Zeitschrift für Kardiologie
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The molecular genetic background of inherited cardiac arrhythmias has only recently been uncovered. This late development in comparison to other inherited cardiac disorders has partly been due to the high mortality and early disease onset of these arrhythmias resulting in mostly small nucleus families. Thus, traditional genetic linkage studies, which are based on the genetic information obtained from large multi-generation families, were made difficult. ⋯ The reduced penetrance and variable expressivity associated with the LQT mutations remain still to be explained. First insights into the complex actions of mutations are being extracted, from expression data; these preliminary results may lead to potential implications for a specific (gene-site directed) therapy. This paper discusses the current data on molecular genetics and genotype-phenotype correlations in LQT syndrome and related disorders and the potential implications for diagnosis and treatment.
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Antiarrhythmic drugs can be divided into four Vaughan Williams classes (I-IV) according to defined electrophysiological effects on the myocardium. Thus, the Vaughan Williams classification also coincides with the main myocardial targets of the antiarrhythmics, i.e., myocardial sodium-, potassium-, and calcium-channels or beta-adrenergic receptors. A more detailed characterization which is also based on the myocardial targets of a drug is given by the "Sicilian Gambit" approach of classification. ⋯ Class-III substances inhibiting the slowly activating IKs component are currently under investigation and are expected to show a direct rate dependence. Experimental data available so far point to an action potential prolonging effect at least independent of rate. However, it is uncertain whether proarrhythmic effects can be thus avoided, especially in light of the fact that one form of congenital QT syndrome (LQT1) seems to be linked to dysfunction of the IKs-channel.
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Review Comparative Study
[Endocardial mapping and high frequency catheter ablation of ventricular tachycardia after myocardial infarction].
Recurrent ventricular tachycardia in the setting of remote myocardial infarction are frequently resistant to antiarrhythmic drug treatment. Endocardial mapping and ablation is feasible in case of hemodynamically tolerable and reproducibly inducible forms. Identification of critical components of the reentrant circuit is mainly guided by entrainment mapping and the analysis of the post-pacing interval. ⋯ Furthermore, this method can be life-saving in the setting of incessant forms. Currently, catheter ablation represents an adjunctive treatment to antiarrhythmic drugs and the implantation of a cardioverter-defibrillator. Improvement of mapping and ablation technologies may help to further increase the efficacy of this treatment strategy in the near future.
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For the emergency treatment of sustained, hemodynamically stable ventricular tachycardia, antiarrhythmic drugs are the therapy of choice. Mostly class I antiarrhythmic drugs, such as lidocaine or ajmaline, are preferred. ⋯ For the primary prevention of sudden cardiac death, beta-blockers and/or amiodarone are the only effective drugs. In the secondary prevention, only the implantable cardioverter/defibrillator has proved to improve the prognosis of the patients.
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Surgical treatment of proximal aortic disease traditionally consists of composite replacement of valve and aorta. Recent reconstructive procedures on the aortic root allow for treatment of aortic dilatation and concomitant aortic valve regurgitation without the associated disadvantages of mechanical heart valves. From 10/95 to 09/99 we treated 84 patients for regurgitation of the aortic valve and dilatation of the aortic root. ⋯ These gradients were thus significantly lower than the increased gradients of patients after composite replacement. Application of reconstructive procedures to the aortic root allows for restoration of aortic valve function in the majority of patients. Disadvantages of heart valve prostheses can be avoided, and the hemodynamic performance of the reconstructed valve appears almost physiologic.