Suicide left ventricle due to conduction disturbance following transcatheter aortic valve replacement and reversal with restoration of sinus rhythm: is there life after death?

Dynamic left ventricular outflow tract obstruction and left ventricular mid-cavity obliteration are phenomena that can complicate the postoperative course in patients who undergo surgical aortic valve replacement for aortic stenosis, and may be markers of increased morbidity and mortality. Recently, reports describing dynamic intraventricular obstruction following transcatheter aortic valve replacement (TAVR) have emerged. We report a case of dynamic left ventricular mid-cavity obstruction due to disordered atrioventricular synchrony immediately following TAVR, and its reversal with restoration of atrioventricular synchrony. This case highlights the essential role of atrial contraction in the management of this phenomenon.

Spatially Discordant Alternans and Arrhythmias in Tachypacing-Induced Cardiac Myopathy in Transgenic LQT1 Rabbits: The Importance of IKs and Ca2+ Cycling

BACKGROUND

Remodeling of cardiac repolarizing currents, such as the downregulation of slowly activating K+ channels (IKs), could underlie ventricular fibrillation (VF) in heart failure (HF). We evaluated the role of Iks remodeling in VF susceptibility using a tachypacing HF model of transgenic rabbits with Long QT Type 1 (LQT1) syndrome.

METHODS AND RESULTS

LQT1 and littermate control (LMC) rabbits underwent three weeks of tachypacing to induce cardiac myopathy (TICM). In vivo telemetry demonstrated steepening of the QT/RR slope in LQT1 with TICM (LQT1-TICM; pre: 0.26±0.04, post: 0.52±0.01, P<0.05). In vivo electrophysiology showed that LQT1-TICM had higher incidence of VF than LMC-TICM (6 of 11 vs. 3 of 11, respectively). Optical mapping revealed larger APD dispersion (16±4 vs. 38±6 ms, p<0.05) and steep APD restitution in LQT1-TICM compared to LQT1-sham (0.53±0.12 vs. 1.17±0.13, p<0.05). LQT1-TICM developed spatially discordant alternans (DA), which caused conduction block and higher-frequency VF (15±1 Hz in LQT1-TICM vs. 13±1 Hz in LMC-TICM, p<0.05). Ca2+ DA was highly dynamic and preceded voltage DA in LQT1-TICM. Ryanodine abolished DA in 5 out of 8 LQT1-TICM rabbits, demonstrating the importance of Ca2+ in complex DA formation. Computer simulations suggested that HF remodeling caused Ca2+-driven alternans, which was further potentiated in LQT1-TICM due to the lack of IKs.

CONCLUSIONS

Compared with LMC-TICM, LQT1-TICM rabbits exhibit steepened APD restitution and complex DA modulated by Ca2+. Our results strongly support the contention that the downregulation of IKs in HF increases Ca2+ dependent alternans and thereby the risk of VF.

Arrhythmogenic Biophysical Phenotype for SCN5A Mutation S1787N Depends upon Splice Variant Background and Intracellular Acidosis

BACKGROUND

SCN5A is a susceptibility gene for type 3 long QT syndrome, Brugada syndrome, and sudden infant death syndrome. INa dysfunction from mutated SCN5A can depend upon the splice variant background in which it is expressed and also upon environmental factors such as acidosis. S1787N was reported previously as a LQT3-associated mutation and has also been observed in 1 of 295 healthy white controls. Here, we determined the in vitro biophysical phenotype of SCN5A-S1787N in an effort to further assess its possible pathogenicity.

METHODS AND RESULTS

We engineered S1787N in the two most common alternatively spliced SCN5A isoforms, the major isoform lacking a glutamine at position 1077 (Q1077del) and the minor isoform containing Q1077, and expressed these two engineered constructs in HEK293 cells for electrophysiological study. Macroscopic voltage-gated INa was measured 24 hours after transfection with standard whole-cell patch clamp techniques. We applied intracellular solutions with pH7.4 or pH6.7. S1787N in the Q1077 background had WT-like INa including peak INa density, activation and inactivation parameters, and late INa amplitude in both pH 7.4 and pH 6.7. However, with S1787N in the Q1077del background, the percentages of INa late/peak were increased by 2.1 fold in pH 7.4 and by 2.9 fold in pH 6.7 when compared to WT.

CONCLUSION

The LQT3-like biophysical phenotype for S1787N depends on both the SCN5A splice variant and on the intracellular pH. These findings provide further evidence that the splice variant and environmental factors affect the molecular phenotype of cardiac SCN5A-encoded sodium channel (Nav1.5), has implications for the clinical phenotype, and may provide insight into acidosis-induced arrhythmia mechanisms.

[Combined transgenic inhibition of CaMKII and Ik1 on cardiac remodeling]

This study was aimed to establish an experimental mouse model of combined transgenic inhibition of both multifunctional Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) and inward rectifier potassium current (Ik1), and to observe whether the specific inhibition of both CaMKII and Ik1 can bring about any effects on cardiac remodeling. Mice were divided into 4 groups: wild type (WT), CaMKII inhibited (AC3-I), Ik1 inhibited (Kir2.1-AAA) and combined inhibition of both CaMKII and Ik1 (AC3-I+Kir2.1-AAA). Mice in each group received electrocardiogram (ECG) and echocardiography examination. ECG in the condition of isoproterenol (ISO) injection was also checked. The whole cell patch clamp technique was used to measure Ik1 and the transient outward potassium current (Ito) from enzymatically isolated myocytes of left ventricle. In the condition of basal status, no significant changes of heart rate, PR interval and QRS interval were observed. No mouse showed ventricular arrhythmias in all of the 4 groups. After ISO injection, each group presented no significant ventricular arrhythmias either. The indexes measured by M-mode (motion-mode) and two-dimensional echocardiography had no significant differences among the four groups. Ik1 in AC3-I group was significantly higher than those in other three groups (P < 0.01) because of the results brought about by CaMKII inhibition. Among the latter three groups, both Kir2.1-AAA group and AC3-I+Kir2.1-AAA group had a significant reduced Ik1 compared with that of WT group, which was due to the Ik1 inhibition (P < 0.01). Ito in AC3-I group was higher than that of the other three groups (P < 0.01), but there were no significant differences in Ito among WT, Kir2.1-AAA and AC3-I+Kir2.1-AAA groups. Thus, combined transgenic myocardial CaMKII and Ik1 inhibition eliminated the up-regulation of Ik1 in CaMKII inhibited mice, and had no effects on cardiac remodeling including heart structure and function as well as arrhythmias at the basic and ISO conditions. The results of this study may provide a basis for the further investigation of combined inhibition of CaMKII and Ik1 in pathogenic cardiac remodeling.

Paroxysmal atrial fibrillation in myotonic dystrophy type 1 patients: P wave duration and dispersion analysis

OBJECTIVE

Myotonic dystrophy type 1 (MD1) is characterized by cardiac involvement, in about 80% of case, that predominantly affects the conduction system. Aim of our study was to evaluate the P-wave duration and dispersion (PD) in MD1 patients underwent pacemaker implantation with conserved systolic and diastolic function.

PATIENTS AND METHODS

We enrolled 60 MD1 patients (age 51.3 ± 5 years; 11 females) underwent dual chamber pacemaker implantation for various grade of atrioventricular (AV) block. Sixty sex-and age matched non-MD1 subjects were recruited as controls. P-wave duration and dispersion were carefully measured using 12-lead electrocardiogram.

RESULTS

Compared with healthy control group, MD1 patients presented increased maximum P wave duration (106.4 ± 20.9 vs 65.9 ± 8.2 ms, p = 0.03) and PD values (40.1 ± 11 vs 27.1 ± 4.2 ms, p = 0.003). No statistically significant difference was found in minimum P wave duration (69.7 ± 11.8 vs 65.4 ± 8.1 ms, p = 0.4). The MD1 patients with paroxysmal atrial fibrillation, compared with MD1 patients without evidence of atrial fibrillation, presented increased maximum P wave duration (108.1 ± 10.4 vs 78.1 ± 7.9 ms, p = 0.001) and PD values (41.1 ± 8.5 vs 33.2 ± 4.2 ms, p = 0.003). Minimum P wave duration (68.4 ± 8.2 vs 67.1 ± 4.9 ms, p = 0.5) didn't differ between the two groups.

CONCLUSIONS

Our data showed a significantly increased P wave duration and dispersion in MD1 patients compared with age and sex-matched healthy controls. We showed a statistically significant increase in PD and P max in MD1 patients subgroup with AF compared to MD1 patients with no arrhythmias.

