Diastolic Patterns and Heart Failure Symptoms
The main symptom of heart failure is breathlessness. If cardiac in origin it is likely to be caused by either impaired emptying of the left atrium due to early diastolic dysfunction (relaxation disturbances) or due to raised left atrial pressure (restrictive filling pattern) as a complication to raised LV end-diastolic pressure. The latter has clear characteristics; dominant early diastolic component, short isovolumic relaxation time (Figure 1C and D), reduced apical early diastolic untwist rate13 and increased duration of flow reversal in the pulmonary veins in late diastole. The two conditions result in left atrial enlargement, reduced compliance and unstable function, hence potential development of atrial arrhythmia and even fibrillation (Figures 1G and H).11,14
Diastolic Disturbances and Heart Failure Signs
A third heart sound heard in heart failure is consistent with restrictive LV filling and is caused because of rapid change of early diastolic filling acceleration to deceleration. This condition reflects unstable cardiac function that needs left atrial pressure off-loading therapy with vasodilators. A fourth sound reflects isolated late diastolic filling due to severe early diastolic dyssynchrony. Signs of pulmonary oedema reflect raised left atrial (LA) pressure, which is secondary to stiff LV and raised end-diastolic pressure. Most patients with this condition present with some degree of mitral regurgitation, which further accentuates LA pressure. Systemic fluid retention is a sign of either stiff right ventricle (RV) or significant tricuspid regurgitation, secondary to left heart disturbances or due to primary right heart problems with or without pulmonary hypertension.15,16
Measurements of Diastolic Function
Doppler echocardiography in the assessment of diastolic function has a number of limitations; mainly relating to heart rate and arrhythmias, in addition to the ones mentioned above. Therefore, when assessing diastolic function the general recommendation is to use more than one measurement. LV filling volumes are studied by Doppler velocities obtained from the transmitral valve flow velocities in early diastole (E) and during atrial systole (A) waves. While peak velocities reflect diastolic function well, additional measurements should be considered to avoid any potential overor underestimation. E wave deceleration time is a good marker of raised LV end-diastolic pressure. A short isovolumic relaxation time – the interval between the end of the aortic Doppler velocity signal and the onset of the E wave – is a good reflection of LA pressure changes, although not in absolute terms. Also, a simple observation of E:A ratio could give a rough impression of diastolic function. In a patient aged over 50, a normal filling pattern is expected to have an E:A <1.0, in the presence of normal LA size (<28 ml/m2), normal LV configuration and normal LV intrinsic relaxation. With increasing left atrial pressures, the combination of E:A >1, enlarged LA, abnormal LV function and abnormal LV intrinsic relaxation (such as reduced e’) is expected17,18.
Relaxation Abnormality
This condition is mainly characterised by reduced E wave velocity, increased A wave velocity, E:A <0.8, prolonged E wave deceleration time (>200 ms) and isovolumic relaxation time (IVRT >100 ms). This LV filling pattern is also commonly seen in the healthy elderly population aged above 60 years and therefore has low accuracy in detecting heart failure (Figure 1B). However, if this pattern is present in conjunction with enlarged LA (volume >34 ml/m2) a strong suspicion of unstable LA pressures is raised and exercise provocation can be useful to detect further increases in LA pressure as shown by changes in E:A.19
Restrictive LV Filling Pattern
This condition is easily detected in heart failure with E:A >2, short E wave deceleration time (<150 ms) and IVRT (<60 ms). The majority of these patients also have increased LA volume (34 ml/m2) and some degree of raised pulmonary artery pressures. This pattern is commonly found in newly diagnosed patients or those not responding to optimum medical therapy because of immobile LV myocardium. Such pattern of cardiac function reflects instability that needs aggressive LA pressure offloading treatment with vasodilators.
In between the abnormal relaxation pattern and restrictive pattern there is a wide range of diastolic patterns but all could be described in one category based on the following measurements; LA volume, E:A, IVRT and DT etc. In those patients new additional methods have been proposed that help optimum evaluation e.g. e’ from tissue Doppler echocardiography and calculating E/e’, time difference between the duration of the transmitral A wave and respective retrograde pulmonary venous Ar (Ar-A). An E/e’ (mean of septal and lateral LV e’) >13 and Ar-A >30 ms are highly indicative of elevated LA pressure.19
LV Filling Pattern in Atrial Fibrillation
Irrespective of LV size and function, the development of myocardial stiffness and the rise in LV diastolic pressures cause LA enlargement, which with time may become unstable and cause fibrillation. In these patients there is a single component of LV filling, the E wave, with absent A wave on the transmitral and pulmonary venous flow, hence, E:A ratio and A wave duration difference are not applicable. However, E/e’ remains of diagnostic value for raised LA pressure in addition to the short E wave deceleration and the increased LA volume.20