMR are essential for evaluating structural involvement, with CMR providing high sensitivity for detecting fibrofatty infiltration[4,9]. Genetic testing contributes to early diagnosis, particularly in asymptomatic carriers. Early identification and timely intervention could reduce the risk of sudden cardiac death. This reveals that ARVC is a multifaceted disease, and effective management relies on a comprehensive assessment.

During cardiac development, major components of the RV and portions of the RA arise primarily from the second heart field (SHF). Pathogenic PKP2 variants have been shown to suppress Wnt signaling in epicardial SHF-derived progenitor cells, promoting adipogenic differentiation. These adipocytes gradually replace cardiomyocytes, beginning in the subepicardial RV free wall and extending toward the endocardium. This developmental-anatomical framework may explain why PKP2-related ARVC typically exhibits early pathological involvement confined to the RV[10,11]. Previous studies have demonstrated that combined endocardial and epicardial substrate ablation can improve clinical outcomes by reducing recurrent VT and mortality. However, epicardial ablation carries a higher risk of procedural complications. Particularly in late-stage ARVC, the right ventricular wall is frequently thinned due to progressive fibrofatty replacement. Compared with epicardial ablation, endocardial ablation has a lower incidence of major complications, including pericardial tamponade and ventricle perforation[12]. Recent evidence indicates that a just endocardial ablation strategy offers effective long-term arrhythmia control in many patients. However, the efficacy of endocardial ablation is constrained by the limited penetration depth of radiofrequency energy. Critical conduction channels situated within the epicardial or intramural layers may remain intact, leading to incomplete substrate modification and a heightened risk of VT recurrence. If endocardial ablation failed, epicardial ablation can be performed again. In clinical practice, most patients undergo just endocardial ablation and achieve effective VT suppression, resulting in prolonged survival with no VT[2,12]. Consistent with observations from Wu et al[2], substrate isolation is a safe and feasible strategy for ARVC patients with extensive abnormal substrate, offering favorable outcomes while avoiding the greater invasiveness of epicardial access. In our case, endocardial mapping showed large-area scars and low-voltage areas along the RV free wall. We performed ablation targeting low-frequency, fractionated late potentials from the tricuspid annulus at the 10 o’clock position down to the low 6 o’clock position, and C-type isolation ring ablation was performed in the low-voltage areas. No VT recurrence was observed during follow-up.

Traditionally, ARVC has been regarded as a condition affecting the RV, LV, or both. In its early stages, ARVC typically affects the “triangle of dysplasia” (the right ventricular inflow tract, outflow tract, and apex), with occasional involvement of the inferolateral left ventricular wall[13]. Recent evidence has demonstrated that atrial involvement is not uncommon in ARVC. Fibrofatty replacement can extend from the ventricles into the atria, leading to structural and electrical remodeling of atrial myocardium. This remodeling predisposes patients to atrial arrhythmias [including atrial tachycardia, atrial fibrillation (AF), and flutter], which may further destabilize cardiac electrophysiology and increase the risk of thromboembolic events[14,15]. Autopsy studies of ARVC patients have demonstrated fat infiltration and fibrosis in RA myocardium, the pathological changes that may lead to atrial arrhythmias including AF[16]. Imaging and EPS may provide evidence of atrial disease[6]. Atrial enlargement may also increase the risk of bradyarrhythmias in ARVC, most commonly intraventricular conductional block while SSS is less frequent. Current data on conduction system abnormalities in ARVC remain limited, but the mechanism is thought to involve the extension of fibrofatty replacement into the cardiac conduction system[17]. In our case, both ARVC and clear evidence of atrial involvement were present, and EPS confirmed a para-Hisian atrial tachycardia and SSS. To the best of our knowledge, this rare pathological phenotype has not been previously reported. These findings show that the disease extended beyond the RV to involve the entire RA and the sinoatrial node region, consistent with the anatomical distribution of the SHF during cardiac development.

Clinical management of ARVC should focus on not only ventricular pathology but also atrial involvement. Atrial structural and electrical abnormalities can affect the rhythmic contraction of the atria, and may facilitate thrombus formation particularly within the left atrial appendage. According to the 2024 ESC guidelines for the management of AF, patients with cardiomyopathy and documented AF should receive anticoagulation based on the CHA₂DS₂-VASc score, while incorporating additional risk modifiers such as atrial enlargement or fibrosis, which may further increase thromboembolic risk[18]. In our patient, recurrent embolic events occurred despite the absence of sustained AF on monitoring. EPS confirmed clear evidence of atrial involvement. These findings show that early anticoagulation may be reasonable in ARVC patients with established atrial involvement, even when AF is not consistently documented. This highlights the importance of individualized thromboembolic risk assessment in ARVC, particularly in those with atrial remodeling or atrial arrhythmias.

CONCLUSION

Once ARVC is diagnosed, a thorough assessment of atrial involvement is essential. Echocardiography, CMR, and EPS are valuable methods for detecting atrial structural and electrical abnormalities. Early recognition of atrial involvement plays a critical role in comprehensive disease evaluation and in guiding optimal clinical management.