[Clinical polymorphisms and approaches of arrhythmias treatment in a family with δKPQ1505-1507 deletion in SCN5A gene]

BACKGROUND

The aim of the study was to analyze spectrum of manifestation and treatment response in large family with rhythm disturbances caused by p.delKPQ1505-1507 mutation in SCN5A gene.

PATIENTS AND METHODS

We had under our observation 18 members of large Iranian family with various combination of inherited arrhythmic syndromes. Careful cardiological examination, genetic councelling and venous blood sampling for molecular genetic study were performed for family members. Mutation screening in SCN5A gene was performed using bidirectional Sanger sequencing.

RESULTS

Here by we show the observation of Iranian family with known mutation p.delKPQ 1505-1507 in SCN5A gene, who display not only LQ-TS phenotype but also some of the carriers of this mutation have had LQ-TS and Brugada syndrome (combine phenotype), interestingly.

CONCLUSION

The overlapping phenotype associated with high risk of sudden cardiac death may require complex approaches to antiarrhythmic therapy, surgical treatment and prevention of sudden cardiac death in the family.

[Brugada syndrome]

Brugada syndrome is an ion channel disease which is associated with an increased risk of sudden cardiac death. Most probably the pathogenesis of ventricular fibrillation in these patients is a combination of both genetically determined repolarisation abnormalities and conduction delay in the right ventricular epicardium. The highest risk of sudden cardiac death is present in patients who have experienced syncope before, who reveal the pathognomic electrocardiographic changes already at rest and who have inducible ventricular fibrillation. Asymptomatic patients who have the J point elevations only after administration of a sodium channel blocker seem to be at lower risk. Most recently the latest joint consensus recommendations of the largest societies for diagnostic criteria, indications for genetic testing and therapy have been published.

[Electrocardiogram in the cardiovascular rare diseases]

Electrocardiography is a method which can not be replaced by any other examination in arrhythmias. It also plays a crucial role in the diagnosis of arrhythmic rare diseases by providing not only diagnostic data, but also paving the way for treatment. This article presents some characteristic examples of ECG in arrhythmic rare diseases (i.e., polimorphic ventricular tachycardia, Brugada syndrome, Coumela syndrome, nonreentrant supraventricular tachycardia with double ventricular response).

Remote monitoring of a high-risk patient with Brugada syndrome: association of different arrhythmic manifestations

We report on the remote arrhythmia monitoring of a 34-year-old man with highly symptomatic Brugada syndrome, who initially presented with syncope, paroxysmal atrial fibrillation, and spontaneous coved-type electrocardiogram. The patient received a dual-chamber implantable cardioverter-defibrillator (ICD) with Home Monitoring™ facilities and experienced recurrent ICD shocks for spontaneous ventricular fibrillation (VF) episodes during the first year after ICD implantation. Remote monitoring revealed an increased burden of premature ventricular complexes and atrial arrhythmias each time VF spontaneously occurred. Atrial and ventricular arrhythmias were effectively suppressed by low-dose quinidine without severe side effects.

The Brugada syndrome revisited

The Brugada syndrome is a rare but well-defined cause of sudden cardiac death. The key underlying abnormality is a decrease in net depolarising current due to a genetic defect, though recent evidence also implicates structural abnormalities in some patients. Diagnosis requires a Brugada-type ECG as well as typical clinical features: such clinical considerations are currently key in guiding risk stratification and hence management. Whilst pharmacological therapies are under investigation, the only intervention with a robust evidence base remains insertion of an implantable cardioverter defibrillator. Further research will be required to allow more effective risk stratification and hence more rational therapy.

Cardiac autonomic control in Brugada syndrome patients during sleep: the effects of sleep disordered breathing

AIMS

Brugada syndrome is characterized by typical ECG features, ventricular arrhythmias and sudden cardiac death (SCD), more frequent during nighttime. Autonomic cardiovascular control has been implicated in triggering the ventricular arrhythmias. Sleep-disordered breathing (SDB) elicits marked autonomic changes during sleep and is also associated with an increased risk of nighttime SCD. Brugada patients may have a higher likelihood of SDB compared to controls. However, no data are available on cardiac autonomic control in Brugada patients, particularly with regard to the comorbidity of SDB.

METHODS

We evaluated autonomic cardiovascular control in Brugada patients with SDB (BRU-SDB, n=9), without SDB (BRU, n=9), in controls (CON, n=8) and in non-Brugada patients with SDB (n=6), during wakefulness and sleep (N2, N3 and REM). Linear spectral and entropy-derived measures of heart rate variability (HRV) were performed during apnea-free stable breathing epochs.

RESULTS

Total HRV was attenuated in BRU-SDB compared to CON and BRU. During N2 and REM, in BRU-SDB patients sympathetic modulation decreased compared to BRU and CON, while during REM, they showed an increased parasympathetic modulation, compared to the other two groups. BRU-SDB and SDB were similar in terms of spectral components. Entropy-derived indices showed preserved dynamic changes in Brugada patients compared to controls through the different sleep stages.

