Minimal Invasive CABGTechnical Concepts and Results

Dr. Deep Chandh Raja.S

GOAL OF CABG

• Complete revascularisation of the area of myocardium that is perfused by a coronary artery with ≥50% stenosis (Hills et al. CIRCULATION 2011, Practice guidelines)

• Conventional CABG Median sternotomy with help of cardio-pulmonary bypass

• Heart-Lung machine with Cardioplegic cardiac arrest

OUTLINE• BASIC CONCEPTS IN CABG- Conduits, Heart Lung

Machine, Cardioplegia• Demerits of conventional CABG• Introduction of OPCAB• Various terminologies- OPCAB, MIDCAB, TECAB, PACAB• Types of Minimal Invasive CABG surgery• MIDCAB-techniques • Trials with respect to OPCAB/MIDCAB vs

Conventional• Short views on PACAB, TECAB, HYBRID CABG

Basic Surgical Process of CABG

• Graft Harvesting – LIMA, LSVG, RIMA, Radial A.• Heparinization• Cardioplegia• CPB Cannulation• Distal Anastomosis (Snaring & shunting)• Proximal Anastomosis• Reversal of Protamine• Decannulation• Maintenance of normothermia, graft patency,

coagulation

CONDUITS IN CABG• ARTERIAL LIMA, RIMA, RADIAL

ARTERY, GASTROEPIPLOIC ARTERY, INFERIOR EPIGASTRIC ARTERY, SPLENIC ARTERY

• VENOUS SAPHENOUS VENOUS

PATENCY RATES OF CONDUITS1 year 10 years

SVG 80-90%(2%/yr upto 5 yrs.)

50%(5%/yr upto 10 yrs.)

LIMA 98% (93-98% depending on type of CABG))

>90%

Other arterial grafts 90% 60%

* Chikwe J, Beddow E, Glenville B. Cardiothoracic Surgery. Oxford: Oxford University Press; 2006

DETERMINING FACTORS FOR GRAFT PATENCY

• Venous vs Arterial- SVG not suited for high shear stresses of arterial circulation

• Type of arterial grafts- LIMA vs other grafts Muscular arteries-Radial, Epigastric,

Gastroepiploic• Target vessel- <70% stenosis in the native vessel

acts as a competitive supply to the target region leading to graft atrophy and occlusion, hence arterial grafts not used for these purposesARTERIAL GRAFTS HAVE POOR PATENCY IF USED TO GRAFT RCA WITH <90% STENOSIS CLASS III

LIMA- A Unique Conduit !!• RESISTANT TO ATHEROSCLEROSIS nearly

continuous elastic lamina, release of prostacyclins, high eNO activity, platelet inhibitors

• Less muscular than other comparable graft vessels

• Parent origin from SCA, no need for proximal anastomosis

• Good length

CONTRAINDICATION FOR LIMA HARVEST:1.Lt. SCA stenosis2.Poor LIMA flow3.Emergency surgery4.Radiation injury to LIMA

CARDIOPLEGIA• Potassium rich solution with varying concentrations of

blood, nutrients, bicarbonate, buffers, electrolytes• COLD 4 degree celcius

SIDE EFFECTS:• Duration of cardioplegia α myocardial dysfunction• Around 10-20% decline in myocardial function

immediate postop due to Myocardial edema, Ischemia-Reperfusion injury

• HYPOTHERMIA induced release of cytokines post perfusion

HEART LUNG MACHINE

• Blood comes in contact with tubings, reservoirs, filters• Form of artificial circulation in order to maintain

systemic perfusion

• Activation of complement system, leucocyte activation, depletion of platelets, clotting factors

• Need for heparinisation ACT maintained >400sec, 3mg /kg heparin

Mechanism of side effects in CABG• Aortic manipulation (cannulation, clamp,

anastomosis)Micro and macroemboli (cholesterol)• CPB microemboli (air, clots)• CPB Complement activation (↑s100 beta)SIRS

(MODS-ARDS, AKI)• CPB loss of platelets, coag. factors ↑ transfusion

of blood products and its inherent risks• Microemboli Neurological adverse effects ranging

from stroke to cognitive dysfunction• Large incision wound infection

Groom et al. Microemboli from cardiopulmonary bypass are associated with a serum marker of brain injury. J Extra Corpor Technol. 2010;42:40–4

