Remodeling of myocardial energy and metabolic homeostasis in a sheep model of persistent atrial fibrillation.

BACKGROUND: Atrial fibrillation (AF) is the most common progressive cardiac arrhythmia and is often associated with rapid contraction in both atria and ventricles. The role of atrial energy and metabolic homeostasis in AF progression is under-investigated. OBJECTIVES: To determine the remodeling of energy metabolism during persistent AF and the effect of eplerenone (EPL), an aldosterone inhibitor, on metabolic homeostasis. METHODS: A nonsustained atrial pacing sheep model was developed to simulate the progression of AF from paroxysmal to persistent. Metabolomic and proteomic analyses at termination of the experiment were used to analyze atrial tissues obtained from sheep in sham, sugar pill (SP) and EPL-treated groups. RESULTS: Proteomic analysis indicated that compared to the sham group, in SP group, fatty acid (FA) synthesis, FA oxidation, tricarboxylic acid (TCA) cycle processes and amino acids (AAs) transport and metabolism were reduced, while glycolytic processes were increased. In metabolomic analysis, the levels of intermediate metabolites of the glycolytic pathways, including 2-phosphoglyceric acid (2 PG), 1,3-bisphosphoglyceric acid (1,3 PG), and pyruvate, HBP (uridine diphosphate-N-acetylglucosamine, UDP-GlcNAc), TCA (citrate) and AAs were greater while the levels of the majority of lipid classes, including phosphatidic acid (PA), phosphatidylcholine (PC), phosphatidylglycerol (PG), glycerophosphoglycerophosphates (PGP), glycerophosphoinositols (PI) and glycerophosphoserines (PS), were decreased in the atria of SP group than in those of sham group. EPL-pretreatment decreased the expression of glut4 and increased the content of acylcarnitines and lipids, such as lyso phospholipids, phospholipids and neutral lipids. CONCLUSION: In the metabolic remodeling during AF, glucose and lipid metabolism were up- and down-regulated, respectively, to sustain TCA cycle anaplerosis. EPL partialy reversed the metabolic shifting.

Re-evaluation of transvenous lead extraction with modified standard technique: a prospective study in 229 patients.

As new-type powered sheaths are expensive and unavailable, the standard lead extraction techniques remain the mainstay in clinical applications in many countries. The purpose of this study was to re-evaluate the clinical application of the standard lead extraction techniques and equipment, and make some procedural modifications and innovations. In our center, between January 2006 and May 2012, 229 patients (median, 66 years) who underwent lead extraction due to infection and lead malfunction were registered and followed up prospectively with respect to clinical features, reasons for lead extraction, technical characteristics, and clinical prognosis. A total of 440 leads had to be extracted transvenously by using special tools from 229 patients (male, 72.1%). Vegetations ≥1 cm were detected in six patients. Locking Stylets were applied for 398 (90.5%) leads. Telescoping dilator polypropylene sheaths and counter traction technique were used for 202 (45.9%) leads due to lead adhesion, and the mean implant duration of the 202 leads was longer than the other 238 leads (48.9±22.6 vs. 26.6±17.8 months; P <0.01). In addition, modified isolation and snare techniques were used for 56 leads (12.7%). Minor and major procedure-related complications occurred in three (1.3%) and four (1.7%) cases respectively, including one death (0.4%). Severe lead residue occurred in one case. Complete procedural success rate was 96.1% (423/440), and clinical success rate was 98.9% (435/440). The median follow-up period was 18 (1-76) months. No infection- and procedure-related death occurred in our series. Our data demonstrated that high clinical success rate of transvenous lead extraction can be guaranteed by making full use of the standard lead extraction techniques and equipment with individualized modifications.

[Population characteristics and impact on heart rate variability, heart rate and blood pressure of passive smoking].

