Open-heart techniques and mitral valve plasty for mitral regurgitation in toy- and small-breed dogs: A review

Perioperative changes in plasma cardiac troponin I concentration during mitral valvuloplasty for severe mitral regurgitation in dogs

Background

Mitral valvuloplasty (MVP) is a surgical procedure for treating severe mitral regurgitation in dogs. Although MVP is considered highly invasive, the extent of myocardial injury, postoperative complications, and recovery has not been evaluated.

Aim

This study examined the degree of MVP invasiveness, the extent of myocardial damage, postoperative complications, cardiomyocyte recovery, and timing of hospital discharge.

Methods

Cardiac troponin I (cTnI) was used to investigate the myocardial damage caused by cardiac arrest associated with a surgical approach to the myocardium in 13 patients with MVP and five controls with patent ductus arteriosus (PDA) who underwent similar anesthesia and thoracotomy.

Results

The level of cTnI peaked 1 day after surgery and was significantly higher in the MVP group (median, 19.90 ng/ml) than in the control group (median, 1.50 ng/ml p < 0.001). At day 7, the cTnI level was significantly higher in the MVP group (1.9 ng/ml) than in the control group (0.1 ng/ml) (p < 0.001), and recovery to the preoperative level took 10 days in the MVP group but returned to the preoperative level at day 7 in the control group. Although the mean arterial pressure of cardiopulmonary bypass (CPB) at the time of use was 42.92 mmHg, the peak cTnI levels in the two patients who exhibited a temporary decrease of 20 mmHg or less (46.03 ng/ml) were significantly higher than in the other 11 patients (19.70 ng/ml) (p < 0.05). Preoperative cTnI levels were correlated with the severity of postoperative complications (P = 0.03, F = 0.71).

Conclusion

The results showed that MVP caused temporary greater myocardial tissue damage than thoracotomy, but postoperative recovery was smoother. A high preoperative cTnI level requires relatively more careful postoperative management, and measuring the level of cTnI over time after surgery can provide information about the extent of myocardial damage and recovery from surgery and help determine the time of discharge.

Prolonged survival with mitral valve plasty for acute mitral regurgitation due to mitral valve dysplasia and chordal rupture in a young small dog: A case report

Background: We aimed to report the second case of mitral valve plasty (MVP) for acute mitral regurgitation (MR) due to mitral valve dysplasia in a young small dog.

Case Description

A 5-month-old female Jack Russell, weighing 3.5 kg, presented with dyspnea and collapse upon excitation. Acute MR with pulmonary edema due to chordal rupture was diagnosed with a suspected congenital mitral valve anomaly. Despite treatment with high-dose drugs, heart failure symptoms and enlargement worsened. An artificial chordal replacement (ACR) was inserted using polytetrafluoroethylene sutures, and annuloplasty was performed. The dog was discharged on postoperative day 7. After 7 years, the dog underwent operations for complete anterior cruciate ligament tears with no cardiac signs. After 11.5 years, the dog showed no cardiac issues and died from a non-cardiac disease.

Conclusion

The MVP method with ACR employed demonstrated better durability and promoted longer survival than that of previous dog mitral valve replacements.

Effects of mitral valve repair on valvular geometry and hemodynamics in dogs with myxomatous mitral valve disease

OBJECTIVE

To investigate the effects of mitral valve repair on the geometry of the mitral valve complex, hemodynamics, and cardiac function of dogs with myxomatous mitral valve disease (MMVD).

STUDY DESIGN

Retrospective cohort study.

SAMPLE POPULATION

Dogs (n = 77) with stage C MMVD undergoing mitral valve repair under cardiopulmonary bypass.

METHODS

Mitral valve geometry and cardiac function were assessed using echocardiography preoperatively, 1 week postoperatively and 3 months postoperatively.

RESULTS

The coaptation length (0 [0-0] vs. 7 [6-8.5] mm, p < .001) and forward stroke volume index (1.5 ± 0.4 vs. 2.3 ± 0.6 mL/kg, p < .001) were higher at 3-months postoperatively than preoperatively, whereas the vertebral heart score (12.3 ± 1.2 vs. 10.8 ± 0.8 V, p < .001), left atrial-to-aortic ratio (2.2 ± 0.7 vs. 1.2 ± 0.3, p < .001), peak velocity of early diastolic transmitral flow (144 ± 34 vs. 91 ± 18 cm/s, p < .001), and regurgitant volume index (11.3 [8.2-14.0] vs. 1.6 [0.95-2.35] mL/kg, p < .001) were lower. Postoperatively, mitral valve geometry was completely changed within 1 week, whereas changes in vertebral heart score lasted for 3 months.

