Cardiac preload and afterload: Definitions, Factors, and Heart Failure

define preload

the amount of blood returning to the heart (venous return) before contraction

what is end diastolioc volume?

how much the ventricle stretches before they contract

what determines end diastolic volume?

preload determines the EDV

what 3 factors influence preload?

venous return, blood volume, and ventricular compliance

what is another term for preload?

filling pressure

define afterload

the resistance the heart must overcome to eject blood during systole

what factors influence afterload?

systemic vascular resistance

blood pressure

aortic valve condition

what is the frank starling mechanism?

increased stretch causes stronger contraction

what is a simple way to think of afterload?

the "force" the heart pushes against

what happens to stroke volume when preload increase?

stroke volume increases

what happens with too much preload over time?

the myocardium overstretches and contractility decreases

what does high afterload do to the heart?

makes it harder for the heart to pump

increased afterload causes increased demand for what?

myocardial oxygen demand

chronic high afterload can lead to what structural change?

ventricular hypertrophy

chronic high afterload can eventually lead to what?

it can lead to heart failure because it forces the left ventricle to work harder

what are causes for increased preload?

fluid overload (kidney failure, IV fluid excess, CHF)

valvular regurgitation (mitral/tricuspid)

dilated cardiomyopathy

which valvular disease increases preload?

mitral and tricuspid regurgitation

how does excess preload affect ventricular size?

causes the ventricle to dilate

what type of heart failure results from reduced contractility due to overstretching?

systolic heart failure (HFrEF)

where does blood back up in left sided heart failure and what does it cause?

into the lungs causing pulmonary congestion

where does blood back up in right sided heart failure and what does it cause?

into the systemic venous system causing systemic congestion

what is the most common cause of increased afterload?

hypertension

how does aortic stenosis increase afterload?

the narrowed valve increases resistance to ejection

how does pulmonary hypertension affect the right heart?

it increases RV afterload and can cause RV failure

what type of hypertrophy is caused by chronic high afterload?

concentric hypertrophy

why does concentric hypertrophy impair filling?

thickened walls reduce chamber compliance and filling

what kind of heart failure does afterload cause first?

diastolic heart failure which then can lead to systolic heart failure

what type of HF is associated with diastolic dysfunction?

diastolic heart failure (HFpEF)

what can persistent afterload strain eventually lead to?

systolic heart failure once the heart weakens

what are the steps in assessing preload (volume status)

IVC assessment

LVEDV

Pulmonary Venous Flow

how is preload assessed with the IVC?

measuring diameter and collapsibility

what is a normal IVC inspiratory collapse?

greater than 50% collapse

what does a dilated IVC with poor collapse suggest?

elevated RAP , fluid overload, and possible congestive heart failure

what does a small fully collapsing IVC suggest?

low RAP due to dehydration,hemorrhage), hypovolemia

what does increases LVEDV indicate?

high preload

what does decreased LVEDV indicate?

low [reload (hypovolemia or poor filling)

pulmonary venous doppler helps assess pressure in which chamber?

left atrium

what are we assessing when we do pulmonary venous flow doppler

left atrial pressure

if we have high preload how will our pulmonary venous flow be?

we will have an abnormal pulmonary venous flow

what 3 things do we look for when assessing afterload?

LVH

Aortic valve assessment (Ao stenosis)

Systemic Vascular Resistance

what LV wall thickness suggests LV hypertrophy?

greater than 1.1 cm

what is afterload linked to?

ventricular wall stress and resistance

what do we measure when assessing the aortic valve for aortic stenosis

measure peak velocity

measure mean gradient

what echo findings suggest severe aortic stenosis?

peak velocity >4m/s

mean gradient >40mmHg

what can increased afterload be caused by?

aortic stenosis

what does elevated SVR indicate?

increased afterload

what can cuase an increased afterload/elevated SVR?

hypertension

vasoconstriction

what does low SVR indicate?

decreased afterload

what can cause a decreased afterload/low SVR?

sepsis

vasodilation

what 5 things do we assess when assessing for heart failure?

LVEF

Diastolic Function (E/e' ratio via TDI)

pulmonmary HTN (RVSP)

GLS

Right ventricular dysfunction

What LVEF indicates systolic heart failure (HFrEF)

<40%

what LVEF indicates diastolic heart failure(HFpEF) ?

>50% with diastolic dysfunction

also can say preserved EF with diastolic dysfunction

what defines HFpEF?

preserved EF with diastolic dysfunction

What does E/e' >15 indicate?

elevated left atrial pressure (diastolic HF)

what does E/e' <8 indicate?

normal filling pressure

what do we measure to assess pulmonary hypertension (RVSP)?

measure TR vmax

What TR velocity suggests pulmonary hypertension?

>2.8m/s

what is a normal GLS value?

<-18%

how do we assess right ventricular dysfunction?

tapse and mcconnells sign

what TAPSE value suggests RV failure?

<1.6cm

what is McConnells sign associated with?

Explain volume overload vs pressure overload

explain why MR causes volume overload

explain why hypertension causes pressure overload

compare HFrEf and HFpEF

why does chronic pressure overload eventually weaken the heart?

how can echo distinguish preload problems from afterload problems?