Accentuated left ventricular lateral wall function compensates for septal dyssynchrony after valve replacement for aortic stenosis☆

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Abstract

Background

The interventricular septal motion becomes reversed after aortic valve replacement (AVR) for aortic stenosis (AS) despite maintained stroke volume (SV). We hypothesis that left ventricular (LV) lateral wall compensates for such disturbances, in order to secure normal SV.

Methods

We studied 29 severe AS patients (age 63 ± 11 years, 18 males) with normal ejection fraction (EF) before, 6 months and 12 months after AVR and compared them with 29 age- and gender-matched controls, using speckle tracking echocardiography.

Results

In patients, the LVEF and SV remained unchanged throughout. Before AVR, the septal radial motion, septal and lateral strain were reduced (p < 0.001). Peak septal and lateral displacements, times from QRS to peak displacement were all not different from controls.

Six months after AVR, septal radial motion reversed (p < 0.001), lateral strain increased (p < 0.05), peak septal displacement reduced (p < 0.01) while lateral displacement increased (p < 0.05). Time to peak septal displacement delayed (p < 0.01) in contrast to lateral displacement which became early (p < 0.05), resulting in a significant septal-lateral time delay (p < 0.01). The accentuation of LV lateral wall correlated with septal displacement time delay (r = 0.60, p < 0.001) and septal–lateral time delay (r = 0.64, p < 0.001). SV correlated with lateral displacement (r = 0.39, p < 0.05). The systolic strain was correlated with opposite wall displacement (p < 0.05 for both). There was no correlation between these measurements before and 12 month after AVR.

Conclusions

Accentuated lateral wall displacement compensates for septal dyssynchrony in order to maintain normal LVEF and SV. The continuing recovery of these disturbances 12 months after complete mass regression suggests an ongoing reverse remodeling.

Introduction

Aortic valve replacement (AVR) for aortic stenosis (AS) results in regression of left ventricular (LV) hypertrophy and improvement of overall cardiac pump performance, including diastolic function [1], [2], [3], [4]. However, AVR also results in reversed septal motion which is recognized as anterior movement of the ventricular septum in systole in the presence of preserved systolic wall thickening. We have previously shown that such reversed septal motion is related to the post AVR fall in right ventricular (RV) free wall motion, in order to optimize its pump function [5], [6], in line with previous studies [7], [8]. Such deviation of myocardial power generation from the left to the right ventricle aims at maintaining the latter's systolic function. This however, is potentially bound to deprive the LV from a significant contributor to its overall pumping function. In view of such significant changes in LV function after AVR, we hypothesized that the free wall (lateral) has to compensate for the loss of septal contribution to LV ejection fraction (EF) and stroke volume (SV) after AVR. We aimed therefore, to assess in detail segmental LV function after AVR and determine potential relationships between the septal and LV lateral wall.

Section snippets

Study population

We studied 29 consecutive patients (age 63 ± 11 years, 18 males) with severe AS based on a mean aortic gradient of ≥ 40 mm Hg and/or aortic valve area (AVA) ≤ 1.0 cm2, referred to the Heart Centre of Umeå University Hospital for AVR. This group is part of a previously studied cohort of AS patients [3]. An echocardiographic examination was performed the day before, 6 months and 12 months after AVR. All patients had undergone cardiac catheterization before surgery to exclude significant (> 50%) coronary

Measurements

Measurements of LV cavity dimensions including septal and posterior wall thickness as well as left atrial (LA) dimensions were made using conventional recommendations [10]. LVEF was estimated using biplane Simpson's model. The SV was calculated as the product of LV outflow tract (LVOT) cross sectional area multiplied by its flow velocity time integral (VTI) from the spectral Doppler recordings. LV mass was calculated using the Penn conversion equation [11].

From the apical 4 chamber view, LV

Reproducibility

Intra- and inter-observer variabilities were assessed in 10 randomly chosen subjects for STE LV wall peak displacement and time to peak displacement measurements. Coefficient of variation was calculated as the ratio of the standard deviation of the variables to their corresponding mean from the original data set [12].

Results

Of the 29 patients, 15 (52%) had hypertension, 4 (14%) diabetes and 4 (14%) had previous stroke. All patients had degenerative aortic valve stenosis. Twelve patients proved to have bicuspid aortic valve at the time of surgery. Two patients had paroxysmal atrial fibrillation immediately after AVR, which recovered before hospital discharge. No patient developed bundle branch block or interventricular conduction delay during follow-up. All patients completed the follow up echocardiography protocol

Findings

The main findings of the present study are the decreased LV septal displacement but increased lateral displacement 6 and 12 months after AVR despite unchanged EF and SV. The early post-operative reversed septal motion remained up to 12 months despite its partial recovery. Longitudinal septal displacement became delayed after AVR in contrast to the lateral wall which was earlier, even than controls, resulting in prolonged time delay between the septal and lateral walls at 6 month of AVR. The extent

Conclusion

Surgical valve replacement for aortic stenosis results in reversed radial septal motion, reduced septal systolic function and significant segmental dyssynchrony, particularly when compared with lateral wall timing. The accentuated lateral wall amplitude of displacement and early peaking compensate for septal dyssynchrony, in order to maintain LV stroke volume and EF.

Acknowledgments

The authors of this manuscript have certified that they comply with the Principles of Ethical Publishing in the International Journal of Cardiology.

References (19)

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Cited by (2)

  • Severity of aortic stenosis predicts early post-operative normalization of left atrial size and function detected by myocardial strain

    2013, International Journal of Cardiology
    Citation Excerpt :

    In patients with maintained ejection fraction (EF), LV subendocardial function as shown by long axis function is often abnormal in AS, even in the absence of additional coronary artery disease. Aortic valve replacement (AVR) results in significant recovery of LV function [3–5], although residual abnormalities may remain [6,7]. Furthermore, recent studies have shown that the extent of irreversible LV dysfunction in the form of reduced myocardial strain rate reserve correlate with the impaired exercise capacity these patients have after AVR [8].

  • Systolic heart function remains depressed for at least 30 days after on-pump cardiac surgery

    2012, Interactive Cardiovascular and Thoracic Surgery
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Grant: Dr. Zhao is partially supported by the Swedish Heart and Lung Foundation and Umeå University.

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