Generality
Cardiac arrest, also known as sudden cardiac death, is a serious emergency situation characterized by the sudden and abrupt cessation of the heart's pumping activity, loss of consciousness and shortness of breath.
To save the lives of those suffering from cardiac arrest, rescuers must act immediately and with clarity. In fact, death and permanent damage to some organs of the body (for example the brain) can occur after just a few minutes.
Sinus rhythm and arrhythmias
The heart is an organ formed by a particular muscle, called myocardium, capable of generating and conducting the impulses for the contraction of the atria and ventricles by itself. The source of these impulses, which are comparable to electrical signals, is located in the right atrium of the heart and is called the sinoatrial node.
The sino-atrial node has the task of marking the right rate of contraction of the heart organ, in such a way as to guarantee a normal heart rhythm. The normal heart rhythm is also called sinus rhythm.
A "cardiac arrhythmia is" an alteration of the normal heart rhythm, which can become faster, slower or become irregular.
What is cardiac arrest?
Cardiac arrest is an emergency clinical condition characterized by the sudden and unexpected interruption of cardiac activity and loss of consciousness and respiratory capacity.
It is so serious that, if it does not intervene immediately, within a few minutes it causes permanent damage to the brain and the death of the affected individual.
Due to its characteristics of suddenness, unpredictability and lethality, cardiac arrest is also called sudden cardiac death or sudden cardiac arrest.
ARE HEART ARREST AND HEART ATTACK THE SAME?
Many often equate cardiac arrest with heart attack (commonly called heart attack).
However, they are two different disorders, in that they have a distinct nature: at the "origin of the" heart attack there is "an interruption in the flow of blood to the myocardium; at the "origin of" cardiac arrest, on the other hand, there is an "alteration of the sinus rhythm, or an" arrhythmia.
EPIDEMIOLOGY
According to a statistical study, in countries such as Italy or the United States, cardiac arrest has an annual incidence of one case per 1,000 inhabitants and high mortality (the survival rate, in the absence of any therapeutic treatment , is 2%).
Furthermore, it is more frequent among middle-aged people (in young people it is linked to particular congenital heart defects) and prefers the male sex (the ratio with women is 3 to 1).
Table. The numbers of cardiac arrest.
1 in 1000
Cases per year in Italy
About 60,000
Cases per year in the USA
About 320,000
Survival rate
2%
Survival if defibrillation occurs within 5 minutes
50%
Time to defibrillate (see the chapter dedicated to therapy)
Maximum 4-6 minutes
At what age is its onset most likely?
From the age of 45, for the man, and from the age of 55 for the woman
How many deaths from cardiovascular disease are due to sudden cardiac death
Over 50%
Causes
The cause of cardiac arrest is an anomaly in the conduction of electrical signals which normally contract the heart starting from the sinoatrial node. In other words, the cause of cardiac arrest is an "arrhythmia capable of interrupting the normal activity of the heart.
DO ALL ARRhythmias CAUSE A CARDIAC ARREST?
Arrhythmias are unusual and out of the ordinary episodes, but they don't always cause cardiac arrest.
They have a life-threatening effect when, with their changes, they drastically disrupt the heart's natural blood-pumping function.
A classic example of an arrhythmia capable of causing cardiac arrest is ventricular fibrillation.
Figure: ventricular fibrillation
This is characterized by a "so profound alteration of the heart rhythm, that the heart, instead of contracting and pumping the blood towards the various organs of the body, vibrates in a completely useless way.
Dangerous arrhythmias such as ventricular fibrillation usually appear when an individual suffers from severe heart ailments.
HEART DISORDERS ASSOCIATED WITH CARDIAC ARREST
Heart disorders (or heart disease) that can lead to cardiac arrest are:
- Coronary heart disease. Coronaries are the arterial vessels that oxygenate the myocardium. Their obstruction, due for example to the deposition of cholesterol, can block the internal blood flow and thus interrupt the oxygenation of the myocardium. Deprived of oxygen, the heart has a harder time working properly and is more prone to developing severe arrhythmic episodes. . Coronary heart disease is at the origin of most cardiac arrests.
- Heart attack. Previously it was specified that heart attack and cardiac arrest are two distinct pathological situations. This, however, does not exclude that heart attack may result in cardiac arrest; often, in fact, the "heart attack follows a coronary artery disease, which, as mentioned above," can actually upset the electrical system of the human heart muscle.
- Dilated cardiomyopathy. The term dilated cardiomyopathy identifies a disorder characterized by "thickening of the walls of the heart, in particular the walls of the ventricles. This thickening can determine a change in the conduction of electrical impulses, therefore an" arrhythmia.
- Abnormalities of the heart valves. The heart has four valves, which finely control the flow of blood through the atria and ventricles. Their malformation can affect the "onset of" arrhythmia, such as to cause an arrest of cardiac functions.
- Congenital anomalies of the heart. Some individuals are born with a malformed or imperfect heart. Such people are predisposed to developing a variety of heart problems, including cardiac arrest. Congenital heart abnormalities are a leading cause of sudden cardiac death in children and adolescents.
- Brugada syndrome and long QT syndrome. The heart of people suffering from these two syndromes has an abnormal electrical system. This can cause, in some unfortunate cases, the sudden onset of cardiac arrest.
RISK FACTORS
The picture of risk factors is very broad. A complete overview of the favoring situations is given in the following table:
- Cigarette smoke
- Hypertension
- Hypercholesterolemia
- Obesity
- Diabetes
- Sedentary life
- Alcohol abuse
- Familial predisposition to coronary heart disease
- A previous episode of cardiac arrest
- A previous heart attack episode
- Old age
- Male sex
- Use of drugs, such as cocaine and amphetamines
- Nutritional imbalances, such as low blood (i.e. blood) levels of potassium or magnesium
N.B: to underline the strong link between coronary heart disease and cardiac arrest, the risk factors common to both disorders have been reported on the left column.
