The Heart 3.3 Sudden Cardiac Arrest
Cardiac Arrest is the sudden and often unexpected stoppage of effective heart action leading the coordinated heart muscle contractions to cease or the individual muscle fibres to twitch rapidly and irregularly.
Normal Sinus Rythm - Impulses originate at the SA Node at normal rate
The most common underlying reason for patients to die suddenly from cardiac arrest is coronary heart disease. Most cardiac arrests that lead to sudden death occur when the electrical impulses in the diseased heart become rapid (ventricular tachycardia, VT) or chaotic / quivering (ventricular fibrillation, VF) or both. This irregular heart rhythm causes the heart to suddenly stop beating.
Ventricular Tachycardia - Impulses originate at the ventricular pacemaker
Ventricular Fibrillation - Chaotic ventricular depolarisation
Some cardiac arrests are due to extreme slowing of the heart (bradycardia). Other factors besides heart disease and heart attack can cause cardiac arrest. They include respiratory arrest, electrocution, drowning, choking and trauma. Cardiac arrest can also occur without any known cause.
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