Right ventricular electrocardiographic leads for detection of Brugada syndrome in sudden unexplained death syndrome survivors and their relatives

BACKGROUND: Sudden unexplained death syndrome (SUDS) is a sudden death syndrome in previously healthy Southeast Asian young adults without any structural causes of death. Many SUDS survivors show electrocardiographic (ECG) evidence of RSR' and ST elevation in leads V1 to V3, which is similar to the ECG pattern in Brugada syndrome. However, in many cases transient normalization of the ECG does not make diagnosis with standard 12-lead ECG possible. HYPOTHESIS: To overcome this problem, we utilized the new right ventricular ECG leads to detect the Brugada syndrome in SUDS survivors. METHODS: The subject was a Thai male patient who presented with a SUDS-like syncopal attack. He had cardiac arrest due to idiopathic ventricular fibrillation. RESULTS: Post-resuscitation standard 12-lead ECG showed no diagnostic features of Brugada syndrome. However, ECG patterns of RSR' and ST elevations typical for Brugada syndrome could be detected at the higher intercostal space leads V1 to V3. We observed similar findings in 2 of the other 10 SUDS survivors and 4 of 23 healthy family members. CONCLUSIONS: Our data suggest that these new right ventricular leads ECG may be helpful in detecting Brugada syndrome in SUDS survivors and their relatives.     

Prolonged qt interval: A marker of sudden infant death syndrome?

A prospective electrocardiographic study was performed in 1830 newborns to evaluate the predictive value of QT interval for sudden infant death syndrome (SIDS). Standard ECG, with babies asleep, was recorded at the ages of 4 days, 2, 4, 6 months, and 1 year. The QTc (+/- SD) was 392 +/- 22 at 4 days, 410 +/- 16 (p less than 0.0001) at 2 months (n = 1256), 404 +/- 16 at 4 months (n = 1015), 400 +/- 16 at 6 months (n = 895), and 398 +/- 15 at 1 year (n = 890). QTc values longer than the mean plus 3 standard deviations were considered prolonged. Heart rate values (beats/min) were 138 +/- 19 at 4 days, 141 +/- 13 at 2 months, 134 +/- 13 at 4 months, 133 +/- 13 at 6 months, and 128 +/- 14 at 1 year. In 34 babies the QT interval was prolonged (mean + 3SD) and 3 of these died suddenly: the first, at 3 months (QTc = 470 and HR = 147 at 4 days); the second after 7 weeks (QTc = 514, HR = 115); the third at 3 months (QTc = 464 and HR = 140 at 4 days).     

Benefit of Pacing and Beta-Blockers in Idiopathic Repetitive Polymorphic Ventricular Tachycardia

An 18-year-old woman presented with recurrent exercise-induced syncopal episodes and severe systolic dysfunction. ECG monitoring disclosed repetitive polymorphic ventricular complexes, paroxysms of bidirectional ventricular tachycardia, and nonsustained bursts of slow polymorphic ventricular tachycardia that increased in length and rate during exercise. Ventricular arrhythmias were refractory to medical treatment, which included verapamil and beta-blockers. Addition of permanent atrial pacing to beta-blocker therapy suppressed the arrhythmias and reversed systolic impairment in the following months.     

云南不明原因猝死高危人群心电图分析

目的 通过总结云南不明原因猝死高发地区人群的心电图特征,发现其规律并为进一步的病因学研究提供线索.方法 自2005年9月至2006年7月间,对云南的不明原因猝死高发区(宁蒗、鹤庆、大姚)的三个自然村年龄为15～45岁的居民进行12导联静息心电图普查,以云南大理地区人群作为对照人群.共普查人群338例,男性175例,女性163例,平均年龄(33.4±11.7)岁.记录所有普查者的一般状况及疾病家族史.单盲法测量心电图各指标.结果 猝死高发区与对照地区人群一样,常见心律失常发生率均低,仅见于个别居民.大姚地区左室高电压发生率(34.6%)显著高于其他地区(P均＜0.01).上述三个猝死高发区人群的QTc较对照地区显著延长[分别为(428.92±25.71)ms、(440.67±28.03)ms、(417.70±24.00)ms与(386.80±27.22)ms,P均＜0.05];U波出现率仅鹤庆地区显著高于对照地区(P＜0.05);QUc上述各地区均显著高于对照地区[分别为(613.67±37.34)ms、(597.19±46.47)ms、(608.59±39.59)ms与(589.33±41.27)ms,P均＜0.01];U波呈宽大、高电压并与T波融合特征性表现;在7例有猝死家族史者中,6例有U波,4例呈猝死高发区特征性改变.结论 云南省不明原因猝死高危人群心电图呈QT间期延长和U波特征性改变,提示可能存在潜在的心肌复极异常内因.     

