Engineering and physiological considerations of direct capacitor-discharge ventricular defibrillation

The amount of energy, current and charge per gram of heart were determined on a series of 36 dogs. The data, which are examined on the basis of current duration (time constant), show that the three criteria are different. The optimum duration range using energy as a criterion is 0·03–3 ms. Minimum peak current was required with a 4 ms duration capacitor discharge pulse. There was no optimum duration for minimum charge. It was found that although short-duration current (0·02–3·0 ms) produced defibrillation, the high current required impaired the contractility of the ventricles. From this study, the optimum range of capacitor-discharge current for defibrillation is 0·3–4 ms. Estimates are presented on the amounts of energy, current and charge to defibrillate the ventricles of large animals.SommaireLes quantités d'énergie, de courant et de charge par un gramme de coeur ont été déterminées dans une série de 36 coeurs canins. Les données acquises, examinées sur la base de la durée du courant (constante de temps), démontrent que les trois critériums sont différents. La durée optimale est de 0,03–3 ms quand l'énergie est prise comme critérium. Un coruant de crête minimum était nécessaire quand la durée de la décharge du condensateur était 4 ms. Il n'y avait pas de durée optimale pour une charge minimum. On a trouvé que des impulsions de courant de courte durée (0,02–3,0 ms) causaient la défibrillation mais le courant élevé qui était nécessaire empêchait la contractilité des ventricules. La conclusion de notre étude est que la gamme optimale de courant de décharge capacitive comme moyen de la défibrillation est de 0,3 à 4 ms. Les quantités d'énergie, de courant et de charge électrique nécessaires pour la défibrillation des ventricules en gros animaux ont été evaluées approximativement.ZusammenfassungDer Betrag an Energie, Strom und Ladung pro Gramm Herz wurde in einer an Hand von 36 Hunden durchgeführten Versuchsreihe bestimmt. Die Werte, die auf der Grundlage der Stromdauer (Zeitkonstante) untersuchtwurden, zeigten, daßsich die drei Kriterien verschieden verhalten. Wählt man die Energie als Kriterium, so liegt der optimale zeitliche Bereich zwischen 0,03 und 3 ms. Der niedrigste Spitzenstrom wurde mit Kondensatorentladungsimpulsen von 4 ms Dauer benötigt. Für die Mindestladung ergab sich keine optimale Impulsdauer. Es stellte sich heraus, daß kurzzeitige Stromimpulse (0,02–3,0 ms) das Herzkammerflattern wohl unterdrückten, der hierzu erforderliche starke Strom jedoch die Kontraktilität der Herzkammern heruntersetzte. Aus der Studie ergab sich, daß der für die Unterdrückung des Herzkammerflatterns optimale Bereich des Kondensatorentladungsstromes von 0,3 bis 4 ms geht. Schätzungseerte für Energie, Strom und Ladung, wie zur Bekämpfung des Herzkammerflatterns bei großen Tieren erforderlich sind, werden dargeboten.

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