| Asystole | |
|---|---|
| Other names | Cardiac flatline, asystolic arrest |
 | |
| A rhythm strip showing two beats of normal sinus rhythm followed by an atrial beat and asystole | |
| Pronunciation | |
| Specialty | Cardiology  |
Asystole (fromNew Latin, from Greeka- 'not, without' +systolē 'contraction'[1][2]) is the absence of ventricular contractions in the context of a lethalheart arrhythmia (in contrast to an induced asystole on a cooled patient on aheart-lung machine andgeneral anesthesia during surgery necessitating stopping the heart). Asystole is the most serious form ofcardiac arrest and is usually irreversible. Also referred to ascardiac flatline, asystole is the state of total cessation of electrical activity from theheart, which means no tissue contraction from the heart muscle and therefore no blood flow to the rest of the body.
Asystole should not be confused with very brief pauses below 3 seconds in the heart's electrical activity that can occur in certain less severe abnormal rhythms. Asystole is different from very fine occurrences ofventricular fibrillation, though both have a poor prognosis, and untreated fine VF will lead to asystole. Faulty wiring, disconnection of electrodes and leads, and power disruptions should be ruled out.
Asystolic patients (as opposed to those with a "shockable rhythm" such as coarse or fine ventricular fibrillation, or unstableventricular tachycardia that is not producing a pulse, which can potentially be treated withdefibrillation) usually present with a very poor prognosis. Asystole is found initially in only about 28% of cardiac arrest cases in hospitalized patients,[3] but only 15% of these survive, even with the benefit of anintensive care unit, with the rate being lower (6%) for those already prescribed drugs forhigh blood pressure.[4]
Asystole is treated bycardiopulmonary resuscitation (CPR) combined with an intravenousvasopressor such asepinephrine (adrenaline).[5] Sometimes an underlying reversible cause can be detected and treated (the so-called "Hs and Ts", an example of which ishypokalaemia). Several interventions previously recommended—such as defibrillation (known to be ineffective on asystole, but previously performed in case the rhythm was actually very fine ventricular fibrillation) and intravenousatropine—are no longer part of the routine protocols recommended by most major international bodies.[6] 1 mg of epinephrine is givenintravenously every 3-5 minutes for asystole.[7]
Survival rates in a cardiac arrest patient with asystole are much lower than a patient with a rhythm amenable to defibrillation; asystole is itself not a "shockable" rhythm. Even in those cases where an individual suffers a cardiac arrest with asystole and it is converted to a less severe shockable rhythm (ventricular fibrillation, or ventricular tachycardia), this does not necessarily improve the person's chances of survival to discharge from the hospital, though if the case was witnessed by a civilian, or better, a paramedic, who gave good CPR and cardiac drugs, this is an important confounding factor to be considered in certain select cases.[8] Out-of-hospital survival rates (even with emergency intervention) are less than 2 percent.[9]
Possible underlying causes, which may be treatable and reversible in certain cases, include theHs and Ts.[10][11][12]
While the heart is asystolic, there is no blood flow to the brain unlessCPR orinternal cardiac massage (when the chest is opened and the heart is manually compressed) is performed, and even then it is a small amount. After many emergency treatments have been applied but the heart is still unresponsive, it is time to consider pronouncing the patientdead. Even in the rare case that a rhythm reappears, if asystole has persisted for fifteen minutes or more, the brain will have been deprived of oxygen long enough to cause severehypoxicbrain damage, resulting inbrain death orpersistent vegetative state.[13]
