Catheter ablation versus antiarrhythmic drug therapy for sustained ventricular tachycardia in patients with hypertrophic cardiomyopathy.

BACKGROUND: Ventricular tachycardia (VT) is the primary cause of sudden cardiac death in patients with hypertrophic cardiomyopathy (HCM). However, the strategy for VT treatment in HCM patients remains unclear. This study is aimed to compare the effectiveness of catheter ablation versus antiarrhythmic drug (AAD) therapy for sustained VT in patients with HCM. METHODS: A total of 28 HCM patients with sustained VT at 4 different centers between December 2012 and December 2021 were enrolled. Twelve underwent catheter ablation (ablation group) and sixteen received AAD therapy (AAD group). The primary outcome was VT recurrence during follow-up. RESULTS: Baseline characteristics were comparable between two groups. After a mean follow-up of 31.4 ± 17.5 months, the primary outcome occurred in 35.7% of the ablation group and 90.6% of the AAD group (hazard ratio [HR], 0.29 [95%CI, 0.10-0.89]; P = 0.021). No differences in hospital admission due to cardiovascular cause (25.0% vs. 71.0%; P = 0.138) and cardiovascular cause-related mortality/heart transplantation (9.1% vs. 50.6%; P = 0.551) were observed. However, there was a significant reduction in the composite endpoint of VT recurrence, hospital admission due to cardiovascular cause, cardiovascular cause-related mortality, or heart transplantation in ablation group as compared to that of AAD group (42.9% vs. 93.7%; HR, 0.34 [95% CI, 0.12-0.95]; P = 0.029). CONCLUSIONS: In HCM patients with sustained VT, catheter ablation reduced the VT recurrence, and the composite endpoint of VT recurrence, hospital admission due to cardiovascular cause, cardiovascular cause-related mortality, or heart transplantation as compared to AAD.

Scar-related atrial macroreentries: Different arrhymogenic basis generates different reentry type.

BACKGROUND: Catheter ablation is an established therapeutic strategy to treat scar-related macroreentry atrial tachycardia (MAT). However, the scar properties and arrhythmogenicity and the reentry type have not been clearly defined. METHODS AND RESULTS: A total of 122 patients with scar-related MAT were enrolled in this study. The atrial scars were classified into two categories: spontaneous scars (Group A: n = 28) and iatrogenic scars (Group B: n = 94). According to the relationship between scar location and the reentry circuit, MAT was described as scar pro-flutter MAT, scar-dependent MAT, and scar-mediated MAT. The reentry type of MAT was significantly different between Groups A and B: pro-flutter (40.5% vs. 62.0%, p = 0.02), scar-dependent AT (40.5% vs. 13.0%, p < 0.001), and scar-mediated AT (19.0% vs. 25.0%, p = 0.42). After a median follow-up of 25 months, 21 patients with AT recurrence were observed. Compared with the spontaneous group, there was a lower recurrence rate of MAT in the iatrogenic group (28.6% vs. 10.6%, p = 0.03). CONCLUSION: Scar-related MAT has three reentry types, and the proportion of each type varies with the scar properties and its arrhythmogenic basis. Optimization of the ablation strategy based on the scar properties to improve the long-term outcome of catheter ablation of MAT is necessary.

Bipolar catheter ablation strategies for outflow tract ventricular arrhythmias refractory to unipolar ablation.

