Effectiveness and safety of non-vitamin K antagonist oral anticoagulants in octogenarian patients with non-valvular atrial fibrillation

BACKGROUND AND OBJECTIVE

Elderly patients with atrial fibrillation (AF) are known to have a high risk of stroke and bleeding. We investigated the effectiveness and safety of non-vitamin K antagonist oral anticoagulants (NOACs) in octogenarian patients with non-valvular AF compared with warfarin.

METHODS

A total of 687 octogenarian patients with AF who were administered NOACs (n = 403) or warfarin (n = 284) for stroke prevention between 2012 and 2016 were included. Thromboembolic (TE) events (stroke or systemic embolism), major bleeding events, and all-cause death were analyzed.

RESULTS

The NOACs group (age 83.4±3.2 years, women 52.4%, CHA2DS2-VASc score 5.0±1.8) comprised 141 dabigatran, 158 rivaroxaban, and 104 apixaban users. Most patients from the NOACs group had been prescribed a reduced dose of medication (85.6%). During 14±18 months of follow-up periods, there were 19 TE events and 18 major bleeding events. Patients with NOAC showed a lower risk of TE (1.84 vs. 2.71 per 100 person-years, hazard ration [HR] 0.134, 95% confidence interval [CI] 0.038-0.479, P = 0.002), major bleeding (1.48 vs. 2.72 per 100 person-years, HR 0.110, 95% CI 0.024-0.493, P = 0.001), and all-cause death (2.57 vs. 3.50 per 100 person-years, HR 0.298, 95% CI 0.108-0.824, P = 0.020).

CONCLUSION

In octogenarian Asian patients with AF, NOACs might be associated with lower risks of thromboembolic events, major bleeding, and all-cause death than warfarin. Although most patients had received reduced doses, on-label use of NOACs was effective and safe.

Abstract TMP93: Comparative Occurrence of Ischemic Stroke with Rhythm versus Rate Control Strategy in a National Prospective Cohort of Atrial Fibrillation

Introduction: Comparative occurrence of ischemic stroke for rhythm versus rate control in patients with non-valvular atrial fibrillation (NVAF) has been still inconclusive. The aim of this study was to compare differences of ischemic stroke occurrence between the rhythm and rate control strategies in AF patients.

Methods: The CODE-AF registry prospectively enrolled 6,280 consecutive patients who were treated for NVAF at 10 tertiary referral centers in South Korea. Of these, 2,513 (40.0%) NVAF patients (age, 67±10 years; male, 61.8%) were clinically followed up for 1-year and divided into rate control 1,233 (49.0%) and rhythm control 1280 (51.0%) group.

Results: Those treated with the rhythm control group were younger, and had less proportions of underlying disease compared to those treated with the rate control strategy. After propensity score matching analysis, 1,800 of these patients was compared and analyzed between rate control and rhythm control group. Those treated with the rhythm control group were similar in the baseline characteristics including CHA 2 DS 2 -VASC score compared to those treated with the rate control strategy. The rate of oral anticoagulation, all bleeding, and hospitalization were also similarly between two groups. The incidence rate of ischemic stroke in the rhythm control group was significantly lower than rate control group (0.7 vs. 6.9 per 1000 person-years, p=0.011).

Conclusion: In this national prospective AF cohort, the rhythm control strategy demonstrated beneficial effect to lower the risk of ischemic stroke during 1-year follow-up compared to rate control strategy.

Association of metabolic syndrome and chronic kidney disease with atrial fibrillation: A nationwide population-based study in Korea

AIMS

Metabolic syndrome (MetS) and chronic kidney disease (CKD) are significant risk factors for incident atrial fibrillation (AF). Few studies have reported the synergistic effect of MetS and CKD on development of AF. We investigated the individual and synergistic effects of MetS and CKD on the risk of incident AF.

METHODS

We studied a retrospective cohort comprising 22,886,663 Koreans whose data was obtained from the national health claims database established by the Korean National Health Insurance Service between 2008 and 2013. Patients were classified into a MetS and a CKD group and followed-up until 2016 for new-onset AF. A Cox proportional hazards model assessed the independent and synergistic effect of MetS and CKD on the risk of incident AF.

RESULTS

The prevalence of MetS and CKD in these patients was 27.4% and 5.4%, respectively. During a mean follow-up of 5.4 years, AF developed in 225,529 patients (1% of the total cohort). The adjusted hazard ratio (HR) for incident AF was 1.38 (95% confidence interval [CI] 1.36-1.39) for MetS, and 1.35 (95% CI 1.34-1.37) for CKD. Patients with MetS and CKD showed a higher risk of AF (HR 1.75, 95% CI 1.73-1.78) than that observed in those without MetS and CKD.

CONCLUSIONS

The combination of MetS and CKD showed a high risk of development of AF in a large-scale nationwide cohort. Further studies are warranted to determine whether pharmacological and/or lifestyle interventions can control/manage these modifiable risk factors to reduce the risk of development of AF.

Association between adult height, myocardial infarction, heart failure, stroke and death: a Korean nationwide population-based study

Background

The association between adult height and cardiovascular (CV) events and mortality has been suggested, albeit inconsistently. We sought to discover the comprehensive relationship between height, CV-related morbidity and all-cause death according to age.

Methods

We investigated the association between adult height and myocardial infarction (MI), heart failure (HF), stroke incidence and mortality in 16 528 128 Korean patients who underwent regular health check-ups (2005-08). Height was stratified by decile according to age (20-39 years, 40-59 years and ≥60 years) and gender.

Results

During a 9-year follow-up period, 590 346 participants died and 232 093 were admitted to hospital for MI, 201 411 for HF and 267 566 for stroke. An inverse relationship between height and MI, HF, stroke and all-cause death was observed in the overall cohort analysis. The association was unchanged after adjusting for CV risk and behavioural and adulthood socioeconomic factors. Both male and female sex showed an inverse relationship with height in adulthood, CV events and mortality. Adult height showed an inverse association in all CV events and mortality, especially in the older groups (≥40 years). In a subgroup analysis of body mass index, there was an inverse relationship between height, CV events and mortality in each group.

Conclusions

Shorter height in adulthood was strongly related to an increased risk of MI, HF, stroke and all-cause death. A suitable environment and appropriate nutrition early in life could influence adult height and eventually reduce the risk of CV events and mortality.

Mortality and causes of death in patients with atrial fibrillation: A nationwide population-based study

Background

Patients with atrial fibrillation are known to have a high risk of mortality. There is a paucity of population-based studies about the impact of atrial fibrillation on the mortality risk stratified by age, sex, and detailed causes of death.

Methods

A total of 15,411 patients with atrial fibrillation from the Korean National Health Insurance Service-National Sample Cohort were enrolled, and causes of death were identified according to codes of the 10th revision of the International Classification of Diseases.

