What is Open Heart Surgery?
Open heart surgery is a term which has come to be associated with the use of Cardiopulmonary Bypass (ie a heart-lung machine) to enable surgical repair of both congenital and acquired heart conditions. The advantage to using cardiopulmonary bypass is that it allows surgery to be performed with the heart isolated from the rest of the circulation. This isolation allows the heart to be opened and the interior structures of the heart visualized, without blood being present. In addition, the heart can be stopped to allow surgery to be performed without the added complication of movement. For this to occur, the heart lung machine must assume the pumping function of the heart, and also the functions of the lung which is also "bypassed" during the procedure.
Curative versus Palliative Intent?
It is important to be realistic when considering the aim of open heart surgical procedures. The intent of the surgery may be Curative or Palliative.
Curative Intent: In this instance, the aim of the surgery is to completely correct the underlying anatomical abnormality (for instance, closure of a VSD). Correction of the anatomic defect may or may not equate to complete cure. This is because in some instances (eg PS) the anatomic lesion may have lead to secondary structural changes in the heart which, although improved by the surgery, may never fully resolve (see the descriptions of each lesion for more information).
Palliative Intent: In this instance, the aim of surgery is not to cure the patient, but rather to alleviate the patient's clinical signs. The most common example for this would be resection of cardiac masses. In some instances, the surgery is not able to completely remove the mass and rather is aimed at removing as much of the mass as possible for improved blood flow and cardiac function. Since the mass will re-grow following such a procedure, life expectancy may or may not be extended. The ultimate aim of surgery for these patients is to improve quality of life.
What procedures can be performed?
We are able to perform almost all surgical procedures currently available for correction of cardiac disease in humans. Procedures tend to fall into one of two classifications:
Congenital Heart Defects: This term implies that the patient was born with a heart defect. Open heart surgery can be considered for a variety of such lesions including Atrial Septal Defect (ASD), Ventricular Septal Defect (VSD), Double Chambered Right Ventricle (DCRV), Pulmonic Stenosis (PS), Tetralogy of Fallot, Cor Triatriatum, Tricuspid Valve Dysplasia (TVD) or Mitral Valve Dysplasia (MVD). Surgical correction for Subvalvular Aortic Stenosis (SAS) is not currently offered as previous studies have demonstrated that life expectancy is not improved even following an apparently successful procedure.
Acquired Heart Disease: This term implies that the patient was born with normal cardiac anatomy, and developed cardiac disease later in life. Examples for this type of heart disease include Degenerative Mitral Valve Disease (DMVD) and Cardiac Tumors.
What is the success rate for Open Heart Surgery in dogs?
When success is defined as the patient surviving the operative procedure and leaving the hospital alive, the current success rates are around 70%. There may be small differences in success rate between different lesions, sizes of patients, ages of patients and many other factors, but overall success rate remains around 70%. The entire open heart surgery team at UC Davis is committed to improving these success rates until they match those obtained in humans for similar procedures. However, the reality at present is that open heart surgery is associated with significant risk during or shortly after the procedure.
What are the advantages and disadvantages of Valve Repair versus Replacement?
Valve Repair - The major advantages of valve repair relate to the fact that we are preserving the patients own valve. This is advantageous as we do not have to buy a costly prosthesis (replacement valve), and because the patient's own tissues are preserved and therefore there is no need for anti-coagulation. The major disadvantage of this approach is the difficulty in repairing valve lesions in dogs. Unlike humans, who present very early in the course of their disease, dogs usually present relatively late in the course of the disease. By this time, the valve is usually extremely abnormal and repair aimed to fully correct the leaky valve is often unrealistic. As a consequence, most patients still have mild to moderate leak through the valve, even after a "successful" repair. This makes the post-operative management of the patient extremely challenging. The good news is that if the patient survives the procedure, the residual leak is usually well tolerated with 75% of patients having resolution of their congestive heart failure and no longer requiring diuretic therapy.
Valve Replacement - The major advantage of valve replacement is that the patient finishes the procedure with no residual leak. This leads to the patient being somewhat easier to manage in the post-operative period, and the heart recovering rapidly to relatively normal structure and function in most patients. Two types of replacement valve are available:
Mechanical Valves - Although these were found to be successful in the short term, we no longer recommend implantation of mechanical valves in dogs. This is due to the fact that mechanical valves are exquisitely dependant on anti-coagulation (preventing the blood from clotting) in order to function. Any lapse in anti-coagulant therapy leads to clot forming on the valve which is commonly fatal for the patient. This is a life long problem for the patient and if anti-coagulation becomes disturbed at any point during the dog's life, there is a high possibility that it will lead to death. With this risk, and previous experience in which all dogs with mechanical valves died due to clot at some point post-operatively, we no longer recommend mechanical valve placement.