CONCLUSION

Mitral valve repair changed valvular geometry and improved hemodynamics as assessed by follow-up echocardiography.

CLINICAL SIGNIFICANCE

This study acts as reference for surgeons and cardiologists considering or evaluating the effects of mitral valve repair in dogs and provides useful data for the enhancement of relevant surgical techniques and the selection of relevant pre- and postoperative observations.

Simultaneous surgical repair of a cardiac myxoma causing left ventricular outflow tract obstruction and a ventricular septal defect in a small dog

Background

Cardiac myxomas are benign tumours that can occur in any heart chamber or valve. They are extremely rare in dogs. We present a novel case involving a cardiac myxoma in the left ventricular outflow tract (LVOT) and a ventricular septal defect (VSD) in a small dog.

Case Description

A female miniature dachshund (age, 7 months; weight, 2.88 kg) presented with growth insufficiency, lethargy, and a cardiac murmur. Echocardiography revealed a small polypoid mass in the LVOT and a membranous VSD. Simultaneous surgeries were performed to resect the mass (aortotomy) and close the VSD (right atriotomy) using low-flow cardiopulmonary bypass with surface-cooling hypothermia and retrograde cardioplegia. The tumour was histopathologically identified as a myxoma. The dog survived with no cardiac complications for 11 years after surgery.

Conclusion

To our knowledge, this is the first report of ante-mortem diagnosis and simultaneous surgical repair of a cardiac myxoma obstructing the LVOT and a VSD in a small-breed dog. In addition to describing this complicated case, this report presents what we believe is the first reported use of retrograde cardioplegia during open-heart surgery in a small-breed dog.

Assessment of microcirculation variables and endothelial glycocalyx using sidestream dark field videomicroscopy in anesthetized dogs undergoing cardiopulmonary bypass

Introduction

To evaluate microcirculation and endothelial glycocalyx (eGC) variables using sidestream darkfield (SDF) videomicroscopy in canine cardiopulmonary bypass (CPB).

Methods

Dogs undergoing CPB for surgical correction of naturally-occurring cardiac disease were prospectively included. Variables collected included patient demographics, underlying cardiac disease, red blood cell flow (Flow), 4-25 μm vessel density (Density), absolute capillary blood volume (CBVabs), relative capillary blood volume (CBVrel) and eGC width assessed by perfused boundary region (PBR). Anesthetized healthy dogs were used as control. Microcirculation and eGC variables were compared at baseline under anesthesia (T0), on CPB prior to cross clamping (T1), after cross clamp removal following surgical correction (T2) and at surgical closure (T3).

Results

Twelve dogs were enrolled, including 10 with a complete dataset. Median Flow was 233.9, 79.9, 164.3, and 136.1 μm/s at T0, T1, T2, and T3, respectively, (p = 1.00). Median Density was 173.3, 118.4, 121.0 and 155.4 mm/mm2 at T0, T1, T2, and T3, respectively, (p = 1.00). Median CBVabs decreased over time: 7.4, 6.6, 4.8 and 4.7 103μm3 at T0, T1, T2, and T3, respectively, (p < 0.01). Median CBVrel increased over time: 1.1, 1.5,1.1, and 1.3 103μm3 at T0, T1, T2, and T3, respectively, (p < 0.001). Median PBR increased over time: 1.8, 2.1, 2.4, 2.1 μm at T0, T1, T2, and T3, respectively, (p < 0.001). Compared to control dogs (n = 8), CPB dogs had lower CBVabs at T0.

Conclusion

Alterations in eGC thickness and microvascular occur in dogs undergoing CPB for naturally-occurring cardiac disease.

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

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.

