Atrial fibrillation detection using ambulatory smartwatch photoplethysmography and validation with simultaneous holter recording.

BACKGROUND: Atrial fibrillation (AF)-associated embolic stroke is preventable, and AF detection may help to prevent stroke in subjects with paroxysmal AF. We aimed to evaluate the AF detection performance of smartwatch photoplethysmography (PPG) and the feasibility of ambulatory monitoring for AF detection in the daily life. DESIGN AND METHODS: Consecutive subjects who underwent ambulatory Holter electrocardiogram (ECG) monitoring for AF detection or AF burden evaluation were enrolled. The participants underwent 24 hours of simultaneous Holter ECG monitoring and continuous PPG recording using a Garmin smartwatch. The PPG signals were processed for noise rejection, beat detection, beat labeling, and rhythm labeling for each 5-minute segment. The accuracy of the PPG AF detection was calculated using the corresponding simultaneous Holter ECG as the AF diagnostic standard. RESULTS: Among the 200 available participants, 112 participants (56%) developed AF (the AF group). The sensitivity, specificity, and positive predicted value of AF detection in participants were 97.3%, 88.6%, and 91.6%, respectively. The area under the receiver operating characteristic curve was 0.90. When the performance was analyzed in these 5-minute segments, the sensitivity, specificity, and positive predicted values of AF detection were 97.1%, 86.8%, and 89.7%, respectively. CONCLUSIONS: This study demonstrated the feasibility of ambulatory monitoring for AF detection using a commercial smartwatch in daily life. A smartwatch may be an alternative screening tool to standard ambulatory Holter monitoring.

P wave duration ≥150 ms predicts poor left atrial function and ablation outcomes in non-paroxysmal atrial fibrillation.

BACKGROUND: It remains unknown whether P wave duration (PWD) ≥ 150 ms measured after extensive radiofrequency catheter ablation (RFCA) can identify non-paroxysmal atrial fibrillation (non-PAF) patients at increased risk of atrial tachyarrhythmia recurrence. We investigated the predicting power of PWD and its association with left atrial (LA) reverse remodeling in patients with non-PAF undergoing pulmonary vein isolation with LA linear ablation. METHODS: We retrospectively evaluated 136 patients who underwent RFCA for drug-refractory non-PAF. Electroanatomic mapping was acquired during AF. Low-voltage area (LVA) was defined as an area with bipolar voltage ≤0.5 mV. Electrocardiography and echocardiography were performed during sinus rhythm 1 day and 3 months after RFCA. PWD was measured using amplified 12­lead electrocardiography. Prolonged PWD was defined as maximum PWD ≥ 150 ms. RESULTS: Over a mean follow-up duration of 48 ± 35 months, 28 patients experienced atrial tachyarrhythmia recurrence. PWD was positively correlated with LVA (r = 0.527, p < 0.001) and inversely correlated with LA emptying fraction (r = -0.399, p < 0.001). PWD was shortened and LA emptying fraction (LAEF) was increased in patients without atrial tachyarrhythmia recurrence during follow-up. Atrial tachyarrhythmia-free survival was significantly more likely in patients without a prolonged PWD (83.5% vs 60.7%, p = 0.002). Multivariate analysis showed that LAEF and PWD were independent predictors of atrial tachyarrhythmia recurrence. CONCLUSIONS: PWD ≥ 150 ms measured after RFCA can identify patients with non-PAF at increased risk of atrial tachyarrhythmia recurrence. PWD is correlated with LVA and LAEF and reflects LA reverse remodeling.

Sacubitril/Valsartan Therapy Ameliorates Ventricular Tachyarrhythmia Inducibility in a Rabbit Myocardial Infarction Model.

