There are many different types of arrhythmias, but the ones most frequently recorded in sudden cardiac arrest are ventricular tachycardia and ventricular fibrillation. Less common causes of dysrhythmias in cardiac arrest include pulseless electrical activity (PEA), bradyarrhythmias or asystole. Such rhythms are seen when there is prolonged cardiac arrest, progression of ventricular fibrillation, or efforts such as defibrillation executed to resuscitate the person. The rhythm changes also appear to have a correlation to the underlying cause of cardiac injury when present (ischemic vs. nonischemic causes). : 831 Sudden cardiac arrest can result from cardiac and non-cardiac causes including the following:

Cardiac causes
Coronary artery disease
Coronary artery disease (CAD), also known as ischemic heart disease, is responsible for 62 to 70 percent of all sudden cardiac deaths. CAD is a much less frequent cause of sudden cardiac death in people under the age of 40. Cases have shown that the most common finding at postmortem examination of sudden cardiac death is chronic high-grade stenosis of at least one segment of a major coronary artery, the arteries that supply the heart muscle with its blood supply. This stenosis is often the result of narrowing and hardening of the arteries following deposition of cholesterol plaques and inflammation over several years. This accumulation and remodeling of the coronary vessels along with other systemic blood vessels characterizes the progression of Atherosclerotic Cardiovascular Disease. When a stable plaque ruptures, it can block the flow of blood and oxygen through small arteries resulting in ischemic injury as a result.
Boomerang dysplasia is a lethal form of osteochondrodysplasia known for a characteristic congenital feature in which bones of the arms and legs are malformed into the shape of a boomerang. Death usually occurs in early infancy due to complications arising from overwhelming systemic bone malformations.Osteochondrodysplasias are skeletal disorders that cause malformations of both bone and cartilage. Presentation
Prenatal and neonatal diagnosis of boomerang dysplasia includes several prominent features found in other osteochondrodysplasias, though the "boomerang" malformation seen in the long bones is the delineating factor.Featured symptoms of boomerang dysplasia include: dwarfism (a lethal type of infantile dwarfism caused by systemic bone deformities), underossification (lack of bone formation) in the limbs, spine and ilium (pelvis); proliferation of multinucleated giant-cell chondrocytes (cells that produce cartilage and play a role in skeletal development - chondrocytes of this type are rarely found in osteochondrodysplasias), brachydactyly (shortened fingers) and micromelia (undersized, shortened bones).The characteristic "boomerang" malformation presents intermittently among random absences of long bones throughout the skeleton, in affected individuals. For example, one individual may have an absent radius and fibula, with the "boomerang" formation found in both ulnas and tibias. Another patient may present "boomerang" femora, and an absent tibia. Cause
Mutations in the Filamin B (FLNB) gene cause boomerang dysplasia. FLNB is a cytoplasmic protein that regulates intracellular communication and signalling by cross-linking the protein actin to allow direct communication between the cell membrane and cytoskeletal network, to control and guide proper skeletal development.