COMPLICATIONS OF CABG• Low Output syndrome: 4-9%, managed with

inotropes, IABP• 1-5%- Myocardial Infarction• 30% Arrythmias• Adverse neurological outomes: 3% Stroke:2-4% Cognitive dysfunction: 40-60%• Renal Injury-4%• Transfusion• Upto 2.9 % perop mortality, increases to 7.2%>80

years

Perioperative complication Isolated CABG(%)

Euro Heart Journal

OFF PUMP (BEATING HEART SURGERY -BHS)

• OPCAB- Off Pump CABg• Majority of side effects of CABG specially

those related to CPB can be circumvented• Innumerous trials and RCTs between OPCAB

and conventional CABG Debate continues• Not immune to side effects, in fact has

created a new dimension of problems esp. cardiac motion

New ventures

• Minimally invasive CABG problems of a large incision can be overcome

• Space constraint, inaccess to posterior lateral branches, incomplete revascularisation

Confusing Terminologies• OPCAB• MIDCAB• PACAB• TECAB

BEATING HEART SURGERY: OPCAB, MIDCAB, TECAB

MINIMAL INVASIVE SURGERY: MIDCAB, TECAB, PACAB

MINIMAL INVASIVE CABG

• MIDCAB• PACAB• TECAB

- MIDCAB & TECAB are OFF PUMP- PACAB is ON PUMP

Definition- OFF PUMP CABG UNDERTAKEN WITHOUT A FULL MEDIAN STERNOTOMY

INDICATIONS

• SINGLE VESSEL DISEASE (NonPTCAable)• MULTI VESSEL DISEASE WITH HIGH PERIOP

RISK • HYBRID PROCEDURES (MIDCAB to LAD + PTCA

to other vessels)

HIGH RISK CASES FOR CABG

• High risk of deep sternal wound infection (e.g., diabetics, morbidly obese)

• Severely impaired left ventricular function• Chronic kidney disease • Significant carotid or neurological disease• Severe aortic calcification• Prior sternotomy, Redo CABG• Elderly

TECHNIQUES IN MIDCAB

• EXPECTED PROBLEMS• INCISION, POSITION• INSTRUMENTATION• STEPS

EXPECTED PROBLEMS

• BEATING HEART coronary motion, suturing related complications

• INTERRUPTION OF CORONARY FLOW regional ischemia, arrythmias

• COLLATERAL BLOOD FLOW hampers view• MINIMAL ACCESS to posterior heart, PLVs, OM

vessels manoeuvring the heart in a small space decreases SV significantly by ˜ 40%, Incomplete revascularisation

ANSWERS TO THE PROBLEMSANSWERS

CORONARY MOTION MECHANICAL TISSUE STABILISERS

INTERRUPTION OF CORONARY FLOW

ARTERIOTOMY SEAL, SHUNT, CANNULA

COLLATERAL BLOOD FLOW

SALINE/ CO2 JET

MINIMAL ACCESS APICAL STABILISATION, ROBOTS, HYBRID

STEPS OF MIDCAB

POSITION AND INCISION• 15-30° Right lateral position• 5-7 cm incision: 4th, 5th ICS• LAST- left anterior small thoracotomy• Multiple small incisions may be taken for

access to other sites- like subxiphoid incision for PDA

Deep Pericardial Traction Sutures

MICS RETRACTOR SYSTEM (THE BOW)

MECHANICAL TISSUE STABILISERS

• OCTOPUS™• PLATYPUS™ • IMMOBILISER™

Immobilises the target area of interest:- Evidence suggests better anastomotic results

than the prestabilisation device use era- Class 1 Indication for performing MIDCAB

APICAL & STABILIZATION DEVICE

LAST Lt.Pleural cavity opened, left lung

deflated, LIMA skeletonised

Pericardium opened, Deep pericardial traction sutures paced

Saline sprayer,OCTOPUSArteriotomyIntracoronary shunts

Anastomoses with continuous polypropylene sutures

Lt.Pleural/pericardial drain placed

LIMITATIONS

• Not more than 2 coronary arteries can be grafted (At present)

• Anastomotic site occlusion was frequent in the earlier daysREINTERVENTIONS

• Severe LV dysfunction surgeons prefer on pump CABG inspite of high risks

CONTRAINDICATIONS

• Small target vessels• Calcified target vessels• Diffusely diseased target vessels• Intramyocardial target vessel• Emergency cases• Patients with hemodynamic instability

MIDCAB VS ON PUMP CABG

CABG MIDCAB

INCISION MIDLINE 10-15 cm 5 cm

HEART-LUNG MACHINE + -

TECHNIQUE Less complex Steep learning curve

MORTALITY RATES SIMILAR SIMILAR (DEBATE !)