Implantable Cardioverter Defibrillator Therapy in Patients with Ischemic or Non-Ischemic Cardiomyopathy and Nonsustained Ventricular Tachycardia

BACKGROUND: Mortality benefit from implantable cardioverter defibrillator (ICD) therapy in ischemic cardiomyopathy (ICM) with non-sustained ventricular tachycardia (NS-VT) and inducible VT is well defined. Although NS-VT may suggest an increased risk of sudden cardiac death (SCD) in non-ischemic cardiomyopathy (NICM), the role of ICD therapy is unclear. This retrospective study compares follow-up data in these two groups after ICD implantation. METHODS: 153 consecutive patients with ICD implantation for NS-VT were analyzed. ICM patients received an ICD if they had inducible VT at electrophysiology study (EPS). NICM patients did not routinely undergo EPS before ICD implantation. RESULTS: There were 48 patients (33 males) in NICM group and 105 patients (89 males) in the ICM group. Baseline characteristics including mean ejection fraction (EF), distribution in various New York Heart Association (NYHA) classes, and the mean duration of follow up in the two groups were similar. 50% of the patients in the NICM group and 36% in the ICM group received appropriate therapies (p = 0.106). The mean number of appropriate therapies in the two groups were similar (23.3 +/- 56.7 and 22.5 +/- 59.5 respectively, p = NS). The percentage of patients with inappropriate therapies in the two groups were 27% and 23% respectively (p = NS). Patients in the NICM group received appropriate ICD discharges at a greater rate (p = 0.02). CONCLUSION: Patients undergoing ICD implantation for NICM and NS-VT receive appropriate ICD therapy at a greater rate than those implanted for ICM, NS-VT, and a positive EPS. Although these data do not prove survival benefit in NICM, they suggest a beneficial effect.     

Sudden cardiac death: an update

Sudden cardiac death (SCD) is a devastating and all too common result of both acquired and genetic heart diseases. The profound sadness endured by families is compounded by the risk many of these deaths confer upon surviving relatives. For those with known cardiac disease, disease‐specific therapy and risk stratification are key to reducing sudden death. For families of a SCD victim, uncovering a definitive cause of death can help relieve the agonising uncertainty and is a vital first step in screening surviving relatives and instituting therapy to reduce SCD risk. Increasing knowledge about the molecular mechanisms and genetic drivers of malignant arrhythmias in the diverse clinical entities that can cause SCD is vital if we are to optimise risk stratification and personalise patient care. Advances in diagnostic tools, disease‐specific therapy and defibrillator technology are improving outcomes for patients and their families but there is still much progress to be made.     

Ventricular Fibrillation in a Patient with Prominent J (Osborn) Waves and ST Segment Elevation in the Inferior Electrocardiographic Leads:

Recurrent ventricular fibrillation was observed in a 29-year-old Vietnamese man who did not exhibit structural heart disease. The patient's ECG showed prominent J (Osborn) waves and ST segment elevation in the inferior leads that were not associated with hypothermia, serum electrolyte disturbance, or myocardial ischemia. Rate-dependent change in the amplitude of J waves and ST segment elevation also were observed. An implantable cardioverter defibrillator (ICD) was implanted. Adjunctive treatment with amiodarone reduced J wave amplitude, preventing ventricular fibrillation and ICD shocks. Prominent J waves and ST segment elevation in the inferior leads may serve as an important diagnostic sign to detect high-risk individuals with a history of unexplained syncope. ICD implantation plus amiodarone is the treatment of choice.     

