1 Introduction

Ablation for papillary muscle (PM) premature ventricular contractions (PVC) is challenging, typically requiring multiple ablation lesions and having a high recurrence rate [1]. PMs are highly mobile structures that make achieving catheter stability difficult, particularly on the sides of the PM due to the shape of the structure during the occurrence of PVCs [2]. Creating an accurate activation map is further complicated by the presence of Purkinje network inside the PM that results in rapid conduction and subsequently small differences in activation timing between neighboring sites, producing a wide area of earliest activation [3].

Multipolar catheters are known to generate higher fidelity activation maps due to narrow bipolar spacing [4], however, their relatively large size can make mapping challenging in the narrow space around the PMs and their use has been associated with the generation of ventricular ectopy [4]. The aim of this study was to explore the utility of intracardiac echocardiogram (ICE) guided mapping of the PMs using the multipolar catheter Advisor HD Grid Mapping Catheter, Sensor Enabled (Abbott. Abbott Park, IL, USA).

2 Methods

We prospectively recruited consecutive cases between January 2021 and December 2022 of patients undergoing repeat ablation of symptomatic PVCs originating from the PMs. Patients with no acute PVC suppression during the index ablation procedure or recurrence within 12-h post-ablation were considered failed. Clinical recurrence was defined as recurrence of PVCs at 3  months post-index procedure.

All antiarrhythmic drugs (AADs) were discontinued at least 2 days pre-procedure.

The ICE catheter was positioned in the RV inflow to visualize the PMs due to their intracavitary location. Activation maps of the index procedures created with point-by-point technique with the ablation catheter were compared to those of the repeat procedure using the HD Grid catheter (Fig. 1i Panel A). The maps compared the activation of earliest point, location of earliest activation, and zone of earliest activation.

Fig. 1
figure 1

i Diffuse activation seen on activation map created using point-by-point technique (A). (B), (C), (D) show HD grid on different surfaces of the papillary muscle, location is confirmed by intracardiac echocardiography (ICE). ICE facilitated positioning of the HD grid allows accurate anatomical representation of papillary muscle in addition to activation (F) (G). The HD Grid follows the movement of the papillary muscle during sinus rhythm, PVCs and respiratory cycle. Simultaneous sampling of multi activation points on the same surface allows identification of small differences in activation timing sequence. In addition, narrow bipole spacing allows documentation of Purkinje potentials (white arrow) (E). ii Twelve-lead electrocardiograms displaying premature ventricular contractions (PVC) originating from the anterolateral papillary muscle (APM) and posteromedial papillary muscle (PPM). In patients 1, 2, 3, and 4 the PVC morphology demonstrated a RBBB pattern in V1 and left superior axis suggestive of PPM origin. In patients 5, 6, 7, 8, 9, and 10 PVC morphology demonstrated a RBBB pattern in V1 and right inferior axis suggestive of APM origin

Full size image

Specifically, for the HD Grid, the geometry of the PM was created independently of the left ventricular anatomy after confirming stable location of the HD Grid in all sites of the PM (Fig. 1i, Panel F, G). Activation points were acquired only after confirming stable positioning of the multipolar catheter on each side of the PM and never during roving (Fig. 1i Panel B, C, D).

Acute procedural success was evaluated post-procedure by telemetry. Twenty-four–hour Holter monitoring was performed at the 3-month follow-up visit.

3 Results

10 patients (4 female, 64.5 years ± 10.6) underwent repeat the procedure for failed ablation (6 patients) or recurrence (4 patients) of symptomatic PVC with PM origin (4 posteromedial) 7.2 months post-index procedure (Fig. 1ii) Site of origin was identified in the same segment for all cases suggesting recurrence as opposed to new origin or differential exit. The activation timing of earliest site did not differ significantly between the index and repeat procedure (−32−34ms, p = 0.39). However, the zone of early activation was significantly larger during the index procedure compared to the repeat. PVC suppression was achieved in 7/10 patients, after 516 s of ablation, whereas 3 patients had PVC suppression but recurrence while in the recovery area.

The three patients that experienced a recurrence of PVCs acutely post-procedure had an average PVC burden of 9.6% on 24-h Holter monitor at 3 months. For the remaining 7 patients, all AADs were discontinued during follow-up and complete elimination of PVCs by 24-hour Holter monitors was noted at 3 months.

4 Discussion

Multielectrode mapping catheters have become the mainstay for complex arrhythmia mapping due to decrease in mapping time, less need for fluoroscopy, and increased clarity of local electrograms [4]. In their case series, Cai et al. report the use of a linear duodecapolar catheter for mapping PM PVCs for precisely localizing the site of origin [5]. More recent multipolar mapping catheters (MPMCs) with fixed electrode spacing utilizing a single plane catheter design have gained additional advantages when mapping some structures, including the PMs. This design allows for catheter stability, higher simultaneous sampling density, reduction in mechanical/catheter-induced ectopy, as well as local spatiotemporal dispersion characteristics of a single beat acquisition [6]. Tan et al. report their experience using the Optrell MPMC, while the catheter provided detailed PVC activation maps, operators reported difficulty manipulating the catheter near highly trabeculated surfaces proximal to the PMs and valve apparatus [6]. Papillary muscle PVCs are often mid-myocardial in origin, and localizing the site of origin is essential with intramural ventricular arrhythmias [7].

We demonstrate that the diagnostic catheter characteristics of the HD Grid MPMC are particularly important when mapping the PMs. ICE allows for accurate sequential positioning of the HD Grid on all surfaces of the PM allowing for synchronized movement of the two, during heart beating and respiratory movements (Fig. 1i Panel F, G). This eliminates the need for respiratory and beat gating during acquisition of the activation point, minimizing errors in the projection of the activation point on the surface of PM. This technique enables the simultaneous sampling of multiple neighboring points during a single beat and allows the identification of small differences in activation timing and sequence that are typical with PM conduction (Fig. 1i Panel E). Furthermore, the narrow bipolar spacing allows the identification of Purkinje fibers potentials that are often involved in reentrant circuits. Complimentary to activation mapping, through qualitative assessment we observed our technique can improve the accuracy of pace-mapping. By allowing the entire catheter to encompass either the anterior or posterior aspect of the PM, we were able to pace-map different bipoles around the mapping catheter without further manipulation and define the site with the closest match to the clinical PVC morphology.

5 Conclusion

Positioning of the HD Grid mapping catheter guided by ICE may provide more accurate activation and pace-mapping for papillary muscle PVCs during repeat catheter ablation.