CONCLUSION

Brugada syndrome per se does not appear associated with an altered autonomic cardiovascular control during wakefulness and sleep. The comorbidity with SDB may contribute to disrupted autonomic cardiovascular regulation during sleep, possibly predisposing to the increased likelihood of sleep-related ventricular tachyarrhythmias and SCD.

Electrical storm in the brain and in the heart: epilepsy and Brugada syndrome

We describe a patient with the coincidence of 2 ion channel disorders with autosomal dominant inheritance: Brugada syndrome, a potentially fatal cardiac condition, and cryptogenic focal epilepsy, likely due to a neurologic channelopathy. Although Brugada syndrome was discovered incidentally, most of the clinical features of epilepsy in this patient shared the risk factor characteristics of sudden unexplained death in epilepsy syndrome. This case provides additional information on the potential interaction between ion channel abnormalities in the heart and in the brain. Furthermore, it may suggest that patients with epilepsy at increased risk for sudden unexplained death in epilepsy syndrome should undergo a careful cardiac evaluation.

Brugada phenocopy in a patient with pectus excavatum: systematic review of the ECG manifestations associated with pectus excavatum

Brugada phenocopies (BrP) have emerged as new clinical entities that are etiologically distinct from true Brugada syndrome (BrS). BrP are characterized by an ECG pattern that is phenotypically identical to true BrS (type 1 or type 2); however, BrP are caused by various other factors such as mechanical mediastinal compression, myocardial ischemia, pericarditis, myocarditis, pulmonary embolism, and metabolic disturbances. We report a case of an electrocardiographic BrP in a patient with pectus excavatum deformity in the absence of true BrS using currently defined BrP diagnostic criteria. A systematic review of ECG manifestations associated with pectus excavatum is also discussed.

Outcome after implantation of a cardioverter-defibrillator in patients with Brugada syndrome: a multicenter study-part 2

BACKGROUND

Implantable cardioverter-defibrillator indications in Brugada syndrome remain controversial, especially in asymptomatic patients. Previous outcome data are limited by relatively small numbers of patients or short follow-up durations. We report the outcome of patients with Brugada syndrome implanted with an implantable cardioverter-defibrillator in a large multicenter registry.

METHODS AND RESULTS

A total of 378 patients (310 male; age, 46±13 years) with a type 1 Brugada ECG pattern implanted with an implantable cardioverter-defibrillator (31 for aborted sudden cardiac arrest, 181 for syncope, and 166 asymptomatic) were included. Fifteen patients (4%) were lost to follow-up. During a mean follow-up of 77±42 months, 7 patients (2%) died (1 as a result of an inappropriate shock), and 46 patients (12%) had appropriate device therapy (5±5 shocks per patient). Appropriate device therapy rates at 10 years were 48% for patients whose implantable cardioverter-defibrillator indication was aborted sudden cardiac arrest, 19% for those whose indication was syncope, and 12% for the patients who were asymptomatic at implantation. At 10 years, rates of inappropriate shock and lead failure were 37% and 29%, respectively. Inappropriate shock occurred in 91 patients (24%; 4±4 shocks per patient) because of lead failure (n=38), supraventricular tachycardia (n=20), T-wave oversensing (n=14), or sinus tachycardia (n=12). Importantly, introduction of remote monitoring, programming a high single ventricular fibrillation zone (>210-220 bpm), and a long detection time were associated with a reduced risk of inappropriate shock.

CONCLUSIONS

Appropriate therapies are more prevalent in symptomatic Brugada syndrome patients but are not insignificant in asymptomatic patients (1%/y). Optimal implantable cardioverter-defibrillator programming and follow-up dramatically reduce inappropriate shock. However, lead failure remains a major problem in this population.

Brugada syndrome

As a clinical entity the Brugada syndrome has existed since 1992 and has been associated with a high risk of sudden cardiac death predominately in younger males. Patients can present with symptoms (ie syncope, palpitations, aborted sudden cardiac death) and asymptomatically. Its three characteristic electrocardiographic patterns can occur both spontaneously or after provocation with sodium channel-blocking agents. Risk stratification and the need for treatment depend on the patient's symptoms, electrocardiography, family history, and electrophysiological inducibility to discern if treatment by implantable cardioverter defibrillator, the only effective treatment to date, is appropriate. This review focuses on Brugada syndrome and various aspects of the disease including proposed mechanisms, epidemiology, clinical presentations, genetics, diagnosis, risk stratification, and treatment options.

Clinical characteristic and clinical course of aborted sudden cardiac death patients with structurally normal heart in King Chulalongkorn Memorial Hospital

BACKGROUND

PED (Primary electrical disease) is an arrhythmogenic disease group that causes serious ventricular tachyarrhythmia in the absence of recognized structural heart disease. Although Thailand, which is a part of Southeast Asia, is an endemic area of PED, especially Brugada syndrome, there is little known about demographic data and clinical outcome of PED among survivors of sudden cardiac death (SCD).