GRAFT PATENCY GOOD LESSER

REVASCULARISATION COMPLETE INCOMPLETE

REPEAT PROCEDURES LESS FREQUENT

TRANSFUSIONS MORE LESS

RECOVERY & LENGTH OF STAY

DELAYED & LONGER QUICKER & SHORTER

TRIALS

• Innumerous observational studies (cases series/nonrandomised comparison) published

• Few RCTs and Meta analyses• POEM STUDY 2001• ROOBY TRIAL 2009• CORONARY METAANALYSES 2012

• Perioperative mortality 2.5% comparable to 2.9% in conventional CABG

4 RCTs till 2001

POEM STUDY• 165 MIDCAB vs 145 onpump

CABG• Comparable LIMA patency

rates (96.5% in MIDCAB vs97.6%) at 1 yr

• Comparable MACCE rates• Advantages of MIDCAB-

lesser duration of hospital stay, lesser transfusions

*Mehran et al. CTT 2000

ROOBY TRAIL

• Largest RCT to date (Randomised On/Offpump Bypass trial)

• ˜2200 pts.• Neuropsychological outcomes similar in both

groups• MACE rate lesser and graft patency rate better

in ON PUMP conventional CABG

Results• There was no significant difference between

off-pump and on-pump CABG in the rate of the 30-day composite outcome (7.0% and 5.6%, respectively; P = 0.19).

• The rate of the 1-year composite outcome was higher for off-pump than for on-pump CABG (9.9% vs. 7.4%, P = 0.04).

• Patients with fewer grafts completed than originally planned was higher with off-pump CABG than with on-pump CABG (17.8% vs. 11.1%, P<0.001).

CRITICISM OF ROOBY TRIAL

• 99% Males• Low risk group• MIDCAB most suited for High risk patients

where a difference in outcomes can be demonstrated

• Meta-analyses of 59 trials involving 8961 pts – reduction in early strokes with off-pump – no differences in other major CV outcomes.

CORONARY INVESTIGATION OUTCOMES

44

OFF-PUMP (n = 2375)

%

ON-PUMP(n = 2377)

%p value

Any Blood Transfusion 50.7 63.3 <0.001

Antifibrinolytics 26.1 37.0 <0.001

Re-operation for bleeding 1.4 2.4 0.02

Peri-operative Transfusions and Bleeding

45

1st Co-Primary Outcome (30 Days)

46

Off Pump%

On Pump%

Hazard Ratio 95% CI

p value

Primary OutcomeDeath, Stroke, MI, Renal Failure 9.8 10.3 0.95 0.79-1.14 0.59

Components

Death 2.5 2.5 1.02 0.71-1.46

Stroke 1.0 1.1 0.89 0.51-1.54

Non Fatal MI 6.7 7.2 0.93 0.75-1.15

New Renal Failure 1.2 1.1 1.04 0.61-1.76

Other Outcomes at 30 days

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Off Pump%

On Pump%

Hazard Ratio 95% CI p value

Angina 0.1 0.1 1.50 0.25-8.99 0.66

PCI 0.5 0.1 3.67 1.02-13.2 0.05

Re-do CABG 0.2 0.04 6.00 0.72-49.8 0.01

PCI/Re-do CABG 0.7 0.2 4.01 1.34-12.0 0.01

All re-operations (re-do CABG) 3.3 3.9 0.85 0.63-1.14 0.27

All re-operations/Re-do CABG/PCI 3.7 4.0 0.94 0.70-1.25 0.65

Off Pump%

On Pump%

Relative Risk 95% CI p value

Respiratory Infection or failure 5.9 7.5 0.79 0.63-0.98 0.03

Acute Kidney Injury

AKIN Stage 1 28.0 32.1 0.87 0.80-0.96 0.01

RIFLE risk 17.0 19.6 0.87 0.76-0.98 0.02

New Renal Failure requiring Dialysis 1.2 1.1 1.04 0.61-1.76 0.77

Other Outcomes at 30 days

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Acute Kidney Injury Network (AKIN): absolute increase in serum creatinine value ≥27 µmol/L OR an increase of ≥150 % from the baseline serum creatinine value

Risk, Injury, Failure, Loss and End-stage Renal Disease (RIFLE): increase of ≥150 % from the baseline serum creatinine value

• At 30 days there was no difference in the primary outcome between Off pump CABG and On pump CABG (9.8% vs. 10.3%, p=0.59).

