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Introduction:
Tricuspid valvular dysplasia is a congenital heart disease in canines whose current prevalence is unknown. It is characterized by malformation of the tricuspid valve leaflets, chordae tendineae and papillary muscles of the right ventricle, either alone or in combination. 2 3 This set of malformations can occur alone or in combination with other congenital heart diseases, of which the most common in our case material was pulmonary stenosis. It can also occur with mitral valve dysplasia.4 Varying degrees of valvular insufficiency result from tricuspid malformation and in rarer cases tricuspid valve stenosis. Dogs that are mildly affected may not show clinical signs. The disease is usually progressive and develops complications early in the animals life, such as ascites, pleural effusion, exercise intolerance, syncope, weight loss, and arrhythmias.^* 2 When right heart failure occurs, one is facing the terminal stage of the disease. Many medical treatments have been tried to eliminate the clinical signs, but they are palliative. For this, we designed a surgery via the inflow occlusion technique for the opening of the right atrium and achieve clear visualization of the tricuspid valve. Using the Alfieri technique -that is to say- placing a stich in the valve apposition zone to transform the uniorificial valve into a bioorificial one,   thus decreasing torrential flow to the right atrium t2t)3t)

7 animals were operated, all under one year of age. They were 1 Labrador, 1 Boxer, 2 English Bulldogs and 3 French Bulldogs. With this technique, a single surgical death occurred in 1 of the French bulldogs that presented the pathology combined with pulmonary stenosis. In all cases, it was possible to transform the valve into a bio- orificial valve and reduce the regurgitating flow. The rest of the animals are currently under clinical follow-up. 5

Materials and methods:
Between 2019 and 2023, our team evaluated 20 canines with a diagnosis of congenital tricuspid dysplasia. Of these 20 animals, 7 were selected as surgical candidates. The General selection criteria were:
1)    Absence of severe ripht conpestive failure (without ascites, without pleural effusion, without syncope or intolerance to exercise),
2)    Sinus rhythm without intermittent atrial fibrillation.
3)    Tricuspid regurpitation: 60% of the ripht atrial volume onwards and tricuspid regurpitation velocity greater than 2.5m/sec.
Normal right ventricular lateral TAPSE (measured through the septal rinp) and a ripht bundle branch compliance index.
4)    Pulmonary artery anatomy within normal. Accordingly, 7 animals were selected, 1 of the Labrador breed, 1 of the Boxer breed, 2 of the English Bulldog breed and 3 of the French Bulldog breed. The weights ranped between 4 and 20kp, the apes were between 4 and 8 months of ape, the sexes were 4 females and
3 males, and the size of the tricuspid regurpitation jet was central concentric in 5 animals and eccentric with septal oripin in 2 animals.

Methods:
Surgery was designed takinp into account the Alfieri technique that is placing a 4-0 Polypropylene stitch at the appositional site between the two leaflets facinp the center of the maximum reflux site, in order to provide a palliative solution to tricuspid reflux. To assess the main site of reflux, a preoperative Doppler echocardiogram was performed using all possible echotomograms to determine the site of greatest reflux.

The circulatory occlusion or inflow occlusion technique was used to gain access to the right atrium in normothermia with the heart beating. This allows for a 7 minute occlusion period. If the surgical objective is not achieved in those 7 minutes, the clamp should be released and the heart allowed to beat at normothermia for 10 minutes before performing a second period of occlusion. In all the operated cases except 1, it was possible to perform the surgical technique in less than 7 minutes. The case in which it was necessary to perform more than a 7 minutes session was a complex case with congenital tricuspid dysplasia and pulmonary valve stenosis. In this individual, 3 episodes of circulatory occlusion were performed.

First, the pulmonary stenosis was resolved and afterwards the tricuspid regurgitation. This was the animal that had a cardiac arrest
24 hours after the operation, the only perioperative death. Another animal died a year from non-cardiovascular causes. The rest of the animals are currently alive and without right ventricular failure.

