External Countershock Research Articles

Massive Inhalation of Desflurane due to Vaporizer Dysfunction

Massive Inhalation of Desflurane due to Vaporizer Dysfunction

Electrode pad size, transthoracic impedance and success of external ventricular defibrillation

Electrode pad size is an important determinant of transthoracic current flow during external countershock. Self-adhesive, dual function electrocardiogram/defibrillator pads were used to assess the effect of electrode pad size on defibrillation success with low energy (200 J) shocks. The study analyzed 123 cardiac arrests due to primary ventricular fibrillation (VF) in 105 patients (74 men, 31 women) ages 40 to 84 years (mean 64). Transthoracic impedance was measured before defibrillation using a low amplitude 30-kHz current passed through the chest by way of the electrocardigram/ defibrillator pads applied anteroanteriorly. Pad diameters were small ( 8 8 cm) in 26 cardiac arrests, intermediate ( 8 12 cm) in 63 arrests and large ( 12 12 cm) in 34 cardiac arrests. Transthoracic impedance decreased with increasing pad size (112 ± 17 vs 92 ± 22 vs 72 ± 14 Ω, respectively, p = 0.0001). Only the first episode of primary VF during a cardiac arrest was analyzed. A single shock of 200 J (delivered energy) was successful in 8 of 26 (31%) arrests using small pads, in 40 of 63 (63%) with intermediate pads and in 28 of 34 (82%) with large pads (p = 0.0003). A second 200-J shock increased the cumulative defibrillation rates to 12 of 26 (46%), 50 of 63 (79%) and 33 of 34 (97%), respectively (p < 0.0001). In primary VF, larger self-adhesive etectrocardiogram/defibrillator pads are associated with a lower transthoracic impedance and improved defibrillation success rates with low energy shocks.

Pulmonary Edema following Conversion of Tachyarrhythmia: A Case following Burst Atrial Pacing

Restoration of normal sinus rhythm is usually followed by improved hemodynamics. By contrast, pulmonary edema and cardiovascular collapse have been reported following successful electrical reversion of various tachyarrhythmias to normal sinus rhythm. The mechanism for this adverse reaction is not clear but has been thought to relate, at least in part, to electrical myocardial damage from the countershock. This report describes a patient in whom this complication occurred on two occasions, first following external countershock and subsequently following burst atrial pacing. Thus, conversion to sinus rhythm may be responsible for this phenomenon independent of the method of conversion.

Development of Electric Control of Cardiac Rhythm

Techniques for electric control of cardiac rhythm began with the demonstration of an action current preceding each myocardial contraction. Next came direct stimulation and countershock defibrillation with electrodes placed directly on the exposed heart. Later, external electric stimulation and external countershock with electrodes on the precordium permitted emergency resuscitation from ventricular standstill and fibrillation and provided a means for stopping rapid arrhythmias. Cardiac monitors permit the prompt recognition and identification of arrhythmias; they led to the widespread growth of coronary-care units. Cardiac pacing is now undergoing extensive development and application in many new directions.

Development of electric control of cardiac rhythm

Techniques for electric control of cardiac rhythm began with the demonstration of an action current preceding each myocardial contraction. Next came direct stimulation and countershock defibrillation with electrodes placed directly on the exposed heart. Later, external electric stimulation and external countershock with electrodes on the precordium permitted emergency resuscitation from ventricular standstill and fibrillation and provided a means for stopping rapid arrhythmias. Cardiac monitors permit the prompt recognition and identification of arrhythmias; they led to the widespread growth of coronary-care units. Cardiac pacing is now undergoing extensive development and application in many new directions.

Precordial thumping during cardiac resuscitation.

A forceful blow to the precordium has long been recommended as the first resuscitative measure following cardiac arrest. It has been shown sometimes to cause slowing of ventricular tachycardia. However, reports maintaining that cardiac standstill responded to chest thumping failed to establish the cardiocirculatory conditions at the time of treatment. This study evaluated the maneuver in resuscitating asphyxiated dogs with cardiac standstill, ventricular fibrillation, severe hypotension clinically resembling cardiac arrest, and post-resuscitation tachyarrhythmias. In animals with ventricular tachycardia, precordial thumping caused ventricular fibrillation as often as reversion to sinus rhythm. Used during severe hypotension it had no effect; nor did it precipitate cardiac asystole, ventricular fibrillation or ventricular tachycardia. No animal with cardiac standstill or ventricular fibrillation was benefited by thumping while artificial ventilation, external cardiac massage, intravenous epinephrine and external countershock restored 14 of 15 animals. It would appear that precordial thumping should be utilized in the management of ventricular tachycardia only when equipment for external defibrillation is immediately available. The measure should be deleted from the recommended treatment of cardiac arrest.

ELECTRICAL CONVERSION OF VENTRICUALAR TACHYCARDIA.

