Cardiovascular Surgery Flashcards
What are the 3 most common congenital cardiac disorders in dogs and cats? Dogs specifically?
- patent ductus arteriosus
- vascular ring anomalies
- VSD
aortic and pulmonary stenosis
What is patent ductus arteriosus? What does this cause?
failure of the fetal ductus arteriosis, which connects the pulmonary artery and the aorta, to close >3 days following birth
left to right shunt = volume overload and hypertrophy in the left ventricle causes mitral valve distension and regurgitation = LEFT SIDED CHF, pulmonary edema
What is the purpose of the ductus arteriosus in the fetus?
shunts blood from the pulmonary artery to the aorta, directing venous blood away from the fetal lungs
What is Eisenmenger’s syndrome? What causes it? What does it result in?
reverse PDA - increased pulmonary hypertension reverses the direction of the PDA shunt to right to left (NO TREATMENT)
untreated PDA or pulmonary hypertension after birth
less likely to develop left-sided CHF, but causes severe hypoxemia and cyanosis
What is the most common signalment associated with PDA? In what breeds has a heritable basis been identified?
female pure bred small breeds - Bichon Frise, Chihuahua, Poodle, Pomeranian, Yorkie
Poodles and Welsh Corgis
What clinical signs are seen in patients with PDA?
younger dogs with:
- cough (pulmonary edema)
- shortness of breath
- left-sided heart failure
- machine murmur
(can be asymptomatic)
What clinical signs are seen in patients with reverse PDA?
older dogs with:
- exercise intolerance
- pelvic limb collapse
- cyanosis
- polycythemia: increased PCV for compensation
What are the 2 most commonly heard on auscultation in patients with PDA? What other cardiac signs are associated?
- continuous machinery murmur heard best at the high left heart base or left axillary region
- palpable cardiac thrill
- strong femoral pulse
- tall R waves or wide P waves
- stunted growth
What 3 thoracic radiograph findings are consistent with PDA?
- left atrial and ventricular enlargement
- dilation of descending aorta
- dilation of pulmonary artery
How is an echocardiogram used to diagnose PDA?
confirmation
- left atrial enlargement
- left ventricle dilation
- pulmonary artery dilation
- “micro bubble”
What is seen on CBC/chem in patients with PDA?
polycythemia - increased RBC to compensate for hypoxemia
When is surgical management indicated in patients with PDA? What 2 medical treatments are recommended prior to surgery?
all dogs with L to R shunting
- Furosemide - pulmonary edema, CHF
- beta adrenergic blocker or calcium channel blocker - atrial fibrillation
When is PDA surgery contraindicated?
R to L shunting
What 2 surgical treatments are used for PDA?
- minimally invasive coil embolization or Amplatzer ductal occluder* - more complete occlusion, less complications, limited by patient size
- surgical ligation - less expensive, no limitations for patient size/shape
When in Atropine usage before PDA correction contraindicated?
tachycardia
What surgical approach is used in PDA correction? How is the ligation performed?
left lateral thoracotomy at the 4th ICS in dogs and 5th ICS in cats
- locate and isolate the vagus nerve as it goes over the PDA (retract it with absorbable suture or umbilical tape)
- isolate and dissect PDA around the pericardial sac
- pass right angle forceps behind the PDA
- double ligate PDA with 2-0 or 0 silk with a surgeons throw
PDA correction:
How is the double ligature around the PDA performed? What commonly happens after?
tie the ligature around the aortic side first, then around the pulmonary side
Branham reflex - reflex bradycardia in response to high blood pressure (detected by baroreceptors)
How can the Branham reflex following PDA ligation be avoided?
- treat with atropine
- tighten first (aortic) ligature slowly
What 3 complications are associated with PDA ligation? Long-term?
- severe hemorrhage secondary to PDA rupture
- bradycardia (Brahman’s reflex) due to increased pressure in the aorta
- residual ductal flow due to incomplete closure
recanalization - reconnection
What 2 additional complications are associated with minimally invasive PDA correction?
