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Competing Interests: Disclosures The authors have no conflicts of interest to disclose.

Background: Predictors of torsades de pointes (TdP) in bradyarrhythmia-induced acquired long QT syndrome are not well defined., Objective: The purpose of this study was to search for electrocardiographic (ECG) TdP predictors in patients with acquired atrioventricular block (AVB) and QT prolongation., Methods: We analyzed 12-lead ECGs from 20 patients (15 females, age 65.9 ± 15.6 years) with TdP episodes from among 898 AVB patients (2.2%) in 3 tertiary hospitals. The ECG repolarization parameters in TdP patients were compared with those of 80 age- and sex-matched control AVB patients with no TdP episodes., Results: TdP was initiated by premature ventricular complexes with a long-short sequence of activation. The average cycle length of the long sequence was 1289.9 ± 228.9 ms and was 2.3 ± 0.6 times longer than the cycle length of the short sequence. TdP patients had a significantly longer mean QT interval (716.4 ± 98.9 ms vs 523.2 ± 91.3 ms, P = .001), mean T peak to end interval (334.2 ± 59.1 ms vs 144.0 ± 73.7 ms, P = .001) and a higher T peak to end interval/QT ratio (0.49 ± 0.09 vs 0.27 ± 0.11, P = .001) compared with non-TdP controls. TdP patients showed a higher prevalence of notched T waves in which T2 was at least 3 mm taller than T1 (45.0% vs 1.3%, P = .001), triphasic T waves (30.0% vs 1.3%, P = .001), reversed asymmetry (20.0% vs 0%, P = .001), and T-wave alternans (35.0% vs 0%, P = .001). An algorithm combining these morphologic parameters was able to differentiate TdP patients from non-TdP patients with high sensitivity (85.0%) and specificity (97.5%)., Conclusion: An algorithm combining specific T-wave morphologies was useful for identifying patients with AVB who are at risk for developing TdP., (Copyright © 2015 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: The relationship between cardiac autonomic nerve activity and blood pressure (BP) changes in ambulatory dogs is unclear., Objective: The purpose of this study was to test the hypotheses that simultaneous termination of stellate ganglion nerve activity (SGNA) and vagal nerve activity (VNA) predisposes to spontaneous orthostatic hypotension and that specific β₂-adrenoceptor blockade prevents the hypotensive episodes., Methods: We used a radiotransmitter to record SGNA, VNA, and BP in eight ambulatory dogs. Video imaging was used to document postural changes., Results: Of these eight dogs, five showed simultaneous sympathovagal discharges in which the minute-by-minute integrated SGNA correlated with integrated VNA in a linear pattern (group 1). In these dogs, abrupt termination of simultaneous SGNA-VNA at the time of postural changes (as documented by video imaging) was followed by abrupt (>20 mm Hg over four beats) drops in BP. Dogs without simultaneous on/off firing (group 2) did not have drastic drops in pressure. ICI-118,551 (ICI, a specific β₂-blocker) infused at 3 µg/kg/h for 7 days significantly increased BP from 126 mm Hg (95% confidence interval 118-133) to 133 mm Hg (95% confidence interval 125-141; P = .0001). The duration of hypotension (mean systolic BP <100 mm Hg) during baseline accounted for 7.1% of the recording. The percentage was reduced by ICI to 1.3% (P = .01)., Conclusion: Abrupt simultaneous termination of SGNA-VNA was observed at the time of orthostatic hypotension in ambulatory dogs. Selective β₂-adrenoceptor blockade increased BP and reduced the duration of hypotension in this model., (© 2014 Heart Rhythm Society Published by Heart Rhythm Society All rights reserved.)

