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HOPIA clinique vétérinaire
14 boulevard des Chênes
78280 Guyancourt

Nos horaires

OUVERT 24H/24 & 7J/7

Consultations sur RDV :
Du lundi au vendredi : 8h00 • 20h00
Samedi : 8h00 • 19h00


At HOPia Hospital, learn more about our expertise


Sabine et Jean-Hugues Bozon, clinique vétérinaire Hopia Versailles Grands Parc


Doctors Sabine and Jean-Hugues Bozon, who are the only 2 vets diplomate of cardiopulmonary bypass sciences, belong to the very private circle of wordly renowned open-heart surgery team. Thanks to their many years practising in this field, they set up a 100% French team of professionals (surgeon, instrumentalists, cardiologist, perfusionists, anaesthetists, highly trained nurses…).

Drs Sabine and JH Bozon are focusing more and more on open-heart surgeries and interventional cardiology by having purchased (November 2018) a brand new digital C-Arm for fluoroscopy, angiography and minimally invasive cardiac procedures (OEC ELITE CFD 21 CARDIAC from GE HealthCare).


Apart from Degenerative Mitral Valve Disease, we operate on most canine and feline congenital heart diseases such as :

  • Mitral dysplasia / stenosis
  • Tricuspid dysplasia / stenosis,
  • Pulmonic stenosis

  • Atrial septal defect (including sinus venosus)
  • Ventricular septal defect
  • Patent ductus arteriosus
  • Tetralogy of Fallot


Bouton Contact-us


Dog going for a walk 2 days after mitral valve surgery at HOPia

devanture Hopia avec chien


DMVD is the most common acquired cardiomyopathy encountered in dogs. Small breed dogs over 5 years of age are particularly at risk. Cavaliers (for which a genetic predisposition has been identified), Dachshunds and Chihuahuas may have an early onset of the disease.

DMVD usually has a slow progression and all dogs may not develop clinical signs.


The heart has four valves (aortic, mitral, tricuspid, pulmonary), all of which can be concerned by the degenerative disease, although the mitral valve seems to be predominantly affected. The mitral valve is located between the left atrium and ventricle. The blood normally flows from the atrium to the ventricle, the latter will then contract strongly in order to eject the blood through the aorta to the rest of the body. The mitral valve, once closed, prevents the blood from returning to the atrium during ventricular contraction, allowing a unidirectional aortic flow. With DMVD, the mitral valve’s structure is modified into a thick and irregular flap which doesn’t close very well. As a consequence, it leaks, enabling the blood to reflux in the left atria during ventricular contraction.

Concurrent tricuspid degenerative disease is presented by 30% of these small breed dogs. More rarely, the aortic and pulmonary valves can be affected.

DMVD is a progressive process which worsens over time. The pressure within the left atrium gradually increases secondarily to the chronic leakage. It can also present with an acute onset in case of a chordae tendineae (cords connecting the valve to the ventricle) rupture. An acute increase of the left atrial pressure will induce an accumulation of blood upstream from the left atrium, namely, the pulmonary veins and lungs, ultimately leading to pulmonary oedema (« water in the lungs »). When this occurs, it is said that the dog is in Congestive Heart Failure (CHF).

teckel chirurgie cardiaque Clinique vétérinaire Hopia Versailles Grand Parc


Pulmonary oedema is a major cause of dyspnoea (difficulty to breathe) because the lungs are filled with fluid instead of air. The clinical signs associated with CHF are: lethargy, exercise intolerance, cough, increase in respiratory rate and amplitude in respiratory motions. If one of those clinical signs is identified, a veterinarian must be contacted urgently.


Unfortunately, no medication exists to slow the degenerative disease.

In case of minor leakage with no heart remodelling, no medication is needed and the dog will have serial heart-scans to monitor the progression of the disease over time. When the leakage increases in volume and the left atrial starts dilating, a drug called « pimobendane » has proven to be very efficient in delaying the onset of CHF. This medication both reduces the cardiac workload by dilating the blood vessels downstream from the heart, and enhances its pumping action.

Once the dog has suffered from a CHF, other medications will be added to its treatment plan like furosemide and benazepril.

Furosemide is a diuretic, which means that it promotes micturition therefore reducing fluid retention and delaying fluid build-up in the lungs. Benazepril is an ACE inhibitor, it helps to lower down the level of some hormones which have a negative impact on the heart that are often overly produced in advanced cardiac issues. It also contributes to regulate electrolyte abnormalities (particularly potassium) which can occur secondarily to the chronic use of diuretics.