Surgical technique:
Anesthesia:
The premedication was morphine at 1mp/kp with acepromazine 0.01mp/kp. induction bepan with ketamine 10mp/kp with midazolam 0.2mp/kp and was continued with isoflurane.
1)    Positioninq the patient:
It was performed was through a right thoracotomy at the level of the Sth intercostal space.
After performing the thoracotomy, the right cranial lung lobe was dislocated in order to gain access to a wider surgical field.
2)    Access and control of the great veins: Rummel tourniquets with 2/0 silk were pre- placed over the azygos vein, the cranial vena cava and over the caudal.
3)    Pericardiotomy:
An oblique incision was made over the pericardium respecting the phrenic nerve allowing access to the wall of the right atrium on which directing sutures were placed.
4)    Atriotomy:
Several sutures of polypropylene pre- assembled with Teflon felt were performed between the apex of the right atrial appendage pointing to the caudal vena cava. The length of the incision was about of 4 cm and the distance from the atrioventricular sulcus was about more than 2cm in order to not distort the geometry of the coronary artery and the tricuspid annulus.

After placing the driving points, a vascular clamp was placed over the right atrium that included the site where the driving points were placed, and then the atriotomy incision was made with the clamp in place. Once the incision was made, the sequential closure of the tourniquets began and the timing began.
5)    The inflow stasis itself:
The tourniquets are always closed from the one with the lowest flow to the one with the highest flow, that is, the azygos is closed first, then the cranial vena and finally the caudal vena. Once the caudal cava is closed, we wait between 7 and 10 right ventricular beats and the clamp was released opened. At this time residual blood begins to flow from the right atrium which must be aspirated.
6)    Assessinq the precise site of the reflux: The residual volume of the right ventricle allows us to visualize where the greatest reflux occurs.
7)    Placement of the stitches:
It is usually between the appositional site of the septal and posterior leaflet.
For this, 4/0 cardiovascular polypropylene sutures are used. 2* From the atrial point of view, an horizontal U point or an X point was made between the the leaflets selected, taking care to suture the appositional site of the leaflets. Fig 8,9,10,1121,22

8)    De-airinq the heart and returninq to normal flow:
Once the Alfieri.15 is done, the air is  purged by placing warm saline solution to fill the entire cavity. Then the clamp is repositioned involving the wall with the directing points. The cava and azygous tourniquets are then released in the opposite direction to that in which they were placed. Finally, the residual air is evacuated by opening the Satinski forceps allowing blood and air to escape. Then the clamp is repositioned when the bleeding is clear and the atriotomy is sutured with 3/0 polypropylene. Finnaly, The clamp is removed and eventual bleeding sites needing additional stitches are performed. The thorax is closed in a standard fashion a thoracostomy tube left for one day. The patient remains hospitalized for a period of 48 hours. An intraoperative echocardiopraphic study is performed, one immediately after the surgical technique, as well as the follow-up at one month, at 3 months, at 6 months and at one year in all the individuals operated on.

The average time to inflow occlusion in 6 of the 7 animals was 5-6 minutes. On average, low regurpitant flow is between 0.5m/s and 1.5m/s per second in echocardiopraphic studies. The biorificial valve was documented.

No iatropenic tricuspid stenosis was recorded in subsequent echocardiopraphic studies. The entire surgical act was performed in normothermia. The patient who died 24 hours later was the one who suffered the combination with pulmonary stenosis and was the one who spent the longest time with partial occlusions. The suspected death was a pas embolism. At present, all the animals are under follow-up (except the one that died from non-cardiac causes) and do not present ripht conpestive heart failure or atrial fibrillation and maintain the bi-orificial tricuspid valve.

Discussion
We have recorded 3 types of pathological lesions in patients with tricuspid dysplasia. The most common is that which occurs with retracted valve leaflets, totally or partially fused to abnormal papillary muscles or muscle bands that cross the lumen of the right ventricle, sometimes configuring two sites of reflux and with great dilation of the right atrium (Fig 1 and 2). The second type registered is the one that occurs with total fusion of the posterior leaflet to the papillary muscles without chordae tendineae (more commonly seen in Labrador retrievers) fig 3 and 4.4 The third anatomical type (and the of less frequency) is known as Ebstein anomaly, with atrialization of the septal aspect of the right ventricle, the implanted valve plane oblique with respect to the right atrioventricular coronary groove and the septal valve fused to the wall due to failure of delamination Fig. 5.3 4

Surgery was considered effective for the two first types of anatomical lesion, but not for the third type.

Associated pathologies:
The most common were fossa ovalis atrial septal defect, persistent left cranial vena cava, and pulmonary stenosis. If the ASD anomaly and tricuspid dysplasia were recorded, we decided to previously close the ASD before solving the tricuspid dysplasia, provided that the patients did not have pulmonary hypertension.

