Elsevier

Heart Rhythm

Volume 19, Issue 9, September 2022, Pages 1475-1483
Heart Rhythm

Clinical
Ablation
Intramyocardial mapping of ventricular premature depolarizations via septal venous perforators: Differentiating the superior intraseptal region from left ventricular summit origins

https://doi.org/10.1016/j.hrthm.2022.03.004Get rights and content

Background

The intramyocardial aspect of the left ventricular summit (LVS) can be mapped by advancing a unipolar guidewire into septal perforator branches of the anterior interventricular vein.

Objective

The purpose of this study was to differentiate between ventricular premature depolarizations (VPDs) with a basal superior intraseptal (SIS) site of origin and those originating from the epicardial LVS using septal intramyocardial mapping.

Methods

A retrospective cohort of patients with suspected LVS VPDs who underwent SIS unipolar mapping were reviewed for their clinical characteristics, mapping findings, and procedural outcomes.

Results

SIS mapping was successful in 44 of 47 cases (93.6%). VPD origin was SIS (defined as earliest activation from the intraseptal wire) in 20 patients (45.5%; median 23 ms pre-QRS). Procedure success was similar in patients with (group 1) and without (group 2) SIS origin (84% vs 87.5%, respectively; P = .842). Of the 10 patients in group 1 without presystolic endocardial activation, 5 (11.3% of all 44 cases) were successfully ablated from the left ventricular endocardium by using an anatomical approach targeting the endocardium closest to the earliest intraseptal activation site.

Conclusion

A significant proportion (45.5%) of VPDs that appear to arise from the left ventricular summit can be demonstrated to have a SIS origin using septal perforator venous mapping. A significant minority (11.3%) of these can be ablated from the endocardium by targeting from an anatomic vantage point closest to the earliest intraseptal activation site. The described strategy may help differentiate true LVS VPDs from those with SIS sites of origin.

Introduction

The left ventricular summit (LVS), an anatomical landmark described by McAlpine1 as the highest point of the left ventricular (LV) epicardium (where the upper end of the anterior interventricular sulcus joins the aortic portion of the LV ostium), represents a challenge for catheter ablation of ventricular arrhythmias (VAs) owing to anatomical constraints to performing detailed mapping and delivering adequate radiofrequency (RF) lesions.2,3 Despite epicardial origin, LVS arrhythmias can sometimes be successfully ablated from adjacent endocardial structures, such as the left coronary sinus of Valsalva, the LV endocardium below the aortic valve, and occasionally the anterior aspect of the right ventricular outflow tract.4,5 In recent years, intramyocardial foci have also been recognized as another reason for failure,6, 7, 8 demonstrated when the earliest electrograms are recorded from the proximal septal branches of the anterior interventricular vein (AIV), below the epicardial portion of the LVS.9

Differentiation of a basal superior intraseptal (SIS) origin (Figure 1) from the epicardial LVS has important implications for the optimal ablation site and outcomes. Small series reported successful ablation from these venous septal perforator branches,10 although again limited by technical challenges and RF delivery within the coronary venous system.11 This study aims to (1) differentiate LVS sites of origin from SIS ventricular premature depolarizations (VPDs) and (2) evaluate whether intramyocardial recordings can facilitate an anatomically guided ablation approach.

Section snippets

Methods

This study conforms to the guiding principles of the Declaration of Helsinki as revised in 2013 and has been approved by our institutional committee on human research. All patients provided written informed consent in accordance with institutional guidelines, and procedural indications were consistent with the 2019 HRS expert consensus statement on catheter ablation of VAs.12

Intraseptal mapping results

Intraseptal mapping was successfully performed in 44 of 47 patients (93.6%), with no complications related to mapping. Intraseptal activation was presystolic in 26 (59.1%), on time in 11 (25%), and after VPD onset in the remaining 7 patients (15.9%). After mapping neighboring structures, patients were divided into group 1 or group 2 (with or without SIS origin, respectively), as depicted in Figure 3. In 20 patients (45.5%), earliest activation was intraseptal (group 1). Of the remaining 24

Discussion

Catheter ablation of LVS arrhythmias is challenging, with procedure failure in more than a third of patients despite epicardial mapping via the coronary venous circulation or the pericardial space.2 Common reasons for failure include difficult access, risk of coronary artery injury, and poor energy delivery due to high impedance or epicardial fat.3,14 Failure to record the earliest site of activation can be common in epicardial and intraseptal VPDs, which is another barrier to endocardial

Conclusion

In this large series of suspected LVS VPDs, most patients had anatomy suitable for SIS mapping, which can be performed safely and effectively. This recording technique allows for differentiation between SIS sites of origin from the epicardial LVS. A significant proportion of these patients (45.5%) with LVS-appearing VPDs were confirmed to have SIS origin. Most of these arrhythmias can be successfully ablated from the endocardium—even when endocardial mapping fails to reveal presystolic

References (22)

  • W.A. McAlpine

    Heart and Coronary Arteries: An Anatomical Atlas for Clinical Diagnosis, Radiological Investigation, and Surgical Treatment

    (1977)
  • Cited by (13)

    • Localized intramural reentry confined within the ventricular septum in lamin cardiomyopathy

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      Citation Excerpt :

      Epicardial mapping through coronary venous branches has gained popularity owing to refinement of mapping catheters and novel use of transcoronary venous ethanol. The septal venous perforators (SPV) that originate from the anterior interventricular vein (AIV) provides access into the basal superior intraseptal region of the left ventricle and may inform the most optimal vantage point for ablation.2 Anteroseptal substrates are among the most challenging in patients with dilated cardiomyopathies who present for VT ablation and the mechanisms are incompletely elucidated.

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    Funding Sources: This research was supported by the David & Karen Kovalcik Fund in Electrophysiology.

    Disclosures: The authors have no conflicts of interest to disclose.

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