Using the 12-Lead ECG to Localize the Origin of Atrial and Ventricular Tachycardias: Part 2—Ventricular Tachycardia

Monomorphic ventricular tachycardia (VT) can arise from multiple different ventricular locations in the context of several different underlying myocardial substrates. Despite this variability, the surface 12-lead electrocardiograph (ECG) has proven to be a robust and reproducible initial mapping tool that can provide useful information in localizing the origin of both focal and reentrant forms of VT. The second part of this review series will look at the use of the ECG in mapping the various forms of VT encountered in clinical practice.     

Linear Ablation of Right Atrial Free Wall Flutter: Demonstration of Bidirectional Conduction Block as an Endpoint Associated With Long‐Term Success

Ablation of Right Atrial Free Wall Flutter. Introduction: Ablation for atypical atrial flutter (AFL) is often performed during tachycardia, with termination or noninducibility of AFL as the endpoint. Termination alone is, however, an inadequate endpoint for typical AFL ablation, where incomplete isthmus block leads to high recurrence rates. We assessed conduction block across a low lateral right atrial (RA) ablation line (LRA) from free wall scar to the inferior vena cava (IVC) or tricuspid annulus in 11 consecutive patients with atypical RA free wall flutter. Method and results: LRA block was assessed following termination of AFL, by pacing from the ablation catheter in the low lateral RA posterior to the ablation line and recording the sequence and timing of activation anterior to the line with a duodecapole catheter, and vice versa for bidirectional block. LRA block resulted in a high to low activation pattern on the halo and a mean conduction time of 201 ± 48 ms to distal halo. LRA conduction block was present in only 2 out of 6 patients after termination of AFL by ablation. Ablation was performed during sinus rhythm (SR) in 9 patients to achieve LRA conduction block. No recurrence of AFL was observed at long‐term follow‐up (22 ± 12 months); 3 patients developed AF. Conclusion: Termination of right free wall flutter is often associated with persistent LRA conduction and additional radiofrequency ablation (RFA) in SR is usually required. Low RA pacing may be used to assess LRA conduction block and offers a robust endpoint for atypical RA free wall flutter ablation, which results in a high long‐term cure rate. (J Cardiovasc Electrophysiol, Vol. 21, pp. 526‐531, May 2010)     

A histopathological comparison of the uvula between snorers and non-snorers

Snoring is a very common problem but there are few publications on the histological findings of the soft palate/uvula and these lack consistency. The relative proportions of tissue types in the base of the uvula removed from 17 adults who underwent uvulopalatopharyngoplasty for heavy snoring were therefore compared with 14 cadaveric specimens. The mean percentage of muscle from the snoring group was 12.1 % compared with 7.2% in the control group (P < 0.05). The percentage of fibrous tissue was greater in the cadavers (52.8% vs 45.5% in the snorers, P < 0.05). The percentage of muscle was inversely related to the percentage of fibrous tissue in the snoring group (P < 0.02). We hypothesize that these changes are a consequence of the repetitive forces on the soft palate during snoring rather than being related to the pathogenesis of snoring.     

The Implantable Cardioverter-Defibrillator Lead: Principles, Progress, and Promises

The prognostic benefit of the implantable cardioverter-defibrillator (ICD) has been well established in multiple settings and its use is consequently widespread. Modern-day ICD systems use transvenous high-voltage leads to act as the interface between the heart and the generator, allowing for the sensing of a cardiac activity and the delivery of both bradycardia and tachycardia therapy, including high-voltage, high-current shocks. The ICD lead is in many ways the most fragile and critical component of the ICD system, and is subjected to more stress than any other implanted medical device. It has similar components to a pacing lead including tip and ring electrodes, fixation mechanism, conductors, insulators, and connector pins. In addition, it also contains the high-voltage shock coils that allow the delivery of defibrillation therapy to the cardiac tissue. The materials used to manufacture each of these components have undergone little evolution from their initial pacing lead-derived origin, but promising progress in this area is now occurring and better conductors and insulators have been developed. Lead body design continues to be multiluminal rather than coaxial, but various iterations of this basic paradigm continue to be investigated. In addition to miniaturization of the entire ICD lead, new industry standard lead connectors will also be introduced to reduce complexity and pocket bulk. However, long-term failure rates have been considerable, with lead failure related to both conductor and insulator malfunction. It is hoped that recent improvements in an ICD lead design and manufacture will result in a good functionality with a reliable long-term performance.