Coronary artery bypass questions Flashcards
What is risk and important predictors of morbidity and mortality following CABG
Stroke (3.1%)
Deep Sternal wound infection (2.5%)
Renal Failure (7.7%)
post op AF (28%)
Post op mortality (1.2%
Long-term survival influenced by
age, DM, number of vessels of coronary artery disease, gender, LV functionLong term patency of bypass grafts
Conduit patency time
LIMA 95% 10 years
Free LIMA 90% 10 years
RIMA 90% 10 years
Radial artery 80% 9 years
GEA 63% 10 years
inferior epigastric 80% 1 year
long saphenous 80% 9 years
short saphenous 60% 3 years
Cephalic vein 45% 5 year
Cyroprhomograft vein 15% 1 year
What is evidence for radial artery for conduit
The RAPCO trial is a randomized controlled trial that assigned 621 patients to either RA, SV, or free right ITA for the largest coronary target other than the left anterior descending coronary artery.
Patency rates reported at 8 years (83.6% RA and 76.5% SV) are lower than the latest reported patency rates of RAPCO patients (90% for RA; and 82% SV on a 5-year average follow-up
mortality was 8.03% in the radial artery group versus 12.5% in the saphenous vein group
What is RAPS evidence to use radial for CABG
5 year outcomes after within-pt randomizationof bypass grafts to the circumflex arteries using saphenous vein graft (SVG) for one and radial for the the other
Functional occlusion was more common after SVG than RA (19.7% vs 12%), and complete occlusion was also more common after SVG than RA (18.6% vs 8.9%)
What are contraindications to use of the radial artery
Insufficient ulnar artery flow, Allens test > 6 seconds, or > 50% on stenosis on u/s
Raynauds’s disease
Emergency surgery
need for high dose inotropes highly likely
Musician or surgeon
Use of a radial artery graft is reasonable when?
Class II B evidence
may be reasonable when grafting left-sided coronary artery with severe stenosis (>70%) and right sided lesions (> 90%) that perfuse LV myocardium.
What are charaterisics of radial
Fenestrated internal elastic lamina
Thicker media with thick myocyte content
Stronger contraction in response to norepinephrine resulting in spasm
Responds to vasodilators such as calcium channel blockers, papavarine, nitrates and milrinone.
28% will have atherosclerosis at time of harvest compared with 6% IMA
Who should get complete arterial revascularisation
All class IIb indications
Age < 60
few or no comorbidities
Arterial graft to RCA only when a critical lesion of > 90%
Radial graft to left sided lesion > 70% and right sided lesion > 90% that perfuse LV myocardium
What are the principles of drug-eluting stents
incorporate a drug (sirolimus or paclitazel) released slowly over months, which impairs the cellular proliferation and fibromuscular hyperplasi healing response to stent deployment and ballon barotraum.
Complications of stent deployment include
1) immediate complications (occlusion, stent thrombosis, embloism, dissection, side-branch occlusion and wire fracture
2) emergency CABG (0.3%), mortality (0.5%) , MI (0.8%), local vascular problems (2%)
3) In-stent stenosis, secondary to neointimal hyperplasit, which is reduced in DES as compared to bare metal stents
4) Late stent thormbosis, more common with DES as the polymer has inhibited endothelisation of the stent, hence when dual therapy is stopped, there is an increased risk of throbosis
What are the differences between LIMA and Radial artery
LITA muscular media has 6-12 elastic lamellae
Initma and subintima lie on a prominent internal elastic lamina, with few and small fenestrations (contrast to other small arteries with larger fenestrations that may permit entry of smooth muscle cells to initiaite plaque, may limit the development of atherosclerosis).
