Abstract
The goal of MitraClip therapy is to achieve mitral regurgitation reduction without iatrogenic creation of clinically significant MS. In some series, up to 35% of patients are left with mild MS. There are many contributors to the final transmitral gradient achieved in patients undergoing MitraClip therapy. Additionally, there are many modalities used for the intraprocedural assessment of MS with no one modality considered to be the benchmark. We herein describe a case which illustrates the dynamic nature of clip-leaflet interaction, and review intraprocedural techniques for invasively and noninvasively assessing MS.
Highlights
- •
Goal of MitraClip therapy is for MR reduction without creation of iatrogenic mitral stenosis.
- •
Intra-procedural assessment for mitral stenosis is imperative and multiple non-invasive and invasive methods can be utilized.
- •
Nuances of mitral stenosis assessment include differential gradients across each orifice, leaflet/clip interaction, and leaflet compliance.
1
Introduction
Percutaneous repair of the mitral valve using the MitraClip system (Abbott, Abbott Park, Illinois) has been shown to be an effective and safe non-surgical method for patients with symptomatic primary and secondary mitral regurgitation (MR) . The main goal of MitraClip therapy is to achieve MR reduction without creation of clinically significant mitral stenosis (MS). Since the initial EVEREST trials, it has been established that in properly selected patients with adequate baseline mitral valve area (MVA), the magnitude of MVA reduction and increase in transmitral gradient (TMG) is mild and remains stable out to two years post-MitraClip . In one series , 35% of patients at the conclusion of the procedure were left with mild MS, defined by a TMG > 5 mmHg (mean 8.3 ± 1.3 mmHg), although this was deemed to be clinically insignificant as the majority of patients remained symptom free on follow-up.
Several case reports in the literature note development of clinically significant MS in follow-up which should raise concern and diligence towards intraprocedural assessment of TMGs. Many factors can contribute to the magnitude of the TMG in a given individual. In addition to common factors such as atrial and ventricular loading conditions, volume status, presence of atrial septal defect, and heart rate, there are several under-recognized factors such as compliance of the leaflets and/or the annulus, the degree of interaction between multiple clips, location of clip placement along the mitral coaptation plane (central vs. noncentral), and the leaflet itself (shallow vs. deep insertion). We herein describe a case which illustrates the dynamic nature of clip-leaflet interaction, and review intraprocedural techniques for invasively and noninvasively assessing MS.
2
Case report
A 32 year old woman was referred for evaluation of severe symptomatic MR. She had a complex medical history consisting of systemic lupus erythematosus complicated by antiphospholipid syndrome with venothromboembolic disease requiring systemic anticoagulation, thrombocytopenia requiring splenectomy, and stage 5 chronic kidney disease requiring hemodialysis. Additionally, she had history of myocardial infarction in the setting of illicit substance abuse, history of methicillin-resistant Staphylococcus aureus cellulitis, hypertension, dyslipidemia, and obesity. She had developed medically refractory NYHA III symptoms one year prior to referral with transthoracic echocardiogram (TTE) demonstrating severe MR.
TTE showed a left ventricular (LV) ejection fraction of 55%, mild LV enlargement with LV end-diastolic dimension 5.86 cm, left atrial enlargement at 6 cm in the anteroposterior dimension, 4+ eccentric mitral regurgitation, 2+ tricuspid regurgitation, and a right ventricular systolic pressure of 40 mmHg. She had a resting transmitral gradient of 5 mmHg with an MVA of 4.65 cm 2 by pressure half-time (PHT) measuring at 47 ms ( Fig. 1 A and B , Table 1 ).
| Preprocedure TTE | HD1 TTE | Follow-up TTE | |
|---|---|---|---|
| Peak TMG (mmHg) | 9 | 19 | 11 |
| Mean TMG (mmHg) | 5 | 11 | 8 |
| PHT (ms) | 47 | 141 | 130 |
| MVA | |||
| PHT | 4.65 | 1.56 | 1.7 |
| BP (mmHg) | 119/74 | 124/72 | 120/78 |
| Pulse (bpm) | 84 | 73 | 76 |
A transesophageal echocardiogram (TEE) demonstrated distinct calcifications of the leaflet tips of the P2 segment of the mitral valve causing incomplete closure and resultant severe MR ( Fig. 2 ). There was no redundancy of the mitral valve leaflet but a small cleft was noted within the posterior medial leaflet ( Fig. 2 C). By PISA, the effective regurgitant orifice area was 0.38 cm 2 with a regurgitant volume of 75 cm 3 . Resting TMG (under sedation) was 3 mmHg with an MVA of 4.24 cm 2 by planimetry in multiplanar reconstruction (Q Lab, Phillips Medical Systems, Andover, MA, USA) and 4.3 cm 2 by PHT with a PHT value of 51. A coronary angiogram demonstrated a right dominant epicardial system without obstructive atherosclerotic disease or coronary anomalies.
