SAS

Question 1

Pyle and al article

Answer 1

Genetics and pathology of discrete subaortic stenosis in the Newfoundland dog (Pyle et al. AHJ 1976)
* 139 dogs from 22 test matings studied
o 42 (30.2%) had one of below forms of SAS

• Lesions classified according to severity as grade 1 to 3
  o Gross lesions only found in dogs > 3weeks of age → suggest postnatal development.
  o Grade 1 (mild SAS): early form of dz that progresses with age
   Grade 1 SAS never found in dogs >12weeks
   Grade 3 predominantly found in dogs >6mo
  o Subaortic ring: persistence of embryonal endocardial tissue in LVOT
   Capable of proliferation/chondrogenic differentiation after birth

Question 2

Pyle and al. Grade 1 gross path lesions

Answer 2

o Small, white, slightly raised nodules on endocardial surface of IVS below AoV
o Similar nodules on ventricular surface of AoV in some animals

Question 3

Pyle and al. Grade 1 histopath lesions

Answer 3

o Fibroplastic cell
o Surrounded by connective tissue fibers + alcian blue positive ground substance
o Lymphatic/dilated capillaries (endothelium lined space/channels) present at base of nodules

Question 4

Pyle and al. Grade 1 PE

Answer 4

asymptomatic
o Some have transient, soft, early systolic murmurs (grade I/VI)

Question 5

Pyle and al. Grade 1 Cardiac KT

Answer 5

no systolic PG across LVOT
o Normal angio

Question 6

Pyle and al. Grade 2 gross path lesions

Answer 6

o Narrow ridge of white/thickened endocardium extending partially around LVOT
o Variable location: most cases at base of MV anterior leaflet
 Extend transversely across IVS below LCA cusp of AoV

Question 7

Pyle and al. Grade 2 histopath lesions

Answer 7

o Ridges: fibroplastic cells surrounded by dense collagenous tissue
o Connective tissue fibers denser vs grade 1

Question 8

Pyle and al. Grade 2 PE

Answer 8

asymptomatic
o Short and soft systolic murmurs (grade I or II/VI)

Question 9

Pyle and al. Grade 2 Cardiac KT

Answer 9

most had no systolic PG across LVOT
o If present was <20mmhg

Question 10

Pyle and al. Grade 3 gross path lesions

Answer 10

• Most severe form
• Gross pathology
  o Fibrous band/ridge/collar encircled LVOT below AoV
  o Often raised of 1-2mm above endocardial surface
  o Extended across below AoV cusp and anterior MV leaflet
  o Thickened ventricular surface of AoV leaflets
  o Focal areas of LV myocardial necrosis and fibrosis

Question 11

Pyle and al. Grade 3 histopath lesions

Answer 11

o Ring: loose collagenous fibrous connective tissue w sparse elongated mesenchymal cells
 Mesenchymal cells → chondrogenic differentiation
* Round polygonal cells w metachromatic capsule
 Rich in acid mycopolysaccharides (alcian blue stain)
o Myocardial lesions:
 Thickening of intramyocardial arteries from fibromuscular proliferation
 ↑ connective tissue and ground substance media

Question 12

Pyle and al. Grade 3 PE

Answer 12

o Grade III-IV/VI systolic basilar murmurs + carotid radiation at thoracic inlet
o ECG: VPC, Afib, ↑QRS amplitude
o CTX: post stenotic dilation of Ao

Question 13

Pyle and al. Grade 3 Cardiac KT

Answer 13

o Systolic PG across LVOT from 36-95mmHg
o Angio: narrowing of LVOT
 Discrete subvalvular ring
 Post stenotic dilation of ascending Ao
 LVH

Question 14

Hu: theories to explain fibrous SAS

Answer 14

• Failure of resorption of bulbus cordis
• Repeated infections → inflammatory proliferation of endocardium in LVOT
• Fibrous plaques observed on IVS with HCM and trauma from anterior MV leaflet (SAM)
  o Lack of LVH in mild forms
• Malformation of proximal extremity of truncus septum joining conus septum
• Malformation of AV endocardial cushions surrounding subaortic LVOT

Question 15

Coronary arteries histo lesions

Answer 15

• Extensive intramural pathology
  o Intimal proliferation of connective tissue and smooth muscle → luminal narrowing
  o Medial degeneration and hypertrophy
  o Arteriosclerotic lesions of intramural coronaries
• ↓ myocardial capillary density secondary to LVH

Question 16

Coronary lesions associated w/

Answer 16

• Coronary lesions: associated w areas of myocardial ischemia and fibrosis
  o Most prevalent in papillary muscles and subendocardium of LV wall

Question 17

Coronary flow

Answer 17

• Abnormal coronary flow
  o ↓ baseline diastolic flow
  o Reversal of flow during early systole
  o Delayed forward systolic flow
• Prominent LCA from ↑ O2 myocardial demand

Question 18

Consequences of abn coronary blood flow

Answer 18

Myocardial ischemia
Arrhythmias
incr wall tension
CHF

Question 19

Myocardial ischemia happens from

Answer 19

o Narrow/ abnormal coronary vessels
o ↑ myocardial mass
o LV systolic hypertension

Question 20

Why do arrhythmias develop

Answer 20

o Myocardial ischemia predisposes to arrhythmia development
o Abnormal coronary flow suggested as the cause for
 Exercise related ST segment deviation
 VPCs

Question 21

How abn coronary blood flow contribute to CHF

Answer 21

myocardial failure, ↑ ventricular stiffness, MR, Afib
o Exertional syncope, sudden death reported
 Myocardial ischemia
 Ventricular arrhythmias
 Exercise induced ↑LVP → activation of LV mechanoR → bradycardia + vasodilation