Myocardial infarction. ECG in myocardial infarction

Myocardial infarction - is necrosis (death) of cardiac muscle resulting from impaired circulation, which leads to the lack of oxygen supplying to the heart muscle. Myocardial infarction nowadays is one of the leading causes of death and disability of people in the world.

Symptoms of myocardial infarction

There are several variants of myocardial infarction depending on the symptoms.

Anginal is the most common variant. It manifests itself by the durational pain which persists more than an hour and does not subsides after taking the medication (nitroglycerin). The pain is severe constricting behind the breastbone. This pain can irradiate to the left half of the chest and the left arm, jaw and back. The patient may feel weakness, anxiety, fear of death, profuse sweating.

Asthmatic is the variant accompanied by shortness of breath or suffocation, palpitations. Pain usually lacks, otherwise it may precede dyspnea. This variant of the disease is common in older people and for those with old myocardial infarction.

Gastralgic is the variant, which is characterized by unusual localization of pain, which manifests itself in the upper abdomen. It can spread into the shoulder blades and back area. This variant is accompanied by hiccups, eructation, nausea, vomiting. Bloating may occur due to bowel obstruction.

Cerebrovascular – the symptoms associated with cerebral ischemia: dizziness, fainting, nausea, vomiting, loss of spatial orientation. The appearance of neurological symptoms complicates diagnosis. Only ECG results in proper diagnosis.

Arrhythmic – the main symptom is palpitation: a feeling of heart failure and interruptions in its work. There is no pain or slight pain. There may be weakness, shortness of breath, syncope or other symptoms caused by the fall in blood pressure.

Oligosymptomatic - the detection of myocardial infarction is only possible after ECG. However, a heart attack may be preceded by mild symptoms such as unexplained fatigue, shortness of breath, arrhythmias.

Any type of myocardial infarction requires ECG for accurate diagnosis. There is a possibility of early detection of heart function deterioration through the project, which most sure allows to prevent myocardial infarction.

The causes of myocardial infarction

The main cause of myocardial infarction is impaired coronary arteries circulation. The main factors of this disease are:

  1. coronarothrombosis (acute occlusion of the artery lumen), which often leads to macrofocal (transmural) necrosis of the cardiac walls;
  2. coronary stenosis (acute narrowing of artery opening by atherosclerotic plaque, thrombus), which usually result in macrofocal myocardial infarction;
  3. constrictive coronary stenosis (acute narrowing of several coronary arteries), which leads to microinfarctions, mainly subendocardial myocardial infarction.

In most cases, myocardial infarction is formed on the background of atherosclerosis, hypertension and diabetes. Smoking, also inactive lifestyle and obesity, strongly contribute to the development of myocardial infarction.
Myocardial infarction can be provoked by the increased myocardial oxygen demand states:

Cooling can initiate the beginning of pathological changes, so the seasonality in the occurrence of myocardial infarction is observed: most often in winter months with low temperatures, most rare – in summer.

Extremely hot weather although can also contribute to development of the pathology. Myocardial infarction cases are increased after flu epidemics.

Classification of myocardial infarction

There are several classifications of myocardial infarction:

The main method of myocardial infarction detection is electrocardiogram. Cardiac electrical impulses are recorded on the body surface by ECG machine electrodes. There are six standard leads (I, II, III, avR, avL, avF), which are registered from the electrodes on the limbs. They are enough to register pathologies. Physicians uses 12 standard leads (additional chest leads V1-V6) for more detailed analysis of heart. Cardiovisor, used by ordinary individuals (not doctors), registers 6 standard leads.  CardioVisor’s information from these leads is enough to make conclusion. Another (12-lead) modification of the instrument is mainly used by cardiologists, which require more detailed cardiac functions with the chest leads besides CardioVisor’s indicators.

There are major symptoms of myocardial infarction. Let us analyze the images. The first one shows electrocardiogram of normally functioning heart.

Нормально функционирующее сердце



The second one shows the main features of ECG myocardial infarction.

Основные признаки инфаркта миокарда



There are two types of myocardial infarction depending on the area affected:

1. Macrofocal infarction, transmural (necrosis, infarction, expanding to all the layers), Q-infarction. This type ECG is shown here:

Крупноочаговый инфаркт


  A - electrode records the tooth Q,
  B - electrode aimed for wave R registration).

