heart failure (CHF) is a common debilitating and usually lethal condition
May 25, 2017
heart failure (CHF) is a common debilitating and usually lethal condition responsible for enormous burden on health care. is used in absence of the conventional bradyarrhthymic indications with an attempt to lead to optimization of AV delay and co-ordination of ventricular contraction. In 1990 Hochleitner et al  reported clinical Tubastatin A HCl improvement in patients with severe heart failure awaiting cardiac transplantation with implantation of a physiologic dual-chamber pacemaker (pacing at right atrium and right ventricle) with a programmed short atrioventricular (AV) delay. Brecker et al  in 1992 reported similar observations. However in a randomized cross over design with larger number of patients there was no significant improvement in the NYHA class or ejection fraction . Sack et al  and Guide et al reported similar negative results. Consequently it is difficult to advocate dual chamber pacing for heart failure management. The reasons for the discrepancies in the results of these studies is possibly due to the detrimental effect of pacing induced broadening of the QRS complex duration in severe ventricular disease resulting from Right Ventricular (RV) apical pacing offsetting the beneficial effect of increased ventricular filling time. As a result the focus has now shifted to Left Ventriuclar (LV) or biventricular (BiV) Tubastatin A HCl as opposed to RV pacing supplemented Tubastatin Tubastatin A HCl A HCl with the lessons learnt from Tubastatin A HCl the optimization of the AV delay. Electromechanical Cardiac Synchrony The association of asynchronous ventricular contraction with ventricular dysfunction has been recognized for many years. Tubastatin A HCl In recent years the presence of left bundle branch block (LBBB) has been shown to correlate with decreased LV function reduced peak dp/dt. LBBB results in asynchronous ventricular contraction with the LV lateral wall contracting much later TNFRSF16 that the inverventricular septum in addition there is an RV-LV asynchrony with RV contracting earlier than LV. The presence of conduction disturbances is seen in 20-30% of the patients with congestive heart failure and contributes to the worsening of symptoms due to improper co-ordination of LV contraction. Cardiac Resyndronisation Therapy (CRT) CRT aims at 3 different levels (a) AV level (b) intraventricular level (c) interventricular level. At present this is achieved by pacing or sensing the right atrium pacing the proper ventricle (close to the interventricular septum) and pacing the remaining ventricle (using the coronary venous branches) also known as biventricular pacing. Remaining Ventricular Lead Style Today’s LV qualified prospects possess lower profile with preformed curves. A lot of the qualified prospects adopted the same regular central-stylet technology with curves becoming designed to negotiate the variabilities in cardiac vein anatomy. Lately over-the-wire business lead deployment systems have already been created (Easytrak – Guidant Company St. Paul MN) and also have the process as an angioplasty. Overall the achievement price for implantation of left-sided qualified prospects runs from 75 to 93%. Implantation Technique The implantation of biventricular pacing can be more technically demanding than a dual chamber pacing for the reason of placing the LV pacing lead appropriately. Prior to the introduction of the endocardial LV pacing leads surgical implantation of these leads epicardially was the norm. It is now possible to pace by entering the cardiac veins which are approached through the coronary sinus and obtain a reasonable threshold in one of the cardiac veins. The presence number location size and tortousity of posterior and lateral branches is usually variable. The coronary veins are thus studied by contrast injections with a balloon inflated catheter within the coronary sinus and subsequently the lead can be placed precisely. The posterolateral veins yield the best haemodynamic outcome and are the ones targeted for the placement of LV leads. The findings from the PATH – CHF trial  suggest that increases in pulse pressures and DP/DT max were maximum at the mid lateral epicardial pacing sites compared with other regions of the left ventricle consequently posterolateral sites are currently targeted for left ventricular pacing. Kass et al  in 1999 demonstrated that LV single site pacing was equal or superior to biventricular pacing. Further studies would be needed to demonstrate whether LV pacing is equivalent. It is possible that LV.