Diastolic function

Question 1

What is tau

Answer 1

Indicator of ventricular compliance: time constant for relaxation
* Tau (T): duration (ms) for ventricular pressure to fall 1/3 (63%) from its initial value at MV opening to the most negative pressure
o Most accurate method to measure ventricular compliance
o = 1/compliance

Question 2

Describe ventricular relaxation process. How does it pertain to Tau?

Answer 2

• Ventricular relaxation = active process
  o Ca2+ removed from cytosol against [gradient]
  o Relaxation rate determine the rate of pressure fall in the ventricle

 Rapidity of this drop = time constant Tau
* Tau ↓ → good relaxation
* Tau ↑ → reduced relaxation
o Delayed relaxation = prolong Tau
 Measured during IVRT: no change in loading conditions

Question 3

Other indicators of ventricular compliance

Answer 3

o Ratio or end diastolic volume to end diastolic pressure
o Rate of fall of ventricular pressure (-dP/dt) during IVRT
o Slope of curve from ventricular volume and pressure during diastole

Question 4

Goal of diastolic fct

Answer 4

allows heart to fill appropriately at normal filling pressures

Question 5

Diastolic dysfct leads to

Answer 5

myocardial alterations leading to incr resistance to filling and incr LVP

• With age, LV becomes stiffer and relaxes more slowly

Question 6

Define diastolic period

Answer 6

• Correspond to closure of semilunar valves to closure of AV valves
  o T wave => start of QRS

Question 7

Phases of diastole

Answer 7

1) Isovolumic relaxation phase
o Rapid energy dependant relaxation of LV myocardium => decr LVP
o Require ATP for Ca2+ uptake by SR = active process
o Rate of early diastolic LV relaxation
 incr w impaired ralaxation
 decr w incr LAP
2) Rapid/early filling => 80% of ventricular filling
o Peak flow velocity proportional to the pressure gradient LA => LV
 LV suction effect: LVP continues to decr
o LVP decr < LAP
3) Slow filling/diastasis => 5%
o LVP incr to = LAP
4) Atrial contraction => 15%
o incr LAP > LVP

Question 8

Cellular factors influencing relaxation

Answer 8

• decr intra¢ [Ca2+]: SR uptake of Ca2+ require =
  o ATP
  o Pi of phospholamban
• Pi of troponin I => incr rate of relaxation
• Inherent viscoelastic properties of myocardium
• Systolic load: incr systolic load => incr rate of relaxation
  o Rate of decr in Ca2+ is greater
• Others: pericardium, atrial function, ventricular interaction and afterload

Question 9

How does ventricular interaction influence myocardial relaxation

Answer 9

o RV & LV fct = intimately linked
 CO of LV must equate RV
 Except if imbalance, ie. Acute LV failure and pulmonary edema
o Pressure work from RV < LV.
 RV has normally thin walls
 LV hypertrophy include IVS => can incr RV work => RV hypertrophy = systolic ventricular interaction
o Bernheim effect: large LV can compress RV
 Impair RV filling

Question 9

Diastolic function determinants

Answer 9

• Active relaxation of the myocardium
• Compliance of the LV
• Pump function of the LA and PVs
• HR
• Age

Question 10

What is a feature of atrial function

Answer 10

Atrial contraction: Presystolic contraction = booster function = helps to complete LV filling
o Smaller myo¢
o Shorter AP: incr outward K+ currents (KAch + ITO)
o Fetal myosin phenotype

Question 11

LA volume is indicator of

Answer 11

useful indicator of presence, chronicity and severity of diastolic dysfct
* In diastolic dysfct: compensatory incr in atrial contraction
o incr A wave on Doppler mitral filling pattern

Question 12

Brainbridge reflex

Answer 12

incr venous return => mechanoR => incr SA node d/c rate => tachycardia

Question 13

How does pericardium influence diastolic fct

Answer 13

• Pericardium and endocardium
  o Restraining effect on diastolic properties of ventricles, especially RV
  o W/o pericardium: RV would dilate by 40%, RA by 70%
• Pericardial disease: effusive or constrictive
  o Acute volume incr => intrapericarial pressure > RA/RVP => decr venous filling

