Arterial Conduits in Coronary Artery bypass Grafting

Lee G. McCann, II, MD

Cardiothoracic Surgeon, Central Utah Clinic

Objectives: • Describe conduit options in coronary bypass surgery • Review data on arterial versus vein grafting • State possible impact on mortality and reintervention

Searching for the Second-Best Conduit in CABG? Lee McCann M.D. Intermountain Heart and Vascular Services at Utah Valley Regional Medical Center Utah Valley Heart and Lung Surgical Associates

Objectives

1. Review the data on arterial grafts. Are they better than saphenous vein in terms of patency? Survival?

2. What are the best methods for using arterial grafts?—harvest, placement, medications

3. Are there certain CABG cohorts that benefit?—age, diabetes etc.

4. Review our data at UVRMC on arterial graft usage and compare regionally and nationally

Background

• Loop at Cleveland Clinic publishes landmark study on the routine use of LIMA—1986 – Improved survival – Decreased incidence of MI – Decreased repeat intervention

• Patency rates 90-95% at 10-15 years • Numerous studies confirmed, patency and survival • Benefits extend into 2nd -3rd decades of follow-up

Loop et al. NEJM 1986;314:1-6

Second best graft?

• Saphenous vein • Radial artery • Right IMA • Gastroepiploic • Cryo-vein (cadaveric)

Saphenous vein • Conduit of choice for fifty years > 95% of

grafts in STS database • Fast, easy harvest--endoscopic, abundant,

good length, technically easy, low risk • Reported patency 50-60% at 5-10 year

interval. (More recent up to 80% at 5 yrs.) • Thin endothelium, muscular media, less NO • Shear susceptibility—intimal hyperplasia from

attempt to normalize the injury from arterial pressures

Radial artery • Infrequently used < 5% of grafts in STS

database (10% in Europe) • Technically more demanding harvest and

use, shorter length, more time, risk of ischemic complication (minimal) more exclusion criteria

• Reported patency 80-90% at 5-10 year interval.

• Thinner intima, muscular media, more NO, resistant to atherosclerosis

• Spasm susceptibility—”string sign” in 7-11% of grafts (no events and no inducible ischemia in areas supplied)

Fig 1

The Annals of Thoracic Surgery 2006 81, 112-119DOI: (10.1016/j.athoracsur.2005.06.076)

Radial artery

• Introduced in 1973 by Carpentier • Abandoned due to 35% rate of early occlusion, string sign • 1988--cardiologist sends a cine of a previous string sign

patient with patent radial • 1992--Acar publishes 100% patency in 56 radial grafts

Right IMA (Bilateral IMA—BIMA)

• Soon after LIMA benefit was recognized (1980’s) • Lytle publishes 20-yr survival results with BIMA,

Cleveland Clinic

Lytle et al. Ann Thorac Surg 2004

7 89 87 10 81 78 15 67 58 20 50 37

Year BITA SITA

Right IMA (Bilateral IMA—BIMA)

• Soon after LIMA benefit was recognized (1980’s) • Lytle publishes 20 yr survival results with BIMA,

Cleveland Clinic

• Identical to LIMA biologically, length issue (free graft), more time to harvest, risk of sternal wound complications (3x)

• Patency rates > 90% at 10 years, similar to LIMA

The Data

• 9 randomized trials (RIMA, RA, GEA vs. SV) • 25 retrospective and cohort studies (RA vs. SV)

• 3 meta-analysis studies (2011, 2013, 2014)

Study Limitations • RCT • Not representative of “real-life

population, • highly selected and standardized • Small sample numbers at long

term follow-up, inadequately matched

• Observational (retrospective) • Higher numbers • “real-life” more consistent with

routine practice • Lack standardization • Selection bias • Follow-up inadequate • “Propensity matching” to

compensate

Desai et al. NEJM 2004

RAPS • 561 patients, 13 centers (Canada and New Zealand) • Radial randomly assigned to RCA or LCX distribution and

