Heart attack – definition, causes, characteristics, diagnostics, course

Heart attack - definition, causes, characteristics, diagnostics, course

Heart attacks are among the most common causes of death in Germany. The definition of a heart attack is the death of a part of the heart muscle of varying size as a result of a lack of oxygen, sometimes with life-threatening complications. Here, you can find out how and why a heart attack occurs, how to recognize it and what to do if you suspect it.

How does a heart attack occur?

As the engine of the circulatory system, the heart represents the driving force behind all blood circulation processes in the organism. Of course, the heart muscle also needs an adequate supply of oxygen for its continuous, very energy-intensive pumping activity. The blood supply to the heart muscle is ensured via the coronary arteries, which originate directly at the outlet of the aorta and fan out on the surface of the heart like the branches of a treetop.

The heart muscle reacts sensitively to circulatory disturbances that last only a few seconds. At the same time, the arms or legs of humans, for example, can cope with a circulatory failure for several hours without significant damage.

A heart attack occurs when the blood flow to the heart muscle via the coronary arteries becomes so severely restricted that part of the heart muscle dies.

 

Causes of a heart attack

In the vast majority of cases, such a heart attack is based on chronic calcification of the coronary arteries, which is favoured by high blood pressurediabetes, dyslipidemia, gout, obesity, smoking and genetic factors. Like calcium deposits in the pipes of a washing machine, narrowing of the coronary arteries forms over decades due to arteriosclerosis.

A heart attack occurs if an important vessel is completely blocked – usually by an additional small blood clot.

However, heart attack mechanisms are also conceivable in which the coronary vessels are healthy. This would be the case, for example, if a blood clot from the heart itself was carried along with the bloodstream, got into the coronary arteries, blocked a healthy vessel there and triggered a heart attack.

In sporadic cases, an acute thrombosis of a primarily healthy coronary artery or even a vascular spasm can trigger a heart attack.

Here is an overview of the possible causes of a heart attack:

  • Atherosclerosis (hardening of the arteries)
  • embolism (spread of a blood clot)
  • thrombosis (local formation of a blood clot)
  • vascular spasm (vasospasm)

General information about heart attacks

Heart attack is the most severe complication of coronary artery disease. In Western industrialized nations, it is far ahead in the cause of death statistics. On average, about 300 to 400 out of every 100,000 men aged 35 to 64 die as a result of a heart attack. Between the ages of 45 and 50, heart attacks occur significantly more frequently in men than in women.

In older people, these differences even out. In addition, it can be observed that the frequency of coronary heart disease and heart attacks in women has increased significantly over the past few decades – most likely as a result of nicotine consumption and taking the birth control pill.

Hardening of the arteries in the coronary arteries can take on very different forms and can also lead to a wide variety of symptoms. If the narrowing of the coronary arteries is only slight – usually less than 70 per cent of the vessel diameter – there may not be any symptoms at all. The complete occlusion of a coronary artery with a heart attack would give the extreme form.

In between, there are smooth transitions between angina pectoris symptoms during heavy physical exertion (stress angina)  and angina pectoris at rest  (rest angina), which can already be a harbinger of a heart attack. In addition, the severity of the symptoms of a patient with calcification of the coronary arteries also depends on his physical training condition and possible accompanying diseases such as diabetes.

 

characteristics and symptoms

Regular physical training improves the blood flow to the heart muscle, which is better protected against a heart attack. In some cases, a heart attack can be the first and, at the same time, the most dramatic manifestation of hardening of the coronary arteries. For example, a healthy person can have a fatal heart attack out of the blue.

The heart attack can also come at the end of a long-term increase in angina pectoris symptoms.

The symptoms of a classic heart attack are:

  • Severe, pressing chest pain, sometimes radiating to the left arm (“as if an iron ring were tightening around the chest”)
  • cold sweats
  • shortness of breath
  • paleness
  • Flat, rapid pulse
  • Anxiety feeling

However, a heart attack can also hide behind much less typical symptoms such as jaw pain, abdominal pain, back pain, nausea, vomiting, shortness of breath, fainting spells or cardiac arrhythmias. In individual cases, one also speaks of silent heart attacks, which are usually only diagnosed years later by chance in the electrocardiogram (ECG).

Fast action required

If a heart attack is suspected, the highest alert level is required. Even if the patients can still be brought to the hospital in this life-threatening emergency, 15 to 30 per cent die in the hours that follow. If the heart attack is survived, three per cent of patients still die every year from complications such as malignant cardiac arrhythmia, another heart attack or heart failure.

Laypeople, in particular, like to speculate about the specific triggering causes of a heart attack in individual cases. Contrary to popular belief, experience has shown that heart attacks occur much more frequently in rest than in stressful situations.

Diagnosis by EKG and blood tests

In the case of corresponding symptoms, the diagnosis can only be made with certainty using an ECG and specific blood tests since the transitions between circulatory disorders in angina pectoris and an actual heart attack are fluid. In the ECG, the doctor sees typical changes that indicate a heart attack: the heart region – the front wall, rear wall or side wall – affected by the heart attack can also be determined.

The blood tests, in turn, provide information about the extent and stage of the heart attack. The treatment must know the exact stage and ideally initiate the first measures at the earliest possible stage of the heart attack.

 

the course of the heart attack

If the heart attack started more than four to six hours before the diagnosis was made, significant irreversible damage to the heart muscle must already be expected. The body usually replaces the dead portion of the heart muscle within 10 to 14 days with a fibrous scar, like a skin burn.

Of course, this scar material does not have the performance capacity of the formerly intact heart muscle, so after a heart attack the heart muscle weakness often persists to the point of cardiac insufficiency.

When no precise diagnosis is possible

Sometimes, the diagnosis – especially in the case of small infarctions – cannot be made unequivocally. In case of doubt, however, a patient is treated like an actual heart attack for safety reasons; in addition to indirect methods such as blood tests and ECG, the coronary artery changes can only be seen directly through a heart catheter examination.

In this procedure, the coronary arteries are identified using long plastic tubes pushed through the groin vessels to the heart and imaged using X-ray contrast media. Classically, an occluded infarction vessel is found in the case of an acute myocardial infarction. In addition, a reduced contraction force can be detected in the heart muscle region previously supplied with blood by the infarction vessel.

Even years after a heart attack, the regionally reduced contraction force of the heart muscle persists and can be diagnosed by a heart catheter examination or – much less complex – by an ultrasound examination of the heart. However, suppose the coronary arteries are unremarkable during the cardiac catheter examination in the acute infarction. In that case, there is a suspicion of an embolic infarction (with self-dissolving of the blood clot) or, rarely, of a vasospastic infarction.

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