Heart attack explained: the mechanisms and risk factors
KD Dr. med. Simon Andreas Müggler
September 29, 2023
10 min
Dr Simon Andreas Müggler, how does a heart attack occur?
The heart beats around 100,000 times a day, transporting over 7,000 litres of blood. In order for our heart to beat and supply the body with oxygen-rich blood and nutrients, it needs sufficient oxygen-rich blood itself. The blood is distributed in the heart muscle via three large arteries (coronary arteries). An important prerequisite for normal blood flow is healthy, unobstructed blood vessels. Various conditions, most frequently arteriosclerosis, lead to damage to the coronary arteries. In arteriosclerosis, the vessel walls thicken due to the accumulation of cholesterol and subsequent calcification processes, resulting in the formation of so-called arteriosclerosis plaques. If such a plaque "breaks open", the blood coagulates at this point and suddenly closes the vessel more or less completely, resulting in a heart attack (myocardial infarction).
Can you tell us more about how a heart attack affects the heart muscle and why it can be life-threatening?
A myocardial infarction in its typical form is an acute, life-threatening event resulting from a sudden disruption of blood flow in a coronary artery. This circulatory disorder leads to an acute lack of oxygen in the heart muscle cells that are dependent on the affected coronary artery. If the circulatory disorder is not corrected quickly, the heart muscle cells are irreversibly damaged and die.
A heart attack is particularly life-threatening because it can lead to dangerous cardiac arrhythmias such as ventricular fibrillation (even in the case of minor heart attacks) or mechanical complications such as a tear in the heart muscle. In addition to arteriosclerosis, there are rarer causes of a heart attack, such as spasms of the coronary arteries (coronary spasm), a tear in the vessel wall of a coronary artery (coronary dissection) or the spread of a blood clot (embolism) or the colonisation of bacteria in a coronary artery.
How do people who are about to have a heart attack feel? What are the symptoms?
There are people for whom a heart attack occurs without warning and is therefore the first symptom of heart disease. However, people often complain of symptoms such as angina pectoris during physical or emotional stress or at night before a heart attack. Typical angina pectoris manifests itself as a flat, dull, burning or oppressive "tight feeling in the chest", as if a "weight were lying over the chest" or a "fist is pressing on the chest". The symptoms then disappear completely within a few minutes after stopping the exercise; taking nitroglycerin medication can support this. Angina pectoris can remain stable for a long time, but can also occur more frequently, for longer periods and with less exertion, in which case medical clarification is required immediately at the latest.
The main symptoms of an acute heart attack are angina pectoris, which is usually more pronounced and does not disappear within minutes, and can radiate to the arms (left and right), neck, jaw, back and upper abdomen. It is often accompanied by symptoms such as nausea, vomiting, sweating, dizziness and shortness of breath.
A minority of all heart attacks present with only mild or even no symptoms at all ("silent" heart attack); this form is often only detected later by chance on an ECG ("cardiac waveform") or by means of a cardiac ultrasound.
What about heart attacks in women? What's different from men?
In fact, women, like older people, are more likely to show less typical symptoms than men or younger people. These atypical symptoms include, for example, acute shortness of breath, general weakness and fatigue or stomach complaints. Several studies have shown that women with acute myocardial infarction are treated differently to men. For example, women are less likely to undergo prompt cardiac catheterisation, although there are no recommendations to treat heart attacks differently in women and men. People with diabetes mellitus ("diabetes") are also more likely to have a silent heart attack due to chronic nerve damage, as the sensation of pain is reduced.
Who is particularly at risk and what are the risk factors for a heart attack?
The risk of suffering a heart attack is made up of one third of controllable risk factors (see below), one third of genetics (family history) and one third of chance. As only one third of the risk can therefore be influenced, strict control of these cardiovascular risk factors is fundamental in order to reduce the risk of heart attack, as well as the risk of stroke.
The most important risk factors include arterial hypertension ("high blood pressure"), elevated blood lipid levels (especially cholesterol, "dyslipidaemia"), smoking (tobacco consumption), obesity and diabetes mellitus. Factors that cannot be influenced include genetics, male gender and age. People with the above-mentioned risk factors are therefore particularly at risk of suffering a heart attack.
What measures help to prevent heart attacks?
As just mentioned, strict control of cardiovascular risk factors is crucial. High blood pressure often cannot be reduced sufficiently without medication. Elevated blood lipid levels (cholesterol) can unfortunately only be reduced by around 10 to 15% through pure dietary optimisation ("Mediterranean diet"); here too, medication is often necessary in order to achieve the individual target values for LDL cholesterol, the so-called "bad" cholesterol. Incidentally, the effectiveness of lowering cholesterol with medication in terms of improving survival and reducing heart attacks, for example, has been proven by countless studies and registry data, including those independent of pharmaceutical companies.
It is also very important to stop smoking. Smokers live on average 11 years (women) or 12 years (men) less than non-smokers, and even after many years of tobacco consumption, quitting smoking still improves the prognosis. Unfortunately, simply reducing tobacco consumption does not achieve much. For example, people who consume just one cigarette a day still have a 40 to 50 per cent increased risk of suffering a heart attack or stroke (compared to consuming 20 cigarettes a day).
Good treatment of diabetes mellitus is just as important as weight reduction in overweight people. Being overweight also indirectly increases the cardiovascular risk by promoting other risk factors such as high blood pressure, diabetes mellitus and high cholesterol.
Regular physical activity also helps to reduce an individual's cardiovascular risk. People of working age and healthy older adults are recommended a cumulative 2½ hours of exercise per week in the form of everyday activities (e.g. climbing stairs, gardening) or sport of at least moderate intensity. Medium intensity means getting at least slightly out of breath. Regular physical activity also helps to prevent accidents in old age and supports weight loss in overweight people.
Can a lack of sleep and excessive stress actually increase the risk of a heart attack?
Stress or lack of sleep also increase the risk of a heart attack. A permanently elevated stress level increases blood pressure, makes the heart beat faster, increases the release of stress hormones and insulin and weakens the immune system. All of these factors are bad for our heart. In addition, constant stress causes people to eat more unhealthily, exercise less, smoke more, consume more alcohol and sleep less. Overall, an unhealthy lifestyle is an important factor in increased cardiovascular risk. Noise and air pollution are also considered to be factors that significantly increase the risk of a heart attack: Noise, for example, leads to a disruption of the inner layer function of arteries ("endothelial dysfunction"), which is considered an important cause of cardiovascular diseases such as heart attacks and strokes. Air pollution, especially an increase in particulate matter and nitrogen oxides, leads to an increase in inflammation levels in the body. This systemic inflammation is also an important risk factor for various diseases, including cardiovascular diseases.
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