Results

From 2002 to 2013, a total of 4,479 (29%) deaths were confirmed, and the crude mortality rate for all-cause death was 63.3 per 1,000 patient-years. Patients with atrial fibrillation had a 3.7-fold increased risk of all-cause death compared with the general population. The standardized mortality ratio for all-cause death was the highest in young patients and decreased with increasing age (standardized mortality ratio 21.93, 95% confidence interval 7.60–26.26 in patients aged <20 years; standardized mortality ratio 2.77, 95% confidence interval 2.63–2.91 in patients aged ≥80 years). Women with atrial fibrillation exhibited a greater excess mortality risk than men (standardized mortality ratio 3.81, 95% confidence interval 3.65–3.98 in women; standardized mortality ratio 3.35, 95% confidence interval 3.21–3.48 in men). Cardiovascular disease was the leading cause of death (38.5%), and cerebral infarction was the most common specific disease. Patients with atrial fibrillation had an about 5 times increased risk of death due to cardiovascular disease compared with the general population.

Conclusions

Patients with atrial fibrillation had a 4 times increased risk of mortality compared with the general population. However, the impact of atrial fibrillation on mortality decreased with age and in men. Cerebral infarction was the most common cause of death, and more attention should be paid to reducing the risk of stroke.

Ankylosing spondylitis: A novel risk factor for atrial fibrillation - A nationwide population-based study

BACKGROUND

Ankylosing spondylitis (AS) is a chronic inflammatory rheumatic disease, associated with a number of cardiovascular diseases. We sought to investigate whether AS increases the risk of atrial fibrillation (AF) in a nationwide population-based study.

METHODS

A total of 14,129 patients newly diagnosed with AS (mean age 41.8 ± 15.3 years, 72% male) were recruited from the Korean National Health Insurance Service database between 2010 and 2014 and followed up for new onset AF. Age- and sex-matched non-AS subjects (1:5, n = 70,645) were selected and compared with the AS patients.

RESULTS

During a mean follow-up of 3.5 years, AF was newly diagnosed in 486 patients (114 patients of the AS group). The AS patients developed AF more frequently than the non-AS subjects (2.32 vs. 1.51 per 1000 person-years). In multivariate Cox regression analysis, AS was an independent risk factor for AF (Hazard ratio [HR] 1.28, 95% confidence interval [1.03-1.58]). The AS with tumor necrosis factor inhibitor (TNFi) therapy group showed higher risk for AF (HR 1.60 [1.02-2.39]). In younger patients of the AS group (patients <40 years old), the risk for AF was three times higher than patients at same age in the non-AS group. AS was an independent risk factor for AF in men, but not in women (HR 1.53 [1.18-1.95]; HR 1.42 [0.94-2.08], respectively).

CONCLUSIONS

AS was an independent risk factor for AF, especially in those under 40 years of age and those administered TNFi. It would be reasonable to screen for AF and stroke prevention in these high-risk patients.

Validation of Conventional Thromboembolic Risk Factors in a Korean Atrial Fibrillation Population - Suggestion for a Novel Scoring System, CHA2DS2-VAK

BACKGROUND

There is little evidence that focuses on the ethnic variability of clinical risk factors for thromboembolism (TE) in atrial fibrillation (AF). We aimed to investigate the effect of each traditional risk factor in the Korean AF population. Methods and Results: Medical records of 12,876 consecutive patients (aged >18 years) newly diagnosed and followed up with non-valvular AF from 2000 to 2013 were reviewed. TE events, including ischemic stroke and systemic embolism, were investigated for risk factor validation. Among the total of 12,876 patients, 1,390 (10.8%) had TE events. In univariate/multivariate analysis adjusting for clinical factors and antithrombotic medications, traditional risk factors included in the CHA₂DS₂-VASc scheme showed statistical significance, except for female sex, which was not a predictor of events. Additionally, chronic kidney disease (CKD; hazard ratio 1.62, P<0.001) was shown to be an independent predictor of TE events. Based on the analysis, we developed a novel stratification system, CHA₂DS₂-VAK, omitting the female sex category and adding CKD. The new scoring system showed greater discrimination in event rates between score 0 and 1 patients.

CONCLUSIONS

Female sex was not associated with TE events in a Korean non-valvular AF population. The novel CHA₂DS₂-VAK scoring system, with substitution of CKD for female sex, might be more appropriate for the Korean population.

Atrial Innervation Patterns of Intrinsic Cardiac Autonomic Nerves

BACKGROUND

Although ganglionated plexi (GPs) are important in the pathogenesis of arrhythmia, their patterns of atrial innervation have remained unclear. We investigated patterns of GP innervation to cardiac atria and the neuroanatomical interconnections among GPs in an animal model.

METHODS

Atrial innervation by GPs was evaluated in 10 mongrel dogs using a retrograde neuronal tracer (cholera toxin subunit B [CTB] conjugated with fluorescent dyes). In Experiment 1, CTB was injected into the atria. In Experiment 2, CTB was injected into the major GP, including the anterior right GP (ARGP), inferior right GP (IRGP), superior left GP (SLGP), and ligament of Marshall (LOM). After 7 days, the GPs were examined for the presence of tracer-positive neurons.

RESULTS

GPs in either right or left-side were innervating to both the same and opposite sides of the atrium. In quantitative analysis, right-sided GPs, especially ARGP, showed numerical predominance in atrial innervation. Based on the proportion of CTB-labeled ganglion in each GP, atrial innervation by GPs showed a tendency of laterality. In Experiment 2, CTB that was injected to a particular GP widely distributed in different GP. ARGP projected the largest number of innervating neurons to the IRGP, SLGP and LOM.

CONCLUSION

This study demonstrated that GPs project axons widely to both the same and opposite sides of atria. ARGP played a dominant role in atrial innervation. Furthermore, there were numerous neuroanatomical interconnections among GPs. These findings about neuronal innervation and interconnections of GPs could offer useful information for understanding intrinsic cardiac nervous system neuroanatomy.

Prognostic efficacy of platelet count in patients with nonvalvular atrial fibrillation

BACKGROUND

The prognostic efficacy of quantitative platelet activity in atrial fibrillation (AF) remains unclear.

OBJECTIVE

The purpose of this study was to evaluate the platelet count (PLT) as a prognostic indicator in patients with nonvalvular AF.

METHODS

Data on 10,978 patients with nonvalvular AF were retrieved from a prospective registry of a single medical center in Korea. Cumulative risk for stroke and bleeding events were compared between patients with normal PLT (n = 8322), mild thrombocytopenia (n = 1791), and moderate to severe thrombocytopenia (n = 865) after propensity score matching. Prediction models for stroke were derived by conventional risk factors (model 1) and by combining PLT with model 1 (model 2), and model performance was assessed by area under the receiver operator characteristics curve (AUC).