OBJECTIVE: To investigate the basic characteristics of passive smoking population, and the impact of passive smoking on heart rate variability, heart rate and blood pressure. METHODS: Eighty-six passive smokers [mean age: (52.4 ± 7.6) years] were recruited from patients and their relatives who visited cardiovascular outpatient department and excluded structural heart disease between June 2010 and June 2012, 80 normal subjects who were not exposed to smoking served as controls. Questionnaire survey, 24 hours ambulatory electrocardiogram examination and blood pressure measurement were performed in all recruited subjects. RESULTS: (1) Non-marriage rate [18.60% (16/86) vs. 3.75% (3/80), P < 0.01] was significantly higher while education level were significantly lower in passive smoking group than in control group. Passive smokers were more likely service industry workers [29.07% (25/86) vs. 15.00% (12/80), P < 0.05] and had longer daily working time [(7.56 ± 1.24) h vs. (6.02 ± 0.96) h, P < 0.01], and were less likely to be professional technology industry employers [20.93% (18/86) vs. 36.25% (29/80), P < 0.05] and managers [13.95% (12/86) vs. 38.75% (31/80), P < 0.01] compared to controls. The main place of passive smoking was workplace (67.44%, 58/86), entertainment venues (63.95%,55/86), restaurants (48.84%, 42/86). (2) Standard of the normal sinus RR intervals (SDNN), the normal consecutive sinus RR interval difference between the root-mean-square (rMSSD) and adjacent the difference between the RR interval>50 ms the number of share the percentage (PNN50) were significantly lower in passive smoking group than in the control group (all P < 0.05). Every 5 min average of the standard deviation of sinus RR cycle (SDNN index) and 24 h every 5 min sinus RR interval mean standard deviation (SDANN) were similar between the 2 groups (all P > 0.05). Ultra-low-frequency power (VLF), low frequency power (LF), high frequency power (HF) and LF/HF were significantly lower in passive smoking group than in the control group (all P < 0.01). (3) Heart rate and diastolic blood pressure were significantly higher in passive smoking group than in control group (all P < 0.05) while systolic blood pressure was similar between the 2 groups (P > 0.05). CONCLUSIONS: Marriage status, education level, profession and daily working time are independent determinants for passive smoking. Passive smoking mainly occurred in the workplace, entertainment venues and restaurants. Passive smoking is linked with reduced heart rate variability, increased 24 h average heart rate and diastolic blood pressure.

[Effect of the smoking cessation services in the out-patient department for patients with coronary heart disease].

OBJECTIVE: To evaluate the effects and clinical prognosis of out-patient department-based smoking cessation services for coronary heart disease (CHD) patients. METHODS: A total of 140 smoking patients diagnosed with coronary heart disease in our cardiovascular department were randomly divided into the intensive smoking cessation clinic follow-up group (intervention group, patients were informed on the importance and methods to quit smoking at the first visit and reminded for that at months interval for 6 months, n = 70) and the conventional treatment group (control group, n = 70). After 6 months, the smoking status, cardiovascular event rates, drug usage, out-patient medical costs and quality of life were compared between the two groups. RESULTS: Age, gender, concomitant diseases, drug usage were similar between the two groups at baseline (all P > 0.05). After 6 months, smoking quit rate [34.2% (24/70) vs. 5.7% (4/70), P < 0.01], drug use rates: lipid-lowering drugs [95.3% (67/70) vs. 80.4% (56/70)], ß blockers [82.4% (57/70) vs. 41.3% (28/70)], and ACEI/ARB [61.4% (43/70) vs. 34.4% (24/70)] were significantly higher in the intervention group than in the control group, while total cardiovascular event rates [21.4% (15/70) vs. 47.1% (33/70), P < 0.01] and out-patient medical costs (3789.3 RMB vs. 4984.2 RMB, P < 0.01) were significantly lower in the intervention group than in the control group. The quality of life scores derived from MYO health survey questionnaire was significantly higher in the intervention group than in the control group (P < 0.01). The top three reasons responsible for continuous smoking for all patients failed to quit smoking were: (1) others smoked more than me and still alive and healthy [90.3% (56/62)]; (2) smoking helped me to keep relaxed and reduce trouble in daily work and life [70.9% (44/62)]; (3) smoking was essential while chatting and drinking with friends [66.1% (41/62)]. The overall satisfactory rate to this smoking cessation program was 42.8% and the satisfactory rate was up to 50.0% by patients. CONCLUSIONS: Intensive outpatient smoking cessation follow-up program can significantly improve the smoking cessation rates, the guideline drug use rate and the quality of life while reduce medical costs for coronary heart disease patients.

