heart failure’s used to describe a pointat which the heart can’t supply enough blood to meet the body’s demands. this can happenin two ways, either the heart’s ventricles can’t pump blood hard enough during systole,called systolic heart failure, or not enough blood fills the ventricles during diastole,called diastolic heart failure. in both cases, blood backs up into the lungs, causing congestionor fluid buildup, which is why it’s also often known as congestive heart failure, orjust chf. congestive heart failure affects millions of people around the world and sinceit means that the body’s needs are not being met, it can ultimately lead to death. partof the reason why so many people are affected by heart failure, is that there are a widevariety of heart diseases like ischemia and
valvular disease that can impair the heart’sability to pump out blood and—over time—can ultimately cause the heart to fail. alright, first up is systolic heart failure,kind of a mathematical way to think this one is that the heart needs to squeeze out a certainvolume of blood each minute, called cardiac output, which can be rephrased as the heartrate (or the number of beats in a minute) multiplied by the stroke volume (the volumeof blood squeezed out with each heart beat). the heart rate is pretty intuitive, but thestroke volume’s a little tricky. for example, in an adult the heart might beat 70 timesper minute and the the left ventricle might squeeze out 70ml per beat, so 70 x 70 equalsa cardiac output of 4900 ml per minute, which
is almost 5 liters per minute. so notice thatnot all the blood was pumped out right? and the stroke volume is a fraction of the totalvolume. the total volume may be closer to 110 ml, and 70ml is the fraction that gotejected out with each beat, the other 40ml kind of lingers in the left ventricle untilthe next beat, right? in this example, the ejection fraction would be 70ml divided by110 ml or about 64%, a normal ejection fraction is around 50-70%, between 40-50% would beborderline, and anything about 40% or less would indicate systolic heart failure becausethe heart is only squeezing out a little blood each beat. so in our example, if the totalvolume of the left ventricle was 110 ml, but only 44 ml was pumped out with each beat (thenyou have 44 ml divided by 110 ml which is
40%), and we would say that this person isin systolic heart failure. now in addition to systolic heart failure,you’ve also got diastolic heart failure, which is where the heart’s squeezing hardenough but not filling quite enough. in this case again the stroke volume is low, but theejection fraction’s normal...how’s that? well it’s not filling enough so there’sa low total volume, say about 69 ml, well even though both are low, 44 ml divided by69 ml is still 64%. in this situation, the failure’s caused by abnormal filling ofthe ventricle so that the chamber doesn’t get fully loaded or stretched out in the firstplace. another term for this is having a reduced “preload†which is the volume of bloodthat’s in the ventricle right before the
ventricular muscle contracts. an important relationship between systolicand diastolic function is the frank-starling mechanism, which basically shows that loadingup the ventricle with blood during diastole and stretching out the cardiac muscle makesit contract with more force, which increases stroke volume during systole. this is kindalike how stretching out a rubber band makes it snap back even harder, except that cardiacmuscle is actively contracting whereas the rubber band is passively going back to itsrelaxed state. heart failure can affect the right ventricle,or the left ventricle, or both ventricles, so someone might have, right-sided heart failure,left-sided heart failure, or both (which is
called biventricular heart failure), eachof which can have systolic or diastolic failure. having said that, if less blood exits eitherventricle it’ll affect the other since they work in series, so left-sided could causeright-sided, and vice versa, so these terms really refer to the primary problem affectingthe heart, basically which one was first. usually left-sided heart failure is causedby systolic (or pumping) dysfunction. this is typically due to some kind of damage tothe myocardium—or the heart muscle—which means it can’t contract as forcefully andpump 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 throughthe coronary artery to the heart tissue, which
damages the myocardium. sometimes, if thecoronary’s blocked completely and the person has a heart attack, they might be left withscar tissue that doesn’t contract at all, which again means the heart can’t contractas forcefully. longstanding hypertension is another common cause of heart failure. thisis because as arterial pressure increases in the systemic circulation, it gets harderfor the left ventricle to pump blood out into that hypertensive systemic circulation. tocompensate, the left ventricle actually bulks up, and its muscles hypertrophy, or grow sothat the ventricle can contract with more force. the increase in muscle mass also meansthat there is a greater demand for oxygen, and, to make things even worse, the coronariesget squeezed down by the this extra muscle
so that even less blood’s delivered to thetissue. more demand and reduced supply means that some of the ventricular muscle startshave weaker contractions—leading to systolic failure. another potential cause would bedilated cardiomyopathy, where the heart chamber dilates, or grows in size in an attempt tofill up the ventricle with larger and larger volumes of blood, or preload, and stretchout the muscle walls and increase contraction strength, via the frank-starling mechanism.even though this can work for a little while, over time, the muscle walls get thinner andweaker, eventually leading to muscles that are so thinned out that it causes systolicleft-sided heart failure. ultimately the ventricle walls need to be the right size relative tothe size of the chamber in order for the heart
to work effectively. any major deviation fromthat can lead to heart failure. even though systolic failure is most commonin left-sided heart failure, diastolic heart failure or filling dysfunction can also happen.in hypertension, remember how the left ventricular hypertrophied? well that hypertrophy is concentric,which means that the new sarcomeres are generated in parallel with existing ones. this meansthat as the heart muscle wall enlarges, it crowds into the ventricular chamber space,resulting in less room for blood, meaning that in addition to contributing to systolicdysfunction, hypertension also can cause diastolic heart failure. concentric hypertrophy leadingto diastolic failure can also be caused by aortic stenosis, which is a narrowing of theaortic valve opening, as well by hypertrophic
