Heart rhythm : the official journal of the Heart Rhythm Society
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Idiopathic ventricular arrhythmias (VAs) can be rarely ablated from the noncoronary cusp (NCC) of the aorta. ⋯ NCC VAs were very rare (7%) and occurred in significantly younger patients than those among the other aortic root VAs. In a limited set of six patients, the ECG and electrophysiologic characteristics of NCC VAs were similar to those of RCC VAs but were characterized by narrower QRS duration, smaller III/II ratio, earlier ventricular activation in the HB region, and A/V ratio >1 at the successful ablation site.
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The transient receptor potential melastatin 4 (TRPM4) channel is expressed in the sinoatrial node, but its physiologic roles in this tissue with cardiac pacemaker properties remain unknown. This Ca(2+)-activated nonselective cation channel (NSCCa) induces cell depolarization at negative potentials. It is implicated in burst generation in neurons and participates in induction of ectopic beating in cardiac ventricular preparations submitted to hypoxia/reoxygenation. Accordingly, TRPM4 may participate in action potential (AP) triggering in the sinoatrial node. ⋯ These data showed that TRPM4 modulates beating rate. Pacemaker activity in the sinoatrial node results from the slow diastolic depolarization slope due to the "funny" current, Na/Ca exchange, and a Ca(2+)-activated nonselective cation current, which can be attributable in part to TRPM4 that may act against bradycardia.
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Right cervical vagus nerve stimulation (VNS) provides cardioprotective effects against acute ischemia-reperfusion injury in small animals. However, inconsistent findings have been reported. ⋯ During ischemia-reperfusion injury, both C-VNS and I-VNS provide significant cardioprotective effects compared with I-VNS + atropine. These beneficial effects were abolished by muscarinic blockade, suggesting the importance of muscarinic receptor modulation during VNS. The protective effects of VNS could be due to its protection of mitochondrial function during ischemia-reperfusion.
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Comparative safety and efficacy associated with transvenous lead extraction (TLE) of recalled and non-recalled implantable cardioverter-defibrillator (ICD) leads has not been well characterized. ⋯ In our experience, recalled ICD leads were extracted with safety and efficacy comparable to that of non-recalled ICD leads.