Methods

This was a prospective observational study of consecutive high surgical risk patients with moderate-to-severe or severe MR who underwent percutaneous mitral valve repair with the MitraClip system at our institution from October 2008 to March 2011.

Patients with either degenerative (due to intrinsic valvular disease) or functional (without structural abnormalities of the valve and with primary LV dysfunction) MR were included. Patients with previous surgical or percutaneous aortic prosthetic valve implantation were also included. High surgical risk was established by consensus between a local independent cardiologist and a cardiac surgeon that conventional surgery would be associated with excessive morbidity and mortality. The high-risk criteria included the logistic European System for Cardiac Operative Risk Evaluation ≥20%, the presence of comorbidities not included in the European System for Cardiac Operative Risk Evaluation such as hepatic cirrhosis, systemic autoimmune disease, severe renal failure requiring hemodialysis, or any contraindication to extracorporeal circulation (e.g., pre-existing cancer, pulmonary or cerebral disease), as previously reported.

All enrolled patients underwent transthoracic two-dimensional echocardiography (Philips X5-1 Transducer, Siemens Acuson Sequoia 5V2 Ultrasound Probe, Siemens, Munich, Germany) at 6 months after the procedure of percutaneous mitral valve repair. The evaluated parameters were compared with the baseline echocardiographic assessments. Although the confidence of interpretation concerning mitral valve pathologic features and catheter-clip system location has been shown to be enhanced by combining two- and three-dimensional imaging modalities, the data presented in our study refer exclusively to two-dimensional echocardiography, because only patients enrolled during the past year were evaluated with both two- and three-dimensional echocardiographic imaging technologies. The baseline and follow-up functional status, assessed according to the New York Heart Association criteria, was also reported. The local ethics committee approved the present study, and all patients provided written informed consent.

All echocardiographic assessments were performed by 2 experienced echocardiographers. The presence of MR at baseline was qualified by color Doppler and quantified by the vena contracta width and the proximal isovelocity surface area method in accordance with the American Association of Echocardiography recommendations. All patients were assigned a MR severity score of 1 (mild), 2 (mild to moderate), 3 (moderate to severe), or 4 (severe), according to the quantitative measure of the effective regurgitant orifice area (EROA) and regurgitant volume. The EROA was obtained using the proximal isovelocity surface area method; the area of interest was optimized by lowering the imaging depth and reducing the Nyquist limit to 15–40 cm/sec; the proximal isovelocity surface area radius was measured at mid-systole using first aliasing and EROA was calculated using the standard formula. The regurgitant volume was estimated as the EROA multiplied by the velocity time integral of the regurgitant jet. After the intervention, MR severity was assessed using the technique reported by Foster et al. Device success was defined as clip implantation with reduction of the MR severity score to 2 or less.

To evaluate the LV changes in size and function, the following parameters were considered: LV end-diastolic and end-systolic volume index (LVEDVI and LVESVI, respectively), calculated using the Simpson method from the apical biplane imaging windows; the LV sphericity index, measured using the LV short/long axis dimension ratio in the end-diastolic four-chamber apical view; and the LV ejection fraction, obtained using the biplane Simpson method. Reverse LV remodeling was defined as a decrease of 10% in the LVEDVI. Reverse remodeling of the atrial chamber was evaluated using the left atrial volume index and was measured from a single-plane apical imaging window.

Continuous variables are presented as the mean ± SD or median and interquartile range and were compared using Student’s t test or the Mann-Whitney rank sum test for unpaired comparisons, as appropriate, and the Wilcoxon rank sum test for paired comparisons. The mean differences between the baseline and 6-month echocardiographic parameters are reported. The categorical variables are expressed as counts and percentages and were compared using the χ ² test or Fisher exact test, as appropriate. Correlations between the echocardiographic measurements were tested, and only those statistically significant are reported, providing the Spearman correlation coefficient. Differences were considered statistically significant when P < .05. Statistical analyses were performed using the Statistical Package for Social Sciences, version 17.0 (SPSS, Chicago, IL).

Results

Of the 49 patients undergoing percutaneous mitral valve repair with the MitraClip system, 5 died within 6 months of the procedure of noncardiac causes ( Table 1 ). The 44 patients surviving at the 6-month follow-up point were evaluated in the present analysis. Of the 44 patients, MR was classified as degenerative in 14 and functional in 30 ( Figure 1 ). The clinical baseline characteristics of the overall population and subgroups according to MR etiology are presented in Table 2 . The mean age of all included patients was 71.9 ± 11 years, and for most (84.1%), the New York Heart Association class was III/IV. One clip was implanted in 65.9% of patients, with 2 clips used in the remaining patients. According to the provided definition, in no case was clip implantation unsuccessful.

Study flow diagram.

The patients with functional MR, compared with those with degenerative MR, were more often men (83.3% vs 57.1%, P = .06), more often had diabetes (46.6% vs 0%, P = .002), and had a significantly greater prevalence of LV ejection fraction less than 30% (26.7% vs 0%, P = .04; Table 2 ). In addition, in patients with functional MR, the baseline LVEDVI, LVESVI, and sphericity index were significantly greater than those in patients with degenerative MR ( Table 2 ).