[Continuous positive airway pressure treatment for functional cardiac arrhythmias combined with obstructive sleep apnea hypopnea syndrome]

OBJECTIVE

To discuss the effect of continuous positive airway pressure (CPAP) treatment for functional cardiac arrhythmias combined with obstructive sleep apnea hypopnea syndrome.

METHODS

Fifty-six OSAHS patients combined functional cardiac arrhythmia were randomized divided into two groups. The 28 patients in the control group were treated with metoprolol according to cardiac guidelines, the other 28 cases in the experimental group were treated with CPAP therapy combined with metoprolol. AHI and the lowest oxygen saturation (LSaO2) were tested before and after treatment.

RESULTS

The efficiency rates were 57.1% and 17.9% in experimental and control group respectively, with statistical difference (χ2 = 7.62, P < 0.01). Total effective rates were 85.7% and 53.6% respectively, with statistical difference (χ2 = 5.41, P < 0.05). In the experimental group, there were three treatment subgroups. After treatment, AHI and the lowest oxygen saturation were significantly different (P < 0.05).

CONCLUSION

CPAP treatment can effectively eliminate respiratory disturbance index, improve the symptoms of hypooxygen at night, and effectively improve the therapeutic effect of functional cardiac arrhythmias in OSAHS patients combined with functional arrhythmia.

[2-Methylthio-adenosine-5'-triphosphate inhibits ventricular arrhythmogenesis in rabbits with chronic heart failure]

OBJECTIVE

To investigate the effects and related mechanisms of 2-methylthio-adenosine-5'-triphosphate (2-MeSATP), an important extracellular agonist that activates receptors for purine nucleotides (P2XR), on ventricular arrhythmias in rabbits with chronic heart failure (CHF).

METHODS

The male New Zealand rabbits were divide into control (n=12), CHF (n=12) and CHF+2-MeSATP groups (2-MeSATP, n=12). CHF was induced by isoproterenol injection (0.3 mg·kg⁻¹·d⁻¹ for 3 weeks) and rabbits were observed 6 months later. The main cardioelectrophysiological parameters and ventricular arrhythmias were tested by recording monophasic action potential (MAP) with burst-pacing (BCL) in rabbits in vivo. The transient outward potassium current (Ito) was recorded via whole-cell patch clamp technique and the fluorescence intensity of intracellular free Ca²⁺ was detected with Flup-3/AM loading by the laser scanning confocal microscope in enzymatically dissociated single rabbet ventricular myocytes.

RESULTS

CHF rabbits developed severely clinical CHF signs and symptoms, reduced left ventricular ejection fraction and fractional shortening as well as enlarged end-diastolic dimension. Compared with CHF group, APA and MaxdV/dt were significantly increased, while APD20, APD50 and APD90 were significantly reduced in 2-MeSATP group (all P<0.01). Moreover, 2-MeSATP could obviously shorten BCL induced ventricular arrhythmias, and decrease deducibility and persistence time of ventricular arrhythmias with burst-pacing in 2-MeSATP group in vivo (all P<0.05). With voltage clamp model, 2-MeSATP could significantly increase the current density of Ito in different command potential in CHF ventricular myocytes (all P<0.01). When holding potential was set at -50 mV and command potential was set at +50 mV, the current densities of Ito increase was more significant in 2-MeSATP group than that in CHF group ((11.79 ± 4.51) pA/pF vs. (7.94 ± 3.53) pA/pF, P<0.01). 2-MeSATP could completely change the I-V curve upward without changing the I-V curve direction in CHF ventricular myocytes. The fluorescence intensities of intracellular free Ca²⁺ increase was more significant in 2-MeSATP group compared to CHF group ((1 291.98 ± 123.31) µmol/L vs. (793.59 ± 114.65) µmol/L, P<0.01).

CONCLUSION

2-MeSATP as a potent agonist acting on P2XR could significantly shorten APD, increase heart rate and improve cardiac performance as well as decrease the susceptibility of ventricular arrhythmias in this rabbit CHF model. Our results suggest that Ito increase and sarcoplasmic reticulum uptake Ca²⁺ enhancement as well as dynamic balance of intracellular Ca²⁺ cycling sustenance might linked to the beneficial effects of 2-MeSATP in this CHF model.

Early repolarization as a predictor of premature ventricular beats

Early repolarization pattern (ERP) is a common ECG variant, characterized by J point elevation manifested either as terminal QRS slurring (the transition from the QRS segment to the ST segment) or notching (a positive deflection inscribed on terminal QRS complex) associated with concave upward ST-segment elevation and prominent T waves in at least two contiguous leads. Aim of this observational study was to compare number of premature ventricular beats in the different groups of patients with early repolarization. The result of this observational study shows that there are: 1,74 fold higher number of premature ventricular beats in 41-74 year subgroup VS 19-40 year subgroup; 1,31 fold higher number of premature ventricular beats in male subgroup VS female subgroup (But this difference is not statistically significant, because t=1,49, p=0,141); 2,85 fold higher number of premature ventricular beats in CAD+ERP subgroup VS ERP without CAD subgroup; 1,74 fold higher number of premature ventricular beats in HF+ERP subgroup VS ERP without HF subgroup; 1,81 fold higher number of premature ventricular beats in CAD+ERP subgroup VS CAD without ERP subgroup; 1,58 fold higher number of premature ventricular beats in HF+ERP subgroup VS HF without ERP subgroup; So, CAD+ERP is very arrhythmogenic condition, after this is HF+ERP, Then Age. This study shows that ERP independently increase number of PVB in different groups (CAD, HF). This is principally new and very important result. Also the number of patients is enough to make this conclusion.

Cardiac contraction induces discordant alternans and localized block

In this paper we use a simplified model of cardiac excitation-contraction coupling to study the effect of tissue deformation on the dynamics of alternans, i.e., alternations in the duration of the cardiac action potential, that occur at fast pacing rates and are known to be proarrhythmic. We show that small stretch-activated currents can produce large effects and cause a transition from in-phase to off-phase alternations (i.e., from concordant to discordant alternans) and to conduction blocks. We demonstrate numerically and analytically that this effect is the result of a generic change in the slope of the conduction velocity restitution curve due to electromechanical coupling. Thus, excitation-contraction coupling can potentially play a relevant role in the transition to reentry and fibrillation.

Global and regional left ventricular strain indices in post-myocardial infarction patients with ventricular arrhythmias and moderately abnormal ejection fraction

The aim of the study described here was to compare myocardial strains in ischemic heart patients with and without sustained ventricular tachycardia (VT) and moderately abnormal left ventricular ejection fraction (LVEF) to investigate which index could better predict VT on the basis of the analysis of global and regional left ventricular (LV) dysfunction. We studied 467 patients with previous myocardial infarction and LVEF >35%. Fifty-one patients had documented VT, and 416 patients presented with no VT. LV volumes and score index were obtained by 2-D echocardiography. Longitudinal, radial and circumferential strains were determined. Strains of the infarct, border and remote zones were also obtained. There were no differences in standard LV 2-D parameters between patients with and those without VT. Receiver operating characteristic values were -12.7% for global longitudinal strain (area under the curve [AUC] = 0.72), -4.8% for posterior-inferior wall circumferential strain (AUC = 0.80), 61 ms for LV mechanical dispersion (AUC = 0.84), -10.1% for longitudinal strain of the border zone (AUC = 0.86) and -9.2% for circumferential strain of the border zone (AUC = 0.89). In patients with previous myocardial infarction and moderately abnormal LVEF, peri-infarct circumferential strain was the strongest predictor of documented ventricular arrhythmias among all strain quantitative indices. Additionally, strain values from posterior-inferior wall infarctions had a higher association with arrhythmic events compared with global strain.

Overexpression of SCN5A in mouse heart mimics human syndrome of enhanced atrioventricular nodal conduction

BACKGROUND

In enhanced atrioventricular (A-V) nodal conduction (EAVNC) syndrome, patients have short A-V conduction times. Multiple mechanisms have been proposed to explain EAVNC; however, the electrophysiological or molecular substrate responsible for it remains unclear.

OBJECTIVE

The purpose of this study was to test the hypothesis that overexpression of SCN5A in the mouse heart may provide an animal model mimicking EAVNC.

METHODS

Electrocardiogram, atrial, His bundle, and ventricular electrograms were recorded from wild-type (WT) and transgenic (TG) mice overexpressing human SCN5A. The sodium current and NaV1.5 expression were measured using patch-clamp and immunohistochemistry techniques.