- pulmonary embolism (technically doesn’t cause short or long-term complications
- implant infection
What is prognosis of PDA correction like?
- good to excellent in animals < 6 months lacking CHF
- fair if cardiac disease or atrial fibrillation is present
- guarded with recanalization —> must be divided, then ligated
- poor to grave with reverse PDA
What are 5 negative prognostic factors assocaited with PDA surgical treatment?
- age
- body weight (too small)
- lethargy (clinical)
- preoperative treatment with ACE inhibitors
- right atrial dilation
What is the normal embryological development of vascular rings?
- descending aorta = left 4th aortic arch
- right subclavian artery = right 4th aortic arch
- ductus arteriosus = 3rd and 4th
What is the most common vascular ring abnormality?
TYPE I =persistent right aortic arch with persistent left ligamentum arteriosum +/- persistent left anterior vena cava
What are the 3 dog and 2 cat breeds associated with vascular ring abnormalities?
DOGS = GSD, Irish Setter, Labrador Retriever
CATS = Siamese, Persian
What history is associated with vascular ring abnormalities?
post-prandial regurgitation in post-weaning puppies and kittens due to PRAA constricting esophagus
- no murmur - DA not patent!
What clinical findings are common in patients with vascular ring abnormalities? What is not found?
- emaciation
- respiratory signs secondary to aspiration pneumonia
cardiac murmurs —> DA not patent, no blood flow
What 2 laboratory findings are seen in patients with vascular ring anomalies?
- hypoalbuminemia
- elevated WBC - aspiration pneumonia
What 3 radiographic abnormalities are seen in patients with vascular ring anomalies?
- esophageal dilation cranial to heart base
- left/ventral tracheal displacement
- mediastinal widening
(UNSEDATED X-rays)
What is expected on esophagrams in patients with vascular ring anomalies?
dilation cranial to contricting vessel —> Type I and V = cranial to heart base
How are vascular ring anomalies treated? What approach is used?
surgical ligation and division of ligamentum arteriosum
left thoracotomy at the 4th ICS
How is the esophagus prepared for vascular ring anomaly correction?
- place a Foley catheter in esophagus with balloon caudal to the ligamentum arteriosum
- inflate the balloon and pull cranially until the balloon ins lodged against the obstruction
Once the Foley catheter is placed, how is the vascular ring anomaly corrected?
- dissect ligamentum arteriosum away from the esophagus with consideration of the dorsal vagus nerve and the ventral phrenic nerve
- divide ligamentum arteriosum between 2-0 silk ligatures
- dissect remaining fibrous CT from the wall of the esophagus until the balloon of the catheter can pass freely
What post-operative management may be necessary following PRAA correction?
- pneumonia treatment
- elevated feeding of moist solid food (may need for life)
What is used to assess recovery following PRAA correction?
long-term follow up esophagrams —> megaesophagus reversal is rare, but more likely with an early surgery
(>2x normal diameter = reversal unlikely)
In what 2 ways are aberrant subclavian ateries different compared to PRAA?
- regurgitation less common
- obstruction more cranial
(normal left aortic arch with persistent right subclavian artery)
What typically accompanies double aortic arches?
tracheal stenosis and malformation of tracheal rings
Where are ventricular septal defects most commonly seen? Other regions?
membranous septum beneath the septal leaflet of the tricuspid valve on the right side of the aortic annulus on the left
infundibular region, supracristal region, muscular septum
How do ventricular septal defects affect blood flow? How is the heart affected?
blood flows from left ventricle to right ventricle, with volume depending on the size of the defect and pulmonary vascular resistance
left ventricle dilates and hypertrophies as a result of the increased volume
What is the primary repair of VSDs? What else may need to be done?
open heart procedure for Dacron or pericardial patch over defect
palliative pulmonary artery banding (any size)
What is the goal of pulmonary artery banding when correcting VSDs? Why?