INTRODUCTION: Conventional unipolar catheter ablation (UA) is generally effective for the treatment of outflow tract ventricular arrhythmias (OT-VAs). However, deep foci refractory to UA remains a clinical challenge. The present study evaluated the efficacy and safety of bipolar ablation (BA) in the treatment of OT-VAs refractory to UA. METHODS: A total of 1022 consecutive patients with antiarrhythmic drugs resistant OT-VAs were screened for inclusion in this study, from 1643 VAs cases who underwent catheter ablation in two centers from October 2014 to May 2019. BA was performed after failed sequential UA. The pair of catheters used for BA was positioned on opposing surfaces of the earliest activation (EA) sites or on adjacent anatomical structures. RESULTS: Twelve patients (seven males, mean age 33.3 ± 16.2 years) who met the inclusion criteria were recruited: one patient suffered sustained monomorphic ventricular tachycardia (VT), six patients had frequent premature ventricular contractions (PVCs), and nonsustained VT (NSVT), and five patients had PVCs only. The 24-hPVC/NSVT burden was 36.9 ± 21.7%. The mean distance between two ablation catheters during BA was 11.1 ± 4.3 mm (range 6.5-23.9 mm). The "rS" morphology of the unipolar electrogram was recorded simultaneously in both EA regions in seven cases (58.3%). Acute eradication of VAs was obtained in 10 (83.3%) cases. At a median follow-up of 58 months, 10 patients (83.3%) remained free from VAs. CONCLUSION: BA was highly effective and safe for the treatment of OT-VAs refractory to UA.

A novel mutation in KCNH2 yields loss-of-function of hERG potassium channel in long QT syndrome 2.

Mutations in hERG (human ether-à-go-go-related gene) potassium channel are closely associated with long QT syndromes. By direct Sanger sequencing, we identified a novel KCNH2 mutation W410R in the patient with long QT syndrome 2 (LQT2). However, the electrophysiological functions of this mutation remain unknown. In comparison to hERGWT channels, hERGW410R channels have markedly decreased total and surface expressions. W410R mutation dramatically reduces hERG channel currents (IKr) and shifts its steady-state activation curve to depolarization. Moreover, hERGW410R channels make dominant-negative effects on hERGWT channels. Significantly, we find hERG channel blocker E-4031 could partially rescue the function of hERGW410R channels by increasing the membrane expression. By using in silico model, we reveal that hERGW410R channels obviously elongate the repolarization of human ventricular myocyte action potentials. Collectively, W410R mutation decreases the currents of hERG channel, because of diminished membrane expression of mutant channels, that subsequently leads to elongated repolarization of cardiomyocyte, which might induce the pathogenesis of LQT2. Furthermore, E-4031 could partially rescue the decreased activity of hERGW410R channels. Thus, our work identifies a novel loss-of-function mutation in KCNH2 gene, which might provide a rational basis for the management of LQT2.

Atrial electromechanical delay assessment in early phase after catheter ablation for patients with atrial fibrillation.

BACKGROUND: Variation of atrial electromechanical delay (AED) in early phase after catheter ablation in patients with atrial fibrillation (AF) is lacking. METHODS: Fifty-five consecutive patients restored sinus rhythm after ablation was included. Echocardiography was performed at 4 h, 1 day, and 3 days after radiofrequency catheter ablation, and AED was measured simultaneously by echocardiography with pulse Doppler imaging and pulse wave tissue Doppler imaging. RESULTS: AED parameters were significantly longer in the nonparoxysmal atrial fibrillation (NPAF) group than in the paroxysmal atrial fibrillation (PAF) group at each checking point after ablation (P < 0.05). Compared with other checking points, AED parameters were significantly longer 4 h postablation in the NPAF group, while no significant difference was found between different checking points in the PAF group. AED-leap, representing the variation of AED in NPAF patients, was significantly positively correlated with the duration of NPAF (r = 0.5291, P = 0.0113). CONCLUSIONS: Compared with PAF, NPAF patients have a longer AED postablation, and an abrupt decrease in the initial-h postablation. Such phenomenon gives rise to the different clinical features of PAF and NPAF, and could guide different assessment and treatment strategies for different types of AF.

Idiopathic isolated fibrotic atrial cardiomyopathy underlies unexplained scar-related atrial tachycardia in younger patients.

