Kapitel 106 – cardiac surgery

Question 1

Which is the dominant coronary artery in dog and in cats?

Answer 1

a. Dogs: left coronary artery
b. Cats: right coronary artery

Question 2

What are the phases during a cardiac cycle?

Answer 2

a. filling phase
b. an isovolumetric contraction phase
c. an ejection phase
d. an isovolumetric relaxation phase

Question 3

what determines the stroke volume?

Answer 3

a. Preload – reflected by the end diastolic volume and end diastolic pressure
b. Afterload – the amount of systolic wall stress the heart has to overcome before it can eject volume.
c. Contractility - represents the intrinsic contractile state of the heart independent of preload and afterload.

Question 4

For how long can a surgical procedure be performed with venous inflow occlusion and circulatory arrest?

Answer 4

a. 2 min or less in a normothermic patient
b. < 4 min with body hypothermia (32-34 degrees)

Question 5

What suture material is commonly used in cardiac surgery?

Answer 5

a. Polypropylene, polytetrafluoroethylene (PTFE) and braided polyester in sizes of 3-0 to 6-0
b. Heavy-gauge (1) silk ligatures for ligation of large cardiovascular structures, making tourniquets, or securing cannulae for cardiopulmonary bypass.

Question 6

Which approach is recommended for inflow occlusion?

Answer 6

Inflow occlusion can be accomplished from a left or right thoracotomy or median sternotomy but direct access to the venae cavae and azygos vein for inflow occlusion is obtained readily from a right or median sternotomy (more difficult from the left side)

Question 7

How do you avoid air embolism when operating on the left side of the heart?

Answer 7

By indicing complete cardiac arrest by crossclamping the acending aorta.

Question 8

When is the most critical time after cardiopulmonary bypass surgery and what are the major complications?

Answer 8

a. The first 12 h
b. hemorrhage, hypoxemia, circulatory collapse, cardiac arrhythmias, low urine output, and electrolyte and acid-base abnormalities

Question 9

which type of hemorrhages is most common after cardiopulmonary bypass: surgical or biological? And why? How is it best treated?

Answer 9

a. Biological because of possible Ddilutional and consumptive thrombocytopenia, acquired platelet dysfunction, consumptive and dilutional coagulopathy, and fibrinolysis after surgery

b. Managed conservatively with supportive treatment and blood products (fresh whole blood preferred)

Question 10

What radiological signs can you see in patients with patent ductus arteriosus?

Answer 10

moderate to severe left atrial and ventricular enlargement, enlargement of pulmonary vessels, and a characteristic dilatation of the descending aorta on the dorsoventral view.

Question 11

What ecogardiographic changes may you see in patients with patent ductus arteriosus?

Answer 11

Tall R waves (>2.5 mV) on a lead II electrocardiogram are supportive of the diagnosis but are not always present (only 63% of cases).

Question 12

What are the clinical signs in patients with reverse (right to left) patent ductus arteriosus?

Answer 12

a. exercise intolerance and pelvic limb collapse on exercise.
b. Cyanosis is a hallmark physical finding. Classically, the cyanosis is “differential” (i.e., more severe in the caudal mucous membranes) because of the position of the ductus in relation to the bifurcation of the brachiocephalic trunk, but it may be present cranially as well.
c. Femoral pulses are normal.
d. There is usually no cardiac murmur
e. Thoracic radiographs show evidence of biventricular enlargement and a markedly enlarged pulmonary artery segment. The pulmonary arteries may appear enlarged and tortuous or normal.

Question 13

When should surgical ligation preferably be performed and in what patients?

Answer 13

a. In animals with a left-to-right shunt
i. surgical ligation of a right-to-left or bidirectional patent ductus arteriosus is contraindicated.
b. Any time after 8 weeks and before 16 weeks.
c. In older animals than that, as soon as possible.

Question 14

What is the surgical approach for patent ductus arteriosus ligation?

Answer 14

a. through a left fourth intercostal thoracotomy in dogs
b. through a left fourth or fifth intercostal thoracotomy in cats

Question 15

What are the different types of pulmonic stenosis?

