Results
The pre-operative demographic characteristics of the patients are shown in Table 1. A total of 31 patients were included (median age: 59 years; >90% male). Nearly 80% patients had New York Heart Association functional class of >II. Regarding the pre-operative echocardiographic parameters, the mean LV end-diastolic dimension (LVDd) was 67 ± 10 mm, the LV end-systolic dimension (LVDs) was 52 ± 13 mm, the LV end-diastolic volume index (LVEDVI) was 291 ± 104 mL/m2, the LV ESV index (LVESVI) was 98.5 ± 40.2 mL/m2 and LVEF was 42% ± 8%. The aetiology of AR was degenerative disease in 25 (80%) patients, bicuspid valve in 3 (10%) and aortic dilatation in 3 (10%).
All patients underwent the low-dose dobutamine protocol with no complications. No adverse effects were observed, and the 10 µg/kg/min dose was administered in all patients. The comparison of echocardiographic variables at baseline (equally pre-operative) and during DSE with the 10 µg/kg/min dose is shown in Table 2. Both LVEDVI and LVESVI during DSE decreased compared with those at baseline (P = 0.015 and P < 0.001, respectively), and LVEF improved during DSE (P < 0.001). The average ΔLVEF improvement was 8.9%. The systolic blood pressure increased (P < 0.001); however, the diastolic blood pressure did not change during DSE (P = 0.787).
All patients underwent aortic valve surgery. The changes in LV volume (LVEDVI and LVESVI) and LVEF before and after surgery over a median follow-up period of 4.6 (2.7–5.7) years are shown in Figure 1. LV volume and function improved remarkably after surgery.
There were 18 patients with pre-operative LVEF of> 45% and 13 with pre-operative LVEF of <45%. Patients with pre-operative LVEF of> 45% exhibited a significant increase in LVEF (from 47.0 ± 1.3 % to 56.4 ± 5.1 %, P < 0.001) (Figure 2). In contrast, in patients with pre-operative LVEF of <45%, there was no significant difference in LVEF (from 34.5 ± 6.5 % to 38.3 ± 10.4 %, P = 0.179) (Figure 2).
Next, we examined the 13 patients with pre-operative LVEF of <45% using the LDSE data. The receiver operating characteristic curve for improvement of post-operative LVEF indicated the cut-off point as ΔLVEF of 6% during DSE. Of the 13 patients, 7 had ΔLVEF of ≥6% (with contractile reserve, CR) and 6 had ΔLVEF of <6% (without CR). The comparison of echocardiographic variables at baseline (equally pre-operative) and during DSE in patients with and without CR is shown in Table 3. In the patients with CR, there was no change in LVEDVI during DSE (P = 0.54) and LVESVI during DSE decreased compared with that at baseline (P = 0.002). In contrast, neither LVEDVI nor LVESVI changed in patients without CR (P = 0.09 and P = 0.13, respectively).
All patients with CR (n = 7) had improvement in post-operative LVEF (from 33.0 ± 7.0 to 42.6 ± 9.9 %, P = 0.006) (Figure 3). However, in six patients without CR, there was no change in LVEF (from 36.3 ± 6.0 to 33.3 ± 9.4 %, P = 0.426) (Figure 3). Patients with CR during DSE had a predicted improvement of post-operative LVEF with a sensitivity and specificity of 80% and 85%, respectively.