Left-sided and Right-sided Heart Failure

00:00 In order to properly talk about heart failure, we first have to understand a bit about normal cardiac function.

00:07 The idea here is not necessarily to give you all the nuances.

00:12 That is what your future career in cardiology will be for.

00:15 Rather, it is to grasp the basic fundamental concepts We'll begin with a roughly cruel view of the cardiac chambers and valves.

00:24 The left side of the image is blue to reflect deoxygenated blood in the right heart.

00:28 Blood returns from the body to the right atrium, passing through the tricuspid valve into the right ventricle and out the pulmonic valve on its way to the lungs.

00:37 The right side of the images pink to reflect oxygenated blood in the left heart.

00:41 Blood returns from the lungs via the pulmonary veins to the left atrium.

00:45 Passing through the mitral valve into the left ventricle.

00:48 And out the aorta into the body.

00:51 OK, now let's put everything into motion.

00:54 As the Atria contract blood is pushed through the tricuspid and mitral valve to fill the ventricles, which are relaxing so that they can fill and accommodate the entering blood.

01:05 Once the ventricles have maximally filled, they then contract to push their contents out.

01:10 The tricuspid of mitral valve is closed, so there's no regurgitation flow backward and the pulmonic and aortic valves are forced open by the ventricular pressure surge.

01:20 It's a beautiful thing that happens at a rate of roughly 60 to 80 contractions per minute or more, meaning over 40 million contractions in the course of just one year and on average 2.5 billion times in a lifetime.

01:36 With each contraction squeezing out roughly just 50 cc's of blood, the average human heart will pump about 1 million barrels of blood over its lifespan or enough to fill three supertankers.

01:50 Let's just marvel at that for a second here.

01:53 OK, enough of that.

01:55 So let's discuss now the phases of the contraction so we can better understand some of the modes of heart failure.

02:01 The ventricular squeeze phase is called systole.

02:04 The ventricular dilation filling phase is called diastole.

02:09 The amount of blood in the ventricle at the peak of filling is called the end diastolic volume, while the amount of blood left in the ventricle at the end of the squeeze phase is called the end systolic volume.

02:22 Notably, the heart does not squeeze out its entire end diastolic volume with any single contraction.

02:28 The amount that it does expel during Systole is called the ejection fraction or E-f.

02:34 That volume is normally somewhere between 50 to 75% of the end diastolic volume because the heart always has a bit of reserve blood in the ventricle after each normal systolic contraction is an important point in that it gives the body a way to potentially boost cardiac output by a mechanism other than just increasing the heart rate.

02:55 That is by squeezing more vigorously while 50 to 75% is the normal range for an ejection fraction.

03:02 And if a 40 to 50% is considered borderline in terms of perfusing peripheral organs and in if less than 40% is usually inadequate.

03:13 And so that brings us to heart failure which is defined as the inability of the heart to pump enough blood to meet the demands of the body.

03:21 This is often also referred to as congestive heart failure or CHF Since as the forward flow is reduced, blood backs up into the tissues behind the failing ventricle.

03:32 With left heart failure, the blood volume and pressures back up into the lungs, leading to pulmonary edema and dyspnea or shortness of breath with right heart failure, the blood backs up into peripheral tissues leading to systemic edema.

03:48 There is a truism that the most common cause of right heart failure is left heart failure, causing right sided pressure and volume overload.

03:56 Having said that, there are conditions like pulmonary hypertension that caused right heart failure in isolation without any left ventricular failure.

04:06 OK, now you also need to know that not all heart failure is created equal.

04:12 Perhaps the easiest to understand is heartfelt cure with a reduced ejection fraction or half ref.

04:20 If the heart becomes damaged, say, by a myocardial infarction, as shown on this image on the right, the muscle mass capable of squeezing blood will be diminished and the ejection fraction will drop.

04:33 A shorthand way of saying this is system dysfunction.

04:37 Although these days F Rev is the preferred way to say it, the most common cause for a half ref heart failure with a reduced ejection fraction is ischemic heart disease.

04:48 But another important causes dilated cardiomyopathy due to genetic or toxic or infectious diseases.