RESULTS

The P-R interval in TG mice (13.6 ± 1.2 ms) was much shorter than that in WT mice (40.2 ± 0.59 ms). In TG isolated hearts, the A-V conduction time (14.4 ± 0.81 ms) during right atrial pacing was also shorter than that in WT hearts (39.5 ± 0.62 ms). Records of His bundle electrograms revealed that atrial-to-His and His-to-ventricular intervals were shorter in TG than in WT hearts. In addition, TG hearts had a shorter Wenckebach cycle length and A-V effective refractory period. The sodium current was 2-fold greater in TG ventricular myocytes than in WT ventricular myocytes. Flecainide prolonged the A-V conduction time in TG hearts to a value close to that in WT hearts. Nifedipine prolonged the atrial-to-His interval in WT hearts but not in TG hearts. Immunohistochemistry studies revealed increased NaV1.5 labeling in TG atrial and ventricular tissues, and NaV1.5 expression in A-V junction and A-V ring regions in TG hearts.

CONCLUSION

Enhanced A-V conduction in mice overexpressing SCN5A in the heart mimics the human syndrome of EAVNC. Thus, variants in sodium channel expression in the A-V nodal region may be an electrophysiological substrate responsible for EAVNC.

The relationship between T-wave peak-to end interval and ST segment recovery on intracoronary ECG during primary PCI

OBJECTIVE

T-wave peak to end interval (TPE) is a measure of repolarization dispersion, which has been reported as a major arrhythmogenic factor post acute myocardial infarction. The aim of our study was to investigate the changes in TPE in this patient population with regard to peri-procedural intracoronary ECG findings.

PATIENTS AND METHODS

Forty-four patients (34 male and mean age of 54.9 ± 10.9 years) with acute STEMI were included. Intracoronary ECG was performed during primary PCI. TPE indices were calculated before and after the procedure. Measurement of the intracoronary ST-segment was carried out before and just after coronary blood flow was established in the infarct related artery. Intracoronary ST-segment resolution (IC-STR) was defined as ≥ 1 mm compared to baseline.

RESULTS

There was no difference with respect to baseline characteristics when patients with IC-STR were compared with patients without IC-STR. TPE values decreased significantly after primary PCI in patients with IC-STR (80.9 ± 22.8 ms vs. 65.8 ± 14.4 ms; p < 0.001) whereas they did not change significantly after PCI in patients without IC-STR (79.2 ± 20.9 ms vs. 68.5 ± 16.3 ms; p = 0.18).

CONCLUSIONS

TPE measured from surface ECG recordings is significantly reduced in STEMI patients with successful reperfusion after primary PCI, as determined by IC-ECG recordings.

[Hyperkalemia-induced failure of pacemaker capture and sensing: a case report]

Hyperkalemia may induce serious cardiac arrhythmia, with possible life-threatening effects. It may cause cardiac pacemaker (PMK) malfunctioning due to a reduction of the electronegativity of the resting myocardial potential. We report the case of a 71-year-old woman who had a previous history of chronic heart failure, chronic renal failure and DDI pacemaker. She was admitted for disturbance of consciousness. During hospitalization, she was observed for extreme hypotension, acute hyperkalemia, ventricular escape rhythm, associated with failure of pacemaker capture and sensing. She was treated with calcium chloride injection, followed by insulin/glucose and sodium bicarbonate infusions; the electrocardiogram recordings showed an correction of the PMK malfunctioning and serial improvement of the intraventricular conduction. This case supports that hyperkalemia should be closely monitored in the chronic heart failure patients combined with chronic renal failure.

BET 2: should ST elevation be measured at the J point or 60 ms later?

A shortcut systematic review was carried out to establish whether in patients with suspected acute coronary syndromes presenting to the emergency department, measurement of electrocardiographic ST elevation at the J point or 60 ms after the J point will lead to more accurate identification of patients with acute coronary occlusion who may benefit from immediate coronary revascularisation. Three studies were directly relevant to the question. The author, date and country of publication, patient group studied, study type, relevant outcomes, results and study weaknesses of these papers are tabulated. The clinical bottom line is that the current evidence does not justify a shift away from measurement of ST elevation at the J point, as advocated in international guidance. Due to the limited available evidence, however, further research in this area is necessary.

Bringing home the bacon? The next step in cardiac sodium channelopathies

Mutations in SCN5A, which encodes the α subunit of the major cardiac sodium channel Na(V)1.5, are associated with multiple cardiac arrhythmias, including Brugada syndrome. It is not clear why mutations in SCN5A result in such a variety of cardiac phenotypes, and introduction of analogous Scn5a mutations into small-animal models has not recapitulated alterations in cardiac physiology associated with human disease. In this issue of the JCI, Park and colleagues present a pig model of cardiac sodium channelopathy that was generated by introducing a human Brugada syndrome-associated SCN5A allele. This large-animal model exhibits many phenotypes seen in patients with SCN5A loss-of-function mutations and has the potential to provide important insight into sodium channelopathies.

Genetically engineered SCN5A mutant pig hearts exhibit conduction defects and arrhythmias

SCN5A encodes the α subunit of the major cardiac sodium channel Na(V)1.5. Mutations in SCN5A are associated with conduction disease and ventricular fibrillation (VF); however, the mechanisms that link loss of sodium channel function to arrhythmic instability remain unresolved. Here, we generated a large-animal model of a human cardiac sodium channelopathy in pigs, which have cardiac structure and function similar to humans, to better define the arrhythmic substrate. We introduced a nonsense mutation originally identified in a child with Brugada syndrome into the orthologous position (E558X) in the pig SCN5A gene. SCN5A(E558X/+) pigs exhibited conduction abnormalities in the absence of cardiac structural defects. Sudden cardiac death was not observed in young pigs; however, Langendorff-perfused SCN5A(E558X/+) hearts had an increased propensity for pacing-induced or spontaneous VF initiated by short-coupled ventricular premature beats. Optical mapping during VF showed that activity often began as an organized focal source or broad wavefront on the right ventricular (RV) free wall. Together, the results from this study demonstrate that the SCN5A(E558X/+) pig model accurately phenocopies many aspects of human cardiac sodium channelopathy, including conduction slowing and increased susceptibility to ventricular arrhythmias.

Assessment of atrial electromechanical delay in patients with migraine

Evidence suggests that symptoms of migraine are related to the involvement of the autonomic nervous system. Data on atrial conduction system are limited in migraineurs. We aimed to assess atrial electromechanical delay using tissue Doppler imaging (TDI) in patients with migraine. Forty-five migraine patients and age- and sex-matched 26 control subjects were enrolled in the study. All the patients and controls underwent resting surface electrocardiogram (ECG) and TDI. The maximum P-wave duration (Pmax), minimum P-wave duration (Pmin) and P-wave dispersion (Pd) were measured from the 12-lead ECG. Atrial conduction time was determined from the lateral mitral annulus (PA lateral), septal mitral annulus (PA septal), and lateral tricuspid annulus (PA tricuspid) by TDI. Interatrial (PA lateral-PA tricuspid) and intraatrial (PA septal-PA tricuspid) electromechanical delays were calculated. Pd was significantly higher in migraine patients than in controls (p < 0.05), whereas Pmax and Pmin were not different between both groups (p > 0.05). PA lateral and PA septal durations were significantly higher in migraine patients than in controls (p < 0.001 and p < 0.05, respectively). However, PA tricuspid duration was similar between the groups (p > 0.05). Both interatrial and intraatrial conduction times were delayed in migraineurs as compared to the controls (p < 0.001). Interatrial delay and intraatrial delay variables were found as an independent risk factors separately on predicting atrial conduction abnormalities in migraineurs. An interatrial delay of 18 ms and an intraatrial delay of 5 ms were found to be cutoff values in ROC analysis (p < 0.001). This is the first report to provide a hypothetical suggestion that there is an atrial electromechanical delay in patients with migraine.

[Catheter ablation of focus triggering ventricular fibrillation in patients with structural heart disease]

First experiences with ablation of focus triggering ventricular fibrillation were reported in isolated cases of idiopathic ventricular fibrillation. Later, there were described the options in management of an electrical instability triggered by ectopic activity in patients after myocardial infarction. In both cases it was shown that the sources of extrasystoles originate almost exclusively from conducting system of chambers. Subsequently, isolated cases were also reported in other structural diseases. It is important that the urgent catheter ablation is able to remove focus which triggers electric instability. In many cases it is a lifesaving procedure. This review summarizes the current knowledge of the catheter ablation of focus triggering ventricular fibrillation with structural heart disease.

Rate and patient features associated with recurrence of acute myocarditis

BACKGROUND

Rate and patient features associated with recurrence after acute myocarditis are largely unknown.

