systolic heart failure

[gaajr1, RN]

I was reading about types of heart failure and when I came to systolic ventricular dysfunction, there is a part I did not understand. I did not have a lecture yet but would really be grateful if anyone could please explain it to me? I thought of waiting till lecture but it's just bugging me, for I know for sure I'm a bit confused!!

Here it is directly from the book:

"Systolic heart failure results when the heart is unable to contract forcefully enough during systole to eject adequate amounts of blood into the circulation. Preload increases with decreased contractility, and afterload increases as a result of increased peripheral resistance. The ejection fraction drops from a normal of 50% to 70% to below 40%. As the ejection fraction decreases, tissue perfusion diminishes and blood accumulates in the pulmonary vessels. Manifestations of systolic dysfunction may include symptoms of inadequate tissue perfusion or pulmonary and systemic congestion."

The part in bold is what I'm confused with. From what I understand preload is the stretching of the myocardium at the end of diastole, just before contraction and the stretching is related to the volume within the ventricle. So, how does preload increase in this case? I know there is something I didn't get straight, please explain. Thanks!

[hypocaffeinemia, BSN, RN]

Simplistically, the contractility of the ventricles is inversely related to the amount of stretching. If a heart deals with a high end-diastolic volume (essentially, a high preload) for a sustained portion of time, it will ultimately dilate and lose contractility in the process.

That doesn't exactly explain your statement, However, if the contractility decreases, there will be more blood left in the ventricle at end-systole, which together with the normal diastolic flow would equate to a higher end-diastole.

Which would further dilate the heart, perpetuating the cycle.

Does that make sense?

[Daytonite, BSN, RN]

preload increases with decreased contractility

essentially, the heart is enlarging and as it enlarges it is getting weak (the decreased contractility), work backs up (preload) and the heart is getting behind in its job although it never stops pumping.

these concepts are not easy to understand at first readings. there is a website that explains these concepts over several pages and it is just as hard to read and understand. takes many readings before the lightbulbs go off in the brain. see http://cvphysiology.com/index.html - cardiovascular physiology concepts, click on "heart failure" link at the left side of the page

[gaajr1, RN]

Daytonite, it is basically going back to Starling's law, right? As you said the cardiac unit does take timeto sink in, that's why I started to read and trying to understand as much as possible. Thanks for your help.

[Daytonite, BSN, RN]

You are smart to start looking at this and trying to make sense of it now. I never did understand Starlings's. You do need to understand preload, afterload and the signs and symptoms they produce. They are among the related factors of the nursing diagnosis of Decreased Cardiac Output

[ghillbert, MSN, NP]

Starling's law is very easy, depending on how it's explained. Most people explain it as imagining an elastic band. If your band is new and fresh, you don't have to stretch it much to flick it. This equates to only requiring a low preload to be able to eject the LV contents easily. If you have systolic HF, your elastic band is loose and rubbery. In order to flick the band, you need to stretch it much harder/further. This equates to needing a high preload (LV filling pressure) in order to generate enough pressure to eject enough blood each beat.

Regarding your bolded statement, think of it as this: The LV can't eject properly, so fluid remains in there at end systole. Then during diastole, it fills up even more. So you have a big, stretched ventricle = higher preload due to the sys HF.

[gaajr1, RN]

ghillbert, thanks a lot for the explanation. I think it makes more sense to me now.

[sunkissed75, CNA]

starling's law is very easy, depending on how it's explained. most people explain it as imagining an elastic band. if your band is new and fresh, you don't have to stretch it much to flick it. this equates to only requiring a low preload to be able to eject the lv contents easily. if you have systolic hf, your elastic band is loose and rubbery. in order to flick the band, you need to stretch it much harder/further. this equates to needing a high preload (lv filling pressure) in order to generate enough pressure to eject enough blood each beat.

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ahhh... i get it a little bit, but i feel like i'm still lost. i don't know why i can't get my head around it. i need to have a definition in my own words... but it's hard when i don't understand it enough to define it!! i have googled it and i can only find the same definitions with the same big words. can someone please spell it out for me like i am in kindergarten!! diagrams may help... just kidding!!!

[sunkissed75, CNA]

ha ha... i get it now!! it clicked!! no response neccessary!!