Aims: Unexplained scar-related atrial tachycardia (AT) has been frequently encountered in clinical practice. We hypothesized that idiopathic, isolated fibrotic atrial cardiomyopathy (ACM) underlies this rhythm disorder. This study was aimed to characterize the underlying substrate and to explore the aetiology of this unexplained scar-related AT. Methods and results: Twenty-six (11 men, aged 46 ± 13 years) of 52 non-surgical scar-related AT patients identified by three-dimensional voltage mapping were enrolled in this prospective observational study. Multimodality image examinations (echocardiography, cardiac magnetic resonance, 99Tc single-photon emission computed tomography), ventricular voltage mapping, and intracardiac pressure curve recording ruled out ventricular involvement. Catheter ablation was acutely successful for all the patients, and pacemaker implantation was performed in seven patients who presented sinus node dysfunction or atrial standstill after termination of the AT. In three patients with multiple AT recurrences, the diseased areas of the right atrium were resected and dechannelled via mini-invasive surgical interventions. Histological examinations revealed profound fibrosis without amyloidosis or adipose deposition. Viral and familial investigations yielded negative results. Fibrosis progression over a median of 45 (5-109) months of follow-up manifested as atrial arrhythmia recurrence in seven patients and atrial lead non-capture due to newly developed atrial standstill in two patients. Two patients suffered four ischaemic stroke events before receiving anticoagulation treatment. Conclusion: Isolated, fibrotic ACM may underlie the idiopathic scar-related ATs. This novel cardiomyopathy has unique clinical characteristics with high morbidity including stroke and warrants specific therapeutic strategies. Further investigations are required to determine the aetiology and mechanism.

Substrate characteristics and ablation outcome of left atrial tachycardia in rheumatic mitral valve disease.

BACKGROUND: Right atrial tachycardia (AT) is a common arrhythmia postsurgical valve replacement in patients with rheumatic heart disease (RHD). However, the substrate and the mechanism of left AT in such patients and the ablation efficacy is less known. METHODS AND RESULTS: Twenty-seven RHD patients with AT were enrolled in this study; nine of them (33%) had left AT. Five and four patients had left AT during the first and second procedure, respectively. A spontaneous scar in the left posterior wall was identified in all patients, and obvious anterior scar in three patients. Dual-roof-dependent AT was found in three patients and macroreentry AT surrounding right pulmonary vein was identified in one patient, two of whom had left anterior scar. Three patients had AT circuit going around the mitral annulus, one of whom had left anterior scar. Entrainment pacing at different sites confirmed the mechanism of these macroreentries. Two patients had a focal origin, one was localized in posterior wall at the edge of the scar and the other one was originated from the left septum with normal voltage. After a mean follow-up of 27.4 ± 7.9 months, the left AT group had a similar recurrence rate compared with the right AT group alone (67% vs 56%, P = 0.58). In the left AT group, 11% of patients had AT recurrence and 56% of patients developed atrial fibrillation. CONCLUSION: Left atrial AT can occur in RHD patients postmitral valve replacement. Catheter ablation is feasible with high acute success rate. The incidence of late development atrial fibrillation is considerable after successful ablation.

Effect of Metoprolol Succinate in Patients with Stable Angina and Elevated Heart Rate Receiving Low-Dose ß-Blocker Therapy.

Aims: ß-blockers are underused in Chinese patients with coronary heart disease. The prescribed dose is often low. The aim of this study was to investigate the effect of metoprolol succinate doses of 95 mg and 190 mg on heart rate (HR) control, as well as drug tolerance, in Chinese patients with stable angina, low-dose ß-blocker use and unsatisfactory HR control. Methods: This was a multicenter, randomized, open-label, parallel-group trial in 15 clinical sites. Patients with stable angina, taking low-dose ß-blockers (equivalent to metoprolol succinate 23.75-47.5 mg/day), and having a resting HR of ≥ 65 bpm were enrolled and randomized to either the metoprolol 95-mg group or the 190-mg group. The change in 24-h average HR from baseline recorded by Holter monitoring and the percentages of patients with resting HR controlled to ≤ 60 bpm were compared between the two groups. Results: Two hundred thirty-one patients entered the intent-to-treat population for the main analysis. The change in 24-h average HR from baseline was -0.62 ± 0.66 bpm in the 95 mg group and -2.99 ± 0.62 bpm in the 190 mg group (p = 0.0077) after 8 weeks of treatment. The percentages of patients with resting HR controlled to ≤ 60 bpm were 24.1% (95% CI: 16.35%, 31.93%) and 40.0% (95% CI: 31.05%, 48.95%), respectively (p = 0.0019). Only 4 and 2 of the patients, respectively, discontinued the study drugs because of hypotension or bradycardia. Conclusions: The metoprolol succinate dose of 190 mg is superior to the 95 mg dose in terms of HR control, in Chinese patients with stable angina, low-dose ß-blocker use and unsatisfactory HR control. Both doses were well tolerated.