reduced smooth muscle mass (thin medial layer, limited vasoreactivity)
No vasa vasorum
Vasodilates readily (NO, Milrinone), limited vasoconstriction
Radial artery accompanied by 2 venous comitantes difference location media thicker than other arterial conduits and devoid of elastic fibers can be calcified or atherosclerotic easy to handle vs LITA highly vasoreactive (prone to spasm)
Contraindications to SVG harvest and use as a bypass conduit
varicose degeneration
superficial phlebitis
deep vein occlusion (where SVG is an important collateral)
List the contraindications to LITA
Prior damage due to chest wall irradiation or trauma
LITA important collateral for lower limb perfusion in patients with severe peripheral vascular disease (stenosis or occlusion of aorta) e.g., Leriiche’s syndrome
subclavian artery stenosis or occlusion
stensosis of subclavian
Av fistual
List the advantages and disadvantages of ITA skeletonization
Advantages:
preserves sternal blood supply
decreased incidence of deep sternal wound infection (especially high risk patients, e.g., DM)
greater length
facilitates sequential or Y graft anastamosis
improved ability to define spasm
preserves intercostal nerves (decreased incidence of neuralgic pain
Disadvantages:
unknown long-term patency
increased risk of injury
longer harvest times
What is evidence that BIMA is better then a LITA alone
There appears to be a 10% survival benefit at 10 year an 18% survival benefit at 15 years for BIMA
List contraindications to BITA
Chronic steroid use Morbid obesity Severe COPD (FEV1 < 1 L) Advanced age Emergency operation **Poorly controlled Diabetes mellitus Subclavian stenosis Calcification of mammary AV fistula in same arm
What are contraindications of off-pump CABG
Absolute hemodynamic instability (secondary to myocardial ischemia or acute MI) electrical instability (arrhythmias) Relative intramyocardial coronary arteries extreme cardiomegaly small diffusely disease coronary arteries calcified coronary arteries
Mechanisms of SVG failure
Early SVG occlusion
thrombosis
technical factors (anastamotic stenosis, kinking)
poor distal runoff or competitive flow from native CA
Intermediate (1 month to 1 year)
intimal hyperplasia (fibroplasia)
factors include: platelet aggregation, growth factor secretion, reduced NO and prostacyclin production
Late occlusion (>1 year)
atherosclerosis
Rate of closure from year 1-6 is 2%/year loss
Rate of closure afterwards 4-5%/year
What are ways to differentiate between post MI VSD and post MI papillary rupture
- Systolic murmur with septal rupture is more prominent at the left sternal border, wheras the murmur resulting from a ruptured papillary muscle is best heard at apex
- The murmur associated with septal perforation is loud and associated with a thrill, whereas the murmur with acute MR is sifter and has no thrill
- Septal rupture is more likely associated with anterior infactions and conduction abnormalities, whereas papillary is more likely with inferior infarctions and no conduction abnormalities.
What are two tests that should be performed to assess post MI VSD or papillary muscle rupture
Right heart cath.–Septal rupture you see a step up between the right atrium and the pulmonary artery in oxygen saturation. Step up for greater then 9% confirms the presence of a shunt. Qp:Qs range from 1.4 to 8:1 and roughly correlates with the size of the shunt.
In MR there are classic giant V waves in the pulmonary artery wedge tracing pressure.
Transthoracic echo, especially with color flow doppler. Detect size of defect, location, right and left heart function, excluded coexisting mitral regurgitation
page 605 cohen.
What is natural history of post MI CSD
25% die in first 24% 50% die in 1 week 65% die in 2 weeks 80% die in 4 weeks 7% alive in one year
What are classification of post MI vsd
Apical
Anterior
posterior/inferior
what are 2 basic repair strategies for post MI VSD
infartctectomy infarct exclusion (this is best used for posterior)
What are rates, complications, and risk factors for GI complications post cardiac surgery
In a 5 year series it was reported @ 0.48%. GI bleeding (82%), Intestinal ischemia (8.5%), perforated duodenal ulcer (2.8%),
12 parameters were identified as risk: age > 65, low left ventricular function, preoperative elevated scerum cr, on pump, prolonged CPB and aortic cross clamp, congenital heart disease, aortic surgery, use of IABP, blood transfusion, HCO3
Surgical intervention needed in about 20% and in that group mortality was 85%. The highest mortality is in intestinal ischemia with a mortality of 42.8%.
What is the evidence of dual antiplatelet agents post on or off bypass
New studies appear to be suggesting that venous graft patency is improved with plavix plus asa. It appears to affect the resistance of antiplatelets (asa resistance has been as high as 32%).
When is evidence for complete arterial revascularization?
Class IIb evidence:
Maybe reasonable in patients less then 60 years of age with minimal comorbidities
for elective surgery when should Plavix and Ticragrelor be stopped?
When should Eptifibatide or tirofiban be stopped?
When should abciximab be stopped?
Elective
5 days for clopidogrel and ticrelor and 7 days for prasugrel
Urgent at least 24 hours
Short-acting Glycoprotein IIb/IIA inhibotors (eptifibatide or tirogiban should be stopped for 2-4 hours) and abciximab for at least 12 hours).