A close monitoring of kidney blood markers and electrolytes is essential for patients receiving diuretics and/or ACE inhibitors.

picto medicament



In order to determine the stage of heart disease your dog is suffering from, we will conduct an extensive set of medical pain free tests thanks to our state-of-the-art equipment.

These analysis include:

  • chest radiographs

  • heart scan with colour Doppler (images & videos are needed for the assessment)

  • electrocardiogram

  • possibly accompanied by the dosage of NT-proBNP (Cardiopet)

Picture on the left : Dr JH Bozon leading the cardiac surgery


Staging a dog’s heart disease is important to follow the recommended therapeutic guidelines established by the ACVIM (American College of Veterinary Internal Medicine) consensus to best treat the condition. The therapeutic plan will also be adapted individually thanks to the complete description of the disease provided by the analysis of each dog.


This class comprises all animals « at risk » (because of their pedigree or breed) of developing the disease but that do not have any heart abnormalities upon clinical examination. They do not need any treatment.

For instance, a new-born Cavalier King Charles Spaniel is in Stage A because this breed is predisposed to DMVD even at a young age.


This class comprises dogs with a heart murmur without any other clinical signs. This stage is further subdivided into Stage B1 and B2.

  • The sub-stage B1 includes dogs without radiographic or echocardiographic evidence of cardiac remodelling in response to DMVD (no evidence of left atrial or ventricular enlargement) ; these dogs don’t need any treatment

  • The sub-stage B2 includes dogs with radiographic and/or echocardiographic evidence of left-sided heart enlargement; these dogs will benefit from the use of pimobendane (proven by the EPIC study – 2016)

SURGERY MIGHT BE RECOMMENDED in case of a « B2+ state »


This class comprises dogs displaying, or that have displayed, clinical signs of CHF (i.e. that have suffered from respiratory failure because of chronic or acute pulmonary oedema). At this stage, at least a tri-therapy must be instituted (pimobendane + ACE inhibitor + furosemide +/- spironolactone). Some dogs will also need sildenafil in case of superimposed pulmonary hypertension.

Life expectancy at this stage is very limited and statistically reduced to 6-18 months after the first onset of pulmonary oedema.



This class comprises dogs unresponsive to medical treatment, in other words, dogs receiving upper-range dosage of heart medication and still presenting clinical signs of CHF. At this stage, the veterinarian might prescribe amlodipine (in case of systemic hypertension), cough-suppressants (in case of left bronchial compression induced by the left dilated atrium), anti-arrhythmics, other diuretics (torasemide, thiazides), etc. Hospitalisation for oxygen therapy and IV administration of the drugs is often necessary at this stage.

SURGERY MIGHT BE RECOMMENDED (sometimes the only option)

We mainly operate on dogs suffering from stage C or very advanced stage B2 likely to progress to a stage C in the next months. We also operate on emergency stage D cases.

In order to ensure a reasonable success rate, the maximum tolerate age to consider surgery is 12 years old. The success rate drops down between 12 and 13 years of age, and after 13, we do not advise the surgery because of the uncertain peri-operative outcome.

Vétérinaire opération Hopia


Firstly, we require a complete heart work-up in order to evaluate if surgery is among the therapeutic options. We then evaluate the risks of heart surgery (around 10% when the best conditions are achieved) versus those of medical treatment. Surgery is never elected if the dog has not been on heart medication for at least 3 months.

Surgery for mitral valve repair is indicated in case of:

  • severe mitral prolapse

  • grade 4 mitral regurgitation (extending into the pulmonary veins)

  • severe chordae tendineae rupture

  • significant dilation of the left atrium

If surgery is an option, we require medical tests to insure that the dog isn’t suffering from other diseases that could compromise surgery or the post-operative outcome.

In any case, our goal is to make sure that your pet gets the best treatment recommendations considering his global health status.


Open heart surgery planning is a 2-month process – here are the 10-key steps in chronological order


Candidacy evaluation (heart status)

Please send us, through the contact formulary OR at, your dog’s latest heart-scan (pictures + video loops) and chest radiographs, his relevant medical history and his ongoing treatment plan.