RESULTS

During the follow-up period, 7.3%, 7.0%, and 4.5% had stroke and 7.6%, 10.8%, and 17.2% had bleeding events in the normal PLT, mild, and moderate to severe thrombocytopenia groups, respectively. Compared to the normal PLT group, the moderate to severe thrombocytopenia group showed a lower risk of stroke (hazard ratio [HR] 0.57; 95% confidence interval [CI] 0.40-0.80; P = .002). A reverse relationship was found between PLT and bleeding risk (moderate to severe thrombocytopenia: HR 2.19; 95% CI 1.77-2.70; P <.001; mild thrombocytopenia: HR 1.43; 95% CI 1.18-1.73; P <.001). Compared to model 1, model 2 showed significant improvement in risk prediction (AUC 0.628 vs 0.644; P <.001).

CONCLUSION

A lower PLT was associated with a lower risk of stroke and a higher risk of bleeding events. PLT combined with conventional risk factors showed significant improvement in prediction for stroke.

Reciprocal relationship between herpes zoster and cardiovascular diseases: A nationwide population-based case-control study in Korea

Recently, herpes zoster (HZ) has been identified as a risk factor for stroke, but there have been few studies on the relationship between HZ and other cardiovascular diseases (CVD), including myocardial infarction (MI) and heart failure (HF). The purpose of this study was to investigate the risk of HZ occurrence after CVD and the occurrence of CVD after HZ. This was a retrospective case-control study based on the National Health Insurance System claims database for 20 311 patients with HZ and 13 980 patients with CVD and 1:5 age- and sex-matched control subjects for each from January 2006 to December 2013. We evaluated the reciprocal relationship between HZ and CVD including MI, ischemic stroke and HF. Severe HZ requiring hospitalization independently increased the risk of subsequent MI (hazard ratio [HR], 1.831; 95% confidence interval [CI], 1.354-2.476)], ischemic stroke (HR, 1.523; 95% CI, 1.212-1.915) and HF (HR, 2.034; 95% CI, 1.615-2.562) during the study period. Likewise, patients with an episode of MI, ischemic stroke or HF were also at increased risk of HZ hospitalization (after MI: HR, 1.625; 95% CI, 1.144-2.308; after stroke: HR, 1.518; 95% CI, 1.177-1.957; and after HF: HR, 1.485, 95% CI 1.041-2.117). Our results suggest that there is a significant reciprocal relationship between severe HZ requiring hospitalization and CVD including MI, ischemic stroke and HF.

Temporal trends of the prevalence and incidence of atrial fibrillation and stroke among Asian patients with hypertrophic cardiomyopathy: A nationwide population-based study

BACKGROUND

Atrial fibrillation (AF) and stroke are common in hypertrophic cardiomyopathy (HCM). We aimed to determine the prevalence and incidence of AF and stroke in patients with HCM during a 10-year period.

METHODS

Using the Korean National Health Insurance Services database, we identified patients diagnosed with HCM from the entire Korean population between 2005 and 2015. The annual prevalence and incidence of AF and stroke in HCM patients were estimated.

RESULTS

The prevalence of AF in HCM patients has gradually increased to 1.6-fold from 13.4% in 2005 to 20.9% in 2015. The incidence of AF ranged from 4.1 to 5.5%, a similar trend was observed for each year in HCM patients. The prevalence of stroke in HCM patients was approximately 10%, while that in HCM patients with AF was about 20%. During 8741 person-years, AF-related stroke occurred in 257 subjects among 2309 HCM patients with new-onset AF. The overall incidence rate of AF-associated stroke was 2.94 per 100 person-years. In subgroup analysis, the incidence rate of AF-associated stroke was 1.49 per 100 person-years in the under 45 year-old group and 1.48 per 100 person-years in the group with CHA₂DS₂-VASc score of 0 or 1 point in HCM patients.

CONCLUSIONS

The prevalence of AF in HCM patients gradually increased over 10 years. The annual risk of AF-associated stroke in HCM was over 1% even in younger patients and those with CHA₂DS₂-VASc score of 0 or 1 point, which provide evidence to support the prevention of stroke in HCM patients with AF.

Multi-ethnic genome-wide association study for atrial fibrillation

Atrial fibrillation (AF) affects more than 33 million individuals worldwide1 and has a complex heritability2. We conducted the largest meta-analysis of genome-wide association studies (GWAS) for AF to date, consisting of more than half a million individuals, including 65,446 with AF. In total, we identified 97 loci significantly associated with AF, including 67 that were novel in a combined-ancestry analysis, and 3 that were novel in a European-specific analysis. We sought to identify AF-associated genes at the GWAS loci by performing RNA-sequencing and expression quantitative trait locus analyses in 101 left atrial samples, the most relevant tissue for AF. We also performed transcriptome-wide analyses that identified 57 AF-associated genes, 42 of which overlap with GWAS loci. The identified loci implicate genes enriched within cardiac developmental, electrophysiological, contractile and structural pathways. These results extend our understanding of the biological pathways underlying AF and may facilitate the development of therapeutics for AF.

Increased Risk of Atrial Fibrillation in the Early Period after Herpes Zoster Infection: a Nationwide Population-based Case-control Study

BACKGROUND

Herpes zoster (HZ) is a chronic inflammatory disease that could result in autonomic dysfunction, often leading to atrial fibrillation (AF).

METHODS

From the Korean National Health Insurance Service database of 738,559 subjects, patients newly diagnosed with HZ (n = 30,685) between 2004 and 2011, with no history of HZ or AF were identified. For the non-HZ control group, 122,740 age- and sex-matched subjects were selected. AF development in the first two-years following HZ diagnosis, and during the overall follow-up period were compared among severe (requiring hospitalization, n = 2,213), mild (n = 28,472), and non-HZ (n = 122,740) groups.

RESULTS

There were 2,204 (1.4%) patients diagnosed with AF during follow-up, and 825 (0.5%) were diagnosed within the first two years after HZ. The severe HZ group showed higher rates of AF development (6.4 per 1,000 patient-years [PTPY]) compared to mild-HZ group (2.9 PTPY) and non-HZ group (2.7 PTPY). The risk of developing AF was higher in the first two-years after HZ diagnosis in the severe HZ group (10.6 PTPY vs. 2.7 PTPY in mild-HZ group and 2.6 PTPY in non-HZ group).

CONCLUSION

Severe HZ that requires hospitalization shows an increased risk of incident AF, and the risk is higher in the first two-years following HZ diagnosis.

Design and simulation of novel laparoscopic renal denervation system: a feasibility study

PURPOSE

In this study, we propose a novel laparoscopy-based renal denervation (RDN) system for treating patients with resistant hypertension. In this feasibility study, we investigated whether our proposed surgical instrument can ablate renal nerves from outside of the renal artery safely and effectively and can overcome the depth-related limitations of the previous catheter-based system with less damage to the arterial walls.

