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Heart Failure Explained · Acedra
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Heart Failure Explained
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0:04
heart failure is used to describe a point at which the heart can't supply enough blood to meet the body's demands and this can happen in two ways either the heart's ventricles can't pump hard enough during systole called systolic heart failure or not enough blood fills into the ventricles during diastole called diastolic heart failure in both cases blood backs up into the lungs causing congestion or fluid buildup which is why it's also often known as congestive heart failure
0:33
or just chf congestive heart failure affects millions of people around the world and since it means that the body's needs aren't being met it can ultimately lead to death part of the reason why so many people are affected by heart failure is that there are a wide variety of heart diseases like ischemia and valvular disease that can impair the heart's ability to pump out blood and over time can ultimately cause the heart to fail alright so first up is systolic heart
1:01
failure kind of a mathematical way to think about this one is that the heart needs to squeeze out a certain volume of blood each minute called cardiac output which can be rephrased as the heart rate or the number of beats in a minute multiplied by the stroke volume the volume of blood squeezed out with each heartbeat the heart rate is pretty intuitive but the stroke volume is a little tricky for example an adult heart might be 70 times per minute and the left ventricle might squeeze out
1:30
70 milliliters per beat so 70 times 70 equals a cardiac output of 4 900 milliliters per minute which is almost 5 liters per minute so notice that not all the blood was pumped out right and the stroke volume is only a fraction of the total volume the total volume might be closer to 110 milliliters and 70 milliliters is the fraction that got ejected out with each beat the other 40 milliliters kind of lingers in the left ventricle until the next beat right in this example the ejection fraction
2:04
would be 70 milliliters divided by 110 milliliters or about 64 a normal ejection fraction is around 50 to 70 percent between 40 to 50 percent would be considered borderline and anything about 40 or less would indicate systolic heart failure because the heart's only squeezing out a little bit of blood each beat so in our example if the total volume of the left ventricle was 110 milliliters but only 44 milliliters was pumped out with each beat then you have 44 milliliters divided by
2:36
110 milliliters which is 40 and we would say that person is in systolic heart failure now in addition to systolic heart failure you've also got diastolic heart failure which is where the heart squeezing hard enough but not filling quite enough in this case again the stroke volume is low but the ejection fraction's normal how's that well it's not filling enough so there's a low total volume say about 69 milliliters well even though both are low 44 milliliters divided by 69 milliliters
3:10
is still 64 in this situation the failure is caused by abnormal filling of the ventricle so that the chamber doesn't get fully loaded or stretched out in the first place another term for this is having a reduced preload which is the volume of blood that's in the ventricle right before the ventricular muscle contracts an important relationship between systolic and diastolic function is the frank starling mechanism which basically shows that loading up the ventricle with blood during diastole
3:40
and stretching out the cardiac muscle makes it contract with more force which increases stroke volume during systole this is kind of like how stretching out a rubber band makes it snap back even harder except that cardiac muscle is actively contracting whereas the rubber band is passively going back to its relaxed state alright so heart failure can affect the right ventricle or the left ventricle or both ventricles so someone might have right-sided heart failure
4:07
left-sided heart failure or both which is called biventricular heart failure each of which can have systolic or diastolic failure having said that if less blood exits either ventricle it'll affect the other since they work in series so left-sided could cause right-sided and vice versa so these terms really refer to the primary problem affecting the heart basically which one was first usually left-sided heart failure is caused by systolic or pumping dysfunction and this is
4:38
typically due to some kind of damage to the myocardium or the heart muscle which means it can't contract as forcefully and pump blood as efficiently ischemic heart disease caused by coronary artery atherosclerosis or plaque buildup is the most common cause in this case less blood and oxygen gets through the coronary artery to the heart tissue which damages the myocardium sometimes the coronary is blocked completely and that person has a heart attack they might be left with scar
5:06
tissue that doesn't contract at all which again means that the heart can't contract as forcefully long-standing hypertension is another common cause of heart failure this is because as arterial pressure increases in the systemic circulation it gets harder for the left ventricle to pump blood out into that hypertensive systemic circulation to compensate the left ventricle actually bulks up and its muscles hypertrophy or grow so that the ventricle can contract with more force
5:34
the increase in muscle mass also means that there's a greater demand for oxygen and to make things even worse the coronaries get squeezed down by this extra muscle so that even less bloods deliver to the tissue more demand and reduce supply means that some of the ventricular muscles starts to have weaker contractions leading to systolic failure another potential cause would be dilated cardiomyopathy where the heart chamber dilates or grows in size in an attempt to fill up the ventricle
6:02
with larger and larger volumes of blood or preload and stretch out the muscle walls and increase contraction strength via the frank starling mechanism even though this can actually work for a little while over time the muscle walls get thinner and weaker eventually leading to muscles that are so thinned out that it causes systolic left sided heart failure ultimately the ventricular walls need to be the right size relative to the size of the chamber in order for the heart to work
6:29
effectively any major deviation from that can lead to heart failure alright even though systolic failure is most common in left-sided heart failure diastolic heart failure or filling dysfunction can also happen in hypertension remember how the left ventricle hypertrophied well that hypertrophy is concentric which means that the new sarcomeres are generated in parallel with existing ones this means that as the heart muscle wall enlarges it crowds into the ventricular chamber space
6:59
