Methods

This observational cohort study complies with the Declaration of Helsinki and was approved by the institutional ethics committee. It was conducted in a prospective manner from September 2009 to July 2012, and all patients gave written informed consent before entering the study. Patients with symptomatic MR were included after discussion in the heart team, if eligible for clip placement and unsuitable for cardiac surgery or refusing surgical treatment. Surgical risk was based on the European System for Cardiac Operative Risk Evaluation I (EuroSCORE I) and the Society of Thoracic Surgeons’ risk model (STS Score). Key exclusion criteria were active endocarditis and MV orifice area <4 cm ² . In contrast to the Endovascular Valve Edge-to-Edge Repair Study (EVEREST) trials, we included patients with lateral and medial leaflet pathologies, severe bileaflet prolapse, LVEF <25%, left ventricular end-systolic diameter >55 mm, flail gap ≥10 mm, flail width >15 mm, and coaptation length <2 mm. All patients underwent transthoracic and transesophageal echocardiography before intervention to assess valve morphology, MR severity, and suitability for MitraClip treatment. MR classification was performed according to international guidelines and graded from 1+ to 4+. The baseline and follow-up LVEF was measured echocardiographically by biplane Simpson method. After the clip procedure, transthoracic echocardiography was conducted for measurements before discharge and regular appointed follow-up visits. The clinical outcome was assessed by New York Heart Association (NYHA) classification and 6 minutes walking test (6mWT). All patients were followed by telephone to evaluate their current clinical status and to determine whether a reintervention or valve surgery due to MV dysfunction was performed. In case of patients lost to clinical follow-up, we contacted municipal registry offices to acquire survival data.

All procedures were performed with 2D and 3D transesophageal echocardiography and fluoroscopic guidance as previously described. Procedural success was defined as the implantation of at least 1 clip and a reduction of MR with the goal of maximum MR reduction, and by at least 1 grade. All hemodynamic measurements were performed under general anesthesia before and after clip placement. Left atrial pressure (v-wave) was obtained by a transseptal catheter positioned in the left atrium. Cardiac output was calculated by the Fick method. The primary endpoints were defined as procedural success (MR reduction ≥1 grade) and primary efficacy endpoint composed of death of any cause, MV surgery, second clip procedure, and NYHA class ≥III after clip implantation. In a prespecified analysis of patients with successful clip placement who did not undergo repeat MV intervention, we further analyzed MR grade, NYHA functional class, and distance in the 6mWT at the latest follow-up visit after clip implantation compared to baseline, as secondary outcomes. Postprocedural, hemodynamic-relevant, atrial-septum-defect requiring closure, myocardial infarction, stroke, and septicemia were defined as major cardiovascular events. Ventilation >48 hours, renal failure requiring dialysis, gastrointestinal bleeding, transfusion of ≥2 units of blood, pseudoaneurysm after procedure, and arteriovenous fistula were considered adverse events.

Categorical data are reported as absolute numbers or percentages and were compared using the chi-square test or Fisher’s exact test. Continuous variables are presented as mean ± standard deviations and were compared between the groups using t tests. Survival free of the primary efficacy endpoint and repeat MV intervention and death of any cause are described by Kaplan–Meier curves, and the log-rank (Mantel–Cox) test was used to compare event-free survival. All probability values reported are two-sided, and a p value of <0.05 was considered as statistical significant. Data analysis was performed with IBM SPSS Statistics 21 and GraphPad Prism Version 5.00.

Results

One hundred forty-seven consecutive patients were intended to be treated by pMVR from September 2009 to June 2012. In 11 of these patients (7.5%), a clip could not be placed (for further details, see Figure 1 ). In the remaining 136 patients, at least 1 clip was placed, but in 6 of these patients (4.4%), a sufficient MR reduction of ≥I grade could not be achieved. Therefore, the acute success rate in this patient population was 88.4%. The patient population with at least 1 clip placed was defined as the study population for subsequent analyses. Baseline demographic, clinical characteristics, and number of implanted clips are provided in Tables 1 and 2 , analyzed according to LVEF ≤30% (group 1) versus >30% (group 2). Concerning co-existing conditions, patients with LVEF ≤30% had more often coronary artery disease, previous myocardial infarction, previous coronary artery bypass grafting, renal insufficiency, more electrical devices, secondary MR, and greater calculated surgical risk scores. A similar mean acute MR reduction was seen in the analyzed patients with LVEF ≤30% versus >30%. Both groups showed a similar increase in cardiac output and a reduction in the left atrial v-wave and pulmonary artery pressure ( Table 3 ).