The cases presented here, although they are few in number, allowed us to follow up 6 of the 7 patients operated on over time (since the patient with tricuspid dysplasia and pulmonary stenosis died on the postoperative day). Of these 6 patients, one died a year later due to non-cardiac causes. Fig 6. The rest are still alive and without symptoms. This has shown that the surgical technique is safe, repeatable, economical and, if it is performed on the site of the valve plane where it was previously detected by transthoracic echo or by intraoperative echo, the site of greatest loss of regurgitant jet is effective in reducing the reflux. The latter has been based not only on the decrease in the speed of the post- surgical jet but also on the decrease in the progression of the growth of the right atrium assessed by echocardiography and on the determination of the absence of clinical signs.

Here it is worth opening the discussion about whether it is feasible to only evaluate the result of the surgery of the speed of the regurgitating jet before  and  after  surgery, since we know that load conditions and applied treatments influence the determination of the speed of the jet. The type of prior selection of each patient also influences through what was considered to assess right ventricular function as  normal. This is important because in veterinary medicine the utility of the PISA for the tricuspid regurgitation jet is not standardized, therefore it does not exist for pre-surgical evaluation. For all this we take into account several parameters as follows:

the preoperative clinical signs, the evaluation of the right ventricle through the TAPSE, the septal paradoxical movement, the distensibility index of the right branch of the pulmonary artery, the size of the right atrium, the average regurgitant flow with respect to the right atrium, the collapsibility of the caudal vena cava with the respiratory cycle, and the velocity of the regurgitant jet. All the added criteria were considered for the pre-surgical evaluation and to assess post-surgical success. Other determinations were not available. 3 ^

It is very important to recognize that a very recent work in human medicine demonstrated that the speed of the post-surgical jet in tricuspid regurgitation, after a percutaneous edge-to-edge closure technique, is not as determinant of the success of the surgery as it is opens the possibility of considering new sets of parameters to assess the success of interventions in the tricuspid valve plane. (1) We also consider it very important to determine the place where the apposition point is applied through pre- or intra-surgical assessment of the place of origin of the maximum regurgitant jet in the valve plane. This demonstrated the transformation of a uniorificial valve to a bioorificial valve without causing iatrogenic post-surgical tricuspid stenosis.

In the same sense,23 the assessment of the tricuspid subvalvular apparatus was very important, for which we made different standard echocardiographic cuts and oblique echocardiographic cuts from the right ventricular outflow tract, in order to determine the type of anomaly and location of the largest loss site.
We believe that, from the best of our knowledge, it is the first time that an attempt has been made to reduce the flow of the tricuspid regurgitant jet in canines  with tricuspid dysplasia through a technique such as that of Alfieri, placing an apposition point at the site of maximum regurgitant flow to reduce in a palliative way the effect of tricuspid regurgitation on the right chambers and thus prolong the time and quality of  life of the treated animals.

One limitation of the study is not having been able to compare the animals treated surgically with animals treated solely with pharmacological therapy, although  the natural history of tricuspid dysplasia without surgical intervention makes it possible to predict right ventricular failure with the high mortality that this entails.

Conclusion
We believe that, to our knowledge, it is the first time that an attempt has been made to reduce the flow of the tricuspid regurgitant jet in canines with tricuspid dysplasia through a technique such as that of Alfieri, placing an apposition point at the most precise site of maximum regurgitant flow to reduce in a palliative way the effect of tricuspid regurgitation on the right chambers and thus prolong the time and quality of life of the treated animals. Although the Alfieri technique has a real but small place in in Human Medicine in virtue of the overwelming more stable repair techniques, we estimate that it can be very useful in canines due to the lower life expectancy of this species. The inflow occlusion right atrial approach is also feasible with a reduced surgical and post- surgical costs with low mortality.

One limitation of the study is not having been able to compare the animals treated surgically with animals treated solely with pharmacological therapy, although  the natural history of tricuspid dysplasia without surgical intervention makes it possible to predict right ventricular failure with the high mortality that this entails.

Corresponding Author: Guillermo Belerenian Veterinary Doctor
University of Buenos Aires (UBA), Specialist in Cardiology.
Director of the Institute of Zoonoses Luis Pasteur city of Buenos Aires, Argentina
Email: [email protected]

Funding Statement:
None

Acknowledgement:
We have to thank Micaela Sottile for the kindly
preparation of the manuscript

Conflicts of Interest Statement: None

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