Myocardial infarction – symptoms, causes, treatment, and consequences

What is myocardial infarction

Myocardial infarction (MI), or heart attack, is one of the manifestations of coronary artery disease. In an MI, death (necrosis) of part of the heart muscle occurs, most often as a result of occlusion of a coronary artery. The extent of the infarct depends mainly on the site of the coronary artery occlusion and the duration of the occlusion.

In the Czech Republic, about 40,000 people suffer a heart attack each year, for 25% of whom it results in serious complications or death.

"The heart needs a constant supply of oxygen to function, which is supplied by the coronary arteries. When a coronary artery is critically narrowed or occluded, the contractile capacity of the affected area is lost relatively quickly. If the infarcted area is large, this can result in heart failure, where the heart is unable to circulate blood efficiently through other organs. However, even a mild infarction can be life-threatening – if dangerous arrhythmias develop in the infarcted area (e.g. ventricular fibrillation, ventricular tachycardia, or, conversely, significant pauses and bradycardia). The good news is that myocardial infarction is usually such a painful and uncomfortable condition that patients are usually “forced” to deal with the situation urgently," says Dr. Lucia Barčiaková, MD and cardiologist at the EUC Clinic Prague – Šustova.

If the blood flow through the coronary arteries is not restored in a short time (within about 2 hours), irreversible death of the heart cells affected by the infarction occurs.

"Necrotic areas are subsequently healed by scarring. The scar tissue will never again have the properties of the original muscle fibres; it does not have the ability to contract and can thus reduce the overall performance of the heart", explains Dr. Lucia Barčiaková.

 

Myocardial infarction: Causes

Myocardial infarction most often occurs as a result of atherosclerosis or coronary artery calcification. In atherosclerosis, narrowing, deformation, and blockage of the arteries occurs due to cholesterol deposition, which is accompanied by an inflammatory process in the artery wall. The immediate cause of myocardial infarction is usually the rupture of an atherosclerotic plaque with the subsequent formation of a blood clot (or thrombus) inside the artery. In addition to atherosclerosis, other diseases can rarely lead to a heart attack:

• vasculitis – an inflammatory disease affecting blood vessels (especially arteries)
• emboli in the coronary vascular system, e.g. in infective endocarditis or thromboembolism
• congenital vascular defects
• dissecting aortic aneurysm – a condition in which the inner wall of the aorta ruptures
• persistent vascular spasms – these can be caused spontaneously, but also under the influence of certain stimulant drugs
• takotsubo cardiomyopathy – has an effect on the development of stress infarction after a strong sudden stress stimulus in predisposed individuals

Secondary infarcts occur due to excessive cardiac workload, for example in metabolic disorders, sepsis, major bleeding, tachyarrhythmias, or periprocedurally during cardiac procedures.

In atherosclerosis, narrowing, deformation, and blockage of the arteries occurs due to cholesterol deposition, which is accompanied by an inflammatory process in the artery wall.

Risk factors for heart attack

Risk factors that can cause acute myocardial infarction generally include:

• age (in men the risk of heart attack increases linearly from the age of 45, in women it is initially lower, after menopause the risk levels off relatively quickly with the male population)
• genetic predispositions
• the presence of untreated high blood pressure
• high cholesterol or triacylglycerols in the blood
• diabetes
• smoking
• obesity
• socio-economic status
• overall unhealthy lifestyle (improper diet, lack of regular exercise and sleep, excessive stress, long-term use of certain addictive substances)

Symptoms of myocardial infarction

In some cases, a heart attack manifests itself with a rapid onset of pain or cardiac arrest, at other times there is some kind of warning with a warning of several hours or days in advance. In about 20% of patients, the symptoms of a heart attack are so-called atypical. In less than a tenth of cases, the heart attack is asymptomatic, a so-called silent myocardial infarction. However, it typically manifests itself as follows:

• dull, pressing, severe, pinching or burning pain behind the sternum preventing more strenuous activity
• pain may radiate (usually) to the left arm, neck, jaw, back
• lasts longer than 15 minutes
• does not respond to changing the position of the affected person and even administration of nitrates does not help at all
• may be accompanied by sweating, palpitations, acute shortness of breath, nausea, vomiting, restlessness, anxiety or confusion

In the most severe cases, the sufferer may fall unconscious as a result of cardiac arrest. As already mentioned, a heart attack can cause sudden death as a result of a rupture of the heart wall, a serious disturbance of the heart rhythm, or extensive involvement of the heart muscle.