The patient had an elevated predicted surgical mortality (Society of Thoracic Surgery score of 8%) and was therefore referred for percutaneous MV repair. After general anesthesia was administered, right heart catheterization with a systemic arterial pressures of 87/53 mmHg revealed a mean right atrial pressure of 8 mmHg, pulmonary artery pressure of 28/17 mmHg with a mean of 22, and a mean pulmonary capillary wedge pressure (PCWP) of 12 mmHg with V waves to 17 mmHg. As there was concern for borderline TMG going into the procedure, decision was made to place a pigtail catheter within the LV to assess PCWP-LV pressures intra-procedurally. Under fluoroscopic and TEE guidance, transseptal puncture was achieved and the MitraClip guiding catheter was advanced into the left atrium (LA) as previously described . Simultaneous LA-LV pressures were recorded prior to advancement of the first MitraClip and corroborated with PCWP-LV pressures. The resting mean LA/PCWP-LV pressure was measured to be approximately 2.5 mmHg ( Fig. 3 A ).
For descriptive purposes, our practice has been to delineate 9 grasping locations along the line of coaptation with each scallop divided into a lateral, central, and medial segment ( Fig. 4 ). This number can increase to 11 if you consider commissural grasps. The first grasp was performed at the medial A2/P2 interface within the area of maximal regurgitation, lateral to the postero-medial cleft. The initial closure of the clip was to 70%, followed by assessment of leaflet insertion, and ultimate clip closure to 100%. This is then followed by assessment of residual MR by color Doppler as well as with examining left and right upper pulmonary vein flow patterns. An evaluation for MS is performed with residual transmitral gradients in both orifices, PHT value, MVA by PHT, MVA by 3D planimetry (if needed).
On evaluation, there was substantial reduction in MR severity (from 4+ to 1+). However, the medial and lateral orifice had a TMG of 10 mmHg and 6 mmHg, respectively. MVA by PHT was 1.06 cm 2 . 3D planimetry of the medial and lateral orifice was 0.64 cm 2 and 1.68 cm 2 ( Fig. 5 ), respectively, for a combined planimetered MVA of 2.32 cm 2 . Finally, simultaneous WP-LV demonstrated a TMG of 8.5 mmHg ( Fig. 3 B). An alternative grasping location was sought to see if a lower final TMG could be achieved. This grasp was released and an additional six grasps were performed along the coaptation plane ( Fig. 6 ). Each grasp resulted in varying degrees of MR reduction; however, each grasp also resulted in substantial TMGs ( Table 2 ).
| Grasp 1 | Grasp 2 | Grasp 3 | Grasp 4 | Grasp 5 | Grasp 6 | Grasp 7 (Final) | Clip Released | |
|---|---|---|---|---|---|---|---|---|
| Grasp Location | Medial A2/P2 | Central A2/P2 | Lateral A2/P2 | Medial A1/P1 | Central A1/P1 | Lateral A1/P1 | Lateral A3/P3 | |
| MR Grade after tightening | 1+ | 1+ | 1+ | 1+ | 2+ | 3+ | Tr | |
| Lateral Orifice | ||||||||
| Peak TMG | 14 | 12 | No Significant Lateral Orifice | 14 | 10 | |||
| Mean TMG | 8 | 8 | 7 | 6 | ||||
| PHT | 207 | 152 | 170 | 196 | ||||
| MVA by PHT | 1.06 | 1.45 | 1.29 | 1.12 | ||||
| Medial Orifice | ||||||||
| Peak TMG | 16 | 18 | 16 | 17 | 16 | 12 | 17 | 13 |
| Mean TMG | 10 | 10 | 8 | 9 | 9 | 7 | 8 | 7 |
| PHT | 263 | 151 | 212 | 165 | 197 | 209 | 151 | 221 |
| MVA by PHT | 0.84 | 1.46 | 1.04 | 1.33 | 1.12 | 1.05 | 1.46 | 1.00 |
| LA/WP-LV | 8.5 | 8.5 | 7.3 | 7.7 | 7.5 | 5.2 | 7.0 | 5.7 |
Each grasp resulted in varying TMGs based on location of the grasp along the coaptation plane and the degree of clip tightening. On one grasp, during initial grasp and closure (70%) and prior to tightening, the WP-LV pressure resulted in a TMG of 7 mmHg. After appropriate leaflet insertion was interrogated and deemed acceptable, the clip was maximally tightened (100%) resulting in a dynamic increase in simultaneous WP-LV pressure to 12 mmHg with reduction in the gradient to 8 mmHg after it was untightened ( Fig. 7 ).
