Diastolic Dysfunction

Diastole has 4 phases:

1. Isovolumetric relaxation
2. Early filling
3. Diasatsis
4. Atrial systole

LA to LV gradient is the driving force for LV filling.

1. IVRT:
- prolonged by impaired active relaxation as in ischaemia
- shortened by raised LA pressure
It is normally less than 100 ms

2. Early filling:
Pressure gradient is greatest during this phase.
So 80% of filling occurs.

The main determinants of filling are:
a.LA pressure
b.Rate of active relaxation
c.Myocardial elastic recoil

3. Diastasis:
Most complicated phase
As the gradient reduces the filling diminishes
The main determinant of filling: LV chamber compliance

LV compliance is in turn determined by:
a.intrinsic myocardial stiffness
b.ventricular mass
c.pericardial restraint
d.RV Volume
e.LV Volume

4. Atrial systole:
increases trans-mitral gradient and accounts for 15-20 % of normal filling.
In conditions of impaired active relaxation the contribution is higher as in AS.

Diastolic dysfunction is divided into:

Active - affects early active relaxation(IVRT and first part of early filling) due to delayed re-uptake of calcium - thus prolongs relaxation
Examples include ischemia, hypertension, AS and HCM
Passive - affects later passive filling phase (later part of LV filling, diastasis and atrial systole) and it is due to reduced chamber compliance.
Examples include amyloidosis and myocardial fibrosis
The natural history of abnormal relaxation is to progress to reduced chamber compliance.

Echocardiographic assessment:
1. 2-D
2. M-mode
3. Transmitral doppler
4. Pulmonary venous doppler
5. Newer - Colour M-mode
- Tissue doppler imaging

2-D:
Look for hypertrophy in trans gastric mid SAx view at end diastole
concentric - wall thickness increased out of proportion to chamber size - due to pressure overload. This may be asymmetrical, affecting anterior septum in prefrence.
eccentric - wall thickness increased in proportion to chamber size
Thickening of anterior septum is best assessed in mid oesophageal long axis view. But do not do M-mode as it inveriably cuts the septum obliquely.
Normal thickness:
Male 1.3 and 1.2 cm
Females 1.2 and 1.1 cm. (Septum normally thicker than rest of the ventricle)

Trans mitral doppler:
Position of sample volume - level of open leaflet tips in diastole.
Normal waveforms:
Has 2 peaks - E and A.
E - due to early diastolic filling.
A - due to atrial systole
With age E max reduces while A max increases and become equal after 60 years.
Emax reduces from 0.70 m/s to 0.55 m/s
Amax increases from 0.35 m/s to 0.55 m/s.



Variables that can be measured include:
1. IVRT -
2. Emax
3. Evti
4. Edec
5. Amax
6. Avti
7. E/A ratio

Three abnormal pattern have been identified.
1.Impaired relaxation
2.Pseudonormalisation
3.Restrictive filling.

Impaired relaxation:

With impaired relaxation IVRT is prolonged.
E max is reduced.
E dec is increased.
Relaxation is complete late so filling occurs late in the atrial systole period. Thus E/A ratio is smaller than 1.
Again low LA pressure exaggerates these findings while increasing LA pressures minimises this.