METHOD

We designed a looped bipolar electrosurgical instrument to be used with laparoscopy-based RDN system. The tip of instrument wraps around the renal artery and delivers the radio-frequency (RF) energy. We evaluated the thermal distribution via simulation study on a numerical model designed using histological data and validated the results by the in vitro study. Finally, to show the effectiveness of this system, we compared the performance of our system with that of catheter-based RDN system through simulations.

RESULTS

Simulation results were within the 95% confidence intervals of the in vitro experimental results. The validated results demonstrated that the proposed laparoscopy-based RDN system produces an effective thermal distribution for the removal of renal sympathetic nerves without damaging the arterial wall and addresses the depth limitation of catheter-based RDN system.

CONCLUSIONS

We developed a novel laparoscope-based electrosurgical RDN method for hypertension treatment. The feasibility of our system was confirmed through a simulation study as well as in vitro experiments. Our proposed method could be an effective treatment for resistant hypertension as well as central nervous system diseases.

Risk of ischemic stroke in metabolically healthy obesity: A nationwide population-based study

Background

Whether metabolically healthy obese (MHO) individuals are at increased risk of ischemic stroke is not well known. We investigated the association of the MHO phenotype with ischemic stroke.

Methods

A total of 354,083 adults (age 45.8 ± 14.2 years) from the Korean National Health Insurance Service–National Sample Cohort enrolled in 2004–2008 were followed-up for incident ischemic stroke until 2013. Subjects meeting none of the metabolic syndrome criteria were classified as ‘metabolically healthy’. The cohort was categorized into four groups according to obesity and metabolic status: metabolically healthy normal weight (MHNW), metabolically unhealthy normal weight (MUNW), MHO, and metabolically unhealthy obese (MUO).

Results

Ischemic stroke was newly diagnosed in 4,884 (1.4%) individuals during a mean follow-up of 7.4 ± 1.5 years. Stroke incidence rates for the MHNW, MUNW, MHO, and MUO groups were 0.56, 2.61, 0.61, and 2.76 per 1,000 person-years, respectively. While risk for stroke increased significantly in metabolically unhealthy groups, it was not increased in MHO compared to the MHNW group on multivariate analysis. In metabolically healthy individuals, obesity did not increase the risk for ischemic stroke, regardless of the severity of obesity. Meanwhile, in metabolically unhealthy individuals, being obese was significantly associated with increased risk of stroke.

Conclusions

MHO individuals were not at increased risk for ischemic stroke. However, obesity increased risk for ischemic stroke in persons with metabolic risk factors; therefore, maintaining normal weight may be more important for this population. Also, metabolic unhealthiness showed greater association than obesity with stroke.

Severe hypoglycemia is a risk factor for atrial fibrillation in type 2 diabetes mellitus: Nationwide population-based cohort study

AIMS

This study investigated the association between severe hypoglycemia (SH) and new onset atrial fibrillation (AF) and all-cause mortality in adult patients with type 2 diabetes mellitus (T2DM).

METHODS

Retrospective data on patients with T2DM aged between 30 and 75years who received healthcare checkups from January 1, 2005 to December 31, 2008 were analyzed using the National Health Insurance Database in Korea. The primary outcome was newly diagnosed non-valvular AF occurring after SH episode using ICD-10 codes.

RESULTS

Among 1,509,280 subjects, 10,864 (0.72%) patients had experienced SH events in the three years prior to health examination, and a total of 48,916 (3.24%) first-time AF episodes occurred during the follow-up period of 8.5years. The incidence of AF was significantly higher in the group with SH than the group without SH. After multivariable adjustment, previous SH was a significant risk factor for the development of AF (HR 1.10, 95% CI 1.01-1.19). All-cause mortality was also significantly increased in patients with previous SH events and prior SH with subsequent AF occurrence, compared to patients without SH events.

CONCLUSIONS

Prior SH events were associated with a higher risk of new onset AF and all-cause mortality in patients with T2DM.

Temporal trends of antithrombotic therapy for stroke prevention in Korean patients with non-valvular atrial fibrillation in the era of non-vitamin K antagonist oral anticoagulants: A nationwide population-based study

Background

Following their introduction, the non-vitamin K antagonist oral anticoagulants (NOACs) are increasingly prescribed in Asia for stroke prevention in patients with non-valvular atrial fibrillation (AF). Few contemporary data are available on temporal trends in antithrombotic therapy use in Asian countries, in the era of NOACs.

Methods and results

Using the National Health Insurance Service database of the entire Korean adult AF population, the use of aspirin, vitamin K antagonist, and NOACs between 2008 and 2015 were analyzed (n = 276,246 in 2015). Most of the included cohort had CHA₂DS₂-VASc score ≥ 2 (78.2% in 2008 and 83.2% in 2015), yet approximately 17% were prescribed no antithrombotic therapy throughout the study period. Aspirin prescription consistently decreased (from 48.2% to 31.5%) over time, while OAC prescription significantly increased from 34.7% to 50.6%. NOAC prescriptions accounted for 50% of total OAC prescription in 2015. Similar trends in antithrombotic therapy were found both in men and in women, but women were more likely to be undertreated with OAC. Female gender, presence of vascular disease and prior intracranial hemorrhage were associated with OAC underuse.

Conclusions

Between 2008 and 2015, a greater proportion of AF patients received OAC treatment with increasing NOAC prescription trends in the recent 3 years. A substantial proportion (approx. 50%) of Korean patients with AF still remain undertreated.

Association between red cell distribution width and thromboembolic events in patients with atrial fibrillation

BACKGROUND

We investigated whether an increase in the value of red cell distribution width (RDW) was associated with thromboembolic outcomes in patients with atrial fibrillation (AF).

METHODS

We performed a retrospective analysis of 5082 consecutive patients with non-valvular AF. Thromboembolic events (N=723, 14.2%) were recorded and analysed according to RDW value.

RESULTS

The peak RDW value during follow-up was higher in patients with thromboembolic events than in those without thromboembolic events (15.1% vs. 14.2%, p<0.001). The RDW value showed similar power in predicting thromboembolic outcomes compared with the factor of age. The risk of thromboembolic events was higher in patients with a peak RDW≥13.9% than in patients with a peak RDW<13.9% (hazard ratio 1.63, p<0.001), and increased with each quartile increase of RDW. In a subgroup of 739 patients with congestive heart failure (CHF), there were 112 (15.2%) thromboembolic events. The peak RDW value of patients with CHF with thromboembolic events was also significantly higher (16.4% vs. 15.6%, p=0.019) compared to that of those without thromboembolic events.