[Types and risk factors of arrhythmia on young patients with acute coronary syndrome in Henan province].

OBJECTIVE: The types and risk factors of arrhythmia were analyzed on acute coronary syndrome (ACS) patients under the age of 44 years who were hospitalized in Henan province between September 2009 to June 2012. METHODS: Medical records of eligible patients were obtained from the information system of the First Affiliated Hospital of Zhengzhou University teleconsultation information center. Middle aged and elderly ACS patients who were hospitalized at the same period served as controls. Data on arrhythmia types, blood pressure, thyroid disease, respiratory sleep apnea syndrome, smoking history, history of alcohol consumption, eating habits, family history of early-onset arrhythmia, laboratory tests were analyzed. RESULTS: (1) Arrhythmia was detected in 110 out of young ACS patients (55%), which was significantly lower than that in the elderly ACS patients (71.05%, P < 0.01). (2) The top three arrhythmias in young ACS patients were: sinus tachycardia (30.50%), the premature ventricular contractions (19.00%), atrial flutter/atrial fibrillation (16.50%). Incidence of sinus tachycardia, atrial flutter/atrial fibrillation were significantly higher while incidence of ventricular tachycardia, ventricular fibrillation, paroxysmal supraventricular tachycardia were significantly lower in young ACS patients than in middle-aged ACS patients (all P < 0.05). The incidence of sinus tachycardia was higher while incidence of ventricular premature accelerated ventricular spontaneous cardiac rhythm, ventricular tachycardia, ventricular fibrillation, non-paroxysmal supraventricular tachycardia, atrial flutter/atrial fibrillation, paroxysmal supraventricular tachycardia, sinus bradycardia, nodal escape, atrioventricular block were significantly lower in young ACS patients than in elderly ACS patients (all P < 0.05). (3) Body mass index, incidence of smoking, coronary three-vessel disease, drinking, eating salty foods, thyroid dysfunction, sleep apnea were significantly higher in youth ACS patients with arrhythmia than in young ACS patients without arrhythmia (all P < 0. 05). (4) Logistic regression analysis found that number of diseased coronary vessels (OR = 24.293), smoking (OR = 1.112) and alcohol consumption (OR = 1.039) were independent risk factor for developing arrhythmia in young ACS patients from Henan province. CONCLUSIONS: The main types of arrhythmia are sinus tachycardia, premature ventricular contractions, atrial flutter/atrial fibrillation and the major risk factors related to the arrhythmia are number of diseased coronary vessels, smoking and alcohol consumption in young ACS patients from Henan province.

[Electrophysiological characterization and efficacy of radiofrequency ablation of focal atrial tachycardia originating from the left atrial appendage].

