Current case selection guidelines for mitral transcatheter edge-to-edge valve repair (TEER) are based on ongoing experience with the feasibility trial in dogs, as well as current American College of Cardiology/American Heart Association (ACC/AHA) guidelines for mitral valve interventions in humans. Dogs undergoing consideration for TEER should meet integrative criteria for severe mitral regurgitation (MR) independent of diuretic status and have functional mitral anatomy appropriate for an edge-to-edge repair.
Mitral regurgitation severity
Dogs undergoing TEER intervention should meet criteria for severe MR adapted from ACC/AHA and American Society of Echocardiography guidelines for severe MR in humans. This could include dogs in American College of Veterinary Internal Medicine stage B2 or stage C. Dogs in late-stage C/D or atrial fibrillation are considered less ideal candidates for this procedure but can be considered. Determination of MR severity is based on consideration of multiple criteria.
Criteria that support severe MR include:
- Holosystolic wall-impinging eccentric color-flow jet or
central color-flow jet area ≥50% - E-wave dominant mitral inflow ≥1.0 m/s and/or E:A ratio >2
- Dense holosystolic triangular regurgitant profile on CW Doppler
- Regurgitant fraction ≥50% (PISA, volumetric, Doppler)
- Regurgitant volume ≥1.2 mL/kg
Color-flow Doppler patterns should be assessed on multiple systolic images at appropriate gain and Nyquist settings. Single images can overestimate MR severity. Measurement of mitral regurgitant fraction (RF) and regurgitant volume (RVol) by PISA, Simpson’s volumetric, and/or Doppler methods provides quantitative assessment of MR severity and therefore represent important objective criteria. Measurement of RF by multiple methods increases confidence in the assessment. Vena contracta (VC) width and effective regurgitant orifice (ERO) area can also be considered but are dependent on patient size and limits for severity have not been fully established in dogs. Left ventricular and left atrial dilation (LVIDdN >1.9, LA:Ao >2.0) are supportive of severe MR, but these are secondary changes in response to MR and are dependent on other influences such as chronicity and therapy.
Anatomic complexity
Anatomic complexity of the mitral valve is an important predictor of procedural success and outcome in dogs undergoing TEER intervention. Based on available canine device sizes, mid-systolic anterior-posterior (A-P) mitral annular diameter should be between 14 millimeters and 22 millimeters on apical inflow-outflow (five-chamber) echocardiographic view. The anatomic inclusion criteria is dominant malcoaptation of the central mitral leaflet segments. Guidelines for anatomic complexity are not absolute but represent a continuum from noncomplex to unfavorable. Dogs with noncomplex anatomy can be expected to have the best outcomes in terms of reduction in MR severity and extension of life expectancy with the lowest procedural risk. Dogs with complex anatomy are still considered good candidates depending on operator experience. Dogs with very complex anatomy may derive benefit from TEER with some associated increase in procedural risk. Dogs with unfavorable anatomy carry a high procedural risk compared to potential benefit and are considered poor candidates for the TEER procedure. Final assessment of functional anatomy for edge-to-edge repair is based on pre-procedural transesophageal echocardiography.
Criteria for anatomic complexity for canine TEER
| Noncomplex Ideal for TEER | Complex Suitable for TEER | Very Complex Challenging TEER | Unsuitable for TEER |
|---|---|---|---|
| Benefit>>>Risk | Benefit>>Risk | Benefit≥Risk | Risk>Benefit |
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VC: vena contracta; AP: anterior-posterior
a optimal clamp size is systolic AP dimension +/- 1 millimeter