CONCLUSION

An increased RDW value during follow-up could be associated with thromboembolic events in patients with non-valvular AF. The suggested cut-off values for RDW used to predict an increased thromboembolic risk in were ≥13.9% in patients with AF in general, ≥15% in patients with co-existing AF and CHF.

Cirrhosis is a risk factor for atrial fibrillation: A nationwide, population-based study

BACKGROUND & AIMS

Information is lacking regarding whether cirrhosis is associated with atrial fibrillation development. We aimed to investigate the incidence and clinical significance of atrial fibrillation in cirrhotic patients.

METHODS

Cirrhotic patients (n=3596; mean age, 54.7±12.3 years; male, 72.5%) without previous atrial fibrillation were selected from the Korean National Health Insurance Service National Sample Cohort database between 2004 and 2008. Age- and sex-matched controls (n=17 980) were randomly sampled in a 5:1 ratio from non-cirrhotic individuals. Both cohorts were followed up for incident atrial fibrillation and death until 2013.

RESULTS

During 9 years of follow-up, atrial fibrillation was newly detected in 113 (3.1%) cirrhosis patients and 385 (2.1%) controls (incidence: 3.48 and 2.16 per 1000 person-years respectively). Cirrhotic patients were at higher risk for atrial fibrillation development compared to controls (hazard ratio, 1.46; 95% confidence interval, 1.18-1.80) after multivariate adjustment. On subgroup analysis, cirrhosis increased the risk for atrial fibrillation, especially in younger (age younger than 65 years) men without comorbidities (CHA₂ DS₂ -VASc score, 0). Cirrhotic patients showed increased overall mortality compared to controls (hazard ratio, 4.80; 95% confidence interval, 4.47-5.15) as well as increased cardiovascular mortality (hazard ratio, 1.37; 95% confidence interval, 1.07-1.75). However, there was no significant association between development of atrial fibrillation and increased mortality in cirrhosis patients (P=.188 and .260).

CONCLUSIONS

Cirrhosis was an independent risk factor for atrial fibrillation development, especially in younger, otherwise healthy men, stressing the importance of cardiac assessment in cirrhotic patients. Meanwhile, atrial fibrillation development in cirrhosis patients was not associated with increased mortality.

Effectiveness and Safety of Non-Vitamin K Antagonist Oral Anticoagulants in Asian Patients With Atrial Fibrillation

BACKGROUND AND PURPOSE

There are limited real-world data comparing the effectiveness and safety of non-vitamin K antagonist oral anticoagulants (NOACs) and warfarin in Asians with nonvalvular atrial fibrillation. We aimed to compare the effectiveness and safety between NOACs and warfarin users in the Korean atrial fibrillation population, with particular focus on high-risk patients.

METHODS

Using the Korean National Health Insurance Service database, we analyzed the risk of ischemic stroke, intracranial hemorrhage (ICH) events, and all-cause death in NOAC users (n=11 611 total, n=5681 taking rivaroxaban, n=3741 taking dabigatran, and n=2189 taking apixaban) compared with propensity score-matched warfarin users (n=23 222) among patients with high-risk atrial fibrillation (CHA₂DS₂-VASc score ≥2) between 2014 and 2015.

RESULTS

NOAC treatment was associated with similar risk of ischemic stroke and lower risk of ICH and all-cause mortality compared with warfarin. All 3 NOACs were associated with a similar risk of ischemic stroke and a lower risk of ICH compared with warfarin. Dabigatran and apixaban were associated with a lower risk of total mortality and the composite net clinical outcome (ischemic stroke, ICH, and all-cause death) compared with warfarin, whereas this was nonsignificant for rivaroxaban. Among previously oral anticoagulant-naive patients (n=23 262), dabigatran and apixaban were superior to warfarin for ICH prevention, whereas rivaroxaban and warfarin were associated with similar risk of ICH.

CONCLUSIONS

In real-world practice among a high-risk Asian atrial fibrillation population, all 3 NOACs demonstrated similar risk of ischemic stroke and lower risk of ICH compared with warfarin. All-cause mortality was significantly lower only with dabigatran and apixaban.

Ganglionated plexi as neuromodulation targets for atrial fibrillation

The autonomic nervous system plays an important role in the genesis of atrial fibrillation and is one of the candidate targets for atrial fibrillation therapy. This review focuses on the role of the autonomic nervous system in atrial fibrillation development and discusses the results of the ganglionated plexi catheter and surgical ablation in preclinical and clinical studies. The heart is innervated by the extrinsic and intrinsic autonomic nervous systems. The intrinsic autonomic nervous system consists of multiple ganglionated plexi and axons, which innervate the neighboring atrial myocardium and control their electrophysiological properties. Abnormal autonomic innervation has been observed in an animal model of atrial fibrillation and in humans. Direct recordings of autonomic nerve activity in canine models showed that atrial tachyarrhythmia episodes were invariably preceded by intrinsic cardiac autonomic nerve activity, thus supporting the importance of intrinsic cardiac autonomic nerve activity as the triggers for atrial tachyarrhythmia. Targeting ganglionated plexi with catheter ablation improves the outcomes of paroxysmal atrial fibrillation ablation in addition to pulmonary vein antrum isolation. Ablation of ganglionated plexi alone without pulmonary vein isolation is also useful in controlling paroxysmal atrial fibrillation in some patients. However, surgical ganglionated plexi ablation in patients with a large left atrium, persistent atrial fibrillation, and/or a history of prior catheter ablation does not result in additional benefits. These different outcomes suggest that ganglionated plexi ablation is effective in managing patients with paroxysmal atrial fibrillation, but its effects in patients with persistent atrial fibrillation and advanced atrial diseases might be limited.

Angiotensin II affects inflammation mechanisms via AMPK-related signalling pathways in HL-1 atrial myocytes

Inflammation is a common cause of cardiac arrhythmia. Angiotensin ІІ (Ang ІІ) is a major contributing factor in the pathogenesis of cardiac inflammation; however, its underlying molecular mechanism remains unclear. Here, we explored the effect of Ang ІІ on inflammatory mechanisms and oxidative stress using HL-1 atrial myocytes. We showed that Ang ІІ activated c-Jun N-terminal kinase (JNK) phosphorylation and other inflammatory markers, such as transforming growth factor-β1 (TGF-β1) and tumor necrosis factor-α (TNF-α). Ang ІІ decreased oxygen consumption rate, which resulted in reactive oxygen species (ROS) generation and inhibition of ROS blocked Ang II-mediated JNK phosphorylation and TGF-β1 induction. Ang ІІ induced the expression of its specific receptor, AT1R. Ang II-induced intracellular calcium production associated with Ang ІІ-mediated signalling pathways. In addition, the generated ROS and calcium stimulated AMPK phosphorylation. Inhibiting AMPK blocked Ang II-mediated JNK and TGF-β signalling pathways. Ang ІІ concentration, along with TGF-β1 and tumor necrosis factor-α levels, was slightly increased in plasma of patients with atrial fibrillation. Taken together, these results suggest that Ang ІІ induces inflammation mechanisms through an AMPK-related signalling pathway. Our results provide new molecular targets for the development of therapeutics for inflammation-related conditions, such as atrial fibrillation.

