Advertisement

Localized Intramural Reentry Confined Within the Ventricular Septum in Lamin Cardiomyopathy

Open AccessPublished:September 22, 2022DOI:https://doi.org/10.1016/j.hrcr.2022.09.010

      Key words

      INTRODUCTION

      High resolution electroanatomic mapping systems have greatly improved the ability to characterize the size and dimensions of the reentrant circuit responsible for human ventricular tachycardia (VT). The minimal dimension of critical isthmus regions may be less than 1 cm in over 25% of circuits mapped.
      • Tung R.
      • Raiman M.
      • Liao H.
      • et al.
      Simultaneous Endocardial and Epicardial Delineation of 3D Reentrant Ventricular Tachycardia.
      Despite advanced, detailed simultaneous epicardial and endocardial mapping, detection of intramural circuit components remains challenging. Epicardial mapping through coronary venous branches has gained popularity due to refinement of mapping catheters and novel use of transcoronary venous ethanol. The septal venous perforators (SPV) that orginate 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.
      • Guandalini G.S.
      • Santangeli P.
      • Schaller R.
      • et al.
      Intramyocardial mapping of ventricular premature depolarizations via septal venous perforators: Differentiating the superior intraseptal region from left ventricular summit origins.
      Anteroseptal substrates are among the most challenging in patients with dilated cardiomyopathies who present for VT ablation and the mechanisms are incompletely elucidated. Here, we report a case of a localized VT circuit within a midmyocardial septal substrate that was completely characterized by activation and entrainment mapping from one recording bipole pair within an SPV in a patient with Lamin cardiomyopathy.

      Case Report

      A 73 year old man with history of dilated cardiomyopathy and left ventricular ejection fraction of 39%, complete heart block status post permament pacemaker placement 15 years ago with upgrade to biventricular implantable cardioverter defibrillator (ICD) two years ago presented with recurrent episodes of VT and appropriate ICD therapies despite anti-arrhythmic drug therapy with sotalol. Cardiac MRI showed midmyocardial delayed enhancement with full-length midmyocardial scar from the basal anteroseptum to inferoseptum.(Figure 1A) He underwent initial ablation where septal VTs were mapped and targeted from the right ventricle. Due to increasing VT burden with appropriate device therapies, including multiple shocks, he was referred for repeat ablation.
      Figure thumbnail gr1
      Figure 1A. Midmyocardial septal scar and mapping catheters positioned to map VT activation. A duodecapolar catheter (DD) was positioned along the RV septum and ablation catheter (Abl) on the LV septum via transseptal approach. A 2F mapping catheter was positioned with the two most distal electrodes within the septal perforating vein (SPV). B. An intraseptal fractionated late potential is recorded from within the SPV, which yields a near-perfect pacemap match for the clinical induced VT with stimulus to QRS latency.
      In anticipation of mapping a septal VT, a linear multielectrode catheter (Livewire, Abbott, Abbott Park, IL) was placed in the septal RVOT and an ablation catheter (FlexAbility, Abbott, Abbott Park, IL) was positioned on the LV basal anterior septum via transseptal approach. A diagnostic 2F microcatheter (EPstar, 1.5mm distal electrode, 1.3mm proximal electrodes, 5-5-5mm spacing, Baylis Medical, Montreal QC, Canada) was placed into the distal coronary sinus to record within the AIV and SPV (Figure 1A). During sinus rhythm, the Baylis catheter placed in the AIV/SPV recorded a low voltage fractionated and split late potential (LP) with discrete isoelectric segment. Pacemapping from the AIV and SPV showed a near-perfect QRS match with stimulus to QRS latency for the clinical VT (Figure 1B).
      VT was induced with programmed triple extrastimuli from the RVOT. The local intraseptal fractionated and late electrogram (EGM) exhibited pandiastolic activation spanning the entirety of diastole during VT . Figure 2A shows the continuous tracing from paced rhythm during sinus into VT from triple extrastimuli (last 5 beats of drive removed) at a constant gain to illustrate that diastolic activation during VT is not noise given the clean baseline. Figure 2B shows VT with instraseptal recording at 150mm/s. Activation mapping was performed from the right ventricular (RV) endocardium, left ventricular (LV) endocardium, epicardially via great cardiac vein/AIV, and intramurally via SPV. Focal exit activation was observed on both LV (-45ms pre-QRS) and RV endocardium (at QRS onset) (Figure 3A). Entrainment from a slightly more proximal position within the SPV showed concealed fusion with post pacing interval (PPI) exactly matching VT cycle length and the S-V interval equal to the EGM-QRS interval measured from SPd, proving critical circuitry confined within the interventricular septum (Figure 3B).
      Figure thumbnail gr2
      Figure 2A. Continuous strip from sinus rhythm with induction of VT with triple extrastimuli (500-300-260-250ms) to demonstrate constant gain and minimal baseline noise. 5 beats of the drive cycle have been removed. The intraseptal late potential (SPd) recorded during pacing rhythm become pandiastolic during VT. B. 12 lead of VT (TCL 360ms) with SPV recording spanning entirety of diastole at 150 mm/s.
      Figure thumbnail gr3
      Figure 3A. Activation mapping and B. Concealed entrainment of Ventricular Tachycardia with C. termination during radiofrequency delivery. The intraseptal late potential is finally eliminated and dissociated after ablation from the RV side of the septum.
      Ablation was performed from the corresponding LV endocardial surface and terminated VT within 10 seconds (Figure 3C, left). Additional ablations were performed but failed to alter the split and late potentials. Therefore, ablation was then performed from the septal right ventricular outflow tract (RVOT) with eventual elimination of LPs and dissociated activity (Figure 3C, right). The clinical VT was rendered noninducible.
      A second VT with left bundle branch block morphology with V4 transition and indeterminate axis with lead 2 more postive than lead 3 consistent with a mid septal right-sided breakthrough was then identified with activation mapping confirming the exit site inferior to the prior lesions. The periaortic region was extensively targeted without termination of VT and two sequential injections of 4 mLs of 100% ethanol were infused into the septal perforator vein with termination of targeted VT 61 seconds after ethanol injection. Due to the small size of the perforator vein with occlusion upon cannulation using coronary guide catheter (no contrast reflux), a balloon technique was not implemented. However, VT remained reinducible at a faster rate and therefore additional ablation were performed at 50W from the LV and RV septum. VT has not recurred for 9 months at the time of this report.

