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Small Animal Surgery > Cardiovascular Surgery > Flashcards

Cardiovascular Surgery Flashcards

1
Q

What are the 3 most common congenital cardiac disorders in dogs and cats? Dogs specifically?

A
  1. patent ductus arteriosus
  2. vascular ring anomalies
  3. VSD

aortic and pulmonary stenosis

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2
Q

What is patent ductus arteriosus? What does this cause?

A

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

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3
Q

What is the purpose of the ductus arteriosus in the fetus?

A

shunts blood from the pulmonary artery to the aorta, directing venous blood away from the fetal lungs

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4
Q

What is Eisenmenger’s syndrome? What causes it? What does it result in?

A

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

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5
Q

What is the most common signalment associated with PDA? In what breeds has a heritable basis been identified?

A

female pure bred small breeds - Bichon Frise, Chihuahua, Poodle, Pomeranian, Yorkie

Poodles and Welsh Corgis

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6
Q

What clinical signs are seen in patients with PDA?

A

younger dogs with:

  • cough (pulmonary edema)
  • shortness of breath
  • left-sided heart failure
  • machine murmur
    (can be asymptomatic)
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7
Q

What clinical signs are seen in patients with reverse PDA?

A

older dogs with:

  • exercise intolerance
  • pelvic limb collapse
  • cyanosis
  • polycythemia: increased PCV for compensation
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8
Q

What are the 2 most commonly heard on auscultation in patients with PDA? What other cardiac signs are associated?

A
  1. continuous machinery murmur heard best at the high left heart base or left axillary region
  2. palpable cardiac thrill
  • strong femoral pulse
  • tall R waves or wide P waves
  • stunted growth
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9
Q

What 3 thoracic radiograph findings are consistent with PDA?

A
  1. left atrial and ventricular enlargement
  2. dilation of descending aorta
  3. dilation of pulmonary artery
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10
Q

How is an echocardiogram used to diagnose PDA?

A

confirmation

  • left atrial enlargement
  • left ventricle dilation
  • pulmonary artery dilation
  • “micro bubble”
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11
Q

What is seen on CBC/chem in patients with PDA?

A

polycythemia - increased RBC to compensate for hypoxemia

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12
Q

When is surgical management indicated in patients with PDA? What 2 medical treatments are recommended prior to surgery?

A

all dogs with L to R shunting

  1. Furosemide - pulmonary edema, CHF
  2. beta adrenergic blocker or calcium channel blocker - atrial fibrillation
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13
Q

When is PDA surgery contraindicated?

A

R to L shunting

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14
Q

What 2 surgical treatments are used for PDA?

A
  1. minimally invasive coil embolization or Amplatzer ductal occluder* - more complete occlusion, less complications, limited by patient size
  2. surgical ligation - less expensive, no limitations for patient size/shape
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15
Q

When in Atropine usage before PDA correction contraindicated?

A

tachycardia

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16
Q

What surgical approach is used in PDA correction? How is the ligation performed?

A

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
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17
Q

PDA correction:

A
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18
Q

How is the double ligature around the PDA performed? What commonly happens after?

A

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)

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19
Q

How can the Branham reflex following PDA ligation be avoided?

A
  • treat with atropine
  • tighten first (aortic) ligature slowly
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20
Q

What 3 complications are associated with PDA ligation? Long-term?

A
  1. severe hemorrhage secondary to PDA rupture
  2. bradycardia (Brahman’s reflex) due to increased pressure in the aorta
  3. residual ductal flow due to incomplete closure

recanalization - reconnection

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21
Q

What 2 additional complications are associated with minimally invasive PDA correction?

A
  1. pulmonary embolism (technically doesn’t cause short or long-term complications
  2. implant infection
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22
Q

What is prognosis of PDA correction like?

A
  • 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
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23
Q

What are 5 negative prognostic factors assocaited with PDA surgical treatment?

A
  1. age
  2. body weight (too small)
  3. lethargy (clinical)
  4. preoperative treatment with ACE inhibitors
  5. right atrial dilation
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24
Q

What is the normal embryological development of vascular rings?

A
  • descending aorta = left 4th aortic arch
  • right subclavian artery = right 4th aortic arch
  • ductus arteriosus = 3rd and 4th
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25
Q

What is the most common vascular ring abnormality?

A

TYPE I =persistent right aortic arch with persistent left ligamentum arteriosum +/- persistent left anterior vena cava

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26
Q

What are the 3 dog and 2 cat breeds associated with vascular ring abnormalities?

A

DOGS = GSD, Irish Setter, Labrador Retriever

CATS = Siamese, Persian

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27
Q

What history is associated with vascular ring abnormalities?

A

post-prandial regurgitation in post-weaning puppies and kittens due to PRAA constricting esophagus

  • no murmur - DA not patent!
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28
Q

What clinical findings are common in patients with vascular ring abnormalities? What is not found?

