The MitraClip system uses the concept of the surgical edge-to-edge Alfieri repair in an innovative transcatheter approach.1 The MitraClip, a polyester-coated cobalt-chromium implant (Fig. 3), is placed percutaneously via the femoral vein; a transseptal puncture with a 22-F guide catheter is required to cross the atrial septum and release the clip to approximate the edges of the A2 and P2 segments. An additional clip can be placed near the first clip if significant residual MR remains. The MitraClip has been used in the United States to treat functional and organic MR in the EVEREST I and II trials2 and in the ongoing REALISM study.a
The EVEREST II trial, a randomized study that compared the efficacy of MitraClip repair of MR with conventional surgical repair or replacement, demonstrated higher rates of 3 and 4+ MR before hospital discharge (23% vs 0%) and need for subsequent MV surgery at 12 months (20% vs 2%) after intervention in the MitraClip group versus the surgical group.2 Argenziano et al.3 reported on 32 of 107 patients who came to the operating room for MV surgery after their MitraClip procedure. Indications for surgery included partial clip detachment, more than 2+ MR, and iatrogenic ASD; approximately, one-third of patients had some leaflet or chordal damage as a result of the MitraClip. Regardless of the increased necessity for subsequent MV surgery, the MitraClip has a good safety profile and remains an attractive treatment option for high-risk surgical candidates.
To our knowledge, this is the first reported case of MV surgery for the correction of MS after MitraClip placement. Although valve area decreases after MitraClip placement, significant stenosis is not typically seen.4 Alfieri repair is generally avoided in patients with rheumatic disease, limited leaflet mobility, and valve area < 4 cm2 because of the concern for stenosis; there were similar exclusion criteria for MitraClip placement in the EVEREST II trial.1,2 The patient’s end stage renal disease in this case may have played a role in calcium deposition on the clips, contributing to stenosis. The particular challenges in evaluation of MS in a double-orifice MV have been discussed by Bader et al.5 regarding the Alfieri repair. Mean diastolic transmitral gradient has the same validity in assessing double-orifice valves as single-orifice valves6; however, it is influenced by heart rate, cardiac output, and concomitant MR. Although the validity of the pressure half-time method of calculating MV area (MVA) has not been specifically studied in double-orifice MVs, it is recognized that changes in left ventricular (LV) compliance immediately after bypass make pressure half-time calculations of MVA inaccurate; this method may also be unreliable in patients with reduced LV compliance at baseline and those in atrial fibrillation. For these reasons, a direct measurement of MVA by planimetry is helpful in making a diagnosis. The basal transgastric short-axis view offers an en face view of the MV from the LV. The planimetry measurement should be made in mid-diastole; the edges of the MV leaflets should be seen, and each orifice traced and the areas combined to calculate total MVA. This 2D measurement can be limited by excessive leaflet calcification or increased echogenicity of the Mitraclip, resulting in an underestimation of MVA, while failure to trace in the plane that demonstrates the narrowest cross-sectional area will overestimate MVA. Three-dimensional echocardiographic assessment of MVA using multiplanar reconstruction is now preferred over 2D planimetry measurements in determining MS severity, because the smallest orifice can be more reliably detected.7
In patients returning to the operating room after failed MitraClip, attention should be paid to the atrial septum to detect iatrogenic ASD from previous transseptal puncture,3 and the tricuspid valve should be interrogated for significant regurgitation, which may have worsened in the presence of a left-to-right interatrial shunt or elevated pulmonary artery pressures. As the MitraClip continues to be available to patients in the ongoing REALISM study, and with likely expanded use on the horizon, the number of patients with MitraClips referred for MV surgery will increase. Familiarity with the appearance of the clips and a high level of suspicion for associated findings (clip detachment, leaflet or chordal damage, MS, ASD, and tricuspid regurgitation) on the preoperative TEE examination can allow the echocardiographer to assist in providing the correct, and hopefully definitive, surgical treatment.
The patient gave consent for this report.
Clinician’s Key Teaching Points
By Nikolaos J. Skubas, MD and Martin J. London, MD
* The MitraClip is inserted percutaneously via the femoral vein across the interatrial septum into the left atrium. It clips together the edges of the A2 scallop and the P2 segment of the mitral valve (MV), thereby reducing the severity of mitral regurgitation (MR). Similar to the open surgical Alfieri technique, the MitraClip produces a smaller, double-orifice MV.
* Transesophageal echocardiography (TEE) is used for the placement of the MitraClip, after deployment evaluation of residual MR, and for the assessment of the diastolic MV orifice with: (1) planimetry, by tracing along the edges of the 2 orifices in mid-diastole (transgastric basal view) and (2) measurement of the mean diastolic pressure gradient with continuous wave Doppler (midesophageal views). However, planimetry may be challenging in cases of severe MV leaflet calcification and mean pressure gradient is elevated with tachycardia and increased diastolic flow across the MV. The pressure half-time method should not be used in the setting of tachycardia or decreased left ventricular compliance as both will prolong it independent of the gradient across the valve.
* In this case, a patient, who had 2 MitraClips placed 16 months before admission, presented with moderate MR and severe systolic pulmonary hypertension. Severe mitral stenosis was diagnosed based on increased mean diastolic gradient (10 mm Hg at 80 bpm). Extensive calcification of the mitral leaflets due to renal failure along with the increased echogeneity of the MitraClip devices made planimetry of the 2 orifices difficult. An iatrogenic atrial septal defect with a significant left-to-right shunt and moderate tricuspid regurgitation were also found. Surgery included MV replacement, tricuspid valve repair, and closure of the atrial septal defect.
* Insertion of the MitraClip is a safe procedure for high-risk surgical patients with functional or organic MR. However, residual MR if often observed after the procedure. Less frequently, new mitral stenosis (as illustrated in this case) is observed, and the procedure is contraindicated in patients with an MV area <4 cm2. TEE is helpful for the evaluation of the MV as well as for diagnosing iatrogenic complications, such as atrial septal defects. Three-dimensional TEE may allow for more accurate planimetry of the dual MV orifices.
Name: Karen Singh, MD.
Contribution: This author helped write the manuscript.
Attestation: Karen Singh approved the final manuscript.
Name: Jacob Raphael, MD.
Contribution: This author helped write the manuscript.
Attestation: Jacob Raphael approved the final manuscript.
Name: Douglas Colquhoun, MBChB, MSc.
Contribution: This author formatted the echo images and clips.
Attestation: Douglas Colquhoun approved the final manuscript.
This manuscript was handled by: Martin J. London, MD.
a Pivotal Study of a Percutaneous Mitral Valve Repair System (EVEREST II). Available at: http://www.clinicaltrials.gov/ct2/show/NCT00209274?term=REALISM&rank=2. Accessed November 23, 2012. Cited Here...
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