Measurement of Pulmonary Artery Wave Reflection Before and After Mitral Valvuloplasty in Canine Patients With Pulmonary Hypertension Caused by Myxomatous Mitral Valve Disease

Background: Pulmonary arterial wave reflection provides novel information about pulmonary artery hemodynamics in pulmonary hypertension (PH). PH is common in dogs with myxomatous mitral valve disease (MMVD), though research examining the relationship between pulmonary arterial wave reflection and MMVD with PH is lacking. Hypothesis/Objective: This study investigated conventional echocardiographic parameters and pulmonary artery wave reflection parameters before and after mitral valvuloplasty in canine patients with PH due to MMVD. The parameters were backward pressure (Pb), forward pressure (Pf), and the reflection coefficient calculated as the ratio of peak Pb to peak Pf (RC). Animals: The study subjects were 10 client-owned dogs receiving mitral valvuloplasty for MMVD with PH. Methods: Conventional echocardiographic parameters and pulmonary artery wave reflection parameters were measured before and after mitral valvuloplasty. The relationships between pulmonary artery wave reflection parameters and echocardiographic parameters, estimation of pulmonary artery systolic pressure, and right atrium pressure (RAP) gained by catheter in mitral valvuloplasty were also investigated. Post-operative echocardiography and the measurement of pulmonary arterial wave reflection were performed 2 weeks after mitral valvuloplasty. Results: The parameters of normalized left ventricular internal diameter at end-diastole (LVIDDN), E velocity, and the estimation of pulmonary artery systolic pressure were significantly reduced post-operatively compared with baseline measurements (p < 0.05). Post-operative Pb decreased significantly compared with pre-operative measurements (8.8 ± 5.9 to 5.0 ± 3.2 mmHg, p = 0.037) as did RC (0.37 ± 0.15 to 0.22 ± 0.11, p < 0.01). A statistically significant positive correlation existed between wave reflection parameters and RAP, an estimation of pulmonary artery systolic pressure. Conclusions: Results demonstrate that mitral valvuloplasty can be used to treat secondary PH caused by MMVD, resulting in the improvement of post-operative echocardiographic and wave reflection parameters and a decrease in the right afterload. In some patients, some degree of vascular admittance mismatch persisted, despite the improvement of left atrial pressure. This may be indicative of residual pulmonary arterial disease, which may continue to adversely affect interactions between the right ventricle and the vasculature.

Successful mitral repair in dogs by mitral annuloplasty using Hegar dilator: two case reports

Mitral regurgitation (MR) is the most common heart disease in small-breed dogs. Mitral repair, which comprise artificial chorda tendineae implantation and mitral annuloplasty, has become the mainstay of treatment in the veterinary field. We report on two small dogs who underwent mitral repair surgery for MR. A Hegar dilator was used during mitral annuloplasty for accurate and reproducible surgery. In both cases, mitral regurgitant flow almost disappeared after surgery, and clinical signs improved. The treatment regimen was terminated 3 months after the surgery. We concluded that using a Hegar dilator may facilitate mitral valve repair surgery.

Echocardiographic evaluation of deformity and enlargement of the canine mitral valve annulus associated with myxomatous degenerative mitral valve disease

INTRODUCTION/OBJECTIVES

Quantitative evaluation of the morphology of the mitral valve annulus (MVA) in dogs with myxomatous mitral valve disease (MMVD) may improve the techniques of mitral valve plasty. This study aimed to compare the MVA morphology on echocardiography in normal dogs and dogs with MMVD and to compare the echocardiographic and intraoperative measurements of the MVA in dogs with MMVD.

ANIMALS, MATERIALS AND METHODS

The study population comprised 59 healthy dogs (control group) and 371 dogs with MMVD (MMVD group). The anterior-posterior diameter and transversal diameter (TD) of the MVA and the aortic annulus diameter were measured by echocardiography to calculate the mitral valve flattening ratio, mitral annulus area (MAA), mitral annulus circumference (MAC), contraction ratio of the MAA and aortic annulus area. In the MMVD group, the mitral annulus diameter (MAD) was macroscopically measured during mitral valve plasty. Areas and lengths were divided by the body surface area (BSA) and √BSA, respectively, for comparative analyses.

RESULTS

The systolic and diastolic anterior-posterior diameter/√BSA, transversal diameter/√BSA, MAA/BSA converted to a natural logarithm (Ln(MAA/BSA)), and MAC/√BSA was significantly higher in the MMVD group than the control group, whereas flattening ratio values and contraction ratio of the MAA was significantly lower. Neither the aortic annulus diameter /√BSA nor the Ln(aortic annulus area/BSA) significantly differed between groups. In the MMVD group, diastolic MAC/√BSA and MAA/BSA correlated significantly with the MAD/√BSA.

CONCLUSIONS

The MVA is larger and rounder in dogs with MMVD than controls. Two-dimensional echocardiographic measures of MAA and MAC correlate well with intraoperative measures of MAD.