Advanced Techniques for CRT Implantation

Abstract

Cardiac resynchronization therapy (CRT) is an important breakthrough for the drug-refractory heart failure patients with reduced left ventrical ejection fraction (LVEF: 120 ms). The primary objecive of CRT is the coordination of the myocardial contraction with a right atrial (RA), right ventrical (RV) and a left ventrical (LV) lead and a biventricular device. The standard approach for implantation of the LV lead is transvenous epicardial approach through the subclavian vein to the lateral or posterolateral sidebranch of the coronary sinus. The average implantation time of CRT in high volume centers is under 120 minutes. Nowadays the procedural success ranges between 87% and 96% (Alonso, 2009). Early complications were seen in 10% and late complications were reported in further 5.5% (Khan et al., 2009). However we do not have all the evidence based predicting criterias to select the CRT responders and the different definitions of responders are numerous (Paul et al., 2009), the basics of all comparison is the successful left and right ventricular lead implantation. The growing numbers of heart failure patients recieving CRT and the limitation of the first line transvenous approach enhanced the evolution of alternative techniques. In this chapter we focus on the advanced CRT techniques which might help to reach the optimal lead positions and increase the success rate of implantations. The standard transvenous approach unfortunately has significant drawbacks as it is totally dependent on the inconsistent venous anatomy. The tributaries of the coronary sinus is usually visualised by the late phase of left coronarography, direct contrast injecion or by inserting an occlusion balloon into the coronary sinus (CS). Several reasons can cause the inabilty to reach the desired sidebrach and to insert the LV lead. The main reasons are: inability to cannulate the CS caused by dilatated right atrium, atypical orifice of CS, prominent Thebesian valve, small vessel size of the CS, severe kinking of the vein or venous valve in the CS. The secondary reasons are the high pacing threshold or phrenic nerve stimulation at the optimal site, inability to fixate the lead at the desired position and the insuffitient experience of the implanters. Stenosis or occlusion of the subclavian vein, or presence of a persistent left superior vena cava might be the cause for alternative LV implantations. Small or occluded sidebranches or tortuous branches and CS dissection or perforations might overcome with advanced transvenous techniques. The selection of the optimal site is an unsettled debate. Several noninvasiv and invasive techniques were investigated to confirm the optimal site, but no clear proven evidence is shown for the selection. However there is a consesus that the lateral and posterolateral veins are preferable rather than the anterior or apical veins. The anterolateral vein might be selected as a last resort in the absence of lateral and posterolateral veins. The identification of the veins