Non-contact mapping-guided ablation of ventricular arrhythmias originating from the pulmonary artery.

AIMS: To identify unique electrophysiological characteristics of pulmonary artery (PA) ventricular arrhythmias (VA) and determine long-term clinical outcomes following non-contact mapping (NCM)-guided ablation. METHODS AND RESULTS: The NCM array was deployed in consecutive patients undergoing clinically indicated ablation of outflow tract (OT) VA with left bundle branch block morphology, inferior axis and the precordial lead transition zone ≥ V3. Activation, pace and NCM mapping parameters, and electrocardiogram analysis of PA VA patients were compared with 50 patients with right ventricular OT (RVOT) or aortic coronary cusps (ACC) foci. Of 170 consecutive patients, 20 (12%) patients (8 male, 39.7 ± 12.8 years old) with PA VA were identified. Electrocardiogram morphologies of PA ventricular tachycardia (VT) (located 10.8 ± 15.1 mm above the PV) were indistinguishable from RVOT VT, particularly those arising from the septal RVOT. Pulmonary artery VT can be mapped and ablated by targeting the site of earliest activation on NCM maps, with success rates of 90% after a single procedure, without anti-arrhythmics and mean follow-up of >5 years. Pace-mapping in the PA is complicated by frequent inability to capture (P < 0.01). Small far-field atrial potentials and smaller ventricular electrograms were more frequently recorded at successful sites of ablation in the PA (P < 0.05). CONCLUSION: Non-contact mapping is a useful technique to map PA VT and ablation at sites of earliest activation above the pulmonary valve is associated with excellent long-term clinical success.

China's research status in emergency medicine: a 15-year survey of literature.

OBJECTIVES: To investigate the research status of emergency medicine in China through literature search of international emergency medicine journals and retrospectively compare the outputs of emergency medicine articles of the 3 major regions of China-Mainland (ML), Taiwan (TW), and Hong Kong (HK). METHODS: Emergency medicine journals were selected category from Science Citation Index Expand. Articles from the ML, TW, and HK were retrieved from PubMed database. The total number of articles, publication types, research contents, impact factors (IF), and articles published in each journal were conducted for quantity and quality comparisons. RESULTS: A total of 1760 articles from 19 emergency medicine journals were searched, of which 395 were from ML, 1210 from TW, and 155 from HK. Accumulated IF of articles from TW (2451.109) was much higher than that of ML (851.832) and HK (328.579), whereas the average IF of articles from TW (2.02) was the lowest. The number of case reports was the highest, which was, 69 from ML, 637 from TW, and 25 from HK, respectively. Although emergency medicine was involved with multiple organs and multiple systems, the reports of trauma accounted for 25% of the research contents. CONCLUSIONS: The total number of articles from both China and the rest of the world increased significantly from 2000 to 2014, especially ML. The total number of articles from TW was still much more than that of ML and HK, whereas the quality of articles from TW was not as good as ML and HK. Case report had the highest share of publication types, whereas the proportions of meta-analysis and observational study were the lowest. As for research contents, the proportion of trauma was still the highest.

[Contribution of atrial activation to the segment of the typical atrial flutter wave: an electro-anatomic insight into the electrocardiogram morphology].

