Unlike diseases such as tuberculosis or cancer, some disease processes are known to kill a human being within an hour of onset. Other than the obvious causes such as decapitation, massive bleeding or any other trauma-related injuries, these diseases tend to be cardiac or respiratory in origin.
A common example is coronary artery disease, where the blood vessel providing blood to an area of the heart becomes completely blocked by stenosis (narrowing, often by atherosclerosis) or a clot. This results in immediate ischaemia (lack of oxygen) to heart muscles, which causes cell death. This produces scar tissue which disrupts the electrical activity of the heart, which may lead to a condition called ventricular fibrillation where the heart beats in an uncontrolled, erratic manner. When in VF, the heart effectively becomes useless as it cannot coordinate proper pumping function. Blood circulation stops and the patient goes in to multiple organ failure (the brain goes first) within a very short time. Although it can kill within a short time, early identification and treatment may be able to prevent VF from occurring and save the patient’s life. If VF does occur, it is crucial to begin CPR or use a defibrillator if available.
VF can also occur in other situations. For example, there is a genetic condition called long QT syndrome which predisposes the patient to spontaneous arrhythmias (electrical abnormalities in the heart). Even becoming too excited can sometimes set off a VF in some LQTS patients, thus they require an implantable cardioverter-defibrillator (ICD) to shock their heart back in to normal rhythm every time they develop an arrhythmia.
Some other causes of sudden death include: aortic dissection (tearing of the aorta that may cause massive internal bleeding), pulmonary embolism (a clot obstructs blood flow in the lung, stopping circulation), commotio cordis (a blow to the heart at a certain moment in the heart rhythm triggers VF), ruptured brain aneurysm (ballooning of an artery in the brain), anaphylaxis (severe allergic reaction that cuts off airflow to the lungs) and poisoning (various mechanisms, mainly related to disrupting cellular function).
Death can strike swiftly, even from within your body.