Clinical Investigation
Left Ventricular Dyssynchrony: Repsonse to Pacing
Effect of Low-Amplitude Two-Dimensional Radial Strain at Left Ventricular Pacing Sites on Response to Cardiac Resynchronization Therapy

https://doi.org/10.1016/j.echo.2010.08.023Get rights and content

Background

Left ventricular (LV) lead placement to areas of scar has detrimental effects on response to cardiac resynchronization therapy (CRT). Speckle-tracking radial two-dimensional strain offers assessment of the extent of regional myocardial deformation. The aim of this study was to assess the impact of LV lead placement at areas of low-amplitude strain on CRT response.

Methods

The optimal cutoff of radial strain amplitude at the LV pacing site associated with an unfavorable CRT response was determined in a derivation group (n = 65) and then tested in a second consecutive validation group (n = 75) of patients with heart failure. Patients had concordant LV leads if placed at the most delayed site, and dyssynchrony was defined as anteroseptal to posterior delay ≥ 130 msec. CRT response was defined as a ≥15% reduction in LV end-systolic volume at 6 months.

Results

In the derivation group, a derived cutoff for radial strain amplitude of <9.8% defined low-amplitude segments (LAS) and had a high specificity but low sensitivity for predicting LV reverse remodeling, suggesting a strong negative predictive value. In the validation group, compared with patients without LAS at the LV pacing site, in patients with LAS (n = 16), CRT response was significantly lower (62.7% vs 31.3%, P < .05). By multivariate analysis, LV lead concordance and the absence of an LAS at the LV pacing site but not dyssynchrony were significantly related to CRT response.

Conclusion

LV lead placement over segments with two-dimensional radial strain amplitudes <9.8% is associated with poor outcomes of CRT.

Section snippets

Patient Population and Study Protocol

One hundred forty patients in sinus rhythm with left bundle branch block (QRS width ≥ 120 msec), NYHA functional class III or IV heart failure, and impaired LV systolic function (LV ejection fraction ≤ 35%) despite receiving maximally tolerated optimal medical treatment were assessed. The study was conducted in two consecutive groups, with hypothesis testing in the first group (n = 65), to derive the optimal cutoff of low-amplitude radial strain that negatively predicted CRT response

Baseline Characteristics and Response to CRT

At baseline, among the entire study population, the mean age was 71 ± 10 years, with a mean LV ejection fraction of 23 ± 7% and a mean QRS duration of 157 ± 22 msec. Baseline characteristics of all patients and a breakdown of patients in the validation and derivation groups are provided in Table 1.

In the entire study population after 6 months of CRT, NYHA class improved in 95 patients (67.9%), was unchanged in 35 patients, and worsened in eight patients. At follow-up, two patients died of

Discussion

In the present study, we report the detrimental effects on CRT response of the presence of LAS as determined by speckle-tracking radial strain analysis, at the site of LV lead placement. We have derived a cutoff value to define LAS and tested this prospectively in a validation group to demonstrate the significance of radial strain amplitude on CRT response. Multivariate regression analysis suggests that even in the presence of significant LV dyssynchrony, a favorable outcome of CRT is dependent

Conclusions

The presence of low-amplitude 2D radial strain at the LV pacing site has detrimental effects on CRT response despite the presence of LV dyssynchrony or pacing of the latest site of contraction. In the prospective identification of the optimal site for LV lead placement, consideration should be given to the amplitude of 2D radial strain as well as the timing of segmental contraction.

Acknowledgments

We wish to thank Addenbrooke’s Charitable Trust, Papworth Hospital Research and Development Department, and Cambridge Biomedical Research Centre, funded by the UK National Institute for Health Research for their support in conducting this work.

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