Update on the Diagnosis and Management of Brugada Syndrome

Brugada Syndrome (BrS) is an autosomal dominant channelopathy with variable penetrance affecting the sodium channel. It reduces the transport of sodium ions essential for proper generation of the cardiac action potential. The resulting inhomogeneous repolarisation in areas of the RV epicardium causes malignant ventricular arrhythmias.BrS is diagnosed by typical cove shaped ST elevation of > 2mm in ≥1 RV precordial lead V1, V2 occurring spontaneously or after provocative drug test with IV administration of Class 1 antiarrhythmic drug such as flecainide or ajmaline.The incidence of BrS is variable being higher in South East Asians and is generally quoted as 1:2000. It is responsible for up to 20% of sudden arrhythmic deaths in those without structural heart disease. Typical presentation is syncope or resuscitated sudden death and symptoms usually occur at night or at rest especially after a large meal. Fever is a common trigger, particularly in children.Genetic testing for BrS is a Class 2A indication and the yield has increased recently to nearly 40%. Genetic testing assists with family screening

Channelopathies That Lead to Sudden Cardiac Death: Clinical and Genetic Aspects

Forty per cent (40%) of sudden unexpected natural deaths in people under 35 years of age are associated with a negative autopsy, and the cardiac ion channelopathies are the prime suspects in such cases. Long QT syndrome (LQTS), Brugada syndrome (BrS) and catecholaminergic polymorphic ventricular tachycardia (CPVT) are the most commonly identified with genetic testing. The cellular action potential driving the heart cycle is shaped by a specific series of depolarising and repolarising ion currents mediated by ion channels. Alterations in any of these currents, and in the availability of intracellular free calcium, leaves the myocardium vulnerable to polymorphic ventricular tachycardia or ventricular fibrillation. Each channelopathy has its own electrocardiogram (ECG) signature, typical mode of presentation, and most commonly related gene. Long QT type 1 (gene, KCNQ1) and CPVT (gene, RyR2) typically present with cardiac events (ie syncope or cardiac arrest) during or immediately after exercise in young males; long QT type 2 (gene, KCNH2) after startle or during the night in adult females-particularly early post-partum, and long QT type 3 and Brugada syndrome (gene, SCN5A) during the night in young adult males. They are commonly misdiagnosed as seizure disorders. Fever-triggered cardiac events should also raise the suspicion of BrS. This review summarises genetics, cellular mechanisms, risk stratification and treatments. Beta blockers are the mainstay of treatment for long QT syndrome and CPVT, and flecainide is remarkably effective in CPVT. Brugada syndrome is genetically a more complex disease than the others, and risk stratification and management is more difficult

Establishment of an Australian National Genetic Heart Disease Registry

A National Genetic Heart Disease Registry has recently been established, with the aim to enrol every family in Australia with a genetically determined cardiomyopathy or primary arrhythmic disorder. The Registry seeks to further our understanding of the impact and burden of disease in this population; increase awareness and provide education to health professionals and families; and establish a large cardiac genetic cohort as a resource for approved research studies. The Registry is currently recruiting families with inherited cardiomyopathies (e.g. hypertrophic cardiomyopathy) and primary arrhythmogenic disorders (e.g. long QT syndrome), with scope to expand this in the future. Affected individuals, as well as their first-degree (at-risk) family members are eligible to enrol. Participants are currently being recruited from cardiac genetics clinics in approved recruitment sites and hope to expand to other Australian centres including general cardiology practice in the future. A significant focus of the Registry is to improve understanding and create awareness of inherited heart diseases, which includes ensuring families are aware of genetic testing options and current clinical screening recommendations for at-risk family members. A Registry Advisory Committee has been established under the NHMRC Guidelines, and includes a representative from each major recruitment centre. This committee approves all decisions relating to the Registry including approval of research studies. A National Genetic Heart Disease Registry will provide a valuable resource to further our knowledge of the clinical and genetic aspects of these diseases. Since most of the current data about the prevalence, natural history and outcomes of genetic heart diseases has emanated from the United States and Europe, characterising these Australian populations will be of significant benefit, allowing for more informed and specific health care planning and resource provision

Phased-array intracardiac echocardiography for defining cavotricuspid isthmus anatomy during radiofrequency ablation of typical atrial flutter