METHODS AND RESULTS

First recurrence of acute myocarditis was studied in 1662 patients aged 16-70 years using a registry data of 29 hospitals in Finland (median follow-up 4.5 years). Matched intoxication patients served as controls. Incidence rate of first time hospitalization due to acute myocarditis was 5.52 (CI 5.26-5.79) per 100,000 person-years during 2001-2008. During the first 30 days 5.5% (CI 3.5-4.4%) of patients were re-admitted to hospital with acute myocarditis (p<0.0001 vs. controls). After 30 days, recurrence rate was 7.0% (CI 5.7-8.6%; p<0.0001 vs. controls). Acute myocarditis recurred after 365 days in 4.7% (CI 3.2-6.7%) of patients (p<0.0001 vs. controls). During the whole follow-up, recurrence rate was 10.3% (CI 8.8-12.1%; p<0.0001 vs. controls) with median recurrence time of 34.5 days. Prolonged (>7 days) initial admission was associated with recurrences during (HR 2.9; CI 1.6-5.2) and after first month (HR 1.8; CI 1.2-3.2), and overall (HR 2.0; CI 1.3-3.2). Ventricular arrhythmia at initial occurrence was associated with recurrence after 30 days (HR 8.6; CI 2.5-30.1), after 1 year (HR 22.6; CI 2.5-201.4) and overall (HR 6.7; CI 2.3-6.7). Other features associated with recurrence were younger age (>365 days), inflammatory bowel disease (during first month), and chronic pulmonary disease (≥ 30 days).

CONCLUSIONS

Acute myocarditis reoccurs in a significant proportion of patients. Prolonged initial admission, ventricular arrhythmias, younger age, inflammatory bowel disease and chronic pulmonary disease are associated with recurrences at different phases after acute myocarditis.

Insights into new-onset rhythm conduction disorders detected by multi-detector row computed tomography after transcatheter aortic valve implantation

New-onset rhythm conduction disorders are frequent after transcatheter aortic valve implantation (TAVI). Multidetector row computed tomography may shed light on the pathophysiology of rhythm conduction disorders in patients who undergo TAVI with the Edwards SAPIEN valve. A total of 94 patients (mean age 81 ± 7 years, 48% men) treated with TAVI with the Edwards SAPIEN valve who underwent pre- and post-TAVI multidetector row computed tomography were included. Patients with preexisting right bundle branch block or left bundle branch block (LBBB) and permanent pacemakers were excluded. Pacemaker implantation or new-onset LBBB at 1-month follow-up was the combined end point. Overall, 1 pacemaker was implanted, and 14 cases of new-onset LBBB were recorded. Among several clinical and multi-detector row computed tomographic variables, overexpansion of the transcatheter valve >15% of native annular area (odds ratio 5.277, 95% confidence interval 1.398 to 19.919, p = 0.014) and depth of frame into the left ventricular outflow tract (odds ratio 1.401, 95% confidence interval 1.066 to 1.770, p = 0.010) were independently related to the need for a pacemaker or new-onset LBBB. In conclusion, overexpansion of the transcatheter prosthesis by >15% of native aortic annular area and implantation depth of the frame into the left ventricular outflow tract were independently associated with the need for a pacemaker or new-onset LBBB in patients who underwent TAVI with the Edwards SAPIEN valve.

Prognostic value of automatically detected early repolarization

Early repolarization associated with sudden cardiac death is based on the presence of >1-mm J-point elevations in inferior and/or lateral leads with horizontal and/or downsloping ST segments. Automated electrocardiographic readings of early repolarization (AER) obtained in clinical practice, in contrast, are defined by ST-segment elevation in addition to J-point elevation. Nonetheless, such automated readings may cause alarm. We therefore assessed the prevalence and prognostic significance of AER in 211,920 patients aged 18 to 75 years. The study was performed at a tertiary medical center serving a racially diverse urban population with a large proportion of Hispanics (43%). The first recorded electrocardiogram of each individual from 2000 to 2012 was included. Patients with ventricular paced rhythm or acute coronary syndrome at the time of acquisition were excluded from the analysis. All automated electrocardiographic interpretations were reviewed for accuracy by a board-certified cardiologist. The primary end point was death during a median follow-up of 8.0 ± 2.6 years. AER was present in 3,450 subjects (1.6%). The prevalence varied significantly with race (African-Americans 2.2%, Hispanics 1.5%, and non-Hispanic whites 0.9%, p <0.01) and gender (male 2.4% vs female 0.6%, p <0.001). In a Cox proportional hazards model controlling for age, smoking status, heart rate, QTc, systolic blood pressure, low-density lipoprotein cholesterol, body mass index, and coronary artery disease, there was no significant difference in mortality regardless of race or gender (relative risk 0.98, 95% confidence interval 0.89 to 1.07). This was true even if J waves were present. In conclusion, AER was not associated with an increased risk of death, regardless of race or gender, and should not trigger additional diagnostic testing.

Mechanisms of atrial fibrillation: rotors, ionic determinants, and excitation frequency

Atrial fibrillation (AF) is the most common cardiac arrhythmia; however, therapy is suboptimal. We review recent data on dynamics of wave propagation during AF and its mechanistic link to the substrate. Data show that the dominant frequency (DF) increase during transition to persistent AF may be explained by rotor acceleration. We discuss how translation of experimentally derived understanding of the rotors may find its way into the clinic, focusing on studies analyzing spatial distribution of DF in the atria of patients with paroxysmal versus persistent AF, and how that knowledge might contribute to improve the outcome of AF ablation procedures.

[κ-opioid receptor agonist U50, 488H attenuates myocardial ischemia-reperfusionvia modulating Toll-like receptor 4/nuclear factor-κB signaling in rat]

OBJECTIVE

To observe the effects of κ-opioid receptor agonist U50, 488H on myocardial ischemia and reperfusion injury and related mechanism.

METHODS

Rats were randomly divided into sham operation, myocardial ischemia and reperfusion(I/R, 30 min ischemia followed by 120 min reperfusion), and MI/R+U50, 488H (1.5 mg/kg) and I/R+U50, 488H+ selective κ-opioid receptor antagonist Nor-BNI (2 mg/kg, n = 8 each). The infarction size and the incidence of ventricular arrhythmias were observed.Real-time PCR and DAB staining were used to define the myocardium Toll-like receptor 4(TLR4) expression. Myeloperoxidase level, TNF-α induction and the expression of NF-κB were also examined in rats.

RESULTS

After I/R, the expressions of myocardial TLR4 and NF-κB increased significantly both in ischemia area and area at risk. Compared with I/R, κ-opioid receptor stimulation with U50, 488H significantly attenuated the expressions of TLR4 and NF-κB and reduced myeloperoxidase (MPO) levels, myocardial TNF-α production, myocardial infarct sizes and the incidence of ventricular arrhythmias and arrhythmia score (2.9 ± 0.7 vs. 4.4 ± 0.9, P < 0.05) , above effects of U50, 488H were partly abolished by co-treatment with Nor-BNI.

CONCLUSION

These data provide evidence for the first time that κ-opioid receptor stimulation could attenuate myocardial I/R injury via downregulating TLR4/NF-κB signaling in rats.

[Assessment of clinical-instrumental, morphological data and expression of coxsackie adenovirus receptor in patients with inflammatory cardiac pathology]

In 22 patients with heart failure and/or ventricular arrhythmias presumably of inflammatory etiology the results of clinical and instrumental investigation were analyzed and compared to the endomyocardial biopsy data. In the subgroup of patients with left bundle branch block (LBBB) we revealed features indicative of lesser contribution of inflammatory destruction in pathogenesis of cardiomyopathy. The only virus, detected in biopsy samples, was parvovirus B19. Its persistence in myocardium was not related to activity of inflammation and severity of clinical course. Increased expression of Coxsackie adenovirus receptor (CAR) was found in 20 patients. It was not related to inflammatory cells infiltration and virus persistence in myocardium. Patients with most prominent CAR expression were characteried by right heart dilatation, more severe heart failure and absence of LBBB. Enhancement of CAR expression could reflect the attempt of organism to repair intercellular communications between cardiomyocites and to protect cells from the products of necrotic lysis during long standing inflammation.

Hypoglycaemia and QT interval prolongation in type 1 diabetes--bridging the gap between clamp studies and spontaneous episodes

AIMS

We propose a study design with controlled hypoglycaemia induced by subcutaneous injection of insulin and matched control episodes to bridge the gap between clamp studies and studies of spontaneous hypoglycaemia. The observed prolongation of the heart rate corrected QT interval (QTc) during hypoglycaemia varies greatly between studies.

