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Query: UMLS:C0018799 (heart disease)
 34,133 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Several invasive and noninvasive tests for risk stratification of sudden cardiac death have been studied, mostly in the context of structural heart disease such as coronary artery disease (CAD), cardiomyopathy, and heart failure. Tests such as MTWA (repolarization abnormality) and SAECG (depolarization abnormality) have high negative predictive values but a low positive predictive value in patients with myocardial infarction or cardiomyopathy. Recently, we described the presence of a fragmented QRS complexes (fQRS) on a routine 12-lead electrocardiogram as another marker of depolarization abnormality. fQRS represents conduction delay caused by myocardial scar in patients with CAD. However, fQRS is not specific for CAD and is also encountered in other myocardial diseases such as cardiomyopathy and congenital heart disease. fQRS is associated with increased mortality and arrhythmic events in patients with CAD. fQRS has also been defined as a marker of arrhythmogenic right ventricular dysplasia/cardiomyopathy and Brugada syndrome. In Brugada syndrome, the presence of fQRS predicts episodes of ventricular fibrillation during follow-up. Therefore, the utility of fQRS in risk stratification of sudden cardiac death needs to be explored further, especially in nonischemic cardiomyopathy and heart failure.
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PMID:Fragmented QRS: a predictor of mortality and sudden cardiac death. 1925 Dec 29

Inherited arrhythmias and conduction system diseases are known causes of sudden cardiac death and are responsible for significant mortality and morbidity in patients with congenital heart disease and electrical disorders. Knowledge derived from human genetics and studies in animal models have led to the discovery of multiple molecular defects responsible for arrhythmogenesis. This review summarizes the molecular basis of inherited arrhythmias in structurally normal and altered hearts.On the cellular and molecular levels, minor disturbances can provoke severe arrhythmias. Ion channels are responsible for the initiation and propagation of the action potential within the cardiomyocyte. Structural heart diseases, such as hypertrophic or dilated cardiomyopathies, increase the likelihood of cardiac electrical abnormalities. Ion channels can also be up- or down-regulated in congenital heart disease, altering action potential cellular properties and therefore triggering arrhythmias. Conduction velocities may be inhomogeneously altered if connexin function, density or distribution changes. Another important group of electrophysiologic diseases is the heterogeneous category of inherited arrhythmias in the structurally normal heart, with a propensity to sudden cardiac death. There have been many recent relevant discoveries that help explain the molecular and functional mechanisms of long QT syndrome, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia, and other electrical myopathies. Identification of molecular pathways allows the identification of new therapeutic targets, for both disease palliation and cure. As more disease-causing mutations are identified and genotypic-phenotypic correlation is defined, families can be screened prior to symptom-onset and patients may potentially be treated in a genotype-specific manner, opening the doors of cardiac electrophysiology to the emerging field of pharmacogenomics.
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PMID:Molecular mechanisms of inherited arrhythmias. 1944 May 13

Conduction disorders result in cardiac arrhythmias that may be fatal. Histiocytoid cardiomyopathy, Arrhythmogenic right ventricular dysplasia, Isolated noncompaction of the left ventricle, Long QT syndrome (LQTS) and Brugada syndrome, are all well described. Congenital short QT syndrome is a new familial primary electrical disease of the heart, which is characterized by abnormally short QT interval and paroxysmal atrial and ventricular tachyarrhythmias, including sudden cardiac death. An autosomal dominant mode of inheritance has been suggested. Catecholaminergic polymorphic ventricular tachycardia is an inherited disease and occurs in the absence of structural heart disease or known associated syndromes. Although the histological appearance of some of these disorders may be diagnostic, molecular analysis is necessary to define clearly the particular type of cardiomyopathy.
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PMID:Cardiac conduction disorders in children. 1948 66

