Long‐Term Nonoutflow Septal Versus Apical Right Ventricular Pacing: Relation to Left Ventricular Dyssynchrony

Background: Right ventricular (RV) apical pacing deteriorates left ventricular (LV) function. RV nonoutflow (low) septal pacing may better preserve ventricular performance, but this has not been systematically tested. Our aim was to assess (1) whether long‐term RV lower septal pacing is superior to RV apical pacing regarding LV volumes and ejection fraction (EF), and (2) if the changes in LV dyssynchrony imposed by pacing are related to the long‐term changes in LV volumes and EF. Methods: In thirty‐six patients with atrioventricular (AV) block, a dual‐chamber pacemaker was implanted. The ventricular electrode was placed either at the apex or at the lower septum, in a randomized sequence. Twenty‐four to 48 hours following implantation, we measured LV volumes, EF, and LV dyssynchrony (by tissue Doppler imaging), both with and without pacing. Patients were reassessed echocardiographically after 12 months. Results: Lower septal pacing induced a more synchronized pattern of LV contraction changes (P < 0.05). Following 12 months, differences were observed between groups regarding LV volumes and EF. EF increased within the septal group (from 52 ± 3.3% to 59 ± 3.0%, P < 0.05). A significant inverse relation was documented between changes in LV dyssynchrony and changes in EF (r =?0.64, P < 0.05). Conclusions: In patients with AV block, RV nonoutflow septal pacing represents an attractive alternative, since it preserves better and may even improve LV volumes and EF. Late changes in EF are associated with the changes in LV dyssynchrony imposed by pacing.     

SUPEROVULATION INDUCTION IN WOMEN SUPPRESSES LUTEINIZING HORMONE SECRETION AT THE PITUITARY LEVEL

In superovulated women the pituitary response to GnRH is markedly attenuated by an unspecified ovarian factor(s). To examine the site of attenuation, the response of the pituitary to GnRH was investigated in five normally ovulating women during the late follicular phase of 3 cycles, i.e. a spontaneous (control) cycle, a cycle treated with 'pure' FSH, and a cycle treated with a combination of 'pure' FSH and pulsatile GnRH, via a pump (15 micrograms/pulse). The oestradiol levels (mean +/- SEM) at the time of the GnRH challenge were respectively 646 +/- 35, 1692 +/- 282 and 5976 +/- 1129 pmol/l. The size of the leading follicle was similar in all groups. Serum LH levels during treatment with FSH decreased significantly, while during treatment with FSH plus GnRH they increased initially and then decreased progressively. The response of pituitary LH to GnRH was significantly attenuated during treatment with FSH and FSH plus GnRH, as compared to the spontaneous cycles, but was not abolished. The attenuation was significantly greater in the FSH plus GnRH cycles (94%) than in the FSH cycles (59%). We conclude that in superovulated cycles, the attenuation of the pituitary response to GnRH increases with the degree of ovarian hyperstimulation. It is suggested that the responsible unspecified ovarian factor(s) exerts its effects at least at the pituitary level.