 

Division of myocardial infarction

A heart attack can be divided according to its localization, which depends on the area supplied by the affected coronary arteries, as follows:

1. left ventricular anterior wall infarction – the most common form of heart attack
2. left ventricular lateral wall infarction
3. left ventricular posterior wall infarction – can affect the sinoatrial node, the natural pacemaker that determines the heart rhythm
4. infarction of the inferior wall of the left ventricle of the heart
5. right ventricular infarction

Infarcts can be further divided according to the degree of cardiac wall involvement into:

• transmural – affecting the entire thickness of the heart wall
• non-transmural – affecting the heart muscle only to a certain depth

Another division is based on the ECG picture, where infarction without or with ST segment elevation or other equivalents (so-called brachial artery blockades) is distinguished.

Last but not least, we divide a heart attack into acute and subacute (ongoing).

 

Diagnosis and treatment of myocardial infarction

"Diagnosing myocardial infarction is not always easy and often requires a combination of different tests. The key is the demonstration of necrosis in the blood using troponin. Today's highly sensitive laboratory methods can detect even slight necrosis of myocardial cells if the infarction occurs within a sufficient time interval from the time of sampling. Therefore, even with a negative blood troponin result and persistent suspicion of infarction, blood is drawn sequentially for troponin for final verification. Another very important diagnostic method for myocardial infarction is ECG examination. The ECG is available in the emergency room at the first contact of the paramedics with the patient. In the case of typical chest pain and the finding of a typical “STEMI” ECG picture, there is no longer any need to wait for confirmatory laboratory results, and the ECG itself is the ticket to theatre. However, the limitations of the ECG findings can be many, and therefore ECG is not the primary method to rule out myocardial infarction in a patient with typical chest pain," explains Dr. Barčiaková, MD.

 

Goal of treatment

The goal of treatment of myocardial infarction is to restore normal flow in the affected coronary artery as quickly as possible, i.e. immediate transport of the affected person to a specialized cardiac centre that performs coronary catheterization. This is performed by access via the femoral or radial artery. Using heart catheters and other special instrumentation, the closed/narrowed artery can be made patent and widened, and usually coronary stents can be inserted to maintain the patency of the artery. This procedure is called coronary angioplasty or coronary stenting.

With timely intervention, it is possible to save or reduce the infarct lesion. In some cases, cardiac surgery is necessary to ensure blood supply to the affected areas by coronary bypass grafts (bypass grafts). Cardiac surgery may also be indicated as the first method of treatment when the findings are severe or angioplasty is not possible. Medical treatment, which is permanent, is also an integral part of the treatment.

"After an uncomplicated heart attack, the patient is usually admitted to a monitored bed for the first 24-48 hours because of possible arrhythmic and postprocedural complications. The length of hospitalization depends on the extent of the infarction and the patient's general condition. When discharged from hospital, the patient has a treatment plan set up, which is then adjusted with his/her outpatient cardiologist according to the development of problems and findings," adds Dr. Lucia Barčiaková, MD.

 

Myocardial infarction – first aid

The timely provision of first aid is essential for rescue. If you find yourself in a situation where you need to help a person likely having a heart attack, do the following:

1. Call 155 and stay with the patient until the ambulance arrives.

If the casualty falls unconscious, call 155, and if the patient is not breathing, perform indirect cardiac massage (at a rate of 100 chest compressions per minute).

During resuscitation, approach a specific bystander to relieve you. Indirect cardiac massage is extremely physically demanding, so take turns about every 2 minutes.