Further Characterization of the Syndrome of Right Bundle Branch Block, ST Segment Elevation, and Sudden Cardiac Death

RBBB, ST Elevation, and SCD. We recently described a syndrome characterized by an ECG pattern of right bundle branch block and persistent ST segment elevation in leads V₁ to V₃ in patients suffering from aborted sudden cardiac death and not having demonstrable structural heart disease. We present new observations on this syndrome, especially those related to asymptomatic and intermittent forms. Forty-seven patients with the described ECG pattern were identified; 32 were symptomatic with syncope and sudden death aborted by cardiopulmonary resuscitation. Eleven patients received pharmacologic therapy, mainly amiodarone and/or beta-blocking agents, and 21 patients received an implantable defibrillator with or without pharmacologic therapy. Three of the 11 patients on pharmacologic therapy died suddenly during follow-up, while 9 of 21 patients with an implantable defibrillator used the device during follow-up. The remaining 15 patients were asymptomatic when first seen. Three patients died suddenly after 6 years, 3 months, and 2 months of follow-up without treatment. Another patient received an implantable defibrillator after syncope and had subsequent episodes of ventricular fibrillation terminated by the defibrillator. The other 11 patients remain asymptomatic without (6) or with (5) treatment with beta blockers. In 14 of the 47 patients, the ECG normalized momentarily during follow-up but later became abnormal again. During transient normalization of the ECG, administration of ajmaline or procainamide unmasked the described ECG pattern in six patients who received the drug. Long-term follow-up of survivors failed to show progression to any form of right or left ventricular cardiomyopatby.     

Further insights into the effect of quinidine in short QT syndrome caused by a mutation in HERG

INTRODUCTION: The principal aim of this study was to assess the efficacy of quinidine in suppressing IKr in vitro and in modulating the rate dependence of the QT interval in the "SQT1" form of the short QT syndrome. METHODS AND RESULTS: Graded-intensity bicycle exercise testing was performed off drug in three patients and during oral quinidine in two patients with short QT syndrome and compared to a control group of healthy normal subjects. The in vitro effects of quinidine on currents in patch clamp technique were investigated. Off drugs QTpV3/heart rate correlation is much weaker in patients with short QT syndrome, and QTpV3 shortens less with heart rate increase compared to normal subjects. In addition to prolonging the QT interval into the normal range, quinidine restored the heart rate dependence of the QT interval toward a range of adaptation reported for normal subjects. Data from heterologous expression of wild-type and mutant HERG genes indicate the mutation causes a 20-fold increase in IC50 of d-sotalol but only a 5.8-fold increase in IC50 of quinidine. CONCLUSION: Oral quinidine is effective in suppressing the gain of function in IKr responsible for some cases of short QT syndrome with a mutation in HERG and thus restoring normal rate dependence of the QT interval and rendering ventricular tachycardia/ventricular fibrillation noninducible.     