Tissue Valves - Following implantation, tissue valves (either glutaraldehyde fixed porcine aortic or bovine pericardial valves) only require anti-coagulation for 3 months. After this period of time the valve is covered with the patient's own tissue and clot formation is no longer a concern. However, another relatively common problem exists with use of tissue valves. This problem is the formation of a foreign body type reaction to the valve (Pannus) which leads to rapid damage of the valve, return of leak, heart failure, and ultimately death of the patient, usually occuring within 6 months of valve implantation. Unfortunately, we currently have no method for determining before surgery which dogs will form Pannus and which will not. Additionally, there is no really effective treatment for prevention of or treatment of Pannus should it occur.
Due to problems with Pannus formation, no one has ever implanted a significant number of tissue valves in dogs. Thus, we have little idea of long term outcome for dogs following tissue valve implantation, assuming they can avoid initial Pannus formation. It is likely that, as with humans, dogs will gradually damage the valve causing failure over time. In humans, this process takes 10-15 years, which would mean that, in dogs, the valve would last the lifetime of most dogs. However, we do not know if the valve lifespan is equivalent in the canine population.
Due to these uncertainties regarding tissue valve use in dogs, we currently only recommend tissue valve placement in patients where valve repair is considered impossible.
What is the cost of the procedure?
The current average cost of an open heart surgical procedure at UC Davis is $10,000-12,000 depending on the exact procedure and post-operative course. This figure includes all pre-operative tests, the procedure itself, and all post-operative care of the patient until discharge. Owners should also factor into their decision the cost of travelling to UC Davis, and lodging during their stay in the Davis area.
How long does the procedure take?
The schedule for surgery usually entails the owner and patient spending approximately 1 week in Davis. Initial appointments are made to see Dr Griffiths on Monday, at which time any final diagnostic tests are undertaken. Surgery is performed on Tuesday, with most procedures lasting 3-5 hrs. Most patients spend the following 2-3 days in the critical care unit, during which time they recover relatively rapidly. By the time of final discharge (usually 5-7 days after the surgery), the patients are essentially back to normal and require no special nursing care. At discharge the dogs are walking, eating and drinking normally, and usually the most difficult part of the aftercare is preventing the dog from doing too much exercise.
What aftercare is needed?
The surgical incisions take several weeks to heal, during which time exercise should be restricted. Stitches should be removed by your veterinarian 10-14 days after the procedure. Periodic follow up evaluations may be performed with your veterinarian, or UC Davis. Dr Griffiths will remain in contact both with the client and the referring veterinarians (cardiologist and general practitioner), and is available for consultation whenever the need arises. Most dogs require some continued medication following the procedure, usually in an effort to aid return to normal heart muscle function.
How do I schedule a procedure?
Due to high demand, there is commonly a waiting list for surgery of several weeks to months (emergency surgery is not currently an option). Fortunately, most dogs who are appropriate candidates for open heart surgery can tolerate the wait with appropriate medical care.
Prior to discussion of scheduling, the patient should be evaluated by a medical cardiologist (preferable board certified). Access to the findings of your cardiologist is essential in providing an accurate assessment for your dog and in planning the surgical procedure to be performed. In order to accurately assess the case, the following checklist items should be available before consulting is sought.
1: Body Weight, Age, Gender and Breed of the patient.
2: A brief synopsis of the medical history, especially that which pertains to episodes of congestive heart failure. This information is best conveyed as a letter of referral from your cardiologist. Any other medical conditions (eg renal disease) should also be clearly stated in the synopsis.
3: Echocardiography images and measurements should be supplied. Ideally this should include video and still images of the lesion.
4: Radiographs, complete blood count, serum chemistry panel, and urine analysis should all be supplied where available.
5: Blood type is essential and should be supplied prior to scheduling of the case.
Contact for a consultation should be made by the owner, referring veterinarian or both directly to Dr Griffiths (firstname.lastname@example.org, or 530 754 0334). The consultation will include phone conversations between Dr Griffiths, the veterinary cardiologist and the owner, as well as a review of the appropriate medical data (radiographs, echocardiography findings, blood work etc). Following consultation, if appropriate, the patient will be placed on the waiting list and possible surgery dates discussed.
What if $10,000 -12,000 dollars is too much for me to afford?
The procedure for open heart surgery at UC Davis is exactly the same as that which is performed on human patients. Although $10,000 - 12,000 is a significant expense, the cost is actually very minimal when the complexity of the surgery, the huge number of doctors involved in the team and the intense one-on-one care the dog and client receives are taken into account. However, we realize that for many clients the price is simply out of reach. Unfortunately, no mechanism currently exists for subsidizing open heart surgery procedures. However, for some procedures that are performed using the open heart machine, other alternative surgical procedures exist which do not require Cardiopulmonary Bypass. Consultation with Dr Griffiths will always lead to discussion of these options, where applicable, and may present alternatives which offer a significantly lower financial cost.