Cardiac Physiology

Systolic

contraction/ejection

1/3 of cycle

ventricle

Diastolic

relaxation/filling

2/3 of cycle

ventricle

preload

end diastolic volume-volume of blood in the ventricles prior to ejection

Venus return

afterload

resistance that must be overcome for ventricles to eject blood

BP

systolic

contraction

heart rate

measures in beats per minute

End diastolic volume

amount of blood remaining in the ventricle at the end of ventricular filling

end systolic volume

amount of blood remaining in the ventricle at the end of ventricular contraction

stroke volume

output during a single heartbeat

heart failure

EDV-ESV

cardiac output

blood volume circulating per minute

single heartbeat x bpm

SV x HR

diastolic

relaxation

heart muscle is perfused

total peripheral resistance

amount of resistance to blood flow in the vascular system

TPR=PVR

decreased plasma volume

systemic blood pressure

pressure exerted on the vessels in the systemic system

SVxHRxTPR

SVxHRxPVR

COxPVR

impacted by diuretics

beta blockers

decrease HR

ejection fraction (EF)

percentage of blood ejected from the heart during ventricular systole/ventricular contraction

SV/EDV

Mean Arterial Pressure

average arterial pressure throughout one cardiac cycle

1/3 systolic + 2/3 diastolic

75-100 normal

MAP <60

bad

kidney failure

MAP >160

Stroke

MAP systemic regulation

cardiac output

systemic vascular resistance

renal

autonomic nervous system

RAAS system

aldosterone increases sodium reabsorption → increased plasma volume

angiotensin II → smooth muscle contraction → vasoconstriction

Autonomic nervous system

baroreceptors in carotid sinus and aorta → effect CO

vagal stimulation

parasympathetic: decrease chronotropic activity

affects PVR and vasoconstriction

Chronotropic

Chronological

rate

ionotropic

force

Systolic - contraction

open- stenosis valves (aortic & pulmonic)

closed - regurgitation valves (Mitral&tricuspid)

diastolic - relaxation

open - stenosis valves (mitral&tricuspid)

closed- regurgitation valves (aortic&pulmonic)

Valsalva or abrupt standing

decrease venous return → decreased EDV → decreased SV

Valsalva: decrease aorta and pulmonic stenosis

decrease in volume of flow from ventricles through valves

Valsalva: decreased VSD sound

decrease in volume of flow → decreased shunting

Valsalva: increase hypertrophic cardiomyopathy

increase when standing

decrease EDV→ decrease stretching → decrease in LV outflow tract size → increase intensity of murmur

Increase in venous return

preload

increase in SVR

afterload

increase MR

increase afterload & preload→ increase backflow pressure → increase flow across regurgitant valve

Increase VSD

increase in preload and afterload → increased shunting

increase AR

increase afterload → increase regurgitation during diastole

decrease hypertrophic cardiomyopathy

increase EDV→ stretching of ventricle→ larger outflow tract→ decrease outflow stenosis