Assessing Atrial Mechanical Remodeling and Its Consequences

Abstract

T he principal function of the left atrium is to modulate left ventricular (LV) filling and cardiovascular performance through reservoir, conduit, and booster pump functions; the latter is often (mistakenly) regarded synonymously with atrial function, and in contrast to the reservoir and conduit phases, has been studied extensively. Typically, the importance of atrial contraction has been estimated by measurements of cardiac output and end-diastolic volumes both with and without effective atrial systole, by relative LV filling using Doppler transmitral velocimetry (E/A ratios) or radionuclide angiography, or by atrial shortening using 2D echocardiography, angiography, and sonomicrometry. Despite considerable investigation, the magnitude and relative importance of the atrial contribution to LV filling and cardiac output remain controversial and provide motivation for a more complete evaluation of the atrial cycle. In this regard, nearly half of the LV stroke volume and its associated energy is stored in the left atrium during ventricular systole, which acts as a ventricular restoring force during the ensuing ventricular diastole. 1 This reservoir function of the left atrium is governed by atrial compliance, which is most rigorously measured by mathematically fitting atrial pressure and volume data during ventricular systole. A number of studies have shown, however, that the proportion of left atrial inflow during ventricular systole with Doppler pulmonary venous flow (ie, S/D ratios) can estimate relative reservoir function. Thus, we showed that an isolated change in left atrial compliance alters predictably reservoir function and the pattern of pulmonary venous flow. 2 Decreased atrial compliance is associated with greater phasic atrial pressures but a lower mean level of atrial pressure during ventricular filling, and as a result, a smaller end-diastolic volume and decreased venous return. 3 In contrast, increased atrial compliance increases early LV filling and atrial systolic shortening. 4

Left atrial function: evaluation by strain analysis

“…These studies support the hypothesis that atrial functional remodelling and reduced atrial contraction can result in subsequent thromboembolism (8). Therefore, LA strain analysis may provide an invaluable prognostic tool for AF; albeit larger prospective studies in stroke patients are required to confirm these early reports.…”

“…While previously left atrial (LA) size was utilised, the role of LA function as a biomarker is increasingly being evaluated (4), both independently and also in combination with LA size (5-7). However, LA function is complex, comprising of three main components: reservoir function in systole when blood fills the left atrium, as a conduit in early diastole corresponding to passive left ventricular filling and as an active contractile chamber in late diastole (8,9).…”

Assessment of left atrial function in diabetes mellitus by left atrial volume tracking method

“…According to Frank-Starling curve, to a certain extent, LA compensatory contractility and LA ejection force (% LAVIact) are increased at late diastole, which can maintain the normal cardiac output [16][17][18][19][20][21][22] . Muranaka et al [23,24] reported that the LA reserve and channel function of patients with DM were decreased. The possible reason for the diversity was attributed to the follows : (1) The heart change of this group was at the early stage; (2) There was no significant difference in %iLAVIe.…”

Left atrial dyssynchrony assessed by strain imaging in predicting future development of atrial fibrillation in patients with heart failure

“…After cardioversion, peak atrial strain rate during late diastole is a descriptor of atrial function [23]. However the reservoir function of the LA is governed by atrial compliance, which may play an important role in modulating systolic and diastolic function of the LA [24,25]. LA strain and strain rate during ventricular systole reflect atrial distensibility [24] and can be used as an index of LA reservoir function [26].…”