Stroke Volume SV affected by contactility afterload preload Increases with anxiety, exercise, and pregnancy Pulse pressure is proportional to SV Heart failure leads to decreased SV Contractility Contractility INCREASES with: Catecholamines (lead to an inc. activity of Ca2+ in the SR) Increased intracellular calcium Increased intracellular sodium Digitalis (incr. intracellular Na+ leading to incr. intracellular Ca2 Contractility DECREASES with: B1 block Heart Failure Acidosis Hypoxia / Hypercapnea O2 Demand Myocardial O2 demand is increased by: Incr. afterload Increased contractility Increased HR Increased heart size which increases wall tension Normal Pressures Normal Systolic Normal Diastolic RA < 5 < 1 RV < 25 < 5 PA < 25 < 10 PCWP (good approx of LA pressure) < 12 < 1 LA <12 < 1 LV < 150 < 10 Aorta < 150 < 90 Oxygen Dissociation Curve Shift of curve to right decreases HgB affintiy for O2 and increases unloading to peripheral tissues increases O2 supply in time of demand It is shifted to the right by increased increased 2,3 BPG (high altitude) metabolic needs PCO2 increased temperature H+ altitude Shift to left decreased 2,3 BPG (low altitude response) increased pH (alkalosis) decreased temperature decreased metabolism Cardiac Conduction Velocity Conduction velocity bundle of His, Purkinje fibers > atria > ventricles > AV node