No abstract

Background-Phase 2 reentry caused by heterogeneous loss of the transient outward potassium current (I to )-mediated epicardial action potential (AP) dome can produce a closely coupled R-on-T extrasystole leading to ventricular fibrillation (VF) under conditions of ST-segment elevation unrelated to ischemia. The present study examined the role of phase 2 reentry in the initiation of VF during early myocardial ischemia. Methods and Results-Regional myocardial ischemia was produced in an isolated, arterially perfused canine right ventricular wedge preparation. Transmembrane APs from 2 epicardial sites at each side of the ischemic border were simultaneously recorded together with measurements of extracellular potassium concentration ([K ϩ ] o ) and a transmural ECG. Loss of the I to -mediated epicardial AP dome in the ischemic zone but not in the perfused tissue resulted in phase 2 reentry and associated R-on-T extrasystoles capable of initiating VF in 7 of 15 preparations during the first 3 to 9 minutes of myocardial ischemia, with marked ST-segment elevation and [K ϩ ] o accumulation. The I to and phase 1 magnitude of epicardium contributed importantly to the onset of VF. Phase 1 magnitude and I to density at ϩ30 mV in the group with phase 2 reentry-related R-on-T extrasystoles were 32.2Ϯ1.3 mV and 30.3Ϯ0.5 pA/pF (nϭ7), respectively, significantly greater than those (24.0Ϯ1.8 mV and 23.2Ϯ1.0 pA/pF) in the group without the extrasystoles (nϭ8, PϽ0.01). Conclusions-Acute regional myocardial ischemia results in markedly heterogeneous loss of I to -mediated epicardial AP domes across the ischemic border, leading to phase 2 reentry. Phase 2 reentry can in turn produce an R-on-T extrasystole capable of initiating VF.

The New England Elders Dental Study (NEEDS) reports the prevalence, extent and severity of oral diseases and conditions among a representative sample of community-dwelling elders age 70 and older residing throughout the six New England states. In-home, full-mouth examinations were conducted by four calibrated dentists who used National Institute of Dental Research (NIDR) standardized disease measures plus additional diagnostic codes on all tooth surfaces. Only 37.6% of elders age 70 and older were edentulous, while dentate elders had a mean number of teeth per person ranging from 21.5 to 17.9 across age and gender cohorts. The prevalence of untreated coronal decay in elders with teeth was 28% in female elders and 34% in male elders. More than 90% of all elders with teeth had coronal fillings and 22% exhibited untreated root caries. Periodontal destruction was substantial, with 66% of dentate elders exhibiting moderate periodontal pockets (4-6 mm) while 21% exhibited severe periodontal pocketing (> 6 mm). Comparisons with national surveys suggest that periodontal disease prevalence and severity appear to have been underestimated in previous national studies of the elderly. Because of aging and tooth retention trends, the periodontal disease problem of the elderly may be increasing in the face of dentists' tendency to underdiagnose the periodontal diseases, legal constraints on dental hygienists to independently treat them, and inadequate funding for conservative nonsurgical therapies.