CORONARY ARTERY BYPASS SURGERY Flashcards
What are the class I indications for coronary artery bypass grafting (CABG)?
Significant left main stenosis, three-vessel coronary artery disease (CAD), two-vessel disease involving proximal left anterior descending (LAD) artery
According to the American College of Cardiology/American Heart Association (ACC/AHA) guidelines.
What is a class IIa indication for CABG?
Single-vessel proximal LAD disease, two-vessel disease without proximal LAD but with extensive ischemia
CABG should be considered as a reasonable treatment strategy.
In which scenarios should CABG be considered for patients?
Not suitable for or having failed PCI, left ventricular (LV) dysfunction, persistent ischemic symptoms
CABG is also performed in conjunction with valvular or aortic surgery.
What did landmark trials in the 1980s reveal about CABG compared to medical therapy?
Long-term superiority of surgery over medical therapy in left main disease (LMD), multivessel disease (MVD), proximal LAD involvement, and LV dysfunction
Trials included the Veterans’ Affairs (VA) cooperative trial, European Coronary Surgery Study (ECSS), and Coronary Artery Surgery Study (CASS).
What were the findings of a contemporary study on invasive vs conservative strategy for stable CAD?
No difference at 3.2 years, but excluded patients who typically benefit from surgery
25% of invasive arm underwent CABG; 75% underwent PCI.
How do drug-eluting stents (DES) compare to CABG in terms of revascularization?
CABG associated with lower rates of repeat revascularization compared to PCI
Registry studies show improved survival rates with CABG for double- and triple-vessel disease.
What is the SYNTAX score?
A scoring system to quantify the extent and complexity of CAD based on cardiac catheterization findings
Scores are divided into low (0–22), intermediate (23–32), and high (≥33).
Which patients benefit most from CABG?
Patients with significant LMD, proximal LAD, multivessel CAD, and lesions not amenable to PCI
Presence of diabetes and depressed LV function favor surgical revascularization.
What is cardiopulmonary bypass (CPB)?
A machine providing circulation and oxygenation during surgery, allowing the heart to be stopped
Components include tubing, a reservoir, oxygenator, heater-cooler machines, and a pump.
Why is heparin used during CPB?
To prevent clotting and embolization in the thrombogenic CPB circuit
Standard dose is 300 U/kg to achieve a target activated clotting time (ACT) greater than 480 seconds.
How is the heart stopped during CPB?
By placing a cross-clamp across the ascending aorta and administering cardioplegia
Cardioplegia can be given in antegrade and retrograde fashion.
What strategies protect the myocardium during cardiac arrest in bypass surgery?
Unloading ventricles, cooling, and arresting the heart with cardioplegia
The greatest decrease in oxygen demand occurs with diastolic arrest through cardioplegia.
What is the long-term patency rate of saphenous vein grafts (SVG)?
1-year attrition rate up to 15%, 10-year patency rate traditionally cited at 60%
SVGs comprise over 80% of bypass grafts in the U.S.
What are the benefits of using the internal thoracic artery (ITA) for bypass?
High nitric oxide levels, rarely affected by atherosclerosis, 90% patency at 10 years
ITA is used primarily for bypassing the LAD, which supplies over 55% of LV mass.
What other arterial conduits can be used for bypass?
Right ITA (RIMA), radial artery (RA), gastroepiploic artery (GEA)
Multiarterial strategies aim to improve long-term patency rates.
What is off-pump CABG (OPCAB)?
A technique of CABG performed without the use of cardiopulmonary bypass
It contrasts with on-pump CABG, which uses CPB.
What is off-pump CABG (OPCAB)?
OPCAB is performed without the use of the CPB machine, keeping the heart beating throughout the procedure.
It eliminates side effects of extracorporeal circulation like coagulopathy and inflammation.
What are the main differences between on-pump and off-pump CABG?
On-pump CABG uses CPB, while off-pump CABG does not.
On-pump is said to provide better hemodynamic stability and allows for complete revascularization.
What are the reported outcomes of OPCAB compared to on-pump CABG?
Literature shows equivalent outcomes with no demonstrable differences in mortality, stroke, or MI rates.
Some studies report lower transfusion rates and shorter hospital stays with OPCAB.
What is minimally invasive cardiac surgery (MICS)?
MICS refers to surgical techniques that avoid the sternotomy incision used in standard CABG, such as MID-CAB and robotic CABG.
MID-CAB typically involves a small left lateral thoracotomy incision.
What is a hybrid procedure in CABG?
A hybrid procedure combines PCI and surgery, often involving LITA-LAD bypass.
It can be performed off-pump or as a MID-CAB approach.
What complications can occur following CABG?
Complications include stroke, MI, renal failure, respiratory failure, and mediastinitis, with an operative mortality of 1% to 2%.
Atrial fibrillation (AF) is also common, occurring in 20% to 40% of cases.
What are the risk factors for mediastinitis following CABG?
Risk factors include diabetes, COPD, morbid obesity, and bilateral ITA harvesting.
Staphylococcus is the most common organism cultured in mediastinitis cases.
What causes strokes after CABG?
Strokes can be caused by atheroemboli from the ascending aorta, microemboli, and regional brain hypoperfusion.
The incidence is 1% to 3% and increases with age.
How should anticoagulants be managed preoperatively for CABG?
Anticoagulants are typically withheld to reduce bleeding risk; clopidogrel and ticagrelor should be stopped for 5 days, and prasugrel for 7 days.
Direct oral anticoagulants (DOACs) are withheld for 2 to 4 days preoperatively.
Which patients should be on dual antiplatelet therapy (DAPT) after CABG?
All post-CABG patients should take aspirin; those with ACS should resume P2Y12 inhibitors after surgery.
DAPT for 12 months may improve vein graft patency in stable ischemic heart disease patients.
What factors are important in the follow-up of CABG patients?
Secondary prevention includes statins, beta-blockers, aspirin, ACE inhibitors for low ejection fraction, smoking cessation, and control of hypertension and diabetes.
These measures are essential for long-term success.
What is the incidence of recurrent disease requiring redo CABG?
The incidence of reoperations is around 10% by 10 years.
Aggressive secondary prevention has reduced the need for reoperations.