BACKGROUND: Coronary artery disease is the most common cause of heart failure (HF) in developed countries. The aim of this study was to elucidate the mechanisms of reduction of arrhythmias after sacubitril/valsartan (LCZ696) therapy in a myocardial infarction (MI)-HF rabbit model. METHODS AND RESULTS: Chronic MI in rabbits with HF were divided into 3 groups: placebo control, valsartan 30 mg/day and LCZ696 60 mg/day. After 4 weeks of therapy, an electrophysiologic study and a dual voltage-calcium optical mapping study were performed. The LCZ696 group had significantly better left ventricular ejection fraction and lower ventricular tachyarrhythmia inducibility than the valsartan and placebo groups. The most common ventricular tachyarrhythmia pattern was 1 or 2 ectopic beats originating from the peri-infarct areas, followed by re-entrant beats surrounding phase singularity points. Compared to the valsartan and placebo groups, the LCZ696 group had significantly shorter action-potential duration, shorter intracellular calcium tau constant, faster conduction velocity, and shorter pacing cycle length to induce arrhythmogenic alternans. LCZ696 therapy reduced the phosphorylated calmodulin-dependent protein kinase II (CaMKII-p) expression. CONCLUSIONS: In a rabbit model with chronic MI and HF, LCZ696 therapy ameliorated postinfarct heart function impairment and electrophysiologic remodeling and altered CaMKII-p expression, leading to reduced ventricular tachyarrhythmia inducibility.

Single Bolus Rosuvastatin Accelerates Calcium Uptake and Attenuates Conduction Inhomogeneity in Failing Rabbit Hearts With Regional Ischemia-Reperfusion Injury.

Acute statin therapy reduces myocardial ischemia/reperfusion (IR) injury-induced ventricular fibrillation (VF), but the underlying electrophysiological mechanisms remain unclear. This study sought to investigate the antiarrhythmic effects of a single bolus rosuvastatin injection in failing rabbit hearts with IR injury and to unveil the underlying molecular mechanisms. Rabbits were divided into rosuvastatin, rosuvastatin + L-NAME, control, and L-NAME groups. Intravenous bolus rosuvastatin (0.5 mg/kg) and/or L-NAME (10 mg/kg) injections were administered 1 hour and 15 minutes before surgery, respectively. Heart failure was induced using rapid ventricular pacing. Under general anesthesia with isoflurane, an IR model was created by coronary artery ligation for 30 minutes, followed by reperfusion for 15 minutes. Plasma NO end product levels were measured during IR. Then, hearts were excised and Langendorff-perfused for optical mapping studies. Cardiac tissues were sampled for Western blot analysis. Rosuvastatin increased plasma NO levels during IR, which was abrogated by L-NAME. Spontaneous VF during IR was suppressed by rosuvastatin (P < 0.001). Intracellular calcium (Cai) decay and conduction velocity were significantly slower in the IR zone. Rosuvastatin accelerated Cai decay, ameliorated conduction inhomogeneity, and reduced the inducibility of spatially discordant alternans and VF significantly. Western blots revealed significantly higher expression of enhancing endothelial NO-synthase and phosphorylated enhancing endothelial NO-synthase proteins in the Rosuvastatin group. Furthermore, SERCA2a, phosphorylated connexin43, and phosphorylated phospholamban were downregulated in the IR zone, which was attenuated or reversed by rosuvastatin. Acute rosuvastatin therapy before ischemia reduced IR-induced VF by improving SERCA2a function and ameliorating conduction disturbance in the IR zone.

One-Year Mortality Risk Stratification in Patients Hospitalized for Acute Decompensated Heart Failure: Construction of TSOC-HFrEF Risk Scoring Model.

BACKGROUND: Most previous risk prediction models in patients hospitalized for heart failure (HF) are derived from populations in Western countries, and it is unclear whether these models are applicable to Asian populations. This study aimed to construct a risk score system for predicting one-year mortality risk in Asian patients and to compare the applicability of this risk score system with the 3C-HF score system. METHODS: We used the population in the Taiwan Society of Cardiology-Heart Failure with Reduced Ejection Fraction (TSOC-HFrEF) registry, which is a prospective cohort of patients admitted for acute decompensated heart failure (ADHF) in Taiwan. The risk score system was constructed using multivariate Cox-model derived coefficients. A bootstrapping procedure was also used for bias-corrected evaluations. Comparisons between this constructed model and the 3C-HF score prediction model were evaluated using calibration plots and area under curve (AUC)/receiver operating characteristic (ROC) curve. RESULTS: Patients with complete data (n = 1127) in the TSOC-HFrEF registry were analyzed. During one year of follow-up, 14.5% (n = 163) of the patients died. A risk score system was constructed with the following predictors: body mass index, diastolic blood pressure, dyslipidemia, diabetes, aortic regurgitation, QRS duration, hemoglobin concentration, and digoxin usage. Compared to the 3C-HF score system, this risk score system had a similar discriminatory ability (AUC/ROC values of 0.675 and 0.636, p = 0.127) and both were well-calibrated in the Taiwan population. CONCLUSIONS: The proposed risk score system for predicting one-year all-cause mortality in Taiwanese patients with ADHF may facilitate risk stratification in Asian patients with HF.

