Combination of the Modified Loop Technique and De Vega Annuloplasty in Dogs with Mitral Regurgitation

SIMPLE SUMMARY: Dogs, like humans, may develop valvular disease, which is particularly common in older, small-sized dogs and is one of the most common causes of canine death. Canine valvular disease generally has a good prognosis. However, approximately 30% of dogs develop congestive heart failure, particularly when the mitral valve is affected, and most dogs with severe congestive heart failure die within a year of pulmonary edema. Although cardiac surgery with extracorporeal circulation can be performed in dogs and can significantly prolong survival, the dogs’ small size is challenging from a surgical perspective, and the success rate depends on the surgeon’s skill. Mitral valve repair in dogs involves suturing cardiac tendons using polytetrafluoroethylene sutures, which are slippery and difficult to ligate at the targeted length. Moreover, the appropriate length of the artificial tendon in dogs has not been determined. The mitral annulus surrounding the mitral valve also needs to be stitched down, but the amount that should be stitched down in dogs is not known because prosthetic valve rings were not manufactured for dogs. Due to the lack of reports detailing surgical procedures in dogs, we describe in detail a surgical technique for canine mitral valve repair. ABSTRACT: Background: Detailed surgical techniques for treating canine mitral regurgitation have not been previously reported. Method: This case series included six consecutive client-owned dogs with mitral regurgitation. All dogs underwent a combined protocol, including the modified loop technique and De Vega annuloplasty (MODEL surgery), in 2021. Artificial loops covering 80% of the length of the strut chordae tendineae were used for chordal replacement. Mitral annuloplasty was subjectively performed, targeting the circumference of the septal leaflet. Results: The breeds were Chihuahua-mixed breed, Spitz, Pomeranian, Cavalier King Charles Spaniel, and Chihuahua, with average ages and weights of 11.4 ± 2.3 years and 5.49 ± 2.98 kg, respectively. The aortic cross-clamp, pumping, and surgery times were 64.0 ± 7.5 min, 168.5 ± 39.1 min, and 321.0 ± 53.1 min, respectively. After MODEL surgery, left atrial-to-aortic ratios significantly decreased from 2.20 ± 0.18 to 1.26 ± 0.22 (p < 0.01), and left ventricular end-diastolic internal diameter normalized to body weight significantly decreased from 2.03 ± 0.26 to 1.48 ± 0.20 (p < 0.01). In all cases, the clinical signs disappeared or improved significantly. Conclusions: MODEL surgery increased mitral valve coaptation, normalized heart sizes, and significantly improved clinical signs in dogs with mitral regurgitation.