室性心动过速患者QT离散度变化的临床意义

目的　探讨室性心动过速 (VT)患者 QT离散度 (QTd)变化的意义。方法　对正常对照组 (35例 )和 VT组 (31例 )记录 12导联同步心电图 ,人工测量 QT间期 ,计算 QTd。结果　与对照组相比 ,VT组 12导联QTd明显增加 (P<0 .0 1) ,但两组之间存在很大交叉 ,无法建立正常参考值 ;QT间期明显延长 (P<0 .0 1) ,两组QTmax多见于 V2 、V3、V4 和 V5导联 (分别为 75 .0 %、77.8% ) ,两组 QTmax、QTmin导联分布无显著差异 (P>0 .0 5 )。结论　 VT患者的 QTd不能代表心肌复极的区域性差异 ,仅可作为心肌复极异常简单、粗略的指标。     

慢性激活天门冬氨酸受体对心室复极变异性储备和心律失常的影响

目的 研究慢性激活天门冬氨酸（N-methyl-d-aspartate,NMDA）受体对心室复极变异性和储备的影响,探讨其诱发室性心律失常的可能机制.方法 36只成年雄性Wistar大鼠分为：对照组（CTL组）、NMDA受体激动剂组（N组）和NMDA受体激动剂＋抑制剂组（N＋M组）.在Langerdorff灌流下,行不同频率的S1S1和短阵快速（Burst）刺激左心室前壁和后壁;记录单向动作电位复极到90％的时限（MAPD90）的动态变化,计算短时限变异（STV）、电交替阈值和室性心律失常的诱发率.结果 与CTL组相比,以不同周长刺激时,N组MAPD90和STV的动态变化幅度显著增大;诱发电交替的起搏周长显著增高[（111.67±2.97）ms对（88.33±2.41）ms,P＜0.01];刺激完成前的STV明显增大[（12.18±0.81）ms对（3.61±0.29）ms,P＜0.01];N组的室性心律失常诱发率和持续性室性心律失常比例均高于CTL组：S1S1模式：83.33％对25.00％,P=0.02和75.00％对8.33％,P＜0.01;Burst模式：100％对25％P＜0.01和83.33％对25.00％,P=0.02.N＋M组的上述变化与CTL组相近,差异无统计学意义（P＞0.05）.结论 慢性激活NMDA受体明显增加室性心律失常的易感性,可能与心脏复极变异性增大和复极储备降低有关.     

Usefulness of rate regulation through continuous ventricular pacing in patients with drug-controlled slower atrial fibrillation and normal or depressed left ventricular systolic function

We studied 33 clinically stable patients with permanent atrial fibrillation (AF), implanted with a ventricular demand rate-responsive (VVIR) pacemaker or an automatic defibrillator, in order to evaluate whether continuous right ventricular apex pacing (VP) conferring rate regulation may be advantageous when compared with slower drug-controlled AF. Devices were chronically programmed at ventricular backup pacing. Patients were divided in two groups according to their normal (n = 17) or depressed (n = 16) left ventricular systolic function (LVSF). Ventricular function was studied by using tissue Doppler and color M-mode and echocardiography, as well as B-type natriuretic peptide (BNP) measurements. Baseline data during AF were compared to corresponding measurements following a 1-month pacing period after the devices were programmed at a base rate of 70 beats/min. In both groups, VP worsened some indexes of left and right ventricular function (P < 0.05) without significantly affecting cardiac output, left ventricular filling pressures and BNP (P = not significant). We conclude that VP should not be considered advantageous compared to slower AF.     

植入型心律转复除颤器临床应用

目的　观察 5例恶性室性心律失常患者植入型心律转复除颤器 (ICD)植入术及临床随访情况。方法　 5例因反复发作有血流动力学障碍的室性心动过速 /心室颤动 (VT/ VF)均顺利植入 ICD(其中双腔 ICD2例 ) ,随访 6～ 2 4个月 ,观察患者临床疗效及 ICD工作情况。结果　 5例患者无 1例死亡。随访期间共出现 VT/ VF事件 30 4次 ,ICD识别并治疗的 VT/ VF事件 71次 ,VT 6 5次 ,占 91.5 % ,VF 6次 ,占 8.5 % ,抗心动过速起搏 (ATP)终止 5 5次 ,占77.5 % ,心律转复 (CV)终止 16次 ,占 2 2 .5 % ,VF经除颤 (DF)全部一次成功。结论　 ICD的治疗效果肯定 ,需加强随访 ,及时修改参数 ,同时应加强药物的辅助治疗 ,如 β-受体阻断剂 ,胺碘酮等 ,积极改善心功能。     