Comparison between local and systemic injection of adenosine for detecting dormant conduction after PV isolation

BACKGROUND

Adenosine administration after pulmonary vein (PV) isolation is effective for identifying dormant conduction (DC). We aimed to compare the efficacy and safety of local injection of adenosine into the PV with systemic intravenous injection.

METHODS

After complete PV isolation was performed, adenosine was injected directly into the PV (local method, 6-18 mg) and the femoral vein (systemic method, 12-30 mg) sequentially. We compared the incidence of DC and the hemodynamic effect of adenosine between the methods.

RESULTS

We analyzed 150 PVs in 40 patients who underwent atrial fibrillation ablation. A total of 16 DCs were seen in 14 patients with either the local or systemic method. Among them, two DCs were detected only by the local method (detection rate: local 10.7% vs systemic 9.3%). The effective doses of adenosine required to induce atrioventricular (AV) block or detect DC were 7.7 ± 3.1 mg (local) and 13.1 ± 3.4 mg (systemic), respectively (P < 0.001). The time interval between adenosine injection and AV block was shorter with the local than systemic method (5.8 seconds vs 11.7 seconds, P < 0.001). Six DCs (four with local and two with systemic method) were detected without manifested AV block. Additionally, there were fewer decrements in blood pressure with the local than systemic method.

CONCLUSION

Local adenosine injection via the PV was comparable to systemic administration for detecting DC after PV isolation. Furthermore, the local method required a smaller dose of adenosine, took less time to induce AV block, and resulted in less systemic hemodynamic compromise than did the systemic method.

Prognostic Implication of the QRS Axis and its Association with Myocardial Scarring in Patients with Left Bundle Branch Block

Background and Objectives

Left bundle branch block (LBBB) with left axis deviation (LAD) has a worse prognosis than LBBB with a normal axis, and myocardial dysfunction has been suggested as a cause of left axis deviation. This study investigated the prognostic significance of the QRS axis in patients with LBBB and analyzed its relationship with the amount of myocardial scarring.

Subjects and Methods

A total of 829 patients were diagnosed with LBBB at Seoul National University Hospital from October 2004 to June 2014. Of these, 314 who were asymptomatic and had no previous history of cardiac disease were included in the present study. Myocardial scarring was calculated using the Selvester QRS scoring system, and LAD was defined as a QRS axis between -180° and -30°.

Results

Of the total patients, 91 (29%) had LAD, and patients were followed for a median of 30 months. During follow-up, two patients were hospitalized for de novo heart failure, four had pacemaker implants, and 10 died. There was a significant inverse correlation between myocardial scar score and the QRS axis (r=-0.356, p<0.001). Patients with concomitant LAD had a higher rate of major cardiac adverse events compared with patients with a normal axis (5.5% vs. 1.3%, log-rank p=0.010); the prognostic value was attenuated in multivariable analysis (hazard ratio 4.117; 95% confidence interval 0.955-17.743; p=0.058).

Conclusion

Concomitant LAD is an indicator of poor prognosis for patients with LBBB and may be associated with greater myocardial scarring.

Trends in the incidence and prevalence of atrial fibrillation and estimated thromboembolic risk using the CHA2DS2-VASc score in the entire Korean population

BACKGROUND

Data on the epidemiology of atrial fibrillation (AF) and temporal trends are not well established in the Korean population. We aimed to estimate the incidence and prevalence of AF in Korea between 2008 and 2015.

METHODS

Using the National Health Insurance Service database, we analyzed as a nationwide cohort the entire Korean adult population from 2008 to 2015 (n=41,505,679 in 2015). AF was identified by using diagnostic codes.

RESULTS

During an 8-year period representing 314,311,360 person-years of follow-up, 496,341 individuals were newly diagnosed with AF. The incidence of AF increased to >1.12-fold as follows: from 15.34 to 17.14 per 10,000 person-years (p<0.001). We also found a 1.68-fold increase in the prevalence of AF, from 0.46% in 2008 to 0.67% in 2015 (p<0.001). The incidence and prevalence of AF increased with advancing age. The median age of the AF patients increased from 68 to 71years (p<0.001). The prevalence of diabetes and heart failure in AF subjects increased (p<0.001). The percentage of patients with a CHA₂DS₂-VASc score of ≥2, who were strongly recommended for anticoagulation treatment, increased from 80.2% to 86.8% (p<0.001).

CONCLUSION

The incidence and prevalence of AF gradually increased from 2008 to 2015. The proportion of AF patients who were candidates for anticoagulation therapy also significantly increased owing to population aging and increasing comorbidities (i.e., heart failure and diabetes). These findings may provide a framework to understand the actual disease burden and establish the optimal management strategy for AF.

Patient Characteristics and the Incidence of Radiation-induced Dermatitis Following Radiofrequency Catheter Ablation

Background and Objectives

Radiofrequency catheter ablation (RFCA) exposes patients to fixed angle radiation for extended periods of time. We investigated the incidence and characteristics of radiation-induced dermatitis (RID) associated with RFCA.

Subjects and Methods

We screened 1347 consecutive patients from 2000 to 2011 who underwent RFCA for any indication and reviewed patients with dermatologic issues at the 1-month follow-up. Skin lesions were classified into three groups: most likely RID, probable RID, and possible RID.

Results

Of the 1347 enrolled patients, 12 (0.89%) experienced dermatologic issues within 1 month after RFCA, including six patients (0.45%) clinically classified as 'most likely RID' and four patients (0.30%) with 'probable RID'. Ten patients, including most likely RID or probable RID patients, developed skin lesions on the right back and upper arm. Skin lesions did not improve without meticulous treatment, and three cases required surgical intervention. We compared the RID group to the remaining 1335 patients (normal group). The mean body mass indices (BMIs) of the RID and normal groups were 29.3 and 23.9 kg/m², respectively (p<0.001). Radiation exposure times were longer in the RID group (180±31.0 vs. 47±49.9 minutes, p<0.001). We further analyzed 44 patients (6 RID cases and 38 normal patients) that had BMIs >26 kg/m² and exposure times >115 minutes based on receiver operator characteristic curve analyses. Among the 35 patients without RID, 29 patients (82.9%) did not use biplane fluoroscopy.

Conclusions

Patients with high BMIs have a higher risk of developing severe RID with increasing fluoroscopy times using biplane fluoroscopy.

