Compensatory increase of left atrial external work to left ventricular dysfunction caused by afterload increase

Abstract

Inoue K, Asanuma T, Masuda K, Sakurai D, Higaki J, Nakatani S. Compensatory increase of left atrial external work to left ventricular dysfunction caused by afterload increase. Am J Physiol Heart Circ Physiol 308: H904 -H912, 2015. First published January 30, 2015 doi:10.1152/ajpheart.00530.2014.-Afterload mismatch can cause acute decompensation leading to an occurrence of acute heart failure. We investigated how the left atrium (LA) and left ventricle (LV) react to acute increases in afterload using speckle tracking echocardiography (STE). LA strain and volume were obtained by STE in 10 dogs during banding of descending aorta (AoB). Simultaneously, LA pressure was measured by a micromanometer-tipped catheter. LA peak negative strain during LA contraction, strain change during LA relaxation (early reservoir strain), and that during LA dilatation (late reservoir strain) were obtained from LA longitudinal strain-volume curves. From pressure-strain curves, the areas of A-loop and V-loops were computed as the work during active contraction and relaxation (A-work) and that during passive filling and emptying (V-work). AoB increased LV systolic pressure (105 Ϯ 15 vs. 163 Ϯ 12 mmHg, P Ͻ 0.01) and mean LA pressure (3.8 Ϯ 1.2 vs. 7.1 Ϯ 2.0 mmHg, P Ͻ 0.01). LV global circumferential strain decreased (Ϫ18.8 Ϯ 3.5 vs. Ϫ13.2 Ϯ 3.5%, P Ͻ 0.01), but LV stroke volume was maintained (8.4 Ϯ 2.3 vs. 9.6 Ϯ 3.6 ml). LA peak negative strain (Ϫ2.9 Ϯ 2.3 vs. Ϫ9.8 Ϯ 4.0%, P Ͻ 0.01) and early reservoir strain (4.5 Ϯ 2.1 vs. 7.7 Ϯ 2.4%, P Ͻ 0.05) increased by AoB, but late reservoir strain did not change (8.9 Ϯ 3.4 vs. 6.1 Ϯ 3.4%). A-work significantly increased (3.2 Ϯ 2.0 vs. 19.2 Ϯ 15.1 mmHg %, P Ͻ 0.01), whereas V-work did not change (13.3 Ϯ 7.1 vs. 13.1 Ϯ 7.7 mmHg %). In conclusion, LA external work during active contraction and relaxation increased as compensation for LV dysfunction during aortic banding. Atrial dysfunction may lead failure of this mechanism and hemodynamic decompensation. atrial function; speckle tracking echocardiography; external work ACUTE HEART FAILURE IS A MAJOR cause of hospitalizations and is associated with significant mortality (8, 9). The process of transition from asymptomatic to overt heart failure is complex and incompletely understood. Increased afterload is one of the key triggers for the sudden onset of life-threatening pulmonary edema. An acute increase of blood pressure results in a preload recruitment to maintain left ventricular (LV) stroke volume according to the Frank-Starling mechanism (21), and the left atrium (LA) immediately reacts to the hemodynamic overload by enhancing LA contraction and relaxation. Accordingly, the failure of LA adaptation leads to a decompensated state of heart failure (15).Echocardiography plays an important role in the assessment of LA structure and function. In an experimental study, Barbier et al.(1) measured LA reservoir function by calculating the expansion rate of the LA area with automated border detection echocardiography. That study identified the determinant...

Incremental value of left atrial active function measured by speckle tracking echocardiography in patients with hypertrophic cardiomyopathy

“…Notably, LA active strain, which corresponds to active contraction and relaxation, was also associated with these cardiac events, and this was independent of and incremental to age, gender, E/e′, LV GLS, and maximal LAVI. In our previous experimental study, LA active contraction and relaxation played an important role to maintain stroke volume during afterload increase in the experimental model . In patients with HCM, these LA active functions become worse in parallel with advanced LV hypertrophy because the burden of atrial preload and afterload is thought to drive the progression of atrial remodeling .…”

“…In our previous experimental study, LA active contraction and relaxation played an important role to maintain stroke volume during afterload increase in the experimental model. 20 In patients with HCM, these LA active functions become worse in parallel with advanced LV hypertrophy because the burden of atrial preload and afterload is thought to drive the progression of atrial remodeling. 21 In fact, the current study found that LA active strain was inversely asso-…”

Echocardiographic Assessment of Atrial Function: From Basic Mechanics to Specific Cardiac Diseases

“…The A-loop area represents LA active function to maintain stroke volume and normal LA pressure despite afterload increase [ 9 ]. Although an increase in afterload limits LV work, augmentations of LA pump function (booster function) and LA active relaxation (early reservoir function) immediately react as compensatory mechanisms to prevent ‘afterload mismatch’ ( Figure 1 B).…”

Clinical Utility of Atrial Electromechanical Conduction Time Measured with Speckle Tracking Echocardiography after Catheter Ablation in Patients with Atrial Fibrillation: A Validation Study with Electroanatomical Mapping

“…Speckle tracking echocardiography was performed with a high frame rate of over 60 frames/sec for the analysis of LA strain parameters using offline software (Ultra Extend; Toshiba Medical Systems, Tochigi, Japan). We used the onset of the P‐wave as the reference point to calculate LA strain according to our previous report . The LA endocardial border was manually and carefully traced in the four‐chamber images.…”

“…We used the onset of the P-wave as the reference point to calculate LA strain according to our previous report. 16 The LA endocardial border was manually and carefully traced in the four-chamber images. After manual adjustment of the region of interest to cover the full thickness of the LA wall, the software automatically divided the LA into six segments.…”