Speckle-Tracking Strain Imaging Identifies Alterations in Left Atrial Mechanics With General Anesthesia and Positive-Pressure Ventilation

Exploration of the Utility of Speckle-Tracking Echocardiography During Mechanical Ventilation and Mechanical Circulatory Support

This narrative review aims to discuss the potential applicability of speckle-tracking echocardiography (STE) in patients under mechanical ventilation (MV) and mechanical circulatory support (MCS). Both its benefits and limitations were considered through critical analyses of the current available evidence.

Left atrial contraction strain and controlled preload alterations, a study in healthy individuals

Background

In order to assess left atrial contractile function in disturbed circulatory conditions, it is necessary to have a clear understanding of how it behaves in a normal resting state with changes in loading conditions. However, currently the understanding of this relationship is incomplete. We hypothesize that in healthy individuals, left atrial contraction strain and its peak strain rate are increased or decreased by increasing or decreasing preload, respectively.

Methods

Controlled maneuvers used to change preload included continuous positive airway pressure by mask (CPAP 20 cmH₂O) for preload decrease, and passive leg raise (15 degrees angle) for preload increase. Cardiac ultrasound 4-chamber views of the left atria and left ventricle were acquired at baseline and during maneuver. Acquired images were post processed and analyzed offline. Comparisons were made using paired t-test and means with 95% confidence interval.

Results

There were 38 participants, complete results were obtained from 23 in the CPAP maneuver and 27 in the passive leg raise maneuver. For the CPAP group, left atrial contraction strain was 11.6% (10.1 to 13.1) at baseline and 12.8% (11.0 to 14.6) during the maneuver (p = 0.16). Left atrial contraction peak strain rate was − 1.7 s^− 1 (− 1.8 to − 1.5) at baseline and − 1.8 s^− 1 (− 2.0 to − 1.6) during the maneuver (p = 0.29). For the passive leg raise-group, left atrial contraction strain was 10.1% (9.0 to 11.2) at baseline and 10.8% (9.4 to 12.3) during the maneuver (p = 0.28). Left atrial contraction peak strain rate was − 1.5 s^− 1 (− 1.6 to − 1.4) at baseline and − 1.6 s^− 1 (− 1.8 to − 1.5) during the maneuver (p = 0.29). Left atrial area, an indicator of preload, increased significantly during passive leg raise and decreased during CPAP.

Conclusion

In healthy individuals, left atrial contraction strain and its peak strain rate seem to be preload-independent.

Trial registration

The study was 2018-02-19 registered at clinicaltrials.gov (NCT03436030).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12947-022-00278-1.

Atrial function in the Fontan circulation: comparison with invasively assessed systemic ventricular filling pressure

Abnormal atrial mechanics in biventricular circulations have been associated with elevated left heart filling pressures. Similar associations in the Fontan circulation are unknown. The aim of this study was to examine the relationship between atrial mechanics and invasively assessed hemodynamic parameters late after the Fontan operation. Thirty-nine Fontan patients with echocardiographic and invasive hemodynamic studies done within 48 h were included and were compared to 40 age-matched healthy controls. Atrial and ventricular strain measurements were measured offline using 2-dimensional speckle-tracking. Mean age was 10.2 ± 6.7 years and 24 (62%) were male. Atrial strain measures were lower in Fontan patients compared to healthy controls. There was no significant association between atrial strain measurements and Fontan systemic ventricular filling pressures (SVFP) as indicated by pulmonary artery occlusion pressures, direct left atrial pressure or systemic ventricular end-diastolic pressure. Global atrial strain was not correlated with segmental atrial strain in the pulmonary venous atrium. Global atrial reservoir strain was positively correlated with pulmonary vascular resistance (r = 0.508, p = 0.045). Global atrial conduit strain was positively correlated with E/A ratio of the AV valve inflow (r = 0.555, p = 0.002). Atrial and ventricular strain measurements were not significantly correlated. In patients with a Fontan, global atrial function is significantly depressed, and is uncoupled from segmental left lateral atrial function. Global as well as segmental atrial mechanics are not significantly associated with SVFPs in Fontan patients. Instead, global atrial reservoir function appears to parallel pulmonary vascular resistance.

Load Dependency of Left Atrial Strain in Normal Subjects

BACKGROUND

Left atrial (LA) longitudinal strain is a novel parameter used for the evaluation of LA function, with demonstrated prognostic value in several cardiac diseases. However, the extent of load dependency of LA strain is not well known. The aim of this study was to evaluate the impact of acute changes in preload on LA strain, side by side with LA volume, in normal subjects.

METHODS

Twenty-five healthy volunteers (13 men; mean age, 31 ± 2 years) were prospectively enrolled, who underwent two-dimensional and three-dimensional echocardiographic imaging during acute stepwise reductions in preload using a tilt maneuver: baseline at 0°, followed by 40° and 80°. Left ventricular and LA size and function parameters were measured using standard methodology, and LA strain-time curves were obtained using speckle-tracking software (TomTec), resulting in reservoir, conduit, and contractile strain components. All parameters were compared among the three loading conditions using one-way analysis of variance for repeated measurements.

RESULTS

Although there were no significant changes in blood pressure, heart rate increased significantly with tilt. As expected, LA volumes, left ventricular volumes, and left ventricular ejection fraction, as well as E wave, A wave, and e' significantly decreased with progressive inclination. In parallel, LA reservoir, conduit, and contractile strain values decreased with reduction in preload (reservoir: 42.9 ± 3.9% to 27.5 ± 3.8%, P < .001; conduit: 29.3 ± 2.7% to 20.2 ± 5.0%, P < .001; contractile: 13.6 ± 2.9% to 7.3 ± 3.5%, P < .001). Paired post hoc analysis showed that all LA strain values were significantly different among all three tilt phases. Of note, percentage change in LA reservoir strain was significantly smaller than that in LA maximum volume.

CONCLUSIONS

In normal subjects, LA strain is preload dependent but to a lesser degree than LA volume. This difference underscores the relative advantage of LA strain over maximum volume, when LA assessment is used as part of the diagnostic paradigm.