Evaluation of the association between diabetic retinopathy and the incidence of atrial fibrillation: A nationwide population-based study

BACKGROUND

Atrial fibrillation (AF) is prevalent among type 2 diabetic patients. However, the association between diabetic retinopathy (DR) and AF is controversial.

METHODS

We included 40,500 patients with type 2 diabetes (≥40years, mean age 62±11years, 53% men) without AF from the Korean National Insurance Service-National Sample Cohort (2002-2007). Subjects were classified without DR (non-DR, n=30,178), with DR (DR, n=8920), and with proliferative DR (PDR, n=1402).

RESULTS

During a mean 5.9-year follow-up, 1261 (3.1%) patients were newly diagnosed as having AF (4.9, 6.0, and 8.3 per 1000 person-years in the non-DR, DR, and PDR groups, respectively). In multivariate Cox proportional hazard models, patients in the DR and PDR groups had a significantly higher risk of AF than those in the non-DR group (DR group: hazard ratio [HR] 1.14, 95% confidence interval [CI] 1.00-1.30; PDR group: HR 1.46, 95% CI 1.13-1.87); p for trend <0.001). The risk of AF increased in patients with DR and end-stage renal disease (ESRD) (HR 2.39, 95% CI 1.31-3.96, p<0.001) and in those with PDR and ESRD (HR 3.59, 95% CI 1.96-5.97, p<0.001) compared to those without DR and ESRD.

CONCLUSIONS

The presence and severity of DR was significantly associated with the incidence of AF. Also, the presence of ESRD had an impact on the incidence of AF in patients with DR.

Effect of ramosetron on QTc interval: a randomised controlled trial in patients undergoing off-pump coronary artery bypass surgery

Background

Ramosetron is a relatively new 5-hydroxytryptamine three receptor antagonist with higher binding affinity and more prolonged duration of action compared to ondansetron. The present study was performed to evaluate the effects of ramosetron on QTc interval and possible cardiovascular adverse effects in patients undergoing cardiac surgery.

Method

A total of 114 patients who underwent off-pump coronary artery bypass surgery were enrolled in this randomised placebo-controlled trial. Patients were allocated into two groups that received intravenous injection of 0.3 mg ramosetron or normal saline during induction of anaesthesia. QTc intervals were measured before the operation, intraoperatively (0, 1, 2, 3, 5, 10, 15, 30, 45, 60, 90, 120, and 240 min after injection of ramosetron or normal saline), at the end of the operation, and on postoperative day 1.

Results

There were no differences in mean QTc interval between groups at every time point. However, maximal change in QTc interval during surgery was higher in the ramosetron group than the placebo group (25.1 ± 22.0 vs. 17.5 ± 14.5 ms, 95 % CI 0.34–14.78, P = 0.040). Also, there were more patients with a QTc interval increase of > 60 ms in the ramosetron group (5 vs. 0, 95 % CI 1.6–18.0, P = 0.021). There were no significant differences in cardiovascular complications.

Conclusions

Ramosetron administered during induction of anaesthesia may affect maximal change in QTc interval during off-pump coronary artery bypass surgery. Ramosetron should be used with caution in high risk patients for developing Torsades de Pointes.

Trial registration

ClinicalTrials.gov NCT02139241. Registered November 12, 2013

Electronic supplementary material

The online version of this article (doi:10.1186/s12871-016-0222-1) contains supplementary material, which is available to authorized users.

Ganglionated plexi and ligament of Marshall ablation reduces atrial vulnerability and causes stellate ganglion remodeling in ambulatory dogs

BACKGROUND

Simultaneous activation of the stellate ganglion (SG), the ligament of Marshall (LOM), and the ganglionated plexi often precedes the onset of paroxysmal atrial tachyarrhythmia (PAT).

OBJECTIVE

The purpose of this study was to test the hypothesis that ablation of the LOM and the superior left ganglionated plexi (SLGP) reduces atrial vulnerability and results in remodeling of the SG.

METHODS

Nerve activity was correlated to PAT and ventricular rate (VR) at baseline, after ablation of the LOM and SLGP, and after atrial fibrillation. Neuronal cell death was assessed with tyrosine hydroxylase and terminal deoxynucleotidyl transferase dUTP nick end label (TUNEL) staining.

RESULTS

There were 4 ± 2 PAT episodes per day in controls. None were observed in the ablation group, even though SG nerve activity and VR increased from 2.2 µV (95% confidence interval [CI] 1.2-3.3 µV) and 80 bpm (95% CI 68-92 bpm) at baseline, to 3.0 µV (95% CI 2.6-3.4 µV, P = .046) and 90 bpm (95% CI 75-108 bpm, P = .026) after ablation, and to 3.1 µV (95% CI 1.7-4.5 µV, P = .116) and 95 bpm (95% CI 79-110 bpm, P = .075) after atrial fibrillation. There was an increase in tyrosine hydroxylase-negative cells in the ablation group and 19.7% (95% CI 8.6%-30.8%) TUNEL-positive staining in both the left and right SG. None were observed in the control group.

CONCLUSION

LOM and SLGP ablation caused left SG remodeling and cell death. There was reduced correlation of the VR response and PAT to SG nerve activity. These findings support the importance of SLGP and LOM in atrial arrhythmogenesis.

Heat, heat waves, and out-of-hospital cardiac arrest

OBJECTIVE

Cardiac arrest is one of the common presentations of cardiovascular disorders and a leading cause of death. There are limited data on the relationship between out-of-hospital cardiac arrest (OHCA) and ambient temperatures, specifically extreme heat. This study investigated how heat and heat waves affect the occurrence of OHCA.

METHODS

Seven major cities in Korea with more than 1 million residents were included in this study. A heat wave was defined as a daily mean temperature above the 98th percentile of the yearly distribution for at least two consecutive days.

RESULTS

A total of 50,318 OHCAs of presumed cardiac origin were identified from the nationwide emergency medical service database between 2006 and 2013. Ambient temperature and OHCA had a J-shaped relationship with a trough at 28°C. Heat waves were shown to be associated with a 14-% increase in the risk of OHCA. Adverse effects were apparent from the beginning of each heat wave period and slightly increased during its continuation. Excess OHCA events during heat waves occurred between 3PM and 5PM. Subgroup analysis showed that those 65years or older were significantly more susceptible to heat waves.

CONCLUSIONS

Ambient temperature and OHCA had a J-shaped relationship. The risk of OHCA was significantly increased with heat waves. Excess OHCA events primarily occurred during the afternoon when the temperature was high. We found that the elderly were more susceptible to the deleterious effects of heat waves.

Is the Atrial Neural Plexis a Therapeutic Target in Atrial Fibrillation?

