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| Guest Commentary |
By Johannes Bonatti, MD and Guy Friedrich, MD
Depts. of Cardiac Surgery and Cardiology
Innsbruck Medical University, Innsbruck, Austria |
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Hybrid Coronary Artery Revascularization – Time To Reactivate The Concept?
Summary:
Hybrid coronary artery revascularization is a combination of minimally invasive left internal mammary artery bypass grafting to the left anterior descending artery combined with a catheter based intervention to other coronary arteries. Over the last 10 years this procedure has been developed from MIDCAB plus PTCA to totally endoscopic CABG procedures plus PTCA and drug eluting stenting. Logistic problems are the main reason why hybrid coronary artery revascularization has not reached broad application. Nevertheless the feasibility of simultaneous procedures has been demonstrated. Intense interdisciplinary cooperation between cardiac surgeons and interventional cardiologists will be necessary in order to further develop the highly appealing therapeutic concept of hybrid coronary artery revascularization.
Definition:
A hybrid in its original meaning in ancient Greek mythology is defined as a composite of two or more species of animal and/or human, the minotauros, a bull-human hybrid, being the most famous of these creatures [www.theoi.com/Ouranos/Minotauros.html ]. According to Webster’s 1913 dictionary a hybrid in biological terms is “The offspring of the union of two animals or plants derived from recognizably different genetic lines, as two distinct species, or two strains of the same species with known genetic differences; an animal or plant produced from the mixture of two genetic lines“. In medical terms a hybrid therapy or procedure is a mixture of therapies out of different subspecialties. By these definitions hybrid coronary artery revascularization is a combination between surgical and catheter based intervention on the diseased coronary arteries. Most commonly a left internal mammary artery (LIMA) bypass graft placed on the left anterior descending artery (LAD) in a minimally invasive or endoscopic fashion is combined with PTCA and stenting of the right coronary artery (RCA) or circumflex artery (Cx) system.
History:
With the advent of the MIDCAB (minimally invasive direct coronary artery bypass) operation in 1995 [2 ] the hybrid concept was discussed for the first time. The baseline situation was that the best revascularization strategy for the anterior wall, an internal mammary artery bypass graft, could be performed in a less destructive surgical fashion and that results of catheter based intervention on coronary territories other than the left anterior descending artery already in the mid 1990s were competitive for surgical revascularization using vein grafts.
In 1996 the first coronary hybrid procedures were reported by Angelini and coworkers in the Lancet [1 ]. A series of 6 patients received placement of a left internal mammary artery on the beating heart through left anterior minithoracotomy and PTCA or PTCA + stent on other coronary vessels. Two of these operations were carried out simultaneously in the cardiac catheterization laboratory. There was no postoperative mortality.
Several groups published small series of hybrid coronary revascularization thereafter [10,21,25] but for a variety of reasons the procedure never reached broad application. The technically demanding MIDCAB operation was abandoned by some surgical groups and logistics from the very beginning prevented a smooth introduction of a combined coronary intervention. Clear guidelines as to which part of the intervention should take place first were not developed. Only few institutions installed operating rooms with coronary angiography systems that allowed simultaneous operations, even though it was envisioned that such cath lab ORs would be one solution to the problem [13 ].
Refined thoracoscopic techniques for internal mammary artery harvesting were a next step that renewed the interest in MIDCAB and in hybrid coronary revascularization. Increased length of the LIMA conduit solved the problem of potential graft tension, the target vessel could be precisely marked, and the anastomosis could be performed through an even smaller incision that was placed exactly above the target vessel [19]. European and US groups have recently published series of such procedures and combinations with PTCA/stenting were included [6,22,24 ].
Robotic technology enabled totally endoscopic coronary artery bypass grafting (TECAB). In 1998 Loulmet performed the first left internal mammary artery bypass graft to the LAD as a TECAB procedure using remote access cardiopulmonary bypass [16]. Active groups in Leipzig, Dresden, and Frankfurt developed TECAB procedures both on the arrested and on the beating heart [11,15,9]. In 2000 the team from Aalst, Belgium reported the first hybrid procedure which combined an arrested heart TECAB LIMA to LAD and a catheter based intervention on the circumflex coronary artery [12]. This procedure was performed in a staged manner. In 2003 our group performed the first combination of arrested heart TECAB and RCA stenting in one simultaneous session [3 ].
Currently the hybrid concept is again discussed as drug eluting stents seem to challenge the results of arterial coronary artery bypass grafts. Prospective randomized studies [RAVEL, TAXUS] have shown single digit restenosis rates of coronary lesions in which drug eluting stents were implanted. In the proximal LAD, however, drug eluting stents do not yet reach the long term follow up performance of a LIMA graft. Would for the patient with multivessel disease a minimally invasive or totally endoscopic LIMA to LAD combined with drug eluting stents to other vessels be an attractive choice? The near future should show whether this concept can be a viable solution. Let us first go back to basic concepts of hybrid coronary revascularization.
