Methods

The study population included 27 consecutive patients who had undergone TAVI with the Medtronic-CoreValve and had transthoracic echocardiograms of adequate quality available before and after the procedure. The inclusion and exclusion criteria for TAVI have been previously described in detail. In brief, the patients were included if they had severe native aortic valve stenosis with an aortic valve area <1 cm ² or <0.6 cm ² /m ² , with or without aortic regurgitation, and were deemed high-risk surgical candidates. All patients provided written informed consent (postmarketing surveillance registry). The Medtronic-CoreValve System consisted of a trileaflet porcine pericardial tissue valve, mounted in an hourglass-shaped, self-expanding nitinol frame (50 to 51 mm high). Currently, the prosthesis is available in sizes with a 26- and 29-mm inflow diameter for patient annulus diameters of 20 to 27 mm.

We obtained 12-lead electrocardiographic tracings in all patients before and after treatment and analyzed them for rhythm, heart rate, PR interval duration, QRS duration and morphology, and the presence of atrioventricular/fascicular block, according to recent recommendations. In addition, an electronic single-lead rhythm strip was continuously recorded during the echocardiographic studies. The patients were considered to have new conduction abnormalities when a new LBBB or a new paced rhythm was recorded after the index procedure. The decision to implant a permanent pacemaker was determined according to the latest guidelines.

Two-dimensional transthoracic echocardiography was performed by an independent experienced echocardiographer the day before and 1 week after the procedure, using a commercially available system (iE33, Philips, Best, The Netherlands) with the patient in the left lateral decubitus position, according to published recommendations. All echocardiograms were saved as video loops or still frames in a digital database and were analyzed by a second independent investigator. The LVEF was calculated using the biplane modified Simpson rule. The transaortic peak velocity, peak and mean gradient, and velocity-time integral were measured using continuous-wave Doppler through the native or prosthetic aortic valve. The aortic valve area was estimated using the continuity equation approach [aortic valve area = LV outflow tract area × (velocity-time integral LV outflow tract/velocity-time integral valve)]. Aortic regurgitation and mitral regurgitation were assessed semiquantitatively according to the current guidelines for the evaluation of native valves.

STE was performed using 2-dimensional grayscale harmonic images at a frame rate of 70 to 80 frames/s. The data sets were transferred to a QLAB workstation for analysis using the QLAB Advanced Quantification Software, version 6.0 (Philips, Best, The Netherlands). The details regarding speckle tracking analysis have been previously published. For the purposes of the present study, systolic mitral annular velocities and longitudinal wall strain were assessed from the inferoseptal and anterolateral sides of the left ventricle (from the base to the distal part of the particular wall) in an apical 4-chamber view. The interobserver variabilities were 3.7 ± 3.3% and 4.8 ± 5.2%.

The continuous variables are presented as the mean ± SD, and the categorical variables are presented as frequencies and percentages. For the comparisons between 2 time points, a paired sample t test or Wilcoxon signed rank test for 2 related samples was used for normally distributed or skewed data, respectively. For ordinal variables (aortic regurgitation and mitral regurgitation grade), a constant difference between values was assumed. A 2-sided p value of <0.05 was considered statistically significant. All statistical analyses were performed using the Statistical Package for Social Sciences, version 17.0, software (SPSS, Chicago, Illinois).

Results

The baseline patient characteristics are summarized in Table 1 . The study population consisted of elderly patients with a number of co-morbidities. Of the 27 patients, 4 (15%) had a baseline EF of ≤35%; 8 patients (30%) underwent TAVI using a 26-mm and 19 (70%) using a 29-mm inflow Medtronic-CoreValve. Postdeployment balloon dilation was performed in 3 patients (11%). No patient required a second bioprosthesis as a valve-in-valve bailout.

Before TAVI (1 day before), no patient had a paced rhythm, 1 patient (4%) had a LBBB, and 4 patients (15%) had a left anterior fascicular block. After TAVI (day 6), 4 patients (15%) had a paced rhythm, 15 patients (56%) had a LBBB (14 patients [52%] with a new LBBB), and no patient had a left anterior fascicular block. Therefore, 18 patients (67%) had new conduction abnormalities. With respect to the baseline characteristics, a comparison between the patients with and without new conduction abnormalities did not reveal statistically significant differences. The indication for permanent pacemaker implantation was (in all 4 cases) complete heart block.

The echocardiographic changes after TAVI are listed in Table 2 . The mean transaortic gradient decreased from 44 ± 14 to 9 ± 3 mm Hg, and the aortic valve area increased from 0.62 ± 0.20 to 1.65 ± 0.38 cm ² (p <0.001). A small, nonsignificant decrease in aortic regurgitation and mitral regurgitation severity was observed. Overall, the EF and longitudinal strain did not change significantly; however, the systolic mitral annular velocities improved. The results of a subgroup analysis of LV systolic parameters in relation to new conduction abnormalities are listed in Table 3 . In patients with new conduction abnormalities, the EF decreased from 47 ± 12% to 44% ± 10%. In contrast, in those without new conduction abnormalities, the EF increased from 49 ± 12% to 54% ± 12% ( Figure 1 ). The change in the EF was significantly different among the patients with and without new conduction abnormalities (p <0.05). In addition, in patients without new conduction abnormalities, an improvement was found in the systolic mitral annular velocities and longitudinal strain (p <0.05). In contrast, in patients with new conduction abnormalities, the changes were not significant. In the 4 patients with an EF of ≤35% at baseline, the EF increased from 29 ± 6% to 34% ± 8% (p = 0.28)

Changes in EF after TAVI. Overall, EF did not change significantly after TAVI (black line). In patients without new conduction abnormalities (blue doted line) , the EF increased but in those with new conduction abnormalities (green doted line) , EF decreased. The change in EF was significantly different among patients with and without new conduction abnormalities (paired sample t test, 2-sided, p <0.05).

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