Acute myocardial infarction is caused by permanent and usually sudden ischemia, ie, blockage of blood flow in a particular area of the heart muscle.
The heart attack can occur in different organs and tissues, for example:
- Lung (rare),
- Bowel ,
Causes of acute myocardial infarction
The cause of myocardial infarction is the reduction of blood flow to a part of the heart due to:
- A thrombus in at least one coronary artery,
- A spasm in the coronary arteries, or narrowing of the artery.
Risk factors for acute myocardial infarction
Family history of heart attack;
- Smoke ;
- Chronic alcoholism;
- Lack of physical exercise;
- High blood pressure (or hypertension);
- Night work (night shift people are more likely to have a myocardial infarction);
- According to a study by Lawrence J. Appel, MD, MPH and Al. (Effects of Protein, Monounsaturated Fat, and Carbohydrate Intake on Blood Pressure and Serum Lipids) in which blood pressure and LDL cholesterol were measured, the risk of Coronary heart disease is lower in a diet rich in proteins (50% of plant origin) or in unsaturated fats (mainly monounsaturated) compared to a diet rich in carbohydrates.
If the patient is not aware of the initial symptoms, the risk of damage to the heart muscle increases, partially or completely.
Infarct risk factors
Factors that influence the development of a heart attack
- Occlusion development speed – If the occlusion of the artery develops slowly, the body has the time and the possibility of creating a collateral or parallel circulation.
Thus, when arterial occlusion occurs, the size of the infarction is smaller because the blood circulates in the collaterally closed arteries.
- The oxygen content in the blood is important because the anemia is characterized by a decrease in the concentration of hemoglobin (and oxygen) in the blood and gives the same symptoms of hypoxia. Thus, a person suffering from anemia is at great risk because the body is already deficient in oxygen.
Symptoms of myocardial infarction
The symptoms are different from one person to another.
Pain in myocardial infarction
Generally, the person has chest pain (tightening type) and radiation to the left arm.
However, in the case of occlusion of the right coronary the pain feels:
- In the throat,
- In the mouth of the stomach (epigastrium), it is sometimes confused with indigestion .
This artery runs at the level of the lower wall of the heart and is in contact with the diaphragm at the level of the esophageal hiatus (where the esophagus penetrates the diaphragm).
It is an atypical pain, with a vague symptomatology and a location that is not always precise, with different degrees of pain, depending on the involved areas, in addition it is perceived differently by women and men.
Hence, infarctions are not often recognized or abdominal irradiation is mistaken for abdominal colic .
That is why the electrocardiogram is not enough for the diagnosis, but also some laboratory tests are necessary.
The cardiac dysfunction is a reduced ability to pump blood from the heart.
The consequence is a reduction in cardiac output.
You may also have a sudden death due to rupture of the heart.
In addition, it has been observed that the symptoms in women are very different from those in men. The patient’s clinical condition may include the following frequent symptoms:
- Chest pain : You may feel discomfort, pressure, tightness in the chest or stitches in the center of the chest that last for more than a few minutes.
The discomfort can come and go at intervals.
- Pain in the upper body : Pain or generalized malaise may occur on the shoulder , arm (inner part up to the little finger), spine , neck , teeth or jaw .
There may be pain in the upper body without discomfort in the chest.
Ischemic heart pain is very characteristic and in most cases follows the T1 dermatome (skin region innervated by the nerve root that originates from the spinal cord at the level of the first dorsal vertebra).
However, the non-rare areas of irradiation are the mandible, epigastrium, anterior and inferior neck ,the region between the shoulder blades and the right arm. This also depends on the damaged heart region.
Pain is typical when it is oppressive or tight, but in some cases it can be burning or a weight. It is typically characterized by a gradual onset and cessation (unlike aortic dissection) and, importantly, is not influenced by breathing, body position and pressure in the chest wall.
Often there are triggering factors like emotional stress, low temperatures, exercise, sexual intercourse, hypertensive crisis or lunch. It may also arise at rest or at night while sleeping.
Typically, angina pectoris lasts only a few minutes (1-2 minutes to 5-10 minutes). However, in the most severe forms, the duration can reach up to 20 or 30 minutes.
- Pain in the stomach : The pain may extend down into the belly and you may feel heartburn .
- Anxiety : You may feel a sense of distress, such as a panic attack without an apparent reason.
- Sweating : Suddenly you can sweat cold.
- Nausea and vomiting : You may experience stomach pain or nausea.
However, women have different symptoms than men. In addition to pain or discomfort, you may experience the following symptoms:
Pain in the spine, neck, jaw, shoulder or abdomen;
- Shortness of breath ;
- Nausea or vomiting;
- Abdominal pain;
- Dizziness or dizziness;
- Unusual or unexplained fatigue .
Silent myocardial infarction is different from the classic because it does not cause chest pain and tightness in the chest, but there are other symptoms (eg sweating, nausea, jaw pain, etc.).