  • Detailed recent physical examination and relevant history

  • Latest detailed cardiac ultrasound scan (images and more important the video loops including colour)

  • Latest chest radiographs

  • Electrocardiogram (ECG)
  • Arterial blood pressure measurement

  • NT-ProBNP dosage


Ask your veterinarian to perform the following tests (please send the complete digital version of these tests) 2 months prior to the presumed date of surgery

  • NT-ProBNP and Cardiac Troponin I dosages

  • Full abdominal ultrasound scan (must be particularly closely examined :  adrenal glands for features of Cushing’s disease, pancreas for signs of pancreatitis, search an occult tumour present)

  • Blood tests : haematology, complete biochemistry panel, electrolytes, C-Reactive Protein, SDMA, cPLi, T4, TSH, 4DX

  • Urinalysis including UPC ratio and bacterial culture (sampling by cystocentesis)

  • Full coagulation profile including antithrombin III dosage, D-dimer and fibrinogen

  • Blood type (DEA 1.1)


Interpretation of the results, validation that your dog fits the criteria for open heart surgery


Date scheduling for your dog’s surgery


Possible refinement of the therapeutic plan in order to optimise preoperative conditions


Additional exams potentially necessary before surgery


Plan to arrive between 1 and 3 days prior to surgery at HOPia


Pre-operative full check-up at HOPia the day before surgery




7 days hospitalisation in the Intensive care Unit

Bouton Contact-us

General guidelines
of open heart surgery for DMVD

Open-heart surgery implicates a large number of veterinarians working together, and the use of many machines and consumables.

The procedure’s success relies on the training, professionalism and cohesion of this team, from the first second to the last of this 7-day process.


Apart from the extracorporeal circulation machine, key pieces to the procedure, the necessary equipment is as follows:

  • 2 anaesthetic machines (isoflurane or sevoflurane)

  • 1 ventilator
  • 1 complete multiparameter monitoring device (ECG, heart rate, respiratory rate, invasive arterial pressure, central venous pressure, non-invasive arterial pressure, pulse oximetry, capnography, FiO2, fraction of anaesthetic gas expired, oesophageal and rectal temperatures)

  • 1 thermic generator able to warm up and cool down the body to the adequate temperature according to the step of the procedure

  • 1 four-plane tilting surgical table
  • 1 ultrasonographic scanner with colour Doppler and paediatric trans-oesophageal probe

  • 4 syringe and 2 perfusion pumps

  • 1 real-time clotting-time measurement machine

  • 1 real-time blood gas analyser

  • 1 real-time haematology and biochemistry analyser

  • 1 real-time electrolytes analyser

  • 1 implantable defibrillator equipped with paediatric pads

  • 1 pace-maker

  • fresh whole blood from a donor previously tested as compatible with the operated dog

  • blood typing tests

  • cross match tests to perform between donors and receivers

  • cell-saver (a machine enabling auto-transfusion)

  • a cardioplegic solution (that stops and protects the heart during the valve repair)

  • frozen sterile saline

  • ice

  • numerous consumables and injectable drugs

  • traditional equipment : aspiration, cautery with delicate calibration (thermofusion), microsurgery equipment, customised equipment (catheters, tubing..)

Heart-lung bypass machine – centerpiece of the intervention

The technical and human platform are important, the team must have a perfect cohesion but the most crucial point is the heart-lung bypass machinery which represents quite a challenge in small individuals.

At HOPIA, we are able to operate on Chihuahuas as small as 1,4 kg. To date, the few heart-lung bypass procedures were conducted on medium to large breed dogs inspired by human paediatric surgery.

In small breed dogs, extracorporeal circulation is a technical challenge because of their very small total blood volume. The tubing is customized to small individuals such as miniature dogs and cats. Heart-lung bypass procedures induce cardiac arrest, thus enabling the surgeon to repair the valves on a motion-free heart. The bypass takes over the lung and heart (pump) functions during the intra-cardiac surgical time.

What are the diffrent parts of the heart-lung bypass machine?

  • a venous line

  • two suction lines, one for the thoracic cavity and the other for the heart cavity

  • a tank

  • an oxygenator

  • a thermic generator able to control the blood and thus the body temperature

  • two suction pumps

  • an arterial line

  • an intermediate line for arterial blood sampling

  • a monitor displaying all the parameters’ live values

  • an anaesthesia circuit for isoflurane and sevoflurane

  • an hemofilter
  • a monitor displaying all the parameters’ blood values
illustration simplifié de la machine circulation extra-corporelle à la Clinique vétérinaire Hopia Versailles Grand Parc

The tubing is customized to the dog’s size. The circuit is filled with a priming solution prior to the procedure.

