Myocardial infarction and sudden cardiac arrest are two cardiac emergencies. Both are life-threatening, but their mechanism is completely different. What are the differences in causes, symptoms and how to help the victim in each case is explained by Szymon Budrejko, MD, PhD, from the Department of Cardiology and Cardiac Electrotherapy at the Medical University of Gdańsk, Board member of the Heart Rhythm Section of the Polish Cardiac Society.
The heart - mechanical and electrical work
- The function of the heart is to pump blood, which, together with oxygen, is delivered to all organs and tissues in the human body. In order for our "pump" to work properly, it needs a stimulus, a kind of "pacemaker", to operate. No less important is the heart's appropriate mode of operation; maintaining the correct cycle of its contractions and diastoles, i.e. proper 'control'," says Dr Szymon Budrejko.
In the heart, everything starts with an electrical signal - an impulse that gives the 'command' to the appropriate cells to contract and diastole in the correct sequence. Without the correct heart rhythm, that is, the correct cycle of contraction and diastole of the heart - the excitation of first the atria and then the ventricles - there is no proper control. The correct control signal is followed by the contraction of the heart cavities, which eject blood, pushing it through the heart and from there to the periphery. There are therefore two different mechanisms going on in the heart: electrical and mechanical. Both are extremely important for the proper functioning of the organ and the entire organism and are inextricably linked.
Myocardial infarction - blockage in the coronary arteries
- Although you sometimes see the term "heart attack" in media reports, it is worth knowing that in Polish medical terminology such a term does not exist. It is a colloquial term and a linguistic carbon copy, a literal translation of the English expression heart attack. The correct Polish-language name for the condition referred to by this term is myocardial infarction. It is worth knowing this," says Dr Szymon Budrejko.
Myocardial infarction is a condition in which blood flow in the coronary arteries is partially or completely blocked, resulting in myocardial ischaemia and necrosis. Myocardial infarction usually occurs as a result of the rupture and detachment of a fragment of atherosclerotic plaque that suddenly blocks a coronary vessel. This leads to blood clotting and closure of the vessel lumen. If the blood supply to a certain area of the heart is impeded or even cut off, tissue fragments deprived of nutrients and oxygen contained in the blood begin to die. This condition can occur as a result of severe stress, exertion or various inflammatory factors, among others. This is an emergency and urgent intervention is required.
Heart attack - how to help?
The symptom of a heart attack is a sudden and severe pain in the chest. The person may be conscious, breathing normally or have accelerated breathing, their pulse is palpable and often the pulse is also accelerated. Other symptoms of a heart attack may include weakness, pallor and the presence of sweats.
- In the event of a myocardial infarction, first aid consists of calling the ambulance service immediately, following the instructions of the dispatcher and ongoing observation of the victim. It is not necessary to undertake cardiopulmonary resuscitation. In this case, the aim is to transport the victim to a centre with specialised cardiac care as quickly as possible and to restore the normal blood supply to the heart muscle as soon as possible. The situation changes when, as a result of a myocardial infarction, a victim suffers sudden cardiac arrest (SCA) (this does not have to happen, but it is possible). SCA is primarily recognised by the victim losing consciousness, having no palpable pulse or breathing. In such a case, there is an immediate threat to life and the correct procedure is quite different," points out Dr. Szymon Budrejko.
Sudden cardiac arrest - a deadly arrhythmic problem
- Sudden cardiac arrest (SCA) is a condition in which mechanical heart function ceases. The cause may be a "control system" malfunction - for example, the occurrence of an arrhythmia, which causes the electrical impulse in the heart to spread so rapidly and/or chaotically that the heart contracts and diastrates asynchronously and the disturbance in its cycle becomes so severe that our "pump" is unable to do its job properly and distribute blood properly. Cardiac cessation occurs. This is an immediate life-threatening condition requiring immediate intervention," explains Dr Szymon Budrejko.
As the specialist explains, sudden cardiac arrest can occur, among other things, as a result of the blood supply being 'cut off' during a heart attack. The deterioration or stoppage of the blood supply to the heart muscle leads to a lack of energy for the 'pump' and to a disruption of the mechanical function of the heart, but can also affect the electrical 'control system' of the heart and lead to life-threatening cardiac arrhythmias. A myocardial infarction may (but not necessarily) lead to an arrhythmia, resulting in sudden cardiac arrest. At the same time, sudden cardiac arrest due to arrhythmia can occur not only in myocardial infarction. Myocardial infarction is one possible cause of ventricular fibrillation or ventricular tachycardia - two life-threatening ventricular arrhythmias that can lead to cessation of heart function. Indicated arrhythmias can also occur in patients whose heart is damaged by chronic ischaemia (i.e. long-standing coronary heart disease), even if they have never had a heart attack or have had one a long time ago.
Sometimes SCA occurs as a result of other abnormalities or diseases. These include, for example, genetic heart diseases that, due to ionic disorders, disorganise the electrical function of the heart and contribute to arrhythmias. Sometimes, signs of this type of disease are diagnosed in a follow-up ECG, but this is not always the case. A history of various cardiac conditions present in the patient's immediate family may be helpful. If someone close to the patient has been resuscitated or has had an implantable cardioverter-defibrillator (ICD), this is an important diagnostic clue.
Sudden cardiac arrest can also occur as a result of heart failure due to dilated cardiomyopathy. In this case, the heart is severely damaged and impaired as a result of the disease. However, SCA can also occur in an organically healthy heart - in young people, including athletes. Each case requires a detailed diagnosis aimed at eliminating the cause of SCA and preventing possible future incidents.
Sudden cardiac arrest - how to help?
The most important symptom of cardiac arrest is loss of consciousness. In cardiac arrest , in contrast to brief fainting, the patient does not regain consciousness spontaneously after a while. The patient has an undetectable pulse and is not breathing properly.
In SCA, the only way to help the victim is to call for help immediately and take resuscitation action. Experience and research show that the quicker such action is taken (the main element of which is the so-called external cardiac massage, i.e. rhythmic compressions of the sternum and chest), the greater the chances of survival of the victims (therefore it is important to train as many people as possible in this area at every possible opportunity). In addition, defibrillation, which is the delivery of an electrical impulse to restore the patient's heart rhythm, may be necessary. It is worth remembering that defibrillation can be carried out by professional emergency services, but also by an AED (Automated External Defibrillator) - an automated external defibrillator. This device, which is available in an increasing number of public and non-public outlets, once connected to the victim will analyse their heart rhythm independently, instruct the responders and, if necessary, carry out the defibrillation, thus protecting the victim until the arrival of the ambulance.
- The thing with an AED is that, first of all, it is worth knowing about the device. Then your natural reflex will be to seek it out in the event of an incident involving a victim due to sudden cardiac arrest. Secondly, it is worth keeping calm, reaching for the system and reading the instructions. The device will guide you step-by-step; as you render assistance using the AED, you learn what to do next. It is important to know that defibrillation will only be carried out by the system if the device considers it necessary based on its analysis. Otherwise, it will tell you what to do next. Either way, there is no harm in using an AED on a SCA victim - let us absolutely remember this and not be afraid to use the system. SCA is an immediate life-threatening condition. Immediate defibrillation and restoration of heart action is often the only chance of survival and avoiding disability and invalidity! - appeals Dr Szymon Budrejko.