[Dangerous arrhythmias].

The usual frequent tachyarrhythmias well known to the specialists in internal medicine, such as ventricular tachycardia and ventricular fibrillation, are not discussed in this publication; nor are the bradycardias connected with the sick sinus syndrome or with atrioventricular block of higher degrees (with one exception). In the first section a stratification of the risk after myocardial infarction is presented including the therapeutic implications. Severely reduced left ventricular function is of most negative prognostic value. After the poor results of the CAST study, which revealed a threefold greater mortality of patients with myocardial infarction and severely impaired left ventricular function under treatment with some antiarrhythmic agents of class I (Vaughan Williams), compared to patients on placebo, cardiologists have resorted to beta-blocking agents again or, in patients with severely reduced left ventricular function, to amiodarone (Cordarone), based on preliminary results of current amiodarone studies. For selected patients, implantable cardioverter-defibrillator (ICD) devices seem to have a promising future. In the second part some rare and persistent arrhythmias are mentioned that may induce heart failure in an otherwise healthy heart, such as ectopic atrial tachycardia, atrioventricular junctional tachycardia with RP > PR, His bundle tachycardia and idiopathic ventricular tachycardia (this arising only in infants). In the third section some infrequent forms of tachycardia are discussed that may be sporadically encountered in a medical office. Ventricular tachycardia of the type "torsades de pointes" is associated with on a prolonged QT or QTU time in the ECG and is mainly due to drugs (especially antiarrhythmic agents). The therapy consists in withdrawal of the drug and may include magnesium intravenously and even a temporary pacemaker. The tachycardias associated to the Wolff-Parkinson-White syndrome have gained more practical importance since it has become possible to localize the accessory pathway involved by mapping with subsequent interruption by surgery or ablation. In atrial fibrillation with an ECG pattern of delta waves at the beginning of QRS complexes, digitalis and verapamil are contraindicated since they may induce ventricular fibrillation. The Mobitz type is one, and the most rare, form of the three atrioventricular blocks of second degree. It is almost always combined with an infra-His-bundle conduction disturbance in the conducted beats, and is an immediate precursor of complete atrioventricular block. Patients with the Mobitz block usually need a pacemaker. Finally, two case reports are presented to show that superficial and incorrect diagnosis of an arrhythmia is followed by incorrect and dangerous therapy.(ABSTRACT TRUNCATED AT 400 WORDS)