OBJECTIVE: To investigate how the intra-cardiac activation was translates into the characterized flutter wave in patients with cavatricuspid isthmus-dependent counter-clockwise atrial flutter (CTI-AFL). METHODS: A total of 15 hospitalized CTI-AFL patients (mean age: (60 ± 14) years old, 1 female) from October 2012 to February 2014 were enrolled in the study. The activation map was re-constructed during AFL rhythm for left atrium and right atrium using 3-dimensional mapping system. The flutter wave in surface electrocardiogram was analyzed in combination with the intra-cardiac activation. RESULTS: The mean left ventricular ejection fraction was (60.8 ± 6.6)%, and the left atrial diameter was (39.0 ± 3.4) mm. The mean tachycardia cycle length was (220 ± 24) ms. The activation map was completed in all cases. In inferior leads, the flutter wave was divided into three parts: slowly downward part, sharp downward part and the terminal positive part. The three parts corresponded to the fixed activation part of the macro-reentry. CONCLUSION: The distinctive flutter wave of CTI-AFL was determined by the unique macro-reentry activation in the right atrium. The activation of left atrium contributes to the downward part of the wave.

Transplantation of iPSc ameliorates neural remodeling and reduces ventricular arrhythmias in a post-infarcted swine model.

Neural remodeling after myocardial infarction (MI) may cause malignant ventricular arrhythmia, which is the main cause of sudden cardiac death following MI. Herein, we aimed to examine whether induced pluripotent stem cells (iPSc) transplantation can ameliorate neural remodeling and reduce ventricular arrhythmias (VA) in a post-infarcted swine model. Left anterior descending coronary arteries were balloon-occluded to generate MI. Animals were then divided into Sham, PBS control, and iPS groups. Dynamic electrocardiography programmed electric stimulation were performed to evaluate VA. The spatial distribution of vascularization, Cx43 and autonomic nerve regeneration were evaluated by immunofluorescence staining. Associated protein expression was detected by Western blotting. Likewise, we measured the enzymatic activities of superoxide dismutase and content of malondialdehyde. Six weeks later, the number of blood vessels increased significantly in the iPSc group. The expression of vascular endothelial growth factor and connexin 43 in the iPS group was significantly higher than the PBS group; however, the levels of nerve growth factor and tyrosine hydroxylase were lower. The oxidative stress was ameliorated by iPSc transplantation. Moreover, the number of sympathetic nerves in the iPSc group was reduced, while the parasympathetic nerve fibers had no obvious change. The transplantation of iPSc also significantly decreased the low-/high-frequency ratio and arrhythmia score of programmed electric stimulation-induced VA. In conclusion, iPSc intramyocardial transplantation reduces vulnerability to VAs, and the mechanism was related to the remodeling amelioration of autonomic nerves and gap junctions. Moreover, possible mechanisms of iPSc transplantation in improving neural remodeling may be related to attenuated oxidative stress and inflammatory response.

Tachycardiomyopathy complicated by focal atrial tachycardia: incidence, risk factors, and long-term outcome.

OBJECTIVE: Focal atrial tachycardias (ATs) are known to have the potential to develop tachycardiomyopathy (TCM). The aim of the study was to investigate the incidence, risk factors, and long-term outcome of TCM patients complicated by focal ATs. METHODS AND RESULTS: A total of 237 patients undergoing electrophysiological studies were enrolled, among which 216 patients were diagnosed as focal ATs. In total, 18 patients (8.3%, 13 males) were identified to have TCM. The TCM patients were younger (29.8 ± 20.1 vs. 45.9 ± 17.3; P < 0.000) and were more frequently males (13/18 vs. 80/198; P = 0.014). The ATs were more likely to be persistent (11/18 vs. 32/198; P < 0.001). There was no difference between the 2 groups in terms of the tachycardia cycle length (392 milliseconds vs. 380 milliseconds; P = 0.56) and heart rate (144 bpm vs. 156 bpm; P = 0.15). The persistence and incidence of symptoms and prevalence of structural heart disease were comparable between the groups. In a multivariable analysis, the younger age and persistent nature were independently associated with TCM. In a 56 ± 21-month follow-up, all TCM patients had improved left ventricle ejection fraction after successful catheter ablation or medical therapy (43.9 ± 5.8% vs. 61.1 ± 3.5%; P ＜ 0.05). However, 1 patient suffered sudden cardiac death due to unauthorized withdrawal of the drug and progressive heart failure. CONCLUSIONS: The incidence of TCM in focal ATs patients was 8.3%. Younger age and persistent nature were the independent risk factors of TCM. Most TCM patients had a benign outcome; however, long-term risk of sudden death does exist.