METHODS

We studied ten adults with type 1 diabetes (age 41±15years) without cardiovascular disease or neuropathy. Single-blinded hypoglycaemia was induced by a subcutaneous insulin bolus followed by a control episode on two occasions separated by 4weeks. QT intervals were measured using the semi-automatic tangent approach, and QTc was derived by Bazett's (QTcB) and Fridericia's (QTcF) formulas.

RESULTS

QTcB increased from baseline to hypoglycaemia (403±20 vs. 433±39ms, p<0.001). On the euglycaemia day, QTcB also increased (398±20 vs. 410±27ms, p<0.01), but the increase was less than during hypoglycaemia (p<0.001). The same pattern was seen for QTcF. Plasma adrenaline levels increased significantly during hypoglycaemia compared to euglycaemia (p<0.01). Serum potassium levels decreased similarly after insulin injection during both hypoglycaemia and euglycaemia.

CONCLUSIONS

Hypoglycaemia as experienced after a subcutaneous injection of insulin may cause QTc prolongation in type 1 diabetes. However, the magnitude of prolongation is less than typically reported during glucose clamp studies, possible because of the study design with focus on minimizing unwanted study effects.

[Cardioprotective effect and mechanism of intensive lipid modulation on patients with coronary artery disease undergoing noncardiac surgery]

OBJECTIVE

To explore the protective effect and possible mechanism of intensive lipid modulation on the perioperative period of patients with stable coronary artery disease undergoing noncardiac surgery.

METHODS

In the study, 60 patients with stable coronary artery disease undergoing elective noncardiac surgery were randomly divided into intensive lipid modulation group (n = 30) and conventional group (n = 30). In intensive lipid modulation group, the patients were given atorvastatin 40 mg every night before surgery, 80 mg 12 h before surgery, and 40 mg 2 h before surgery, and 40 mg every night after noncardiac surgery. In conventional group, the patients were given atorvastatin 20 mg every night before surgery and also after the surgery. The occurrence of perioperative major adverse cardiac events (including sudden cardiac death, acute myocardial infarction, unplanned revascularization) were compared in the two groups. Preoperative and 48 h postoperative changes of lipid levels and inflammatory markers were also compared in the two groups.

RESULTS

In conventional group, one patient suffered myocardial infarction with acute anterior ST-segment elevation and was given emergency left anterior descending artery interventional reperfusion therapy, and 7 patients suffered asymptomatic myocardial infarction. In intensive lipid modulation group, one patient suffered asymptomatic myocardial infarction, and the incidence rate of perioperative acute myocardial infarction reduced significantly compared with conventional group (P < 0.05). There was no significant difference in preoperative and postoperative changes of lipid levels in the two groups (P > 0.05), and compared with conventional group, there was significantly lower levels of inflammatory markers in intensive lipid modulation group (P < 0.05).

CONCLUSION

The intensive lipid modulation group significantly reduced the incidence of perioperative major adverse cardiac events especially asymptomatic myocardial infarction, and the inhibition of the inflammatory response may be one of the protective mechanisms, which still needs to be further confirmed by large multicenter randomized controlled clinical trials.

Sinoatrial node dysfunction induces cardiac arrhythmias in diabetic mice

BACKGROUND

The aim of this study was to probe cardiac complications, including heart-rate control, in a mouse model of type-2 diabetes. Heart-rate development in diabetic patients is not straight forward: In general, patients with diabetes have faster heart rates compared to non-diabetic individuals, yet diabetic patients are frequently found among patients treated for slow heart rates. Hence, we hypothesized that sinoatrial node (SAN) dysfunction could contribute to our understanding of the mechanism behind this conundrum and the consequences thereof.

METHODS

Cardiac hemodynamic and electrophysiological characteristics were investigated in diabetic db/db and control db/+ mice.

RESULTS

We found improved contractile function and impaired filling dynamics of the heart in db/db mice, relative to db/+ controls. Electrophysiologically, we observed comparable heart rates in the two mouse groups, but SAN recovery time was prolonged in diabetic mice. Adrenoreceptor stimulation increased heart rate in all mice and elicited cardiac arrhythmias in db/db mice only. The arrhythmias emanated from the SAN and were characterized by large RR fluctuations. Moreover, nerve density was reduced in the SAN region.

CONCLUSIONS

Enhanced systolic function and reduced diastolic function indicates early ventricular remodeling in obese and diabetic mice. They have SAN dysfunction, and adrenoreceptor stimulation triggers cardiac arrhythmia originating in the SAN. Thus, dysfunction of the intrinsic cardiac pacemaker and remodeling of the autonomic nervous system may conspire to increase cardiac mortality in diabetic patients.

Natural products as potential human ether-a-go-go-related gene channel inhibitors - outcomes from a screening of widely used herbal medicines and edible plants

Inhibition of the human ether-a-go-go-related gene channel is the single most important risk factor leading to acquired long QT syndrome. Drug-induced QT prolongation can cause severe cardiac complications, including arrhythmia, and is thus a liability in drug development. Considering the importance of the human ether-a-go-go-related gene channel as an antitarget and the daily intake of plant-derived foods and herbal products, surprisingly few natural products have been tested for channel blocking properties. In an assessment of possible human ether-a-go-go-related gene liabilities, a selection of widely used herbal medicines and edible plants (vegetables, fruits, and spices) was screened by means of a functional two-microelectrode voltage-clamp assay with Xenopus oocytes. The human ether-a-go-go-related gene channel blocking activity of selected extracts was investigated with the aid of a high-performance liquid chromatography-based profiling approach, and attributed to tannins and alkaloids. Major European medicinal plants and frequently consumed food plants were found to have a low risk for human ether-a-go-go-related gene toxicity.

[Clinical characteristics and prognosis comparison of Chinese non ST-segment elevation acute coronary syndrome patients in two different time periods]

OBJECTIVE

To compare the clinical characteristics, treatment methods and outcomes in Chinese non ST-segment elevation acute coronary syndrome (NSTE-ACS) patients from two large clinical trials in different time periods.

METHODS

All Chinese NSTE-ACS patients from two large International clinical trials (OASIS Registry and TIMACS) underwent coronary artery angiography after first admission were recruited in our analysis. The follow-up time was 180 days. A total of 1 473 NSTE-ACS patients were recruited in this analysis, in which 749 from Organization to Assess Strategies for Ischemic Syndromes (OASIS REISTRY) that completed in 38 centers in China from April 1999 to December 2000, and the rest 724 patients from The Timing of Intervention in Acute Coronary Syndromes (TIMACS) trial in 24 centers in China performed from April 2007 to June 2008.

RESULTS

Compared to OASIS patients, TIMACS group were older ((64.2 ± 10.1) years old vs. (58.7 ± 10.2) years old) , and fewer male patients (66.3% (480/724) vs. 74.4% (557/749)) , lower blood pressure at admission, and more histories of previous PCI (9.4% (68/724 vs. 6.4% (48/749)), stroke (8.8% (64/724) vs. 5.1% (38/749)) , hypertension (62.8% (455/724) vs. 56.6% (424/749)) and diabetes (23.3% (169/724) vs. 16.2% (121/749)), lower histories of coronary artery disease (37.4% (271/724) vs. 59.1% (443/749)) and myocardial infarction (12.0% (87/724) vs. 27.6% (207/749)) (all P < 0.05). After admission, comparing to OASIS group, TIMACS patients had significant higher PCI proportion (74.9% (524/724) vs. 49.3% (369/749), P < 0.001). In addition, for secondary prevention, TIMACS patients had significant higher standard medication treatment proportion during hospitalization, at discharge and at 180 days follow up than OASIS group (P < 0.05 for β-blocker, ACEI/ARB and lipid lowering drugs) and higher compliance rate. The combined primary outcome event rate at 180 days was much lower in TIMACS than in OASIS patients (13.3% (96/724) vs. 25.2% (189/749), P < 0.001) mostly due to the reduction on the refractory angina (5.2% (38/724) vs. 22.6% (169/749), P < 0.001) .

RESULTS

of COX regression model adjusted for baseline levels and treatment during hospitalization showed that the incidence rate of combination endpoint (HR = 0.39, 95% CI: 0.29-0.53, P < 0.001) and refractory ischemia/angina rehospitalization (HR = 0.17, 95% CI: 0.11-0.25, P < 0.001) were both lower in TIMACS patients than in OASIS patients.

CONCLUSION

PCI procedure and secondary prevention medication administration are more often applied in TIMACS patients than in OASIS group, which is related to less integrated incidence of primary outcomes reflecting progress in Chinese medical care for non ST elevated acute coronary syndrome patients according to the updated guidelines.