Symptoms and Complications
For further information: Cardiac Arrest Symptoms
The most characteristic symptoms of cardiac arrest are: cardiovascular collapse, absence of pulse, lack of breath, loss of consciousness, convulsions and pale cyanosis.
These symptoms usually arise without warning and unexpectedly, although, in some rare situations, they may be preceded by fatigue, fainting, fainting, dizziness, chest pain, shortness of breath, palpitations and vomiting.
The suddenness of onset of symptoms is the property that makes cardiac arrest highly lethal.
COMPLICATIONS
During a cardiac arrest, the various anatomical districts of the body no longer receive oxygenated blood and gradually begin to damage themselves in a short time.
The first organ affected is the brain, which, in the absence of help, can suffer permanent damage already after 4-6 minutes.
Death can come just as quickly; in fact, it is very rare that after 10 minutes the patient is still alive (and even if he were, he would have brain damage incompatible with a normal life or would be in a coma).
Based on this timing, one can understand how essential it is, during a cardiac arrest, to intervene immediately and with the most appropriate treatments.
WHEN TO SEE THE DOCTOR?
Predicting or preventing cardiac arrest is somewhat complicated. Furthermore, its onset is so rapid that it does not give the possibility to consult a doctor in time.
However, if an individual frequently suffers from chest pain, heart palpitations, irregular heartbeat, tachycardia (i.e. rapid heartbeat), difficulty breathing and feeling faint, it is a good idea to seek medical advice and undergo a thorough cardiac examination. In fact, a predisposition to cardiac arrest could emerge from it.
Diagnosis
The first thing to do, in the event of cardiac arrest, is to provide immediate help to the affected individual. Therefore, any diagnostic examination and any investigation relating to the triggering causes (coronary artery disease, heart attack, etc.) is postponed to a later stage and if the patient survives.
The checks to be carried out are numerous and consist of:
- An electrocardiogram
- Blood tests of various kinds
- Diagnostic for images
- Other types of exams
The data emerging from their execution could help treat existing heart problems and prevent a possible second episode of cardiac arrest.
ELECTROCARDIOGRAM
The electrocardiogram measures the electrical activity of the heart. It, through the application of some electrodes on the chest and limbs, allows to measure the heart rate and any sinus rhythm disturbances.
It is a particularly useful control in cases of cardiac arrest due to a heart attack.
BLOOD TESTS
Blood tests are aimed at measuring and / or searching for: cardiac enzymes, electrolytes, drug substances and hormones.
- Research of cardiac enzymes. Following a heart attack, enzymes that are normally only present in the heart spread in the blood. Since a heart attack can result in cardiac arrest, the identification of these enzymes is an unequivocal signal of what the triggers were.
- Count of electrolytes. Electrolytes are minerals, such as potassium, magnesium and calcium, which allow the conduction of contractile electrical impulses. Their imbalance, found in the blood, may indicate the origin of the cardiac arrest.
- Research of pharmacological substances. Certain medications and certain drugs, such as cocaine, can cause various heart conditions, including cardiac arrest.
- Count of hormones. The hormone thyroxine, when in excess, gives rise to a pathological condition known as hyperthyroidism. Hyperthyroidism can trigger cardiac arrest.
IMAGE DIAGNOSTICS
Among the various diagnostic imaging tests, the following are extremely useful:
- Chest x-ray (chest x-ray). It is an X-ray examination that allows the doctor to evaluate the shape and size of the patient's heart. The presence of abnormal thickening of one or both ventricles may mean that cardiac arrest has arisen due to dilated cardiomyopathy.
- The "echocardiogram. It is an" ultrasound of the heart, through which the doctor can identify: damaged areas of myocardium, irregular pumping of blood and defects in the heart valves.
- The measure of the ejection fraction. The ejection fraction is the amount of blood pumped into the circulation by the left ventricle of the heart. Its measurement, which can be done through magnetic resonance imaging, CT scan, echocardiogram etc., allows you to establish if the heart has any functional defect. The ejection fraction is considered normal when it is higher than 50-55%, while it is considered indicative of cardiac arrest when it assumes values below 40%.
- Thallium scintigraphy combined with stress tests. The injection into the patient of a radioactive substance, such as thallium, allows the doctor to analyze how the blood flows through the heart and into the coronary arteries. Photographed by a particular device, the blood flow is monitored both in a resting phase of the patient both after a short stress test.
OTHER EXAMINATIONS
If the previous diagnostic tests deserve further clarification, the doctor is forced to resort to two invasive cardiac catheterization procedures, such as electrophysiological examination and coronary angiography.
- Electrophysiological examination. It is a test that analyzes how the transmission of electrical signals occurs in the heart. It is performed with the insertion into the blood vessels, and the subsequent conduction into the heart cavities, of various leads; these, by measuring the electrical activity of the heart, are able to identify the "diseased" heart area, responsible for the arrhythmia that gave rise to cardiac arrest.
- Coronarography. It is an examination for the identification of any narrowing or obstruction in the coronary arteries. It involves the use of a small catheter, which, once conducted up to the coronary vessels, emits a contrast liquid visible on X-rays. of this liquid, taken up by a special instrument, allows to study the anatomy of the vessels that oxygenate the myocardium, highlighting any anomalies.
CONTINUED: Treatment of "cardiac arrest"
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