OBJECTIVE: To analyze the electrophysiological characteristics and efficacy of radiofrequency catheter ablation (RFA) of focal atrial tachycardia (AT) originating from the left atrial appendage (LAA). METHODS: Electrophysiologic study and RFA were performed in 9 patients (4 female) with focal AT originating from the LAA. Atrial appendage angiography was performed to identify the origin of AT. P waves were classified as negative, positive, isoelectric, or biphasic. RESULTS: The mean age was (21 +/- 9) years. AT occurred spontaneously or was induced by isoproterenol infusion rather than programmed extrastimulation and burst atrial pacing. A characteristic P-wave morphology and endocardial activation pattern were observed. Positive P-wave in inferior leads was seen in all patients, upright or biphasic (+/-) component P wave was observed in lead V1, isoelectric component or an upright component P wave with low amplitude ( < 0.1 mV) was seen in lead V2-V6. Earliest endocardial activity occurred at the distal coronary sinus (CS) in all patients. The earliest endocardial activation at the successful RFA site occurred (36.7 +/- 7.9) ms before the onset of P wave. RFA was successful in all 9 patients immediately post procedure. AT reoccurred in 2 patients within 1 month post RFA and AT disappeared post the 2nd-RFA. AT reoccurred in 1 patient and terminated after the 3rd RFA. At the final follow-up (12 +/ 5) months, all 9 patients were free of arrhythmias without antiarrhythmic drugs. CONCLUSIONS: The LAA is an uncommon site of origin for focal AT. The characteristic P wave and activation timing are suggestive for focal AT originating from the LAA. LAA focal ablation is safe and effective for patients with focal AT originating from the LAA.

[Coronary characteristics of young smokers with coronary heart disease and the effects of tobacco control on smoking cessation].

OBJECTIVE: Coronary features of young smokers and non-smokers with coronary heart disease were compared and the effect of tobacco control education was analyzed. METHODS: A total of 160 young patients (14 - 35 years old) diagnosed with coronary heart disease by coronary angiography were included in this study, patients were followed up for 3 months. There were 118 smokers and 42 non-smokers, smokers were further divided to psychological counseling intervention group (68 cases) and control group (50 cases), non-smokers were also divided into psychological counseling intervention group (22 cases) and control group (20 cases). RESULTS: Incidence of single-vessel lesion (50.84% vs. 66.67%) was significantly lower, acute coronary syndrome (75.42% vs. 50.00%), double-vessel lesions (24.58% vs. 19.05%), three-vessel lesions (11.86% vs. 4.74%) as well as coronary artery ectasias (12.71% vs. 9.52%) was significantly higher in smokers than in non-smokers. Gensini scores (61.94 ± 40.35 vs. 45.08 ± 28.97) was significantly higher in smokers than in non-smokers (all P < 0.05). At the end 3-months follow up, smoking cessation rate was significantly higher in psychological counseling intervention group than in control group (61.76% vs. 30.00%, P < 0.05). New smokers was zero in psychological counseling intervention group and 1 in control group among previous non-smokers. CONCLUSION: Smoking is linked with severe coronary artery lesion in young patients with coronary heart disease and psychological counseling intervention could significantly increase the short-term successful smoking cessation rate in these patients.

[Efficacy of minimally invasive left ventricular epicardial lead placement for cardiac resynchronization therapy].

OBJECTIVE: Ventricular resynchronization might be achieved via minimally invasive left ventricular epicardial lead placement. METHOD: Six patients with congestive heart failure underwent minimally invasive left ventricular epicardial lead placement after failed coronary sinus cannulation were followed up for 1 year, cardiac function and LV lead threshold were evaluated. RESULTS: There were no in-hospital deaths, intraoperative complications and diaphragm stimulation. Correct lead positioning was achieved in all 6 patients. LV lead thresholds remained unchanged [(1.2 ± 0.5) V vs (1.1 ± 0.4) V, P = 0.68] at 12 months follow-up. Improvements on 6 min walking test [(327 ± 77) m vs (267 ± 68) m, P = 0.001], LVEF [(26.1 ± 6.0)% vs (38.2 ± 4.7)%, P = 0.004], and NYHA functional class were evidenced at 12 months follow-up. CONCLUSION: Minimally invasive left ventricular epicardial lead placement is a safe and reliable technique and should be considered as an alternative option in case of difficult coronary venous anatomy and inability to position the lead for resynchronization therapy.

[Assessment of left ventricular systolic synchronicity by quantitative tissue velocity imaging in patients with left ventricular noncompaction].

