Who needs a defibrillator?
During resuscitation, only patients with ventricular fibrillation need defibrillation. Patients with asystole do not benefit from defibrillation. After a surviving cardiac arrest it is an important question whether a defibrillator should be implanted.
This is important because the probability of suffering another cardiac arrest is significantly increased in patients who have already suffered one. An implantable defibrillator (ICD) can detect life-threatening cardiac arrhythmias (ventricular fibrillation) and intervene. However, if a patient with an ICD suddenly develops asystole, the implanted pacemaker cannot help, as shock delivery is of no benefit in the absence of complete cardiac activity.
However, it is rather rare that primarily an asystole occurs. More often a ventricular fibrillation develops first. This can be stopped by a defibrillator. The indication for the implantation of an implantable defibrillator can be given in the following diseases: – condition after cardiovascular arrest – condition after tachycardic ventricular arrhythmia (cardiac arrhythmia with too fast ventricular action) – various forms of cardiomyopathy – coronary heart disease/condition after myocardial infarction – cardiac insufficiency with an ejection fraction of the heart (EF) below 35% – various cardiac arrhythmias (Long QT syndrome, Brugada syndrome)
Duration and prognosis of asystole
The prognosis for asystole is poor. An asystole lasting longer than a few seconds will result in unconsciousness. If it persists, the organs are no longer supplied with sufficient oxygen.
A longer lasting asystole always leads to death. An asystole that has lasted for minutes, but could be terminated by successful resuscitation, carries a high risk of permanent brain damage due to an oxygen deficiency in the brain. However, there are patients who can be successfully resuscitated in the case of an asystole and who do not retain any permanent damage.
The prognosis depends to a large extent on how quickly resuscitation measures are initiated. Therefore, lay resuscitation is of utmost importance. If resuscitation is only started when the emergency doctor arrives, the chances of successful resuscitation are much smaller than if sufficient lay resuscitation has been carried out beforehand.
The course of the disease is brilliant. Within minutes, an asystole leads to a severe undersupply of oxygen to the brain. An untreated asystole is fatal within minutes.
What’s the difference with V-fib?
Ventricular fibrillation is a life-threatening cardiac arrhythmia. In this case, the heart beats so fast due to an uncontrolled propagation of excitation in the heart that it can no longer pump adequately, but only flickers. If left untreated, ventricular fibrillation that is not self-limiting leads to death.
The two disorders are hardly distinguishable clinically. In both cases the patient is unconscious and not responsive. A pulse is not palpable.
The ECG shows a ventricular fibrillation due to uncoordinated and irregular flicker waves. In case of asystole the ECG shows a zero line. Both disturbances of the heart require immediate therapy (resuscitation), otherwise they usually end fatally.
While asystole must be treated with adrenaline and cardiac massage and ventilation, ventricular fibrillation requires defibrillation in addition to cardiac massage and ventilation to bring the heart back into the correct rhythm. In ventricular fibrillation, amiodarone is used in addition to adrenaline.