Results at Follow-Up

Regarding left chamber remodeling, in the overall population, the 6-month echocardiograms showed significant reductions in the sphericity index and in the degree of MR compared with the baseline echocardiograms ( Figure 2 ). The individual sphericity index values for all the evaluated patients are shown in Figure 3 A. The 6-month sphericity index correlated positively with the baseline LVEDVI ( r = 0.633, P < .001; Figure 4 ). Significant reductions in LVEDVI and LVESVI were observed ( Figure 5 A,B). The LV ejection fraction increased from 38.0% (interquartile range 30.0–55.0) to 46.0% (interquartile range 35.0–58.0; P < .001), with a more than 5% absolute increase occurring in 48% of the overall population. The individual ejection fraction values of all evaluated patients are shown in Figure 3 B. The pulmonary artery pressure decreased from 45.0 mm Hg (interquartile range 40.0–54.5) to 35.0 mm Hg (interquartile range 33.2–45.0; P < .001). Reverse remodeling, according to the specified definition, was observed in 77.3% of all patients.

(A) Mitral regurgitation degree and (B) sphericity index at baseline and 6 months after the percutaneous procedure. Data are expressed as mean ± SD. Error bars indicate SDs of the mean. Δ = Mean difference ± SD. The baseline and 6-month median and interquartile range of MR degree was 4.0+ (interquartile range 4.0–4.0) to 1.3+ (interquartile range 1.0–2.0), respectively. The baseline and 6-month median and interquartile range of the sphericity index was 0.57 (interquartile range 0.54–0.62) to 0.54 (interquartile range 0.50–0.58), respectively.

(A) Individual sphericity index and (B) ejection fraction before and 6 months after percutaneous mitral valve repair. Circles indicate patients with functional MR; triangles, patients with degenerative MR.

Correlation between 6-month follow-up sphericity index and baseline LVEDVI.

Echocardiographic changes in (A) LVEDVI, (B) LVESVI, and (C) left atrial volume index (LAVI) from baseline to 6 months of follow-up. The central box represents the values from the lower to upper quartile (25th to 75th percentile). The middle horizontal line represents the median (50th percentile). The vertical line extends from the minimum to the maximum value within 1.5 box heights from the top or bottom of the box. Outside values, displayed as separate points, are defined as greater than 1.5 box heights from the top or bottom of the box.

The significant changes detected in the overall population were also confirmed within both the degenerative and the functional MR subgroups ( Table 3 ). The magnitude of the mean differences between the baseline and 6-month LV volumes and sphericity index was greater within the functional than in the degenerative MR group, although statistical significance was reached only for the differences in the LVESVI and LV ejection fraction ( Table 3 ). A 5% absolute increase in the LV ejection fraction was seen in 14.3% and 63.3% of the patients in the degenerative and functional MR subgroups, respectively ( P = .002). A moderate and significant inverse correlation was seen between baseline LVESVI and 6-month LV ejection fraction ( r = 0.54, P = .002) within the patients with functional MR. No significant difference ( P = .31) was found in terms of the pulmonary artery pressure reduction in the two considered subgroups (78.6% in degenerative MR vs 63.3% in functional MR).

Table 3

Baseline and 6-month follow-up echocardiographic parameters within degenerative and functional MR subgroups

Variable	Degenerative MR (n = 14)				Functional MR (n=30)
	Baseline	6-Month follow-up	Difference	P value	Baseline	6-Month follow-up	Difference	P value
MR degree (+)	4.0 (4.0–4.0)	1.0 (1.0–2.0)	−2.4 ± 0.8	.001	4.0 (3.0–4.0)	1.5 (1.0–2.0)	−2.2 ± 0.6	< .001
LVEF (%)	58.0 (55.0–60.0) ∗	60.0 (58.0–60.0)	1.4 ± 2.3 †	.017	30.0 (28.0–38.5) ∗	39.0 (32.0–47.2)	6.7 ± 6.9 †	< .001
LVEDVI (mL/m 2 )	61.3 (55.8–66.3) ∗	48.9 (46.7–54.1)	−12.8 ± 10.2	.001	98.3 (75.5–113.6) ∗	67.7 (57.1–88.0)	−24.1 ± 26.6	< .001
LVESVI (mL/m 2 )	24.7 (22.0–30.8) ∗	19.5 (18.8–22.2)	−5.9 ± 4.7 †	.001	66.1 (48.1–85.7) ∗	42.5 (28.4–63.5)	−21.0 ± 24.1 †	< .001
Sphericity index	0.54 (0.49–0.55) ∗	0.50 (0.46–0.54)	−0.02 ± 0.02	.002	0.60 (0.58–0.66) ∗	0.56 (0.53–0.62)	−0.04 ± 0.04	< .001
LAVI (mL/m 2 )	46.7 (32.8–68.4)	44.3 (30.5–51.9)	−7.8 ± 12.8	.064	54.7 (41.6–63.4)	50.5 (36.3–63.4)	−2.0 ± 16.2	.510
sPAP (mm Hg)	45.0 (40.0–50.7)	35.0 (32.7–42.5)	−7.7 ± 10.7	.025	45.0 (40.0–55.2)	36.5 (33.0–45.0)	−8.8 ± 15.6	.006

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