How the Heart Fails: Pathophysiology, Ejection Fraction & HF Classification Explained (Video 1 of 5)

[00:00:02]Your patient comes in short of breath, legs swollen, and can barely walk to the bathroom. You know it's heart failure, but do you know why all the symptoms are happening?

[00:00:13]If you don't understand the mechanisms, well, you're going to struggle on your NCLEX and miss key clinical cues. During this Simple Nursing video, we're going to build the whole picture from scratch.

[00:00:24]So, let's get into it.

[00:00:26]Now, what is heart failure? Heart failure does not mean that the heart stopped.

[00:00:32]It simply means that the heart can no longer pump enough blood to meet the body's demands.

[00:00:37]Think of the heart as a pump. When that pump weakens or stiffens, well, things back up. Fluid backs up and organs don't get enough blood. That's basically heart failure in a nutshell.

[00:00:49]But to really understand it, we need to talk about three things the heart depends on.

[00:00:54]So, let's use the mnemonic PAC, P A C.

[00:00:58]P is for preload. This simply means the volume of blood stretching the ventricles before it contracts. So, basically, how full the heart is.

[00:01:07]A is for afterload, the resistance the heart has to pump against. Think of it like pushing blood through a narrow pipe.

[00:01:15]And C is for contractility, which is simply the strength of the heart muscle to squeeze itself.

[00:01:21]Now, heart failure disrupts one or more of these. For example, high afterload from hypertension, that high blood pressure. The heart works harder and eventually fails.

[00:01:32]Weak contractility from a heart attack.

[00:01:35]The pump simply doesn't squeeze enough.

[00:01:37]So, remember PAC, PAC, for three things the heart depends on. Preload, afterload, and contractility.

[00:01:46]Now, here's where nursing students get confused and where the NCLEX loves to test you. There are two types of heart failure based on ejection fraction.

[00:01:54]You see, ejection fraction, or EF, is the percentage of blood pumped out of the left ventricle with each beat.

[00:02:01]Normal EF is 55 to 70%. So, for the two types of heart failure, we have HFrEF.

[00:02:10]Heart failure with reduced ejection fraction, also called systolic heart failure.

[00:02:16]This is where the heart muscle is weak.

[00:02:19]It can't squeeze, so EF, or ejection fraction, falls below 40%. Just think, the pump is floppy.

[00:02:27]The next type is HFpEF.

[00:02:31]Heart failure with preserved ejection fraction, also called diastolic heart failure.

[00:02:37]This is where the heart muscle is stiff.

[00:02:40]It can squeeze fine, but it can't relax and fill properly.

[00:02:45]So, EF is normal, or above 50%.

[00:02:48]Think the pump is rigid.

[00:02:50]And here's the big NCLEX trap.

[00:02:53]Students assume that all heart failure means a weak squeeze. Well, nope, you're wrong. HFpEF patients have a normal ejection fraction.

[00:03:04]And they still have all the classic congestion symptoms.

[00:03:08]So, you need to know the difference.

[00:03:10]Now, here's the part that ties everything together. The compensatory mechanisms, where the heart starts to fail and the body tries to compensate.

[00:03:19]So, the two big players are the RAAS system, the RAAS system, and the SNS, the sympathetic nervous system. Now, for the RAAS system, there's low cardiac output, and so the kidneys sense low perfusion. They release renin, then angiotensin II, and finally aldosterone, which holds on to sodium and water.

[00:03:40]And that adds more volume, more preload, and the heart gets overwhelmed.

[00:03:45]Now, for the SNS, we have low output, so epinephrine and norepinephrine increase the heart rate and vasoconstriction, which leads to more afterload and the heart works harder.

[00:03:59]Now, in the short term, these mechanisms keep you alive, but what about the long term?

[00:04:04]Well, they accelerate heart failure. The heart gets bigger, stiffer, and weaker.

[00:04:10]This is what's called cardiac remodeling, and this is exactly why heart failure medications like ACE inhibitors, beta blockers, and diuretics work.

[00:04:21]They block these compensatory systems, which we're going to be covering more on in video three of this series.

[00:04:28]Now, the New York Heart Association classified, or the NYHA, tells us how symptomatic the patient is.

[00:04:37]There are four classes.

[00:04:39]So, class one, patients have no symptoms with ordinary activity.

[00:04:43]Heart failure is there, but the patient doesn't feel it.

[00:04:47]Class two is where patients have a slight limitation and show symptoms with moderate exertion.

[00:04:53]So, for example, when climbing stairs, patients are short of breath.

[00:04:57]Now, class three, there's marked limitations. So, patients show symptoms with minimal activity.

[00:05:03]Even something as minimal as getting dressed causes fatigue.

[00:05:07]And finally, class four, patients have symptoms at rest. They cannot function without discomfort.

[00:05:13]So, for the memory trick, think of 1 2 3 4 as a stairs visual.

[00:05:19]Each step up equals less activity tolerance. Now, it's important to know that the NCLEX uses this NYHA to determine medication choices and treatment goals.

[00:05:30]So, for patients considered class three or even four, it's time for advanced therapy.

[00:05:36]All right, now for a quick recap.

[00:05:38]Remember PAC, P A C, preload, afterload, and contractility.

[00:05:43]All three things the heart depends on.

[00:05:46]H F R E F means that we have a weak squeeze. And H F P E F means a stiff fill.

[00:05:55]And the RAAS and SNS try to help out, but end up making things worse.

[00:06:00]And finally, the NYHA tells you how bad these symptoms really are.

[00:06:05]Now, in the next video, we're going to break down why left-sided heart failure causes shortness of breath. And why right-sided heart failure causes leg swelling.

[00:06:15]Trust me, once you see it, you'll never forget it.

[00:06:18]So, on your screen right now is the next video in the series.

[00:06:22]So, go watch that next. Or, if you want a complete study system, not just individual videos that actually helps this stick, check out simplenursing.com using the link on your screen. All right, I'll see you in the next video.