Measuring the amplitude of R and Q waves, we can determine the degree of heart disease in the infarction area. There is a division of macrofocal myocardial infarction into transmural myocardial infarction (in this case, R wave will be absent) and subepicardial myocardial infarction. Transmural myocardial infarction is characterized by QS complex registration in one of the following leads: aVL, I, II, III, aVF, or QR (if Q is exceeds 0.03 seconds and the Q/R exceeds 1/3 R wave in II, III, aVF .)

2. Microfocal infarction (non Q-infarction).
There are two types of microfocal infarction. The first type is subendocardial infarction (heart necrosis areas adjacent to the endocardium) (Fig. 4).

Мелкоочаговый инфаркт


The main ECG sign of subendocardial infarction is the ST shift below the isoelectric line, with no recorded abnormal Q wave in aVL and I leads.

The second type of microfocal infarction – the intramural (necrosis infarction, but the endocardium and epicardium are not impaired).

интрамуральный инфаркт



Macrofocal infarction is a multistage process and includes the following steps:

1. Extra-acute – it lasts since few minutes up several hours of ischemia before necrosis development. There is an unstable blood pressure. Pain is possible, also hypertension, sometimes low blood pressure. There is high probability of ventricular fibrillation.

2. Acute – the period when the final part of necrosis, also inflammation of surrounding tissue, and scar are formed. It lasts since 2 hours up to 10 days (it lasts longer if protracted and recurrent course). Hemodynamic impairment may manifest itself as decreased blood pressure (mostly systolic), and can be terminated by pulmonary edema or cardiogenic shock development. Worsen hemodynamic may cause decreased cerebral circulation, which can manifest as neurological symptoms, in elderly can lead to mental disorders.

Cardiac rupture is possible during the first days of myocardial infarction. In patients with multivessel stenosing coronary artery lesion early post-infarction angina may occur. During this period, the electrocardiogram will look like this:

Острый период


Using Project and CardioVisor device during the first days of acute myocardial infarction may serve as extra characteristic of the disease, which will allow to the doctor to assess pathology degree and assign the appropriate treatment.

3. Subacute – is a period when there is a final scar formation, and necrotic tissue is replaced with the granular one. This durate up to 4-5-th week after the onset of the disease.
Postinfarction syndrome (pericarditis, pleurisy, pneumonia) can develop after the second and sixth weeks of the disease. During this period, the electrocardiogram will be seen as follows:

Подострый период


Scarring period – since two weeks up to two or three years. Postinfarction period – is the period when scar is completely formed and indurated, and the heart is accommodated to new functioning conditions. During this period, the electrocardiogram may look like this:

Период рубцевания


To determine the localization of myocardial infarction, it is necessary to pay attention which lead records specific changes:

  1. Anterior septum myocardial infarction – I, aVL, V1, V2, V3;
  2. Anterior septum – apical – I, aVL, V1, V2, V3, V4;
  3. Anterior septum - -apical-lateral – I, aVL, V1, V2, V3, V4, V5, V6;
  4. Lower - II, III, aVF;
  5. Inferolateral – II, III, aVF, V5, V6.


Risk of myocardial infarction

Myocardial infarction is dangerous for its complications. These include:

  1. acute heart failure (cardiogenic shock, pulmonary edema);
  2. cardiac rupture;
  3. ventricular fibrillation, asystole;
  4. cardiac arrhythmias (ventricular tachycardia, dysfunction / weak sinus syndrome);
  5. left ventricular aneurysm;
  6. intracardiac thrombosis;
  7. complications after treatment: gastrointestinal ulcers and bleeding, hemorrhagic stroke, hypertension.

The most dangerous complication of myocardial infarction is acute heart failure, which can be fatal.

It is very important to diagnose myocardial infarction early, as about half of the cases are terminated by death in few hours. Nevertheless, only during first six hours it is possible to limit the cardiac necrosis area and reduce the risk of complications.

The project provides monitoring of the heart, based on modern methods of ECG analysis – dispersion mapping. The method of dispersion mapping, if compared to standard ECG, reflects the changes in the earlier stages of heart blood supply disorders, which allows the earliest detection of heart problems, also prevention of myocardial infarction.
Myocardial infarction patients have high degree of recurrence. The project also assists to manage the patients with this problem: the possibility of relapse due to early detection of early deterioration several times reduces, provided that they use the service.

View all articles