Ch 106 - Cardiac Surgery Flashcards
Which coronary artery is dominant in dogs and cats?
- Dogs - left
- Cats - right
What is the first brach of the aortic arch?
Second?
- Brachiocephalic trunk
- Second = Left subclavian artery
What factors determine stroke volume?
- Preload
- Afterload
- Contractility
What kinds of cardiac procedures can be performed under venous inflow occlusion?
Short procedures under 4 minutes
For what amount of time can circulatory arrest be allowed for in normotheric and hypothermic animals (32-34C)?
- Normothermic - 2min
- Hypothermic - 4min
What is the lowest allowable temperature for hypothermic cardiac surgery?
32C - under this the risk of v-fib increases significantly
What vessels are tourniqueted for inflow occlusion?
- Caudal vena cava
- Cranial vena cava
- Azygous vein
What is the maximal time for aortic cross clamping during cardiac bypass?
90min
What is the main post-op complications of cardiac bypass?
SIRS
What breeds are predisposed to PDA?
- Poodles, Keeshonds, Maltese, Bichon, Torkies, COcokers etc
- Heritable component in Corgis and Poodles (hypoplasia and segmental asymmetry of the ductus muscle mass that results in failure of ductus contraction
What causes a reverse PDA?
Supresystemic pulmonary hypertension
What age is recommended for surgical treatment of a PDA?
- Older than 8 weeks and younger than 16 weeks
What is the reported residual flow thorugh a PDA after standard ligation and the Jackson-Henderson technique?
- Standard - 21%
- Jackson-Henderson 53%
What nerve course over a PDA?
Left vagus
What suture is recommended for PDA ligation?
2 silk sutures 2-0
What is the Branham reflex?
Increase in blood pressure and decrease in HR after ligation of a PDA
What is the mortality rate of PDA ligation?
0-7%
List indications for surgery with pulmonic stenosis
What are the surgical options?
Indications for surgery:
- Tricuspid regurgitation
- Severe stenosis
- Systolic pressure gradient across defect of 60mmHg or more
- Clinical signs
Sx options:
- Dilatation valvuloplasty
- Pulmonic valvulotomy or valvulectomy
- Patch-graft valvuloplasty
When is balloon valvuloplasty for pulmonic stenosis contraindicated?
- When there is a anomalous left coronary artery (common in Eng Bulldogs and Boxers)
What is the recommended approach for a patch graft valvuloplasty using inflow occlusion and cardiac bypass?
- Inflow occlusion - left 5th intercostal
- Bypass - median sternotomy
What breeds are predisposed to aortic stenosis?
What is the classical murmur?
- Newfies, Goldens, Boxers, Rottweilers, Bouviers
- Crescendo-decrescendo left systolic murmur at the heart base
What are the treatment options for aortic stenosis?
What factor effects survival?
Options:
- Surgical valvuloplasty
- Transcatheter balloon valvuloplasty
- Beta-blockers
- Tx does not effect survival….
Severity of pressure gradient effects survival
What are the surgical options for a ventricular septal wall defect?
- Pulmonary artery banding
- Open repair
- Intravascular or hybrid intervention (Amplatz Ductal Occluder)
List the components of Tetralogy of Fallot
- Pulmonic stenosis
- Ventricular septal defect
- Overriding aorta
- Right ventricular hypertrophy
The most common cyanotic heart defect in companion animals
What breeds are overrepresented for Tetralogy of Fallot?
- Keeshonds
- Poodles
- Schnauzers
- Terriers
- Collies
- Shelties
What is the most prominent feature of tetralogy of fallot?
Moderate to severe cyanosis, unresponsive to supplemental oxygen
What are the surgical indicators for tetralolgy of fallot?
- Debilitating exercise intolerance
- Polycythaemia (HCT over 70%)
- Resting hypoxaemia (arterial saturation less than 60%)
What are the surgical options for tetralogy of fallot?
Systemic-to-pulmonic shunts to increase pulmonary blood flow
- Blalock-Taussig (Subclavian to pulmonary artery)
- Potts (Aorticopulmonary anastomosis)
- Waterston (aorta-to-right pulmonary artery)
- Glenn (Venocaval-to-pulmonary artery anastomosis)
Open repair: curative intent
- Patch closure of VSD
- Oval patch graft valvuloplasty for pulmonary stenosis
What is cor triatriatum?
What are the two main types?
An uncommon congenital defects resulting in the persistance of an embryonic membrane
- Cor triatriatum dexter - on the right. Chow chows overrepresented
- Cor triatriatum sinister - on the left, reported in cats
Causes obstruction of the venous flow through the atrium.
Membranectomy considered curative
What is a relative contraindication for mitral valve surgery?
Severe chronic inflammatory airway disease with or without collapsing trachea
List the surgical options for mitral regurgitation
- Mitral valve replacement through 5th right or left thoracotomy
- Mitral valve repair
What breeds are predisposed to cardiac HSA?
What percentage will have concurrent HSA of the spleen?
Mets to other areas?
- GSD, Goldens and Labs
- 29% HSA in spleen
- 42% mets in other areas
With primary splenic HSA, 8.7% will have a cardiac mass
What is the prognosis for cardiac HSA?
- Surgical excision - 4m
- Longer with adjuvant chemo
- Pericardiectomy alone does not improve survival
Why are brachycephalic dogs thought to be predisposed to chemodectomas?
Chronic stimulation of the chemoreceptors by hypoxia
What is the prognosis for chemodectoma?
- Pericardiectomy 730d (vs 42d without)
What are indications for a pacemaker?
- High-grade 2nd or 3rd degree AV blocks
- Sick sinus syndrome
- Sinus arrest
- Chronic bradyarrhythmias
What are the 2 methods of pacemaker insertion?
- Transveonous (preferred)
- Epicardial (may be necessary in small dogs and cats)
Describe the 5 letts NASPE/BPEG coding of pacemakers
What is the most common pacing mode of vet patients?
Letters indicate the chamber paced, the chamber sensed, the response to sensing, whether the rate can be modulated, and wheter the system provided multisite pacing
Chambers paced, chambers sensed and multisite pacing are identified using:
- A - atrium
- V - ventricle
- D - dual
- O - none
Response to sensing:
- T - triggered
- I - inhibited
- D - dual
- O - none
Rate of modulation:
- R - present
- O - absent
Most common is single-chamber ventricular inhibited synchronous pacing with (VVIR) or without (VVI) rate modulation
What is the recommended approach for an epicardial pacemaker?
5th or 6th left lateral thoracotomy
Regarding pacemakers, what may be the cause of an increase in impedence of large variations in impedence and failure to pace?
- Increase: development of excessive inflammatory tissue around the lead tip
- Variation: Lead instability
- Failure to pace: lead breakage, disconnection or dislodgement
What are the surgial options for a ventricular septal wall defect?
- Pulmonary artery banding
- Open repair
- Intravascular or hybrid intervention (Amplatz Ductal Occluder)
