Left Ventricular Pressure-Volume Loops

Left Ventricular Pressure-Volume Loops Pressure-volume loop plots LV pressure against LV volume through one complete cardiac cycle Factors affecting: Preload Afterload Contractility IHSS Valvular problems

Left Ventricular Pressure-Volume Loops KNOW: When the mitral and aortic valves are open and closed during each phase When systole begins (B) and ends (D) When diastole begins (D) and ends (B) Diastolic filling occurs between points A and B Ejection occurs between points C and D

Left Ventricular Pressure-Volume Loops Acute changes in preload Increased preload: Filling increases SV increases Decreased preload: Filling decreases SV decreases *NOTE: the ventricle empties to the same end-systolic volume after either an increase or decrease in preload

Left Ventricular Pressure-Volume Loops

Left Ventricular Pressure-Volume Loops Cardiac tamponade Unique loop

Left Ventricular Pressure-Volume Loops Acute changes in Afterload Increased afterload: Ventricle empties less completely SV decreases Increase in BP (shifts up and right) Decreased afterload: Ventricle empties more completely SV increases Decrease in BP (shifts down and left)

Left Ventricular Pressure-Volume Loops

Left Ventricular Pressure-Volume Loops Altered contractility Increased contractility: Ventricle empties more completely SV increases BP increases (shifts up and left) Decreased contractility: Ventricle empties less completely SV decreases BP decreases (shifts down and right)

Left Ventricular Pressure-Volume Loops

Left Ventricular Pressure-Volume Loops Summary of concepts: Alterations in preload: end-diastolic volume increases or decreases, but the amount of blood in the chamber at end-systole does not change Stroke volume falls: result of either an increase in afterload or a decrease in contractility, the volume of blood in the LV chamber increases (chamber dilates) Stroke volume increases: result of a decrease in afterload or an increase in contractility, the volume of blood in the LV chamber decreases (chamber shrinks)

Left Ventricular Pressure-Volume Loops IHSS UNIQUE P-V loop is shifted to smaller volumes and larger pressures (due to outflow tract obstruction) ONLY IHSS causes this type of combined shift

Left Ventricular Pressure-Volume Loops Chronic Aortic Stenosis (increased afterload) Concentric hypertrophy permits the LV to generate greater pressure LV volumes remain about normal P-V loop shifts upward

Left Ventricular Pressure-Volume Loops Mitral Stenosis (Decreased preload) LV filling is diminished P-V loop reflects a decreased preload Emptying is about normal

Left Ventricular Pressure-Volume Loops Acute Aortic Insufficiency (regurgitation) Volume in the LV chamber increases during early diastole P-V loop is small No isovolemic relaxation

Left Ventricular Pressure-Volume Loops Chronic Aortic Insufficiency (Eccentric hypertrophy) LV chamber dilates P-V loop is large because the SV is large No isovolemic relaxation

Left Ventricular Pressure-Volume Loops Be able to identify a P-V loop that shows aortic insufficiency Be able to identify whether the loop reflects acute or chronic aortic insufficiency

Left Ventricular Pressure-Volume Loops Acute Mitral Regurgitation P-V loop is small No isovolemic contraction

Left Ventricular Pressure-Volume Loops Chronic Mitral Regurgitation LV hypertrophies (eccentric) LV chamber dilates P-V loop is large because the SV is large No isovolemic contraction

Left Ventricular Pressure-Volume Loops A = Normal B = Mitral stenosis C = Aortic stenosis D = mitral regurgitation (chronic) E = aortic regurgitation (chronic)