Shen, W K

Abstract Funding Acknowledgements Type of funding sources: Private hospital(s). Main funding source(s): Mayo Clinic Background/Introduction Syncope is a common presentation in heart failure (HF) patients. However, the associations between syncope and prognosis in HF patients with the cardiac implantable electronic device (CIED) have not been demonstrated. It is unclear whether syncope increases all-cause mortality in HF patients with CIED. Purpose We aimed to examine the association between syncope and all-cause mortality in the largest cohort of HF with reduced ejection fraction (HFrEF), mid-ranged ejection fraction (HFmEF), and preserved ejection fraction (HFpEF) patients with and without CIED. Methods A retrospective cohort of patients with HF and syncope at our hospital between 2010 and 2015 were identified, and 1:1 propensity was matched with a control group of HF patients without syncope. A chart review was conducted. The multivariate Cox regression model was applied to estimate the association between syncope and the all-cause mortality endpoint. Results 3,449 HF patients were diagnosed with syncope (mean age, 72.8±14.5 years; 41.5% women), and the propensity-matched control HF patients without syncope (n=3,449) aged 72.8±14.3 years, and 42.5% women were selected. Cardiac implantable electronic devices were implanted more in HF patients with syncope (32.5% versus 13.7%, p<0.001). Implantable cardioverter defibrillators were implanted more in HF patients with syncope (15.6% versus 8.3%, p<0.001) as well as pacemakers (16.9% versus 7.5%, p<0.001) and cardiac resynchronization therapy devices (6.9% versus 4.8%, p=0.015). Among HF patients with CIED, syncope significantly increased the risk of all-cause mortality in HFrEF patients (hazard ratio [HR]=1.479, 95% confidence interval [CI]: 1.197-1.828, p<0.001) but not in HFpEF (HR=0.980, 95%CI: 0.793-1.210, p=0.849)(Figure 1). Syncope also tended to increase the risk of all-cause mortality in HFmEF patients with CIED but was not significant (HR=1.193, 95%CI: 0.762-1.865, p=0.762)(Figure 1). Among HF patients without CIED, syncope did not increase the risk of all-cause mortality in HFrEF (HR=0.923, 95%CI: 0.806-1.057, p=0.247), HFmEF (HR=1.074, 95%CI: 0.848-1.360, p=0.554), or HFpEF (HR=0.964, 95%CI: 0.883-1.052, p=0.406). Conclusions Syncope significantly increased the risk of all-cause mortality in HFrEF patients but not in HFmEF or HFpEF patients with CIED. The association of syncope and increased mortality in HFrEF patients with CIED suggests that syncope may be a marker and a factor of mortality and warrants further investigation.

Effects of ER-001533 (ER), a newly synthesized vasorelaxant, on the membrane currents were examined in single ventricular cells of guinea pigs. The patch-clamp technique was used in the "whole-cell" and "inside-out" patch configurations. In the whole-cell clamp condition, ER induced a time-independent K(+)-dominant current, which was inhibited by glibenclamide (1-3 microM), suggesting that ER activated the cardiac ATP-sensitive K+ channel (KATP). To elucidate the mechanism of ER-mediated KATP channel activation, the drug was applied to the inside-out patches before and after channel "run-down." Since nucleotide diphosphates could induce the channel openings after complete run-down, effects of the drug on the nucleotide diphosphate-induced channel openings were also examined. Before run-down, ER activated the KATP channel only in the presence of ATP. ER shifted the relation between [ATP]i and the channel activity to the right in a concentration-dependent fashion without a significant alteration of the slope. After channel run-down, ER did not affect the channel openings either in the absence or in the presence of UDP. However, ER could relieve the ATP-gamma-S inhibition of the UDP-induced channel openings. Thus, we conclude that ER antagonizes the inhibitory effect of ATP on the KATP channel in a competitive manner, thereby enhancing the channel openings.

Vasorelaxant agents such as pinacidil, lemakalim, and nicorandil, known as K+ channel openers, can activate the ATP-sensitive K+ channel (KATP channel) in cardiac myocytes. The aim of this study was to elucidate the molecular mechanisms underlying the K+ channel opener-mediated cardiac KATP channel activation by using the inside-out patch-clamp technique in guinea pig ventricular myocytes. Effects of pinacidil, lemakalim, and nicorandil on the KATP channel were examined both before and after channel "run-down". Since nucleotide diphosphates (NDPs) could activate the channel after complete run-down, effects of the drugs on the NDP-induced channel openings were also examined. We made the following observations: 1) Pinacidil (10-100 microM) and lemakalim (300 microM) activated the KATP channel before run-down and after run-down when NDPs were present. 2) Nicorandil (30 microM-1 mM) activated the KATP channel only in the presence of NDPs regardless of the condition of the channel with respect to run-down. 3) None of these K+ channel openers activated the channel after run-down in the absence of NDPs. These observations suggest that NDP binding is essential for nicorandil-mediated activation of the KATP channel and indicate that the molecular mechanisms underlying nicorandil activation are distinct from those of pinacidil and lemakalim activation of the KATP channel. We discuss the possible interactions between the drugs and the KATP channel based on a functional channel model.

The outlook for patients with double-outlet right ventricle has improved since the development of corrective operations. Late arrhythmic deaths after successful procedures have been reported; however, the magnitude remains unknown. This study was undertaken to identify the magnitude of late sudden death and the significant factors associated with it. From 1965 through 1985, 118 patients underwent corrective operation for double-outlet right ventricle; of these, 23 died in the hospital and six were lost to follow-up. The 89 remaining patients (52 male and 37 female) made up the study population. Their mean age (+/- SD) was 10.3 +/- 7.8 years at the time of repair. The mean duration of follow-up was 82 months. Of the 22 late deaths, 16 (73%) were sudden. Eight (50%) of the sudden deaths occurred within 1 year of operation. Cox proportional hazards multivariate analysis revealed the following significant risk factors for late sudden death: older age at the time of operation, perioperative or postoperative ventricular tachyarrhythmias, and third-degree atrioventricular block. Factors not associated with late sudden death included year of operation, sex, type and number of associated cardiac anomalies, preoperative functional class, previous palliative procedures, surgical technique, perioperative or postoperative single premature ventricular contractions, and postoperative left or right bundle branch block with or without fascicular block. We conclude that the incidence of late sudden death after successful surgical repair of double-outlet right ventricle is very high. Complete corrective operation at an early age and aggressive diagnosis and treatment of arrhythmias and conduction defects after operation are warranted.