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

The nature of most syncopal episodes, previously unknown, was recently elucidated by new diagnostic techniques such as the use of the tilt test. The vasovagal syncope can be clinically diagnosed by means of the tilt test. The transitory loss of consciousness during prolonged orthostasis is typically associated with sudden hypotension and bradycardia, which are commonly preceded by relative tachycardia and by premonitory symptoms such as pallor, nausea, asthenia, yawns, hyperventilation, mydriasis, humming, lasting several minutes. The nature of the vasovagal reflex is now better understood: in subjects with vasovagal syncope, during prolonged orthostasis, it was observed a fall in the venous return, inducing an increased sympathetic drive to the heart (with positive inotropic and chronotropic effect) and a lower ventricular filling. The powerful contraction around an almost empty cardiac chamber induces the activation of ventricular mechanoreceptors, and through a reflex mechanism, a sudden increase in the vagal and a sudden reduction in the sympathetic drive. These autonomic changes are responsible for a sudden hypotension and bradycardia. The discussion is still open about the origin of the reduced venous return: it probably originates from a redistribution in the blood volume, due to a venous pooling in the lower limbs or from a reduced muscle tone, because many subjects with vasovagal syncope are slender and with less developed muscle apparatus. Others suggest that a reduction in the sympathetic drive to the vessels, responsible for a progressive hypotension in the minutes preceding syncopal episodes, is the origin of the reduced venous return. In this review a diagnostic pattern for the assessment of the vasovagal syncope is suggested. The medical history, clinical examination, electro- and echocardiogram, chest x-ray identify two main groups of patients (with or without cardiopathy) who will follow different diagnostic protocols. The therapy of vasovagal syncope, which is based on beta-blockers, scopolamine, dysopiramide and plasma expanders, is reviewed.
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PMID:[Vasovagal syncope]. 851 54

Patients with syncope of unknown etiology may suffer from recurrent disability. Syncopal episodes are often too infrequent and unpredictable for detection with conventional ambulatory monitoring techniques. A symptom-rhythm correlation is a frequently unattainable gold standard in many patients. Clinicians must often rely on the results of laboratory testing to make an inferential determination of the etiology of spontaneous syncope. Electrophysiological testing has a role in patients with structural heart disease and suspected ventricular arrhythmias, but is negative in 14% to 70% of patients studied and has a limited role in patients without structural heart disease. The external loop recorder is an ambulatory device worn for weeks or even months that freezes the preceding rhythm strip after an episode of spontaneous syncope. This device is useful in patients with frequent symptoms but is hampered by lack of patient compliance and technical limitations. In the absence of a diagnosis after extensive testing, an empirical trial based on index of suspicion may be warranted. This may include implantation of a pacemaker for suspected bradycardia or empirical therapy directed at a tachycardia. Finally, recent reports of an insertable loop recorder suggest a high diagnostic yield with a broad spectrum of etiologies in patients with recurrent syncope in spite of negative noninvasive and electrophysiological testing. In the future, such a device may assume a prominent role in the investigation of syncope.
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PMID:Recurrent unexplained syncope: diagnostic and therapeutic approach. 919 91

Syncope is a common clinical problem with multiple potential causes. Recent studies have delineated the natural history and most frequent causes of recurrent syncopal episodes. The medical history and detailed physical examination are particularly important. Clinical electrophysiologic testing has also played a critical role in assessing causes of syncope, but recent reports suggest that its value lies primarily in treating patients with evident underlying structural heart disease. Among patients without structural heart disease, the neurally mediated forms of syncope, particularly the emotional or vasovagal faint, are by far the most common basis for symptoms. In these patients, head-up tilt-table testing has proved particularly valuable in defining the origin of the problem and in assessing therapeutic alternatives. Protocols for upright tilt-table testing remain in evolution. Nonetheless, current practice suggests that 25-minute tilt-test duration is reasonable if pharmacologic provocation is to be used for further evaluation of patients with negative initial findings. However, for those laboratories that do not favor pharmacologic intervention, a 45-minute tilt-test duration is probably essential. Overall, tilt-table testing has proved relatively sensitive and appropriately specific for the identification of patients susceptible to neurally mediated syncopal syndromes.
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PMID:Tilt-table testing and syncope. 1014 50