The acute and chronic effects of different right ventricular site pacing on left ventricular mechanical synchrony as assessed by phase analysis of SPECT myocardial perfusion imaging.

BACKGROUND: This study aimed to assess acute and chronic effects of right ventricular mid-septum (RVS) versus right ventricular apex (RVA) pacing on left ventricular (LV) mechanical dyssynchrony using phase analysis of gated single photon emission computed tomography myocardial perfusion imaging (MPI). METHODS: Thirty-nine patients with complete atrioventricular (AV) block, who were indicated for permanent pacing, were recruited and randomized to receive RVA (n = 20) or RVS (n = 19) pacing. All patients underwent MPI at 1 week and 6 months after pacemaker implantation. LV dyssynchrony and cardiac function were assessed by MPI and compared between the two groups. RESULTS: There were no significant differences in baseline characteristics between the RVS and RVA groups. The paced QRS duration was significantly longer in the RVA group than in the RVS group. LV dyssynchrony parameters were not significantly different between the groups at the 1-week follow-up, but they were significantly smaller in the RVS group than in the RVA group at the 6-month follow-up. LV dyssynchrony parameters significantly decreased in the RVS group from the 1-week follow-up to the 6-month follow-up, but were unchanged in the RVA group. No differences in LV function parameters were observed between the groups at the 1-week and 6-month follow-ups. CONCLUSIONS: RVS pacing produces better electrical and mechanical synchrony than RVA pacing for patients with complete AV block.

Rat induced pluripotent stem cells protect H9C2 cells from cellular senescence via a paracrine mechanism.

OBJECTIVES: Cellular senescence may play an important role in the pathology of heart aging. We aimed to explore whether induced pluripotent stem cells (iPSCs) could inhibit cardiac cellular senescence via a paracrine mechanism. METHODS: We collected iPSC culture supernatant, with or without oxidative stress, as conditioned medium (CM) for the rat cardiomyocyte-derived cell line H9C2. Then we treated H9C2 cells, cultured with or without CM, with hypoxia/reoxygenation to induce cellular senescence and measured senescence-associated ß-galactosidase (SA-ß-gal) activity, G1 cell proportion and expression of the cell cycle regulators p16(INK4a), p21(Waf1/Cip1) and p53 at mRNA and protein levels in H9C2 cells. In addition, we used Luminex-based analysis to measure concentrations of trophic factors in iPSC-derived CM. RESULTS: We found that iPSC-derived CM reduced SA-ß-gal activity, attenuated G1 cell cycle arrest and reduced the expression of p16(INK4a), p21(Waf1/Cip1) and p53 in H9C2 cells. Furthermore, the CM contained more trophic factors, e.g. tissue inhibitor of metalloproteinase-1 and vascular endothelial growth factor, than H9C2-derived CM. CONCLUSIONS: Paracrine factors released from iPSCs prevent stress-induced senescence of H9C2 cells by inhibiting p53-p21 and p16-pRb pathways. This is the first report demonstrating that antisenescence effects of stem cell therapy may be a novel therapeutic strategy for age-related cardiovascular disease.

Coexpression of VEGF and angiopoietin-1 promotes angiogenesis and cardiomyocyte proliferation reduces apoptosis in porcine myocardial infarction (MI) heart.