increases right ventricular systolic pressure and decreases shunt flow
- protects pulmonary vasculature
- reduces volume overload in the left heart
What approach is used for pulmonary artery banding? What materials are used?
left 4th ICS thoracotomy
- umbilical tape
- Teflon tape
- Silastic sheeting
(tighten until pressure < 30 mmHg or reduction of diameter by 2/3)
What complication is associated with pulmonary artery banding? How can it be avoided?
tearing and hemorrhage (thin-walled)
- careful dissection
- gentle placement of band
- careful measuring of pressure
What effect to the heart is associated with pulmonary artery banding? What should be done if this happens?
fulminant right heart failure due to excessive reduction of outflow —> monitor for cyanosis and hypoxemia
immediately return to surgery and remove band
What is pulmonic stenosis? What are the 4 types?
congenital narrowing of the pulmonic valve, pulmonary artery, or right ventricular outflow tract
- supravalvular
- valvular
- subvalvular
- infundibular
When are patients with pulmonic stenosis treated?
no treatment indicated - not clinical, mild right ventricular hypertrophy, mild gradient
treatment indicated - significant right ventriculat hypertrophy, gradient > 50 mmHg
What noninvasive option is there for pulmonic stenosis? 3 surgical treatments?
balloon valvuloplasty - percutaneous
- valvuloplasty via pulmonic arteriotomy
- patch-graft valvuloplasty
- right ventricle to pulmonary trunk conduit (bypass)
What always results from valvuloplasty procedures?
pulmonic insufficiency due to tearing of stricture —> well tolerated in dogs
(better to have flow!)
What is the main benefit of valvuloplasty via pulmonary arteriotomy in the treatment of pulmonary stenosis? When is it most effective
allows direct visualization of valve
simple valvular stenosis or valve dysplasia with mild infundibular hypertrophy
What are the 2 main indications for patch-graft valvuloplasty in the treatment of pulmonic stenosis?
- severe pulmonaic stenosis - severe infundibular hypertrophy and dynamic stenosis
- supravalvular
What should occur before performing a patch-graft valvuloplasty? What may preclude the use of this technique?
inflow occlusion: umbilical tape tourniquet around vena cavae and azygous vein
aberrant left coronary artery
What are the 2 most common materials used for patch-graft valvuloplasty? What reduces risk?
- Dacron
- patient’s pericardium
partial thickness bites
How are patch-graft valvuloplasties performed?
- partial thickness incision in right ventricle below the pulmonary artery (stenosis)
- graft is sutured to the present opening
- incision is extended up the pulmonary artery
- suture remaining part of the graft to the new incision
When is a right ventricle to pulmonary trunk conduit used to treat pulmonic stenosis? What material is used?
severe stenosis when aberrant left coronary artery precludes use of other techniques
Gore-Tex vascular graft, valve not required
What complications are associated with patch-grafts and conduit techniques?
PATCH-GRAFT = failure to resuscitate heart, fatal hemorrhage
CONDUIT = hemorrhage, air embolism
What materials are used for thoracocentesis?
- IV catheter
- Turkel catheter
- 16-18G needle
- thoracostomy tube
What is the preferred tube diameter, number of holes, and size of holes for tube thoracostomy?
similar to the main bronchus, 1/2-1/3 width of ICS
no more than 3 - addition orifices only adds to flow by 5%
1/4 diameter of tube
What tube sizes are used on different patients?
- dogs and cats 3-6 kg = 14-16 Fr
- dogs 7-15 kg = 18-20 Fr
- dogs 16-30 kg = 22-28 Fr
- dogs > 30 kg = 30-36 kg
Why should a hemostat never be used to clamp off a thoracostomy tube?
serrated and can cut the tube = pnuemothorax
What should be put on thoracostomy tubes in patients less than 15 kg? Over 15 kg?