心肌梗死后室壁瘤形成与室性心动过速的关系探讨

目的 探讨心肌梗死（MI）后室壁瘤形成大小、左室大小、左心功能与室性心动过速的关系.方法 回顾性分析114例心肌梗死后室壁瘤形成患者的临床资料,根据动态心电图、心电监护证实并发室性心动过速21例归为室速组,其余为非室速组,分析比较两组患者的病史特点、左房直径、左室舒张末期直径、左室收缩末期直径、左室舒张期室间隔厚度、左室舒张期后壁厚度、室壁瘤大小及左室射血分数.结果 两组间左房直径[（4.49±0.47）cm比（4.07±0.62）cm,P=0.040]、左室舒张末期直径[（6.34±0.80）cm比（5.77±0.76）cm,P=0.029]和左室收缩末期直径[（5.18±1.01）cm比（4.33±0.94）cm,P=0.008]比较,差异有统计学意义,左房直径、左室舒张期后壁厚度、室壁瘤基底直径、室壁瘤膨出直径、左室射血分数两组间比较差异无统计学意义（P〉0.05）.结论 心肌梗死后室壁瘤形成,其左室大小与室性心动过速有一定关系,而与室壁瘤大小无关.     

Mechanisms of sudden cardiac death

Worldwide, sudden cardiac death (SCD) is a major problem. It is most frequently caused by ventricular tachyarrhythmias: Monomorphic and polymorphic ventricular tachycardia (VT), torsade de pointes (TdP), and ventricular fibrillation (VF). Beta blockade, ACE inhibition, coronary reperfusion and other treatments have reduced the incidence of VT but pulseless electrical activity (PEA) is increasingly seen, particularly in patients with advanced chronic heart disease. From existing data, bradyarrhythmia in the form of asystole (usually complete heart block without escape rhythm) causes only a minor proportion (10–15%) of SCD. In patients aged 50 years and more, coronary artery disease plays a dominant role causing more than 75% of SCD cases, either by acute ischemia and ventricular fibrillation or by chronic scar formation and reentrant VT. In younger patients, SCD may occur in patients with structurally normal hearts. A number of arrhythmogenic disorders with an increased risk of SCD have been detected and better understood recently, such as long and short QT syndrome, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia, and the early repolarization syndrome. Most importantly, ECG signs and clinical features indicating high risk for SCD have been identified. Knowledge of the exact electrophysiologic mechanisms of ventricular tachyarrhythmias at the cellular level has been improved and mechanisms such as phase 2 reentry and reflection proposed to better understand why and how SCD occurs.     

大剂量静脉用胺碘酮治疗顽固性、持续性室性心律失常的临床疗效及安全性

目的：评价静脉用胺碘酮（ａｍｉｏｄａｒｏｎｅ）对顽固性、持续性室性心动过速（ＳＶＴ）、心室颤动（ＶＦ）患者的临床疗效。方法：２４例ＳＶＴ和（或）ＶＦ患者，其中男１９例，女５例，平均年龄４９．２±１２．４岁；冠心病陈旧性心肌梗死１４例，心肌病７例，心肌炎２例，先天性心脏病１例。静脉注射胺碘酮首剂３～５ｍｇ／ｋｇ，１０分钟内注入，继之以１．０～１．５ｍｇ／ｍｉｎ维持静脉滴注，第１个２４小时总量平均２１６５．０±３８５．４ｍｇ（包括口服量），以后依病情渐减，维持静脉滴注平均４．２±２．５天。静脉应用同时加用口服胺碘酮６００～１２００ｍｇ／ｄ。第１次负荷量后，若心律失常控制不理想，可每隔１５～３０分钟再给１．５～３．０ｍｇ／ｋｇ的追加负荷量。疗效判断以ＳＶＴ和（或）ＶＦ消失为有效。结果：总有效率８３．３％。２例静脉用胺碘酮期间出现窦性心动过缓、窦性停搏及一过性Ⅱ度房室传导阻滞。经减量后恢复。结论：静脉应用大剂量胺碘酮治疗快速性室性心律失常安全有效。     

糖耐量异常对心室重塑的影响

目的 探讨糖耐量异常对心室重塑的影响及可能的机制,从而预防心室重塑的发生和发展.方法 入选患者均接受葡萄糖耐量试验(OGTT)和心脏彩色超声检查,测定E波与A波流速比值(E/A)、计算左室心肌重量(LVM)、左室心肌指数(LVMI),行24 h动态血压检测,分析糖耐量异常与心室重塑相关指标的关系.结果 合并糖耐量异常高血压组左室舒张功能减低发生率(74%)高于单纯高血压组(39%)(x2=6.5,P＜0.05),糖耐量异常组左室舒张功能减低(34%)发生率高于对照组(10%)(x2=5.2,P＜0.05).合并糖耐量异常高血压组左室肥厚发生率(24%)明显高于高血压组、糖耐量异常组及正常组(分别为7%、0、0)(x2=4.561,P＜0.05).多因素逐步回归分析显示,年龄和餐后2 h血糖值是E/A比值的独立危险因素.结论 糖耐量异常是导致左室肥厚和舒张功能减低的一个危险因素和病理基础之一,且导致左室舒张功能减低发生率高于左室肥厚.     