The perfusionist, working hand-in-hand with the surgeon and the anaesthetist, must master the extracorporeal circulation technique for the procedure to be a success.

Doctors Sabine and Jean-Hugues Bozon are the only veterinary surgeons in the world to possess a certificate in extracorporeal circulation.


It is important to maximise the number of steps that may be done on the conscious animal in order to reduce the anaesthetic time:

  • venous catheter placement in the two fore limbs

  • one venous and one arterial catheter placement in the hind limbs

  • urinary Foley catheter placement

  • left thoracic and neck clipping

The operating theatre is also prepped during that time and the surgeons start scrubbing.

Chien sous respirateur artificiel

The next steps are the following:

01. Premedication

02. General anaesthesia induction and intubation

03. Jugular vein and carotid dissection

04. Chest opening, lung reflection, pericardectomy enabling the access to the heart

05. Minimal aortic and pulmonary artery dissection

06. Heparin intravenous bolus given to induce a state of hypocoagulability with monitoring of the clotting time

07. Cannulation of the jugular vein and carotid artery

08. Induction of partial then total extracorporeal circulation

09. Transoesophageal hear-scan: a transoesophageal paediatric probe connected to an ultrasonographic scan equipped with colour Doppler is delicately inserted in the oesophagus in order to obtain successive images of the heart in median transversal and longitudinal cross-sectional planes. The surgeon analyses the mitral valve movements, the different segments and the regurgitation.

10. Ascending aorta catheterisation (cardioplegic cannula insertion): a catheter is delicately inserted from a lateral approach in the ascending aorta

11. Body temperature cooling: the body temperature is progressively lowered to 28°C and maintained at that level thanks to a thermic generator integrated to the extracorporeal circuit

12. Cardoplegic solution injection (cardoplegic solution mixed with own blood) in the coronary arteries via the aortic catheter to induce cardiac arrest

13. Left atrial incision and introduction of the left (in the left atrium) and right (on the surgical field) suction lines

14. Pre-placement of the artificial mitral valve chordae tendineae to insure a proper repair of the ruptured chordae. Double suture material of expensed polytetrafluoroethylen (ePTFE or GoreTex) are placed between the papillary muscles (reinforced by pledgets to avoid the muscle to tear) and the mitral valve. Four to six artificial chordaes are placed depending on the case.

15. Mitral annuloplasty: the aim is to tighten the mitral annulus in order to reduce the mitral regurgitation and thus to maintain a good systolic coaptation. The same material as the chordae is used (ePTFE) in the form of two sutures reinforced by pledgets at each commissure of the mitral annulus. In some cases, a new annulus made of ePTFE is customized and sutured into place to add support to the sutures. The mitral annulus is tightened based on the surgeon’s experience and the preoperative measurements (mitral annulus and aortic diameter at maximum opening).

16. The artificial mitral valve chordae tendineae are secured. The main challenge at this point is to find the perfect length and tension allowing optimal coaptation during closure of the mitral valve. This step is very dependent on the surgeon’s experience. The result is challenged using sterile fluids to fill up the left ventricle and apply pressure on the mitral valve.

17. Left atrium suture and intracavitary gas removal under ultrasonographic monitoring (using the transoesophageal probe) and aortic de-clamping.

18. The heart is then restarted. The heart beat is expected to restart after the intracoronary recurrent cardioplegic injections are discontinued. Intra-thoracic heart massage is performed and sometimes a pacemaker is temporary set in place or ventricular defibrillation is needed.

19. Control transoesophageal heart-scan: the mitral valve coaptation, residual mitral regurgitation, systolic function, ventricle blood volume and presence of gas are checked.

20. Body temperature is gradually increased and arterial pump flow is progressively reduced.

21. The carotid artery and jugular vein cannulas are withdrawn and the extracorporeal circulation is terminated.

22. Protamine, a heparin antidote is infused. Dobutamine is added to the perfusion plan if the invasive arterial blood pressure is too low or unstable. Protamine can indeed induce severe hypotension, bronchospasm and increase pulmonary vascular resistance. Ventilation and arterial blood pressure must therefore be perfectly monitored at that time.