Paradoxical Effects of Sodium-Calcium Exchanger Inhibition on Torsade de Pointes and Early Afterdepolarization in a Heart Failure Rabbit Model.

Calcium homeostasis plays an important role in development of early afterdepolarizations (EADs) and torsade de pointes (TdP). The role of sodium-calcium exchanger (NCX) inhibition in genesis of secondary Ca rise and EAD-TdP is still debated. Dual voltage and intracellular Ca optical mapping were conducted in 6 control and 9 failing rabbit hearts. After baseline electrophysiological and optical mapping studies, E4031 was given to simulate long QT syndrome. ORM-10103 was then administrated to examine the electrophysiological effects on EAD-TdP development. E4031 enhanced secondary Ca rise, EADs development, and TdP inducibility in both control and failing hearts. The results showed that ORM-10103 reduced premature ventricular beats but was unable to suppress the inducibility of TdP or EADs. The electrophysiological effects of ORM-10103 included prolongation of action potential duration (APD) and increased APD heterogeneity in failing hearts. ORM-10103 had a neutral effect on the amplitude of secondary Cai rise in control and heart failure groups. In this model, most EADs generated from long-short APD junction area. In conclusion, highly selective NCX inhibition with ORM-10103 reduced premature ventricular beat burden but was unable to suppress secondary Ca rise, EADs development, or inducibility of TdP. The possible electrophysiological mechanisms include APD prolongation and increased APD heterogeneity.

Inhomogeneous downregulation of INa underlies piceatannol proarrhythmic mechanism in regional ischemia-reperfusion.

BACKGROUND: Piceatannol, a grape-derived polyphenol, has been linked to proarrhythmic properties by aggravating inhomogeneous conduction delay in the ischemia-reperfusion (IR) zone to enhance arrhythmogenic alternans in heart failure (HF) rabbits. The underlying molecular mechanisms of piceatannol-induced conduction disturbance were unclear in this model. METHODS: HF was induced by 4 weeks' rapid ventricular pacing. IR injury was induced in vivo using a protocol of left coronary artery ligation and release. Left ventricular cardiomyocytes were isolated enzymatically for whole-cell patch-clamp studies. Piceatannol (10 µM) was administrated to test its inhibitory effect on sodium current (INa ). Immunoblots studies and immunoenzymological staining were conducted in tissues sampled from the IR and remote zones. RESULTS: Peak INa density was less in failing cardiomyocytes than control cardiomyocytes. IR injury further reduces peak INa density in both groups. Piceatannol showed a greater INa inhibitory effect in HF than control cardiomyocytes. Western blots showed reduced NaV 1.5 protein expression in the HF group compared to the control group but no significant difference between remote and IR zones. Immunostaining showed that IR led to cytosolic redistribution of NaV 1.5, especially in failing hearts. CONCLUSIONS: Downregulation of NaV 1.5 protein expression and reduced peak INa density are found in the failing hearts. Piceatannol exerts a greater inhibitory effect on peak INa in the failing cardiomyocytes than in the controls. IR injury further decreases peak INa density, which is more prominent in the failing hearts than in the control hearts.

Roles of impaired intracellular calcium cycling in arrhythmogenicity of diabetic mouse model.

