Heart attack (myocardial infarction)

A heart attack (myocardial infarction) occurs when the blood vessels of the heart (coronary vessels), which are responsible for supplying the heart muscle, become blocked. The heart muscle has the task of pumping blood around the body. Normally, three of these large blood vessels (coronary arteries) supply the heart with blood and oxygen.

If these vessels become blocked, as is the case with a heart attack, not enough oxygen and nutrients reach the heart. If the blocked vessel is not opened within a few hours, the part of the heart muscle supplied by the affected vessel may die. For this reason, every heart attack is considered an emergency.

In industrialized countries, the number of heart attacks is steadily increasing. The main cause is coronary heart disease (CHD), which is promoted by various factors such as obesity, lack of exercise and smoking.

Sick vessels:

The most common trigger for a myocardial infarction is coronary artery disease (CAD). Sometimes an inflammation of the coronary vessels or a washed up blood clot (embolism) can also cause a heart attack.

Coronary artery disease can be recognised by the deposits in the arteries, which are also called plaques. Sometimes, even in young adults, the onset of such arteriosclerosis can be detected. The plaques lead to a reduction of the inner space of the blood vessels and, as a consequence, to a restricted blood flow.

The plaques can show small tears, which are then immediately closed by blood platelets. During this process, messenger substances are released, which in turn attract further platelets. As a result, a blood clot (thrombus) is formed, which clogs the entire vessel and thus leads to an interruption of the blood supply. All in all, these processes cause a heart attack.

However, it is still uncertain for what reason some plaques rupture and thus cause a high risk of heart attack, while others do not rupture for years. It is already known that deposits containing many fat cells and little calcium are unstable. The same is true if there is a high concentration of inflammatory substances in the blood (such as C-reactive protein, CRP). High levels of inflammation are most commonly found in people who have a lot of abdominal fat or metabolic syndrome. Other risk factors that make plaques unstable include nicotine and particulate matter.

Risk factors:

Some factors are known to increase the risk of heart attack due to vascular calcification. Generally speaking, the higher the number of risk factors, the more likely you are to have a heart attack.

• Diet: high fat and energy dense foods result in obesity and high cholesterol levels.
• Obesity: Is the result of an unhealthy diet over many years.
• Lack of exercise: regular exercise leads to lower blood pressure, as well as better cholesterol levels and increased insulin sensitivity in muscle cells.
• Male sex: Pre-menopausal women are less at risk, as female sex hormones (such as estrogens) initially provide protection.
• Genetic predisposition: Genes also appear to play a role, as a clustered occurrence of cardiovascular disease has been observed within families.
• Smoking: Some substances present in tobacco smoke (cigarettes, cigars, pipes) cause the development of unstable plaques.
• Increased blood pressure: hypertension causes damage to the inner walls of the blood vessels.
• Elevated cholesterol levels: High LDL levels and low HDL levels are particularly dangerous.
• Diabetes mellitus: Poorly controlled diabetes causes permanently high blood sugar levels, which lead to damage to the vessels.
• Increased inflammation values: An example of this is an increased CRP value, which makes the plaques unstable.
• Age: With increasing age, arteriosclerosis also increases.

It has not yet been proven whether an increased value of the protein building block (amino acid) homocysteine also represents a risk factor.

If there is even the slightest suspicion of a heart attack, the emergency services must be called immediately.

Characteristic signs that indicate a heart attack are:

• Strong pressing or burning pain in the front left chest area that occurs suddenly. However, the pain may also be felt in the upper abdomen, back or jaw. Often, the pain may also radiate to the left arm.
• Feeling of anxiety, tightness or fear
• Acute severe shortness of breath, as well as unconsciousness or severe dizziness

Depending on which coronary artery is affected, the symptoms can manifest themselves differently. If the posterior coronary arteries are occluded, a posterior wall infarction occurs, which can be noticeable through pain in the upper abdomen. An anterior wall infarction occurs when the left coronary arteries are affected by the blockage. This is characterised by complaints in the chest area.

Acute cardiac death usually occurs as a result of occlusion of the large coronary vessels.

It is important to distinguish a heart attack from an angina attack. Both can cause the same symptoms, but angina pectoris, unlike a heart attack, is caused by a narrowing of the blood vessels rather than an occlusion of the vessels.

About 15 to 20 percent of all heart attacks have a painless course (silent attacks). This occurs mainly in patients suffering from diabetes mellitus. 30 to 50 percent of heart attacks occur suddenly and unexpectedly without any prior pain.

