Heart 2 Flashcards
Cardiac output = ?
“CO = Stroke volume (SV) x Heart rate (HR)
- SV = end diastolic volume (EDV) - end systolic volume (ESV)”
Mean arterial pressure (MAP) =?
“MAP = CO x total peripheral resistance (TPR)
or
MAP = 2/3 diastolic pressure + 1/3 systolic pressure”
Pulse pressure = ?
“pulse pressure = systolic pressure - diastolic pressure
- it is proportional to SV, inversely proportional to arterial compliance”
during the early stages of exercise, CO is maintained by? What about late stages of exercise?
“early stages: ↑ HR and ↑SV
late stages: ↑ HR only (SV plateaus)”
Stroke volume is increased by?
"SV CAP ↑ Contractility (exerise, anxiety, pregnancy) ↓Afterload ↑ Preload (remember SV = EDV - ESV)"
Contractility increases with?
“Catecholamines (↑ activity of Ca2+ pump in sarc retic)
↑ intracellular Ca2+
↓extracellular Na+, or ↑ intracellular Na+
Digitalis (blocks Na+/K+ pump, ↓Na+/Ca2+ exchanger activity)
(remember SV = EDV - ESV)”
Contractility decreases with ?
β-blockade (↓ cAMP), Heart failure with systolic dysfunction, acidosis, hypoxia, non-dihydropyridine Ca2+ channel blockers
↑ myoCARDial O2 demand is ↑ by?
“↑ Contractility
↑ Afterload (proportional to arterial pressure)
↑heart Rate
↑ Diameter of ventricle (↑ wall tension)”
Preload is approximated by? What two things does it depend on?
Preload approximated by ventricular EDV; depends on venous tone and circulating blood volume
Afterload is approximated by ?
“afterload approximated by MAP
↑ Afterload → ↑ pressure → ↑ wall tension per Laplace’s law”
What ↓ preload? What ↓ afterload?
vEnodilators (nitroglycerin) ↓ prEload, vAsodilators (hydralazine) ↓ Afterload, ACE inhibitors and ARBs ↓ both preload and afterload.
LV compensates for ↑ afterload by hypertrophy in order to do what?
↓ wall tension