cardiomyopathy, an abnormal ventricular wallthickening often from a genetic cause. restrictive cardiomyopathies are yet another cause. inthis case the heart muscle gets stiffer and less compliant, and therefore the left ventriclecan’t easily stretch out and fill with as much blood, which leads to diastolic heartfailure. when the heart doesn’t pump out as muchblood, there’s decreased blood flow to the kidneys, which activates the renin-angiotensin-aldosteronesystem, ultimately causing fluid retention. which fills the heart a bit more during diastoleand increases preload, which increases contraction strength again by the frank starling mechanism.unfortunately, just like the other strategies, in the long term, retaining fluid so thatmore fluid remains in the blood vessels typically
leads to a large portion of it leaking intothe tissues and can contribute to fluid buildup in the lungs and other parts of the body,which can worsen the symptoms of heart failure. aright so a major, major clinical sign ofthe heart not being able to pump enough blood forward to the body, is that blood startsto back up into the lungs. a backup of blood in the pulmonary veins and capillary bedscan increase the pressure in the pulmonary artery and can also result in fluid movingfrom the blood vessels to the interstitial space causing pulmonary edema, or congestion.in the alveoli of the lungs, all this extra fluid makes oxygen and carbon dioxide exchangea lot harder, since a wider layer of fluid takes more time for oxygen and carbon dioxideto diffuse through, and therefore patients
have dyspnea—trouble breathing, as wellas orthopnea - which is difficulty breathing when lying down flat since that allows venousblood to more easily flow back from the legs and the gut to the heart and eventually intothe pulmonary circulation. this extra fluid in the lungs causes crackles or rales to beheard on auscultation while the patient breathes. if enough fluid fills some of these capillariesin the lungs, they can rupture, leaking blood into the alveoli. alveolar macrophages theneat up these red blood cells, which causes them to take on this brownish color from ironbuild-up. and then they’re then called “hemosiderin-laden macrophagesâ€, also known as “heart failurecellsâ€. for left-sided heart failure, certain medicationscan be prescribed to help improve blood flow,
like ace inhibitors which help dilate bloodvessels, as well as diuretics to help reduce the overall fluid buildup in the body whichhelps prevent hypertension from worsening the heart failure. now let’s switch gears and think about right-sidedheart failure, which is actually often caused by left-sided heart failure. k remember howfluid buildup increased pressure in the pulmonary artery? well this increased pulmonary bloodpressure makes it harder for the right side to pump blood into. in this case the heartfailure would be biventricular, since both ventricles are affected. someone can alsohave isolated right-sided heart failure, though, and an example of this would be a left-to-rightcardiac shunt. in these cases, there might
be a cardiac shunt like an atrial septal defector a ventricular septal defect, that allows blood to flow from the higher-pressure leftside to the lower-pressure right side, which increases fluid volume on the right side andcan eventually lead to concentric hypertrophy of the right ventricle, making it more proneto ischemia—which is a systolic dysfunction, and have a smaller volume and become lesscompliant—which is a diastolic dysfunction. another potential cause of isolated right-sidedfailure is chronic lung disease. lung diseases often make it harder to exchange oxygen, right?well in response to low oxygen levels, or hypoxia, the pulmonary arterioles constrict,which raises the pulmonary blood pressure. this, just like before, makes it harder forthe right side of the heart to pump against
and can lead to right-sided hypertrophy andheart failure. when chronic lung disease leads to right-sided hypertrophy and failure, it’sknown as cor pulmonale. with left-sided failure, blood gets backedup into the lungs. with right-sided failure, blood gets backed up to the body, and so patientshave congestion in the veins of the systemic circulation. one common manifestation of thisis jugular venous distention, where the jugular vein that brings blood back to the heart takeson more blood and becomes enlarged and distended in the neck. also in the body, when bloodbacks up to the liver and spleen, fluid can move into the interstitial spaces within thoseorgans and they can both become enlarged, called hepatosplenomegaly, which can be painful,and if the liver is congested for long periods
of time, patients can eventually develop cirrhosisand liver failure, which would be called cardiac cirrhosis. excess interstitial fluid nearthe surface of the liver and spleen can also move right out into the peritoneal space aswell, and since that cavity can take a lot of fluid before there is any increase in pressure,a lot of fluid can build up in the peritoneal space which is called ascites. finally, fluidthat backs up into the interstitial space in the soft tissues in the legs causes pittingedema, where the tissue is visibly swollen and when you apply pressure to it it leavesa “pit†and takes awhile to come back to its original place. this generally affectsthe legs in most people, because gravity generally causes the majority of fluid to “poolâ€in the dependent parts of the body, which
is the legs when you’re standing and thesacrum, essentially the lower back, when you’re lying down. right-sided heart failure will be treatedsimilarly to left-sided heart failure, especially because it’s often a result of left-sidedheart failure. therefore, medications like ace inhibitors and diuretics may be prescribed. with heart failure, we saw that sometimesthe muscle wall can stretch and thin out, or sometimes it can sometimes thicken andbecome ischemic. in either case, those heart cells get irritated, in both scenarios thecells get irritated, and this can lead to heart arrhythmias. with an arrhythmia, theventricles don’t contract in sync anymore
making them less able to pump out blood andworsening the whole situation. in some cases, patients might be treated with cardiac resynchronizationtherapy pacemakers, which can stimulate the ventricles to contract at the same time andpotentially improve the blood pumped out. alternatively, for heart failure in general,some people might have ventricular assist devices implanted, or vads, which literallyassist or help the heart pump blood may also be implanted. in end-stage situations whereother forms of treatment have failed, patients might have a heart transplant.