Women show different symptomatology than men. Among the characteristics are:

• Only one-third of women experience chest pain.
• The majority of those affected experience fatigue
• About 50 percent complain of sleep disturbances
• Some patients are short of breath
• Some women may experience stomach pain

Since in many cases the signs are not interpreted correctly, women undergo clinical treatment about an hour later. This shows that the proportion of women who die of a heart attack is higher than that of men.

In general, a heart attack can be diagnosed on the basis of the symptoms. However, in order to be sure and to exclude other diseases that are also accompanied by chest pain, the following examinations can be carried out:

• ECG: The electrocardiogram (ECG) represents the most important examination method to detect a heart attack. With the help of this procedure, typical changes, which also allow conclusions to be drawn about the size and location of the infarction, can be made visible. In addition, the ECG can also be used to diagnose any cardiac arrhythmias. These are the most common complications of a fresh infarction. However, the changes cannot be detected immediately after the infarction has occurred, but only a few hours later. For this reason, if a heart attack is suspected, it is recommended that several examinations be performed, each a few hours apart.
• Blood tests: If muscle cells die, as is the case with a heart attack, certain proteins are released. If the patient suffers a heart attack, the concentration of these proteins in the blood is increased. These markers include troponin T, troponin I, myoglobin and creatinine kinase (CK-MB). However, here too, an increase can only be observed a few hours after the infarction has occurred.
• Cardiac ultrasound/echocardiography: If the ECG does not provide any information, but the symptoms nevertheless indicate an infarction, a cardiac ultrasound (echocardiography) can provide indications. On the basis of this examination, the doctor can detect wall movement disturbances. If there is interrupted blood flow as a result of the heart attack, abnormal movement of the affected section of the heart occurs.
• Cardiac catheterization: A cardiac catheterization helps detect affected coronary arteries, and provides clues as to whether other vessels are affected. In this way, the heart muscle and the heart valves can also be checked to ensure that they are functioning properly.

Heart attack patients must undergo treatment in the intensive care unit. The treatment aims to reopen the blocked blood vessel as quickly as possible (reperfusion therapy). If normal blood flow is restored as soon as possible, the chances are good that little heart muscle tissue will have died ("time is muscle") and fewer acute and chronic complications will occur.

The following treatment methods can be used for reperfusion therapy:

• Lysis therapy (thrombolytic therapy):

In this type of therapy, the blood clot (thrombus) that caused the infarction is dissolved by medication (lysis). To achieve this, drugs are administered into the vein that either cause the thrombus to break down directly or activate the body's own breakdown enzymes (plasminogens), which also cause the blood clot to dissolve. Shortly after the heart attack, the chances are best to reopen an affected coronary vessel. This treatment can already be carried out by the emergency doctor. As a result, the blocked vessel can be reopened within 90 minutes in 50 percent of cases.

If the heart attack has already occurred some time ago, it becomes increasingly difficult to open the blood vessel. Lysis can be performed a maximum of 12 hours after a heart attack. After these 12 hours, the blood clot can no longer be dissolved properly, which leads to considerable side effects.

The enzymes streptokinase and urokinase, as well as the genetically engineered activators alteplase, reteplase or tenecteplase can be used for lysis. The lysis drugs have the effect of inhibiting the body's own blood clotting in the body, as they exert their effect on the entire body and not just the heart. Serious bleeding can occur as a complication. Other complications include activation of previously unrecognized sources of bleeding such as gastric ulcers, and vascular malformation in the brain (aneurysms). Among the most serious side effects is cerebral hemorrhage, which occurs in about one percent of cases. After thrombolytic therapy, patients often suffer from cardiac arrhythmias, so patients must be monitored closely.

• Acute PTCA:

In this treatment, a cardiac catheter is inserted immediately to dilate the blocked vessel with the help of a balloon (acute PTCA). In many cases, a stent is implanted during this treatment to prevent the vessel from blocking again.

In the majority of patients, acute PTCA can achieve reopening of the vessel. The disadvantage, however, is that PTCA is not immediately available for all patients, as not all hospitals have cardiac catheterization facilities. The therapy only achieves success if it starts within 90 minutes. It is clear from numerous studies that acute PTCA offers certain advantages over lysis therapy.

• Rescue PTCA:
  

If lysis therapy does not achieve success and the patient is still suffering from pain, as well as worsening of the condition, a cardiac catheterization may be considered to open the vessel (salvage PTCA).

Occasionally, the coronary arteries are so narrowed that bypass surgery is necessary to correct the heart attack. In this operation, the narrowing of the vessel is bridged by a vein, which is either a chest wall artery or taken from another part of the body.