A
  • emaciation
  • respiratory signs secondary to aspiration pneumonia

cardiac murmurs —> DA not patent, no blood flow

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29
Q

What 2 laboratory findings are seen in patients with vascular ring anomalies?

A
  1. hypoalbuminemia
  2. elevated WBC - aspiration pneumonia
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30
Q

What 3 radiographic abnormalities are seen in patients with vascular ring anomalies?

A
  1. esophageal dilation cranial to heart base
  2. left/ventral tracheal displacement
  3. mediastinal widening

(UNSEDATED X-rays)

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31
Q

What is expected on esophagrams in patients with vascular ring anomalies?

A

dilation cranial to contricting vessel —> Type I and V = cranial to heart base

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32
Q

How are vascular ring anomalies treated? What approach is used?

A

surgical ligation and division of ligamentum arteriosum

left thoracotomy at the 4th ICS

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33
Q

How is the esophagus prepared for vascular ring anomaly correction?

A
  • 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
34
Q

Once the Foley catheter is placed, how is the vascular ring anomaly corrected?

A
  • 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
35
Q

What post-operative management may be necessary following PRAA correction?

A
  • pneumonia treatment
  • elevated feeding of moist solid food (may need for life)
36
Q

What is used to assess recovery following PRAA correction?

A

long-term follow up esophagrams —> megaesophagus reversal is rare, but more likely with an early surgery

(>2x normal diameter = reversal unlikely)

37
Q

In what 2 ways are aberrant subclavian ateries different compared to PRAA?

A
  1. regurgitation less common
  2. obstruction more cranial

(normal left aortic arch with persistent right subclavian artery)

38
Q

What typically accompanies double aortic arches?

A

tracheal stenosis and malformation of tracheal rings

39
Q

Where are ventricular septal defects most commonly seen? Other regions?

A

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

40
Q

How do ventricular septal defects affect blood flow? How is the heart affected?

A

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

41
Q

What is the primary repair of VSDs? What else may need to be done?

A

open heart procedure for Dacron or pericardial patch over defect

palliative pulmonary artery banding (any size)

42
Q

What is the goal of pulmonary artery banding when correcting VSDs? Why?

A

increases right ventricular systolic pressure and decreases shunt flow

  • protects pulmonary vasculature
  • reduces volume overload in the left heart
43
Q

What approach is used for pulmonary artery banding? What materials are used?

A

left 4th ICS thoracotomy

  • umbilical tape
  • Teflon tape
  • Silastic sheeting
    (tighten until pressure < 30 mmHg or reduction of diameter by 2/3)
44
Q

What complication is associated with pulmonary artery banding? How can it be avoided?

A

tearing and hemorrhage (thin-walled)

  • careful dissection
  • gentle placement of band
  • careful measuring of pressure
45
Q

What effect to the heart is associated with pulmonary artery banding? What should be done if this happens?

A

fulminant right heart failure due to excessive reduction of outflow —> monitor for cyanosis and hypoxemia

immediately return to surgery and remove band

46
Q

What is pulmonic stenosis? What are the 4 types?

A

congenital narrowing of the pulmonic valve, pulmonary artery, or right ventricular outflow tract

  1. supravalvular
  2. valvular
  3. subvalvular
  4. infundibular
47
Q

When are patients with pulmonic stenosis treated?

A

no treatment indicated - not clinical, mild right ventricular hypertrophy, mild gradient

treatment indicated - significant right ventriculat hypertrophy, gradient > 50 mmHg

48
Q

What noninvasive option is there for pulmonic stenosis? 3 surgical treatments?

A

balloon valvuloplasty - percutaneous

  1. valvuloplasty via pulmonic arteriotomy
  2. patch-graft valvuloplasty
  3. right ventricle to pulmonary trunk conduit (bypass)
49
Q

What always results from valvuloplasty procedures?

A

pulmonic insufficiency due to tearing of stricture —> well tolerated in dogs

(better to have flow!)

50
Q

What is the main benefit of valvuloplasty via pulmonary arteriotomy in the treatment of pulmonary stenosis? When is it most effective

A

allows direct visualization of valve

simple valvular stenosis or valve dysplasia with mild infundibular hypertrophy

51
Q

What are the 2 main indications for patch-graft valvuloplasty in the treatment of pulmonic stenosis?

A
  1. severe pulmonaic stenosis - severe infundibular hypertrophy and dynamic stenosis
  2. supravalvular
52
Q

What should occur before performing a patch-graft valvuloplasty? What may preclude the use of this technique?

A

inflow occlusion: umbilical tape tourniquet around vena cavae and azygous vein

aberrant left coronary artery

53
Q

What are the 2 most common materials used for patch-graft valvuloplasty? What reduces risk?

