cardiac function

inotropism

ability of heart to change contractility independent of preload and after load

chronotropism

ability of heart to change rate

lusitropism

relaxation properties of the heart

dromotropism

relating/influencing conductivity of nerve fibers or cardiac fibers

as you increase 1L of VO2…

you increase 5 liters of cardiac output (Q)

overall main factors that regulate Q

• volume of blood returning to the heart (VR)

• chronotropic & inotropic effects

stroke volume constituents

preload, contractility, afterload, distensibility/compliance

impacting factors of increasing ventricular preload

• increase in outflow resistance

• increase in atrial inotropy

• increase in ventricular compliance

• increase in venous pressure due to decrease in venous compliance

  • and also due to increase in venous blood volume

• decrease in inflow resistance

• degrease in ventricular inotropy

• decrease in heart rate

define afterload

force opposing ventricular contraction during systole (other terms = wall stress/wall tension)

means of increasing afterload

increase vascular resistance (HTN/vasopressors)

decrease arterial compliance (atherosclerosis)

outflow tract obstruction (aortic stenosis/OHCM)

increase in left ventricular size/volume

means of decreasing afterload

decrease vascular resistance (antiHTN meds)

decrease left ventricular size/volume

positive pressure ventilation

distensibility/compliance