Cardiac Surgery
World Small Animal Veterinary Association World Congress Proceedings, 2011
Peter Vogel, VMD, DACVS
Southern California Veterinary Specialty Hospital, USA

What is Cardiac Surgery?

 Any procedure performed on the ventricles, atria, cardiac valves, and great vessels

 May be closed procedures which can be performed without opening major cardiac structures

 May be open procedures which require circulatory arrest

 Inflow occlusion (procedures < 5 minutes) with or without hypothermia

 Cardiopulmonary bypass (not discussed in these lectures)

Perioperative Considerations

 Must undergo a thorough diagnostic evaluation

 Incomplete or inaccurate diagnosis can be devastating

 Cardiac catheterization, CT or standard angiography (no longer routinely necessary)

 Anatomic 2D, m-mode, color flow and spectral Doppler, live 3D and transesophageal echocardiography

 Animals undergoing cardiac surgery usually have some degree of cardiovascular dysfunction

 Wherever possible, cardiac abnormalities should be corrected medically prior to surgical intervention


 Congestive heart failure (pulmonary edema, pleural effusion, etc.)

 Not fundamentally different from other soft tissue surgery

 All principles of good surgical technique apply

 Motion from cardiac contraction is the aspect that makes cardiac surgery different

 Strategies for arresting cardiac motion are available

 Closure of cardiovascular structures require precise suturing techniques:

 Typically use fine suture (4-0 or smaller) with swaged-on atraumatic needles

 Avoid palming instruments when suturing vascular tissue

 Hand tying of knots is fast and produces a tighter, more secure knot

 Fundamental skill for cardiac surgery

 One handed tie preferred

 First 2 or 3 throws in same direction, and finish with a square knot

Suture and Instrumentation

 Polypropylene, nylon, braided polyester, common sutures in 3-0 to 6-0 size ranges

 Heavy gauge silk for ligatures

 Swaged-on taper point needles

 Double-armed suture (needles on both ends) very useful in cardiovascular surgery

 Continuous horizontal mattress pattern oversewn with simple continuous is the most secure and generally preferred suture pattern

 Proper instrumentation is essential

 Basic surgical instruments along with

 DeBakey atraumatic tissue forceps

 Metzenbaum scissors

 Potts 45 degree angled scissors

 Long needle holders

 Vascular clamps (variety of styles and sizes)

Conditions Amenable to Surgical Correction Without Inflow Occlusion/Bypass

Patent Ductus Arteriosus

 Ductus arteriosus is a fetal vessel that shunts blood away from (pulmonary artery) lungs back to systemic circulation (descending aorta)

 Closes shortly after birth

 Continued patency of the ductus arteriosus for more than a few days after birth is consistent with PDA

 Most common congenital cardiac defect in dogs (25–35% of congenital malformations in dogs)

 Exists, but rare in cats

 More common in purebreds, slight predilection for females.

 Poodles, Yorkshire Terriers, Maltese, Bichon Frise, Cocker Spaniels, Pekingese, Collies, Shelties, Pomeranians, Welsh Corgis.

 Heritability documented in Poodle and Welsh Corgi


 Allows left to right shunting, resulting volume overload, leading to left ventricular and atrial dilation, progressive myocardial deterioration, and left sided congestive heart failure

 Most dogs with PDA die of heart failure before 1 year of age


 Continuous cardiac murmur (machinery murmur) at left heart base is classic PE finding, often with palpable thrill

 Bounding femoral pulses


 Left atrial and ventricular enlargement

 Enlargement of the vessels

 Characteristic aortic bulge (dilatation of descending aorta)

 ECG findings

 May or may not show changes, more changes as cardiac dilatation occurs


 Most diagnostic

 Helps rule out concurrent defects

 Helps rule out right to left shunts (although clinical signs of this are different)


 Standard surgical correction is ligation of the ductus

 Left 4th intercostal thoracotomy

 Vagus nerve is identified and isolated

 Gently dissect ductus and pass two silk ligatures (O) around ductus

 Excellent prognosis with surgical therapy

 Less than 5% mortality

 Aortic aneurysm or PDA rupture can cause complications

 Transvascular occlusion now standard of care (coil embolization, Amplatz ductal occluder)

 Surgery relegated to failures or very small dogs (rare)

Vascular Ring Anomalies

 Can occur in any breed

 German Shepherd and Irish Setter seem to have a predilection for PRAA


 Developmental anomalies of the great vessel which result in entrapment of the trachea or esophagus in complete or incomplete ring of vessels


