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Richards MA, Clarke JD, Saravanan P, Voigt N, Dobrev D, Eisner DA, Trafford AW, Dibb KM. Transverse tubules are a common feature in large mammalian atrial myocytes including human. Am J Physiol Heart Circ Physiol 301: H1996 -H2005, 2011. First published August 12, 2011; doi:10.1152 doi:10. /ajpheart.00284.2011 tubules are surface membrane invaginations that are present in all mammalian cardiac ventricular cells. The apposition of L-type Ca 2ϩ channels on t tubules with the sarcoplasmic reticulum (SR) constitutes a "calcium release unit" and allows close coupling of excitation to the rise in systolic Ca 2ϩ . T tubules are virtually absent in the atria of small mammals, and therefore Ca 2ϩ release from the SR occurs initially at the periphery of the cell and then propagates into the interior. Recent work has, however, shown the occurrence of t tubules in atrial myocytes from sheep. As in the ventricle, Ca 2ϩ release in these cells occurs simultaneously in central and peripheral regions. T tubules in both the atria and the ventricle are lost in disease, contributing to cellular dysfunction. The aim of this study was to determine if the occurrence of t tubules in the atrium is restricted to sheep or is a more general property of larger mammals including humans. In atrial tissue sections from human, horse, cow, and sheep, membranes were labeled using wheat germ agglutinin. As previously shown in sheep, extensive t-tubule networks were present in horse, cow, and human atrial myocytes. Analysis shows half the volume of the cell lies within 0.64 Ϯ 0.03, 0.77 Ϯ 0.03, 0.84 Ϯ 0.03, and 1.56 Ϯ 0.19 m of t-tubule membrane in horse, cow, sheep, and human atrial myocytes, respectively. The presence of t tubules in the human atria may play an important role in determining the spatio-temporal properties of the systolic Ca 2ϩ transient and how this is perturbed in disease.atria; t-tubule heart T TUBULES ARE INVAGINATIONS of the surface membrane that penetrate deep within the cell. They occur at the z-line and are present in ventricular myocytes of all mammalian species studied to date. Many of the proteins involved in excitation contraction coupling are located on, or in close proximity to, the t-tubule membrane (16). In cardiac muscle, excitation contraction coupling is initiated by opening of L-type Ca 2ϩ channels and subsequent Ca 2ϩ entry (I Ca,L ) triggering release of Ca 2ϩ from the intracellular Ca 2ϩ store, the sarcoplasmic reticulum (SR). T tubules allow close coupling of I Ca,L to ryanodine receptors (RyRs) on the SR membrane resulting in rapid triggered Ca 2ϩ release in the cell interior upon electrical excitation. Thus, in ventricular cells, which have a regular t-tubule network penetrating the entire cell, the rise in intracellular Ca 2ϩ responsible for contraction is both rapid and synchronous throughout the entire cell. Chemically induced t-tubule removal with formamide results in this initial rise in intracellular Ca 2ϩ concentration being localized to the periphery and then propagating to the cell center (46).To ...

Background-Omega-3 polyunsaturated fatty acids (n-3 PUFA) have been reported to reduce the risk of sudden cardiac death presumed to be due to fatal ventricular arrhythmias, but their effect on atrial arrhythmias is unclear. Methods and Results-Patients (nϭ108) undergoing coronary artery bypass graft surgery were randomly assigned to receive 2 g/d n-3 PUFA or placebo (olive oil) for at least 5 days before surgery (median, 16 days; range, 12 to 21 days). Phospholipid n-3 PUFA were measured in serum at study entry and at surgery and in right atrial appendage tissue at surgery. Echocardiography was used to assess left ventricular function and left atrial dimensions. Postoperative continuous ECG monitoring (Lifecard CF) for 5 days or until discharge, if earlier, was performed with a daily 12-lead ECG and clinical review if patients remained in the hospital beyond 5 days. Lifecard recordings were analyzed for episodes of atrial fibrillation (AF) Ն30 seconds (primary outcome). Clinical AF, AF burden (% time in AF), hospital stay, and intensive care/high dependency care stay were measured as secondary outcomes. One hundred three patients completed the study (51 in the placebo group and 52 in the n-3 PUFA group). There were no clinically relevant differences in baseline characteristics between groups. n-3 PUFA levels were higher in serum and right atrial tissue in the active treatment group. There was no significant difference between groups in the primary outcome of AF (95% confidence

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There is increasing recognition that migraine with aura may be associated with intra-cardiac shunting because of a patent foramen ovale. Radio-frequency ablation to treat cardiac arrhythmias is an increasingly popular means of treating cardiac arrhythmias. Trans-septal puncture is routinely performed to gain access to the left atrium in order to ablate arrhythmias originating in the left heart. We report several cases of migraine triggered acutely by trans-septal puncture at our center.

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