By Dr. Stefano Casali
Definition
Spectrum of diseases with different etiology, in which the unifying pathophysiological factor is represented by an imbalance between the metabolic demand and the supply of oxygen to the myocardium.
This imbalance causes an alteration in the electrical activity and the contractile capacity of the affected areas.
Peculiar elements:
- The ischemic character of the lesion
- The segmentarity of the alterations
- The clinical expressiveness of myocardial damage
Clinical manifestations
- Primary cardiac arrest: it rapidly evolves towards sudden death, in the absence of resuscitation maneuvers or when resuscitation is ineffective.
- Angina pectoris: it is linked to a transient imbalance between myocardial demand and metabolic intake. Ischemia is reversible and does not cause permanent anatomical damage. In the non-infrequent case in which myocardial ischemia is not associated with symptoms, it is called silent ischemia.
- Myocardial infarction: it follows a protracted myocardial ischemia, which leads to irreversible cell damage or myocardial necrosis.
- Heart failure: it can manifest itself as a complication of an acute or previous infarction, or it can be precipitated by episodes of transient myocardial ischemia or arrhythmias. In cases without clinical and / or electrocardiographic signs of ischemic heart disease, the diagnosis is always presumptive.
- Arrhythmias: they may be the only sign of an ischemic heart disease. In this case the diagnosis is only presumptive, unless a reliable myocardial ischemia or coronary angiography shows an obstructive coronary artery disease.
Epidemiology
- In Italy cardiovascular diseases are the cause of 45-50% of global mortality.
- Ischemic heart disease alone is in turn responsible for 35% of deaths due to cardiovascular diseases.
- It is estimated that annual mortality for typical forms of ischemic heart disease (angina, heart attack and sudden death) is between 70, 000 and 80, 000 cases.
- In Italy, therefore, about one million people live with ischemic heart disease in its most typical forms.
Causes
Coronary atherosclerosis is by far the most frequent cause of ischemic heart disease and, from a practical point of view, it can be considered the exclusive cause.
Numerous epidemiological studies, conducted over the past twenty-five years, have enabled us to identify some individual variables that are associated with a greater risk of disease; these variables have been termed coronary risk factors.
Coronary risk factors:
Non-changeable risk factors:
- Age.
- Sex.
- Genetic factors and familiarity for CI
- Personal history of cardiovascular diseases.
Partially modifiable risk factors:
- Hypertension.
- Diabetes mellitus.
- Hypercholesterolemia.
- Low HDL cholesterol.
- Obesity.
Modifiable risk factors:
- Smoke.
- Alcohol abuse.
Myocardial metabolism
In basal conditions the heart consumes about 6.5-10 ml / min of oxygen per 100 g of tissue. This expenditure serves:
- 3-5% for electrical activity.
- 20% for the maintenance of cellular integrity.
- 72-75% for contract work.
At the myocardial level, due to the high extraction of O2 (about 70%), the only mechanism of compensation in case of increased oxygen requirement is represented by a proportional increase in coronary flow, determined by a vasodilation of the arteriolar coronary district ( resistance vessels).
The maximum capacity of vasodilation secondary to a metabolic stimulus is called Coronary Reserve.
Factors that regulate the coronary circulation
- Anatomic: (origin of the Valsalva sinuses, wall thickness of the left ventricle, presence of collateral circulation).
- Mechanics: (systemic flow rate, vascular resistance, systolic compression, myogenic reflex, blood viscosity).
- Neurogens: (Alpha receptors, Beta2 receptors, vagal action).
- Metabolic: (pO2, pH, K +, adenosine, prostaglandins).