23. Chest closure (the pericardium is not sutured).

24. Thoracic drain placement

25. Very slow awakening over 2-3 hours. During this crucial phase, all of the vital parameters (ECG, invasive BP, CVP, HR, RR, SpO2, pCO2, temperatures) and ventilation are closely monitored and their return to a normal level is very progressively obtained. The clotting times are checked and must return to a normal level. The arterial catheters enabling the measurement of invasive pressure are withdrawn just before the patient recovers (i.e. isoflurane is discontinued) once the arterial blood pressure has normalised. The dog is then transferred to the intensive care unit where an oxygenated and temperature and humidity controlled cage awaits (ICU Menix Operation System cages).

Once the mitral valve is repaired and the new chordae are set in place, the mitral prolapse is diminished if not abolished, the valval coaptation is appropriate and the mitral regurgitation is markedly reduced. The left atrium has an amazing plasticity which allows it to reduce to a normal size in sometimes no more than a week post-operatively if the tissue is still healthy enough and if surgery hasn’t been performed to late.

During the post-operative hospitalisation period, the treatment plan for congestive heart failure is adjusted and then often discontinued. Several platelet inhibitors and blood thinning drugs are prescribed to prevent thrombosis, the most common complication observed during that phase.

The post-operative care is a real challenge!

It is a very critical phase during which the dog may die because many organs have suffered from the extracorporeal circulation, even the blood, to start with, because it has flown outside of its usual body. A complete blood panel, urinalysis, radiographic and ultrasonographic scans are performed daily during the week following surgery.

Apart from thrombosis (clot formation), the possible complications are:

  • Sudden cardiac arrest

  • Respiratory failure

  • Haemorrhage

  • Anaemia (sometimes haemolytic)

  • Acute pancreatitis

  • Tachycardia

  • Diaphragmatic paralysis

  • Coronary or cerebral gas embolism

  • Systemic inflammatory response syndrome
  • Acute right sided-heart failure

  • Acute pulmonary arterial hypertension

  • Focal infection among which the worse is endocarditis

  • Stroke (hypoxic, haemorrhagic or thrombotic)

All the signs of possible complication development are checked during the week following surgery and the treatment plan is adjusted accordingly to avoid a fatal outcome.


If the surgery is a success, your pet will always have a healed heart as long as you respect the post-surgery exercise restrictions.

About 80% of the dogs will stop medication after 3 months. A diminution of the heart cavities will be observed, a significant loss of mitral regurgitation that will become moderate or inexistent, enabling your dog to live normally without having breathing difficulties or being tired.


Pictures on the right: Mitral valve repair performed by Dr JH Bozon. Top : Peroperative Transoesophageal Echocardiographye (Dr Sabine Bozon). Bottom : Post-opertaive trans-thoracic Echocardiography (Dr Sabine Bozon)

avant / après chirurgie mitrale

The post-operative risks

Death on the operating table can occur; it is usually due to hemorrhage or low blood pressure or acute pulmonary hypertension…. The worse the cardiac failure stage, the riskier. There is also a high risk of death during the post-operative week in intensive care, when many complications may occur.

Apart from thrombosis (clot formation), the possible complications are:

  • Sudden cardiac arrest

  • Respiratory failure

  • Haemorrhage

  • Anaemia (sometimes haemolytic)

  • Acute pancreatitis

  • Tachycardia

  • Diaphragmatic paralysis

  • Coronary or cerebral gas embolism

  • Systemic inflammatory response syndrome
  • Acute right sided-heart failure

  • Acute pulmonary arterial hypertension

  • Focal infection among which the worse is endocarditis

  • Stroke (hypoxic, haemorrhagic or thrombotic)

Since 2018, all of our hearts but one restarted after the mitral valve repair.

We are equipped to detect and treat most of these risks. A complete health check is performed on a daily basis along with many other analysis or diagnostic imaging. In a few of cases, an incurable complication occurs.

cardiac surgery schedule

Open-heart surgery

Regular cardiac surgeries are performed throughout the year at the HOPIA clinic.

Open heart surgery requires the presence of at least 10 professionals who are trained in this very complicated procedure.

The surgeries are organized about 2 months in advance.

Given the many requests from all over the world, our schedule is usually very full but we give priority to emergencies (advanced C or D heart dogs) as well as to King Charles Cavaliers for whom « Emergency slots » can be unlocked.

Non-urgent surgeries are likely to be postponed in order to help a dog who is suffering.

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