Among children rates of survival are 3 to 16% in North America. For in hospital cardiac arrest survival to discharge is around 22%. Those who survive to Return-of-Spontaneous-Circulation (ROSC) and hospital admission frequently present with Post-Cardiac Arrest Syndrome which usually presents with neurological injury that can range from mild memory problems to coma.Hypoxic ischemic brain injury is the most detrimental outcome for people suffering a cardiac arrest. Poor neurological outcomes following cardiac arrest are much more prevalent in countries that do not use withdrawal of life support (~50%) as compared to those that do (less than 10%). Most improvements in cognition occur during the first three months following cardiac arrest, with some individuals reporting improvement up to one-year post cardiac arrest. 50 – 70% of cardiac arrest survivors report fatigue as a symptom, making fatigue the most prevalent patient-reported symptom.Prognosis is typically assessed 72 hours or more after cardiac arrest. Rates of survival are better in those who someone saw collapse, got bystander CPR, or had either ventricular tachycardia or ventricular fibrillation when assessed. Survival among those with Vfib or Vtach is 15 to 23%. Women are more likely to survive cardiac arrest and leave hospital than men.A 1997 review found rates of survival to discharge of 14% although different studies varied from 0 to 28%. In those over the age of 70 who have a cardiac arrest while in hospital, survival to hospital discharge is less than 20%.
This is most commonly the result of longstanding high blood pressure, or hypertension, which has caused a maladaptive change to the wall of the main pumping chamber of the heart, the left ventricle. Increased blood pressure means that the heart must pump even harder to adequately circulate blood throughout the body. If the heart does this for a prolonged period of time due to uncontrolled hypertension, the left ventricle can hypertrophy (grow larger) in a way that decreases the effectiveness of the heart. Left ventricular hypertrophy can be demonstrated on echocardiogram and electrocardiogram (EKG).A 1999 review of sudden cardiac deaths in the United States found that structural heart diseases accounted for over 30% of sudden cardiac arrests for those under 30 years. A study of military recruits age 18-35 found that this accounted for over 40% of sudden cardiac deaths.Congestive heart failure increases the risk of sudden cardiac death fivefold.Structural abnormalities of the cardiac conduction system (notably the Atrioventricular Node and His-Purkinje system) may predispose an individual to arrhythmias with risk of progressing to sudden cardiac arrest, albeit this risk remains low. Many of these conduction blocks can be treated with internal cardiac defibrillators for those determined to be at high risk due to severity of fibrosis or severe electrophysiologic disturbances. : 833

Inherited arrhythmia syndromes
Arrhythmias that are not due to structural heart disease account for 5 to 10% of sudden cardiac arrests. These are frequently caused by genetic disorders that lead to abnormal heart rhythms.