Ultra–High Density Mapping of Ventricular Tachycardia in a Patient With Arrhythmogenic Right Ventricular Cardiomyopathy

Abstract

Background

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited cardiomyopathy that often leads to ventricular dysfunction and recurrent ventricular tachycardia (VT). Catheter ablation is a beneficial treatment for ARVC-related VT, but extensive substrate ablation may increase the risk of iatrogenic hemodynamic decompensation.

Case Summary

We describe a 54-year-old female ARVC patient with paroxysmal palpitations and frequent implantable cardioverter-defibrillator discharges.

Discussion

This case demonstrates that ultra–high density mapping-guided precise ablation can effectively target the “culprit” substrate in ARVC patients with extensive ventricular scarring, achieving a favorable balance between long-term freedom from VT and preservation of residual cardiac function.

Take-Home Messages

Precise ablation balances efficacy and safety by ensuring long-term VT freedom and preserving residual cardiac function in ARVC patients. Comprehensive mapping techniques, including activation mapping, entrainment mapping, and isochronal late activation mapping, improve ablation accuracy.

Graphical Abstract

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited cardiomyopathy predominantly affecting the right ventricle and characterized by progressive fibrofatty replacement of the myocardium, resulting in ventricular dysfunction and high prevalence of ventricular tachycardia (VT).¹ Catheter ablation has been proven beneficial in ARVC patients,² but the need for repeated procedures is emphasized for more sustained freedom from VT recurrence.^2,3 From another perspective, progressive cardiac dysfunction resulting from extensive substrate ablation, which may increase the risk of iatrogenic hemodynamic decompensation, is recently garnering growing attention.⁴ Therefore, “pinpointing the culprit” precisely is essential for long-term success and maintenance of cardiac function. In recent studies, ultra–high density mapping has been widely applied to reveal clearer arrhythmogenic substrates and improve clinical outcomes. In this case report, we delineate a patient with ARVC treated with a precise ablation approach under the guidance of ultra–high density mapping.

Take-Home Messages

• •In patients with ARVC, precise ablation balances efficacy and safety by ensuring long-term freedom from VT and preservation of residual cardiac function.
• •Comprehensive mapping techniques (eg, activation mapping, entrainment mapping, isochronal late activation mapping) improve ablation accuracy.

History of presentation

A 54-year-old woman attended the emergency department owing to paroxysmal palpitations and frequent implantable cardioverter-defibrillator (ICD) discharges even when taking high doses of metoprolol and amiodarone in the past 5 months. A previous electrocardiogram (ECG) indicated ventricular tachycardia (VT) with a heart rate of 97 beats/ min (Figure 1A). She had undergone ICD implantation in our hospital 10 years prior and had since been on long-term antiarrhythmic drug therapy. However, her symptoms persisted, and she subsequently experienced multiple episodes of syncope. She was therefore admitted to our hospital for radiofrequency catheter ablation.

Figure 1.

ECG During VT and Sinus Rhythm

(A) ECG during VT demonstrated a left bundle branch block pattern, consistent with an origin in the upper right ventricle. (B) ECG during sinus rhythm showed epsilon waves (low-amplitude distinct signals between the QRS complex and T-wave in precordial leads V₁-V₃) and negative T waves in precordial leads V₁ to V₄, which were major diagnostic criteria for ARVC. ARVC = arrhythmogenic right ventricular cardiomyopathy; ECG = electrocardiogram; VT = ventricular tachycardia.

Differential diagnosis

ECG identified epsilon waves (low-amplitude distinct signals between the QRS complex and T wave in precordial leads V₁-V₃) and negative T wave in precordial leads V₁ to V₄ (Figure 1B), which are major criteria for the diagnosis of ARVC. Additionally, the ECG of the VT demonstrated a left bundle branch block pattern (Figure 1A), consistent with an origin in the upper right ventricle. Furthermore, significant right ventricular dilation (54 mm) and ventricular wall thinning were detected on transthoracic echocardiography, indicating predominantly right ventricular involvement. Although the patient did not undergo preoperative cardiac magnetic resonance imaging, the diagnosis of ARVC was still definitive in this case.

