Stroke Volume, Cardiac Output, Starling's Law, & CVD

Stroke Volume, Cardiac Output, Starling’s Law, and Cardiovascular Diseases

Stroke volume

amount of blood pumped out of the left ventricle in one contraction

cardiac output

amount of blood pumped by each ventricle in one minute

Cardiac outpout equation

CO = SV x HR

typical stroke volume

about 70-80 mL per beat

example of cardiac output

HR 70 × SV 80 mL = 5600 mL/min (5.6 L/min)

end diastolic volume (EDV)

blood in ventricle just before contraction

end systolic volume (ESV)

blood remaining in ventricle after contraction

stroke volume formula

SV = EDV - ESV

why athletes have low resting HR

high stroke volume → heart doesn’t need to beat as often

why CHF patients have high resting HR

low stroke volume → heart rate increases to maintain cardiac output

starling’s law

increased ventricular stretch (preload) increasess stroke volume

preload

degree of stretch of ventricular walls before contraction

effect of increased venous return

increases preload → increases stroke volume → increases cardiac output

aneurysm

abnormal bulge in a blood vessel wall; may rupture and cause fatal bleeding

hypertension

chronically elevated BP ≥ 140/90 mmHg

normal BP (in adults)

< 120/80 mmHg (systolic <120 & diastolic < 80)

why hypertension is dangerous

can lead to heart attack (MI), kidney failure stroke, aneurysm

stroke

inadequate or interrupted blood supply to the brain; medical emergency

ischemic stroke

blocked artery reduces blood flow to brain

hemorrhagic stroke

blood vessel leaks or ruptures in the brain

TIA (Transient Ischemic Attack or "mini-stroke”)

temporary interruption of blood flow; no lasting symptoms

causes of ischemic stroke

fatty plaques, blood clots, debris from heart lodging in brain vessels

causes of hemorrhagic stroke

high BP, anticoagulant overuse, aneurysm rupture, trauma, amuloid angiopathy

arteriosclerosis

general hardening and loss of elasticity of arteries

atherosclerosis

plaque buildup in arterial walls; specific type of arteriosclerosis

how plaque form

cholesterol deposits accumulate → narrow or block arteries → may rupture

myocardial infarction (heart attack)

heart muscle begins to die due to lack of blood flow

cause of MI

blockage in coronary arteries; untreated → permanent damage or death

arrhythmia (OR dysrhythmia)

abnormal heart rhythm (too fast, too slow, irregular, ectopic)

tachycardia (FAST)

resting HR over 100 bpm

bradycardia (SLOW)

resting HR below 60 bpm

atrial fibrillation (AFib)

a rapid, chaotic, and irregular rhythm starting in upper chambers; often leading to stroke or HF

atrial flutter

(similar to AFib) BUT w/ more organized electrical signals in atria, causing very rapid yet steady contractions

supraventricular tachycardia (SVT)

(a broad term) rapid heartbeats that start in upper chambers, causing a sudden pounding feeling

ventricular tachycardia (VT)

fast, abnormal rhythms originating in lower chambers, can prevent heart from filling properly

ventricular fibrillation (VF)

a medical emergency where the ventricles quiver instead of pumping, which can result in sudden cardiac arrest

premature contractions (PACs/PVCs)

extra, early beats that feel like a skipped or fluttering heart