Answer 15

a. type A pulmonic stenosis: have a normal annulus diameter with an aortic:pulmonary ratio ≤1.2
b. Type B pulmonic stenosis have a hypoplastic annulus diameter with an aortic:pulmonary ratio ≥1.2.

Question 16

what are the treatment options for pulmonic stenosis?

Answer 16

a. dilatation valvuloplasty, pulmonary valvulotomy or valvulectomy, and patch-graft valvuloplasty.

Question 17

What is the treatment of choice for type A pulmonic stenosis?

Answer 17

a. Balloon valvuloplasty
b. (not advised in patients with concurrent anomalous left coronary artery)

Question 18

What is the most common presentation of aortic stenosis in dogs?

Answer 18

Formation of a fibrous band in the subvalvular area

Question 19

What is the most important cause of aortic regurgitation? What is the most prominent finding of physical examination?

Answer 19

a. Infective endocarditis
b. Diastolic murmur at the left cardiac base and hyperkinetic or bounding arterial pulses

Question 20

What is the most prominent finding of physical examination for ventricular septal defect?

Answer 20

A systolic murmur at the right sternum

Question 21

Name the classification of artrial septal defects

Answer 21

a. ostium secundum atrial septal defect (most common)
b. sinus venosus defects
c. coronary sinus atrial septal defect

Question 22

What is the most prominent finding of physical examination for Teratology of fallot?

Answer 22

a moderate to severe cyanosis that is unresponsive to supplemental oxygen. Cyanosis typically worsens with exercise.

Question 23

what is characteristic for Teratology of fallot?

Answer 23

a. pulmonic stenosis
b. perimembranous ventricular septal defect
c. a overriding aorta
d. and secondary right ventricular hypertrophy.

Question 24

What are the objective indications for surgery for Teratology of fallot?

Answer 24

a. exercise intolerance
b. polycythemia (hematocrit >70%)
c. resting hypoxemia (arterial oxygen saturation <60%)

Question 25

What are the surgical options for mitral valve replacement?

Answer 25

a. mechanical valves or glutaraldehyde-fixed bioprosthetic valves. b. Because of size limitations in currently available valve prostheses, valve replacement is limited to dogs weighing 10 kg or more.

Question 26

Which if the mitral valve replacements are preferred in dogs? Why?

Answer 26

a. bioprosthetic valve are preffered. b. Mechanical valve are thrombogenic and require lifetime anticoagulation therapy, which is challenging in dogs. c. The incidence of catastrophic valve thrombosis and death was relatively high (56%), despite warfarin therapy

Question 27

Which is the most common cardiac neoplasia in cats and dogs?

Answer 27

Cats: Lymphosarcoma and metastatic neoplasia Dogs: hemangiosarcoma

Question 28

When is placement of a permanent pacemaker indicated?

Answer 28

a. high-grade second- or third-degree atrioventricular (AV) block b. sick sinus syndrome c. sinus arrest d. other chronic bradyarrhythmias that are causing clinical signs (e.g., syncope, episodic weakness, exercise intolerance

Question 29

what type of pacemaker is most commonly used in veterinary medicine?

Answer 29

single-chamber, ventricular inhibited synchronous pacing with (VVIR) or without (VVI) rate modulation.

Question 30

What can affect the contractility of the heart?

Answer 30

contractility is affected by the amount sympathetic stimulus, diseases of the myocardium, cardiac drugs, changes in cardiac mass (hypertophy of the heart muscles). The greater the contractility the greater the stroke volume.

Question 31

What Suture material should you have available for cardiac surgery and what instruments?

Answer 31

Polypropylene, Polytetraflouroethylene, braided polyester (3-0 to 6-0). Double armed suture with needles in both ends, pledgets in a variety of sizes (3x7mm, 4x 9mm) to buttress sutures. Heavy gauge silk (1-0) suture for ligation of large strucktures, tourniques and so forth. Debakey forceps and metsenbaum scissors, potts scissors, needle holders – long, vascularclampsnon- crushing, angled forceps,

Question 32

What is an inflow occlusion and what is it used for?