04:56 Overall, mitral insufficiency is usually a secondary consequence of heart failure with reduced ejection fraction because the left ventricle dilates to try to increase cardiac output.

05:07 And by doing so, tethers open the valve and keeps it from closing.

05:12 The flip side of that coin is heart failure.

05:15 With a preserved ejection fraction or half PEMF.

05:18 In that case, you can think of the heart is becoming stiff due to interstitial fibrosis or other depositions, which will prevent complete filling during diastole.

05:30 It's these interstitial deposits that we are trying to represent with a funny looking ventricular walls, even though the heart may squeeze relatively normally.

05:40 It has, after all, a preserved ejection fraction.

05:44 It doesn't relax and fill very well.

05:46 And the result is a reduced cardiac output.

05:50 Again, a shorthand way to say this is diastolic dysfunction, although my cardiology colleagues assure me that the best way to say this is half PEMF heart failure with a preserved ejection fraction.

06:03 A variety of insults can lead to half PEMF.

06:05 Many of them associated with increased interstitial fibrosis.

06:09 These include aging, hypertension, aortic stenosis and diabetes.

06:15 Cardiac amyloid deposition is another classic way to get heart failure with a preserved ejection fraction.

06:22 So to recap, heart failure is a condition where insufficient blood is pumped to maintain the needs of the peripheral tissues.

06:32 It is not always associated with reduced ejection fraction.

06:36 Insufficient relaxation and diastolic filling can also be a cause.

06:43 symptoms of left-sided heart failure overall are going to be cough. This is due to water accumulating within the alveoli which feels like you're drowning so you're going to be coughing and it's going to be dyspnea because you do not get adequate oxygenation when the alveoli are half filled with water as opposed to air. And it really makes no difference whether it's diastolic or systolic dysfunction. Those are going to be the major signs or symptoms that the patient is going to report. With chronic disease, we may progress beyond this. So they will have orthopnea. They will have a redistribution of peripheral edema particularly in right heart failure. That will then give rise to fluid that accumulates in the lungs when they are lying supine. Patients may also have paroxysmal nocturnal dyspnea, a major redistribution of fluid during sleep from peripheral edema that gives rise to profound symptoms of shortness of breath. Patients will describe that they woke up, were gasping for breath, had to go to a window and throw it open. That's paroxysmal nocturnal dyspnea or dyspnea at rest. So those are all signs of heart failure. With systolic dysfunction or diastolic dysfunction, it's all pretty much overlapping. So, you can have dyspnea, irritability that is to say arrhythmias.

08:10 You may have, because of the inadequate perfusion of the brain, loss of attention.

08:16 You may have renal insufficiency because you're not perfusing the kidneys appropriately.

08:20 And because of the activation of the renin angiotensin aldosterone system, you will have edema. So, in terms of right-sided heart failure, as I've already mentioned, left-sided heart disease is the most common cause but there are other causes of primary isolated right heart failure and that includes primary lung disease, so either pulmonary fibrosis or primary pulmonary hypertension or even severe emphysema. Because we have restriction of blood flow through the lungs, the right ventricle is under a greater pressure load and over time can fail. Right heart failure due to primary pulmonary processes is called cor pulmonale. Cor meaning heart, pulmonale meaning lungs. You can also have recurrent pulmonary embolization. So, not enough to kill you but recurrent low level embolization of blood clots usually from deep leg veins into the lungs can again block the pulmonary circulation and lead to elevated pulmonary pressures which can cause right heart failure. Another important cause particularly now with the obesity epidemic, a kind of around the world but particularly in developed nations, obstructive sleep apnea which leads to more snoring but also a relative hypoxia during sleep. All that obese tissue sits up against the upper airway and you may get compromised oxygenation of the lungs. The way the lungs deal with diminished oxygenation in any particular part of the lung is to reduce the blood supply to that area. If you have a localized area where you are not getting good oxygenation, you don't want to send blood there.

10:15 However, if you're not getting good oxygenation to the entire lung, now we're going to squeeze all the vessels of the pulmonary vasculature and we're going to have right-sided heart failure due to chronic recurrent nightly obstructive sleep apnea.