Cardiac cycle and PV loops Flashcards

Question

Determinants of end systolic wall stress

Answer 1

= afterload o Constantly changing throughout systole o Determined by inotropic state

Answer 2

* SV: total volume of blood ejected * EDV: end diastolic volume * EDS: end systolic volume o incr wall stress (afterload) => decr ESV

Answer 3

pressure change required to elicit volume change * Maximal elastance = beginning of systole * Ability to returning to its normal volume after stretching force is released Pressure/volume

Answer 4

diastolic property → volume of blood that can be stored in given portion of circulation * Elastic deformation/change in volume secondary to an applied pressure * Opposite of elastance volume/pressure

Answer 5

* Constant volume, all valves are closed * IVCT = start of systole o Rapid rise in ventricular pressure o Until reach Ao or PA pressure and semilunar valve open * IVRT = start of diastole o Rapid fall in ventricular pressure o Until under atrial pressures and AV valve open

Answer 6

end systolic pressure/volume relationship * Line connecting several end systolic wall-stress volume point o Slope is Emax (end systolic pressure-volume curve) → maximal elastance of ventricle o V0: theoretic volume that chanber should empty if afterload was 0 * Affected by contractility and volume

Answer 7

(↓ESV for any afterload) → ↓ volume or ↑ pressure  + inotrope  ↑ contractility  ↓ afterload

Answer 8

(↑ESV for any afterload)  - inotrope  ↑ afterload  ↓ contractility

Answer 9

external work done by LV o Cardiac external work = systolic P x SV

Answer 10

end diastolic pressure/volume relationship * COMPLIANCE → determines how much end diastolic volume

Answer 11

↓ pressure per volume o ↑ Compliance * Hyperdynamic function (ex. CVD) * ↓ Myocardial stiffness (ex. DCM in early disease)

Answer 12

↑ pressure per volume unit o ↓ compliance * HCM * Pericardial disease

Answer 13

energy used for blood ejection → Emax AUC o Stroke work = systolic pressure x SV

Answer 14

energy generated w each cardiac cycle but not converted into kinetic energy (or external work)

Answer 15

* Internal work: total work of the heart for each contraction o Total mechanical work = external + potential work o Proportional to myocardial O2 consumption * Increase w heart dz

Answer 16

↓ SV → ↑ volume * ↑ IVCT → longer time to reach pressure * ↑ end diastolic volume and pressure o Compensatory o Not infinite mechanism: at some point → LVH → ↓ compliance * Volume ↓ * Pressure ↑ * Disease progression o Normal contractility at onset o Contractility ↓ → ↓ SV over time * Systolic PG in Aortic curve can be present depending on disease SAS

Answer 17

* ↑ SV → can eject more volume against lower pressure * ↓ IVCT → shorter time to reach pressure o Primary change * ↓ End diastolic volume and pressure o Cycle starting from a lower pressure and volume systemic vasodil

Answer 18

* ↑ End diastolic volume and pressure o ↑ contractility via Frank Starling * Initially o ↓ end systolic pressure and volume o Afterload ↑ → higher SV * Overtime o ↑ SV → more blood into Ao/syst vasculature o Afterload ↑ from ↑ arterial blood pressure * If inotrope positive o ↑ contractility normalize afterload * Normal IVCT AI, PDA

Answer 19

* ↓ end diastolic volume and pressure = primary change o ↓ SV * ↓ volume into Ao → ↓ Afterload * ↓ myocardial stretch → ↓ SV via Frank Starling * Normal IVCT hypovolemia, PH

Answer 20

decr inotropy => decr SV + compensatory incr preload * Incomplete ventricular emptying → incr EDV and ESV o ↓SV and CO * Curve slopes o ESPVR: flat slope from ↓ end systolic pressures => incr ESV o EDPVR: flat slope from ↑ compliance in early disease * RIGHTWARD SHIFT * decr stroke work

Answer 21

Ventricular filling depends on venous return and compliance of ventricle in diastole * HCM → impaired relaxation and decr ventricular compliance * EDPVR: steep slope → LEFTWARD AND UPWARD SHIFT o decr EDV + incr EDP * decr SV until compensation w/ ↑ preload occurs * No change in IVRT or IVCT

Answer 22

 ventricular compliance * EDPVR: steep slope → LEFTWARD AND UPWARD SHIFT o decr EDV + incr EDP * ESPVR: RIGHTWARD SHIFT

Answer 23

High outflow resistance caused by reduced valve orifice area => impaired LV emptying * ↑ peak systolic ventricular pressure → incr systolic wall stress o ↑ afterload → ↓ SV and ↑ ESV * decr SV: velocity of fiber shortening decr 2nd to incr afterload o decr further w development of systolic and diastolic dysfct * incr ESV o incr EDV because ESV added to venous return = incr preload o Activate Frank starling => incr contractility  Can be sufficient in mild AS to maintain normal SV  Compensatory incr in EDV limited by LVH due to chronic  in afterload * Can lead to large incr EDP + decr EDV because of incr stiffness * Contractility is unchanged

Answer 24

* ↑ preload: LV fills from AI + atrial volume o  ventricular filling   EDV  Activate Frank Starling →  contractility → incr SV * incr LV peak systolic pressure  As long that not in failure = small incr in ESV * If failure: incr ESV => decr SV o Dilation of LV secondary to AI  incr ventricular compliance  Also contributes to incr EDV * ↑ afterload: ↑ wall stress during ejection * Absence of true IVRT: blood flows from the Ao when diastole start + blood continue to flow even when MV open (AoP > LVP) o No vertical line from Ao closure and MV opening * Absence/brief IVCT: LV start contraction and incr LVP o AI still flows until LVP > AoP o ↓ diastolic pressures * Contractility unchanged

Answer 25

* ↑ preload: regurgitant volume ↑ LAP → ↑ LV filling pressure o EDPVR: steep curve * decr afterload: MR is a = resistance pathway o ↓ total outflow resistance o decr ESV (can incr if CHF) w/ unchanged contractility * Absence of true IVRT: blood continue to flow back into LA as LVP > LAP * Absence of true IVCT: blood start to flow across MV before AoV open * Dilation secondary to incr EDV => incr LV compliance o Would normally incr afterload, but not in case of MR * SV is incr = volume ejected into Ao + LA o But decr CO => net forward flow in Ao in reduced

Answer 26

* incr preload o EDPSV: steep curve o incr EDV because of overciculation of the blood in pulmonary circulation o incr venous return to LA * incr SV with stable ESV o Frank starling activation 2nd to incr EDV

Answer 27

* decr preload from impaired LV filling => ↓ EDV o decr SV => decr CO (Frank Starling) * ↓ afterload from ↓ LV filling and ↓ AoP o decr wall stress o decr ESV slightly

Answer 28

* ↑ preload compared to LV o Same SV as both sides have same SV * ↓ afterload from low PVR o Much of RV ejection occurs after systolic pressure is reached o RV very sensitive to changes in afterload * ↓ contractility o Dependent on coordinated contraction w/ LV (IVS)  ↓ LV contractility or BBB can ↓ contractility