      DISCUSSION

      Catheter ablation for drug-refractory VT in patients with dilated cardiomyoapathies, particularly in those with genetic mutations such as LMNA and TTN, are associated with VT recurrence rates that are among the highest in structural heart disease.
      • Kumar S.
      • Androulakis A.F.
      • Sellal J.M.
      • et al.
      Multicenter Experience With Catheter Ablation for Ventricular Tachycardia in Lamin A/C Cardiomyopathy.
      • Enriquez A.
      • Liang J.
      • Smietana J.
      • et al.
      Substrate Characterization and Outcomes of Ventricular Tachycardia Ablation in TTN (Titin) Cardiomyopathy: A Multicenter Study.
      • Ebert M.
      • Wijnmaalen A.P.
      • de Riva M.
      • et al.
      Prevalence and Prognostic Impact of Pathogenic Variants in Patients With Dilated Cardiomyopathy Referred for Ventricular Tachycardia Ablation.
      The advent of improved genetic testing has led to improved identification of likely pathologic variants associated with dilated cardiomyopathy and VT allowing for better understanding of the substrate and outcomes based on the specific etiology of dilated cardiomyopathy. Patients with pathologic genetic variants, when compared to those without pathologic variants, were shown to have signicantly lower 2-year VT free survival and increased cardiac and all cause mortality.
      • Ebert M.
      • Wijnmaalen A.P.
      • de Riva M.
      • et al.
      Prevalence and Prognostic Impact of Pathogenic Variants in Patients With Dilated Cardiomyopathy Referred for Ventricular Tachycardia Ablation.
      LMNA variants in particular, have been shown to have high rates of arrhythmia recurrence, progression of cardiomyopathy to end stage heart failure, and high mortality.
      • Kumar S.
      • Androulakis A.F.
      • Sellal J.M.
      • et al.
      Multicenter Experience With Catheter Ablation for Ventricular Tachycardia in Lamin A/C Cardiomyopathy.
      Lamin cardiomayopathy classically involves the septum and periaortic region and seems to be predominantly related to reentry in and around regions of scar. Periaortic VTs have been increasingly described with regard to reentrant mechanism and circuit characteristics.
      • Nishimura T.
      • Beaser A.D.
      • Aziz Z.A.
      • et al.
      Periaortic ventricular tachycardia in structural heart disease: Evidence of localized reentrant mechanisms.
      Midmyocardial scar patterns are associated with adverse outcomes and may require adjunctive strategies such as bipolar ablation with half normal saline as irrigant. While the method and yield of intramural mapping via coronary veins have been described
      • Guandalini G.S.
      • Santangeli P.
      • Schaller R.
      • et al.
      Intramyocardial mapping of ventricular premature depolarizations via septal venous perforators: Differentiating the superior intraseptal region from left ventricular summit origins.
      ,
      • Briceno D.F.
      • Enriquez A.
      • Liang J.J.
      • et al.
      Septal Coronary Venous Mapping to Guide Substrate Characterization and Ablation of Intramural Septal Ventricular Arrhythmia.
      ,
      • Tavares L.
      • Lador A.
      • Fuentes S.
      • et al.
      Intramural Venous Ethanol Infusion for Refractory Ventricular Arrhythmias: Outcomes of a Multicenter Experience.
