We're very lucky, as this was the artery blocked. Notoriously known as a 'widow maker heart attack'.
A widow maker is a nickname used to describe a highly stenotic left main coronary artery or proximal left anterior descending coronary artery of the heart.
This term is used because if the artery gets abruptly and completely occluded it will cause a massive heart attack that will likely lead to a sudden death. The blockage that kills is made up of platelets streaming to the site of a ruptured cholesterol plaque. Even a small amount of plaque in this area can (for a variety of poorly understood reasons) rupture and cause death; bypassing chronic blockages or trying to open them up with angioplasty does not prevent heart attack but it can restore blood flow in case of a sudden blockage or heart attack. An example of the devastating results of a complete occlusion of the LAD (Left Anterior Descending) artery was the sudden death of former NBC News Washington Bureau Chief Tim Russert.
From the minute a widow maker hits, survival time ranges from minutes to several hours. Rapidly progressing symptoms should signal the need for immediate attention. Symptoms of initial onset may include nausea, shortness of breath, pain in the head, jaw, arms or chest, often of a novel but imprecise sensation which builds with irregular heart beat. Early symptoms may be mistaken for food poisoning, flu or general malaise until they intensify. A widow maker cannot kill instantaneously but induce cardiac arrest which may do so within 10 to 20 minutes of no circulation. A victim with no pulse or breath is still alive living off oxygen stored in the blood and may be able to be rescued if treatment is begun promptly within this window. .
Once again, all praise to my sister-in-law!