Cardiac arrest is a critical, life-threatening medical emergency characterized by the sudden and unexpected cessation of cardiac function, respiration, and consciousness. This abrupt failure is typically triggered by a severe electrical disturbance in the heart’s rhythm most commonly ventricular fibrillation or ventricular tachycardia that disrupts its ability to effectively pump blood. As a result, blood circulation to the brain and other essential organs halts almost instantly, leading to rapid oxygen deprivation. Without immediate intervention, such as cardiopulmonary resuscitation (CPR) or defibrillation, cardiac arrest can lead to irreversible brain damage or death within minutes. During cardiac arrest, individuals usually lose consciousness and do not respond. The symptoms appear abruptly and without any prior signs, which is why it’s often referred to as sudden cardiac arrest. In recent years, the rate of sudden cardiac arrest occurring outside of a hospital setting is increasing rapidly.
Sudden cardiac arrest can strike individuals regardless of whether they have a known history of heart disease. However, the presence of certain cardiovascular conditions such as a previous heart attack, structural heart abnormalities, or arrhythmias can greatly elevate a person’s risk of experiencing this life-threatening event.
The leading cause of sudden cardiac arrest is an abnormal heart rhythm known as ventricular fibrillation. This condition involves disorganized, rapid electrical impulses that cause the ventricles of the heart’s lower chambers to quiver ineffectively rather than contract and pump blood. Certain underlying heart disorders can increase the risk of developing this life-threatening arrhythmia.
However, sudden cardiac arrest may also occur in individuals with no prior history of heart disease. Cardiac conditions associated with an elevated risk of sudden cardiac arrest include:
 Coronary artery disease (CAD): Sudden cardiac arrest can result from coronary artery disease, a condition in which the heart’s major blood vessels become narrowed or blocked due to the buildup of cholesterol, fatty deposits, and other substances, a process known as atherosclerosis. This buildup restricts the flow of oxygen-rich blood to the heart muscle, potentially leading to areas of the heart becoming electrically unstable. Reduced blood supply can impair the heart’s ability to function properly and increase the risk of dangerous arrhythmias, such as ventricular fibrillation, which can ultimately trigger sudden cardiac arrest.
 Heart Attack (Myocardial Infarction): A heart attack, most commonly caused by a severe blockage in the coronary arteries due to advanced coronary artery disease, can serve as a major trigger for sudden cardiac arrest. When blood flow to a portion of the heart muscle is abruptly cut off, the affected tissue becomes damaged or dies. This sudden injury to the heart can disrupt its electrical stability and lead to life-threatening arrhythmias such as ventricular fibrillation, a chaotic rhythm that prevents the heart from pumping effectively.
In addition to the immediate threat, a heart attack can leave behind scar tissue in the heart muscle. This scarred area does not conduct electrical impulses normally, which can interfere with the heart’s rhythm and increase the likelihood of future arrhythmias. Over time, these irregular electrical patterns may elevate the risk of sudden cardiac arrest, even after recovery from the initial heart attack
Enlarged Heart (Cardiomyopathy): Cardiomyopathy is a condition characterized by structural abnormalities in the heart muscle, most commonly involving the enlargement, thickening, or weakening of its walls. In many cases, the heart muscle stretches and thins, causing the chambers especially the ventricles to become dilated. Alternatively, the muscle may become abnormally thickened, as seen in hypertrophic cardiomyopathy. As the heart enlarges or its walls thicken, it becomes less efficient at pumping blood and maintaining a normal rhythm. These changes can disrupt the electrical pathways within the heart, leading to irregular heartbeats (arrhythmias), which may significantly increase the risk of sudden cardiac arrest.
Heart valve disease: refers to any condition that affects the proper functioning of one or more of the heart’s valves. These valves may either become narrowed (a condition known as stenosis) or may not close properly, leading to leakage (referred to as regurgitation or insufficiency). When the valves fail to open or close as they should, the heart must work harder to pump blood effectively. Over time, this added strain can cause the heart muscle to become abnormally thickened or stretched, especially in the chambers responsible for pumping blood. As the heart’s structure changes and becomes weakened, the likelihood of developing arrhythmias or irregular heart rhythms increases significantly, potentially leading to further complications if not managed appropriately.
Congenital heart defect: is a structural abnormality of the heart that is present from birth. These defects can vary widely in type and severity, affecting how blood flows through the heart and to the rest of the body. In children and adolescents, sudden cardiac arrest is often linked to an underlying congenital heart condition that may or may not have been previously diagnosed. Even when such defects are identified early and corrected through surgical intervention, individuals may still face long-term cardiac risks. Adults who underwent surgical repair for a congenital heart defect during childhood remain at an elevated risk of sudden cardiac arrest later in life, due to lingering electrical or structural abnormalities in the heart. Ongoing monitoring and specialized cardiac care are often necessary to manage this risk effectively.
However, there are factors that can increase the risk of cardiac arrest in people without prior history of health disease. These risk factors associated with heart disease also significantly heighten the likelihood of sudden cardiac arrest.
These includes:
 Smoking: Smoking significantly increases the risk of sudden cardiac arrest by damaging the cardiovascular system in multiple ways. The chemicals in tobacco smoke contribute to the buildup of plaque in the arteries (atherosclerosis), which restricts blood flow and can lead to coronary artery disease, a major trigger for cardiac arrest.
