Marks

1. In performing open aortic arch surgery with hypothermic circulatory arrest, antegrade cerebral perfusion facilitates cerebral protection.

a) Briefly describe TWO cannulation strategies to provide continuous antegrade 2 selective cerebral perfusion.

b) With respect to selective cerebral perfusion, indicate the currently recommended 4 parameters for the following:

Nasopharyngeal temperature

Cerebral perfusion pressure and how it is measured

Cerebral perfusion flow

Model Answer

a) (1 mark each; total 2 marks) 1. Right axillary artery perfusion with clamping of the innominate artery, ± left carotid artery perfusion ± clamping of the subclavian artery. (1 mark) 2. Direct ostial cannulation of the innominate artery and left carotid artery ± clamping of the left subclavian artery with only a brief interruption of flow to insert cannulae after opening the arch. (1 mark)

b) (marks as indicated; total 4 marks) 1. 15°C to 22°C (1 mark) 2. Pressures from 40-70 mm Hg measured in the right radial artery or directly from cannula (2 marks) 3. Flows of 10 mL/kg/min 800-1200 mL/min adjusted to maintain the above pressures (1 mark)

References: Kazui et al, Ann Thoracic Surg. 2002 Nov(5): S1806-9 Ueda et al, Ann Thoracic Surg. 2003 Dec; 76(6): 1951-6 Spielvogel and Griepp, Ann Thoracic Surg. 20015 Jul; 80(1): 90-5

Cardiac Surgery

Marks

2. A 58-year-old man with hypertension is recovering in hospital 12 days following an orthotopic transplantation procedure for ischemic . His postoperative course has been uneventful. His first endomyocardial 1 week after surgery showed no evidence of rejection, and a second biopsy is scheduled for postoperative day 14.

The patient's blood pressure has been running high (160/100 mm Hg) and the transplant team prescribed nifedipine 10 mg PO 4 times daily as a new medication. One hour after the first dose of nifedipine, the nurse calls you to report that the patient has had a presyncopal spell and now has the following vital signs: pulse 120 bpm and regular, blood pressure 70/30 mm Hg, respiratory rate 18/min, temperature 37.9°C.

a) List FOUR possible causes of this acute change in the patient’s clinical status. 2

Further physical examination of the patient reveals reduced breath sounds at both lung 1.5 bases. Cardiac auscultation reveals no murmur, rub or gallop, but heart sounds are less clearly audible than previously. The sternotomy incision is clean and dry, and there is no significant peripheral edema.

b) List the THREE diagnostic tests that should be performed at this time.

Model Answer

a) (0.5 marks each; total 2 marks)

Adverse vasodilatory reaction to the nifedipine

Acute cardiac rejection

Late tamponade/bleeding into the pericardial space

Evolving sepsis

b) (0.5 marks each; total 1.5 marks) Chest x-ray Endomyocardial biopsy ECG

References: Cardiac Surgery in the Adult, 2nd Edition. McGraw-Hill, LH Cohen and LH Edmunds, eds, pp.1400-8

Cardiac Surgery

Marks

3. You have completed a P2 quadrangular resection for myxomatous mitral valve disease. The post-repair intraoperative transesophageal echocardiogram reveals systolic anterior motion (SAM) of the anterior leaflet with a left ventricular outflow tract gradient of 60 mm Hg and moderate mitral regurgitation.

a) List TWO anatomical factors that preoperatively predict the possibility of SAM post 1 repair.

b) List TWO components in the pathophysiology of SAM. 1

c) After separation from cardiopulmonary bypass, list FOUR non-surgical therapeutic 2 strategies to decrease SAM.

d) Name the surgical technique that is the MOST commonly used to avoid SAM. 0.5

e) List FOUR alternative surgical techniques to correct SAM. 2

Cardiac Surgery

Model Answer a) (0.5 marks each; total 1 mark): - Excess leaflet tissue, anterior or posterior leaflet - Narrow aortic/mitral angle - Short C-sept distance b) (0.5 marks each; total 1 mark). - Dynamic anterior leaflet tethering in left ventricular outflow tract (LVOT) - Excessive posterior leaflet height - Forward displacement of the coaptation line towards the anterior annulus c) (0.5 marks each; total 2 marks). - eliminate beta-stimulants/positive inotropes - consider beta-blockers - volume loading - increase afterload - reduce vasodilator - atrial pacing d) (0.5 marks) - Reducing the height of the posterior leaflet with a sliding leaflet annuloplasty. e) (0.5 marks each; total 2 marks). - upsize annuloplasty ring - excise excessive tissue of anterior leaflet - edge-to-edge repair - transfer secondary chords of posterior leaflet to anterior leaflet to tether it -

References: 1. Lee et al. Circulation 1994. Aug. 90(2): 1107-08 2. Maslow et al. J AM Coll Cardiol 1999. Dec 34(7): 2096-2104 3. Jebara et al. Circulation 1993. Nov 88(5 PT 2): 1130-4 4. Quigley et al. J Dis. 2004. Nov 13(6): 927-30 5. Mascagni et al. Ann Thoracic Surg 2005. Feb 79(2): 471-3. Discussion 474. 6. Sternik et al. Tex Heart Inst J 2005. 32(1): 47-9

Cardiac Surgery

Marks

4. When performing an arterial switch operation in a neonate, you notice a 3 decrease of more than 20% in the cerebral near-infrared spectroscopy (NIRS) value relative to the pre-incision baseline value.

List SIX possible interventions during cardiopulmonary bypass to correct this condition.

Model Answer (0.5 marks each; total 3 marks)

1. Increase bypass flow 2. Increase PaCO2 3. Increase mean arterial pressure 4. Decrease temperature 5. Increase hematocrit 6. Adjust cannulae 7. Increase sedation

Cardiac Surgery

Marks

5. A 67-year-old man presents with atypical chest pain and a slight rise in troponin level. Coronary angiography demonstrates a 50% stenosis of the mid-right coronary artery. Fractional flow reserve (FFR) assessment of this lesion is performed.

a) Define the term “fractional flow reserve (FFR)”. 1

b) How and under what essential condition is FFR determined? 3

c) How is this essential condition achieved? 2

d) What numerical value of FFR signifies a hemodynamically significant stenosis 1 that is almost always capable of inducing myocardial ischemia?

Model Answer a) (1 mark) The extent to which maximal myocardial blood flow is limited by a stenotic epicardial coronary lesion.

b) (3 marks) Coronary catheters measure the pressure proximal (Pp) and distal (Pd) to a stenotic lesion under conditions of maximal hyperemia. FFR=Pd/Pp

c) (2 marks) Dilatation of epicardial conductance vessels with nitroglycerin and of the microvascular resistance vessels with adenosine.

d) (1 mark) FFR ≤ 0.75

Reference: De Bruyne B and J Sarma. FFR: a review: Invasive imaging. Heart 2008;94:949-59.

Cardiac Surgery