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The difference SA-VA provides a simpler electrophysiologic maneuver that reliably differentiates atypical AVNRT from AVRT regardless of concealed AP location.

Multipoint pacing activation significantly reduces battery longevity compared with that for conventional CRT configuration. When reasonable MPP LV vector PCTs (≤4.0 V) are achieved, the decrease in battery longevity is relatively small which may prompt the clinician to activate MPP.

The subcutaneous implantable cardioverter-defibrillator (S-ICD) has recently been approved for commercial use in Europe, New Zealand and the United States. It is comprised of a pulse generator, placed subcutaneously in a left lateral position, and a parasternal subcutaneous lead-electrode with two sensing electrodes separated by a shocking coil. Being an entirely subcutaneous system it avoids important periprocedural and long-term complications associated with transvenous implantable cardioverter-defibrillator (TV-ICD) systems as well as the need for fluoroscopy during implant surgery. Suitable candidates include pediatric patients with congenital heart disease that limits intracavitary lead placements, those with obstructed venous access, chronic indwelling catheters or high infection risk, as well as young patients with electrical heart disease (e.g., Brugada Syndrome, long QT syndrome, and hypertrophic cardiomyopathy). Nevertheless, given the absence of intracavitary leads, the S-ICD is unable to offer pacing (apart from short-term post-shock pacing). It is therefore not suitable in patients with an indication for antibradycardia pacing or cardiac resynchronization therapy, or with a history of repetitive monomorphic ventricular tachycardia that would benefit from antitachycardia pacing. Current data from initial clinical studies and post-commercialization "real-life" case series, including over 700 patients, have so far been promising and shown that the S-ICD successfully converts induced and spontaneous ventricular tachycardia/ventricular fibrillation episodes with associated complication and inappropriate shock rates similar to that of TV-ICDs. Furthermore, by using far-field electrograms better tachyarrhythmia discrimination when compared to TV-ICDs has been reported. Future results from ongoing clinical studies will determine the S-ICD system's long-term performance, and better define suitable patient profiles.

Symptomatic bradycardia is effectively treated with the implantation of a cardiac pacemaker. Although a highly successful therapy, during recent years there has been a focus on the negative effects associated with long-term pacing of the apex of the right ventricle (RV). It has been shown in both experimental and clinical studies that RV pacing leads to ventricular dyssynchrony, similar to that of left bundle branch block, with subsequent detrimental effects on cardiac structure and function, and in some cases adverse clinical outcomes such as atrial fibrillation, heart failure and death. There is substantial evidence that patients with reduced left ventricular function (LVEF) are at particular high risk of suffering the detrimental clinical effects of long-term RV pacing. The evidence is, however, incomplete, coming largely from subanalyses of pacemaker and implantable cardiac defibrillator studies. In this group of patients with reduced LVEF and an expected high amount of RV pacing, biventricular pacing (cardiac resynchronization therapy) devices can prevent the negative effects of RV pacing and reduce ventricular dyssynchrony. Therefore, cardiac resynchronization therapy has emerged as an attractive option with promising results and more clinical studies are underway. Furthermore, specific pacemaker algorithms, which minimize RV pacing, can also reduce the negative effects of RV stimulation on cardiac function and may prevent clinical deterioration.

Reference values and differences of LVTM and LVTM% in various cardiac conditions are given for the first time. Quantification of these parameters with CMR may be clinically useful in the differential diagnosis between left ventricular noncompaction and other cardiac diseases. Exclusion of LVT from myocardium alters left ventricular morphological and functional parameters, which have significant clinical importance.

Background: The purpose of this study was to evaluate the feasibility of the use of a quadripolar left ventricular (LV) lead for cardiac resynchronization therapy and to compare its acute and mid-term outcomes with those obtained with bipolar leads. Cardiac resynchronization exhibits a high incidence of problems involving the LV lead when conventional leads are used, and these problems may be minimized by using multipolar leads.

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