Discussion
In this study, we performed DSE in patients with severe AR and reduced LVEF (pre-operative LVEF < 50%), for whom surgery was indicated. We found that patients with pre-operative LVEF of> 45% exhibited a significant increase in LVEF; however, patients with pre-operative LVEF of <45% showed no change in LVEF. When we examined the results of DSE performed in patients with pre-operative LVEF of <45%, ΔLVEF of ≥6% (with CR) during DSE was related to an improvement in post-operative LVEF.
Previous studies have shown that the long-term outcomes after AVR in patients with a low pre-operative LVEF are poor.15-17 Patients with reduced LVEF are often considered at very high risk of AVR, and some are denied surgery because they are thought to be at an irreversible worsening stage. However, a recent study revealed that a low pre-operative LVEF for AVR was associated with lower mortality than medical therapy.6 The post-operative echocardiographic parameters (LVDd, LVDs and LVEF) are important predictors of long-term cardiac death.7 In addition, some studies have shown that pre-operative LVEF does not correlate with the post-operative LVEF. Even when the pre-operative LVEF is depressed, the LVEF of some patients recovered after surgery and the long-term prognosis after AVR is not affected by pre-operative LV dysfunction.18 19 Therefore, it is clinically important to assess the viability and to identify the predictors of post-operative LV remodeling in patients with reduced pre-operative LVEF.
Some studies have focused on the effect of pre-operative status on recovery of LV function. Cho et al. demonstrated that an LVDs index of <35.3 mm/m2 and an LVDd index of <44.2 mm/m2 were associated with normalised LVEF (LVEF > 50%) in 79 patients with severe AR who underwent AVR. However, in this study, 62 out of 79 patients had pre-operative LVEF of >50%.20Furthermore, as for stress echocardiography for AR, CR by exercise echocardiography has been shown to be a prognostic value for post-operative LV function and clinical outcome in asymptomatic or mildly symptomatic patients with severe AR and preserved LVEF at rest.21 This exercise stress echocardiography also included patients with preserved LVEF. There are few studies regarding the predictions for post-operative LV remodeling that focus on patients with reduced pre-operative LVEF.
DSE is an established tool for detecting myocardial viability8 in various diseases, including chronic heart failure or aortic stenosis.9-11 However, there are few reports about DSE in patients with severe AR. Tam et al. studied 16 patients who underwent elective surgery for AR and had echocardiograms obtained at baseline and with 7.5 µg/kg/min dobutamine.22 This study included patients with preserved or reduced LVEF; however, the authors concluded that LVEF during DSE was highly predictive of post-operative LVEF. DSE may therefore have a role in predicting the clinical outcomes of patients following AVR for AR. Marcia et al. performed DSE (20 µg/kg/min) in 24 patients with AR and preserved LVEF (mean LVEF, 62.3%).23However, they found that the percentage increase in LVEF under DSE did not predict the need for surgery and/or death. Unlike our study, this study included patients with preserved LVEF. Therefore, DSE may be better at identifying patients who already require surgery and are at a more advanced stage than asymptomatic or minimally symptomatic patients. These findings support our results that DSE may be a helpful tool for predicting post-operative reverse remodeling in patients with severe AR and, particularly, more progressive, decreased LVEF.
Our study is one of the few to investigate the usefulness of DSE in patients with severe AR and reduced LVEF and to show cut-off values for contractile reserve for the improvement of post-operative LVEF.