Outcome of recombinant tissue plasminogen activator in ST-segment elevation myocardial infarction in Buriram Hospital

OBJECTIVE

To study clinical outcomes of recombinant tissue plasminogen activator (alteplase) as primary fibrinolytic drug in patients with acute STEMI in Buriram Hospital.

MATERIAL AND METHOD

Data on demographics, medications, in-hospital outcomes, and angiography were collected from a prospective registry of STEMI patients admitted by STEMI fast track from January 1, 2011 to December 31, 2013.

RESULTS

During the 3-year period, 97 consecutive patients with STEMI who received alteplase were enrolled. The mean age was 64.3 year and 75.3% were male. There were high prevalence of dyslipidemia and current smoking. Median time from symptom onset to hospital presentation was 170 minutes. Median door to needle time was 30 minutes. Thrombolytic therapy was started in 30 minutes in 55. 7% of cases. Overall bleeding was 19.6%. Intracranial hemorrhage was 1.0% of patients. ST-segment resolution was found in 79.4% of patients. In-hospital mortality was 11.3%. Angiographic data (n = 45) in patients with clinical reperfusion (n = 32), TIMI flow grade 2 and 3 combined was 90.6% and TIMI flow grade 3 was 56.3%. Revascularization was performed in 90.6%.

CONCLUSION

Alteplase in acute STEMI provided good clinical reperfusion with minimal major bleeding complication. Most of patients with clinical reperfusion required additional percutaneous coronary intervention to fix residual stenosis of infarct related artery.

[Research progress of Tbx3 in cardiac biological pacemaker]

The early cardiac biological pacemaker studies were mostly around HCN channel, and how to build a biological pacemaker through the enhanced If current. In recent years, however, people found that the genes of Tbx3 could play an important role in the development of cardiac conduction system, especially in processes of the maturity of the sinoatrial node and maintenance of its function. And the Tbx3 can further optimize the biological pacemaker. Therefore, it could be a new therapeutic focus in biological pacemaker and treatment of cardiac conduction system disease. This paper summarizes some of the latest research progress of the Tbx3 in biological pacemaker in recent years. We hope that this review could provide theoretical basis for the clinical applications of Tbx3.

Assessment of atrial conduction time in patients with polycystic ovary syndrome

BACKGROUND

Polycystic ovary syndrome (PCOS) is closely related to increased cardiovascular risk in women of reproductive age. Atrial conduction abnormalities in these patients have not been investigated in terms of atrial electromechanical delay measured by tissue Doppler imaging (TDI) as an early predictor of atrial fibrillation development. The aim of this study was to evaluate whether TDI-derived atrial conduction time is prolonged in PCOS.

METHODS

The study included 51 patients with PCOS and 48 age-matched healthy controls. P-wave dispersion (PWD) was calculated on the 12-lead surface electrocardiogram. Systolic and diastolic left ventricular (LV) functions, atrial electromechanical coupling, intraatrial and interatrial electromechanical delays were measured with conventional echocardiography and TDI.

RESULTS

PWD was higher in PCOS women (50.45 ± 3.7 vs 34.73 ± 6.7 ms, p = 0.008). Interatrial and intraatrial electromechanical delay were found longer in patients with PCOS compared to controls (41.9 ± 9.0 vs 22.2 ± 6.6 ms, p < 0.001; 22.6 ± 5.8 vs 5.9 ± 4.7 ms, p < 0.001, respectively). Left atrial (LA) volume index and LV diastolic parameters were significantly different between the groups. PWD was correlated with interatrial electromechanical delay (r = 0.54, p < 0.01). Interatrial electromechanical delay was strongly correlated with homeostatic model assessment insulin resistance index and high-sensitivity C-reactive protein levels (r = 0.68, p < 0.001; r = 0.53, p < 0.001, respectively). Interatrial electromechanical delay was positively correlated with LA volume index and deceleration time (r = 0.31, p = 0.04; r = 0.37, p = 0.021, respectively) and negatively correlated with flow propagation velocity (r = -0.38, p = 0.014).

CONCLUSION

This study shows that atrial electromechanical delay is prolonged in PCOS patients. Atrial electromechanical delay prolongation is related to low-grade inflammation, insulin resistance, and LV diastolic dysfunction in PCOS.

Relation of T-wave alternans to mortality and nonsustained ventricular tachycardia in patients with non-ST-segment elevation acute coronary syndrome from the MERLIN-TIMI 36 trial of ranolazine versus placebo

We explored the utility of T-wave alternans (TWA) in predicting mortality in patients with non-ST-segment elevation acute coronary syndrome (NSTEACS). Maximum TWA was calculated using Modified Moving Average method from continuous electrocardiographic recordings in patients with left ventricular ejection fraction <40% and ventricular tachycardia (VT) ≥4 beats during index hospitalization or sudden cardiac death during the follow-up year and age- and sex-matched controls in the Metabolic Efficiency with Ranolazine for Less Ischemia in Non-ST Elevation Acute Coronary Syndrome-Thrombolysis In Myocardial Infarction (MERLIN-TIMI) 36 trial. All patients received standard therapy for NSTEACS plus ranolazine (n = 109) or placebo (n = 101). Median follow-up was 1 year. Baseline clinical characteristics did not differ between patients with elevated TWA (≥47 μV) compared with lower levels. Patients with TWA ≥47 μV at admission had increased risk of total mortality (adjusted odds ratio [ORadj] 2.35, p = 0.04) during follow-up and VT ≥4 beats (ORadj 2.70, p = 0.01) during hospitalization with a trend toward increased cardiovascular death risk (ORadj 2.18, p = 0.07) during follow-up. In patients receiving placebo, TWA ≥47 μV on day 6 was associated with increased risk of total mortality (OR 4.12, 95% confidence interval 1.25 to 13.64, p = 0.02) and cardiovascular death (OR 4.73, p = 0.01) during follow-up. No deaths occurred among patients with TWA ≥47 μV assigned to ranolazine. In conclusion, in patients with NSTEACS and left ventricular ejection fraction <40%, TWA ≥47 μV early after admission is associated with increased risk of mortality at 1 year and with nonsustained VT during hospitalization. TWA may be useful in risk estimation in patients with NSTEACS. The possibility that TWA may serve as a therapeutic target deserves further exploration.

Early repolarization and myocardial scar predict poorest prognosis in patients with coronary artery disease

PURPOSE

Recent studies show positive association of early repolarization (ER) with the risk of life-threatening arrhythmias in patients with coronary artery disease (CAD). This study was to investigate the relationships of ER with myocardial scarring and prognosis in patients with CAD.

MATERIALS AND METHODS

Of 570 consecutive CAD patients, patients with and without ER were assigned to ER group (n=139) and no ER group (n=431), respectively. Myocardial scar was evaluated using cardiac single-photon emission computed tomography.

RESULTS

ER group had previous history of myocardial infarction (33% vs. 15%, p<0.001) and lower left ventricular ejection fraction (57±13% vs. 62±13%, p<0.001) more frequently than no-ER group. While 74 (53%) patients in ER group had myocardial scar, only 121 (28%) patients had in no-ER group (p<0.001). During follow up, 9 (7%) and 4 (0.9%) patients had cardiac events in ER and no-ER group, respectively (p=0.001). All patients with cardiac events had ER in inferior leads and horizontal/descending ST-segment. Patients with both ER in inferior leads and horizontal/descending ST variant and scar had an increased adjusted hazard ratio of cardiac events (hazard ratio 16.0; 95% confidence interval: 4.1 to 55.8; p<0.001).

CONCLUSION

ER in inferior leads with a horizontal/descending ST variant was associated with increased risk of cardiac events. These findings suggest that ER in patients with CAD may be related to myocardial scar rather than pure ion channel problem.

Early repolarisation and J wave syndromes

J wave syndrome has emerged as a significant cause of Idiopathic ventricular fibrillation (IVF) responsible for sudden cardiac death. A large body of data is now available on genesis, genetics and ionic mechanisms of J wave syndromes. Two of these viz., Early repolarization syndrome (ER) and Brugada syndrome (BrS) are fairly well characterized enabling correct diagnosis in most patients. The first part of repolarization of ventricular myocardium is governed by Ito current i.e., rapid outward potassium current. The proposed mechanism of ventricular fibrillation (VF) and ventricular tachycardia (VT) storms is the faster Ito current in the epicardium than in the endocardium results in electrical gradient that forms the substrate for phase 2 reentry. Prevention of Ito current with quinidine supports this mechanism. Majority of ER patterns in young patients are benign. The key issue is to identify those at increased risk of sudden cardiac death. Association of both ER syndrome and Brugada syndrome with other disease states like coronary artery disease has also been reported. Individuals resuscitated from VF definitely need an implantable cardiac defibrillator (ICD) but in others there is no consensus regarding therapy. Role of electrophysiology study to provoke ventricular tachycardia or fibrillation is not yet well defined. Radiofrequency ablation of epicardial substrate in right ventricle in Brugada syndrome is also under critical evaluation. In this review we shall discuss historical features, epidemiology, electrocardiographic features, ionic pathogenesis, clinical features and current status of proposed treatment of ER and BrS.

