Pressure-volume loop analysis during pacemaker/ICD implantations facilitates to determine the optimal LV pacing site. Patients with chronic RV pacing showed a significant acute improvement in LV function when LV pacing or biventricular pacing is applied.

Bifocal RIGHT ventricular stimulation (BRIGHT) is an ongoing, randomized, single-blind, crossover study of atrial synchronized bi-right ventricular (RV) pacing in patients in New York Heart Association heart failure functional class III, a left ventricular ejection fraction <35%, left bundle branch block and QRS complexes >/=120 ms. This analysis compared the electrical and handling characteristics, and the complications of pacing at the RV apex (Ap) with passive, versus RV outflow tract (OT) with active fixation leads. A mean of 1.6 +/- 0.9 and 2.2 +/- 2.0 attempts were needed to position the Ap and OT leads, respectively (ns). R-wave amplitudes at Ap versus OT were 23 +/- 13 mV versus 14 +/- 8 mV (n = 36, P < 0.001). R-wave amplitudes at the Ap remained stable between implant and M7. R-wave amplitudes at the OT could not be measured after implantation. In two patients, atrioventricular block occurred during active fixation at the OT. Conduction recovered spontaneously within 4 months. Ventricular fibrillation was induced in one patient during manipulation of an Ap lead in the RV. Marked differences were found between leads positioned in the OT versus Ap, partly related to the difference in lead design. Mean R-wave amplitude was higher at the Ap that at the OT. Ease and success rate of lead implant was similar in both positions.

CRT in patients with chronic RV pacing causes significant improvement of both LV function as measured by pressure-volume loops during implantation and clinical and echocardiographic improvement during follow-up. Pressure-volume loops during implantation may facilitate selection of the most optimal pacing site.

Left interventricular septal pacing is feasible. In our study it was safely performed in six goats. The pacing threshold was low, and the stability of the lead system was good. Implantations in humans and animals and haemodynamic evaluations are needed to reveal the potential benefits of this new form of left interventricular septal pacing.

Single lead physiological pacing with right ventricular apex stimulation is feasible in patients with normal sinus node function and is associated with lower costs and a reduced complication rate. Left ventricular or biventricular pacing using the tributaries of the coronary sinus was reported to improve functional status and quality-of-life in patients with advanced congestive heart failure and intraventricular conduction delays. In addition, the proximal part of the coronary sinus has been successfully used for left atrial stimulation. The feasibility and pacing characteristics of left atrial- and left ventricular-based temporary pacing using a conventional single pass lead were studied. The tip of the lead was advanced in a distal position of the lateral or posterolateral branches of the coronary sinus, providing a stable position of the middle and proximal electrode pair in the first 2-7 cm of the coronary sinus. A successful stable position was achieved in 13 of 21 consecutive attempts. Using overlapping biphasic (OLBI) stimulation, left atrial and left ventricular pacing threshold were 2.3 +/- 0.6 and 2.5 +/- 0.5 V, respectively. Acceptable sensing values were measured for P waves (4.1 +/- 0.7 mV) and R waves (9.7 +/- 3.9 mV). There was a good correlation between the diameter of the coronary sinus as assessed by quantitative coronary angiography at the level of the middle and proximal rings and atrial pacing threshold (r = 0.92, P < 0.0001). Thus, single lead left atrial- and left ventricular-based pacing is feasible although further development is necessary to increase the success rate for stable stimulation at both sites.