Left Ventricular Pressure-Volume Loops左心室压力容积环.ppt

Left Ventricular Pressure-Volume Loops Left VentricularPressure-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 VentricularPressure-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 VentricularPressure-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 VentricularPressure-Volume Loops Left VentricularPressure-Volume Loops Cardiac tamponade Unique loop Left VentricularPressure-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 VentricularPressure-Volume Loops Left VentricularPressure-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 VentricularPressure-Volume Loops Left VentricularPressure-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 c