I’ve always heard/been told to be careful while shoveling snow, that you’re more likely to have a heart attack. Why would I be more likely then as opposed to exerting myself during normal temperatures?
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Current med student here, and we literally covered this exact subject in this morning’s lecture (going to med school in Wisconsin so it’s pretty relevant here).
A little bit of necessary background: plaques build up in arteries over the years, which reduce the effective size of the inside of the artery and thus reduce blood flow. When this happens in the arteries that supply blood to the heart, it can cause pain (called angina) when oxygen demand in the heart increases, usually due to increased physical activity. In more severe cases, the blood flow to the heart can be reduced enough to actually kill part of the heart muscle when oxygen demand increases, this is one type of heart attack (NSTEMI, this part isn’t ELI5-appropriate I’ve just provided it so you can look it up if you want to). Another consequence of the plaques in the arteries is the formation of blood clots on them called thrombi. These thrombi cause even further blockage of the artery and reduce blood flow even more. The most dangerous part about a thrombus, though, is that it can break off and travel to a smaller artery where it can cause complete blockage of that artery. This process is called thromboebolism. If a clot breaks off and travels into one of the arteries that supply the heart, it can completely cut off blood supply to the part of the heart that is fed by that artery. This is another type of heart attack that is even more serious than the one mentioned above. Probably the worst-case scenario is if it blocks the left descending artery, which supplied the strongest and hardest working muscle in the heart, the left ventricle. This leads to the worst type of heart attack (STEMI, again, not ELI5-appropriate), and when it happens in this part of the heart it is nicknamed “the widowmaker” because it is so commonly fatal.
As to why these events commonly happen when people are shoveling snow, that’s mostly due to the fact that it can be pretty strenuous physical work and is often the first significant physical activity that people have had in several months if not longer. This leads to the heart working much harder than it has in a long time, meaning it requires more oxygen than it has in a long time and potentially more oxygen than the arteries are now capable of delivering. It also means an increased chance of a thrombus that may have formed elsewhere in the body breaking loose and potentially blocking one of the arteries to the heart.
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