[Value of admission electrocardiogram for predicting multivessel disease in acute anterior and anterior-inferior myocardial infarction]

OBJECTIVE

The correlation between admission Electrocardiogram (ECG) and coronary angiography findings have the responsibility for culprit vessel in predicting the infarct or multivessel disease (MVD) in acute anterior or anterior-inferior ST segment elevation myocardial infarction.

METHODS

Between 2012 January and 2012 December, in Emergency Department Beijing Anzhen Hospital, Concessive 203 patients were retrospective investigated with the diagnosis of anterior AMI (ASTEMI) with or without ST-segment elevation or ST-segment depression in at least two leads in II, III, aVF. Patients are categoried in 3 groups by ECG (1) ASTEMI with inferior depressions, (2) ASTEMI with inferior elevations,(3) all ASTEMI according to the ST-segment changes in the inferior region were analyzed by the presence of LAD (SLAD) or multivessles involvement.

RESULTS

The ST-segment depression in aVL and V6 significantly correlated with MVD in ASTEMI patients with whose reciprocal changes in the inferior leads (P = 0.004 and P = 0.031, respectively). The analyse of all the patients with ASTEMI, the association between the presence of MVD and ST-segment depression in leads aVL,V4,V5 and V6 is significant (P = 0.041, P = 0.012, P = 0.014, P = 0.001, respectively).

CONCLUSIONS

In the admission ECG, ST-segment depression in anterolateral leads of anterior AMI patients who with reciprocal changes in inferior leads were associated with MVD.

Clinical characteristics and outcomes associated with the natural history of early repolarization in a young, biracial cohort followed to middle age: the Coronary Artery Risk Development in Young Adults (CARDIA) study

BACKGROUND

Early repolarization (ER), a common electrocardiographic phenotype, has been associated with increased mortality risk in middle-aged adults. Data are sparse on long-term follow-up and outcomes associated with ER in younger adults.

METHODS AND RESULTS

We prospectively examined 5039 participants (mean age, 25 years at baseline, 40% black) from the Coronary Artery Disease Risk in Adults (CARDIA) cohort for 23 years. Twelve-lead ECGs were recorded and analyzed at years 0, 7, and 20 and coded as definite or probable ER using a standardized algorithm. Cox regression was used, and models were adjusted for important baseline and clinical covariates. Kaplan-Meier curves were created for presence of ER and total mortality and cardiovascular mortality. Participants with ER were more likely to be black, male, smoke, have higher systolic blood pressure, lower heart rate and body mass index, higher exercise duration, and longer PR, QRS, and QT intervals. ER was associated with total mortality (hazard ratio, 1.77; confidence interval, 1.38-2.28; P<0.01) and cardiovascular mortality (hazard ratio, 1.59; confidence interval, 1.01-2.50; P=0.04) in unadjusted analyses, but adjustment for age, sex, and race attenuated associations almost completely. Sex-race stratified analyses showed no significant associations between ER and outcome for any of the subgroups except blacks.

CONCLUSIONS

The presence of ER at any time point during 23 years of follow-up was not associated with adverse outcomes. Black race and male sex confound the unadjusted association of ER and outcomes, with no race-sex interactions noted. Additional studies are necessary to understand the factors associated with heightened risk of death in those who maintain ER into and beyond middle age.

Evaluation of cardiac functions and atrial electromechanical delay in children with adenotonsillar hypertrophy

Deterioration of the right ventricular (RV) functions and the increase in the pulmonary arterial pressure (PAP) of children with moderate to severe adenotonsillar hypertrophy (ATH) have been well described. In addition to these complications, this study aimed to investigate the influence of ATH on the conduction system. The study investigated 46 patients with a diagnosis of ATH and 46 healthy control subjects. Conventional echocardiography, P-wave dispersion (Pd), tissue Doppler imaging (TDI) findings, and atrial electromechanical delay (AED) were compared between the patients and the control subjects before and after adenotonsillectomy. The maximum P-wave duration and Pd were significantly higher in the patients than in the control subjects (p < 0.001). The patient group showed significantly greater RV end-diastolic dimension (p = 0.01), right atrial area (p < 0.001), and mean PAP (p = 0.03) but lower E/A ratios for the mitral (p = 0.04) and tricuspid (p = 0.01) valves and a shorter pulmonary flow trace acceleration time (p = 0.03). The tricuspid annular-plane systolic excursion was similar between these groups (p = 0.21). In the patient group, TDI studies showed significantly lower E'/A' ratios for the tricuspid lateral (p = 0.006) and mitral septal (p = 0.003) segments than in the control group. The myocardial performance index was lower for the mitral lateral, mitral septal, and tricuspid lateral segments in patient group (p < 0.001). Similarly, AED was prolonged in the patient group at all three segments (p < 0.001). Also, the patient group showed a significantly longer interatrial (p = 0.03) and intraatrial (p = 0.04) electromechanical delay. However, all the electro- and echocardiographic parameters were similar between the patients and the control subjects after adenotonsillectomy (p > 0.05). The prolongations in P-wave duration, Pd, and inter- and intraatrial electromechanical delays were first shown in this population. The cardiac changes induced by ATH-associated hypoxia may facilitate arrhythmias during the long term.

Outcomes of straightforward extracardiac Fontan operation in advanced-age group

INTRODUCTION

Fontan operation is a palliative procedure used in patients with univentricular heart (UVH). There have been numerous modifications to the technique. The appropriate strategy for treating patients with UVH in Thailand is still a major concern.

OBJECTIVE

To describe the outcomes of patients after straightforward Fontan operation at advanced-age and evaluate their post-surgical cardiac performance.

MATERIAL AND METHOD

A cross sectional study was performed in post-Fontan operation patients at Rajvithi Hospital between 2000 and 2009. Post-operative cardiac performance was analyzed using the echocardiogram and treadmill exercise stress test (EST).

RESULTS

Thirty-nine patients were enrolled in the present study. The mean age was 11.7 years and the mean age at operation was 7.4 years. The predominant systemic chamber was morphologic left ventricle. Straightforward Fontan operation was performed in 60% of cases. Mean of Fontan index, mean of McGoon ratio, and mean of Nakata index were 2.63, 2.32, and 414.15 sqmm/sqm, respectively. Mean of the PVR and PAP were 1.98 U/m2 and 11.05 mmHg. Eighteen percent of patients died in the early post-operative period. Most of the patients died from septicemia. The mean EFwas 58.43%. Systolic dysfunction in 17.9% of the cases was abnormal, whereas diastolic dysfunction was present in half of the cases. Thirty-nine percent had MPI abnormality. During EST three cases developed arrhythmias and 3 cases had hypotension. Patients were categorized into 3 groups (Group 1: normal systolic and diastolic functions, Group 2: diastolic dysfunction, Group 3: impairment of both systole and diastole). Pre-operative cardiac catheterization parameters, surgical data and cardiac performance showed no statistical significance. However, there was a significant correlation between those with abnormal cardiac performance and arrhythmias or hypotension during EST (p = 0.003).

CONCLUSION

The selection of suitable cases and good pre-operative evaluation could decrease the morbidity and mortality in patients undergoing the Fontan procedure. This study also found a correlation between abnormal cardiac performance and transient cardiac arrhythmia during exercise. The evaluation of cardiac performance and EST remains to be performed for following-up of patients who have undergone the Fontan operation, even for the asymptomatic cases.

Heart rate-corrected QT interval is an independent predictor of all-cause and cardiovascular mortality in individuals with type 2 diabetes: the Diabetes Heart Study

OBJECTIVE

Heart rate-corrected QT (QTc) interval is associated with mortality in the general population, but this association is less clear in individuals with type 2 diabetes. We assessed the association of QTc interval with all-cause and cardiovascular disease (CVD) mortality in the Diabetes Heart Study.

