Selective pacing sites.

he right ventricular apex (RVA) has always been the most used pacing site, because it is easily accessible and provides a stable lead position with a low dislodgment rate. However, it is well-known that long-term right ventricular apical pacing may have deleterious effects on left ventricular function by inducing a iatrogenic left bundle branch block, which can have strong influences on the left ventricle hemodynamic performances. More specifically, RVA pacing causes abnormal contraction patterns and the consequent dyssynchrony may cause myocardial perfusion defects, histopathological alterations, left ventricular dilation and both systolic and diastolic left ventricular dysfunction. All these long-term changes could account for the higher morbidity and mortality rates observe in patients with chronic RVA pacing compared with atrial pacing. This observation led to the reassessment of traditional approaches and to the research of alternative pacing sites, in order to get to more physiological pattern of ventricular activation and to avoid deleterious effects. Then, attempts were made with: right ventricular outflow tract (RVOT) pacing, direct His bundle pacing (DHBP), parahisian pacing (PHP) and bifocal (RVA + RVOT) pacing. For example, RVOT pacing, especially in its septal portion, is superior to the RVA pacing and it would determine a contraction pattern very similar to the spontaneous one, not only because the septal portions are the first parts to became depolarized, but also for the proximity to the normal conduction system. RVOT is preferable in terms of safety too. DHBP is an attractive alternative to RVA pacing because it leads to a synchronous depolarization of myocardial cells and, therefore, to an efficient ventricular contraction. So it would be the best technique, however the procedure requires longer average implant times and dedicated instruments and it cannot be carried out in patients affected by His bundle pathologies; furthermore, due to the His bundle fibrous area, higher pacing thresholds are required, causing accelerated battery depletion. For all these reasons, PHP could be considered an important alternative to DHBP, to be used on a large scale. Finally, bifocal pacing in CRT candidates, provides better acute hemodynamic performance than RVA pacing, derived from a minor intra- and interventricular dyssynchrony, expressed also by the QRS shortening. Then, bifocal pacing could be taken into account when RVA pacing is likely to be the origin of serious mechanical and electrical dyssynchrony or when CRT is contraindicated or technically impossible. So, whatever chosen as selective pacing site, you must look also at safety, effectiveness and necessary equipment for an optimal pacing site.

Short term prognostic role of NT-proBNP in patients after myocardial infarction.

AIM: The clinical and prognostic role of cardiac natriuretic peptides (CNP) in patients with heart failure is well known; recently, several studies have evaluated the possibility of using CNP to evaluate their potential prognostic role in patients with acute coronary syndromes (ACS). The aim of this study was to evaluate the short term prognostic value of NT-proBNP in 70 patients admitted for ACS. METHODS: The authors studied 70 patients with ACS, evaluating, at admission, clinical-anamnestic, instrumental and laboratory characteristics including NT-proBNP plasma levels. Patients were monitored in a 6-month-follow-up to record adverse fatal events and their possible correlation with baseline characteristics. RESULTS: The incidence of adverse events during the follow-up period was 28% (10 patients). In patients with adverse events, the authors observed lower left ventricle ejection fraction (P=0.01), higher prevalence of ST elevation myocardial infarction (P=0.03) and higher NT-proBNP levels (P=0.03), compared to those without adverse events. Moreover, the logistic regression analysis underlined how ST elevation myocardial infarction (P=0.05) and higher NT-proBNP levels (P=0.05) were the only predictive variables for adverse events during the follow up period. CONCLUSIONS: This study demonstrates the short term prognostic role of NT-pro BNP in patients admitted for ACS.