Question 14

Diastolic volume : influenced by

Answer 14

o Loading conditions
o Elastic properties: ability to recover normal shape after removal of systolic stress

Question 15

Compliance curve

Answer 15

• Compliance: relationship btw change in stress and resultant strain => curvilinear
  o Gentle initial slope
  o As pressure incr => volume increase less
  o Considerable incr in pressure for small incr volume
  o Influence Starling curve + pressure-volume loop + early diastolic filling
   decr compliance => lower Starling curve
   incr upward baseline on pressure-volume loop = incr LAP for early filling required

Question 16

Parameters of diastolic fct on echo

Answer 16

• 2D and M-mode
  o LA size
  o B-bump: late diastolic reopening of MV
• Doppler flow patterns
  o IVRT
  o Transmitral valve flow: peak E, A waves, Edec, E:A, DTe
• Color M mode: Vp
• PV flow: S/D ratio
  o Flow reversal seen during Akick → A: Ar
  o High velocity reversed flow
• MR: -dP/dT
• Invasive methods
  o Tau: rate of fall of LV pressure during IVRT
  o -dP/dT
  o Diastolic pressure-volume relationships

Question 17

Diastolic dysfct can be 2nd to

Answer 17

• Impaired relaxation
  o incr early diastolic LVP => delayed LV filling => incr atrial contraction contribution to filling
  o Hypertorphy, ischemia
• Decreased LV compliance
  o Stiff LV = pressure incr rapidly as LV fill
  o Larger role in late diastole when LV is partially filled
  o Fibrosis, infiltrative process, hypertrophy, structural abnormalities
• Forward failure => decr volume 2nd to decr filling
• Backward failure => incr LV filling pressure => incr LAP

Question 18

E wave

Answer 18

rapid early filling
o Peak E wave: reflect LA=> LV pressure gradient at beginning of diastole
o E wave deceleration: reflect time for equilibration of pressures
 i proportional to stiffness

Question 19

A wave

Answer 19

reflect LA => LV pressure gradient at end of diastole
o Small amount of filling
o Normally smaller vs E wave

Question 20

Factors affecting E/A waves

Answer 20

tachycardia, 1˚AVB, Afib

Question 21

E’ wave

Answer 21

brisk motion of mitral annulus as chamber expands
* Less dependent on preload

Question 22

Changes in spectral Doppler w/ diastolic dysfct

Answer 22

• decr E wave, incr deceleration time
• incr A wave, decr E/A ratio
• incr IVRT
• decr E’
• incr E/E’ ratio (at any stage of diastolic failure)

Question 23

Stages of diastolic dysfct

Answer 23

Delayed relaxation
Pseudonormal
Restrictive physiology

Question 24

Changes w/ delayed relaxation

Answer 24

slower muscle relaxation and impaired early filling
incr IVRT
decr peak E wave
decr deceleration rate
incr PV S:D ratio
a. Loss of elastic recoil => decr sucking force of LV in early diastole
i. Prolongation of LV pressure curve => delay MV opening
b. Normal compliance + LV filling pressure

Question 25

Changes w/ pseudonormal

Answer 25

normal flow profile despite diastolic dysfunction
a. As LAP incr with progressive dysfct => incr E wave and normalize pattern (large pressure gradient)
i. E/A ratio > 1 => severe diastolic dysfct
b. Impaired relaxation + decr compliance
i. incr LV filling pressures and LAP
c. decr IVRT => LV reach LAP faster because of incr LAP

Question 26

Changes w/ restrictive physiology

Answer 26

decr IVRT
incr E wave
decr A wave
decr deceleration rate

a. Severly impaired relaxation + decr compliance
i. +++ incr LV filling pressures
b. High early mitral inflow
c. Reduced Akick filling: incr LVP + failing LA contractility

Question 27

how regurgitation influence diastolic fct

Answer 27

• AI => incr LV diastolic P quickly in early diastole
  o Rapid equilibration of pressures, shorter E wave deceleration
• MR => incr pressure gradient => incr peak E wave