Circumferential pulmonary vein isolation is the mainstay of atrial fibrillation (AF) ablation, but alternative approaches and techniques have been developed to improve the outcomes. One of these additional ablation targets are ganglionated plexi of the intrinsic cardiac autonomic system that contain a variety of sympathetic and parasympathetic neurons that communicate with the extrinsic cardiac autonomic nervous system. The ganglionated plexi of the heart do not serve as a simple relay station but could modulate the autonomic interaction between the extrinsic and intrinsic cardiac autonomic system. Intrinsic cardiac autonomic nerve activity is an invariable trigger of paroxysmal atrial tachyarrhythmia, including atrial fibrillation. Although multiple studies have shown that ganglionated plexi play an important role in initiating atrial fibrillation, there is no consensus on a standardized protocol for selecting target sites and determining how ganglionated plexi ablation can best be accomplished. Recent clinical trials have demonstrated the feasibility and efficacy of ganglionated plexi ablation in addition to pulmonary vein isolation, but novel technologies and strategies are necessary to improve the current ablation techniques in managing patients with atrial fibrillation. This review focuses on the relationship between atrial ganglionated plexi and atrial fibrillation and the potential benefits and limitations of ganglionated plexi ablation in the management of atrial fibrillation.

Underweight is a risk factor for atrial fibrillation: A nationwide population-based study

BACKGROUND

Obesity is a well-known risk factor for development of atrial fibrillation (AF). However, the impact of underweight on AF has not been previously recognized. We sought to determine the risk of AF in subjects with underweight in this study.

METHODS

We analyzed clinical data from a total of 132,063 individuals with the age of 40years or older who received health care checkups arranged by the national insurance program between 2003 and 2004. Newly diagnosed nonvalvular AF was identified using claim data during a median follow-up duration of 9.0years.

RESULTS

The mean body mass index (BMI) of patients was 23.9kg/m(2), and 3,323 individuals (2.5%) were classified as being underweight (BMI <18.5kg/m(2)). During the study period, 3,237 individuals (2.5%) developed AF. There was a U-shaped relationship between BMI and AF occurrence: Each 1.0kg/m(2) increase of BMI above 20kg/m(2) was associated with a 6% increased risk of AF (p<0.001), while each 1.0kg/m(2) lower BMI below 20kg/m(2) was associated with a 13% increased risk of AF (p<0.001) after multivariable adjustment. Underweight was significantly associated with 23% increased risk of AF, while obesity classes I and II were with 26% and 120% increased risk of AF, respectively. Excess risk of AF in the underweight was independent of thyroid disease, chronic lung disease, or history of malignancy, and was not attributable to cigarette smoking, low socioeconomic status, excessive physical activity, or heavy alcohol consumption.

CONCLUSION

BMI has a U-shaped relationship with the risk of AF. Underweight was an independent risk factor for AF independent of confounding factors such as chronic lung disease and malignancy. These findings suggest that underweight is associated with biological effects that contribute to the development of AF.

Early Parasympathetic Reinnervation Is Not Related to Reconnection of Major Branches of the Vagus Nerve after Heart Transplantation

Background and Objectives

Bicaval heart transplantation (HTx) may promote parasympathetic reinnervation. However, the prevalence and timing of reinnervation have not been fully investigated. Heart rate variability (HRV) and direct vagal stimulation were used to evaluate the presence of parasympathetic reinnervation after bicaval HTx.

Subjects and Methods

A total of 21 patients (time after HTx 0.52-4.41 years, mean 1.8±1.2 years) who received a bicaval HTx was enrolled. Reinnervation was evaluated using HRV values from 24-hour Holter recordings. A cross-sectional analysis of the HRV at 0.5-1, 1-2, and >2 years after HTx was performed. We also applied high-frequency electrical stimulation (16.7 Hz, 1 msec pulse width, ≤10 V) to the cardiac branches of the vagus nerve at the level of the superior vena cava in eight patients at 6 and 12 months after HTx.

Results

The degree of parasympathetic reinnervation corresponded to the time after HTx. The HRV analysis revealed that the root mean square of the successive differences between consecutive RR-intervals (RMSSD) and high-frequency power were significantly higher during the late period (>2 years) compared with the early period (0.5-1 year) after HTx. None of the eight patients who underwent direct vagal stimulation responded during the stimulation at 6 and 12 months, whereas incremental trends in HRV parameters were observed, which indicated that parasympathetic reinnervation began within 1 year after HTx.

Conclusion

Parasympathetic reinnervation seemed to begin in the early period (<1 year) after bicaval HTx. Reconnection of major branches of the vagus nerve may not be related to early reinnervation.

Small conductance calcium-activated potassium current and the mechanism of atrial arrhythmia in mice with dysfunctional melanocyte-like cells

BACKGROUND

The melanin synthesis enzyme dopachrome tautomerase (Dct) regulates intracellular Ca(2+) in melanocytes. Homozygous Dct knockout (Dct(-/-)) adult mice are vulnerable to atrial arrhythmias (AA).

OBJECTIVE

The purpose of this study was to determine whether apamin-sensitive small conductance Ca(2+)-activated K(+) (SK) currents are upregulated in Dct(-/-) mice and contribute to AA.

METHODS

Optical mapping was used to study the membrane potential of the right atrium in Langendorff perfused Dct(-/-) (n = 9) and Dct(+/-) (n = 9) mice.

RESULTS

Apamin prolonged action potential duration (APD) by 18.8 ms (95% confidence interval [CI] 13.4-24.1 ms) in Dct(-/-) mice and by 11.5 ms (95% CI 5.4-17.6 ms) in Dct(+/-) mice at a pacing cycle length of 150 ms (P = .047). The pacing cycle length threshold to induce APD alternans was 48 ms (95% CI 34-62 ms) for Dct(-/-) mice and 21 ms (95% CI 12-29 ms) for Dct(+/-) mice (P = .002) at baseline, and it was 35 ms (95% CI 21-49 ms) for Dct(-/-) mice and 22 ms (95% CI 11-32 ms) for Dct(+/-) mice (P = .025) after apamin administration. Apamin prolonged post-burst pacing APD by 8.9 ms (95% CI 3.9-14.0 ms) in Dct(-/-) mice and by 1.5 ms (95% CI 0.7-2.3 ms) in Dct(+/-) mice (P = .005). Immunoblot and quantitative polymerase chain reaction analyses showed that protein and transcripts levels of SK1 and SK3 were increased in the right atrium of Dct(-/-) mice. AA inducibility (89% vs 11%; P = .003) and duration (281 seconds vs 66 seconds; P = .008) were greater in Dct(-/-) mice than in Dct(+/-) mice at baseline, but not different (22% vs 11%; P = 1.00) after apamin administration. Five of 8 (63%) induced atrial fibrillation episodes in Dct(-/-) mice had focal drivers.

CONCLUSION

Apamin-sensitive SK current upregulation in Dct(-/-) mice plays an important role in the mechanism of AA.