RESEARCH DESIGN AND METHODS

We studied 1,020 participants with type 2 diabetes (83% European Americans; 55% women; mean age 61.4 years) who were free of atrial fibrillation, major ventricular conduction defects, and antiarrhythmic therapy at baseline. QT duration was automatically calculated from a standard 12-lead electrocardiogram (ECG). Following American Heart Association/American College of Cardiology Foundation recommendations, a linear scale was used to correct the QT for heart rate. Using Cox regression, risk was estimated per 1-SD increase in QTc interval as well as prolonged QTc interval (>450 ms) vs. normal QTc interval for mortality.

RESULTS

At baseline, the mean (SD) QTc duration was 414.9 ms (18.1), and 3.0% of participants had prolonged QTc. After a median follow-up time of 8.5 years (maximum follow-up time 13.9 years), 204 participants were deceased. In adjusted multivariate models, a 1-SD increase in QTc interval was associated with an 18% higher risk for all-cause mortality (hazard ratio 1.18 [95% CI 1.03-1.36]) and 29% increased risk for CVD mortality (1.29 [1.05-1.59]). Similar results were obtained when QTc interval was used as a categorical variable (prolonged vs. normal) (all-cause mortality 1.73 [0.95-3.15]; CVD mortality 2.86 [1.35-6.08]).

CONCLUSIONS

Heart rate QTc interval is an independent predictor of all-cause and CVD mortality in this population with type 2 diabetes, suggesting that additional prognostic information may be available from this simple ECG measure.

The relationship between J wave on the surface electrocardiography and ventricular fibrillation during acute myocardial infarction

We investigated whether the presence of J wave on the surface electrocardiography (sECG) could be a potential risk factor for ventricular fibrillation (VF) during acute myocardial infarction (AMI). We performed a retrospective study of 317 patients diagnosed with AMI in a single center from 2009 to 2012. Among the enrolled 296 patients, 22 (13.5%) patients were selected as a VF group. The J wave on the sECG was defined as a J point elevation manifested through QRS notching or slurring at least 1 mm above the baseline in at least two leads. We found that the incidence of J wave on the sECG was significantly higher in the VF group. We also confirmed that several conventional risk factors of VF were significantly related to VF during AMI; time delays from the onset of chest pain, blood concentrations of creatine phosphokinase and incidence of ST-segment elevation. Multiple logistic regression analysis demonstrated that the presence of J wave and the presence of a ST-segment elevation were independent predictors of VF during AMI. This study demonstrated that the presence of J wave on the sECG is significantly related to VF during AMI.

[Optical coherence tomography, delayed stent implantation and primary percutaneous coronary intervention in patients with myocardial infarction and ST segment elevation]

Primary percutaneous coronary intervention (PCI) is an effective treatment for myocardial infarction with ST-segment elevation. However, the stent may slow (slow-flow) or even interrupt the flow (no-reflow) in the infarct-related artery with an increase in short-term and long-term mortality. Due to these limitations there is an effort to search for alternative methods or certain modifications of existing PCI. Present article introduces a modified PCI and results of trombo-aspiration technique by optical coherence tomography (OCT). The article presents the results of our clinical study and brief case report. Our pilot project involved 100 patients with STEMI in 2011-2012. 20 patients (20%) were initially treated only with trombo-aspiration without stent implantation, based on OCT. Control angiography and OCT done 9 months after event have revealed insignificant stenosis in all patients. It is plausible that universal medical procedure with stenting is not suitable for all patients with STEMI and especially patients with large thrombus may benefit from the alternative procedure performed by manually trombo-aspiration technique with intensive anticoagulant/antiaggregant therapy. Nevertheless, only randomized trials with sufficiently follow-up may confirm this hypothesis.

A long QT mutation substitutes cholesterol for phosphatidylinositol-4,5-bisphosphate in KCNQ1 channel regulation

Introduction

Phosphatidylinositol-4,5-bisphosphate (PIP₂) is a cofactor necessary for the activity of KCNQ1 channels. Some Long QT mutations of KCNQ1, including R243H, R539W and R555C have been shown to decrease KCNQ1 interaction with PIP₂. A previous study suggested that R539W is paradoxically less sensitive to intracellular magnesium inhibition than the WT channel, despite a decreased interaction with PIP₂. In the present study, we confirm this peculiar behavior of R539W and suggest a molecular mechanism underlying it.

Methods and Results

COS-7 cells were transfected with WT or mutated KCNE1-KCNQ1 channel, and patch-clamp recordings were performed in giant-patch, permeabilized-patch or ruptured-patch configuration. Similar to other channels with a decreased PIP₂ affinity, we observed that the R243H and R555C mutations lead to an accelerated current rundown when membrane PIP₂ levels are decreasing. As opposed to R243H and R555C mutants, R539W is not more but rather less sensitive to PIP₂ decrease than the WT channel. A molecular model of a fragment of the KCNQ1 C-terminus and the membrane bilayer suggested that a potential novel interaction of R539W with cholesterol stabilizes the channel opening and hence prevents rundown upon PIP₂ depletion. We then carried out the same rundown experiments under cholesterol depletion and observed an accelerated R539W rundown that is consistent with this model.

Conclusions

We show for the first time that a mutation may shift the channel interaction with PIP₂ to a preference for cholesterol. This de novo interaction wanes the sensitivity to PIP₂ variations, showing that a mutated channel with a decreased affinity to PIP₂ could paradoxically present a slowed current rundown compared to the WT channel. This suggests that caution is required when using measurements of current rundown as an indicator to compare WT and mutant channel PIP₂ sensitivity.

[Myotonia and cardiac conduction defects in myotonic dystrophy and defect in ion channels]

Myotonic dystrophy (DM), the most common hereditary muscle disease in adults, is caused by the unstable genomic expansion of simple sequence repeats. This disease is characterized by myotonia and various multisystemic complications, most commonly those of the cardiac, endocrine, and central nervous systems. The cardiac abnormalities, especially cardiac conduction defects, significantly contribute to morbidity and mortality in DM patients. Therefore, understanding the pathophysiology of cardiac conduction defects in DM is important. The pathomechanism of DM has been thoroughly investigated. The mutant RNA transcripts containing the expanded repeat give rise to a toxic gain-of-function by perturbing splicing factors in the nucleus, leading to the misregulation of alternative pre-mRNA splicing. In particular, several studies, including ours, have shown that myotonia is caused by alternative splicing of the CLCN1 gene coding the voltage-gated chloride channel in skeletal muscle through an "RNA-dominant mechanism". Since the aberrantly spliced isoform does not seem to form a functional channel, the feature of skeletal muscle in DM can be interpreted as a "channelopathy" caused by reduced chloride channel protein. Similarly, we recently identified a misregulation of alternative splicing in an ion channel gene which is known to be responsible for arrhythmic disease showing Mendelian inheritance. Here, we review the cardiac manifestation and RNA-dominant mechanism of DM, and discuss the possible pathophysiology of cardiac conduction defects by referring to hereditary arrhythmic diseases, such as long QT syndrome and Brugada syndrome.

Connexin defects underlie arrhythmogenic right ventricular cardiomyopathy in a novel mouse model

Arrhythmogenic right ventricular cardiomyopathy (ARVC) termed a 'disease of the desmosome' is an inherited cardiomyopathy that recently underwent reclassification owing to the identification of left-dominant and biventricular disease forms. Homozygous loss-of-function mutations in the desmosomal component, desmoplakin, are found in patients exhibiting a biventricular form of ARVC; however, no models recapitulate the postnatal hallmarks of the disease as seen in these patients. To gain insights into the homozygous loss-of-function effects of desmoplakin in the heart, we generated cardiomyocyte-specific desmoplakin-deficient mice (DSP-cKO) using ventricular myosin light chain-2-Cre mice. Homozygous DSP-cKO mice are viable but display early ultrastructural defects in desmosomal integrity leading to a cardiomyopathy reminiscent of a biventricular form of ARVC, which includes cell death and fibro-fatty replacement within the ventricle leading to biventricular dysfunction, failure and premature death. DSP-cKO mice also exhibited ventricular arrhythmias that are exacerbated with exercise and catecholamine stimulation. Furthermore, DSP-cKO hearts exhibited right ventricular conduction defects associated with loss of connexin 40 expression and electrical wavefront propagation defects associated with loss of connexin 43 expression. Dose-dependent assessment of the effects of loss of desmoplakin in neonatal ventricular cardiomyocytes revealed primary loss of connexin 43 levels, phosphorylation and function independent of the molecular dissociation of the mechanical junction complex and fibro-fatty manifestation associated with ARVC, suggesting a role for desmoplakin as a primary stabilizer of connexin integrity. In summary, we provide evidence for a novel mouse model, which is reminiscent of the postnatal onset of ARVC while highlighting mechanisms underlying a biventricular form of human ARVC.