Nicotine, a key component of tobacco, stimulates the release of adrenaline, which increases heart rate, raises blood pressure, and can provoke abnormal heart rhythms (arrhythmias). These arrhythmias, especially in individuals with underlying heart conditions, can escalate into ventricular fibrillation, the most common cause of sudden cardiac arrest.
Additionally, smoking reduces oxygen delivery to the heart and other tissues, promotes inflammation, and increases the likelihood of blood clot formations all of which put extra strain on the heart and raise the chances of a sudden cardiac event.
Diabetes: Diabetes mellitus, particularly type 2 diabetes, is a major independent risk factor for sudden cardiac arrest (SCA) due to its multifaceted impact on cardiovascular health. Chronic hyperglycemia (elevated blood glucose levels) leads to both macrovascular and microvascular damage, significantly accelerating atherosclerosis the buildup of plaque within arterial walls which increases the risk of coronary artery disease (CAD). Since CAD is the most common underlying cause of SCA, this creates a direct link between diabetes and the likelihood of a fatal arrhythmic event.
Moreover, diabetes contributes to autonomic neuropathy, a condition in which the autonomic nerves controlling heart rate and blood pressure become damaged. This disruption can impair normal cardiac regulation, increasing the risk of silent myocardial ischemia and making the heart more vulnerable to life-threatening arrhythmias such as ventricular tachycardia or ventricular fibrillation.In addition, insulin resistance and chronic inflammation seen in diabetes promote electrical and structural remodeling of the myocardium, including left ventricular hypertrophy and myocardial fibrosis.
These changes impair the heart’s electrical stability, making arrhythmic events more likely. Diabetics are also more likely to have comorbid conditions such as hypertension, obesity, and dyslipidemia, all of which further compound cardiovascular risk and contribute to the progression of structural heart disease another key risk factor for SCA.
Psychological Stress: Chronic psychological stress is increasingly recognized as a significant, though often underestimated, contributor to cardiovascular morbidity and mortality including sudden cardiac arrest (SCA). The pathophysiological link between stress and SCA is multifactorial, involving neuroendocrine, autonomic, and inflammatory pathways.
Under stress, the hypothalamic-pituitary-adrenal (HPA) axis is activated, resulting in elevated levels of cortisol and catecholamines (e.g., adrenaline and noradrenaline). These stress hormones increase heart rate, blood pressure, and myocardial oxygen demand, placing additional strain on the cardiovascular system. In individuals with underlying coronary artery disease or structural heart abnormalities, this heightened demand can precipitate myocardial ischemia or trigger malignant ventricular arrhythmias, both of which can lead to sudden cardiac arrest.
Obesity:
Obesity is a well established, independent risk factor for sudden cardiac arrest due to its profound and multifactorial effects on cardiovascular structure, function, and electrophysiology. Its impact extends across mechanical, metabolic, inflammatory, and electrical domains of cardiac health.
Obesity leads to increased cardiac workload due to higher blood volume and cardiac output needed to meet the metabolic demands of excess adipose tissue. Over time, this chronic volume overload contributes to left ventricular hypertrophy (LVH) and left atrial enlargement, both of which are known to create a substrate for electrical instability and malignant ventricular arrhythmias.
Obesity is also associated with diastolic dysfunction and, in some cases, the development of heart failure with preserved ejection fraction (HFpEF) a condition that increases the risk of arrhythmias and sudden cardiac death, even in the absence of overt coronary artery disease.
High blood cholesterol:
High blood cholesterol can increase the risk of cardiac arrest primarily by contributing to the development of atherosclerosis, a condition where cholesterol and other substances build up on the walls of the arteries. Sometimes, a plaque can rupture, causing a blood clot to form. If this completely blocks a coronary artery, it can stop blood flow to the heart, triggering a sudden cardiac arrest a condition where the heart stops beating effectively.
Being male:
Being male increases the risk of cardiac arrest due to a combination of hormonal, biological, and behavioral factors. One key reason is the difference in sex hormones: men have higher levels of testosterone, while women (especially before menopause) have higher levels of estrogen, which provides protective cardiovascular effects by improving cholesterol profiles and maintaining healthy blood vessels. Without this protection, men are more susceptible to developing heart disease earlier in life. Men also tend to experience coronary artery disease, the leading cause of cardiac arrest about 10 years earlier than women.
Additionally, lifestyle and health related risk factors such as smoking, high blood pressure, poor diet, and higher levels of LDL cholesterol are more common or severe in men at younger ages. Structurally and electrically, male hearts may be more prone to certain arrhythmias, such as ventricular fibrillation, which is a primary cause of sudden cardiac arrest. Moreover, after heart damage, men’s hearts often undergo more scarring and remodeling, increasing the likelihood of electrical disturbances. Statistically, men are two to three times more likely to experience sudden cardiac arrest than women, making male sex a significant non-modifiable risk factor for this life-threatening condition.
Prevention
You can lower your risk of cardiac arrest and other heart-related conditions by making healthy lifestyle changes, such as:
Following a heart-friendly diet
Maintaining a healthy weight
Staying physically active
Avoiding smoking and drug use
Limiting alcohol consumption