Answer 32

a tourniquet is placed on the caudal v. cava and the v. azygous+cranial v. cava, avoiding the phrenic nerve, readily accessible from a right lateral thoracotomy for example. Can only be done for ideally 2 min maximum, but can potentially be repeated, or arrest time can be prolonged to 4-5 minutes with hypothermia, 32-34 degrees. Risk for cardiac arrest if longer, or ventricular fibrillation if colder the 32 degrees. Only for short procedures and very bad if the procedure is not finished in the time. Ventilation stopped during procedure, to prevent the blood being pressed into the heart from the lungs. Inflow stoped, heart may need massage or I fibrillation direct shock to defibrillate, once started again, the incision can be repaired with suture material, and the vascular clamped removed

Question 33

What is cardiopulkmonary bypass? and Describe the major steps of cardiopulmonary bypass?

Answer 33

an extracorporal bypass maschine provides oxygenated blood for the circulation. Gives a motionless, bloodless surgical field. Tripel lumen catheter placed I jugular vein before surgery – for monitoring First arterial cannulation, In dogs the femoral artery is preferred to the aorta. 1 or 2 venous catheters (venous cannulation) to divert blood away from the right heart to by pass machine. Hemodilotion to counter increased viscosity due to hypothermia -hct of 25-28% preferred. Crystalloid used to dilute during the ciruit. Cross clamping the ascending aorta, cooling the myocardium with cardioplegia solution into coronary circulation by a cannula into ascending aorta before cross clamping. De-air heart before discontinuing – anesthesiologist will help by inflating lungs pushing blood back into heart.

Question 34

Name five dog breeds that are predisposed for PDA

Answer 34

poodles, keeshond, maltese, bichon fries, Yorkshire terrier, shelties, cockerspaniels, collies, Pekingese, Pomeranians, welsh corgies

Question 35

What is a reverse PDA?

Answer 35

a small percent develop hypertension in the pulmonary circulation, giving the reverse flow o blood from left to right, shunting unoxygenated blood into the descending aorta – leading to cyanosis which is worse in the back. Most commonly this is already from birth, this does diminish the risk for left sided heart failure, but causes excersize intolerance, hypoxemia, and polycytemia

Question 36

Please list the major steps of PDA ligation

Answer 36

left 4 th intercostal thoracotomy, vagal nerve courses directly over the pda, , the vagal nerve is lifted but incising the tissue it courses in and is retracted dorsally, blunt dissection of the pda, parallel caulally and at 45 degree angel cranially, then pass silk suture 1, and double ligate, start at the aorta side then the pulmonary trunk side. Close.

Question 37

You are doing your third PDA surgery, and it starts to bleed during the dissection…..what are your options?

Answer 37

simple ligation no longer an option…you have 3 choices. 1) the duct can be closed with 3-4 wide biting buttress mattress sutures across the pda. This closes duct and provides tamponade of the tear…this is safer then dividing the duct. But you risk significant residual shunt flow. 2)Divide an oversew between vascular clamps. The openends are closed with pledgets buttressed mattres sutures interrupted or continuous + oversewn with continuous, technically demanding. Any residual flow is almost never hemodynamically significant and almost never warrents a second surgery 3. Jackson henderson technique

Question 38

In dogs, what is the cause for pulmonic stenosis?

Answer 38

usually valvular stenosis, but can also be subvalvular or supravalvular. The valves kan be fused or dysplastic (80%). Then secondary hypertropfhy of the right ventricle further worsens the outflow obstruction

Question 39

You are shown an electrocardiogram of an English bulldog with abdominal distension, you are suspecting a pulmonic stenosis, what would you be locking for on the printout?

Answer 39

prominent s waves in the I lead, because this is indicative of a right axis shift and right ventricular hypertrophy.

Question 40

Ulrika comes to you and talk fast in babble english about this patient, you gather shes done an echocardiography, what are the key words you are trying to listen for in order to confirm your suspicion of pulmonary stenosis?

Answer 40

right ventricular hypertrophy, dilation of the main pulmonary artery, malformation of the pulmonic valve, increased pulmonic ejection velocity.