OBJECTIVE: To assess left ventricular systolic synchronicity by quantitative tissue velocity imaging (QTVI) in patients with left ventricular noncompaction (LVNC). METHODS: Eighteen LVNC patients and 30 healthy controls were included. Two-dimensional echocardiography, QTVI was applied on parasternal long axis view, apical two-chamber and four-chamber view. Tissue velocity curve was obtained from the middle and basal segments of left ventricular posterior, lateral, septal, anterior, inferior and anteroseptal walls. Time interval from the beginning of QRS complex to the peak systolic velocity (Q-Ts) and the maximal difference in Ts among all 12 LV segments (Max-DeltaTs) was calculated. RESULTS: Q-Ts from basal and middle segments of left ventricular inferior, lateral and posterior walls was significantly prolonged in LVNC patients compared to controls (P < 0.001). Max-DeltaTs was also significantly increased in LVNC patients [(161.9 +/- 93.2) ms] than that in controls [(61.2 +/- 27.4) ms, P < 0.001]. CONCLUSIONS: There was significant left ventricular asynchronies in patients with LVNC and delayed systolic contraction occurred mostly in the basal and middle segments of left ventricular inferior, posterior and lateral walls.

Regulation of gap-junction protein connexin 43 by beta-adrenergic receptor stimulation in rat cardiomyocytes.

AIM: beta-adrenergic receptor (beta-AR) agonists are among the most potent factors regulating cardiac electrophysiological properties. Connexin 43 (Cx43), the predominant gap-junction protein in the heart, has an indispensable role in modulating cardiac electric activities by affecting gap-junction function. The present study investigates the effects of short-term stimulation of beta-AR subtypes on Cx43 expression and gap junction intercellular communication (GJIC) function. METHODS: The level of Cx43 expression in neonatal rat cardiomyocytes (NRCM) was detected by a Western blotting assay. The GJIC function was evaluated by scrape loading/dye transfer assay. RESULTS: Stimulation of beta-AR by the agonist isoproterenol for 5 min induces the up-regulation of nonphosphorylated Cx43 protein level, but not total Cx43. Selective beta(2)-AR inhibitor ICI 118551, but not beta(1)-AR inhibitor CGP20712, could fully abolish the effect. Moreover, pretreatment with both protein kinase A inhibitor H89 and G(i) protein inhibitor pertussis toxin also inhibited the isoproterenol-induced increase of nonphosphorylated Cx43 expression. Isoproterenol-induced up-regulation of nonphosphorylated Cx43 is accompanied with enhanced GJIC function. CONCLUSION: Taken together, beta(2)-AR stimulation increases the expression of nonphosphorylated Cx43, thereby enhancing the gating function of gap junctions in cardiac myocytes in both a protein kinase A- and G(i)-dependent manner.Acta Pharmacologica Sinica (2009) 30: 928-934; doi: 10.1038/aps.2009.92.

[Clinical characteristics and treatment of a Chinese family with congenital short QT syndrome.].

OBJECTIVE: To observe the clinical characteristics and therapeutic efficacy of a Chinese family with congenital short QT Syndrome (SQTs). METHODS: Fourteen family members including the proband were screened with routine clinical examination, serum electrolyte, serum myocardial enzymes, electrocardiography (ECG), Holter recording, treadmill exercise test, echocardiography and chest radiograph. High risk patient received intracardiac electrophysiological study (EPS). RESULTS: Among the fourteen family members, 4 members died of sudden cardiac death at young ages, 4 members including the proband and his two daughters and one son were diagnosed as SQTs with structurally intact hearts. Initial ECG in these subjects revealed sinus rhythm with a high peaked T wave, QTc interval

[The study of inhibiting heart rate and rapidly terminating atrial flutter of ibutilide on canine].