BACKGROUND: Diabetes mellitus is associated an increased risk of ventricular arrhythmias (VAs), but the underlying electrophysiological mechanisms are not fully explored. This study was aimed to test whether dynamic factors and Cai handling play roles in arrhythmogenesis of a diabetic animal model. METHODS: We used 26 db/db type 2 diabetes mice and 28 control mice in this study. VA inducibility was evaluated in vivo under isoflurane general anesthesia. The intracellular Ca2+ (Cai ) and membrane voltage (Vm ) signals of the Langendorff-perfused mouse hearts were simultaneously recorded using the optical mapping technique. Action potential duration (APD), Cai dynamics conduction velocity (CV), and arrhythmogenic alternans were analyzed. Western blot was conducted to examine expressions of calcium handling and associated ion channels proteins. RESULTS: The diabetic db/db mice showed significantly increased VA inducibility and severity. Longer APD and Cai transient duration and slower Cai decay and CV in the db/db mice than these in the control ones were observed. Dynamic pacing showed increased incidence of spatially discordant alternans leading to more VA inducibility in the db/db mice. Western blot analyses revealed increased phosphorylated-Ca2+ /calmodulin-dependent protein kinase II protein expression and decreased ryanodine receptor protein expression, which probably underlay the molecular mechanisms of enhanced arrhythmogenicity in db/db mice. CONCLUSIONS: The type 2 diabetic mouse hearts show impaired repolarization, Cai handling homeostasis, and cardiac conduction reserve, leading to vulnerability of spatially discordant alternans development and induction of VA. Altered Cai -handling protein expressions probably underlie the molecular mechanisms of arrhythmogenicity in the type 2 diabetes animal model.

Conjunction of Endocardial and Coronary Venous System Mapping to Ablate Ventricular Arrhythmias.

BACKGROUND: Ablation of idiopathic ventricular arrhythmias (VAs) with epicardial or intramural origins is technically challenging. Herein, we have described the successful ablation of left VAs via the coronary venous system (CVS) in conjunction with endocardial map guided by three-dimensional electroanatomical map in six patients. METHODS: Out of a total consecutive 84 patients with symptomatic idiopathic VAs, radiofrequency ablation via the CVS was performed on six patients (7%). Furthermore, we reviewed patient records and electrophysiologic studies with respect to clinical characteristics. RESULTS: Activation map was conducted in 5 patients, and the earliest activation sites were identified within the CVS. The preceding times to the onset of QRS complex were longer than those at the earliest endocardial sites (36.2 ± 5.6 ms vs. 14.2 ± 6.4 ms, p = 0.02, n = 5). Spiky fractionated long-duration potentials were recorded at the successful ablation sites in all 5 patients. The other patient received pacemapping only because of few spontaneous VAs during the procedure, and the best pacemap spot was found within the CVS. Irrigated catheters were required in 4 out of 6 patients because VAs were temporarily suppressed with regular ones. CONCLUSIONS: Idiopathic VAs can be ablated via the CVS in conjunction with endocardial mapping. Additionally, spiky fractionated long-duration potential can function as a clue to identify the good ablation site.

Dantrolene suppresses ventricular ectopy and arrhythmogenicity with acute myocardial infarction in a langendorff-perfused pacing-induced heart failure rabbit model.

INTRODUCTION: Dantrolene prevents arrhythmogenic Ca(2+) release during heart failure (HF). However, direct evidence to support its antiarrhythmic effects in failing hearts with acute myocardial infarction (AMI) is lacking. METHODS AND RESULTS: HF was induced by right ventricular pacing (312 beats/min, 4 weeks) in 19 rabbits. AMI was induced by coronary artery ligation in rabbits surviving chronic pacing (n = 17). The hearts were quickly excised and Langendorff-perfused for simultaneous membrane potential and intracellular Ca(2+) (Cai ) optical mapping when ventricular fibrillation (VF) occurred or 4 hours after AMI. The VF inducibility was defined as the ability to provoke sustained VF (>2 minutes) by pacing. Dantrolene (10 µM) was administered after baseline studies. Spontaneous VF occurred in 5 rabbits (SVF group). The ventricular premature beat (VPB) burden was significantly higher in the SVF group than the non-SVF group (P < 0.05). Dantrolene suppressed VPB burden (P = 0.03) and prolonged action potential duration (APD; P < 0.05) to reduce VF inducibility (P < 0.05). However, dantrolene shortened immediate postshock APD50 even if VF storm was suppressed. CONCLUSION: In failing hearts with AMI, VPB burden plays a pivotal role in SVF occurrence. Dantrolene suppresses VPBs and/or prolongs repolarization to inhibit spontaneous VF and reduce VF inducibility.

