The study was approved by the ethics board of Fuwai Hospital, Chinese Academy of Medical Sciences (No. 2021-1530). All patients and legal guardians signed informed consent for the operation and clinical record review.

This present retrospective, observational, cohort study was conducted at Fuwai Hospital. Data were collected from patients with symptomatic MR who underwent TEER with MitraClip guided solely by TEE or TTE from April 2021 to August 2021. Baseline assessment encompassed demographics, symptoms, comorbidities, routine laboratory testing, risk evaluation, electrocardiogram findings, and TTE results. The heart team, comprising of multidisciplinary experts, evaluated all patients to determine their suitability for TEER according to the current guidelines [13]. Subsequently, patients with contraindications to radiation or contrast agents, such as those with a history of malignant tumors, pregnancy, severe renal failure, or known allergies to contrast agents, were further screened for potential eligibility for PAN procedure via TEER.

All procedures were performed in the operating room under general anesthesia in a supine position. The working distance was determined as the distance from the puncture point to the third intercostal space on the right side of the sternum. A 10 Fr arterial sheath was introduced through femoral vein puncture. An MPA2 catheter and the super-stiff guide wire were inserted according to the working distance. Echocardiography was used to visualize the bi-atrial view at 90 degrees, monitoring the guide wire as it entered the right atrium from the inferior vena cava. The inserted length of the MPA2 catheter was marked after the guide wire reached the atrial septum, allowing for correction of the working distance. The SL1 puncture catheter was inserted at the working distance along the guidewire. The puncture needle was then inserted. By rotating the puncture catheter, a tent-like protrusion was created on the interatrial septum, with the puncture made posterior to the fossa ovalis (Fig. 1A, Video 1). The puncture position was adjusted under ultrasound X-plane guidance. The puncture point was at least 4.0 cm away from the mitral valve annulus. Normal saline was injected to perform contrast-enhanced echocardiography, with microbubbles filling the left atrium to confirm successful trans-septal puncture. The MitraClip clips (CDS0601-XTR or CDS0601-NTR, Abbott, Chicago, IL, USA) were pre-installed. The clip delivery system (CDS) with the working distance mark was introduced into the guide catheter. For navigating to the annulus, a three-dimensional (3D)-view was utilized to visualize the structure of the left atrium. Then the CDS was oriented perpendicularly to the long axis of the leaflet edges under the 3D-view guidance (Fig. 1B, Video 2). Meanwhile, the bi-commissural view was also used to monitor the direction of the CDS. Then, the clip was advanced into the left ventricle just below the mitral leaflet edges, as visualized by the left ventricular (LV) outflow tract and apical two-chamber view. Leaflet grasping, leaflet insertion, and MR assessment were performed in a standard fashion (Fig. 1C). Deployment of more than one MitraClip device was allowed if necessary.

Fig. 1.

TEE guided TEER procedures. (A) Tent-like protrusion on the interatrial septum. (B) 3D echocardiogram showing MitraClip CDS in the left atrium (arrow). (C) TEE showing MitraClip clamping anterior and posterior valve leaflets (arrow). TEE, transesophageal echocardiography; TEER, transcatheter edge-to-edge repair; LA, left atrium; LV, left ventricular; 3D, three-dimensional; CDS, clip delivery system.

All patients were admitted to the intensive care unit (ICU) for monitoring and treatment after the procedure. Aspirin therapy was initiated on the second day after the procedure and continued for 6-months.

The operation success rate was defined as the proportion of cases in which the MitraClip device(s) were successfully delivered and deployed. Total procedure time was defined as the duration from anesthesia induction to the removal of the last sheath. Device procedure release time was defined as the time from the initiation of the transseptal procedure to the removal of the clip delivery system.

Follow-up assessments of clinical outcomes and transthoracic echocardiography were conducted during outpatient visits or through phone interviews at 1-, 3-months and 1-year. Cardiac events were carefully recorded.

Continuous variables are presented as means $\pm$ standard deviation, while categorical variables as expressed as percentages. A paired Student’s t-test was utilized to compare specific time point with baseline for continuous variables, while the Wilcoxon signed rank test was employed for categorical variables. Statistical analysis was conducted using SPSS 25.0 for Windows (SPSS Inc., Chicago, IL, USA). A p value of less than 0.05 was considered statistically significant.

Between April 2021 and August 2021, a total of 23 patients successfully underwent TEER with exclusive echo guidance at the Fuwai Hospital. Baseline characteristics are summarized in Table 1. The mean age was 66.1 $\pm$ 12.1 years, with 65.2% being males, and the mean body mass index (BMI) was 24.0. All patients had moderate-to-severe (grade 3+ or 4+) MR, with 91.3% of patients classified as New York Heart Association (NYHA) functional class III or IV. Based on etiologic classification, 7 patients (30.4%) had functional MR (FMR) and 16 (69.5%) had degenerative MR (DMR). Among the patients, 10 (43.5%) had a single A2/P2 lesion, while the remaining patients presented with A1/P1 or A3/P3 lesions. Two patients (8.7%) underwent MitraClip implantation with the support of an intra-aortic balloon pump (IABP) and 4 patients (17.4%) had a history of malignant tumor. Additionally, 14 (60.9%) patients had severe renal failure, and 5 (21.7%) patients had allergies that necessitated the avoidance of contrast agents.

