Isthmus Dependent Atrial Flutter Cycle Length Correlates with Right Atrial Cross-Sectional Area

Background: Right atrial flutter cycle length can prolong in the presence of antiarrhythmic drug therapy. We hypothesized that the cycle length of right atrial isthmus dependent flutter would correlate with right atrial cross-sectional area measurements. Methods: 60 patients who underwent ablation for electrophysiologically proven isthmus dependent right atrial flutter, who were not on Class I or Class III antiarrhythmic drugs and had recent 2-dimensional echocardiographic data comprised the study group. Right atrial length and width were measured in the apical four chamber view. Cross-sectional area was estimated by multiplying the length and width. 35 patients had an atrial flutter rate ≥250 bpm (Normal Flutter Group) and 25 patients had an atrial flutter rate < 250 bpm (Slow Flutter Group). Results: Mean atrial flutter rate was 283 bpm in the normal flutter group and 227 bpm in the slow flutter group. Mean atrial flutter cycle length was 213 ms in the Normal Flutter Group and 265 ms in the Slow Flutter Group (p<0.0001). Mean right atrial cross sectional area was 1845 mm2 in the Normal Flutter group and 2378 mm2 in the Slow Flutter Group, (p< 0.0001). Using linear regression, CSA was a significant predictor of cycle length (β =0.014 p = 0.0045). For every 1 mm2 increase in cross-sectional area, cycle length is 0.014 ms longer.Conclusion: In the absence of antiarrhythmic medications, right atrial cross sectional area enlargement correlates with atrial flutter cycle length. These findings provide further evidence that historical rate-related definitions of typical isthmus dependent right atrial are not mechanistically valid

Improved detection of substantia nigra pathology in Alzheimer\u27s disease

The role of substantia nigra pathology in Alzheimer\u27s disease (AD) is uncertain. Detection of pathology may be obscured by intraneuronal neuromelanin and influenced by stains. We determined methods for optimal visualization of nigral pathology in 45 cases of AD. For detection of Lewy bodies (LBs), we compared ubiquitin and alpha-synuclein immunostains to hematoxylin and eosin (H&E). For neurofibrillary tangles (NFTs) and neuropil threads (NTs), we compared Gallyas silver and paired helical filament (PHF) immunostains, after bleaching of melanin, to modified Bielschowsky, Gallyas, and PHF alone. The number of LB cases was not different using the three stains. However, more LBs per section were detected using alpha-synuclein (z=4.88, p\u3c0.001). Twice the number of cases exhibited NFT (z=8.21; p\u3c0.001) and the mean NFT number per section was 2.8-5.2-fold greater, using Gallyas and PHF after bleaching compared to without bleaching (chi(2)=142.17; p\u3c0.001). More NTs (z=6.54; p\u3c0.001) were observed with PHF and Gallyas after bleaching. With optimal methods, we found LBs in 27%, NFTs in 89%, and NTs in all 45 AD cases. We show that detection of nigra pathology is influenced by histological method. Clinicopathological studies using these methods are needed to determine the role of nigral pathology in AD