Contrasting effects of HMR1098 on arrhythmogenicity in a Langendorff-perfused phase-2 myocardial infarction rabbit model.

BACKGROUND: The stability of dynamic factors has been reported to play a role in the antiarrhythmic actions of adenosine triphosphate (ATP)-sensitive potassium channel (KATP) opener in phase-2 myocardial infarction (MI) hearts. In the situation of the downregulation of KATP, the effects of KATP blocker (HMR1098) on the dynamic factors and electrophysiological changes during phase-2 MI remain unclear. METHODS: Dual voltage and intracellular Ca(2+) (Cai) optical mapping was performed in nine Langendorff-perfused hearts 4-5 hours after coronary artery ligation and five control hearts. Electrophysiology studies, including action potential duration (APD) restitution, conduction velocity (CV), inducibility of ventricular fibrillation (VF), VF dominant frequency, APD and Cai alternans, and Cai decay, were performed. The same protocol was repeated in the presence of HMR1098 (10 µm) after the baseline studies. RESULTS: HMR1098 significantly prolonged APD and effective refractory period to prevent sustained VF in five of nine MI hearts and two of five control hearts compared to none at baseline in both groups. On the other hand, HMR1098 steepened APD restitution slope to enhance spatially concordant alternans in both groups. In the phase-2 MI group, HMR1098 steepened CV restitution slope and enhanced spatially discordant alternans (SDA), which might account for a decreased pacing threshold of VF induction during HMR1098 infusion in phase-2 MI hearts. CONCLUSIONS: In phase-2 MI hearts, HMR1098 has contrasting effects on arrhythmogenesis, suppressing reentry and VF persistence but facilitating VF inducibility. The mechanism is the intensified induction of SDA because of the steepened APD and CV restitution slopes.

Successful treatment of macroreentrant atrial tachycardia by radiofrequency ablation targeting channels with continuous activation.

BACKGROUND: Macroreentrant atrial tachycardia (MRAT) is frequently unresponsive to antiarrhythmic drugs. The application of three-dimensional (3D) mapping and entrainment pacing contributes to a high success rate for radiofrequency ablation, but programmed electrical pacing may either terminate or transform clinical tachyarrhythmias. On the basis of clinical experiences of the use of ventricular tachycardia ablation, channels with continuous activation are suitable for reentrant circuits, and ablation at these channels can lead to noninducibility of ventricular tachycardias. We reviewed patients referred for symptomatic MRAT with identified channels with continuous activation and evaluated the efficacy of MRAT ablation by targeting these channels. METHODS: Fifteen consecutive patients (10 men, 49 ± 14 years) with MRAT illustrated by endocardial activation maps using a 3D electroanatomical mapping system (CARTO™, Biosense Webster, Diamond Bar, CA, USA) were included in this study. Continuous activation was defined as double or continuous potentials without an isoelectric interval, and sites with continuous activation were tagged for measurements of channel properties. Radiofrequency ablation was performed at those targeted sites located within the reentrant circuit. RESULTS: Radiofrequency ablation successfully eliminated MRAT in all patients. The mean cycle length was 283 ± 60 ms, and the longest activation duration was 112 ± 38 ms. The minimal and maximal bipolar voltage amplitudes were 0.13 ± 0.1 mV and 0.7 ± 0.6 mV, respectively. The targeted ablation length and width were 28.9 ± 15.3 mm and 9.4 ± 3.3 mm, respectively. CONCLUSION: Radiofrequency ablation of MRAT targeting channels with continuous activation using a 3D electroanatomical mapping system yields a high success rate.

Vericiguat suppresses ventricular tachyarrhythmias inducibility in a rabbit myocardial infarction model.

