Ischemic heart disease

coronary

Importance and functions

The heart, like the other organs of the human body, needs the right doses of oxygen and nutrients to function properly and live. The supply of these substances is ensured by the presence of a dense network of vessels, which together form the coronary system.

The coronary circulation, as well as that of the whole organism, is composed of veins and arteries that surround the surface of the heart like a crown (hence the term coronary). The arteries, rich in arterial blood, supply the sprayed tissues with oxygen and nutrients while the veins carry the wastewater from the heart to the right atrium, where it is first sent to the right ventricle and then to the lungs to be purified.

At the level of the heart, all the blood vessels are divided from the beginning into two distinct systems. The first, called the left coronary system, mainly supplies the left side of the heart with blood. The second, called the right coronary system, instead deals with spraying the right side.

Both of these systems originate from the root of the aorta, through two large arterial vessels called the right coronary artery and the left cornoaria artery respectively. These vessels are then divided into smaller and smaller branches until they reach the innermost parts of the heart.

At rest the heart's oxygen consumption is high, much higher than that of other organs and tissues. The myocardium is in fact particularly skilled in extracting oxygen from the blood that irrigates it.

The muscle tissue of the heart (myocardium) is in fact striated like that of the other skeletal muscles but has some peculiar differences. In resting conditions the heart is characterized by:

widespread capillary density (about 3-4 times higher than skeletal muscle). Every single cell of the myocardium is in fact fed by at least one capillary
high blood flow, about 20 times higher than skeletal muscle (60-80 ml / min. every 100 g of tissue)
very high oxygen consumption (7-9 ml / min. per 100 g of tissue versus 0.15 ml / min. per 100 g of skeletal muscle tissue)
high oxygen extraction (arterio-venous difference of O ₂ 10 ml / 100 against 5 ml / 100 ml of skeletal muscle)

However, compared to the other muscles of the body, the heart has a limited capacity to draw energy from anaerobic processes.

Considering that the extraction of oxygen is already high at rest, when energy demands increase in the heart there is nothing left to do but increase the flow of blood in the coronary system. The myocardium is therefore able to regulate blood flow according to its metabolic needs.

In particular the coronary system can increase the blood supply to the heart up to five times to cope with increased energy demands (during maximal exercise the blood flow in the coronary arteries can reach the value of 1L / min).

Definition

Ischemic heart disease is also known as myocardial ischemia .

CARDIOPATHY: heart disease;
ISCHEMIA: decrease or suppression of blood supply in a specific body district;

The tissues affected by ischemia are in a situation characterized by:

reduced oxygen supply (hypoxia, anoxia)
reduced availability of nutrients
reduced elimination of waste substances

This situation results in a state of tissue suffering that can seriously affect the functionality of the affected organs.

The term ischemic heart disease contains a spectrum of pathological conditions accumulated by a discrepancy between consumption and oxygen supply to the myocardium ; in those who suffer from it the heart requires more oxygen than the coronary arteries can guarantee, consequently the heart enters a state of suffering (hypoxic state).

Consequences

Ischemia can occur in the presence of an increase in myocardial oxygen demand and / or a reduction in coronary flow.

In any case, an imbalance is created between the need and availability of oxygen and nutrients. This deficit may be temporary or permanent and in the latter case the most serious damage occurs.

The consequences of cardiac ischemia depend on:

importance of the occluded vessel: the greater the area of cardiac tissue supplied by that vessel, the greater the ischemic damage;
duration of occlusion;
perfusion by a collateral circle: if a cell is perfused by more than one capillary, an auxiliary vessel could guarantee its survival even when the main one is occluded;
metabolic and functional state of the myocardium before blood flow interruption.

Causes

At the origin of ischemic heart disease there can be numerous pathologies, all linked by the reduction of the blood supply to the heart. Among these the most common forms of clinical manifestation are:

Chronic coronary syndromes:
- chronic or stressful angina
Acute coronary syndromes:

unstable angina
myocardial infarction without ST elevation
myocardial infarction with ST elevation
heart failure
unexpected death
silent ischemia

The main cause of ischemic heart disease is atherosclerotic disease of the coronary arteries

Role of Atherosclerosis

Atherosclerosis is a degenerative disease that favors the deposit of fat aggregates and other substances in the inner wall of the arteries. These deposits decrease the vessel lumen and the elasticity of the walls. Forced to pass in a rigid vessel of restricted caliber, the blood undergoes an increase in pressure putting the integrity of the artery at risk.

The shrinkage, when it becomes important, alters the normal circulation as it favors the formation of thrombus that can be detached from the arteriosclerotic plaque and go to obstruct smaller caliber vessels. The same thrombus, in addition to directly narrowing the vessel, also does so indirectly favoring the synthesis of thromboxane, a powerful vasoconstrictor.

Within the coronary arteries, when the obstruction reaches 50%, serious problems begin to appear, given that the vessel is no longer able to completely satisfy the metabolic demands of the sprayed cells.

Local ischemia alters the electrical behavior of the entire heart generating arrhythmias that can seriously jeopardize the efficiency of the heart pump. At the same time, the reduced flow of blood and oxygen decreases the cardiac contraction force by reflex mechanism, further aggravating the situation.

Complications

The severity and duration of ischemia determine whether or not the cardiac damage is reversible.

If the ischemia lasts over time, the cardiac cell can withstand for about 20-360 minutes the lack of oxygen and nutrients, after which it dies. Cell necrosis is called heart attack and, if it involves an important number of cells, it can be fatal for the individual.

Once dead these cells no longer regain their functionality, but are replaced by electrically and mechanically inert fibrous scar tissue.

Angina, on the other hand, is a transient myocardial ischemia with reversibility. It is defined:

stable if it is associated with constant physical effort and does not undergo significant changes over time,
unstable if it is of recent onset, worsening and also appears at rest.

Primary prevention

Behavioral Measures

Primary prevention or prophylaxis aims to avoid the onset of ischemic heart disease.

It is based on the identification and correction of the main risk factors:

Smoke
Diabetes mellitus
dyslipidemia
Hypertension
sedentary
Obesity
Estrogen replacement therapy: to be avoided in menopausal women who have had a heart attack
Hyperhomocysteinemia

drugs

Aspirin and antiplatelet drugs in general in high-risk patients:

Reduce the incidence of acute cardiac ischemic events
To be used for prevention especially in patients with multiple risk factors

Beta blockers, ACE inhibitors

They help to control hypertension (ACE inhibitors) and to normalize heart rate

Treatment and prophylaxis

If Ischemic Heart Disease has already manifested, there are drugs that can control the progression of the disease and reduce the risk of new serious ischemic episodes: