Prognosis

The outcome of sudden cardiac arrest is generally poor; while the application of algorithms for the treatment of sudden cardiac arrest has evolved, and the rate of sudden cardiac arrest is decreasing, the rate of successful recovery of a perfusing rhythm is still low. According to the US Cardiac Arrest Registry to Enhance Survival (CARES), survival to hospital admission after emergency medical services-treated non-traumatic out-of-hospital cardiac arrest (OHCA) in 2022 was 24.9% for all presentations, with higher survival rates in public places (36.9%) and lower survival rates in homes/residences (23.5%) and nursing homes (14.4%). Only 9.3% of patients with OHCA survive until hospital discharge.[2]​ The mean global survival rate of patients with OHCA is 7.7% at 1 year after hospital discharge, with variations worldwide.[115]

Early provision of CPR, including compression-only CPR, by bystanders during OHCA increases the rate of survival.[77][78] Other factors associated with a better prognosis include witnessed arrest, arrest during daytime hours, and initial shockable rhythm.[116]

Factors associated with a worse prognosis include male sex, aged >60 years, active malignancy, and chronic kidney disease.[116] Patients with ventricular tachycardia or ventricular fibrillation at diagnosis have the greatest rate of survival, followed by those who are found in pulseless electrical activity, and lastly patients found in asystole.

The most common mechanism of death after successful resuscitation from cardiac arrest is withdrawal of life-sustaining treatment on the basis of perceived poor neurological prognosis due to underlying hypoxic-ischaemic brain injury. Among cardiac arrest survivors, about half remain comatose 72 hours following return of spontaneous circulation (ROSC).[117]​ Neuroprognostication is an important component of the care pathway for these patients, but is complex, challenging, and often guided by limited evidence. Guidelines advise that definitive neuroprognostication should generally not occur before 72 hours after ROSC and should be performed in the absence of sedation or other confounders that may delay awakening (e.g., seizures, hypothermia, sepsis, renal failure, delirium, and hepatic encephalopathy).[117][118]​​ It should be multimodal, with consideration of the complete clinical picture (taking into account factors that impact overall prognosis, such as older age, poor baseline level of functioning, or pre-existing illness associated with limited life-expectancy), and never based on a single variable. Modalities include neurological examination, electroencephalogram (EEG), somatosensory evoked potentials (SSEPs), brain imaging (computed tomography and magnetic resonance imaging), and/or biomarkers (e.g., neuron specific enolase [NSE]) where available.[117][118]​​ The following findings on neurological examination portend death or a poor neurological outcome: at 24 hours - loss of corneal reflex, lack of motor response, lack of withdrawal to pain, and loss of pupillary response; and at 72 hours - lack of motor response.[119]​ When functional recovery does occur, the time course is highly variable.[117]

Among patients admitted to hospital after OHCA, the survival rate to discharge is approximately 50% to 60%.[120]​ Those who do survive to hospital discharge often have neurological, pulmonary, cardiac, hepatic, renal, or musculoskeletal complications. A survey of survivors of OHCA in Denmark, however, found that long-term patient-reported health-related quality of life up to 20 years after their event was consistently high and comparable to that of the general population.[121]​ Most survivors are able to return home, with only a small percentage (1% to 10%) requiring admission to a long-term care facility.[95]​ Data on long-term survival beyond 12 months after OHCA are scarce, but one systematic review found that survival after 10 years in patients surviving the initial hospital stay was between 62% and 64%. Patients with a shockable initial rhythm had a lower risk of long-term mortality compared with those with a non-shockable rhythm (hazard ratio 0.30; 95% CI 0.23-0.39).[120]

In European countries where withdrawal of life-sustaining treatment (WLST) is routinely practiced, a good neurological outcome is seen in >90% of patients. In situations where WLST is not applied, however, severe hypoxic-ischaemic brain injury is substantially more common; an Italian study reported that more than 50% (n = 119) of survivors had a poor outcome 6 months post-event, with one third (n = 68) in a persistent vegetative state.[122][123] Among survivors with a good neurological outcome, many experience long-term cognitive, emotional, and physical problems, as well as fatigue.​[123] Approximately 40% to 50% have cognitive impairments due to hypoxic-ischaemic brain injury. These are mainly mild to moderate and tend to affect memory, attention, processing speed, and executive function. Most cognitive recovery occurs in the first 3 months after cardiac arrest.[95][123]​ Emotional problems are also common; anxiety is present in 15% to 30% of survivors at 3-6 months (and remains in 15% to 23% at 12 months), while depression affects 13% to 32% of patients at 3-6 months (decreasing to 5% to 15% at 12 months).[95]​ Symptoms of stress and post-traumatic stress are reported in 16% to 28% of survivors, and some patients develop behavioural problems, such as emotional lability or aggression.[95][123]​ Fatigue is reported in approximately 70% of survivors at 6 months, and 50% at one year. Physical problems include rib fractures, muscle weakness, and restricted mobility, and some patients may benefit from referral to a physiotherapist or occupational therapist.[95][124]​ Of those who were previously working, 63% to 85% are able to return to work, although some need to adapt their working hours or activities.[95]

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