Cardioversion, like cardiac defibrillation, is a method of transforming an arrhythmia into a sinus rhythm by means of an electric shock to the heart, and both have the same mechanism of action. A defibrillator with synchronized discharge is an electric cardioverter, but it is still customarily called a defibrillator.
The difference between resuscitation and defibrillation is that
1, the indications for treatment are different resuscitation is mainly used to treat tachyarrhythmias. Defibrillation is only used for the treatment of ventricular fibrillation and flutter.
2. The discharge mode is different. The resuscitation is triggered by the patient’s ECG R-wave, and the discharge is triggered only during the absolute non-response period of the cardiac cycle to avoid inducing ventricular fibrillation, while defibrillation is a random non-synchronous discharge mode.
The electrical energy required for resuscitation is less than that required for defibrillation.
I. Indications
(A) Atrial fibrillation
Atrial fibrillation is the most common type of arrhythmia in which synchronous DC electrical resuscitation is used. The immediate success rate of electrical resuscitation is 70% to 96%. Because the etiology of atrial fibrillation varies, the duration of the disease varies, and the response to drugs varies greatly, the choice of electrical resuscitation should be weighed in many ways.
There are two main categories of indications for atrial fibrillation: chronic atrial fibrillation with fast ventricular rate and obvious symptoms, or atrial fibrillation causing heart failure, and digitalis cannot control the ventricular rate; the other category of indications is atrial fibrillation that occurred recently after cardiac surgery, or atrial fibrillation that occurred within six months.
1, history of atrial fibrillation <1 year, previous sinus heart rate is not less than 60 times/min;
2, heart failure or angina worsening and not easily controlled after atrial fibrillation
3, atrial fibrillation with a fast ventricular rate and poor drug therapy.
4, atrial fibrillation persists even though the primary disease has been controlled, such as hyperthyroidism.
5.Atrial fibrillation does not disappear more than 3~6 months after valve replacement or repair for wind heart disease, or more than 2~3 months after repair for precordial disease. 6.Atrial fibrillation associated with pre-excitation syndrome.
(B) Atrial flutter
Atrial flutter is a rapid arrhythmia that is difficult to control by drugs. When atrial flutter is transmitted downward in a 1:1 ratio, it can lead to rapid hemodynamic deterioration and even life-threatening due to excessive ventricular rate. Electrical cardioversion is advocated as the first choice.
(iii) Ventricular tachycardia with hemodynamic instability that is ineffective with drug therapy
(D) supraventricular tachycardia most of the supraventricular tachycardia does not require the first choice of electrical resuscitation, should be preferred according to the specific circumstances of the excitation of the vagus nerve method or drug termination method, only a very few due to prolonged heart failure or signs of shock can choose electrical resuscitation.
Second, contraindications
1, with high or third degree atrioventricular block and consideration of pathological sinus node syndrome.
2, atrial fibrillation with digitalis toxicity, or atrial fibrillation caused by digitalis toxicity.
3, extremely poor cardiac function, with a cardiothoracic ratio > 55%, advanced age and long medical history, and little chance of resuscitation
4, severe water and electrolyte disturbances, especially in patients with hypokalemia.
5, those with uncontrolled infection and rheumatic activity.
6, those who cannot tolerate relapse prevention drugs such as amiodarone, propafenone, etc.
Complications of electrical resuscitation are often related to the amount of electricity used. The main ones are arrhythmia, myocardial injury, hypotension, acute pulmonary edema, pulmonary embolism and embolism of body circulation, skin burns, etc.
Third, complications
1.All kinds of cardiac arrhythmias, including cardiac arrest.
2.Decrease in blood pressure (hypotension), fever, and increase in serum cardiac enzymes.
3, peripheral arterial embolism, including cerebral embolism, mesenteric artery embolism, lower limb artery embolism, etc.
4.Pulmonary edema (occasional).
5.Local skin erythema and pain.
Fourth, the use of methods and precautions
1.Preparation of drugs before electric resuscitation ①Anti-arrhythmic drugs should be given a few days before electric resuscitation to prevent the recurrence of atrial fibrillation after resuscitation and to improve the success rate of electric resuscitation and reduce the electrical energy required. ②Generally, digitalis should be used to control the ventricular rate and improve cardiac function. If the patient is taking digitalis drugs, they should be stopped 1-2 d before resuscitation; ③Anticoagulation therapy to prevent embolic complications. The incidence of embolism is 1%-3%. Atrial fibrillation lasting no more than 2 d does not require anticoagulation, otherwise it should be treated with warfarin for 3 weeks before resuscitation and continued for 3-4 weeks after the rhythm is restored. For emergency resuscitation, heparin anticoagulation can be used.
2.Fast for more than 6h before resuscitation (except emergency resuscitation).
3.Prepare resuscitation equipment and drugs, prepare oxygen, open intravenous access, monitor ECG and blood pressure and pulse oximetry (SPO2).
4.The anesthetic principles of electric resuscitation are sedation, amnesia, elimination of fear of electric shock, supplemented by analgesia. The patient is gradually put to sleep, and the electric shock can be started when the patient does not respond to the call and the eyelash reflex disappears. During anesthesia, pay attention to keep the airway open to prevent hypoxia and keep SPO2 above 95%.
5.Select the synchronous discharge mode, electrode placement and charging and discharging process is the same as that of external chest defibrillation. The selection of electrical energy is mainly based on the type of arrhythmia and condition: atrial flutter 50~100 J, supraventricular tachycardia 100~150 J, ventricular tachycardia 100~200 J, atrial fibrillation 100~150 J. When repeated, the interval should be more than 3 min and should not be continued after 3~4 times.