室性期前收缩伴原发性ST—T改变的发生机制及临床意义

为研究室性期前收缩伴原发性ＳＴ－Ｔ改变的发生机制及临床意义，分析５７例符合室性期前收缩伴原发性ＳＴ－Ｔ改变诊断标准的患者（Ｉ组）的相关参数，并与５８例无器质性心脏病证据的室性期前收缩患者（Ⅱ组）比较。Ｉ组中２５例视原发性ＳＴ－Ｔ改变持续存在与否作逐日自身前后对照分析。结果发现：室性期前收缩伴原发性ＳＴ－Ｔ改变１００％见于器质性心脏病患者，其持续存在可预示进展到高Ｌｏｗｎ分级室性心律失常；室性期前收     

无器质性心脏病证据的室性心动过速的电生理检查与随访

本文对35例无临床器质性心脏病证据的室性心动过速患者进行了电生理检查及心室晚电位检查,并随访41.2±24个月。结果发现,临床表现为单形持续性室速者电程序刺激阳性率高(6/8),若不积极治疗,少数患者可能有猝死的危险。临床表现为非持续性室速者,电程序刺激及晚电位检查的阳性率均极低(分别为0/27和1/27)。我们认为,对于无临床器质性心脏病的持续性室速者,应进行电生理检查并筛选有效药物,给予抗心律失常治疗;而非持续性室逮不是电生理检查的适应证,对无症状者可不予治疗;对有症状者可对症治疗,其预后良好。     

Evaluation of the effectiveness of a wearable cardioverter defibrillator detection algorithm

Background

Wearable cardioverter defibrillators (WCDs) provide protection from sudden cardiac death. The efficacy of a WCD detection algorithm has not been reported outside of clinical trial.

Methods

The efficacy of the algorithm was reviewed through a retrospective analysis of appropriate shocks, inappropriate shocks, and arrhythmia detections during a 1-year period.

Results

WCD patients had an appropriate shock rate of 1.58 per 100 patient-months and an inappropriate shock rate of 0.99 per 100 patient-months. Most of the arrhythmia detections in a 3-month period were short in length, with only 2.7% of the detections lasting over 25 seconds, the time at which a shock becomes possible.

Conclusions

By incorporating a patient responsiveness test, as well as features that eliminate or reduce signal interference common to external electrocardiogram electrodes, the WCD detection algorithm has a low risk of inappropriate shocks.     

Predictive power of T-wave alternans and of ventricular gradient hysteresis for the occurrence of ventricular arrhythmias in primary prevention cardioverter-defibrillator patients

Background and purpose

Left ventricular ejection fraction lacks specificity to predict sudden cardiac death in heart failure. T-wave alternans (TWA; beat-to-beat T-wave instability, often measured during exercise) is deemed a promising noninvasive predictor of major cardiac arrhythmic event. Recently, it was demonstrated that TWA during recovery from exercise has additional predictive value. Another mechanism that potentially contributes to arrhythmogeneity is exercise-recovery hysteresis in action potential morphology distribution, which becomes apparent in the spatial ventricular gradient (SVG). In the current study, we investigated the performance of TWA amplitude (TWAA) during a complete exercise test and of exercise-recovery SVG hysteresis (SVGH) as predictors for lethal arrhythmias in a population of heart failure patients with cardioverter-defibrillators (ICDs) implanted for primary prevention.

Methods

We performed a case-control study with 34 primary prevention ICD patients, wherein 17 patients (cases) and 17 patients (controls) had no ventricular arrhythmia during follow-up. We computed, in electrocardiograms recorded during exercise tests, TWAA (maximum over the complete test) and the exercise-recovery hysteresis in the SVG. Statistical analyses were done by using the Student t test, Spearman rank correlation analysis, receiver operating characteristics analysis, and Kaplan-Meier analysis. Significant level was set at 5%.

Results

Both SVGH and TWAA differed significantly (P < .05) between cases (mean ± SD, SVGH: −18% ± 26%, TWAA: 80 ± 46 μV) and controls (SVGH: 5% ± 26%, TWAA: 49 ± 20 μV). Values of TWAA and SVGH showed no significant correlation in cases (r = −0.16, P = .56) and in controls (r = −0.28, P = .27). Receiver operating characteristics of SVGH (area under the curve = 0.734, P = .020) revealed that SVGH less than 14.8% discriminated cases and controls with 94.1% sensitivity and 41.2% specificity; hazard ratio was 3.34 (1.17-9.55). Receiver operating characteristics of TWA (area under the curve = 0.699, P = .048) revealed that TWAA greater than 32.5 μV discriminated cases and controls with 93.8% sensitivity and 23.5% specificity; hazard ratio was 2.07 (0.54-7.91).

