Introduction Cardiac resynchronisation therapy (CRT) usually involves placing the left ventricular (LV) pacing lead in the postero-lateral or lateral region of the LV epicardial surface as this is thought likely to re-coordinate myocardial contraction most effectively. The LV lead is standardly placed in a position with the best pacing parameters and satisfactory stability. It is not known, however, whether there is a significant difference in haemodynamic response to LV pacing in different regions of the same coronary sinus (CS) vein. In this study we aimed to evaluate the difference in acute haemodynamic response to pacing along individual branches of the CS.
Methods 16 patients underwent an acute haemodynamic study during their CRT-defibrillator implant. We used a high fidelity pressure wire to assess the acute haemodynamic response (AHR) to pacing in different branches of the coronary sinus. We used a novel quadripolar lead (Quartet, St Jude Medical, Sylmar, California, USA) that has four poles on the LV lead―distal tip and 3 ring electrodes. The 3 ring electrodes are spaced 20 mm, 30 mm and 47 mm from the distal tip electrode and the four poles allow bipolar pacing between them. It was thus possible for us to test pacing parameters and AHR along a significant proportion of a CS branch without having to reposition the LV lead.
Results DDDLV pacing was attempted in as many different CS branches as possible in each patient (total 56 different positions used). The mean overall percentage difference in AHR (measured by change in +dP/dt compared to baseline AAI pacing or VVI pacing in AF patients) between an individual CS branch bipole with the lowest +dP/dt and that with the highest was 6.6±5.6%. Much larger differences in change in +dP/dt were seen, however, between different branches of the CS in the same patient with a mean difference in change in +dP/dt in the best CS vein compared to the worst CS vein of 16.7±6.3%. Although the difference in AHR seen between different bipoles within the same vein were not large, we did find that in some cases no pacing capture was found with one bipole but was found with another. Furthermore, differences in whether phrenic nerve stimulation (PNS) occurred were seen when using different LV lead bipoles within the same branch of the CS.
Conclusion Our data suggest that only a small difference in AHR is seen when pacing along the same branch of the CS compared to pacing within different branches of the CS within the same patient. This means that although the site of LV lead placement is important, a proximal or distal position within a CS branch is much less important than choosing the right branch in terms of acute haemodynamic response. A choice of bipoles on the LV lead may mean, however, that problems with capture thresholds or PNS can be overcome without the need to reposition the LV lead.
- haemodynamic response
- quadripolar lead