In approximately 10-20% of all sudden deaths, no structural cardiac abnormalities can be identified. Important potential causes of sudden cardiac deaths in the absence of heart disease are primary electrical diseases such as Brugada syndrome, long QT syndrome (LQTS), short QT syndrome (SQTS), and catecholaminergic polymorphic ventricular tachyarrhythmias (CPVT). The resting ECG and the ECG under exercise are pivotal for the diagnosis of ion channel diseases. Molecular genetic screening can reveal underlying mutations in a variable degree among the cardiac ion channel diseases in up to 70% (LQTS) and may identify individuals with incomplete penetration of the disease. In patients with primary electrical diseases, specific clinical triggers for arrhythmic events such as syncope or sudden cardiac death have been identified including exercise, strenuous activity, auditory stimuli, or increased vagal tone. Young, otherwise healthy individuals are likely to be involved in sports activity. Therefore, special attention has to be given to advise these patients. Competitive sports and vigorous exercise are contraindications in almost all patients. Even recreational exercise may have to be avoided in phenotypically overt patients or silent gene carriers depending on the underlying disease.
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PMID:Channelopathies: Brugada syndrome, long QT syndrome, short QT syndrome, and CPVT. 1957 58

In the last decade there have been considerable advances in the understanding of the pathophysiology of malignant ventricular tachyarrhythmias (VA) and Sudden Cardiac Death (SCD). Over 80% of SCD occurs in patients with organic heart disease. However, approximately 10-15% of SCD occurs in the presence of structurally normal heart and the majority of those patients are young. In this group of patients, changes in genes encoding cardiac ion channels produce modification of the function of the channel resulting in an electrophysiological substrate of VA and SCD. Collectively these disorders are referred to as Cardiac Ion Channelopathies. The 4 major syndromes in this group are: The Long QT Syndrome (LQTS), the Brugada Syndrome (BrS), the Short QT Syndrome (SQTS), and the Catecholaminergic Polymorphic VT (CPVT). Each of these syndromes includes multiple subtypes with different and sometimes complex genetic abnormalities of cardiac ion channels. Many are associated with other somatic and neurological abnormalities besides the risk of VA and SCD. The current management of cardiac ion channelopathy could be summarized as follows: 1) in symptomatic patients, the implantable cardioverter defibrillator (ICD) is the only viable option; 2) in asymptomatic patients, risk stratification is necessary followed by the ICD, pharmacotherapy, or a combination of both. A genotype-specific approach to pharmacotherapy requires a thorough understanding of the molecular-cellular basis of arrhythmogenesis in cardiac ion channelopathies as well as the specific drug profile.
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PMID:Role of pharmacotherapy in cardiac ion channelopathies. 1960 60

Brugada syndrome (BrS) is a condition characterized by a distinct ST-segment elevation in the right precordial leads of the electrocardiogram and, clinically, by an increased risk of cardiac arrhythmia and sudden death. The condition predominantly exhibits an autosomal dominant pattern of inheritance with an average prevalence of 5:10,000 worldwide. Currently, more than 100 mutations in seven genes have been associated with BrS. Loss-of-function mutations in SCN5A, which encodes the alpha-subunit of the Na(v)1.5 sodium ion channel conducting the depolarizing I(Na) current, causes 15-20% of BrS cases. A few mutations have been described in GPD1L, which encodes glycerol-3-phosphate dehydrogenase-1 like protein; CACNA1C, which encodes the alpha-subunit of the Ca(v)1.2 ion channel conducting the depolarizing I(L,Ca) current; CACNB2, which encodes the stimulating beta2-subunit of the Ca(v)1.2 ion channel; SCN1B and SCN3B, which, in the heart, encodes beta-subunits of the Na(v)1.5 sodium ion channel, and KCNE3, which encodes the ancillary inhibitory beta-subunit of several potassium channels including the Kv4.3 ion channel conducting the repolarizing potassium I(to) current. BrS exhibits variable expressivity, reduced penetrance, and "mixed phenotypes," where families contain members with BrS as well as long QT syndrome, atrial fibrillation, short QT syndrome, conduction disease, or structural heart disease, have also been described.
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PMID:The genetic basis of Brugada syndrome: a mutation update. 1960 73

