Electric Impulse Therapy in Cardiac Tachyarrhythmias-Theoretical Principles and Clinical Aspects

This paper reviews 14 years of experimental and clinical research work. Concise concepts of electric impulse therapy in cardiac tachyarrhythmias by application of capacitor discharges are described. Experiments carried out on dogs showed that pure undamped capacitor discharges caused more damage to myocardial function than damped ones. The degree of damage depends upon the parameters of the impulse. When identical energies are applied, a high voltage impulse causes greater functional and morphological damage than impulses at lower voltages. For electrical impulse therapy of cardiac arrhythmias, damped impulses have greater advantages. Lower threshold voltage and less energy are required. The duration of the impulse plays an important role in determining the lowest voltage on the electrodes. In the experiments described the lowest voltage was achieved for an impulse duration of 10 ms. Parameters of 4 to 10 ms appear to have practical advantage from the point of view of ventricular defibrillation. These damped impulses at values above the voltage threshold, i.e. from at least 2.5 kV upwards, do not cause ventricular fibrillation in any phase of the heart cycle. Therefore synchronized application of the capacitor discharge is not required. Experimental results were confirmed by clinical practice and presented identical findings. Finally, two examples of an unsynchronized portable defibrillator are shown. These instruments have their own battery power source, can be operated independent of electrical power lines, and are suitable for use both in emergency cases and routine treatment of all kinds of cardiac tachyarrhythmias.