Influence of ventilation phase on transthoracic impedance and defibrillation effectiveness.

The influence of the phase of ventilation on the transthoracic impedance and defibrillation success was studied in 6 mongrel dogs. Ventricular fibrillation was induced by a transvenous bipolar catheter electrode. Defibrillation was attempted after 1 min of ventricular fibrillation.

Influence of time and therapy on ventricular defibrillation in dogs.

Factors that may influence energy requirements for ventricular defibrillation include the duration of fibrillation and the mode of resuscitation. The present study assesses the effect of these influences on the energy needed for defibrillation. Dogs were anesthetized, and arterial blood pressure and Lead II of the ECG were continuously recorded.

Preoperative evaluation of patients with electrocardiographic conduction defects.

Prophylactic pacemakers should be recommended for all preoperative patients with second- and third-degree heart block, regardless of whether the block is in the AV node or the trifascicular conduction system. Symptomatic patients with potential for trifascicular block should also have a transvenous pacemaker. Those without symptoms should be monitored during anesthesia and the postoperative recovery period.

Comparison of myocardial damage from defibrillator discharges at various dosages.

To study the difference in myocardial damage produced by the same defibrillation energy delivered at frequent, low-energy discharges vs infrequent, high-energy discharges, experiments were performed on 48 dogs. In Part I, a total of 3000 Wsec energy was delivered; in Part II, a total of 600 Wsec was delivered; and in Parts III and IV, a total of 1800 Wsec was delivered. In half the dogs, the energy was delivered in three shocks within 135 sec.

1-year followup of cardiac status after adriamycin therapy.

To study the natural history of the alterations in cardiac function produced by Adriamycin therapy, serial M-mode echocardiograms, electrocardiograms, and systolic time intervals were obtained in 15 patients prior to Adriamycin therapy and at 3-month intervals during and 1 year after cessation of therapy. The echocardiographic E-point septal separation increased from a median 0 dose value of 0.40 cm to 0.

Electrocardiographic axis deviation in Navajo and Apache indians.

It has been our clinical impression that the range of the mean frontal-plane electrocardiographic QRS axis was greater than might have been anticipated in healthy Navajo and Apache Indians. To determine whether this clinical impression was correct, electrocardiograms were obtained from 146 Navajo, 144 Apache, and 159 non-Navajo non-Apache schoolchildren with normal findings on cardiovascular examinations. A mean frontal-plane QRS axis between -1 degrees and -90 degrees was present in 19 percent of the Navajo, 12 percent of the Apache, and 2 percent of the control schoolchildren.

Transvenous catheter defibrillation: comparison of a half-sinusoidal and trapezoidal waveform.

This study compares transvenous electrode catheters' defibrillation effectiveness when using the trapezoidal waveform and when using the damped half-sinusoidal waveform, at comparable energy levels. Five greyhounds were used in some 272 fibrillation/defibrillation trials. Neither total energy, peak current, nor peak voltage could be absolutely correlated with percent effectiveness for transvenous defibrillation.

Electrode system for permanent implantable defibrillators: transvenous catheter and subcutaneous plate electrodes.

The permanently implanted automatic defibrillator offers an alternative treatment for heart patients with high risk of ventricular fibrillation, who cannot be safely treated by surgery or drugs. Because of size and energy requirements, permanently implanted automatic defibrillators are not presently practical for many of these patinets, and sudden death from ventricular fibrillation remains a majof health problem. This study, which determines the optimal electrode configuration of the transvenous catheter when used in conjunction with a subcutaneous plate or disk electrode for transvenous ventricular defibrillation, attempts one of many changes needed to improve the defibrillator's efficiency so that it will be a viable alternative treatment for delicate heart patients.

Impedance to transthoracic direct current discharge: a model for testing interface material.

An in vitro method for screening the relative impedance of gels has been developed. A nonconductive chamber was built with 1-cm-diameter electrodes placed 1 cm apart. This chamber is filled with electrode gel to be tested.

Effectiveness of direct current defibrillation: role of paddle electrode size.

Myocardial necrosis from repeated direct current defibrillation discharges is less when the same stored energy is delivered by paddle electrodes that are larger than those presently available on the majority of commercial defibrillators. The present study was undertaken to determine if the larger 12.8 cm.