Brugada syndrome (BrS) is a primary electrical heart disease, which can lead to sudden cardiac death. In older patients with BrS, the disease may coexist with ischaemic heart disease (IHD) and recent studies support a synergistic proarrhythmic effect of the two disease entities. We report a case that illustrates this. The index patient was a middle-aged patient with BrS traits, IHD, and aborted sudden cardiac death. Mutation analysis discovered a novel mutation P468L in the Na(V)1.5 sodium channel. Surprisingly, voltage-clamp experiments on the wild-type and mutant Na(V)1.5 channels expressed in HEK cells revealed no functional effect of the mutation. In a patient like ours, the distinction between IHD and BrS as the cause of an aborted sudden cardiac death is hard to establish and mounting evidence shows that coexistence of the two may have a synergistic proarrhythmic effect.
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PMID:A Novel SCN5A Mutation in a Patient with Coexistence of Brugada Syndrome Traits and Ischaemic Heart Disease. 1982 66

Since it was first described approximately 15 years ago, the Brugada Syndrome has spurred a significant quantity of interest in its underlying mechanism and physiology. The Brugada electrocardiographic pattern is characterized by right bundle branch block morphology and ST segment elevations in the right precordial leads with an absence of identifiable underlying structural heart disease. The syndrome is clinically significant since these patients are at a higher risk of developing malignant ventricular arrhythmias. One of the mechanisms behind the disorder involves mutations in specific myocardial sodium channels. Furthermore, these electrocardiographic changes appear to be temperature dependent. We present the case of a 35-year-old male who presented with intestinal Shigellosis and was also found to have Brugada-type electrocardiographic changes on ECG. The electrocardiographic changes that were present when the patient was admitted and febrile resolved following antibiotic therapy and defervescence.
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PMID:Fever associated with gastrointestinal shigellosis unmasks probable brugada syndrome. 2006 6

The Brugada syndrome is an inherited cardiac disorder initially described in 1992 by Pedro and Josep Brugada, with variable electrocardiographic features characteristic of right bundle-branch block, persistent ST-segment elevation in the precordial leads (VI-V3) at rest and sudden cardiac death. The genetic abnormalities that cause Brugada syndrome have been linked to mutations in the ion channel gene SCN5A which encodes for the alpha-subunit of the cardiac sodium channel. A consensus conference report published in 2002 described the diagnostic criteria for the Brugada syndrome and described the three distinct types of Brugada syndrome. In 2005, a second consensus report was published which described the risk stratification and approaches to therapy. Two specific types of ST-segment elevation, coved and saddleback, are observed in the Brugada syndrome, the former of which is reported to relate to a higher incidence of ventricular tachycardial ventricular fibrillation (VTNF) and sudden cardiac death.The objective of this paper is to review the genetics and the molecular biology behind the Brugada syndrome, the diagnostic criteria, including clinical and electrocardiographic characteristics, and current management.
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PMID:The Brugada syndrome. 2012 57

Brugada syndrome is characterized by the electrocardiographic (ECG) pattern of right bundle-branch block (RBBB) with a high take-off, coved ST-segment elevation in the precordial leads V1 to V3, and the risk of sudden cardiac death. Typically, there is no evidence of structural heart disease. In many cases, Brugada syndrome has been linked to a mutation of the gene SCN5A, which encodes for the fast cardiac sodium channel. In patients with the Brugada syndrome, pharmacologic sodium channel blockade can increase the degree of ST-segment elevation. Interestingly, even in patients with a normal baseline ECG and no clinical suggestion of the Brugada syndrome, toxic doses of class I antiarrhythmic agents as well as toxicities with several nonantiarrhythmic drugs that possess sodium channel blocking properties can induce the Brugada ECG abnormality. Specifically, the beta-receptor blocker propranolol, at high doses, binds to the cardiac sodium channels and inhibits sodium uptake. In this report, we describe a case of severe propranolol toxicity, which resulted in the Brugada ECG pattern in an otherwise healthy individual who had no clinical or ECG suggestion of the genetically determined Brugada syndrome.
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PMID:Brugada-pattern electrocardiogram in propranolol intoxication. 2015 10


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