resulting in less room for blood meaning that in addition to contributing to systolic dysfunction hypertension also can cause diastolic heart failure concentric hypertrophy leading to diastolic failure can also be caused by aortic stenosis which is a narrowing of the aortic valve opening as well as by hypertrophic cardiomyopathy an abnormal ventricular wall thickening often from a genetic cause restrictive cardiomyopathies are yet another cause in this case the heart muscle gets
7:29
stiffer and less compliant and therefore the left ventricle can't easily stretch out and fill with as much blood which leads to diastolic heart failure when the heart doesn't pump out as much blood there's decreased blood flow to the kidneys which activates the renin-angiotensin aldosterone system ultimately causing fluid retention which fills the heart a bit more during diastole and increases preload which increases contraction strength again by the frank starling mechanism
7:57
unfortunately just like the other strategies in the long term retaining fluid so that more fluid remains in the blood vessels typically leads to a large portion of it leaking into the tissues and can contribute to fluid buildup in the lungs in other parts of the body which can worsen the symptoms of heart failure alright so a major major clinical sign of the heart not being able to pump enough blood forward to the body is that the blood starts to back up into the lungs
8:24
a backup of blood in the pulmonary veins in capillary beds can increase the pressure in the pulmonary artery and can also result in fluid moving from the blood vessels to the interstitial space causing pulmonary edema or congestion in the alveoli the lungs all this extra fluid makes oxygen and carbon dioxide exchange a lot harder since a wider layer of fluid takes more time for oxygen and carbon dioxide to diffuse through and therefore patients have dyspnea or trouble breathing
8:53
as well as orthopedia which is difficulty breathing when lying down flat since that allows venous blood to more easily flow back from the legs in the gut to the heart and eventually into the pulmonary circulation this extra fluid in the lungs causes crackles or rails to be heard on auscultation while the patient breathes [Music] if enough fluid fills some of these capillaries in the lungs they can actually rupture leaking blood into the alveoli alveolar macrophages then eat up these
9:26
red blood cells which causes them to take on this brownish color from iron buildup and then they're called hemosiderin-laden macrophages also known as heart failure cells for left-sided heart failure certain medications can be prescribed to help improve blood flow like ace inhibitors which help dilate blood vessels as well as diuretics to help reduce the overall fluid buildup in the body which helps prevent hypertension from worsening the heart failure now let's switch gears and think about
9:56
right-sided heart failure which is actually often caused by left-sided heart failure okay remember how fluid buildup increased the pressure in the pulmonary artery while this increased pulmonary blood pressure makes it harder for the right side to pump blood into in this case the heart failure would be biventricular since both ventricles are affected someone can also have isolated right-sided heart failure though an example of this would be a left-to-right cardiac shunt
10:24
in these cases there might be a cardiac shunt like an atrial septal defect or a ventricular septal defect that allows blood to flow from the higher pressure left side to the lower pressure right side which increases fluid volume on the right side and can eventually lead to concentric hypertrophy of the right ventricle making it more prone to ischemia which is a systolic dysfunction and have a smaller volume and become less compliant which is a diastolic dysfunction
10:51
another potential cause of isolated right-sided failure is chronic lung disease lung diseases often make it hard to exchange oxygen right well in response to low oxygen levels or hypoxia the pulmonary arterials constrict which raises the pulmonary blood pressure this just like before makes it harder for the right side of the heart to pump against and can lead to right-sided hypertrophy and heart failure when chronic lung disease leads to right-sided hypertrophy and failure
11:20
it's known as core pulmonale with left-sided failure blood gets backed up to the lungs with right-sided failure blood gets backed up to the body and so patients have congestion in the veins of the systemic circulation one common manifestation of this is jugular venous distension with a jugular vein that brings blood back to the heart takes on more blood and becomes enlarged and distended in the neck also in the body when blood backs up to the liver and the spleen
11:49
fluid can move into the interstitial spaces within those organs and they can become enlarged called hepatosplenomegaly which can be painful and if the liver is congested for long periods of time patients can eventually develop cirrhosis and liver failure which would be called cardiac cirrhosis excess interstitial fluid near the surface of the liver and spleen can also move right out into the peritoneal space as well and since that cavity can take a lot of fluid before there's any increase in
12:18
pressure a lot of fluid can build up in the peritoneal space which is called ascites finally fluid that backs up into the interstitial space of the soft tissue of the legs causes pitting edema where the tissue is visibly swollen and when you apply pressure to it it leaves a pit and takes a while to come back to its original place this generally affects the legs in most people because gravity generally causes the majority of the fluid to pool in the dependent parts of the body which
12:46
is the legs when you're standing in the sacrum essentially the lower back when you're lying down right-sided heart failure will be treated similarly to left-sided heart failure especially because it's often a result of left-sided heart failure therefore medications like ace inhibitors and diuretics might be prescribed with heart failure we saw that sometimes the muscle wall can stretch and thin out or sometimes it can thicken and become ischemic in either case those heart cells get
13:14
irritated and this can lead to heart arrhythmias with an arrhythmia the ventricles don't contract in sync anymore making them less able to pump blood out and worsening this whole situation in some cases patients might be prescribed with cardiac resynchronization therapy pacemakers which can stimulate the ventricles to contract the same time and potentially improve the blood pumped out alternatively for heart failure in general some people might have ventricular assist devices implanted or vads
13:44
which literally assist or help the heart pump blood in end stage situations though where other forms of treatment have failed patients might have a heart transplant
14:15
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