BACKGROUND: The VICTORIA trial demonstrated a significant decrease in cardiovascular events through vericiguat therapy. This study aimed to assess the potential mechanisms responsible for the reduction of cardiovascular events with vericiguat therapy in a rabbit model of myocardial infarction (MI). METHODS: A chronic MI rabbit model was created through coronary artery ligation. Following 4 weeks, the hearts were harvested and Langendorff perfused. Subsequently, electrophysiological examinations and dual voltage-calcium optical mapping studies were conducted at baseline and after administration of vericiguat at a dose of 5 µmol/L. RESULTS: Acute vericiguat therapy demonstrated a significant reduction in premature ventricular beat burden and effectively suppressed ventricular arrhythmic inducibility. The electrophysiological influences of vericiguat therapy included an increased ventricular effective refractory period, prolonged action potential duration, and accelerated intracellular calcium (Cai) homeostasis, leading to the suppression of action potential and Cai alternans. The pacing-induced ventricular arrhythmias exhibited a reentrant pattern, attributed to fixed or functional conduction block in the peri-infarct zone. Vericiguat therapy effectively mitigated the formation of cardiac alternans as well as the development of reentrant impulses, providing additional anti-arrhythmic benefits. CONCLUSIONS: In the MI rabbit model, vericiguat therapy demonstrates anti-ventricular arrhythmia effects. The vericiguat therapy reduces ventricular ectopic beats, inhibiting the initiation of ventricular arrhythmias. Furthermore, the therapy successfully suppresses cardiac alternans, preventing conduction block and, consequently, the formation of reentry circuits.

Comparing Artificial Intelligence-Enabled Electrocardiogram Models in Identifying Left Atrium Enlargement and Long-term Cardiovascular Risk.

BACKGROUND: The role of P-wave in identifying left atrial enlargement (LAE) with the use of artificial intelligence (AI)-enabled electrocardiography (ECG) models is unclear. It is also unknown if AI-enabled single-lead ECG could be used as a diagnostic tool for LAE surveillance. We aimed to build AI-enabled P-wave and single-lead ECG models to identify LAE using sinus rhythm (SR) and non-SR ECGs, and compare the prognostic ability of severe LAE, defined as left atrial diameter ≥ 50 mm, assessed by AI-enabled ECG models vs echocardiography. METHODS: This retrospective study used data from 382,594 consecutive adults with paired 12-lead ECG and echocardiography performed within 2 weeks of each other at Chang Gung Memorial Hospital. UNet++ was used for P-wave segmentation. ResNet-18 was used to develop deep convolutional neural network-enabled ECG models for discriminating LAE. External validation was performed with the use of data from 11,753 patients from another hospital. RESULTS: The AI-enabled 12-lead ECG model outperformed other ECG models for classifying LAE, but the single-lead ECG models also showed excellent performance at a left atrial diameter cutoff of 50 mm. AI-enabled ECG models had excellent and fair discrimination on LAE using the SR and the non-SR data set, respectively. Severe LAE identified by AI-enabled ECG models was more predictive of future cardiovascular disease than echocardiography; however, the cumulative incidence of new-onset atrial fibrillation and heart failure was higher in patients with echocardiography-severe LAE than with AI-enabled ECG-severe LAE. CONCLUSIONS: P-Wave plays a crucial role in discriminating LAE in AI-enabled ECG models. AI-enabled ECG models outperform echocardiography in predicting new-onset cardiovascular diseases associated with severe LAE.

Effects of SEA0400 on arrhythmogenicity in a Langendorff-perfused 1-month myocardial infarction rabbit model.

BACKGROUND: The effects of SEA0400, a Na(+) /Ca(2+) exchanger (NCX) blocker, on dynamic factors and arrhythmogenic alternans in 1-month myocardial infarction (MI) hearts remain unknown. METHODS: Simultaneous voltage and intracellular Ca(2+) (Cai ) optical mapping was performed in 12 rabbit hearts with MI for 1 month and six normal rabbit hearts as control. Western-blot studies were performed in both groups in an additional six hearts for each. Action potential duration (APD) restitution was constructed and arrhythmogenic alternans was induced by dynamic pacing. SEA0400 (0.03, 3 µM) was administered after baseline studies. RESULTS: SEA0400 suppressed pacing-induced ventricular premature beats in a concentration-dependent manner. SEA0400 at 0.03 µM steepened APD restitution slopes and enhanced spatially discordant alternans (SDA), which became insignificant at 3 µM. The VF inducibility was seven of nine at baseline, nine of nine at 0.03 µM SEA0400, and five of nine at 3 µM SEA0400 (P = NS). Significant upregulation of NCX in the remote but not periinfarct zone and less degree downregulation of DHP1α in the remote versus periinfarct zone may play a role in enhancing SDA induction by SEA0400 in 1-month MI hearts. CONCLUSIONS: In 1-month MI hearts, SEA0400 suppresses pacing-induced ventricular premature beats, but also is proarrhythmic by steepening APD restitution and enhancing SDA via NCX inhibition. Heterogeneous upregulation of NCX and downregulation of DHP1α may contribute to SDA augmentation by SEA0400 in this model. The insignificant effect of SEA0400 on VF inducibility suggests that suppression of both reentry and triggered activity is required to suppress VF induction in this model.