3-way stopcock
Heimlich valve (one-way)
How can expansional pulmonary edema be avoided?
gradually allow for packed off lungs to refill, or else there can be microtears
How are effusions and air actively drained from the thorax following tube placement?
pleurovac below patient - provides continuous suction (negative pressure) and quantifies air vs. fluids
How can pain be regulated during thoracic surgery?
dorsal and ventral intercostal nerve blocks —> Bupivacaine (lasts longer) or Lidocaine
(no pain = breaths better)
In what 3 situations can a thoracostomy tube be removed?
- when collection of air/fluid is 50 cm^3 or less in 24 hrs
- X-ray at 24 hours doesn’t show air or free fluid
- drainage is reduced to a volume that is consistent with the one produced by the tube itself - 2 mL/kg/day
What is the preferred approach for subtotal pericardectomies? What else can be done?
median sternotomy —> can see both sides of the chest!
lateral thoracotomy at 4th or 5th ICS —> less pericardium able to be removed
How much of the pericardium is removed in subtotal pericardectomies? What is it the common treatment for?
circumferential incision ventral to phrenic nerves
chylothorax —> restrictive pericarditis
How does the prognosis of pericarditis differ due to etiology?
granulomatous = fair
idiopathic = good —> recurrence requires pleuroperitoneal shunts
What is a pleuroperitoneal shunt? What is its purpose?
way to get fluid out of the chest and into the abdomen, where there is more surface area for absorption
palliative: fluid buildup with an obvious cause (MESOTHELIOMA)
What is the most common cardiac neoplasia in dogs? What is the most common cause?
hemangiosarcoma of the right auricle
primary occurrence —> micrometastasis may be present at time of diagnosis
How do patients with hemangiosarcoma of the right auricle present? How is it diagnosed?
acute cardiac tamponade that requires emergency treatment, pericardiocentesis
echocardiography
What treatment of hemangiosarcoma of the right auricle gives the best diagnosis?
excision of the right auricular mass, pericardectomy, and chemotherapy
(MST w/o chemo = 4 months)
What are the 3 purposes of the pericardium?
- prevents over distension
- provides a gliding surface
- protects heart from infection spread from the thoracic cavity
What causes cardiac tamponade? What are 3 signs?
thickening of the pericardium or rapid raise in pericardial pressure
- increased intra-cardiac diastolic pressure
- decreased SV and CO
- increased systemic venous pressure
What are 6 causes of pericardial effusion?
- idiopathic
- right-sided CHF
- pericardioperitoneal diaphragmatic hernia
- infectious/non-infectious pericarditis
- hemorrhage - right auricular mass vs. anticoagulant toxicosis
- neoplasia - mesothelioma, heart base tumor
What is the most common signalment and presentation of patients with pericardial disease? What is seen on physical exam?
older, large breed dogs presenting with weakness, lethargy, collapse, dyspnea, or exercise intolerance
- muffled heart sounds
- weak femoral pulse (pulsus paridoxicus) - weak pulse on inspiration due to decrease in left end systolic pressure
- cardiogenic shock
What diagnostics are used for pericardial disease?
- thoracic imaging: ultrasound fluid check, 3 view thoracic radiograph shows globoid heart
- CBC, chem, UA, coag profile
- ECG: electrical alternans secondary to swinging of the heart in the pericardial sac (QRS amplitude change)
- PERCARDIOCENTESIS: fluid submission for cytology, fluid analysis, and culture
- +/- abdominal imaging
How do pericardectomies help in pericardial disease?
- decreases SA for fluid production
- increases SA for absorption in the pleural cavity
What type of pericardiectomy is preferred? What else is done? How is hemostasis best achieved?
SUBTOTAL - all pericardium ventral to phrenic nerves are removed, resulting in limited tissue dissection
total - median sternotomy, phrenic nerves dissected from pericardium
electrocautery
What are 3 other techniques used to treat pericardial disease?
- thoracoscopic pericardial window
- percutaneous balloon
- pericardiotomy - palliative treatment for tamponade that creates a large pericardial tear