VEGF and angiopoietin-1 (Ang1) are two major angiogenic factors being investigated for the treatment of myocardial infarction (MI). Targeting VEGF and Ang1 expression in the ischemic myocardium can increase their local therapeutic effects and reduce possible adverse effects. Adeno-associated viral vectors (AAVs) expressing cardiac-specific and hypoxia-inducible VEGF [AAV-myosin light chain-2v (MLC)VEGF] and Ang1 (AAV-MLCAng1) were coinjected (VEGF/Ang1 group) into six different sites of the porcine myocardium at the peri-infarct zone immediately after ligating the left descending coronary artery. An identical dose of AAV-Cytomegalovirus (CMV)LacZ or saline was injected into control animals. AAV genomes were detected in the liver in addition to the heart. RT-PCR, Western blotting, and ELISA analyses showed that VEGF and Ang1 were predominantly expressed in the myocardium in the infarct core and border of the infarct heart. Gated single-photon emission computed tomography analyses showed that the VEGF/Ang1 group had better cardiac function and myocardial perfusion at 8 wk than at 2 wk after vector injection. Compared with the saline and LacZ controls, the VEGF/Ang1 group expressed higher phosphorylated Akt and Bcl-xL, less Caspase-3 and Bad, and had higher vascular density, more proliferating cardiomyocytes, and less apoptotic cells in the infarct and peri-infarct zones. Thus, cardiac-specific and hypoxia-induced coexpression of VEGF and Ang1 improves the perfusion and function of porcine MI heart through the induction of angiogenesis and cardiomyocyte proliferation, activation of prosurvival pathways, and reduction of cell apoptosis.

Long-term outcome following ablation of atrial tachycardias occurring after mitral valve replacement in patients with rheumatic heart disease.

BACKGROUND: Atrial tachycardia (AT) is a frequent late sequel of surgical valve replacement procedures in patients with rheumatic heart disease (RHD). The aim of this study was to evaluate the acute and long-term outcome of catheter ablation in such patients. METHODS AND RESULTS: A total of 21 consecutive RHD patients with AT after a valve replacement were enrolled in this study. The mean interval between the occurrence of symptomatic AT and the surgical intervention was 38.2 ± 48.7 months. The initial procedure was performed 8.4 ± 8.9 months after first onset of AT. During the first procedure, an electroanatomic mapping was completed for 25 ATs, 18 of which were cavotricuspid isthmus-dependent atrial flutter, five that were right atrial free wall AT, and two that were left AT. Acute success was obtained in 95% (20/21) patients. Nine patients with recurrent AT had repeat radiofrequency catheter ablation, and newly developed left AT was identified in five patients after the first right AT ablation. After a mean follow-up of 42.7 ± 17.3 months, only 33% of the patients remained free of ATs, while 14% and 53% of the patients had AT recurrence and the development of atrial fibrillation (AF), respectively. CONCLUSION: Right but not left macroreentry is the most common AT postmitral valve replacement in patients with RHD. The incidence of AF is very high after AT ablation in such patients during the long-term follow-up.

[Clinical characteristics and genetic analysis of three pediatric patients with idiopathic restrictive cardiomyopathy].

