Oligodendrocytes of adult rodents express three different connexins: connexin29 (Cx29), Cx32, and Cx47. In this study, we show that Cx29 is localized to the inner membrane of small myelin sheaths, whereas Cx32 is localized on the outer membrane of large myelin sheaths; Cx29 does not colocalize with Cx32 in gap junction plaques. All oligodendrocytes appear to express Cx47, which is largely restricted to their perikarya. Cx32 and Cx47 are colocalized in many gap junction plaques on oligodendrocyte somata, particularly in gray matter. Cx45 is detected in the cerebral vasculature, but not in oligodendrocytes or myelin sheaths. This diversity of connexins in oligodendrocytes (in different populations of cells and in different subcellular compartments) likely reflects functional differences between these connexins and perhaps the oligodendrocytes themselves.

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Background— The prognosis for patients experiencing ventricular arrhythmias (VAs) while on continuous flow left ventricular assist device (LVAD) support has not been well elucidated. Accordingly, the role of implantable cardioverter-defibrillators (ICDs) in this patient population remains undefined. Methods and Results— Records of 106 consecutive patients undergoing implantation of the HeartMate II LVAD at a single center were reviewed. For patients surviving >30 days postimplant (98 patients), the impact of VAs and ICDs on survival was analyzed. Mean age was 56.6±11.4 years, 82.1% were male, 42.5% had an ischemic cardiomyopathy, 87.7% were bridge to transplantation, and median length of support was 217 days. Twenty-one (19.8%) patients died, 60 (56.6%) survived to transplantation, and 25 patients (23.6%) reached the end of study, had the LVAD explanted, or were lost to follow-up. Post-LVAD VAs occurred in 37 patients (34.9%) but were not associated with increased mortality (hazard ratio, 0.58 [0.18–1.90]). Sixty-two (63.3%) patients had an active ICD, and 36 (36.7%) patients had no ICD or an inactivated ICD post-LVAD. Patients with an ICD were more likely to be INTERMACS (Interagency Registry for Mechanically Assisted Circulatory Support) level 3 or 4 at the time of implant (54.8% versus 33.3%; P =0.04). An appropriate shock was delivered in 27.3% of patients, but the presence of an active ICD was not associated with improved survival (hazard ratio, 1.12 [0.37–3.35]). Conclusions— VAs are common in patients with continuous flow LVADs. Although some episodes may be clinically significant, VAs are not associated with a worse prognosis, and concomitant ICDs in these patients may not reduce mortality.