Usefulness and limitations of contractile reserve evaluation in patients with low-flow, low-gradient aortic stenosis eligible for cardiac resynchronization therapy

Abstract

Aims: In low-flow, low-gradient aortic stenosis (LF/LG AS), the assessment of contractile reserve (CR) by dobutamine stress echocardiography (DSE) is recommended for risk stratification and treatment strategy. However, DSE may show limitations in cases of left ventricular dyssynchrony (LVD). The impact of LVD in LF/LG AS, and the feasibility of CRT in this setting have never been evaluated. We aimed to assess: (i) the proportion of LF/LG AS patients with LVD; (ii) the influence of LVD on CR at DSE; and (iii) the effects of CRT in these patients.

Methods and results: Thirty consecutive patients with LF/LG AS underwent DSE with study of CR. The operative risk for aortic valve replacement (AVR) was assessed using the logistic EuroSCORE. Twenty-one of the 30 patients had LVD. They were significantly older, more symptomatic, had a higher EuroSCORE, and a lower prevalence of CR than those with a narrow QRS (47% vs. 100%, P = 0.009). A CRT pacemaker was implanted in 19 of the 21 patients with LVD. All 19 (except for one patient who died suddenly) experienced significant clinical and echocardiographic improvement. Fourteen CRT patients underwent subsequent AVR with a low event rate. Four CRT patients refused AVR; two of them worsened again 1-2 years post-CRT.

Conclusion: LVD is common in LF/LG AS patients and may be a major mechanism of afterload mismatch, as well as a cause of underdetection of CR. CRT in this population is feasible and may be proposed as a bridge to surgery.

Keywords: Aortic valve stenosis; Cardiac resynchronization therapy; Dobutamine stress echocardiography; Left bundle branch block; Ventricular dysfunction.