• Off-pump was associated with:–Less transfusions and re-operation for bleeding–Less acute kidney injury–Less respiratory infections/failure–More early revascularizations

Conclusions

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Early Cognitive Dysfunction

• Reference: Assessment of neurocognitive impairment after off-pump and on-pump techniques for coronary artery bypass graft surgery: prospective randomized controlled trial. Zamvar V, Williams D, Hall J, et al. BMJ 2002;325:1268-1273.

• Message: neurocognitive impairment more in ONPUMP CABG.

One week postop, 27% in the off-pump and 66% in the on-pump had neurocognitive impairment (P=0.004). Ten weeks postop, 10% of the off-pump and 40% of the on-pump had neurocognitive impairment (P=0.017).

Early Stroke• Reference: Safety and efficacy of off-pump coronary

artery bypass grafting. Arom KV, Flavin TF, Emery RW, et al. Ann Thorac Surg 2000;69:704-710

• Message: Several postoperative events are studied • Of Interest: There were no significant differences in

the number of patients who suffered from neurological deficits such as permanent stroke (2.0 % on-pump versus 1.4 % off-pump, p=0.42) and transient ischemic attack (0.9 % on-pump versus 0.3 % off-pump, p=0.35)

CONFLICTING EVIDENCEAUTHOR et al YEAR FAVOURS

Athanasiou 2004 Less stroke MIDCAB

Moller 2010 NO diff. in MACCE

Eifert 2010 NO diff. in MACCE

Jensen 2008 NO diff. in MACCE

Mack 2004 Lesser stroke MIDCAB

• All observational studies/ retrospective analyses from registries• No RCTs in High risk groups

2011 GUIDELINES (AHA STATEMENT)

“ BOTH CONVENTIONAL CABG AND MIDCAB HAVE SIMILAR OUTCOMES AND NONE HAS SUPERIORITY OVER THE OTHER”

• Periop STROKESIMILAR in both• MIDCAB advantageslesser neurocognitive dysfunction,

lesser renal dysfunction, lesser duration of hospital stay• CONVENTIONAL CABG advantages lesser complexity,

better access to posterolateral wall complete revascularisation

• Decision left to the surgeon to individualise the decision of minimally invasive off pump vs conventional cabg in a given patient

Prevailing practices

PTCA VS MIDCAB(esp. for PLAD)

• Buszman et al. JACC 2011• Around 200 pts. In each arm• NO short (30days) / Long term (5yrs.)

differences in MACE rates• ↑ short term adverse events like wound

infection, low output syndrome, bleeding in MIDCAB

• ↑ long term repeat revascularisations in PCI arm (72% IInd generation DES used)

HYBRID PROCEDURES• BEST OF BOTH WORLDS• Advantages of MIDCAB ( minimally invasive, off

pump, long term patency of LIMA)• Advantages of PTCA (difficult to approach vessels

like LCX)• NO TOUCH AORTIC surgeries

CLASS I INDICATIONS FOR MIDCAB/HYBRID:

Calcified proximal aorta

Unfavourable LAD/ Distal LM for PCI

Lack of conduits for grafting

Poor nonLAD targets for CABG which are amenable to PCI

STAGED HYBRID

• SINGLE need for HYBRID suites for both procedures to be done in same sitting

• 2 STAGED CABG f/b PCI within 36 hours

• UNIQUE CHALLENGES !!

MINIMALLY INVASIVE CABG

• MIDCAB• PA CAB• TECAB

PACAB• PumpAssisted minimal incision CAB-ON PUMP • Femoral CBP & Endoaortic clamp• Only advantages of a minimal incision

– Surgeons in the early phase of MICS experience– Before advent of tissue stabilisers

TECAB

• Totally Endoscopic CABG• Robotic assisted anastomoses• Early graft failure, reinterventions, CABG

conversion rates• At present, comparison of TECAB vs

conventional CABG is lacking

DA VINCI ROBOT

MIDCAB vs PACAB vs TECAB(Jegaden et al. JCTS 2011. Retrospective analysis)

• Early postop results • Follow-Up results

TAKE HOME MESSAGES

• Beating heart surgery- OPCAB• OPCAB + MINIMAL INVASIVEMIDCAB• Other minimal invasive surgeries: PACAB,

TECAB• OPCAB vs ONPUMP CABG: none superior• HYBRID CVR- promising concept with

collecting evidences and new challenges• HIGH RISK CABGMIDCAB may be considered