A
  1. Dacron
  2. patient’s pericardium

partial thickness bites

54
Q

How are patch-graft valvuloplasties performed?

A
  • 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
55
Q

When is a right ventricle to pulmonary trunk conduit used to treat pulmonic stenosis? What material is used?

A

severe stenosis when aberrant left coronary artery precludes use of other techniques

Gore-Tex vascular graft, valve not required

56
Q

What complications are associated with patch-grafts and conduit techniques?

A

PATCH-GRAFT = failure to resuscitate heart, fatal hemorrhage

CONDUIT = hemorrhage, air embolism

57
Q

What materials are used for thoracocentesis?

A
  • IV catheter
  • Turkel catheter
  • 16-18G needle
  • thoracostomy tube
58
Q

What is the preferred tube diameter, number of holes, and size of holes for tube thoracostomy?

A

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

59
Q

What tube sizes are used on different patients?

A
  • 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
60
Q

Why should a hemostat never be used to clamp off a thoracostomy tube?

A

serrated and can cut the tube = pnuemothorax

61
Q

What should be put on thoracostomy tubes in patients less than 15 kg? Over 15 kg?

A

3-way stopcock

Heimlich valve (one-way)

62
Q

How can expansional pulmonary edema be avoided?

A

gradually allow for packed off lungs to refill, or else there can be microtears

63
Q

How are effusions and air actively drained from the thorax following tube placement?

A

pleurovac below patient - provides continuous suction (negative pressure) and quantifies air vs. fluids

64
Q

How can pain be regulated during thoracic surgery?

A

dorsal and ventral intercostal nerve blocks —> Bupivacaine (lasts longer) or Lidocaine

(no pain = breaths better)

65
Q

In what 3 situations can a thoracostomy tube be removed?

A
  1. when collection of air/fluid is 50 cm^3 or less in 24 hrs
  2. X-ray at 24 hours doesn’t show air or free fluid
  3. drainage is reduced to a volume that is consistent with the one produced by the tube itself - 2 mL/kg/day
66
Q

What is the preferred approach for subtotal pericardectomies? What else can be done?

A

median sternotomy —> can see both sides of the chest!

lateral thoracotomy at 4th or 5th ICS —> less pericardium able to be removed

67
Q

How much of the pericardium is removed in subtotal pericardectomies? What is it the common treatment for?

A

circumferential incision ventral to phrenic nerves

chylothorax —> restrictive pericarditis

68
Q

How does the prognosis of pericarditis differ due to etiology?

A

granulomatous = fair

idiopathic = good —> recurrence requires pleuroperitoneal shunts

69
Q

What is a pleuroperitoneal shunt? What is its purpose?

A

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)

70
Q

What is the most common cardiac neoplasia in dogs? What is the most common cause?

A

hemangiosarcoma of the right auricle

primary occurrence —> micrometastasis may be present at time of diagnosis

71
Q

How do patients with hemangiosarcoma of the right auricle present? How is it diagnosed?

A

acute cardiac tamponade that requires emergency treatment, pericardiocentesis

echocardiography

72
Q

What treatment of hemangiosarcoma of the right auricle gives the best diagnosis?

A

excision of the right auricular mass, pericardectomy, and chemotherapy

(MST w/o chemo = 4 months)

73
Q

What are the 3 purposes of the pericardium?

A
  1. prevents over distension
  2. provides a gliding surface
  3. protects heart from infection spread from the thoracic cavity
74
Q

What causes cardiac tamponade? What are 3 signs?

A

thickening of the pericardium or rapid raise in pericardial pressure

  1. increased intra-cardiac diastolic pressure
  2. decreased SV and CO
  3. increased systemic venous pressure
75
Q

What are 6 causes of pericardial effusion?

A
  1. idiopathic
  2. right-sided CHF
  3. pericardioperitoneal diaphragmatic hernia
  4. infectious/non-infectious pericarditis
  5. hemorrhage - right auricular mass vs. anticoagulant toxicosis
  6. neoplasia - mesothelioma, heart base tumor
76
Q

What is the most common signalment and presentation of patients with pericardial disease? What is seen on physical exam?

A

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
77
Q

What diagnostics are used for pericardial disease?

A
  • 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
78
Q

How do pericardectomies help in pericardial disease?

A
  • decreases SA for fluid production
  • increases SA for absorption in the pleural cavity
79
Q

What type of pericardiectomy is preferred? What else is done? How is hemostasis best achieved?

A

SUBTOTAL - all pericardium ventral to phrenic nerves are removed, resulting in limited tissue dissection

total - median sternotomy, phrenic nerves dissected from pericardium

electrocautery

80
Q

What are 3 other techniques used to treat pericardial disease?

A
  1. thoracoscopic pericardial window
  2. percutaneous balloon
  3. pericardiotomy - palliative treatment for tamponade that creates a large pericardial tear

Small Animal Surgery (34 decks)

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