SVG to the opposite • Each patient serving as own control • 440 pt. had angiographic f/u 8-12 months, TIMI flow

assessed, “string –sign” • Graft occlusion 13.6% of SVG, 8.2% of RA, p =.009 • 5.4% absolute reduction • 40 % relative reduction in graft occlusion

RAPS-5 yr data

• 561 patients, 13 centers (Canada and New Zealand) • 358 pt. alive and eligible and 269 had cath (75%) • Graft occlusion 19.7% of SVG, 12.0% of RA, p = .03 • 7.7% absolute risk reduction • 40% relative risk reduction in graft occlusion

Deb et al. JACC 2012

Functional graft occlusion

Complete graft occlusion

• 142 randomized to RA or SVG to LCX system.

• 5yr angiographic f/u on 103 pt.

• 98.3% RA patency • 86.4% SV patency

Collins et al. Circulation 2008

RAPCO--6 year interim data

Hayward et al. Ann Thorac Surg 2007 Hayward et al. Eur J Cardiothorac Surg 2008

Patency

Survival

• 8622 isolated CABG, 1993-2009 • Two groups—LIMA/SV (n=7435), MultArt (n=1187) • Propensity matched cohort 1153 to the MultArt group • Follow-up on 7951 up to 18.3 years, (mean 7.6 yrs) 94% • Univariate and multivariate regression

Locker et al. Circulation 2012

At 15 years MultiArt grafting—with at least one additional arterial graft added to LIMA—resulted in significant improvement in Kaplan-Meier estimates of survival for the following subgroups: • Male and Female • Age > 65 and age 50% • 3-VSD or 2-VSD • Urgent/Emergent

• Meta-analysis of 35 angiographic studies—RCT and observational, RA vs. SV patency

• Divided into early 1yr patency (6795), mid 1-5yr (3232) and long-term >5yr (1157)

• Early OR 1.04 • Mid OR 2.06 • Long OR 2.28

• Conclusion: RA is a superior conduit to SV

past 1 year considering the surrogate outcome of patency

Athanasiou et al. Eur J Cardiothorac Surg 2011

• Network meta-analysis—technique to assess more than two strategies simultaneously, (ie. RIMA, RA, GEA and SV)

• 9 RCT analyzed angiographic outcomes, mean f/u 1-7.7 yrs. • 2780 patients, 1620 angiographies • RIMA—145, RA—871, GEA—92, SVG—845

Benedetto et al. Eur J Cardiothorac Surg 2014

• All studies--Rank probability of graft occlusion —best to worst: – RIMA 75% (probability of being best) – RA – SV – GEA 82% (probability of being worst)

• Late >4yr--Rank probability of graft

occlusion—best to worst: – RIMA 74% (probability of being best) – RA – SV 96% (probability of being worst)

Summary

• RCT’s with f/u greater than a year show superiority of multiple arterial grafting strategy on patency but not survival

• Observational cohort studies in general favor multiple arterial grafting and show benefit in terms of patency and survival

• Meta-analysis studies show superiority of multiple arterial grafting on patency

• Graft superiority: LIMA/RIMA→ RA→ SV→GEA

Best Methods • BITA can be used as pedicled or free graft with the same patency

rates • Preference should be given to the LCX system over the RCA

(except for dominant high-grade stenosis) • Skeletonization has shown decreased rates of sternal complications • Avoided in obese, IDDM, severe COPD • Proximal to the aorta has better patency than Y-graft to LIMA • When going to RCA, should try to get PD to avoid future distal

disease • RIMA and LIMA have identical patency to LAD. (LIMA to LCX)

Pedicled Skeletonized

Best Methods

• BITA less susceptible to spasm than RA, highest NO • Can be placed to stenosis of > 60-70% • RA needs to be placed to stenosis of 80-90% for best

results and less “string sign” (7-11%) • Radial can be harvested with equal patency, open or

endoscopic, however skeletonized again seems to have better patency than pedicled

