Cardiac Surgery-Ishay

Question 1

Class I AHA guidelines for CABG

Answer 1

Left main stenosis, Left main equivalent (prox LAD and prox circumflex), Triple-vessel disease, Disabling angina refractory to medical therapy, Failed PCI (ongoing ischemia with significant territory at risk, hemodynamic irritability)

Question 2

Definition of significant stenosis

Answer 2

A 75% reduction in cross-sectional area, which correlates with a 50% loss of arterial diameter, is sufficient to impair coronary blood flow reserve.

Question 3

What would happen in a lesion that is less than 50% stenosed after CABG?

Answer 3

Bypassing less-than-significantly stenotic lesions creates a state of competitive flow between the graft and the native vessel, predisposing to low flow in the bypass conduit and increasing the risk of graft occlusion regardless of the conduit used.

Question 4

Definition of traditional revascularization

Answer 4

All diseased arterial systems receiving at least one graft insertion.

Question 5

Definition of functional revascularization

Answer 5

Bypassing all diseased “primary” coronary segments (LAD,LCX,RCA).

Question 6

What is the limit of a nondiseased vessel?

Answer 6

Any vessel of

Question 7

CABG vs. PCI theory

Answer 7

CABG is complete vascularization with culprit lesion and future culprit lesions, PCI is with “suitable” culprit lesion

Question 8

CABG vs PCI outcome

Answer 8

Fewer adverse events (all cause death) in CABG. PCI is only lower for stroke.

Question 9

What is the total 30 day risk for CABG operative mortality?

Answer 9

3.05%

Question 10

Risk of permanent stroke in CABG

Answer 10

1.63%

Question 11

Risk of deep sternal wound in CABG

Question 12

What additional risk factors add to CABG for mediastinits?

Answer 12

Obesity, COPD

Question 13

What are the top 3 adverse outcomes of COPD?

Answer 13

Mortality, permanent stroke, renal failure requiring dialysis. Higher in emergency surgery.

Question 14

What are the considerations in the EuroSCORE prediction of operative risk

Answer 14

Considers all patient factors (age, sex, COPD), cardiac factors (angina, LVEF), Operative factors (emergency, other surgeries, etc.) Must be calculated before each surgery.

Question 15

What are the steps of myocardial revascularization with Coronary bypass

Answer 15

1. Sternotomy (preferable but in complicated patients thorectomy) 2. Bypass conduits harvested 3. Cardiopulmonary bypass (On Heparin, Cannulation, Initiating bypass-On Pump, Weaning from CPB-Off Pump) 4. Chest closure.

Question 16

What vessels can be used for bypass conduits?

Answer 16

Internal Thoracic Artery Radial artery Greater Saphenous Vein Gastroepiploic artery

Question 17

What are the components of the Internal Thoracic Artery (ITA) used for graft?

Answer 17

LIMA (left internal mammary artery) or RIMA

Question 18

What are the benefits to using the internal thoracic artery?

Answer 18

Superior early and late survival, and better event-free survival - The conduit of first choice. Resistance to atherosclerosis. Production of vasodilators NO and prostacyclin - “downstream” effect. Response to : vasodilators (milrinone + nitroglycerin) Remodeling - adapting to demand. Only attach distal side. Usually stay patent for up to 20 years.

Question 19

How do outcomes compare in SVG vs LIMA in LAD bypass?

Answer 19

X 1.61 risk of death in 10 y X 1.41 risk of late MI X 2.00 risk of re-operation.

Question 20

What is a skeletoned artery vs pedicled?

Answer 20

Much mroe difficult, need to find all the branches and clean each one otherwise can be damaged but perfusion is better and pt has less pain. Also increases length of vessel. Pedicled is with the artery and surrounding tissue.

Question 21

What is the requirement for using the radial artery?

Answer 21

Proper ulnar perfusion using Allen test. Also susceptible to collateral flow so arteries need to be at least 75% stenosed. Need to attach proximal anastemoses.

Question 22

What is the composite (T- or Y-) graft made of?

Answer 22

Components of the RIMA and LIMA.

Question 23

What is the hierarchy of patency of arteries for graft?

Answer 23

LIMA is best (20y), RIMA, Radial, Gastroepiploic, SVG

Question 24

What is the 5 year patency of the radial artery?

Answer 24

83-95%

Question 25

What are factors that add to graft failure rate?

Answer 25

1. The target vessel stenosis is less than severe 2. On the right coronary system.

Question 26

What is the average duration of patency for a saphenous vein graft?

Answer 26

10years

Question 27

What are the increased risks for impaired wound healing in SVG?

Answer 27

Ischemic heart disease, diabetes

Question 28

What are the benefits of endoscopic?

Answer 28

Patients like it better but open surgery lasts longer.

Question 29

How is heparin applied for CABG?

Answer 29

Full heparinization – ACT \>480 seconds – to minimize thrombin formation within the extracorporeal circuit.. Rechecked every 15-20 min. Prevents pulmonary embolism.

Question 30

What are the 3 cannulations that must be done during surgery?

Answer 30

Arterial cannulation : ascending Aorta. Venous drainage : 2-stage cannula , right atrial appendage. Cardioplegia : antegrade, retrograde.

Question 31

What is cardioplegia?

Answer 31

Blood taken from venous system, cools, adds oxygen (to preserve tissue) and potassium (to stop contractility) added and introduced into the aortic root (antegrade) or carotid sinus (retrograde). Pumped every 15-20min.

Question 32

What does the cross-clamp do in CABG?

Answer 32

Clamps the aorta to prevent cardioplegia blood from reaching systemic circulation. Pressure makes cardioplegia blood enter carotid arteries.

Question 33

What do the venous and arterial cannulae do in CABG?

Answer 33

Takes deoxygenated blood from venous system, oxygenates, goes into arterial tube and into aorta above the crossclamp.

Question 34

What are the effects of cardioplegia?

Answer 34

Hypothermia lowers metabolism (reduced by 90%), diastolic arrest, potassium stops contractility of the heart, oxygen prevents ischemia.

Question 35

How does retrograde cardioplegia work?

Answer 35

Through the coronary sinus with no valves can pass to coronary arteries. Usually combined with antegrade to sandwich the occlusion.

Question 36

What needs to be done during chest wall closure of CABG?

Answer 36

Rewarm patient back to 37oC. Epicardial pacemaker wires (because cardioplegia may inhibit SA node for a few hours), Weaning from Cardiopulmonary Bypass, give Protamine (counteract the effect of heparin)

Question 37

What is a special consideration for SVG?

Answer 37

Must turn upside down to account for valves.

Question 38

What is the difference in off-pump CABG?

Answer 38

Revascularization without the potential complications of extracorporeal support.. Completeness of Revascularization and Graft Patency . Technically demanding, can't see arteries well and difficult to stitch. Posterior stitching not allowed because of hemodynamic instability. Used when patient has significant comorbidity or if aorta is calcified and atheromatous.

Question 39

What is a Maze procedure used for?

Answer 39

Atrial fibrillation, abnormal electrical pathways.

Question 40

What is Maze?

Answer 40

Ablation of pathway of extra atrial foci by cutting incisions into atria. Controlled maze-like pathway into AV node.

Question 41

What is the outcome of Maze procedures?

Answer 41

77% have sinus rhythm.

Question 42

What is surgical ventricular reconstruction?

Answer 42

Cut aneurysm of LV and heart contracts better without it.