 Usually normal until weaning, when signs of post-prandial regurgitation occur

 Clinical signs caused primarily by esophageal obstruction

 Coughing and respiratory distress may be present with aspiration pneumonia, or with tracheal compression due to double aortic arch


 Esophageal dilation cranial to heart base

 Contrast esophagrams


 Angiography (rarely performed)


 Medical management unrewarding

 Surgical intervention

 Divide vascular ring and transect peri-esophageal fibrous bands

 Most corrected via left lateral thoracotomy, except aberrant right subclavian


 Persistent regurgitation is common

 Loss of neuromuscular function and lack of aboral peristalsis

 Earlier intervention is probably better, but many older dogs do well

 Most report good or excellent outcomes

Ventricular Septal Defects

 Failure of development of the intraventricular septum

 Membranous defects more common than muscular

 10% of congenital heart defects in dogs.

 Most common congenital malformation in cats

 English springer spaniels, Lakeland terriers, West Highland white terriers, basset hounds, English bulldogs, Akitas, and Shih Tzu have increased risk

 Polygenic in keeshonden


 Dependent on defect size and location

 Restrictive defects allow left to right shunting

 Left ventricular overload leading to CHF

 High flow shunts

 Progressive pulmonary arteriopathy

 Pulmonary hypertension

 Right to left shunting (Eisenmenger's syndrome)

 Aortic valve insufficiency is associated with VSD

 Prolapse of right coronary aortic leaflet into the defect


 Often not symptomatic in young animals

 Eventually see signs of left-sided CHF


 Exercise intolerance

 Systolic murmur at the right sternum/apex

 Diastolic murmur due to aortic insufficiency can give the murmur a continuous quality ("to and fro")

 Angiography (rarely done anymore)

 Echocardiography with color flow Doppler

 Higher velocity shunting equates with a smaller defect and a better prognosis


 Surgical correction indicated for hemodynamically unrestricted defects

 Prevent CHF

 Prevent worsening of aortic insufficiency if present

 Radiological evidence of pulmonary vascular dilatation

 Echocardiographic evidence of left ventricular dilatation

 Shunt velocity > 3.5 m/sec (> 5 m/s for left to right defects)

 Right ventricular outflow tract ejection velocity increased causing relative pulmonic stenosis

 Pulmonary Arterial Banding

 Increase right ventricular systolic pressure

 Left 4th intercostal approach

 Large cotton or Teflon tape passed around pulmonary artery just distal to pulmonic valve

 Generally requires a 2/3 reduction in pulmonary arterial diameter

 Attenuated pulmonary arterial pressure decreased to < 30 mm Hg

 Open repair requires bypass

 Interventional cardiac catheterization closure on the horizon


 Minimal morbidity and mortality

 Over-tightening of pulmonary band can lead to reversal of flow through defect

 Progressive tricuspid regurgitation and RVO tract obstruction leading to reverse flow also reported


 Long term data is not available

 Short term palliation good. One report out up to 7 years.

 Cats do better than dogs

 Definitive open repair or closure via catheter occluder probably curative

Tetralogy of Fallot

 Complex congenital defect

 RVO tract obstruction


 Over-riding aorta

 Right ventricular hypertrophy

 Genetic in keeshond


 With large RVO obstructions:

 Markedly elevated right ventricular pressure

 Right to left shunting


 Progressive polycythemia

 Sudden cardiac death

 With large VSD

 Similar to VSD alone

 Balanced VSD and RVO obstruction

 Similar to VSD that has been banded



 Moderate to severe exercise intolerance

 Exertional tachypnea

 Syncopal episodes

 Thoracic radiographs

 Right ventricular enlargement

 Dilation of pulmonary artery


Indications for Surgery

 Severe exercise intolerance

 Polycythemia (HCT > 65%)

 Resting hypoxemia (PaO2 < 70%)


 Goal of surgery is to alleviate right outflow obstruction and to create a left to right shunt

 Animals with a natural left to right shunt have acyanotic tetralogy and rarely require surgery

 Balloon valvuloplasty + modified Blalock-Tausig shunt

 Definitive correction requires bypass


 Short term palliation successful

 Long term palliation has not been demonstrated

 Successful definitive correction reported (2 dogs)


Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker)

Peter L. Vogel, VMD, DACVS
Southern California Veterinary Specialty Hospital

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