Overview Stroke Volume (SV) affected by contractility afterload preload ↑ SV when ↑ preload ↓ afterload ↑ contractility Contractility (and SV) ↑ with catecholamines ↑ activity of Ca2+ pump in sarcoplasmic reticulum ↑ intracellular calcium ↓ extracellular sodium ↓ activity of Na+/Ca2+ exchanger digitalis ↑ intracellular Na+, resulting in ↑ Ca2+ Contractility (and SV) ↓ with β1 blockade heart failure acidosis hypoxia/hypercapnea non-dihydropyridine Ca2+ channel blockers Myocardial O2 demand is ↑ by ↑ afterload (proportional to arterial pressure) ↑ contractility ↑ heart rate ↑ heart size (↑ wall tension) ↑ preload Other situations SV ↑ in anxiety, exercise, and pregnancy a failing heart has ↓ SV