minimal invasive cabg
TRANSCRIPT
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
47
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
48
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
49
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