Heart failure Flashcards
what is heart failure
abnormality of cardiac structure or function leading to failure of the heart to deliver oxygen at a rate that fulfills the requirements of tissues in the body
how do you calculate the ejection fraction of the heart
amount of blood pumped out of the ventricle divided by the total amount of blood in the ventricle
what ejection fraction is considered heart failure
50%
how do cardiomyocytes resspond to an action potential
depolarization of the membrane then shortens the contractile proteins then relaxes to return to resting state
what is echocardiography
send soundwaves into the body which are reflected at the interfaces between tissue, the return time tells the depth of the reflecting surface
what is the force of muscle contraction related to
amount of cytosolic calcium
what causes the initiation of the contractile process
calcoium enters from outside the cell which triggers release from the sarcoplasmic reticulum and mitochondria stores
how is muscle relaxtion achieved after the release of calcium
removal of free calcium by Na/Ca exchangers and reuptake into SR and mitochondria
why is heart failure initially not perceived by the patient
compensatory mechanisms
3 ways the body tries to correct failure
increase sodium retention
activate RAAS (angiotensin, aldosterone)
sympathetic nerve activation
how does increased sodium retention increase BP
increases blood volume slowly
how does activating RAAS increase BP
angiotensin constricts arteries and veins
aldosterone causes sodium retention
how does activating SNS increase BP
increase heart rate
increase contractility
what happens as a result of overly increased plasma volume and constriction of veins due to compensatory mechanisms
venous return stretches the already overstretched ventricles
heart cant increase force of contraction
heart enlarges and thickens
venous presure increases causing edema
what happens as a result of overly increased constriction of arteries dur to compensatory mechanisms
increased TPR heard for heart to empty against
increased resistance to outflow more than heart can overcome