OBJECTIVE: To observe the electrophysiological effects of ibutilide on canine and to explore the potential mechanisms of ibutilide on terminating atrial flutter. METHODS: Eighteen mongrel dogs were anesthetized and intubated. The heart was exposed through thoracotomy for electrodes implantation. The electrophysiologic variables (heart rate, the conduction of intraatrium and interatrium, the conduction ratio of isthmus, the effective refractory period) were measured in the absence or presence of ibutilide (10 minute infusion with 0.10 mg/kg ibutilide, 30 minutes later with a maintaining dose of 0.01 mg/min). RESULTS: Ibutilide significant suppressed sinus atrial node function, the peak effect was observed at 20 - 30 min post drug infusion and heart rate returned to normal at 2 hours post infusion. Post ibutilide infusion, 1 canine developed sinus pause for 5 seconds and 2:1 atrioventricular conduction block was evidenced in another canine. The atrial, ventricular and pulmonary vein effective refractory periods were all significant prolonged (all P < 0.05) post ibutilide infusion. However, conduction of intraatrium, interatrium and isthmus remained unchanged post ibutilide infusion (all P > 0.05). CONCLUSIONS: Ibutilide could suppress sinus atrial node and the atrioventricular node function. The mechanism of ibutilide on rapidly terminating atrial flutter might be related to the prolongation of the refractory periods which might then result in the reduction of the whole excitable gap of the reentrant circuit and induce proceed inability of reentrant wavefront.

Focal atrial tachycardia originating from the left atrial appendage: electrocardiographic and electrophysiologic characterization and long-term outcomes of radiofrequency ablation.

INTRODUCTION: This study sought to investigate electrophysiologic characteristics and radiofrequency ablation (RFA) in patients with focal atrial tachycardia (AT) arising from the left atrial appendage (LAA). METHODS: This study included seven patients undergoing RFA with focal AT. Activation mapping was performed during tachycardia to identify an earlier activation in the left atria and the LAA. The atrial appendage angiography was performed to identify the origin in the LAA before and after RFA. RESULTS: AT occurred spontaneously or was induced by isoproterenol infusion rather than programmed extrastimulation and burst atrial pacing in any patient. The tachycardia demonstrated a characteristic P-wave morphology and endocardial activation pattern. The P wave was highly positive in inferior leads in all patients. Lead V1 showed upright or biphasic (+/-) component in all patients. Lead V2-V6 showed an isoelectric component in five patients or an upright component with low amplitude (<0.1 mV) in two patients. Earliest endocardial activity occurred at the distal coronary sinus (CS) ahead of P wave in all seven patients. Mean tachycardia cycle length was 381 +/- 34 msec and the earliest endocardial activation at the successful RFA site occurred 42.3 +/- 9.6 msec before the onset of P wave. RFA was acutely successful in all seven patients. Long-term success was achieved in seven of the seven over a mean follow-up of 24 +/- 5 months. CONCLUSIONS: The LAA is an uncommon site of origin for focal AT (3%). There were consistent P-wave morphology and endocardial activation associated with this type of AT. The LAA focal ablation is safe and effective. Long-term success was achieved with focal ablation in all patients.

Inositol-1,4,5-trisphosphate and ryanodine-dependent Ca2+ signaling in a chronic dog model of atrial fibrillation.

Ca2+ signaling regulation plays an important role in triggering and/or maintaining atrial fibrillation (AF). Little is known about the relationship of the inositol-1,4,5-triphosphate receptors (InsP3Rs) and ryanodine receptors (RyRs) in left atrium to chronic AF. In this study, we investigated the expression and function of InsP3R1, InsP3R2 and RyR2 in a chronic dog model of AF. AF was induced in 6 dogs by rapid right atrial pacing for 24 weeks, and a sham procedure was performed in 5 dogs (control group). The intact left atrial myocytes were used to examine the expression and function of InsP3Rs, RyRs by BODIPY(O,R) TR-X ryanodine, heparin-fluorescein conjugate, and were stimulated by caffeine, ATP to release Ca2+ through RyRs, InsP3Rs separately. We also assessed the molecular components of left atrial tissue underlying the amount of RyR2, InsP3R1 and InsP3R2 determined by RT-PCR, immunohistochemistry and Western blot analysis. In the chronic AF group, the Ca2+ released through RyRs is not altered, but the Ca2+ released through InsP3Rs increased significantly. RyR2 distributed in cytosol of myocytes, cellular membrane; its expression significantly decreased in AF group compared to controls. InsP3R1 distributed in cytosol, InsP3R2 distributed not only in cytosol, cellular membrane, but also in nuclear envelope and intercalated discs. The InsP3R1 and InsP3R2 expression significantly increased in chronic AF group compared to controls. These results indicated that in a chronic dog model of AF, the expression and function of RyR2 down-regulated; on the contrary, the expression and function of InsP3R1, InsP3R2 up-regulated, and InsP3R2 may be the major InsP3Rs, which regulate intracellular or even intercellular Ca2+ signal transmission.