2. Do not take the patient anywhere alone, but wait for the ambulance to arrive.

The patient should be admitted to the cardiac centre as soon as possible, optimally within 1 hour of the onset of chest pain. If he does not get to the doctor in time, the heart can be seriously damaged.

Consequences, rehabilitation, and life after a heart attack

Myocardial infarction can have a number of serious consequences. The most common are a transient or permanent reduction in cardiac output, post-infarction mitral valve defect, and, in the most serious cases, a heart attack can be the immediate cause of death. In addition to this extreme possibility, there are other consequences:

1. pericarditis, an inflammation of the pericardium
2. mural thrombi and their potential embolization – blood clots most often forming in the left ventricle and attaching to its inner wall from the inside
3. left ventricular aneurysm – an aneurysm of the left ventricular wall
4. myocardial rupture – rupture of the heart wall

"A patient who has already had a myocardial infarction is at significant risk of further heart attacks or other cardiovascular events. That's why the initial treatment of coronary arteries with a stent or bypass grafting is followed by lifelong pharmacological treatment, which has fairly simple goals – not to have another heart attack, to reduce the risk of death from cardiovascular disease, and to feel as well as possible. In addition, in the first year after a heart attack, the patient is also at risk of a potential complication – thrombosis of the stent itself, in which there is a risk of recurrent heart attack at the same site that has already been treated once. This unpleasant complication is now very effectively prevented by specific anticoagulants and their combinations. At the same time, the risks of potential side effects of certain drugs need to be minimised. And last but not least – in the case of large myocardial necrosis resulting in chronic heart failure, i.e. if the consequences of the infarction are permanent, it is crucial to maintain the circulation in such a state with the help of pharmacotherapy that all organs are as calm as possible and the patient feels as limited as possible," adds Dr. Lucia Barčiaková, MD.

 

Rehabilitation

Rehabilitation after a heart attack focuses mainly on physical activity and lifestyle modification. As soon as the patient's condition allows, the following regimen measures are recommended:

• No smoking: The chemicals in cigarettes adversely affect the walls of blood vessels, making smokers much more likely to suffer from coronary heart disease, and quitting smoking means halving the risk of a heart attack.
• Appropriate diet and lifestyle: A healthy lifestyle and diet significantly reduce the risk of subsequent heart problems.
• Lowering cholesterol: Cholesterol is involved in the formation of plaques that build up in the walls of blood vessels and narrow them; its level is regulated by diet and medication.
• Alcohol restriction: It is best to avoid alcohol completely. Initially, alcohol interacts with the medications given after a heart attack, but it is generally not good for the nervous system or liver. The positive effect on the arteries does not outweigh the risks associated with long-term use of alcohol in any quantity.
• Adaptation of physical activity: Shorter walks are recommended at first, then physical activity can be gradually increased: from about 20 to 30 minutes of walking per day to moderate-intensity exercise, but activities that require sudden high effort should be avoided.
• Treatment of high blood pressure: This is a major risk factor for heart disease and must be measured regularly.
• Minimise stress: You can return to work after about 1 to 3 months, depending on the type of job. If the work is medically unsuitable, a partial disability pension can be applied for.
• Good correction of other associated diseases: It is particularly related to diabetes, obesity, and lung diseases.

 

Prevention of myocardial infarction

The risk of heart attack increases with the number and intensity of individual risk factors. Therefore, the best way to prevent heart attacks is to minimise the influential risk factors (smoking, treatment of high blood pressure, cholesterol and diabetes, inappropriate diet, overweight, lack of exercise, stress).

In some cases, the hereditary predisposition to cardiovascular disease is so significant that even a perfect lifestyle will not completely prevent a heart attack.

Preventive medical check-ups are also important, focusing on risk factors that are currently causing only minor or unnoticed problems (high blood pressure, elevated blood lipid levels, incipient diabetes, obesity). If these factors are identified and treated early, the risk of heart attack can be significantly reduced.

If you experience symptoms indicating a heart attack, seek medical attention immediately. You can also contact the experts at EUC clinics for preventive advice on risk factors for cardiovascular disease or care after a myocardial infarction.