Septal Flash-like Motion of the Earlier Activated Ventricular Wall Represents the Pathophysiology of Mechanical Dyssynchrony in Single-Ventricle Anatomy

Echocardiographic Patterns of Abnormal Septal Motion: Beyond Myocardial Ischemia

Abnormal septal motion (ASM), which often is associated with myocardial ischemia, is also observed in other diseases. Owing to the position of the interventricular septum (IVS) in the heart, its movement not only relies on contractile properties but is also affected by the pressure gradient between the 2 ventricles and by the mode of electrical activation. Echocardiography allows the operator to focus on the motion of the IVS, analyzing its characteristics and thereby gaining information about the possible underlying pathophysiological mechanism. In this review, we focused on the main echocardiographic patterns of ASM that are not related to a failure of contractile properties of the septum (i.e., acute coronary syndrome and cardiomyopathies), showing their pathophysiological mechanisms and underlining their diagnostic usefulness in clinical practice.

The Evolution of Longitudinal Strain Across Various Univentricular Morphologies Prior to Superior Cavopulmonary Anastomosis

BACKGROUND

Infants with single-ventricle physiology have increased morbidity, mortality, and ventricular dysfunction in the pre-superior cavopulmonary anastomosis (pre-SCPA) period. Echocardiography-derived longitudinal strain (LS) is emerging as a reliable marker of single-ventricle performance. We aim to assess evolution of LS during the pre-SCPA period across univentricular morphologies and explore associations of LS with modifiable and nonmodifiable factors.

METHODS

Ninety-four term infants (36 females) with univentricular physiology who were discharged home prior to stage 2 palliation were serially analyzed for LS (single apical view) and other echo measures at initial hospital discharge and the last pre-SCPA encounter. Ventricular myocardium was tracked for strain along the septum and respective lateral wall for single right ventricular (RV) and left ventricular (LV) groups, and along both right and left lateral walls in functionally univentricular hearts with biventricular (BiV) morphology. Clinical data were obtained from the medical record.

RESULTS

Longitudinal strain improved in the total cohort during the pre-SCPA period (16.48% ± 3.31% to 17.57% ± 3.81%, P = .003). Longitudinal strain improved between encounters in the single LV (P = .04) and BiV groups (P = .02). However, LS failed to improve in the RV group (P = .7) with lower LS at both visits compared with the other groups. The RV group, mostly composed of hypoplastic left heart syndrome patients-87% of cases-had a higher incidence of arrhythmias (57%) and unplanned reinterventions (60%), most of which were arch reinterventions. A subanalysis based on arch reintervention showed that LS improves between encounters in the single LV group needing arch reintervention (P = .05) compared with the single RV group needing arch reintervention (P = .89). Lower LS was independently associated with unplanned reinterventions at both encounters (P = .008 and .02).

CONCLUSIONS

Single-ventricle LS evolves differently across ventricular morphologies during the pre-SCPA period and is related to the need for unplanned cardiac reinterventions. Lower LS is noted in the single RV group, who mostly have hypoplastic left heart syndrome.

The Influence of Atrial Strain on Functional Capacity in Patients with the Fontan Circulation

Speckle-tracking echocardiography has been used to assess atrial function. This analysis is feasible in univentricular hearts. The aim of this study was to characterize the relationship between atrial strain and functional capacity in the Fontan circulation. Apical four-chamber echocardiographic loops of 39 Fontan patients were reviewed. The dominant atrium was assessed for active (ε_act), conduit (ε_con), and reservoir (ε_res) strain and ε_act/ε_res ratio. Cardiopulmonary exercise test was performed on the same day and oxygen uptake (VO₂) at ventilatory threshold (VT) and peak VO₂ were chosen as the dependent variables. Statistical analysis was performed using SPSS^® version 23. Unpaired t test was used for binomial and continuous variable correlation; single and multivariable linear regression were used for continuous variable correlation. Statistical significance was defined as p value < 0.05. VO₂ at VT as a percentage of predicted VO₂ was 36.8% (SD 10.7). Peak VO₂ was 64.7% (SD 18.9) of the predicted value. In univariate analysis, both were associated with age, atrioventricular regurgitation, ejection fraction, ε_res, ε_con, and ε_act/ε_res. In multivariate regression, higher VO₂ at VT and peak VO₂ were associated with younger age (p = 0.003 and p = 0.001, respectively) and higher ε_con (p = 0.026 and p = 0.020). Evaluation of heart function is difficult in the Fontan circulation, hindered by complex ventricular morphology and lack of normative data. VO₂ provides a good surrogate. Atrial strain parameters are compromised in these patients and associated with VO₂. Therefore, whenever possible, atrial strain should be measured as it may provide a new method of risk stratification.

Impact of delayed ventricular wall area ratio on pathophysiology of mechanical dyssynchrony: implication from single-ventricle physiology and 0D modeling

Electrical disparity can induce inefficient cardiac performance, representing an uncoordinated wall motion at an earlier activated ventricular wall: an early shortening followed by a systolic rebound stretch. Although regional contractility and distensibility modulate this pathological motion, the effect of a morphological factor has not been emphasized. Our strain analysis in 62 patients with single ventricle revealed that those with an activation delay in 60-70% of ventricular wall area suffered from cardiac dysfunction and mechanical discoordination along with prolonged QRS duration. A computational simulation with a two-compartment ventricular model also suggested that the ventricle with an activation delay in 70% of the total volume was most vulnerable to a large activation delay, accompanied by an uncoordinated motion at an earlier activated wall. Taken together, the ratio of the delayed ventricular wall has a significant impact on the pathophysiology due to an activation delay, potentially highlighting an indicator of cardiac dysfunction.