Electrophysiological Interventions for Inherited Arrhythmia Syndromes

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IInherited arrhythmia syndromes are electrical myopathies with genetic origins and risk of sudden death. They may present from infancy through adulthood, although the specific diseases have stereotypic but variable phenotypic onset and severity. There is clinical and genetic overlap among the syndromes, with variable penetrance and expressivity. Although underlying mechanisms of arrhythmogenesis may differ between syndromes, the electrophysiological (EP), pharmacological, and interventional options overlap. Specifics of the genetics, pharmacological therapies, and lifestyle modifications have been reviewed recently and are beyond the scope of this article, which focuses on interventional electrophysiology for inherited arrhythmias. The congenital long-QT syndromes (LQTSs) are the prototypic group of inherited arrhythmias. They were initially described as autosomal-recessive LQTSs with congenital sensorineural hearing loss, Jervell and Lange-Nielson (JLN) syndrome,1 and the more common autosomal-dominant LQTS with normal hearing, Romano-Ward syndrome.2,3 LQTS is caused by mutations in ion channel (or related anchoring protein) –encoding genes,4–6 presenting with prolonged QTc, stress-induced syncope, ventricular arrhythmias, or sudden cardiac death (SCD). The diagnosis is ascertained from clinical symptom complex, family history, ECG manifestations (at baseline or with provocative stimulation), and genetic testing. The principal treatment is pharmacological for most LQTS patients.7,8 ### Interventions for Congenital Long-QT Syndromes #### Catheter Ablation There is little role for diagnostic EP testing in LQTS. Studies have shown that programmed ventricular stimulation, QT interval response to pacing, and infusion of β-blocking medication in LQTS are of limited value.9 Monophasic action potential studies demonstrated afterdepolarizations but were not prognostic, and proarrhythmia can occur with ventricular stimulation.10 #### Left Cardiac Sympathetic Denervation Left cardiac sympathetic denervation (LCSD) can reduce cardiac events in LQTS but is not commonly performed at many institutions.11 Indications for LCSD include failure of medical therapy or frequent implantable cardioverter-defibrillator (ICD) shocks. Clinical results vary, likely because of the level of sympathetic denervation and operator experience. Left cervicothoracic sympathectomy involves resection of …