The long QT syndrome (LQTS) is a heart disorder which is characterised by the prolongation of the QT interval of the surface electrocardiogram and is associated with malignant arrhythmias, syncopal episodes, torsade de pointes form ventricular tachycardias and an increased risk of sudden cardiac death. There are two familial forms of LQTS, the autosomal dominant Romano-Ward syndrome and the autosomal recessive Jervell-Lange-Nielsen syndrome which is associated with congenital senzorineural deaf-mutism. Recent advances in molecular genetics have allowed to identify mutations in four genes, KvLQT1 (11p15.5), HERG (7q35), SCN5A (3p21) and minK (21q22), which cause LQTS. There is a fifth genetic locus known on chromosome 4 (4q25-27), where the disease causing gene has not been identified yet. As LQTS genes code proteins which form sodium and potassium channels of the heart, LQTS can be regarded as the disease of cardiac ion channels. The KvLQT1 and minK genes code the slowly activating, delayed rectifier (Iks) potassium channel, the HERG gene code the rapidly activating, delayed rectifier (Ikr) potassium channel of the heart, while the SCN5A gene codes a cardiac sodium channel. Mutations in KvLQT1, minK and HERG genes affects repolarising, rectifier potassium currents, while SCN5A mutations cause delayed inactivation and reopening of the cardiac sodium channel, which initiates the depolarisation of cardiac cells. Both alterations result in a prolongation of cardiac repolarisation which is represented in the elongation of the QT interval. Elucidation of the genetic base of the disease provided new tools in the clinical management of LQTS. It has been shown that changes in the repolarisation parameters on the ECG may be predictive for the causative gene and different LQTS genes are associated with different clinical picture. More importantly, it is possible to use "gene-specific" therapy in LQTS which specifically targets ion channels affected by given gene mutations.
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PMID:[Molecular genetics of the long QT syndrome: clinical aspects]. 1061 47

Syncope is the abrupt loss of consciousness and postural tone that reverses without intervention. Typically, syncopal episodes in pediatric patients are brief, lasting seconds (rarely minutes), and are followed by complete recovery without residual neurological sequelae. Syncopal presentations may be dramatic and lead family members and primary care providers to suspect a malignant cardiac condition, prompting referral to a pediatric cardiologist. Significant advances in the understanding of syncope in infants, children, and adolescents have occurred in the past decade. This review emphasizes neurally mediated syncope, but other etiologies are reviewed to complete the spectrum encountered by pediatric cardiologists. Some clues are provided to distinguish the more common and benign forms of syncope from those due to significant underlying heart disease.
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PMID:Current approach to pediatric syncope. 1105 Feb 76

Patients with unexplained syncope are often considered candidates for prolonged monitoring or empiric pacing when noninvasive and invasive investigations fail to provide a diagnosis. Identifying the outcome of patients undergoing prolonged monitoring that would ultimately benefit from empiric pacing may permit a cost-effective approach to resolution of syncope. Two hundred and six patients (age 57 +/- 18 years, 57% male) underwent prolonged monitoring with an implanted loop recorder for syncope of unknown origin. The median number of previous syncopal episodes was four (mean 29 +/- 133). Prior tilt testing was performed in 63% of patients, and electrophysiological testing in 46%. Symptoms recurred during follow-up in 142 patients (69%). Recurrence was associated with bradycardia leading to pacemaker implantation in 35 patients (17.0%), tachycardia in 12 (5.8%), sinus rhythm in 63 (30.6%), neurally mediated syncope based on rhythm and clinical assessment in 22 (11%), and failed activation in 10 (5%). Logistic regression analysis of baseline variables found that age was the only independent variable that predicted the need for pacing, associated with a 3% increase in risk per advancing year of age (odds ratio 1.027, P = 0.026). Despite this finding, no age group could be identified in which the likelihood of requiring pacing exceeded 30%. Logistic regression also found that patients with structural heart disease were less likely to experience recurrent symptoms during monitoring (49% vs 78%, P = 0.001) and that advancing age was associated with earlier recurrence of symptoms (P = 0.01). The etiology of recurrent syncope is diverse and cannot be predicted by baseline clinical variables. Empiric pacing appears to have little role in the management of this patient population.
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PMID:Predicting the outcome of patients with unexplained syncope undergoing prolonged monitoring. 1187 34

