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Myocardial infarction (MI) refers to tissue death of the heart muscle caused by ischemia, the lack of oxygen delivery to myocardial tissue. It is a type of acute coronary syndrome , which describes a sudden or short-term change in symptoms related to blood flow to the heart. [ 22 ]
Reduced blood flow to the heart associated with coronary ischemia can result in inadequate oxygen supply to the heart muscle. [6] When oxygen supply to the heart is unable to keep up with oxygen demand from the muscle, the result is the characteristic symptoms of coronary ischemia, the most common of which is chest pain. [6]
Hypoxemia is usually defined in terms of reduced partial pressure of oxygen (mm Hg) in arterial blood, but also in terms of reduced content of oxygen (ml oxygen per dl blood) or percentage saturation of hemoglobin (the oxygen-binding protein within red blood cells) with oxygen, which is either found singly or in combination. [2] [5]
Hypoxemic hypoxia is a lack of oxygen caused by low oxygen tension in the arterial blood, due to the inability of the lungs to sufficiently oxygenate the blood. Causes include hypoventilation, impaired alveolar diffusion, and pulmonary shunting. [8] This definition overlaps considerably with that of hypoxic hypoxia.
The word infarction means that some area of tissue has died due to a lack of blood flow, and therefore a lack of oxygen. “Myo” refers to the muscle, and “cardial” refers to the heart tissue. So with a heart attack, or MI, you have death of heart muscle cells because of a lack in blood flow, a process called necrosis.
Venous oxygen saturation (SvO 2) is the percentage of oxygenated hemoglobin returning to the right side of the heart. It can be measured to see if oxygen delivery meets the tissues' demands. SvO 2 typically varies between 60% and 80%. [9] A lower value indicates that the body is in lack of oxygen, and ischemic diseases occur.
There is a relationship between severity of angina and degree of oxygen deprivation in the heart muscle. However, the severity of angina does not always match the degree of oxygen deprivation to the heart or the risk of a heart attack (myocardial infarction). Some people may experience severe pain even though there is little risk of a heart ...
Symptoms include chest pain or angina, shortness of breath, and fatigue. [6]A completely blocked coronary artery will cause a heart attack. [6] Common heart attack symptoms include chest pain or angina, pain or discomfort that spreads to the shoulder, arm, back, neck jaw, teeth or the upper belly, cold sweats, fatigue, heartburn, nausea, shortness of breath, or lightheadedness.