People with diabetes may have an asymptomatic or silent heart attack , they do not realize this event.
Consequences and risk of myocardial infarction
Damaged cardiac tissue drives the electrical impulses more slowly than normal. This difference in the speed of conduction of the impulses can trigger an arrhythmia that in some people is the final cause of death.
The most serious arrhythmia is ventricular fibrillation: a very fast and irregular heartbeat that is the main cause of sudden cardiac arrest.
Another dangerous arrhythmia is ventricular tachycardia: it usually causes an increase in heart rate that prevents the heart from pumping blood efficiently to the various parts of the body.
This can lead to a decrease in cardiac output and a dangerous drop in blood pressure that may further increase coronary ischemia and the infarction.
Arrhythmia : is present in more than 90% of patients. During the course of the infarction, bradycardia or ectopic (premature) ventricular beats may appear.
Driving disturbances may be caused by damage to:
- Nó sinoatrial,
- Nó atrioventricular,
- Specialized conductive tissue.
The arrhythmias severe within 72 hours is the leading cause of death and include:
- Frequent tachycardias that reduce cardiac output,
- Ventricular tachycardia,
- Ventricular fibrillation.
Heart failure : occurs in about 2/3 of patients admitted with acute myocardial infarction. Generally, left ventricular dysfunction predominates with:
- Dyspnea ,
- Pulp crepitations on inspiration at the base of the lung,
- Hypoxemia (reduced amount of oxygen in the blood).
Clinical signs depend on:
- Of the infarct size,
- The severity of cardiac output reduction.
Mortality depends on the severity of heart failure .
The reduced blood oxygen – usually accompanied by acute myocardial infarction is caused by the increased left atrial pressure with a ventilation / perfusion changes lung, pulmonary edema interstitial and alveolar collapse.
Low blood pressure : in acute myocardial infarction may be due to:
- Lower ventricular filling,
- Loss of contraction force caused by extensive cardiac damage.
Usually, the decreased filling of the ventricle is caused by the reduction of blood in the veins that return to the heart. It occurs especially in patients undergoing diuretic therapy, but may be the consequence of a right ventricular infarction.
The cardiogenic shock is a reduction in cardiac function characterized by:
- Low blood pressure ,
- High heart rate,
- Reduced urine production
- Excessive sweating ,
- Cold hands and feet .
It has a mortality of over 65%.
It is usually associated with an extensive anterior infarction, in which at least 40% of the left ventricular myocardium does not work.
Recurrent ischemia – Ischemia can develop quietly in about 1/3 of patients and leads to an increased risk of recurrence of heart attack.
Papillary muscle insufficiency – occurs in about 35% of patients. In addition, permanent mitral reflux may develop due to a papillary muscle scar.
Heart rupture – can occur in 3 areas:
- Papillary muscle,
- Interventricular Septo,
- Ventricular wall.
Papillary muscle rupture is usually caused by a lower posterior infarction due to an obstruction of the right coronary artery.
It produces acute and severe mitral regurgitation, usually occurring in conjunction with pulmonary edema.
The wall rupture is more common in females and is characterized by sudden drop in blood pressure and fluid accumulation in the pericardial.
And almost always deadly.
Ventricular aneurysm : is frequent, especially in the case of transmural infarction (usually anterior) with a portion of the residual myocardium that works.
The aneurysm can develop in a few days, weeks or months.
This does not break, but can cause:
- Recurrent ventricular arrhythmias,
- Reduction of cardiac output.
Another complication of ventricular aneurysm includes wall thrombi and systemic embolization.
Mural thrombosis : occurs in about 20% of patients with acute myocardial infarction (60% of patients with extensive anterior infarction).
10% of patients with left ventricular thrombosis develop at least one plunger.
The risk is higher in the first 10 days but persists for at least three months.
Pericarditis : Occurs in 1/3 of patients with acute transmural infarction, 24-96 hours after infarction.
Dressler syndrome – develops in some patients several days, weeks or months after an acute myocardial infarction.
Is characterized by:
The differential diagnosis with a recurrence of heart attack can be difficult, but in this case cardiac enzymes remain normal.
Ventricular asynergy : may occur in acute myocardial infarction due to the alternation between normal and abnormal myocardium (which does not contract or where contraction is partial).
In the case of multiple infarctions, the myocardium that contracts partially is frequent.
In case of heart failure with low cardiac output and pulmonary congestion, it is called: ischemic myocardiopathy .
The consequences of heart attack
The size of the scar that is formed to repair the heart depends on the extent of the necrotic tissue.
The heart muscle cells do not reproduce, so the damage is irreversible .
The scar is a non-contractile area of myocardial tissue, so if it is too large it can cause a significant loss of the force with which the blood is pumped.
In addition, the scar is an area with less resistance, so that the urge of the blood to the ventricles can cause an outward flexion (movement out) that can cause:
- The rupture of the heart.
In the first 6 months after a heart attack it is not possible to do dental treatments.