Diastolic Function & Diastolic Dysfunction
Diastolic function is defined as/describes the filling of the heart during diastole. The left ventricle is filled with blood shortly after the mitral valve opens initially by suction with a rapid early (E-wave) filling and the left ventricle (LV) expands. In healthy individuals a normal sized left atrium during atrial systole only contributes a minor amount, roughly in between 20%-30%. On the other hand the early filling via suction contributes 70%-80% of LV filling during diastole. In between passive and active filling of the left ventricle there is a period of time where only little filling occurs, the so called diastasis. Therefore diastolic dysfunction is understood as impaired left ventricular relaxation with increased stiffness of the LV and elevated filling pressures.
Clinical context & background
Possible causes of diastolic dysfunction are various such as structural heart diseases (hypertrophy, constriction, fibrosis) or functional heart disease (ischemia). Diastole is affected by a lot of factors such as heart rate, ventricular function and compliance, preload, atrial systolic function, heart rhythm and atrioventricular valve function. The prevalence of diastolic dysfunction is present in over 25% of the adult population over 40 years of age!
Echocardiography should be used as a tool in patients showing signs or symptoms of heart failure, e.g. dyspnea to evaluate if there is diastolic dysfunction present.
There are various variables to assess diastolic function using corresponding pathological cut off values:
- Mitral E/A ratio - cut off value: ≤ 0.8 & > 2
- Peak E velocity - cut off value: > 50 cm/sec
- Deceleration time (DT) - cut off value: 140 - 240 msec
- e´ - cut off values: septal < 7cm/sec, lateral < 10cm/sec
- E/e´ ratio - cut off value: average > 14 (septal >15 , lateral >13)
- Left atrial (LA) maximum volume index - cut off value: 34mL/m2
- Peak tricuspid regurgitation (TR) velocity - cut off value: > 2.8m/sec
- Isovolumetric relaxation time (IVRT) - cut off value: ≤ 70 mm/sec - >100 mm/sec
- pulmonary venous S/D ratio - cut off value: < 1
- Ar - A duration - cut off value: >30 msec
- Grade I diastolic dysfunction, impaired relaxation: First stage of diastolic dysfunction. Decreased suction of the LV.
- Grade II diastolic dysfunction, pseudonormalization: Increased stiffness of the LV, elevated LAP.
- Grade III, restrictive filling (reversible): High LAP, noncompliant LV. May be reversible with reduction of preload (e.g. diuretics).
- Grade IV, restrictive filling (irreversible): As stage III with no benefit from reduction of preload.
As a first step to evaluate diastolic function it is useful to evaluate mitral inflow patterns. It is reproducible, easy to learn and gives prognostic information. First of all the peak of the passive filling of the LV (peak E wave) and the active contraction of the left atrium in atrial systole (peak A wave) should be assessed, and an E/A ratio should be calculated. In addition deceleration time (DT) of the early filling phase of the LV should be measured. Four different filling patterns can be differentiated in patients: normal filling, impaired relaxation (grade I diastolic dysfunction, normal LAP), pseudonormal filling (grade II diastolic dysfunction, elevated LAP), and restrictive filling (grade III diastolic dysfunction, elevated LAP). Additionally the time interval from aortic valve (AV) closure and mitral valve (MV) opening, the IVRT can be assessed.
In patients with preserved ejection fraction (EF) it is recommended in the current guidelines to evaluate four variables to assess diastolic dysfunction: e´, E/e´ ratio, LA maximum volume index and peak TR velocity. If three of the parameters are pathological there is diastolic dysfunction present. In case of 2 pathological and 2 normal parameters parameters it is an intermediate state, and if three are non pathological there is normal diastolic function present.
In patients with reduced left ventricular EF an E/A ratio of ≤ 0,8 concordant with a peak E velocity of 50 cm/sec or lower leads to the conclusion that filling pressures must be normal, equals grade I of diastolic dysfunction. If E/A ratio is > 2 means that left atrial filling pressures are elevated and diastolic dysfunction grade III is present.
An E/A ratio of ≤ 0.8 with a peak E velocity of over 50 cm/sec or an E/A ratio > 0.8 but < 2 there are more parameters like TR velocity, LA maximum volume index and E/e´ needed to evaluate diastolic function in these patients.
Pulmonary vein peak systolic to peak diastolic velocity should be used if one of the other variables is not available in patients with reduced left ventricular ejection fraction. Note that normal pulmonary flow consists of a systolic and a diastolic component and a very brief reversal flow during atrial systole.
If you want to get further insights into current diastolic function & dysfunction guidelines you can watch our free webinar here.
Diastolic stress testing:
Indication: If resting echo does not explain the symptoms of heart failure or dyspnea especially with exertion. It is considered positive if:
- average E/e´ > 14 or septal E/e´ ratio > 15 with exercise
- peak TR velocity > 2.8 m/sec with exercise
- septal e´ velocity is < 7 cm/sec
Pitfalls & Tipps
L-Wave: During diastasis there is normally no flow from the left atrium to the LV. If a flow occurs, during slow rhythms only, it is a sign for elevated filling pressures, therefore diastolic dysfunction is present.
Supernormal filling: In young, fit and healthy individuals you can see a very tall E-wave, a normal DT, a very small A-wave and an E/A ratio >2 which looks like a restrictive filling pattern. This is due to a very strong suction of the LV during diastole.
Be aware that visualizing suboptimal Doppler signals is a huge pitfall. You should not conclude if there is diastolic dysfunction present or not if you do not have optimal Doppler signals.
Be aware that one normal parameter (normal sized left atrium) does not automatically indicate normal diastolic function and exclude diastolic dysfunction.
Note IVRT is prolonged in impaired relaxation, gets shorter with left atrial pressure (LAP) elevation. Be aware that IVRT becomes longer when people get older and is responsive to heart rate and systolic function.
Be aware that in young healthy individuals the S/D ratio of pulmonary venous flow is often below 1.
Be aware that you can not measure E/A ratio in presence of atrial fibrillation (AFIB), significant mitral regurgitation, significant mitral annular calcification, left bundle branch block (LBBB), paced rhythm or mitral stenosis. In patients with AFIB you can use E/e´ ratio and IVRT which is shortened.
Be aware that when you measure E/e´ ratio the variables are measured at different times in the cardiac cycle. It is age dependent, preload dependent and there is a variation if left ventricular systolic function changes. You should not measure e´ when a prosthetic valve or mitral annular calcification is present. Left atrial (LA) maximum volume index gives diagnostic and prognostic information. There is still no targeted therapy for patients with diastolic dysfunction.
Left atrial (LA) maximum volume index gives diagnostic and prognostic information.
There is still no targeted therapy for patients with diastolic dysfunction.
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