The newer implantable loop recorders recently introduced (Reveal Plus. Medtronic Inc, Minneapolis, MN, U.S.A.). equipped with auto activation capabilities, are expected to expand our diagnostic abilities in the investigation of syncopal episodes. The case presented here is that of a man with pre-syncopal and syncopal episodes, without organic heart disease, in whom the device was auto-activated due to undersensing and the recorded strip imitated complete heart block. Increased attention should be given by the interpreter of the device's recordings to avoid false positive diagnoses that might lead to serious therapeutic actions.
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PMID:Implantable loop recorder undersensing mimicking complete heart block. 1213 56

Chloroquine has been widely used in rheumatological treatment, but potential severe side effects require careful follow-up. Cardiac damage is not a common consequence, but its clinical relevance has not yet been described. We report the case of a 58-year-old woman with rheumatoid arthritis, in whom chronic chloroquine use resulted in major irreversible cardiac damage. She presented with syncopal episodes due to complete atrioventricular block confirmed by electrophysiological study whose changes were concluded to be irreversible and a permanent pacemaker was indicated. Endomyocardial biopsy was also performed to search for histopathological and ultrastructural cardiac damage. We also reviewed the 22 cases of chloroquine-induced cardiopathy described to date as well as its pathophysiology.
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PMID:Cardiac damage from chronic use of chloroquine: a case report and review of the literature. 1216 48

Brugada syndrome is an inherited cardiac disorder caused by mutations in the SCN5A gene encoding the cardiac sodium channel alpha-subunit, and potentially leads to ventricular fibrillation and sudden death. We report a case of a novel SCN5A mutation associated with Brugada syndrome. A 51-year-old man suffered from recurrent nocturnal syncopal attacks due to polymorphic ventricular tachycardia. His electrocardiogram showed ST-segment elevation in V1-V3 leads, but there was no evidence of structural heart disease. DNA sequence analysis of SCN5A in this patient revealed a missense mutation (R282H) in the S5-pore region of domain I. This mutational change was not present in 100 healthy Japanese controls. In the patient's family, a 36-year-old brother had died suddenly. Genetic analysis identified two other carriers of the R282H mutation, who had ST-segment elevation and slightly increased QRS widths, but they experienced no syncopal episodes or ventricular fibrillation. Electrophysiological investigation of the R282H mutant channel expressed in cultured cells showed a severe reduction in sodium current density and a mild positive shift of activation curve. R282H did not enhance intermediate inactivation. Single-channel conductance of R282H was slightly decreased compared with WT. The electrophysiological characteristics of the R282H channel are suggested to be closely related to the clinical phenotype of Brugada syndrome.
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PMID:Clinical and electrophysiological characteristics of Brugada syndrome caused by a missense mutation in the S5-pore site of SCN5A. 1582 79

We sought to identify the electrophysiologic basis of life-threatening events associated with polymorphic ventricular tachycardia (PVT) in young patients with heterozygous KCNJ2 mutations. PVT describes a beat-to-beat alternating QRS axis and morphology during ventricular tachycardia. PVT may be well tolerated and even asymptomatic in young patients without other heart disease, but an association with syncope, cardiac arrest, or sudden death has long been known. Little is known of the basis of life-threatening events associated with PVT in this setting. We identified heterozygous KCNJ2 mutations (R67W and C101R respectively) in 2 adolescents with PVT (cycle length > 375 ms, < 160 beats/minute). Biophysical properties of wild-type and mutant KCNJ2 channels were characterized during heterologous expression in Xenopus oocytes. Despite a large tachycardia burden, neither patient experienced symptoms during electrocardiographic documentation of PVT. One patient had a history of cardiac arrest, but neither had other evidence of heart disease. Both patients were treated with an implantable cardioverter-defibrillator (ICD). In one patient, ICD interrogation identified rapid ventricular tachycardia (cycle length of 190 to 270 ms), terminated with a single 29-J asynchronous shock, as the cause of 2 syncopal episodes occurring 19 months apart. Biophysical characterization of KCNJ2-C101R demonstrated a loss-of-function and a dominant-negative effect on Kir2.1. Similar effects were previously observed for KCNJ2-R67W. Heterozygous mutations in KCNJ2 can cause life-threatening ventricular arrhythmias. Arrhythmia documented during cardiac arrest is rapid ventricular tachycardia; ICD is effective therapy for cardiac arrest in patients with PVT due to KCNJ2 mutation.
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PMID:Polymorphic ventricular tachycardia and KCNJ2 mutations. 1585 Nov 60


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