Investigation

Electrophysiology study and radiofrequency ablation were performed under deep sedation with propofol and dexmedetomidine. At the start of the procedure, sustained VT was present, with a cycle length of 440 ms; the patient remained awake with stable hemodynamics. An intracardiac echocardiography catheter (SoundStar, Biosense Webster) was introduced into the right atrium via the left femoral vein. A three-dimensional model of the right ventricle was constructed using a mapping system (CARTO 3, Biosense Webster). Ultra–high density activation mapping was performed during an episode of VT using a novel 8-spline high-resolution catheter (Octaray; Biosense Webster). Local activation time was annotated using the wavefront algorithm (steepest unipolar − dv/dt). With nearly 20,000 mapping points acquired, a counterclockwise re-entrant circuit was clearly revealed at the upper aspect of the right ventricular free wall (Figure 2, Video 1). Isochronal late activation mapping (ILAM) demonstrated significantly slow conduction at the upper anterior free wall, while bipolar mapping showed extensive distribution of low-voltage regions and severely lesioned myocardium (Figure 3). Subsequently, an 8.5-F saline-irrigated ablation catheter (ThermoCool SmartTouch; Biosense Webster) was advanced to the right ventricular free wall for pace mapping or entrainment. Characteristic entrainment responses⁵ were obtained at the “exit” and “mid-isthmus” of the re-entrant circuit, respectively (Figure 4).

Figure 2.

Ultra–High Density Activation Mapping and Potentials Along the Re-Entrant Circuit

(Left) ECG obtained upon laboratory entry. (Right) An ultra–high density activation map was acquired during VT. A counterclockwise re-entrant circuit was clearly identified at the upper aspect of the right ventricular free wall. Electrical potentials along the re-entrant circuit spanned the entire cycle length. ECG = electrocardiogram; PA = pulmonary artery; VT = ventricular tachycardia.

Figure 3.

Results of Isochronal Late Activation Mapping and Bipolar Voltage Mapping

(Upper Panels) ILAM demonstrated significantly slow conduction at the upper anterior aspect of the right ventricular free wall. (Lower Panels) Bipolar mapping showed extensive distribution of low-voltage regions and severely lesioned myocardium. AP = anteroposterior; ILAM = isochronal late activation mapping; LL = left lateral; RAO = right anterior oblique.

Figure 4.

Results of Entrainment Mapping

Concealed entrainment was observed at sites A and B, with characteristics consistent with the “exit” and “mid-isthmus” of the re-entrant circuit identified at these 2 sites, respectively. (A) PPI = 447 ms, S-QRS = 114 ms, EGM-QRS = 116 ms. (B) PPI = 474 ms, S-QRS = 162 ms, EGM-QRS = 162 ms. PPI = postpacing interval; S-QRS = stimulus-to-QRS interval; EGM-QRS = electrogram-to-QRS interval.

Management

VT was immediately terminated with the first application of radiofrequency ablation at the “exit.” Additional lesions were applied across the critical isthmus to of the re-entrant circuit to ensure complete block of the isthmus. Extensive homogenization of this low-voltage area was an optional strategy, but it may not be optimal for preserving residual myocardial function. To assess the further possibility of re-entrant VTs mediated by this area, another activation map during sinus rhythm was created to identify other potential critical isthmuses (Figure 5, Video 2). It could be interpreted from the mapping results that electrical propagation on the free wall “hit a dead end” with no other exit out of this region, confirming a precise and sufficient barrier to block the re-entrant circuit (Figure 5, Video 2).

Figure 5.

Postablation Activation Remapping During Sinus Rhythm

Postablation activation mapping during sinus rhythm demonstrated the conduction sequence and distribution of scar regions. The right ventricular free wall was divided into 3 distinct regions that were disconnected from each other, indicating a low likelihood of subsequent macro-re-entrant arrhythmias. Nevertheless, the last map illustrated a potential peritricuspid conduction (red arrows), which necessitated additional lesions connecting the tricuspid annulus to the inferior aspect of the scar (yellow dotted line). AP = anteroposterior; LAO = left anterior oblique; RAO = right anterior oblique; RL = right lateral.

Postablation activation mapping during sinus rhythm demonstrated the conduction sequence and distribution of scar areas. The free wall was segmented into 3 districts that were disconnected from each other, which predicted little possibility of further macro-re-entrant arrhythmias. Nevertheless, the last map illustrated a potential peritricuspid conduction, which necessitated additional lesions connecting the tricuspid annulus to the inferior aspect of the scar.

Outcome and follow-up

Ventricular burst pacing was performed immediately after ablation to assess inducibility but failed to induce any VTs, and the procedure was concluded. The patient's symptoms (paroxysmal palpitations, ICD discharges) completely resolved. During 10 months of follow-up, no VT recurrence was recorded by either ICD interrogations or 24-hour Holter monitoring.