The definitive version is available at www.blackwell-synergy.comIntroductionCavotricuspid isthmus (CTI) topography includes ridges, pouches, recesses, and trabeculations. These features may limit the success of radiofrequency ablation (RFA) of typical atrial flutter (AFL). The aim of this study was to assess the utility of phased-array intracardiac echocardiography (ICE) for imaging the CTI and monitoring RFA of AFL.Methods and resultsFifteen patients (mean age 64 +/- 9 years) underwent ICE assessment (imaging frequency 7.5-10 MHz) before and after RFA of AFL. The ICE catheter was positioned at the inferior vena cava-right atrial junction and the following parameters were measured: (1) CTI length from the tricuspid valve to the eustachian ridge; (2) extent of CTI pouching; and (3) thickness pre/post RFA of the anterior, mid, and posterior CTI. CTI length was 35 +/- 6 mm at end-ventricular systole but shorter (30 +/- 6 mm) and more pouched at end-ventricular diastole (P = 0.02). A pouch or recess was seen in 11 of 15 patients (mean depth 6 +/- 2 mm). The septal CTI was more pouched than the lateral CTI, but the latter had more prominent trabeculations. Trabeculations were seen in 10 of 15 patients, and at these locations the CTI was 4.6 +/- 1 mm thick. Anterior, mid, and posterior CTI thickness pre-RFA was 4.1 +/- 0.8, 3.3 +/- 0.5, and 2.7 +/- 0.9 mm, respectively (P ConclusionPhased-array ICE permits novel real-time CTI imaging with excellent endocardial resolution and may facilitate RFA of AFL.Joseph B. Morton, Prashanthan Sanders, Neil C. Davidson, Paul B. Sparks, Jitendra K. Vohra, Jonathan M. Kalma

Focal atrial tachycardia arising from the mitral annulus: Electrocardiographic and electrophysiologic characterization

© 2003 by the American College of Cardiology Foundation. Published by Elsevier Inc.ObjectivesThe study was done to characterize the electrocardiographic and electrophysiologic features of focal atrial tachycardia originating at the mitral annulus (MA).BackgroundThough the majority of left atrial tachycardias originate around the ostia of the pulmonary veins, only isolated reports have described focal tachycardia originating from the MA.MethodsSeven patients of a consecutive series of 172 patients undergoing radiofrequency ablation for focal atrial tachycardia are reported. Electrophysiologic study involved catheters positioned along the coronary sinus (CS), crista terminalis (CT), His bundle, and a mapping/ablation catheter.ResultsAll seven patients had tachycardia foci originating from the superior region of the MA in close proximity to the left fibrous trigone and mitral-aortic continuity. These foci demonstrated a characteristic P-wave morphology and endocardial activation pattern. The P-wave morphology in the precordial leads typically showed a biphasic pattern, with an inverted component followed by an upright component. The P-wave was consistently of low amplitude in the limb leads. Earliest endocardial activity occurred at the His bundle region in all seven patients. In general, CS activation was proximal to distal, and mid-CT activation was earlier than high or low CT. Ablation was successful at the superior aspect of the MA in all patients.ConclusionsThe MA is an unusual but important site of origin for focal atrial tachycardia, with a propensity to be localized to the superior aspect. It can be suspected as a potential anatomic site of tachycardia origin from analysis of P-wave morphology and the atrial endocardial activation sequence map. Using mapping targeted to anatomic structures achieved a high success rate for ablation.Peter M. Kistler, Prashanthan Sanders, Azlan Hussin, Joseph B. Morton, Jitendra K. Vohra, Paul B. Sparks and Jonathan M. Kalma

P-Wave Morphology in Focal Atrial Tachycardia Development of an Algorithm to Predict the Anatomic Site of Origin

ObjectivesThe purpose of this study was to perform a detailed analysis of the P-wave morphology (PWM) in focal atrial tachycardia (AT) and construct and prospectively evaluate an algorithm for identification of the anatomic site of origin.BackgroundAlthough smaller studies have described the PWM from particular anatomic locations, a detailed algorithm characterizing the likely location of a tachycardia associated with a P-wave of unknown origin has been lacking.MethodsThe PWMs for 126 consecutive patients undergoing successful radiofrequency ablation of 130 ATs are reported. P waves were included only when the onset was preceded by a discernible isoelectric segment. P waves were classified as positive (+), negative (−), isoelectric, or biphasic. Sensitivity, specificity, and predictive values were calculated. On the basis of these results, an algorithm was constructed and prospectively evaluated in 30 new consecutive ATs.ResultsThe distribution of ATs was right atrial (RA) in 82 of 130 (63%) and left atrial (LA) in 48 of 130 (37%). Right atrial sites included crista (n = 28), tricuspid annulus (n = 29), coronary sinus (CS) ostium (n = 14), perinodal (n = 7), right septum (n = 1), and RA appendage (n= 3). Left atrial sites included pulmonary veins (n = 32), mitral annulus (n = 8), CS body (n= 3), left septum (n = 3), and LA appendage (n = 2). In electrocardiographic lead V1, a negative or +/− P-wave demonstrated a specificity of 100% for a RA focus, and a + or −/+ P-wave demonstrated a sensitivity of 100% for a LA focus. A characteristic PWM was associated with high sensitivity and specificity at common atrial sites for tachycardia foci. A P-wave algorithm correctly identified the focus in 93%.ConclusionsCharacteristic PWMs corresponding to known anatomic sites for focal AT are associated with high specificity and sensitivity. A P-wave algorithm correctly identified the site of tachycardia origin in 93%