Blunted proarrhythmic effect of nicorandil in a Langendorff-perfused phase-2 myocardial infarction rabbit model.

BACKGROUND: Nicorandil (a K(ATP) opener) administration is reported to reduce ventricular arrhythmias 4.8 ± 2.2 hours after myocardial infarction (MI). The electrophysiological changes and the effects on dynamic factors and dynamically induced spatially discordant alternans by nicorandil during phase-2 MI are unclear. METHODS: Simultaneous voltage and intracellular Ca(2+) (Ca(i)) optical mapping was performed in nine Langendorff-perfused hearts 4-5 hours after coronary artery ligation and nine control hearts. Action potential duration (APD) restitution was constructed and arrhythmogenic alternans was induced by dynamic pacing. Western blot studies (Kir6.1 and Kir6.2) were performed in six more hearts for both groups. Nicorandil (100 µM) was administered after baseline studies. RESULTS: Phase-2 MI hearts showed longer APD, slower conduction velocity (CV), and higher ventricular fibrillation (VF) inducibility than the control hearts. Nicorandil shortened and restored APD without significant arrhythmogenic effects, and also increased the rate of Ca(i) reuptake and flattened CV restitution to suppress spatially discordant alternans, which might account for a tendency toward higher VF threshold with nicorandil infusion in phase-2 MI hearts. Immunoblotting studies showed significant down-regulation of K(ATP) protein expression, which was functionally correlated to the blunted APD shortening response to nicorandil. CONCLUSIONS: K(ATP) expression is down-regulated in phase-2 MI hearts. Nicorandil restores APD, increases the rate of Ca(i) reuptake, and flattens CV restitution to suppress spatially discordant alternans induction, which ameliorates its proarrhythmic effects during phase-2 MI.

Risk factors of recurrence and complication in radiofrequency catheter ablation of atrioventricular reentrant tachycardia in children and adolescents.

BACKGROUND: To compare potential risk factors for complications and recurrence after radiofrequency catheter ablation in symptomatic atrioventricular reentrant tachycardia in children and adolescents. METHODS: We retrospectively reviewed the data of 213 consecutive patients with symptomatic atrioventricular reentrant tachycardia who underwent both electrophysiological study and radiofrequency catheter ablation, divided these patients into two groups, children (age < 12 years) and adolescents (12 < or = rage, 18 years), and compared the location of the accessory pathway, success rate, recurrence rate, complications, presence of congenital heart disease, presence of intermittent ventricular pre-excitation, and presence of Wolff­Parkinson­White syndrome in the two groups. RESULTS: The position of the accessory pathway was mostly right sided in children (61.3%) and left sided in adolescents (61.5%). Children had significantly more congenital heart disease than adolescents (6.4% versus 0.8%). Univariate analysis showed children or adolescents with right-sided accessory pathways to be 6.84 times and those with accessory pathways on both sides of the septum 25 times more likely to relapse than those with a single accessory pathway. Multivariate analysis indicated that children or adolescents with two accessory pathways were six times, and those with intermittent ventricular pre-excitation nine times more at risk of relapsing following radiofrequency ablation than those with single accessory pathways. All five complications occurred in children. CONCLUSIONS: The findings suggest that the position and number of accessory pathways and presence of intermittent ventricular pre-excitation are related to risks of recurrence of atrioventricular reentrant tachycardia in children and adolescents.