Brugada and Long QT‐3 Syndromes: Two Phenotypes of the Sodium Channel Disease

Brugada and long QT‐3 syndromes are two allelic diseases caused by different mutations in SCN5A gene inherited by an autosomal dominant pattern with variable penetrance. Both of these syndromes are ion channel diseases of the heart manifest on surface electrocardiogram by ST‐segment elevation in the right precordial leads and prolonged QT_c interval, respectively, with predilection for polymorphic ventricular tachycardia and sudden death, which may be the first manifestation of the disease. Brugada syndrome usually manifests during adulthood with male preponderance, whereas long QT3 syndrome usually manifests in teenage years, although it can also manifest in adulthood. Class IA and IC antiarrhythmic drugs increase ST‐segment elevation and predilection for polymorphic ventricular tachycardia and ventricular fibrillation in Brugada syndrome, whereas these agents shorten the repolarization and QT_c interval, and thus may be beneficial in long QT‐3 syndrome. Beta‐blockade also increases the ST‐segment elevation in Brugada syndrome but decreases the dispersion of repolarization in long QT‐3 syndrome. Mexiletine, a class IB sodium channel blocker decreases QT_c interval as well as dispersion of repolarization in long QT‐3 syndrome but has no effect on Brugada syndrome. The only effective treatment available at this time for Brugada syndrome is implantable cardioverter defibrillator, although repeated episodes of polymorphic ventricular tachycardia can be treated with isoproterenol. In symptomatic patients of long QT‐3 syndrome in whom the torsade de pointes is bradycardia‐dependent or pause‐dependent, a pacemaker could be used to avoid bradycardia and pauses and an implantable cardioverter defibrillator is indicated where arrhythmia is not controlled with pacemaker and beta‐blockade. However, the combination of new devices with pacemaker and cardioverter‐defibrillator capabilities appear promising in these patients warranting further study.     

Is QT Dispersion Associated with Sudden Cardiac Death in Patients with Hypertrophic Cardiomyopathy?

QT dispersion is significantly greater in patients with hypertrophic cardiomyopathy (HCM) than that in healthy subjects. Few data exist regarding the prognostic value of QT dispersion in HCM. In this study, we retrospectively investigated the association between QT dispersion and sudden cardiac death in 46 patients with HCM (mean 33.1 ±; 15.5 years, 32 men). The case group consisted of 23 HCM patients who died suddenly, and the control group consisted of 23 HCM patients who survived uneventfully during follow‐up. Study patients were pair‐matched for age, gender, and maximum left ventricular wall thickness. QT dispersion (maximum minus minimum QT interval) was manually measured on early 12‐lead ECGs using a digitizing; board. An in‐house program was used for calculating QT interval, QT dispersion, JT interval, and JT dispersion (maximum minus minimum J point to T end interval). Patients in the case group tended to have shorter RR intervals than those in the control group (777 ±; 171 vs 856 ±; 192 ms, P = 0.08). Maximum corrected QT and JT intervals did not discriminate the case group from controls (489 ±; 29 vs 479 ±; 27 ms, P = NS; 375 ±; 36 vs 366 ±; 22 ms, P = NS, respectively). Greater QT dispersion and JT dispersion were found in the case group compared with controls (74 ±; 28 vs 59 ±; 21 ms, P = 0.02 and 76 ±; 32 vs 59 ±; 26 ms, P = 0.03, respectively). The measurements of maximum QT, JT, and T peak to T end intervals, precordial QT and JT dispersion, and T peak and T end dispersion were all comparable between the two groups (P = NS for all). No systematic changes in ECG measurements were found from late ECGs of the case group compared to those from early ECGs (P = NS). No correlation between maximum left ventricular wall thickness and QT dispersion, JT dispersion, maximum QTc or JTc intervals was observed (r < 0.29, P > 0.05 for all). Our results; show that increased QT dispersion and JT dispersion is weakly associated with sudden cardiac death in the selected patients with HCM. A.N.E. 2001; 6(3):209–215     

中国人群青壮年猝死综合征的流行现状——广东省东莞市、深圳龙岗区及宝安区青壮年猝死综合征的流行病学调查

目的了解中国人群不明原因夜间睡眠猝死综合征(SUNDS)的流行现状。方法采用描述性研究方法,对广东省东莞市、深圳市宝安区及龙岗区975例SUNDS案件资料进行回顾性分析。结果中国人SUNDS主要发生于劳动强度较高、文化素质较低的生产作业工人,年发病率约为1.0人/10万;男性病例占93.23%,80.56%的病例集中在21~40岁;4、5月份异常高发,SUNDS病例与急诊发热病例的月份分布呈正相关(r=0.785,P<0.05);64.96%的病例籍贯属于北纬30度以南地区;目击病例的临床症状集中表现为睡眠中突发呼吸障碍。结论本研究首次勾勒了中国人群SUNDS的流行现状并初步提出与其发生可能相关的危险因素,为后继的病因探索奠定了基础。