OBJECTIVE

To study demographic data and clinical outcome of PED among survivors of SCD in Thailand.

MATERIAL AND METHOD

The present study was approved by the ethics committee of the Faculty of Medicine, Chulalongkorn University, Bangkok. The authors reviewed patient medical records for clinical characteristics, etiology, and clinical outcome of survivors of SCD between January 2002 and December 2008. The patients with PED who had normal structural heart and no obvious non-cardiac causes of sudden death were enrolled.

RESULTS

Fifty-two survivors of SCD with PED (mean age 39 +/- 12, 49 males), mainly from the northeast and middle regions of Thailand, were recruited for this study. SCD mainly occurred during times when patients were asleep or resting (50% and 15.4%) respectively. Of the 52 survivors, 21 patients (40%) had a documented family history of SCD. The etiology of survivors of SCD is composed of Brugada syndrome (63.5%), Early repolarization syndrome (ERS) (9.6%). Congenital long QT syndrome (LQTS) (7.7%), and idiopathic VF (3.8%). Remaining 15.4% had abnormal ECG but not compatible with any etiology. A large number of patients (78.8%) completely recovered without neurological sequelae. The recurrence of severe ventricular arrhythmia occurred in 27 patients (51.9%) during mean follow-up period 56.5 +/- 35.4 months (4 to 137 months). The recurrence was highest during the first year (32%) of follow-up.

CONCLUSION

The Brugada syndrome is the most common etiology of survivors of SCD with normal structural heart in Thailand Although the prognosis after resuscitation was good, recurrence was especially high during the first year and as a result, an ICD implantation is needed for prevented recurrence of SCD.

Current electrocardiographic criteria for diagnosis of Brugada pattern: a consensus report

Brugada syndrome is an inherited heart disease without structural abnormalities that is thought to arise as a result of accelerated inactivation of Na channels and predominance of transient outward K current (I(to)) to generate a voltage gradient in the right ventricular layers. This gradient triggers ventricular tachycardia/ventricular fibrillation possibly through a phase 2 reentrant mechanism. The Brugada electrocardiographic (ECG) pattern, which can be dynamic and is sometimes concealed, being only recorded in upper precordial leads, is the hallmark of Brugada syndrome. Because of limitations of previous consensus documents describing the Brugada ECG pattern, especially in relation to the differences between types 2 and 3, a new consensus report to establish a set of new ECG criteria with higher accuracy has been considered necessary. In the new ECG criteria, only 2 ECG patterns are considered: pattern 1 identical to classic type 1 of other consensus (coved pattern) and pattern 2 that joins patterns 2 and 3 of previous consensus (saddle-back pattern). This consensus document describes the most important characteristics of 2 patterns and also the key points of differential diagnosis with different conditions that lead to Brugada-like pattern in the right precordial leads, especially right bundle-branch block, athletes, pectus excavatum, and arrhythmogenic right ventricular dysplasia/cardiomyopathy. Also discussed is the concept of Brugada phenocopies that are ECG patterns characteristic of Brugada pattern that may appear and disappear in relation with multiple causes but are not related with Brugada syndrome.

[Arrhythmia and genetic background]

Recent studies have demonstrated that genetic abnormalities associated with the regulation of myocardial ionic channels, receptors, transporters, cell membranous proteins etc, can create an arrhythmogenic substrate in some patients with structurally normal hearts, and these are called hereditary arrhythmic diseases. Various arrhythmic diseases (such as congenital long or short QT syndrome, Brugada syndrome, catecholamine-sensitive polymorphic ventricular tachycardia, arrhythmogenic right ventricular cardiomyopathy, early repolarization syndrome etc.) are categorized as hereditary arrhythmic diseases. Among them, we focused on long QT syndrome and Brugada syndrome in this review. In congenital long QT syndrome, either attenuation of the net outward current or augmentation of the net inward current is responsible for prolonging the myocardial action potential duration and QT interval on ECG. Premature ventricular beats triggered due to early after-depolarization infringe on the large spatial dispersion of ventricular repolarization and initiate polymorphic ventricular tachycardia with a specific form (torsade de pointes). Currently, thirteen genotypes in Romano-Ward syndrome and two genotypes in Jervell-Lange Nielsen syndrome have been reported. In Brugada syndrome, large transient outward current (Ito) creates a deep phase 1 notch in the action potential, especially at the epicardial myocardium of the right ventricular outflow tract. In combination with the delayed completion of repolarization and loss of the phase 2 dome in some epicardial myocardium in this area, coved-type ECG abnormality and ventricular fibrillation due to phase 2 reentry are believed to be induced in Brugada syndrome. Eleven genetic abnormalities are presently listed as a possible cause of Brugada syndrome.

A drop dead healthy ECG

The diagnostic and risk stratification implications of a borderline electrocardiogram, which could be a normal variant or a marker for sudden cardiac death, are explored.