[Electrophysiology of two human hyperpolarization activated cyclic nucleotide-gated potassium channels expressed in HEK293 cells].

OBJECTIVE: To express the human HCN2 and HCN4 genes in HEK293 cells and investigate the electrophysiology of the expressed channel protein. METHODS: cDNA encoding human HCN2 or HCN4 gene was ligated into a shuttle vector pAdTrack-CMV. Homologous recombination was performed in Escherichia coli of the line BJ5183. Human embryonic kidney cells of the line 293 (HEK293 cells) were cultured and transfected with the positive recombinant adenovirus plasmid. Then the HEK293 cells were infected by AdhHCN2 or AdhHCN4 and the whole cell hyperpolarization-activated currents were recorded in HEK293 cells transfected with hHCN2 and hHCN4. RESULTS: If-like currents could be found in the HEK293 cells transfected with hHCN2 and hHCN4. The channels were activated by hyperpolarized potentials. Boltzmann equation showed that the half-activation voltage of the hHCN2 and hHCN4 channels were -114.8 mV +/- 3.3 mV and -125.9 mV +/- 2.9 mV respectively (P = 0.024). The reversal slope factors of the hHCN2 and hHCN4 channels were 11.1 mV +/- 1.2 mV and 13.7 mV +/- 1.3 mV respectively (P = 0.22). The activation kinetics was faster in hHCN2 than in hHCN4, with the activation constants at -110 mV being 0.99 s +/- 0.21 s and 8.47 s +/- 2.85 s respectively. The relative permeation ratio for sodium and potassium were 0.40 and 0.34 respectively in these two channels. Caesium chloride of the concentration of 2 mmol/L prominently inhibited both currents. CONCLUSION: The target genes hHCN2 and hHCN4 are successfully expressed in HEK293 cells, and the expressed functional channels have profoundly different activation kinetics.

[The relationship of paroxysmal atrial fibrillation and regional sympathetic innervations in the atria and pulmonary veins: experiment with dogs].

OBJECTIVE: To test the hypothesis that regional sympathetic innervation in the atria and pulmonary veins are correlated with atrial fibrillation (AF). METHODS: Sixteen adult mongrel dogs underwent thoracotomy under general anesthesia. Bilateral cervical vagal trunks were decentralized. Multipolar catheters were placed into right atrial appendage (RAA), left atrial appendage (LAA), left atrium (LA), left superior pulmonary vein (LSPV), left inferior pulmonary vein (LIPV), right superior pulmonary vein (RSPV), and left inferior pulmonary vein (LIPV). The bilateral sympathovagal trunks were stimulated, S1S1 burst stimulation and S1S2 stimulation procedure were performed on different points of RAA, LAA, LA, LSPV, LIPV, RSPV, and LIPV. The TF thus induced was monitored. After that, the dogs were killed with their hearts and lungs were taken out. Immunocytochemical staining of cardiac nerves was performed using anti-tyrosine hydroxylase (TH) antibodies. The nerve fiber density was counted manually for each case and expressed as the mean number per slice. RESULTS: Two dogs died during the experiment and the whole procedure was completed on 14 dogs. There was no significant difference in the AF induction rate among the most points, however, the AF induction rate of the RIPV was significantly lower than those of the other points (all P < 0.05). The levels of density of TH-positive nerves in the atria and atrial appendages were significantly higher than those in the pulmonary veins (P = 0.02). The density of TH-positive nerves in the dogs with AF was significantly higher than that in the dog without AF (P < 0.05). The innervation of sympathetic nerves in atria and pulmonary veins was highly correlated to the induction of atrial fibrillation (r = 0.83). CONCLUSION: Regional sympathetic hyperinnervation plays an important role in atrial fibrillation induction.