OBJECTIVE: Restrictive cardiomyopathy (RCM) is rare in children, and little is known about the molecular basis of RCM. The aim of this study was to investigate the clinical and myopathological characteristics and to detect mutations on cardiac sarcomere protein genes in three idiopathic pediatric RCMs. METHODS: Detailed clinical characteristics and familiar history were obtained in three idiopathic pediatric RCMs. One hundred healthy pediatric individuals were recruited as controls. Histological evaluation was performed with heart tissue retrieved at catheterization in case-1 and case-2. The entire coding sequences of four cardiac sarcomere protein genes, including cardiac troponin T (TNNT2), cardiac troponin I(TNNI3), ß-myosin heavy chain (MYH7), and α-actin (ACTC)were screened for mutations. Sequence variants were then tested in the family as well as in 100 healthy control DNAs. RESULTS: All three index cases were diagnosed as primary RCMs without family history, and their clinical conditions deteriorated rapidly. Case-1 was in combination with ventricular septal defect. Case-2 was in combination with mid- and inferoseptal hypertrophy. In case-1, myocardial biopsies displayed extensive an isomorphism and disarray of cardiomyocytes; electron microscopy showed large stacks of severely dysmorphic megamitochondria and focal Z-disc streaming. In case-2, endomyocardial biopsy revealed moderate myocyte hypertrophy with mild interstitial fibrosis; transmission electron microscopy showed misalignment of Z-bands and unequal Z-Z band distances. Genetic analysis identified two heterozygous missense mutations in TNNI3, with R204H in case-1 and R192H in case-3 respectively. A de novo heterozygous deletion in TNNT2 (p. Asn100_Glu101del) was identified in case-2. Sequence analysis shows that all three mutations are located in a position highly conserved across many species. The three mutations were negative for their parents and controls. CONCLUSION: The clinical conditions in all three index cases are deteriorated rapidly after diagnosed as primary RCM. Three heterozygous mutations including two in TNNI3 and one in TNNT2 gene are identified in the three RCMs respectively, which are considered as causative mutations. These findings provide new insights into the molecular etiology responsible for pediatric RCM.

[Catheter ablation of epicardial accessory pathway associated with coronary sinus musculature].

OBJECTIVE: To report the single-center clinical experience of catheter ablation of epicardial accessory pathway associated with coronary sinus musculature. METHODS: The data of 721 cases of left sided accessory pathway ablation were retrospectively analyzed. Ablation in the coronary sinus was performed in 17 (2.4 %) cases [11 males, mean age (37 ± 11) years]. RESULTS: Among the 17 cases, the accessory pathway was successfully ablated in middle cardiac vein and posterior lateral coronary sinus in 11 and 6 cases, respectively. Deverticulum of middle cardiac vein was seen in 2 cases. Mean time required to block the accessory pathway was (4.7 ± 2.7) s. An accessory pathway potential could be recorded at the target site in 10 out of 17 patients (59%). During a mean (21 ± 16) months follow up, only one patient experienced recurrence who was successfully cured by a second ablation session. No procedure related complication was reported. CONCLUSION: About 2.4% of left accessory pathway may have epicardial connection locating at middle cardiac vein or lateral part of the coronary sinus and require epicardial ablation. The epicardial ablation is safe and effective, warrants an excellent long-term results.

[Efficacy of catheter radiofrequency ablation for the treatment of ventricular arrhythmia storm post cardioverter-defibrillators implantation].

OBJECTIVE: To evaluate the acute and long-term effects of catheter radiofrequency ablation for the treatment of ventricular arrhythmia storm (VAS) post implantable cardioverter-defibrillators (ICD) implantation. METHODS: Acute and long-term effects of catheter radiofrequency ablation for the treatment of VAS post ICD implantation were retrospectively assessed in 11 patients from September 2008 to August 2011. RESULTS: A total of 15 ablation procedures were performed in 11 patients. Six ablation procedures were performed through epicardial approach. In 9 patients, 20 types of ventricular tachycardia (VT) (including 20% hemodynamically unstable VT) were induced during the procedures [mean cycle length (384 ± 141) ms] and polymorphic ventricular tachycardia were induced in 7 patients. The average X-ray fluoroscopy time and procedural time were (26 ± 17) min and (189 ± 60) min, respectively. Complete success, partial success, and failure rates immediately post catheter radiofrequency ablation were 46.7% (7/15), 26.7% (4/15) and 26.7% (4/15), respectively. All patients are alive at follow-up[(2.45 ± 9.6) months after the last catheter ablation] and the complete success, partial success, and failure rates during follow-up were 72.7% (8/11), 9.1% (1/11) and 18.2% (2/11), respectively. CONCLUSION: VAS can be effectively treated by catheter radiofrequency ablation in patients post ICD implantation.