The rationale for hybrid coronary artery revascularization I
LIMA- the best choice for the LAD:
According to newest literature the failure rate of a conventionally placed LIMA to LAD graft is 1% at 5 years [23]. Even with sirolimus eluting stents only a failure rate of 5% requiring reintervention at 9 months can be achieved on the proximal LAD, the corresponding in-segement restenosis rate is in the 10% range. [18]. Failure rates of drug eluting stents in the proximal LAD in the TAXUS trial were similarily high. Freedom from reintervention in patients who received a conventional single LIMA to LAD graft reach 89% at 10 years and 60% at 18 years [4]. For patients with totally isolated LAD lesions the freedom of reintervention at 18 years lies in the 80% range [4]. Placement of a LIMA to the LAD in conventional manner, through sternotomy, on pump, with cardioplegia is one of the saftest major procedures in surgery. Its mortality rates in the literature lie near zero percent. [20 ].
Mortality rates of minimally invasive single LIMA to LAD procedures are also reported in the near zero percent range. Recent prospective randomized trials comparing MIDCAB with bare metal stenting of the proximal LAD have clearly demonstrated benefits of surgery versus intervention [8 ]. Initial series of totally endoscopic LIMA to LAD grafting using robotics were performed with a similar low perioperative mortality rate and it can therefore be stated that minimally invasive techniques seem to be adequate methods for placement of this extraordinary conduit to the most important vessel of the heart
The rationale for hybrid coronary artery revascularization II
Catheter based intervention using drug eluting stents on non LAD lesions are as good as arterial grafts:
There is considerable evidence that restenosis rates after catheter based interventions on the Cx and RCA territories are lower than restenosis rates after interventions on the LAD [14,5]. Recent data have shown that radial artery graft 1 and 4 year failure rates are 4% and 11% [23]. 9 months target vessel reintervention rates in non LAD targets in the SIRIUS trial reached 3.4%, results which make catheter based intervention competitive with arterial surgical revascularization [18 ].
The rationale for hybrid coronary artery revascularization III
Catheter based intervention on non LAD lesions can be performed under the protection of a functioning LIMA graft to the LAD:
One intriguing fact about hybrid coronary artery revascularization is the possiblitiy to carry out catheter based intervention on non LAD territories under full protection of a LIMA to LAD graft. Even left main coronary artery PTCA and stenting can be relatively safely performed under protection of a LIMA to LAD and hybrid coronary revascularization procedures combining MIDCAB and left main catheter based intervention have already been reported [17 ].
Patient selection:
Indications:
Basically any patient with multivessel coronary artery disease who is suitable for minimally invasive LIMA to LAD placement and who’s coronary arteries other than the LAD are suitable for catheter based intervention is suitable for hybrid coronary artery revascularization. As many patients with multivessel disease present complex lesions and chronic total occlusions it becomes clear that only a certain segment of the CAD population would enter a possible evaluation process. As stated by Fosse and coworkers approximately 4% of patients referred for coronary angiography are potential candidates for a classic hybrid procedure [Fosse ICR Workshop 2003].
It can be stated that at present the majority of cases are indicated by surgeons that find a patient who exhibits the above mentioned inclusion criteria. This may of course vary between institutions but it can be speculated that most suitable candidates are treated by multivessel catheter based intervention whenever possible. Nevertheless there seems to be a considerable interest of interventional cardiologists in hybrid coronary revascularization. This has been recently shown in a survey among heart surgeons and cardiologists [7 ]. The same survey demonstrated a very limited practical experience of both cardiologists and surgeons with hybrid procedures.
Contraindications:
Contraindications can be derived from contraindications for a minimally invasive LIMA to LAD and from contraindications for catheter based intervention which are listed in Table 1.
| Table 1: Contraindications for hybrid coronary revascularization: |
| Contraindications for minimally invasive LIMA to LAD: |
| Subclavian artery stenosis |
| Known damage to the LIMA |
| Previous chest irradiation (relative) |
| Pleural adhesions (relative) |
| Intramyocardial LAD (relative) |
| Severe pulmonary disease precluding single lung ventilation |
| Additional valve disease |
| |
| MIDCAB specific: |
| Massive obesity (relative) |
| AH-TECAB specific: |
| Contraindications for remote access perfusion |
| (aortoiliac atherosclerotic disease, ascending aortic diameter >3.7 mm) |
| BH-TECAB specific: |
| Severe abdominal adhesions precluding subxiphoid placement of endo-stabilizer |
| |
| Contraindications for PTCA/Stent to the RCA and Cx System: |
| Chronic total occlusions (relative) |
| Complex lesions (relative) |
| (recurrent restenosis, angled lesions, bifurcation lesions, calcified lesions, Type C stenosis) |
Specific problems and questions:
Timing of the procedure:
The most frequently discussed topic in hybrid coronary revascularization is timing of the two coronary revascularization procedures. Performing the minimally invasive LIMA to LAD procedure first and the catheter intervention a few days afterwards offers the advantage that the LIMA to LAD graft undergoes direct quality control in the angiography suite. If problems with dilatation and stenting, however, occur, placement of a bypass graft in an additional operation through sternotomy may be necessary.
