Sudden Cardiac Arrest Is Often Caused by Ventricular Fibrillation in Its Early Stages

When sudden cardiac arrest occurs, the most common underlying pathophysiological mechanism is a rapid ventricular arrhythmia, such as ventricular fibrillation (VF) or ventricular tachycardia (VT). These abnormal heart rhythms disrupt the heart's ability to pump blood effectively, leading to a sudden loss of cardiac function.

Other Potential Causes of Cardiac Arrest

While ventricular fibrillation is the most frequent cause, it's important to note that other rhythm disturbances can also lead to cardiac arrest. These include bradyarrhythmias (slow heart rhythms) and asystole (complete cessation of electrical activity in the heart). A less common cause is pulseless electrical activity (PEA), where the heart produces electrical signals but fails to generate a pulse.

Immediate Effects on the Brain and Body

During cardiac arrest, blood flow to the brain drops dramatically, often resulting in immediate loss of consciousness. This may be accompanied by localized or generalized seizures due to the brain's lack of oxygen.

Respiratory Response During Early Arrest

In the initial moments following cardiac arrest, there may still be a small amount of oxygenated blood in the brain. This can temporarily stimulate the respiratory center, causing irregular breathing patterns such as gasping or brief, spasmodic breaths. Eventually, all respiratory effort ceases.

Physical Signs of Cardiac Arrest

As oxygen levels drop, the skin may become pale or take on a bluish tint (cyanosis), and the pupils may begin to dilate. Additionally, because of the loss of autonomic control, urinary and fecal incontinence can occur due to relaxation of the sphincter muscles.