Lecture 30 Flashcards
what are the Possible Consequences of High Systolic BP?
Aneurysm
Myocardial ischemia
define Aneurysm
rupture of wall of aorta; anywhere along aorta
what are the two different types of aortic aneurysms
Abdominal aortic aneurysm (AAA)
aortic dissection
are aneurysms common in young people
Not typical in young people unless you have a genetic predisposition (Marfan Syndrome - connective tissue disorder)
what is Abdominal aortic aneurysm (AAA)
occurs in the part of the aorta that passes through the abdomen
develop slowly over time
what is an aortic dissection
when there is a tear in the inner lining of the aorta
When this tear occurs, blood can flow between the layers of the aortic wall, causing the layers to separate or dissect.
Abdominal aorta aneurysm is more common with…
age (>60)
men more likely than women (4:1)
why is it despite men being more likely to develop abdominal aorta aneurysms, women are more likely to die from them
growth is faster in women
because women have smaller aortas (3cm is a greater percentage; women’s disease progression is at a further state)
is myocardial infarction and myocardial ischemia the same thing
Myocardial ischemia refers to a lack of blood flow and oxygen to the heart muscle. This can occur when there is a partial blockage or narrowing of the coronary arteries that supply blood to the heart, which can cause chest pain or discomfort (angina) and other symptoms.
Myocardial infarction, on the other hand, occurs when there is a complete blockage of one or more coronary arteries, which leads to the death of heart muscle cells due to a lack of blood flow and oxygen. Myocardial infarction is a type of acute myocardial ischemia and is a medical emergency that requires prompt treatment to minimize damage to the heart muscle and improve outcomes.
In summary, myocardial ischemia is a condition that can lead to a heart attack (myocardial infarction) if left untreated. While they share similarities, the two conditions are distinct entities with different causes, symptoms, and treatments.
what is Myocardial ischemia/infarction
Low blood flow to the muscle tissue of your heart
Cardiac workload is too high and oxygen demand is not met
how does the heart maintain cardiac output when aortic pressure is elevated
the left ventricle must contract harder; this increases oxygen demand by the myocytes
When MAP (mean arterial/aortic pressure) increases, SV immediately decreases (harder to pump into an area with high pressure). Why?
due to increased afterload on the heart.
Afterload is the resistance that the heart must overcome to eject blood from the left ventricle into the systemic circulation.
When MAP increases, there is an increase in the pressure within the aorta and other systemic arteries. This higher pressure increases the afterload that the left ventricle must overcome to eject blood during systole. As a result, the left ventricle has to work harder to pump blood into the high-pressure arterial system, which reduces the amount of blood that is ejected with each contraction (i.e., stroke volume).
This relationship between afterload and stroke volume is known as the Frank-Starling mechanism. According to this mechanism, as afterload increases, the myocardial fibers stretch less during diastole, which reduces their contractile force during systole. This results in a decrease in stroke volume. Conversely, when afterload decreases, the myocardial fibers stretch more during diastole, resulting in an increase in contractile force during systole and an increase in stroke volume.
Therefore, when MAP increases, there is a decrease in stroke volume due to the increased afterload on the heart. This can lead to a decrease in cardiac output and a reduced ability of the body to meet its metabolic demands.
Consequences of increased MAP to the Heart
Immediate decrease in SV
Coronary blood flow decreases
Lower oxygen delivery
Causes oxygen deprivation to cardiac myocytes
how does the heart compensate for increased MAP to the Heart
LV increases contraction (by hormones like epi/adrenaline that increase contractility of the heart)
Maintains the SV (don’t want to be a permanent adaptation because it will lead to a pathophysiological condition)
O2 demand is higher
The coronary blood flow will decrease due to longer systole vs. diastole
Causes O2 deprivation to cardiac myocytes
why does coronary blood flow decrease during systole when LV is contracting.
because the cardiac myocytes are squeezing the coronary artery, preventing blood flow (pressure in LV > pressure in coronary artery)
Whereas at diastole, the myocytes are relaxed, so it is easier for the blood to travel
There is an increase in flow during systole because the coronary pressure exceeds the pressure of the myocytes
High ventricular pressure during systole actually compresses the arteries, reducing coronary blood flow temporarily
Because of the period of low flow of blood, there is a development of metabolites and CO2 in the tissue which cause an increase in blood flow to the tissues during diastole