Successful implantation was achieved in all patients, with a mean of 1.4 clips per patient. Among them, 60.9% received 1 implant, while 39.1% received 2 implants. Immediately after the procedure, only 2 patients (8.7%) had residual mild-to-moderate (2+) MR, while the remaining patients demonstrated significant improvement, with MR decreasing to 0+ or 1+ (Table 2). The median total procedural time was 130 (interquartile range, IQR: 90–150) min and the device procedure time was 73 (IQR: 58–100) min. The median length of stay was 6 (IQR: 5–9) days. No complications, such as vascular injury, cardiac tamponade, or MitraClip embolism, were observed in any of the patients.

One patient with posterior mitral valve leaflet clefts and severe esophageal stenosis was successfully treated under TTE guidance alone (Fig. 2A). The procedure was conducted under general anesthesia. The transseptal puncture was performed posterior to the fossa ovalis under the bi-atrial view (Fig. 2B). Subsequently, the pre-installed MitraClip (CDS0601-XTR, Abbott, Chicago, IL, USA) was introduced along the CDS. With TTE guidance, the clip was advanced to the center of the mitral orifice under the inter-commissural view and short-axis view (Fig. 2C,D, Video 3). The arms of the clip were oriented perpendicularly to the long axis of the leaflet edges (Fig. 2E). Then, the clip was advanced into the left ventricle and pulled back until the mitral leaflets were captured (Fig. 2F). Clip orientation was confirmed again at the short-axis view (Fig. 2G, Video 4). Then the device was closed gradually to optimize the reduction of MR. The MR decreased to trace (Fig. 2H) with a mean mitral valve (MV) pressure gradient of 1.9 mmHg. The total procedure time of TTE guidance was 88 min and the device procedure time was 66 min.

Fig. 2.

TTE guided TEER procedure. (A) TTE showed severe MR. (B) The transseptal puncture under the bi-atrial view (arrow). (C–E) The clip (arrow) was advanced under the guidance of TTE. (F) The leaflets were captured by the clip (arrow). (G) Confirming the position of the clip (arrow) under short-axis view. (H) Postprocedural TTE showed MR decreased to traced. TTE, transthoracic echocardiography; MR, mitral regurgitation; LA, left atrium; LV, left ventricle; AO, aorta; TEER, transcatheter edge-to-edge repair.

The changes in MR severity as assessed by echocardiography at baseline, 1-, 3-months, and 1-year are shown in Fig. 3. At 1-month, 59.1% of patients had MR $\le$1+, and 100% of patients had MR $\le$2+, indicating a significant improvement compared to baseline (p 0.001 vs. baseline). Among the 22 patients followed up at 3-months, 63.6% had MR $\le$1+, and 90.9% had MR $\le$2+ (p 0.001 vs. baseline). Among the 21 patients with echocardiographic data available at 1-year, 90.4% had sustained MR reduction with MR $\le$2+ (p 0.001 vs. baseline) (Fig. 3).

Fig. 3.

Change in mitral regurgitation grade up to 1-year follow-up.

Changes in LV volumes, LV ejection fraction (LVEF), and other echocardiographic parameters are shown in Table 3. At 1-month, LV end-diastolic volume decreased from 160.84 $\pm$ 43.97 to 124.42 $\pm$ 39.24 mL (p 0.001), while LV end-systolic volume numerically but not significantly decreased from 69.81 $\pm$ 36.33 to 57.00 $\pm$ 27.60 (p = 0.028). Furthermore, from baseline to 1-month, significant reductions were observed in LV internal diameter during diastole (from 58.76 $\pm$ 5.41 to 51.67 $\pm$ 6.34, p 0.001), LV internal diameter during systole (from 39.00 $\pm$ 7.85 to 35.20 $\pm$ 6.93, p = 0.003), and LA diameter (48.73 $\pm$ 10.57 to 44.09 $\pm$ 11.18 mm, p = 0.001). However, LVEF did not show a significant change from baseline to 1-month. At 1-year follow-up, significant reductions of LV end-diastolic volume and LV end-systolic volume were still observed, indicating sustained improvements in LV remodeling (Table 3).

NYHA functional classes at baseline and 3-months are shown in Fig. 4. At 3 months, 40.9% of patients showed an improvement to NYHA functional class I and 45.5% improved to NYHA functional class II (p 0.001 vs. baseline). One patient (4.3%) suffered single leaflet device attachment (SLDA) 1-week after the operation, and subsequently underwent mitral valve replacement surgery 11-days after the operation. At 1-year, 2 (8.7%) patients died, 1 due to heart failure and 1 due to renal failure. However, 80.9% of the patients had improvement to NYHA functional class I/II (p 0.001 vs. baseline) (Fig. 4).

Fig. 4.

Change in New York Heart Association functional class at 1-year follow-up. p values were calculated by the Wilcoxon signed rank test for paired patients.