Basic therapy for acute myocardial infarction includes:

• Acetysalicylic acid: this agent prevents platelets from sticking to the blood, thus increasing the size of the blood clot. If a heart attack is suspected, the emergency doctor already injects acetylsalicylic acid to improve the prognosis.
• Heparin: Heparin interferes with the blood clotting system and counteracts thrombus enlargement. It can also be administered by the emergency physician.
• Beta-blockers: Beta-blockers lead to a lowering of the blood pressure, as well as to a slowing of the heartbeat and consequently to a relief of the heart. Early administration counteracts life-threatening cardiac arrhythmias (ventricular fibrillation) and reduces the size of the infarction.
• Nitrates: They dilate the blood vessels and lead to a reduction in the oxygen demand of the heart. They also reduce pain, but do not improve the prognosis.
• ACE inhibitors: These drugs cause the blood vessels to dilate and blood pressure to drop. Thus, they relieve the heart and reduce the risk of mortality in infarction patients. For this reason, therapy should be started within 24 hours.
• Pain therapy: If the need arises, painkillers and sedatives can be administered, which should lead to the patient being free of pain.
• Oxygen: Oxygen is administered to all affected patients through a nasal tube, as this helps to ensure oxygen supply to the heart.

Aftercare:

Aftercare is also of great importance for the prognosis of heart attacks. Already within the first days, patients should start with physiotherapy and breathing exercises. Physical activity can also counteract further vascular occlusion.

A few weeks later, cardiovascular training can be started. This does not mean competitive sports, but rather sports such as hiking, light jogging, cycling and swimming. The attending physician is responsible for an individual training program in cooperation with the patient.

Factors such as high blood pressure, high cholesterol levels, obesity and diabetes increase the risk and should therefore be checked at regular intervals. Another important factor is smoking, which should be stopped immediately. In addition, control examinations should be carried out at regular intervals (every six months to annually).

In heart attacks, death usually occurs as a result of ventricular fibrillation.

The faster the opening of the occluded vessel, the better the prospects for recovery. The best results are achieved with a therapy that starts within 3 hours. If a heart attack is now suspected, the patient should be treated immediately in hospital.

The size of the infarction, as well as possible changes in other coronary vessels also exert influence on the prognosis.

Acute complications:

Many sufferers experience cardiac arrhythmias in the course of the heart attack. In many cases there is a very fast heartbeat (sinus tachycardia), in 10 to 15 percent of cases atrial fibrillation. Life-threatening situations such as ventricular fibrillation are also not excluded.

A heart attack can also be accompanied by acute cardiac insufficiency, in which the heart is no longer able to pump sufficient blood through the body. Occasionally, a part of the heart wall may rupture as a result of a heart attack.

The first 48 hours after a heart attack are the most risky time for the patient. About 40 percent of those affected do not survive the first few days.

Long-term complications:

An acute heart attack leads to a major change in the life of the affected person. Quite a few suffer from depression in later life. It is particularly important to change to a healthy and active lifestyle.

If a lot of muscle mass dies as a result of the heart attack, chronic cardiac insufficiency develops over time, as the dead heart muscle tissue forms scars. The pumping capacity then depends on the size of the affected area.

Heart failure can also develop as a result of many small heart attacks ("small vessel disease"). In some cases, part of the heart wall bulges out (aneurysm), creating better conditions for the formation of a blood clot. If these get into the body with the bloodstream, they can get stuck in one place and block the vessel. If this happens in the brain, it is called a stroke.

Sudden cardiac death due to ventricular fibrillation is a common cause of death after heart attack. However, less threatening cardiac arrhythmias such as atrial fibrillation can also occur.

Heart attacks can be prevented to a certain extent by keeping the risk factors for arteriosclerosis as low as possible. Arteriosclerosis creates optimal conditions for coronary heart disease (CHD), which is the most common cause of heart attacks. For this reason, much emphasis should be placed on a healthy lifestyle:

• Smoking should be given up. Optimally, it should not be started in the first place.
• A healthy diet should be a priority. This includes a lot of fruit and vegetables, as well as little fat.
• If you are overweight, you should try to lose weight. Even a few kilograms less have a positive effect on health.
• Regular exercise should be planned into the daily routine. Even a half-hour walk has a positive effect.
• Factors such as diabetes mellitus, high blood pressure or elevated cholesterol levels should be treated.
• Medications prescribed by the doctor should be taken at regular intervals. This applies even if one is not suffering from any symptoms at the moment.
• In the long run, the stress factor should be kept as low as possible.

If a heart attack is suspected, the emergency doctor should be called immediately. Under no circumstances should you drive yourself to hospital, as your condition can deteriorate from one second to the next.