Cardiac Pressure Volume Loop Flashcards
What does the End-systolic pressure volume relationship (ESPVR) curve describe?
The maximal pressure that can be developed by the ventricle at any given left ventricle volume. The PV loop cannot cross over the line for any given contractile state, however, the curve can be shifted with substances like norepi.
What is the formula for compliance?
C=∆V / ∆P
Describe a healthy ventricle in terms of compliance?
It is very compliant during diastole and NOT very compliant during systole. A highly compliant ventricle is easy to fill.
What is the formula for elastance?
E = ∆P / ∆V. or 1/C. A low elastance ventricle is easy to fill.
Is the ESPVR relatively insensitive to changes in preload, afterload and heart rate?
Yes. The ESPVR becomes steeprer and shifts to the left as isotropy (contractility) increases. The ESPVR becomes flatter and shifts to the right as isotropy decreases.
What does the EDPVR describe?
The passive filling curve for the ventricle and thus the passive properties of the myocardium. The slope of the EDPVR at any point is the reciprocal of ventricular compliance.
In ventricular hypertrophy what happens to ventricular compliance? What is the result in end-diastolic pressure?
Ventricular compliance decreases meaning the ventricle is stiffer. The result is a higher ventricular end-diastolic pressure at any given end-diastolic volume. Alternatively, for a given EDP, a less compliant ventricle would have a smaller EDV due to impaired filling.
In dilated cardiomyopathy where the ventricle becomes highly dilated without appreciable thickening of the wall what happens to ventricular compliance? What effects does it have on EDV and EDP?
The ventricular compliance increases. The EDV may be very high but the EDP may not be greatly elevated.
What is stroke volume?
It is the volume of b loos ejected by the ventricle in a single contraction. It is the difference between the end diastolic volume and the ESV. SV = EDV-ESV
What affects stroke volume?
Changes in preload, afterload, and isotropy (contractility). In normal hearts the SV is not strongly influenced by after load, whereas, in failing hearts, the SV is highly sensate to after load changes.
What is ejection fraction?
defined as the fraction of EDV that is ejected out of the ventricle during each contraction. EF = SV/EDV. Healthy EF’s are typically greater than 0.55. It is dependent on loading.
What does low EF usually indicate?
Systolic disfunction. It is also a clinical indicator of the inotropy (contractility) of the heart. Increasing inotropy leads to an increase in EF, decreasing inotropy decreases EF.
What is preload equal to? What about after load?
Preload is the EDV at the beginning of systole. Afterload is ventricular pressure at the end of systole. Meaning at the time of aortic valve closure. Preload is volume measured in mL and after load is pressure in mmHg. Preload times after load equals work.
A V vs P curve reveals the ______ in stroke volume with increasing EDV (preload).
Increase. It is sensitization and the F-S law in action
A V vs P curve reveals ______ in stroke volume with increasing ventricular after load.
Decrease. The SV is lower meaning less blood is ejected per heart beat.
