Heart attack

Echocardiography can play an important role in the diagnosis of a heart attack. In a heart attack, blood vessels that normally supply the heart with blood, the coronary arteries, become blocked. If a coronary artery is blocked, parts of the heart muscle are undersupplied with oxygen and this undersupplied area of the heart muscle dies.

In most cases, blood clots are responsible for the occlusion of coronary arteries. The formation of these blood clots is promoted by various risk factors, such as smoking, obesity or high blood pressure. The diagnosis of a heart attack is made with the help of various examination methods.

First of all, the patient’s medical history is taken in detail. In the case of a heart attack, patients often complain of a feeling of pressure or tightness, as well as chest pain. In addition to the questioning, an electrocardiography (ECG) is always performed.

This often reveals typical changes that indicate a heart attack. In addition, a search is made for certain myocardial infarction markers (certain enzymes that indicate the death of heart muscles) in the patient’s blood. However, these parameters only increase after a few hours and are not yet measurable in the blood in the early phase of the heart attack.

One method that indicates disorders at an early stage (even before the myocardial infarction markers in the blood increase) is echocardiography, which is why this examination method plays an important role in myocardial infarction diagnostics. The death of heart muscle leads to the heart not being able to contract properly at this point, resulting in a movement disorder of the heart muscle. This movement disorder is visible in echocardiography.

Thus, it is possible to detect a fresh heart attack even before the heart attack markers in the blood rise.If echocardiography does not show any movement disorder of the heart muscles, a heart attack can be ruled out with a very high probability. To treat a heart attack, the obstruction in the affected coronary vessel must be removed. This is done either by dissolving the blood clot with medication or by mechanically expanding the constricted area using a cardiac catheter.

After a heart attack, the loss of heart muscle can lead to complications, such as reduced pumping capacity of the heart or functional disorders of the heart valves. For this reason, a further echocardiographic examination is often performed after the closure of the coronary artery has been removed. This would reveal the potential complications mentioned above after myocardial infarction and further treatment measures could be initiated.

Only transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE) are used in the diagnosis of myocardial infarction. Exercise echocardiography (“stress echo”) must not be performed under any circumstances in the event of a heart attack and until two weeks after a heart attack has occurred, as the increased heart rate would result in additional stress on the heart and thus an even poorer oxygen supply to the heart muscle. One aim of echocardiography is to assess the size of the heart.

In addition, the function of the various heart valves is checked. To decide whether a measured value is abnormal or normal, standard values exist as general guidelines. However, it should be remembered that the size of the heart also depends on the patient’s height and therefore varies from person to person.

Of particular interest are the diameters of the individual chambers and surrounding vessels, such as the aorta. In the following, standard values of relevant anatomical structures of the heart during echocariography are listed and sorted according to the physiological blood flow starting in the vena cava. The blood flows from the great circulation into the right atrium of the heart via the superior and inferior vena cava, which are approximately 20 mm wide.

This normally has a diameter of less than 35 mm. From there, the blood reaches the right chamber (ventricle) via the so-called tricuspid valve. The wall of the right ventricle is much thinner in the cardiac echo compared to the left ventricle.

The reason for this is the much lower resistance, namely the pulmonary circulation, against which the right ventricle must pump the blood. In addition, the diameter of the right ventricle is about 25 mm, which is slightly smaller than the left. Here it should be smaller than 45 mm.

The wall (septum) between the chambers is normally 10 mm thick. If the right chamber contracts, the pulmonary valve opens and blood flows through the lungs to the left atrium, which is about 40 mm in diameter. On its way to the aorta, the blood passes through two more valves, first the mitral valve and then the aortic valve.

At its root, the diameter of the aorta is still 40 mm, but shrinks to about 25 mm as it continues. In addition to the measurement of the previously mentioned cavities, echocardiography is used to check the function of the heart valves. This is done using the Doppler method.

This makes it possible to measure the speed of the blood flow. The following velocities should prevail at the four heart valves: In addition to measuring the heart cavities and the surrounding vessels and determining the flow speeds over the heart valves, echocardiography can also be used to determine other measured values. Echocardiography can also be used to estimate the pumping capacity of the heart on the basis of various measured values.

The values end-diastolic volume, end systolic volume, stroke volume and ejection fraction provide information on this. The end diastolic volume is the amount of blood in the heart after maximum filling and is between 130 and 140 ml in healthy individuals. End-systolic volume is the amount of blood still in the heart after a heartbeat and is about 50 to 60 ml in a healthy person.

The stroke volume is the amount of blood that is ejected into the body’s circulation per heartbeat. In a healthy person, the stroke volume is between 70 and 100 ml. With the help of the stroke volume and the end-diastolic volume, a further value can be calculated, the so-called ejection fraction.

The ejection fraction indicates the percentage of blood ejected in relation to the amount of blood after maximum filling of the heart. The ejection fraction is over 55 percent in healthy individuals.Echocardiography can also be used to determine the heart rate. It indicates how often the heart beats per minute and is between 50 and 100 beats per minute in healthy individuals.

The heart rate depends on the age and training condition of the person to be examined. Older people, as well as very sporty people, usually have a low heart rate, sometimes even below 50 beats per minute, but do not show any signs of illness. With the help of beat volume and heart rate, another value can be calculated which also provides information about the pumping capacity of the heart, the cardiac output per minute.

The cardiac output is the amount of blood that is pumped from the heart into the body’s circulation per minute. The normal cardiac output is 4.5 to 5 liters per minute. All the above values apply to healthy adults and vary according to gender.

Aortic valve 1.0-1.7 m/s
Mitral valve 0.6-1.3 m/s
Pulmonary valve 0.6-0.9 m/s
Tricuspid valve 0.3-0.6 m/s

For the evaluation of an echocardiography, the physician usually has a ready-made form at his disposal which he has to fill in. After the name of the doctor and the patient have been entered, the doctor has to indicate the exact method he has used. Then the individual heart cavities are evaluated according to the criteria described in the section “Standard values”.

The examiner determines the wall thickness in millimeters and compares it with the standard values. A slight magnification is indicated by a +, a stronger magnification by several. Once the doctor has measured both atria and chambers, the function of the chambers is checked.

Depending on the pumping capacity, the ventricle is evaluated in different gradations. These could be, for example: The contraction of the individual wall sections of the cavities is then observed and checked for irregularities. Even slight asynchronicity, which occurs for example in the case of excitation transmission complaints or heart attacks, can greatly reduce the heart’s pumping capacity.

In addition, the physician pays attention to possible hypokineses, i.e. a too slow contraction, or even akinesia, i.e. an inability of the myocardium to contract. This could also be caused by damage to the stimulus transmission system or circulatory disorders of the heart muscle.

Finally, the examination of the ventricular function is followed by the evaluation of the individual valves. The appearance is evaluated first. Visible enlargements, calcifications, tears, etc.

are documented by the physician. In addition, the movement of the cap is observed and conspicuous restrictions are noted. This is followed by the evaluation of the valve function.

Basically, two different types of valve dysfunction can be distinguished: stenosis on the one hand and insufficiency on the other. In a stenosis, the valve does not open properly so that the heart has to pump against increased pressure. In the case of valve insufficiency, it does not close sufficiently so that blood can flow back into the upstream cavity, thus causing a volume overload.

During echocardiography, the physician pays special attention to such valve defects and diagnoses them depending on their severity. For example, a mild insufficiency can be assessed with the word “minor”, while a severe insufficiency is described as “severe”.

Normal
Somewhat reduced
Medium reduced
Highly reduced.