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Transcatheter electrosurgery is a versatile tool that can be used to cut cardiac tissue without the need for a sternotomy, cardiopulmonary bypass, and cardioplegia. With adequate imaging and suitable anatomy, any cardiac tissue can be cut. Thus, transcatheter electrosurgery can provide bespoke therapies for complex patients who often have no other good treatment options. In this review, we will discuss the common applications for electrosurgical tissue traversal and laceration, including transcaval access, BASILICA, LAMPOON, and ELASTA-Clip, summarizing the evidence and the key technical steps for each.

BACKGROUND: Left ventricular outflow tract (LVOT) obstruction complicates hypertrophic cardiomyopathy and transcatheter mitral valve replacement. Septal reduction therapies including surgical myectomy and alcohol septal ablation are limited by surgical morbidity or coronary anatomy and high pacemaker rates respectively. We developed a novel transcatheter procedure, mimicking surgical myotomy, called SESAME (SEptal Scoring Along the Midline Endocardium). METHODS: SESAME was performed in 5 naïve pigs and 5 pigs with percutaneous aortic banding-induced left ventricular hypertrophy. Fluoroscopy and intracardiac echocardiography guided procedures. Coronary guiding catheters and guidewires were used to mechanically enter the basal interventricular septum. Imparting a tip bend to the guidewire enabled intramyocardial navigation with multiple degrees of freedom. The guidewire trajectory determined the geometry of SESAME myotomy. The myocardium was lacerated using transcatheter electrosurgery. Cardiac function and tissue characteristics were assessed by cardiac magnetic resonance (CMR) at baseline, post-procedure, and at 7- or 30-day follow-up. RESULTS: SESAME myotomy along the intended trajectory was achieved in all animals. The myocardium splayed after laceration, increasing LVOT area (753mm(2) to 854mm(2), p=0.008). Two naïve pigs developed ventricular septal defects due to excessively deep lacerations in thin baseline septa. No hypertrophy model pig, with increased septal thickness and left ventricular mass compared with naïve pigs, developed ventricular septal defects. One animal developed left axis deviation on ECG but no higher conduction block was seen in any animal. Coronary artery branches were intact on angiography with no infarction on CMR late gadolinium imaging. CMR chamber volumes, function, flow and global strain were preserved. No myocardial oedema was evident on CMR T1 mapping. CONCLUSIONS: This pre-clinical study demonstrated feasibility of SESAME, a novel transcatheter myotomy to relieve LVOT obstruction. This percutaneous procedure using available devices, with a safe surgical precedent, is readily translatable into patients.

Toxicity studies in animals are carried out to identify the intrinsic hazard of a substance to support risk assessment for humans. In order to identify opportunities to minimise animal use in regulatory toxicology studies, a review of current study designs was carried out. Pharmaceutical companies and contract research organisations in the UK shared data and experience of standard toxicology studies (ranging from one to nine months duration) in rodents and non-rodents; and carcinogenicity studies in the rat and mouse. The data show that variation in study designs was primarily due to (i) the number of animals used in the main study groups, (ii) the use of animals in toxicokinetic (TK) satellite groups, and (iii) the use of animals in off-treatment recovery groups. The information has been used to propose a series of experimental designs where small adjustments could reduce animal use in practice, while maintaining the scientific objectives.