Discussion

This report describes a rare case of an ARVC patient with extensive endocardial scarring, a finding that typically makes it challenging to “pinpoint the culprit” for VTs. However, the precise ablation strategy guided by ultra–high density mapping yielded encouraging and win-win outcomes: the patient achieved long-term freedom from VT and no deterioration of ventricular function.

It is well established that fibrofatty replacement of the myocardium in ARVC patients serves as the substrate for macro-re-entrant tachycardia, but its spatial distribution varies among patients at different stages of myocardial fibrosis.² This pathological substrate is typically characterized by low-amplitude potentials, slow conduction, fractionated potentials, late potentials, or local abnormal ventricular activities—all of which originate from local pathological myocardial tissues.⁶ Ultra–high density mapping using high-resolution multielectrode catheters offers distinct advantages in identifying these electrophysiological indicators and functional substrates of VT within definite regions.⁷ Recently, several techniques leveraging ultra–high density mapping have been validated as feasible and effective, including ILAM, decrement-evoked potential (DeEP) mapping, and wavefront discontinuity lines (WADLs) mapping.

For inducible monomorphic VTs, identifying functional substrates is relatively straightforward, as the entire conduction sequence can be captured in either the endocardium or the epicardium. Furthermore, entrainment maneuvers performed after activation mapping serve as a complementary method to validate the functional substrate.⁸ However, for noninducible VTs or those associated with hemodynamic intolerance, the accuracy of functional substrate identification decreases, and detecting all occult targets becomes far more challenging during sinus rhythm or ventricular pacing. In the present case, given that the patient had sustained VT and stable hemodynamics, we employed a comprehensive mapping technique combining activation mapping, entrainment mapping, and ILAM analysis for cross-validation. As anticipated, the critical isthmus identified via activation mapping was highly consistent with the results of entrainment mapping.

After careful interpretation of the mapping data, we did not perform homogenization of the entire isthmus region, as complete conduction block was achieved across one end of the isthmus (Figure 5, Video 2). This finding indicated a very low likelihood of future re-entrant VT recurrence mediated by this region. Although most studies suggest that extensive substrate ablation is associated with higher freedom from recurrence in scar-related VT, this approach has remained controversial in recent years. Like a double-edged sword, aggressive ablation may increase the procedural risk of hemodynamic decompensation in patients with pre-existing impaired cardiac reserve.⁹ Thus, a precise ablation strategy—optimized by advanced mapping techniques—has been proposed, but limited evidence supports its long-term efficacy.

The current case specifically highlights the role of precise ablation in ARVC patients with extensive ventricular scarring and pre-existing ventricular dysfunction. A major challenge in managing these patients is detecting all occult targets during sinus rhythm. A recent study demonstrated that extrastimulus pacing from the right ventricular apex has the highest sensitivity (up to 95%) for identifying critical isthmuses, compared with sinus rhythm or standard right ventricular apical pacing.¹⁰ In our clinical practice, however, we prefer right ventricular apical pacing for mapping, as it is less time-consuming and maintains relatively high sensitivity (85%, as reported).¹⁰ Unfortunately, in this case, we were unable to stably capture the endocardium—even with maximum stimulus voltage and from multiple right ventricular sites—likely because of extensive endocardial scarring. We therefore opted to perform mapping during sinus rhythm as an alternative. Although assessing only a single physiological state (ie, sinus rhythm) is insufficient to detect all occult targets—given the anisotropic conduction of diseased myocardium—the favorable postoperative outcome (10 months of VT freedom and resolved symptoms) confirmed the accuracy and adequacy of our ablation strategy.

Conclusions

This case demonstrates the successful application of a precise ablation strategy—guided by ultra–high density mapping—to target the “culprit” substrate in a patient with ARVC-associated VT. Notably, for patients with extensive ventricular scarring and pre-existing ventricular dysfunction, this strategy holds clinical significance in achieving a favorable balance between optimizing clinical outcomes (ie, VT freedom) and preserving residual cardiac function.

Funding Support and Author Disclosures

The authors have reported that they have no relationships relevant to the contents of this paper to disclose.

Appendix

Video 1

Propagation of the Counterclockwise Reentrant Circuit on the Upper Free Wall.

Video 2

Activation Map After Ablation During Sinus Rhythm Showed the Free Wall was Segmented Into Three Disconnected Districts, Indicating A Low Likelihood of Recurrent Macroreentrant Arrhythmias.