Background: Cervical vagal nerve (CVN) stimulation may improve left ventricular ejection fraction in patients with heart failure., Objectives: To test the hypothesis that sympathetic structures are present in the CVN and to describe the location and quantitate these sympathetic components of the CVN., Methods: We performed immunohistochemical studies of the CVN from 11 normal dogs and simultaneously recorded stellate ganglion nerve activity, left thoracic vagal nerve activity, and subcutaneous electrocardiogram in 2 additional dogs., Results: A total of 28 individual nerve bundles were present in the CVNs of the first 11 dogs, with an average of 1.87±1.06 per dog. All CVNs contain tyrosine hydroxylase-positive (sympathetic) nerves, with a total cross-sectional area of 0.97±0.38 mm(2). The sympathetic nerves were nonmyelinated, typically located at the periphery of the nerve bundles and occupied 0.03%-2.80% of the CVN cross-sectional area. Cholineacetyltransferase-positive nerve fibers occupied 12.90%-42.86% of the CVN cross-sectional areas. Ten of 11 CVNs showed tyrosine hydroxylase and cholineacetyltransferase colocalization. In 2 dogs with nerve recordings, we documented heart rate acceleration during spontaneous vagal nerve activity in the absence of stellate ganglion nerve activity., Conclusions: Sympathetic nerve fibers are invariably present in the CVNs of normal dogs and occupy in average up to 2.8% of the cross-sectional area. Because sympathetic nerve fibers are present in the periphery of the CVNs, they may be susceptible to activation by electrical stimulation. Spontaneous activation of the sympathetic component of the vagal nerve may accelerate the heart rate., (Copyright © 2013 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Na channel blockers are effective in suppressing delayed afterdepolarizations (DADs) in isolated Purkinje fibers. However, in isolated mouse ventricular myocytes lacking calsequestrin, only those Na channel blockers that also inhibit type 2 ryanodine receptor channels were effective against spontaneous Ca elevation (SCaE) and DADs., Objective: To test the hypothesis that combined Na channel and type 2 ryanodine receptor channel blocker ((R)-propafenone) is more effective than a Na channel blocker (lidocaine) in suppressing SCaE and DADs in the intact rabbit ventricles., Methods: We compared (R)-propafenone (3 μmol/L) with lidocaine (50 μmol/L) on SCaE and DADs by using epicardial optical mapping of intracellular calcium (Ca(i)) and membrane voltage in Langendorff-perfused rabbit hearts. SCaE and DADs were induced by rapid pacing trains and isoproterenol (0.3 μmol/L) infusion. One arbitrary unit is equivalent to the Ca transient amplitude of paced beats., Results: SCaEs were observed at the cessation of rapid pacing in all hearts at baseline. (R)-Propafenone nearly completely inhibited DADs and SCaE (0.04 arbitrary units [95% confidence interval 0.02-0.06] vs 0.23 arbitrary units [95% confidence interval 0.18-0.28] at baseline; n = 6 hearts; P <.001). Lidocaine also significantly reduced the SCaE but was significantly (P <.05) less effective than (R)-propafenone. Both drugs increased the rise time of action potential upstroke and reduced conduction velocity to a similar extent, suggesting a significant inhibition of I(Na)., Conclusions: Both Na channel blockers significantly reduced tachycardia-induced SCaEs in the rabbit ventricles, but (R)-propafenone was significantly more effective than lidocaine. These data suggest that type 2 ryanodine receptor inhibition potentiates the activity of Na channel blockers against SCaE and DADs in the intact hearts., (Copyright © 2012 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Meta-analysis of randomized trials showed superior efficacy and similar safety of drug-eluting stent over bare-metal stent in acute ST-elevation myocardial infarction (STEMI) patients. However, long-term relative outcomes of sirolimus- (SES) vs. paclitaxel-eluting stent (PES) have not been fully evaluated in randomized studies. This study compared long-term safety and efficacy of these two stents in STEMI., Methods: A total of 308 STEMI patients were randomly treated with SES (n = 154) or PES (n = 154). Three-year clinical outcomes were assessed. Primary outcome of interest was incidence of major adverse cardiac events (MACE) including death, myocardial infarction (MI), stent thrombosis or target vessel revascularization (TVR). Secondary outcome of interest was occurrence of very late stent thrombosis., Results: Both groups had similar baseline characteristics. During follow-up, there was no difference between the two groups in terms of death (6.5% for SES and 10.4% for PES, p = 0.22), MI (2.6% vs. 3.9%, p = 0.75), stent thrombosis (1.9% vs. 3.2%, p = 0.72), TVR (3.9% vs. 8.4%, p = 0.15) and MACE (12.3% vs. 18.8%, p = 0.12). Eight patients in overall population had stent thrombosis: definite 3, probable 1, and possible 4. Cumulative incidence of stent thrombosis was gradually increased; 0.6% at 30 days, 0.6% at 1 year, 1.6% at 2 years, and 2.6% at 3 years. Very late stent thrombosis, definite or probable, occurred in 0.6% for both., Conclusion: Among non-selected STEMI patients who underwent primary angioplasty, both SES and PES might be safe and SES showed similar three-year clinical outcomes compared to PES., (Copyright © 2009 Elsevier Ireland Ltd. All rights reserved.)

Objectives: We compared 4-year efficacy and safety of sirolimus-eluting stents (SES) and paclitaxel-eluting stents (PES) in patients with diabetes mellitus (DM)., Background: Four-year comparison of SES with PES in diabetic patients has not been evaluated in a randomized manner., Methods: This prospective, multicenter, randomized study compared SES (n = 200) and PES (n = 200) implantation in diabetic patients. We evaluated 4-year major adverse cardiac events (MACE) including death, myocardial infarction (MI), and target lesion revascularization (TLR)., Results: The 2 groups had similar baseline characteristics. At 2 years, TLR (3.5% vs. 11.0%, log-rank, p < 0.01) and MACE (3.5% vs. 12.5%, log-rank, p < 0.01) were significantly lower in SES versus PES group with no difference of death or MI. At 4 years there were no differences in death (3.0% vs. 5.0%, p = 0.45) or MI (1.5% vs. 1.0%, p = 0.99) between SES and PES group. The TLR (7.5% vs. 12.0%, log-rank, p = 0.10) and MACE (11.0% vs. 16.0%, log-rank, p = 0.10) were statistically not different between SES and PES group. At multivariate Cox regression, post-procedural minimal lumen diameter (hazard ratio [HR]: 0.44, 95% confidence interval [CI]: 0.24 to 0.81, p < 0.01), hypercholesterolemia (HR: 2.21, 95% CI: 1.29 to 3.79, p < 0.01), and use of intravascular ultrasound (HR: 0.51, 95% CI: 0.26 to 0.99, p = 0.049) were independent predictors of 4-year MACE., Conclusions: Superiority of SES over PES during 2 years was attenuated between 2 years and 4 years in diabetic patients. Use of intravascular ultrasound and larger post-procedural minimal lumen diameter were independent predictors of the improved long-term clinical outcomes., (Copyright © 2011 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)