Contemporary Management of Complex Ventricular Arrhythmias.

Percutaneous catheter ablation is an effective and safe therapy that can eliminate ventricular tachycardia, reducing the risks of both recurrent arrhythmia and shock therapies from a defibrillator. Successful ablation requires accurate identification of arrhythmic substrate and the effective delivery of energy to the targeted tissue. A thorough pre-procedural assessment is needed before considered 3D electroanatomical mapping can be performed. In contemporary practice, this must combine traditional electrophysiological techniques, such as activation and entrainment mapping, with more novel physiological mapping techniques for which there is an ever-increasing evidence base. Novel techniques to maximise energy delivery to the tissue must also be considered and balanced against their associated risks of complication. This review provides a comprehensive appraisal of contemporary practice and the evidence base that supports recent developments in mapping and ablation, while also considering potential future developments in the field.

Hourly variability in outflow tract ectopy as a predictor of its site of origin.

INTRODUCTION: Before ablation, predicting the site of origin (SOO) of outflow tract ventricular arrhythmia (OTVA), can inform patient consent and facilitate appropriate procedural planning. We set out to determine if OTVA variability can accurately predict SOO. METHODS: Consecutive patients with a clear SOO identified at OTVA ablation had their prior 24-h ambulatory ECGs retrospectively analysed (derivation cohort). Percentage ventricular ectopic (VE) burden, hourly VE values, episodes of trigeminy/bigeminy, and the variability in these parameters were evaluated for their ability to distinguish right from left-sided SOO. Effective parameters were then prospectively tested on a validation cohort of consecutive patients undergoing their first OTVA ablation. RESULTS: High VE variability (coefficient of variation ≥0.7) and the presence of any hour with <50 VE, were found to accurately predict RVOT SOO in a derivation cohort of 40 patients. In a validation cohort of 29 patients, the correct SOO was prospectively identified in 23/29 patients (79.3%) using CoV, and 26/29 patients (89.7%) using VE < 50. Including current ECG algorithms, VE < 50 had the highest Youden Index (78), the highest positive predictive value (95.0%) and the highest negative predictive value (77.8%). CONCLUSION: VE variability and the presence of a single hour where VE < 50 can be used to accurately predict SOO in patients with OTVA. Accuracy of these parameters compares favorably to existing ECG algorithms.

Bipolar Radiofrequency Ablation of Septal Ventricular Tachycardia Facilitated by an Intramural Catheter.

Intramural septal substrate presents a challenge in patients undergoing ventricular tachycardia ablation, in terms of both accurate mapping and ablation with unipolar radiofrequency energy. We present the first use of the novel 2-F octapolar catheter in accurately defining intramural septal scar and facilitating bipolar ablation. (Level of Difficulty: Advanced.).

Cardiac sarcoidosis in a patient with testicular seminoma.

Sarcoidosis is a multisystem disorder characterised by non-caseating granulomas that typically affect the lungs, skin and lymph nodes. Sarcoidosis has been associated with various cancers, and we describe the case of a patient with systemic sarcoidosis associated with testicular seminoma. This was originally diagnosed as stable sarcoid-like reaction. He subsequently presented with ventricular tachycardia. Cardiovascular MRI suggested cardiac sarcoidosis, which was confirmed by myocardial biopsy. This case highlights the association between some types of cancer and sarcoidosis. In addition, it highlights the importance of close follow-up for patients with a history of malignancy to monitor for sarcoid-like reactions and sarcoidosis, which are often difficult to differentiate clinically.

Day case complex devices: the state of the UK.

Objective: Complex cardiac devices including implantable cardioverter defibrillator (ICD) and cardiac resynchronisation therapy (CRT) devices can safely be implanted as a day case procedure as opposed to overnight stay. We assess how common day case complex device therapy is and the cost implications of more widespread adoption across the UK. Methods: A freedom of information request was sent to all centres performing complex cardiac devices across the UK to assess the adoption of this technique. Cost implications were assessed using Department of Health National Schedule of Reference Costs 2016-2017. Results: 100 UK centres were surveyed, 80% replied. Eighty per cent of UK centres already implant complex cardiac devices as a day case to some extent. 64.06% of centres have a protocol for this. 12.82% of centres do <25% of complex devices as a day case. 15.38% do 25%-50% as day case. 17.95% do 50%-75% as day case and 33.33% do >75% as day case. There was no relationship between centre volume and the proportion of devices done as a day case as opposed to overnight stay. The cost saving of performing a complex device as a day case as opposed to overnight stay was £412 per ICD, £525 per CRT-pacemaker and £2169 per CRT-defibrillator. Conclusions: Day case complex devices are already widespread across the UK, however, there is scope for increase. An increase in proportion of day case devices could translate to £5 583 265 in savings annually for the National Health Service if all centres performed 75% of devices as a day case.

Case of low dose clenbuterol toxicity.

We present a case of acute clenbuterol toxicity following ingestion of 20 µg of clenbuterol, resulting in symptoms of sympathetic activation, sinus tachycardia and electrolyte derangement. The patient was managed conservatively with fluid resuscitation, electrolyte replacement and monitoring, and discharged following a 5-day stay in hospital.

Reduced endothelial dependent vasodilation in vessels from TLR4(-/-) mice is associated with increased superoxide generation.

Toll like receptor (TLR)4 is a pattern recognition receptor expressed in endothelial and other cells, responsible for the sensing of endotoxin and host derived ligands. Our group has shown previously that the absence of TLR4 is associated with reduced endothelial dependent vasodilator responses and left heart hypertrophy in animal models. However, the mechanism behind reduced endothelial cell function in TLR4(-/-) mice is not known. We have used en face confocal imaging of mesenteric arteries from mice deficient in the TLR4 receptor stained with dihydroethidium (DHE) to measure superoxide production. Using the isometric wire myograph, mesenteric artery vasodilator responses to acetylcholine and MnCl(2) (a superoxide dismutase mimetic) were measured. Mesenteric arteries from TLR4(-/-) mice had a reduced endothelial dependent relaxant response and increased superoxide levels when stimulated with acetylcholine. Increased levels of superoxide, as detected by DHE staining, were seen in vessels from TLR4(-/-) mice, which were reduced to control levels in the presence of MnCl(2). Our observations suggest that loss of TLR4 increases superoxide generation which reduces the biological activity of endothelial derived nitric oxide and thereby explains the endothelial dysfunction and associated cardiovascular phenotype in TLR4(-/-) mice. These data implicate a novel cardio-protective role for TLR4 in vascular homeostasis.