The use of the automated external defibrillator aboard commercial aircraft is effective, with an excellent rate of survival to discharge from the hospital after conversion of ventricular fibrillation. There are not likely to be complications when the device is used as a monitor in the absence of ventricular fibrillation.

Mate choice is considered an important influence in the evolution of mating signals and other sexual traits, and-since divergence in sexual traits causes reproductive isolation-it can be an agent of population divergence. The importance of mate choice in signal evolution can be evaluated by comparing male signal traits with female preference functions, taking into account the shape and strength of preferences. Specifically, when preferences are closed (favouring intermediate values), there should be a correlation between the preferred values and the trait means, and stronger preferences should be associated with greater preference-signal correspondence and lower signal variability. When preferences are open (favouring extreme values), signal traits are not only expected to be more variable, but should also be shifted towards the preferred values. We tested the role of female preferences in signal evolution in the Enchenopa binotata species complex of treehoppers, a clade of plant-feeding insects hypothesized to have speciated in sympatry. We found the expected relationship between signals and preferences, implicating mate choice as an agent of signal evolution. Because differences in sexual communication systems lead to reproductive isolation, the factors that promote divergence in female preferences-and, consequently, in male signals-may have an important role in the process of speciation.

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Background-Although there have been few studies in which the hemodynamic effects of right ventricular (RV) and left ventricular (LV) pacing were compared with those of biventricular (BV) pacing, the autonomic changes during these different pacing modes remain unknown. We hypothesized that BV pacing results in improved hemodynamics and a decrease in sympathetic nerve activity (SNA) compared with single-site pacing. Methods and Results-Thirteen men with a mean ejection fraction of 0.28Ϯ0.7 were enrolled in the study. Arterial blood pressure (BP), central venous pressure (CVP), and SNA were recorded during 3 minutes of right atrial (RA)-RV, RA-LV, and RA-BV pacing at a rate 10 beats faster than sinus rhythm. BP was greater during LV (151Ϯ7/ 85Ϯ3 mm Hg) and BV (151Ϯ6/85Ϯ3 mm Hg) pacing than during RV pacing (146Ϯ7/82Ϯ3 mm Hg) (PϽ0.05). There were no differences in CVP among all pacing modes (Pϭ0.27). SNA was significantly less (PϽ0.02) during both LV (606Ϯ35 U) and BV (582Ϯ41 U) pacing compared with RV pacing (685Ϯ32 U) (PϽ0.02). Although not statistically significant (Pϭ0.08 to 0.14), there was a trend for patients with a narrow QRS to have a lower mean BP and higher SNA during LV pacing than during BV pacing (rϭ0.42 to 0.49). Conclusions-LV-based pacing results in improved hemodynamics and a decrease in SNA compared with RV pacing in patients with LV dysfunction regardless of the QRS duration.

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