T Wave Safety Margin during the Process of ICD Implantation As a Novel Predictor of T Wave Oversensing.

Introduction: T wave oversensing (TWOS) is a major drawback of implantable cardioverter defibrillator (ICD) and data on predictors of TWOS in ICD is limited. We aimed to calculate a novel index of T wave safety margin (TWSM) and assess its potential for evaluating TWOS during the procedure of ICD implantation. Methods and Results: Thirty-two consecutive patients with ICD implantation were enrolled. During each procedure of ICD implantation, different ICD generators were connected to implanted sensing lead through active-fixation leads and bridging cables. R and T wave amplitudes were measured on ICD printouts according to the gain. The ICDs were programed to the most sensitive settings to reveal possible TWOS. A novel index TWSM was calculated according to the corresponding sensing algorithm of ICD. There was discrepancy of R wave amplitudes measured by different ICDs (P < 0.01). In Fortify and Teligen ICDs, T wave amplitudes showed no difference (P > 0.05) and TWSMs were sufficiently high (post sensing: 13.0 ± 7.6 and 28.3 ± 16.5, respectively, post pacing: 5.0 ± 2.2 and 4.6 ± 0.9, respectively). In nine patients with 10 TWOS episodes detected during the procedure of ICD implantation, generators with the highest TWSM were chosen. Only one TWOS episode during pacing was recorded during the 25 ± 7 mo follow-up period. Conclusions: We first propose the index of TWSM during ICD implantation as a potentially efficient predictor for TWOS. Evaluation of TWSM might help to reduce TWOS episodes in patients with high risk of TWOS. Prospective studies are warranted to validate this index and its potential to reduce TWOS episodes.

[Screening of sleep apnea syndrome by ECG derived respiration of ambulatory electrocardiogram].

OBJECTIVE: To evaluate the feasibility of screening sleep apnea-hypopnea syndrome (SAHS) by from electrocardiogram derived respiration (EDR) of ambulatory electrocardiogram (AECG) monitoring. METHODS: The overnight sleep investigation was administered to 80 subjects by polysomnogram (PSG) and 24 hours AECG monitoring simultaneously during February through November, 2004. The electrocardiogram analyzers did not know the PSG results at all, They were both asked to give the apnea hypopnea index (AHI) by EDR and PSG respectively. The PSG result was considered as the gold standard so as to evaluate the feasibility of screening SAHS by EDR of AECG monitoring. RESULTS: The average age, male gender, body mass index, history of hypertension were higher in the SAHS(+) patients than those of the SAHS(-) patients. Automatic analysis was performed with software in a sensitivity of 75%, 87.5% and 100% respectively. When software sensitivity adjusted to 75%, the sensitivity of screening SAHS with EDR was 26.7%, with the specificity of 80%, the positive predictive value of 80%, the negative predictive value of 26.7%, the diagnose accordance rate of 40%. When software sensitivity was adjusted to 87.5%, the sensitivity of screening SAHS with EDR was 55%, with the specificity of 45%, the positive predictive value of 75%, the negative predictive value of 25%, and the diagnose accordance rate of 52.5%. When software sensitivity was adjusted to 100%, the sensitivity of screening SAHS with EDR was 88.3%, with the specificity of 35%, the positive predictive value of 84.1%, the negative predictive value of 50%, and the diagnose accordance rate of 75%. CONCLUSION: EDR technique of AECG was useful to screen the suspicious SAHS patients, sensitivity and the diagnosis coincidence rate was higher when the sensitivity of automatic analysis software was adjusted to 100%.