• Most studies document 2-3% of radials are not usable

• Deaths 0% • 3 MI 9.7% • 4 recurrent angina 26.6%

Miwa et al. Ann Thorac Surg 2006; 81:112

Note: Univariate and multivariate analysis both showed two predictors of “string sign.” 1. Target stenosis

Best Methods

• All arterial grafts need spasm prophylaxis • Papaverine intraluminal and soak after harvest • Nitro drip for 24 hrs. perioperative, then oral CCA or

nitrate for 6 months up to a year • Not much evidence for CCA in vitro or in vivo. There is

some in vitro data for nitrates. Both are used clinically • Radial cath may cause vascular dysfunction for up to 3

months and should be avoided.

Best Methods

• Most studies document additional 20-40 minutes for BITA or radial use compared to SV

Who benefits?

• In addition to Mayo data • Diabetes • Age and Sex

Diabetes (survival) • 642 with LIMA/RA ± SV compared with 1201 LIMA/SV • Propensity matched each group with 409 pt.

1 98 96 5 89 87 10 77 64 12 70 59

Year RA SV

• Multivariate analysis revealed only factor protective against mortality: use of RA, OR 0.683

• > 30% risk reduction in mortality

Hoffman et al. J Cardiothorac Surg 2013

Age and Sex (survival)

Habib et al. Ann Cardiothorac Surg 2013

How are we doing?

• Compare regional data (Intermountain heart programs) • National (STS)

CAB (2014-H2)

• Dixie 597 2 0.3% • McKay 466 0 0% • UVRMC 487 29 6.2% • IMED 561 1 0.2%

Loc. n RA % 2012

• Dixie 716 0 0% • McKay 419 3 0.7% • UVRMC 458 22 4.8% • IMED 530 0 0%

Loc. n RA % 2013

Summary and Conclusions

• Second best graft for CABG is in all probablility the same as the first best—IMA, followed closely by RA.

• Despite fairly conclusive data in favor of multiple arterial grafting over three decades and in RCT, observational and meta-analysis studies, BITA and RA grafts are underutilized in the US (5%) and Europe (10%)

Summary and Conclusions

• Benefit is time dependent--small differences in early patency, significant at mid and long-term. Survival differences are still being debated but generally accepted in mid and long-term

• Most cohorts and conditions benefit including high-risk, elderly and diabetics

• Specific best practices including harvest techniques, graft placement and prevention of graft spasm are important to success

Summary and Conclusions

• UVRMC is above national and well above regional arterial graft usage.

• LIMA is a mandatory NQF quality measure for CABG. Multi arterial grafting or possibly a second arterial graft may be added as a quality measure in the future.

06_1McCann-Arterial Conduits in Coronary Artery bypass Grafting06_McCann_artCABG2Slide Number 1ObjectivesBackgroundSecond best graft?Slide Number 5Slide Number 6Slide Number 7Saphenous veinRadial arterySlide Number 10Radial arteryRight IMA (Bilateral IMA—BIMA)Slide Number 13Slide Number 14Right IMA (Bilateral IMA—BIMA)The DataStudy LimitationsSlide Number 18RAPSRAPS-5 yr dataSlide Number 21Slide Number 22Slide Number 23RAPCO--6 year interim dataSlide Number 25Slide Number 26Slide Number 27Slide Number 28Slide Number 29Slide Number 30Slide Number 31Slide Number 32Slide Number 33Slide Number 34Slide Number 35Slide Number 36Slide Number 37Slide Number 38SummaryBest MethodsSlide Number 41Best MethodsSlide Number 43Slide Number 44Best MethodsBest MethodsWho benefits?Diabetes (survival)Age and Sex (survival)How are we doing?Slide Number 51Slide Number 52Slide Number 53Slide Number 54Summary and ConclusionsSummary and ConclusionsSummary and Conclusions