Discussion and conclusion

Spatial ventricular gradient hysteresis bears predictive potential for arrhythmias in heart failure patients with an ICD for primary prevention, whereas TWA analysis seems to have lesser predictive value in our pilot group. Spatial ventricular gradient hysteresis is relatively robust for noise, and, as it rests on different electrophysiologic properties than TWA, it may convey additional information. Hence, joint analysis of TWA and SVGH may, possibly, improve the noninvasive identification of high-risk patients. Further research, in a large group of patients, is required and currently carried out by our group.     

Endocardial catheter ablation of ventricular tachycardia in patients with ventricular assist devices

BACKGROUND: The outcomes of patients with ventricular assist devices (VADs) who undergo catheter ablation for ventricular tachycardia (VT) have not been reported. OBJECTIVE: The purpose of this study was to assess the feasibility, safety, and efficacy of endocardial VT ablation in patients with VADs. METHODS: We retrospectively reviewed three cases at our institution where endocardial catheter ablation was performed in patients with VADs and incessant VT. RESULTS: Three patients with underlying cardiomyopathies and VADs underwent VT ablation for incessant VT refractory to multiple antiarrhythmic medications. In each case, VT was either eliminated or significantly ameliorated by catheter ablation. No procedure-related complications occurred. The hemodynamic stability afforded by the VAD played an important role in facilitating ablation in two of the cases. CONCLUSION: Catheter ablation for VT in VAD patients appears to be feasible, safe, and effective based on our initial experience. Several technical issues, such as decreases in ventricular volumes that can limit maneuverability of the ablation catheter and potential entrapment of the mapping catheter in the inflow cannula, need to be considered at the time of ablation.     

急性心肌缺血QT离散度变化与室速室颤的关系

目的：探讨冠心病患者急性心肌缺血对 Ｑ Ｔ 离散度（ Ｑ Ｔｄ）、校正后的 Ｑ Ｔ 离散度（ Ｑ Ｔｃｄ）的影响及其与室性心动过速（简称室速）、心室颤动（简称室颤）的关系。方法：选择７１例确诊为冠心病心绞痛的患者，分成室速室颤组（１３例）和非室速室颤组（５８例），测定每例患者心绞痛发作前、发作时及发作后的 Ｑ Ｔｄ、 Ｑ Ｔｃｄ。结果：心绞痛发作时 Ｑ Ｔｄ、 Ｑ Ｔｃｄ 均显著大于心绞痛发作前和发作后（均 Ｐ ＜ ０．０１），后两者比较无显著性差异（ Ｐ ＞ ０．０５）。室速室颤组心绞痛发作时 Ｑ Ｔｄ、 Ｑ Ｔｃｄ均显著大于非室速室颤组（均 Ｐ ＜ ０．０１）。心绞痛发作前以 Ｑ Ｔｄ≥８０ ｍ ｓ 为标准，则预测室速室颤发生的敏感性为５３．８％ ，特异性为８２．８％ ，准确性为７７．５％ ；心绞痛发作时以 Ｑ Ｔｄ≥１００ ｍ ｓ 为标准，则预测室速室颤发生的敏感性为９２．３％ ，特异性为８４．５％ ，准确性为８５．９％ 。结论：冠心病患者急性心肌缺血时 Ｑ Ｔｄ、 Ｑ Ｔｃｄ 显著增大，易发生室速室颤。急性心肌缺血时的 Ｑ Ｔｄ、 Ｑ Ｔｃｄ 变化可能是预测室速室颤发生更为敏感的指标。     

冠心病患者QT及JT间期离度增加与恶性心律失常的关系

目的探讨冠心病患者QT间期离散度（QTd和JT间期离散度（JTd）的增加与室性心动过速、室性颤动（恶性心律失常）的关系。方法测定冠心病（心绞痛型和心力衰竭型）患者中恶性心律失常组（22例）与无恶性心律失常组（30例）之体表12导联心电图的QTd及JTd。结果恶性心律失常组的QTd和JTd分别为72．7±23．1ms和72．8±21．9ms,明显高于无恶性心律失常组（38.2±16．8ms和37．1±16.2ms），差异显著（P＜0．01）。如以QTd值＞40ms或≥80ms分别预测出现恶性心律失常的可能，其敏感性分别为64．5％和100％，特异性分别为90．5％和63．8％，预测值分别为90．9％和100％。结论冠心病病人的QTd或JTd明显增加时，易发生恶性心律失常。提示检测QTd或JTd是预测冠心病病人发生恶性心律失常的一种简单可靠的方法。