      , complete activation mapping incorporating midmyocardial activation with both sides of the septum, to the best of our knowledge, has not been previously described. While intraseptal entrainment was demonstrated, definitive proof of participation of the entire pandiastolic signal recorded would require entrainment from each component with repeated overdrive sequences, which was not performed in this case. Recording of adjacent bystander components cannot be excluded. Entrainment from either RVOT or LVOT was not performed. The ability to record these presented signals requires cannulation of septal perforating vein in close proximity or within the superior basal intraseptal substrate.
      Prior studies have not demonstrated localized reentry completely confined within the intramural septum, which is the novelty of this report. These descriptions reiterated the propensity of LMNA to predominantly involve the septum
      • Ebert M.
      • Wijnmaalen A.P.
      • de Riva M.
      • et al.
      Prevalence and Prognostic Impact of Pathogenic Variants in Patients With Dilated Cardiomyopathy Referred for Ventricular Tachycardia Ablation.
      ,
      • Zeppenfeld K.
      Ventricular Tachycardia Ablation in Nonischemic Cardiomyopathy.
      , with Kumar et al
      • Kumar S.
      • Androulakis A.F.
      • Sellal J.M.
      • et al.
      Multicenter Experience With Catheter Ablation for Ventricular Tachycardia in Lamin A/C Cardiomyopathy.
      showing majority of VT in LMNA patients originating from basal septum and exiting toward the left ventricle; however, intramural VT circuits were inferred rather than mapped via SPV. We have previously proposed a definition of localized reentry as >50% of diastole within <1.5 cm path.
      • Jiang R.
      • Nishimura T.
      • Beaser A.D.
      • et al.
      Spatial and transmural properties of the reentrant ventricular tachycardia circuit in arrhythmogenic right ventricular cardiomyopathy: Simultaneous epicardial and endocardial recordings.
      In this case, the entire diastolic phase was recorded from a single bipole pair.
      Strategies such as substrate modification via transcoronary venous ethanol may warrant further consideration, particularly when a full length septal scar is present on MRI, which portends a poor prognosis.
      • Nishimura T.
      • Patel H.N.
      • Wang S.
      • et al.
      Prognostic value of cardiac magnetic resonance septal late gadolinium enhancement patterns for periaortic ventricular tachycardia ablation: Heterogeneity of the anteroseptal substrate in nonischemic cardiomyopathy.
      Although transcoronary venous ethanol ablation was attempted with limited efficacy by Kumar et al. in cases of VT refractory to multiple prior radiofrequency ablations, the midmyocardial VT circuits were not fully characterized.
      • Kumar S.
      • Androulakis A.F.
      • Sellal J.M.
      • et al.
      Multicenter Experience With Catheter Ablation for Ventricular Tachycardia in Lamin A/C Cardiomyopathy.
      Further study to evaluate efficacy of transcoronary venous ethanol ablation in intramural VT
      • Tavares L.
      • Lador A.
      • Fuentes S.
      • et al.
      Intramural Venous Ethanol Infusion for Refractory Ventricular Arrhythmias: Outcomes of a Multicenter Experience.
      , particularly when used in combination with complete mapping of the intramural cricuit via coronary veins should be considered.
      Due to high rates of recurrent VT in associated with Lamin cardiomyopathies, Early collaboration and consultation with heart failure team is warranted to discuss advanced management options given modest outcomes from ablation and high risk of mortality from progression of heart failure. This case provides further mechanistic insights into the nature of septal VTs in this challenging patient population that may be entirely missed by traditional endocardial and epicardial mapping techniques.

