Cardiac Surgery-Ishay Flashcards
Class I AHA guidelines for CABG
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)
Definition of significant stenosis
A 75% reduction in cross-sectional area, which correlates with a 50% loss of arterial diameter, is sufficient to impair coronary blood flow reserve.
What would happen in a lesion that is less than 50% stenosed after CABG?
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.
Definition of traditional revascularization
All diseased arterial systems receiving at least one graft insertion.
Definition of functional revascularization
Bypassing all diseased “primary” coronary segments (LAD,LCX,RCA).
What is the limit of a nondiseased vessel?
Any vessel of
CABG vs. PCI theory
CABG is complete vascularization with culprit lesion and future culprit lesions, PCI is with “suitable” culprit lesion
CABG vs PCI outcome
Fewer adverse events (all cause death) in CABG. PCI is only lower for stroke.
What is the total 30 day risk for CABG operative mortality?
3.05%
Risk of permanent stroke in CABG
1.63%
Risk of deep sternal wound in CABG
What additional risk factors add to CABG for mediastinits?
Obesity, COPD
What are the top 3 adverse outcomes of COPD?
Mortality, permanent stroke, renal failure requiring dialysis. Higher in emergency surgery.
What are the considerations in the EuroSCORE prediction of operative risk
Considers all patient factors (age, sex, COPD), cardiac factors (angina, LVEF), Operative factors (emergency, other surgeries, etc.) Must be calculated before each surgery.
What are the steps of myocardial revascularization with Coronary bypass
- 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.
What vessels can be used for bypass conduits?
Internal Thoracic Artery Radial artery Greater Saphenous Vein Gastroepiploic artery
What are the components of the Internal Thoracic Artery (ITA) used for graft?
LIMA (left internal mammary artery) or RIMA
What are the benefits to using the internal thoracic artery?
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.
How do outcomes compare in SVG vs LIMA in LAD bypass?
X 1.61 risk of death in 10 y X 1.41 risk of late MI X 2.00 risk of re-operation.
What is a skeletoned artery vs pedicled?
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.
What is the requirement for using the radial artery?
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.
What is the composite (T- or Y-) graft made of?
Components of the RIMA and LIMA.
What is the hierarchy of patency of arteries for graft?
LIMA is best (20y), RIMA, Radial, Gastroepiploic, SVG
What is the 5 year patency of the radial artery?
83-95%
What are factors that add to graft failure rate?
- The target vessel stenosis is less than severe 2. On the right coronary system.
What is the average duration of patency for a saphenous vein graft?
10years
What are the increased risks for impaired wound healing in SVG?
Ischemic heart disease, diabetes
What are the benefits of endoscopic?
Patients like it better but open surgery lasts longer.
How is heparin applied for CABG?
Full heparinization – ACT >480 seconds – to minimize thrombin formation within the extracorporeal circuit.. Rechecked every 15-20 min. Prevents pulmonary embolism.
What are the 3 cannulations that must be done during surgery?
Arterial cannulation : ascending Aorta. Venous drainage : 2-stage cannula , right atrial appendage. Cardioplegia : antegrade, retrograde.
What is cardioplegia?
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.
What does the cross-clamp do in CABG?
Clamps the aorta to prevent cardioplegia blood from reaching systemic circulation. Pressure makes cardioplegia blood enter carotid arteries.
What do the venous and arterial cannulae do in CABG?
Takes deoxygenated blood from venous system, oxygenates, goes into arterial tube and into aorta above the crossclamp.
What are the effects of cardioplegia?
Hypothermia lowers metabolism (reduced by 90%), diastolic arrest, potassium stops contractility of the heart, oxygen prevents ischemia.
How does retrograde cardioplegia work?
Through the coronary sinus with no valves can pass to coronary arteries. Usually combined with antegrade to sandwich the occlusion.
What needs to be done during chest wall closure of CABG?
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)
What is a special consideration for SVG?
Must turn upside down to account for valves.
What is the difference in off-pump CABG?
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.
What is a Maze procedure used for?
Atrial fibrillation, abnormal electrical pathways.
What is Maze?
Ablation of pathway of extra atrial foci by cutting incisions into atria. Controlled maze-like pathway into AV node.
What is the outcome of Maze procedures?
77% have sinus rhythm.
What is surgical ventricular reconstruction?
Cut aneurysm of LV and heart contracts better without it.