Termination of ventricular tachycardia using an external countershock was electively attempted in 21 episodes of ventricular tachycardia occurring in 12 patients. In all cases, myocardial depressant drugs had been tried unsuccessfully prior to attempted electrical conversion. The tachyardia was successfully converted in 20 of the 21 episodes. In six cases, an alternating-current (ac) discharge was used, with successful conversion five times. In 15 cases, a synchronized direct-current (dc) discharge was employed with 14 successful conversions. The only failure in both series occurred in the same patient, who could not be successfully converted with either ac or dc. Ventricular fibrillation was precipitated by the shock once in each group of patients, and was controlled by the application of further countershock. The use of an externally applied shock, either ac or dc, proved to be a safe and effective method of treating ventricular tachycardia when the use of conventional drugs was either unsuccessful or deemed hazardous.

Countershock conversion of digitalis-associated paroxysmal atrial tachycardia with block

The first successful conversion of paroxysmal atrial tachycardia (PAT) with block by means of external countershock is reported. The arrhythmia occurred while the patient was receiving digitalis and after the loss of potassium due to brisk diuresis and other factors, and digitalis intoxication appeared to be likely. The arrhythmia proved to be refractory to intravenous potassium and procaine amide carried to toxicity but was promptly converted to sinus rhythm with a single DC synchronized countershock. This method is suggested in the management of PAT with block when there is a dilemma whether this arrhythmia was caused by digitalis or whether further digitalis administration is indicated after conventional methods of treatment have proved to be ineffective.

Resistant Ventricular Tachycardia a Year After Surgical Correction of Fallot's Tetralogy, Treated by External Electrical Countershock

Resistant Ventricular Tachycardia a Year After Surgical Correction of Fallot's Tetralogy, Treated by External Electrical Countershock

Critical evaluation of indications for external electric countershock in the treatment of ventricular tachycardia

External electric countershock has been recently employed and recommended for the treatment of ventricular tachycardia and other serious arrhythmias, when drug therapy is ineffective and the patient's condition desperate or intolerable. Two cases of ventricular tachycardia are reported in which the use of external countershock was regarded as indicated. In one case, in which other drugs had failed and procaine amide was regarded as contraindicated because of periods of heart block, external countershock was considered urgently necessary because of a deteriorating clinical state. Nevertheless, the tachycardia disappeared spontaneously after withholding all drugs while the patient was carefully observed. In the second case in which drug therapy was considered ineffective after 5 gm. of procaine amide intravenously had caused a widening of the QRS to 0.18 second without conversion, a subsequent, much more rapid infusion of the same drug in a total dose of 1 gm. restored sinus rhythm. An analysis of the cases reported in the literature in which details are presented indicates that procaine amide had been given too slowly or too briefly to regard the drug as ineffective and the urgent need for electric countershock appears questionable. In view of the drastic nature of external electric countershock in the conscious patient and the need for an anesthetic, the requirement of this procedure many different times in some patients, the occurrence of ventricular fibrillation or standstill after counter-shock with the need for further defibrillation or external stimulation, the prompt recurrence of the ventricular tachycardia in some cases, and because of possible fatalities, the indications for such procedure must be most critically assayed in the light of our experience in the two reported cases.

A simple portable pneumatic pump for external cardiac massage

A portable pneumatic pump for external cardiac massage has been described. The apparatus is easy to operate, involving only three maneuvers, namely, opening the gas valve, connecting the hose to the gas source, and turning the rate regulator to the desired speed. A two-transistor rate circuit controls a small relay which energizes the solenoid of the valve. A small 30 volt battery powers the transistors while a larger lantern battery is used for the solenoid. The control circuit may be bypassed by means of a switching jack, and the solenoid valve controlled externally for synchronization of the R wave. The apparatus has maintained adequate circulation so that dogs in ventricular fibrillation for 30-minute periods were easily restored to good health by external countershock. Arterial pressures were recorded in 3 recently deceased persons. Further experimental and clinical studies are being conducted to elucidate those circulatory and respiratory factors which will make external cardiac massage most likely to succeed.

External countershock treatment of ventricular fibrillation and tachycardia A case report

External countershock treatment of ventricular fibrillation and tachycardia A case report

Termination of Refractory Tachycardia by External Countershock

External electric countershock has been used to terminate refractory supraventricular and ventricular tachycardia and atrial fibrillation in eight patients. General anesthesia is necessary when the patient is conscious. This technic is indicated when the patient's condition is desperate or intolerable and drug therapy is ineffective, too slow, or otherwise inadvisable.

Use of external electric countershock in the treatment of ventricular tachycardia.

ELECTRIC countershock applied to the closed chest has been successfully used to terminate ventricular fibrillation and prefibrillatory ventricular tachycardia. 1-3 Generally, this technique has been employed as an emergency measure in the unconscious patient with Adams-Stokes disease in the absence of other therapeutic alternatives. No reports exist on the deliberate use of external countershock as an elective procedure to control episodes of ventricular tachycardia in the conscious patient. The following experiences illustrate its effectiveness in the treatment of ventricular tachycardia resistant to drug therapy. Report of a Case A 59-year-old man entered the Peter Bent Brigham Hospital Dec. 1, 1960, with the chief complaint of palpitations, shortness of breath, and profuse sweating of 24-hours duration. In 1949 he sustained an acute myocardial infarction. Six years later he first noted the onset of paroxysmal rapid heart action. In September, 1960, the attacks increased in frequency, often lasting many hours, and