      CONCLUSIONS

      In midmyocardial septal scar substrates, SPV recordings may provide critical intramural information to elucidate the spatial dimensions and location of circuit challenging VTs. Localized reentry recorded from a single bipole pair can be confined completely within the septum, which cannot be fully characterized from either endocardial surface.

      REFERENCES

        • Tung R.
        • Raiman M.
        • Liao H.
        • et al.
        Simultaneous Endocardial and Epicardial Delineation of 3D Reentrant Ventricular Tachycardia.
        J Am Coll Cardiol. 2020; 75: 884-897
        • Guandalini G.S.
        • Santangeli P.
        • Schaller R.
        • et al.
        Intramyocardial mapping of ventricular premature depolarizations via septal venous perforators: Differentiating the superior intraseptal region from left ventricular summit origins.
        Heart Rhythm. 2022;
        • Kumar S.
        • Androulakis A.F.
        • Sellal J.M.
        • et al.
        Multicenter Experience With Catheter Ablation for Ventricular Tachycardia in Lamin A/C Cardiomyopathy.
        Circ Arrhythm Electrophysiol. 2016; 9
        • Enriquez A.
        • Liang J.
        • Smietana J.
        • et al.
        Substrate Characterization and Outcomes of Ventricular Tachycardia Ablation in TTN (Titin) Cardiomyopathy: A Multicenter Study.
        Circ Arrhythm Electrophysiol. 2021; 14e010006
        • Ebert M.
        • Wijnmaalen A.P.
        • de Riva M.
        • et al.
        Prevalence and Prognostic Impact of Pathogenic Variants in Patients With Dilated Cardiomyopathy Referred for Ventricular Tachycardia Ablation.
        JACC Clin Electrophysiol. 2020; 6: 1103-1114
        • Nishimura T.
        • Beaser A.D.
        • Aziz Z.A.
        • et al.
        Periaortic ventricular tachycardia in structural heart disease: Evidence of localized reentrant mechanisms.
        Heart Rhythm. 2020; 17: 1271-1279
        • Briceno D.F.
        • Enriquez A.
        • Liang J.J.
        • et al.
        Septal Coronary Venous Mapping to Guide Substrate Characterization and Ablation of Intramural Septal Ventricular Arrhythmia.
        JACC Clin Electrophysiol. 2019; 5: 789-800
        • Tavares L.
        • Lador A.
        • Fuentes S.
        • et al.
        Intramural Venous Ethanol Infusion for Refractory Ventricular Arrhythmias: Outcomes of a Multicenter Experience.
        JACC Clin Electrophysiol. 2020; 6: 1420-1431
        • Zeppenfeld K.
        Ventricular Tachycardia Ablation in Nonischemic Cardiomyopathy.
        JACC Clin Electrophysiol. 2018; 4: 1123-1140
        • Jiang R.
        • Nishimura T.
        • Beaser A.D.
        • et al.
        Spatial and transmural properties of the reentrant ventricular tachycardia circuit in arrhythmogenic right ventricular cardiomyopathy: Simultaneous epicardial and endocardial recordings.
        Heart Rhythm. 2021; 18: 916-925
        • Nishimura T.
        • Patel H.N.
        • Wang S.
        • et al.
        Prognostic value of cardiac magnetic resonance septal late gadolinium enhancement patterns for periaortic ventricular tachycardia ablation: Heterogeneity of the anteroseptal substrate in nonischemic cardiomyopathy.
        Heart Rhythm. 2021; 18: 579-588