Study flow chart of enrollment and follow-up.

One hundred twenty-seven patients (93.4%) were followed up to 3 years with a median of 371 days (27 to 1,047 days). Considering the composite endpoint with freedom from death, repeat MV intervention, and/or NYHA class ≥III, there was no statistical difference between the groups (p = 0.719; Figure 2 ). Sixteen patients died during the follow-up period. There were more deaths in the patients in group 1 than in those in group 2, but with no statistical difference (7 of 42 patients died in group 1 vs 9 of 94 patients in group 2, respectively; p = 0.279; Figure 3 ): 7 of these deaths were adjudicated as cardiac: 3 of those died during the index hospital stay (clip procedure was performed as a bailout situation in cardiogenic shock), 1 patient died at the first postoperative day after MV replacement (which was performed because of MR recurrence 243 days after index clipping), and 3 patients because of terminal heart failure or sudden cardiac death (in domestic setting); 5 patients died of unknown cause; and 3 because of fulminant pneumonia, 1 of those related to the clip procedure (after thromboembolic stroke, the patient acquired a fulminant pneumonia and died during index hospitalization) and 1 patient because of fibrosarcoma (for details regarding groups 1 and 2, see Figure 1 and Table 4 ). With regard to repeat MV intervention, 2 of 42 patients with LVEF ≤30% underwent a second clip procedure because of MR recurrence (after 66 and 245 days after index clipping, respectively), whereas 4 of 94 patients with LVEF >30% needed a second clip procedure (3 procedures were done because of partial clip detachment after 2, 8, and 49 days, respectively; whereas 1 procedure was performed because of MR recurrence 198 days after index clipping). During the follow-up, 6 patients in group 2 needed MV surgery (MV replacement in 3 patients and MV repair in 3 patients), whereas no one in group 1. The reasons for surgery were (1) perforation of the posterior MV leaflet (associated with the clip implantation, 1 day after index clipping), (2) partial clip detachment (287 and 300 days after index clipping), and (3) MR recurrence ( Figure 1 and Table 4 ).

Primary efficacy endpoint. Kaplan–Meier estimates freedom from death of any cause, reintervention, switch to mitral valve surgery, and/or NYHA functional class ≥III. Black line indicates entire study population, red line indicates patients with ejection fraction (EF) ≤30%, and blue line indicates patients with EF >30%.

Death of any cause. Kaplan–Meier estimates freedom from death of any cause. Black line indicates entire study population, red line indicates patients with EF ≤30%, and blue line indicates patients with EF >30%.

Table 4

Endpoints and adverse events

	Entire study population (n=136)	Ejection fraction		p value
		≤ 30% (n=42)	> 30% (n=94)
Primary efficacy endpoints
Composite endpoint (death of any cause, reintervention/switch to surgery and/or NYHA class ≥ III)	51 (38%)	13 (31%)	38 (40%)	0.719
Secondary endpoints
Death of any cause	16 (12%)	7 (17%)	9 (10%)	0.279
In-hospital death after index clipping	5 (4%)	2 (5%)	3 (3%)	0.387
Second clip procedure	6 (4%)	2 (5%)	4 (4%)	0.756
Switch to mitral valve surgery	6 (4%)	0	6 (6%)	0.094
MR grade ≥ III directly post clipping,	11 (8%)	1 (2%)	10 (11%)	0.092
MR grade ≥ III at a median of 411 days	23 (26%)	4 (17%)	19 (30%)	0.528
(Major) Adverse Events at 30 days	57 (42)	20 (48)	37 (39)	0.069
Clip related perforation of mitral valve leaflet	1 (1)	0	1 (1)
Clip related chordal rupture	0	0	0
Pericardial effusion/tamponade	0	0	0
PM/ICD/CRT lead displacement	0	0	0
Stroke	2 ∗ (2%)	1 ∗ (2%)	1 (1%)
Myocardial infarction (thromboembolic)	1 (1%)	1 (2%)	0
Mechanical ventilation > 48 h	12 (9%)	4 (10%)	8 (9%)
ASD requiring closure	5 † (4%)	2 (5%)	3 † (3%)
Infection	5 (4)	3 (7%)	2 (2%)
Transfusion of ≥ 2 IU blood	10 (7%)	2(5%)	8 (9%)
Pseudoaneurysm	3 (2%)	0	3 (3%)
AV-fistula, n (%)	5 (4%)	0	5 (5%)
Post-procedural ICU – stay [days]	3.7 ± 6.4	5.6 ± 8.1	2.9 ± 5.3	0.05
IABP	12 (9%)	6 (14%)	6 (6%)	0.133

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