If the percutaneous procedure is done first, preferably immediately following diagnostic angiography, the patient receives one angiographic step and an operation thereafter. If the percutaneous procedure fails a bypass graft can be placed to the corresponding target vessel at surgery, which in this case is carried out through sternotomy. The disadvantage of this kind of timing is that the patients undergoes the minimally invasive LIMA to LAD placement most probably under aggressive antiplatelet treatment which may increase the perioperative bleeding risk.
Looking at these logistic problems a simultaneous intervention would be appealing. The patient would undergo diagnostic angiography and electively receive the minimally invasive LIMA to LAD and catheter intervention in one single session in a cath-lab OR.
Feasibility of simultaneous procedures:
The main obstacle for performance of simultaneous coronary hybrid revascularization procedures is availability of a cath-lab operating room. Angelini in his landmark series [1 ] demonstrated that MIDCAB can be carried out in a conventional cardiac catheterization lab. Fosse recently reported on 11 cases of MIDCAB combined with stenting of the RCA or Cx artery performed simultaneously in a special interventional center [Fosse ICR Workshop Innsbruck 2004]. During a 2.7 year follow up there were two deaths, 2 reinterventions on stents, and 1 reintervention on a LIMA graft. In May 2004 our group performed a simultaneous hybrid procedure combining an arrested heart TECAB LIMA to LAD and placement of a sirolimus coated CypherTM stent to the RCA in one single session. A mobile coronary angiography C-arm (GE OEC 9800) was used for the PCI part of the procedure.
A subspeciality “coronary therapist?"
As hybrid coronary revascularization includes logistic problems such as the involvement of a surgical and an interventional specialist discussions come up whether a single specialist is necessary who can cover both parts of the procedure. Occasionally surgeons have attempted to aquire PCI techniques and reported successful performance of PTCA and stenting. Complex interventional procedures, however, would probably remain difficult for a primarily surgically trained physician [Nataf ICR Workshop Innsbruck 2004]. The interest of interventional cardiologists to learn surgical techniques can at present be regarded as poor [Survey ICR Workshop Innsbruck 2004]. We therefore think that training single persons to perform the whole hybrid procedure will be more difficult than creating coronary revascularization teams consisting of dedicated surgeons and interventional cardiologists.
Results of hybrid coronary revascularization in the literature:
As can be seen in Table 2 the approximately 200 coronary hybrid procedures which are published in the current literature were performed with a highly acceptable mortality rate of 0%. The majority of patients in these publications underwent follow up angiography and as expected the three to six months failure rate of the LIMA to LAD graft was 0% to 3%. The limiting factor was restenosis in the dilated and stented coronary arteries which reached 7% to 24%. Bare metal stents were used in all these patients. The majority of these restenoses were treated by another catheter procedure. Data on longterm freedom from angina and major adverse events are too sparse to draw firm conclusions.
| Table 2: Results of hybrid coronary artery revascularization according to literature data |
| Author |
Year |
Journal |
Patients |
Mortality Periop % |
LIMA Stenosis 6 Mo. % |
PTCA/Stent Restenosis 6 Mo. % |
| |
|
|
|
|
|
|
| Angelini |
1996 |
Lancet |
6 |
0 |
n.a. |
n.a. |
| Friedrich |
1997 |
NEJM |
2 |
0 |
n.a. |
n.a. |
| Wittwer |
2000 |
AnnThorSurg |
35 |
0 |
0 |
7 |
| Riess |
2002 |
AnnThorSurg |
57 |
0 |
3 |
24 |
| Cisowski |
2002 |
EJCTS |
50 |
0 |
2 |
10 |
| Stahl |
2002 |
AnnThorSurg |
54 |
0 |
n.a. |
n.a. |
| |
|
|
|
|
|
|
| Total |
|
|
204 |
0% |
|
|
Current trends:
As mentioned above hybrid coronary artery revascularization is currently gaining renewed interest. There is a need to perform a prospective randomized multicenter trial comparing hybrid coronary artery revascularization with multivessel stenting and total arterial grafting. Performance of such a study poses multiple logistic problems including learning curves in the hybrid arm of the study, inhomogenity of the minimally invasive surgical techniques involved, and achieving an adequate patient sample size in the hybrid arm. Networks constisting of surgeons and interventional cardiologists interested in the procedure are currently formed and specific international meetings are held [www.icr-workshop.at ].
Future aspects:
In the ancient Greek mythology the most famous hybrid, the minotauros did not survive as this creature was killed by the human hero Theseus. Will there be a similar fate of coronary hybrid revascularization? In order to guarantee survival and expansion of this attractive type of revascularization procedure important steps are necessary:
Broader implementation will require acceptance of the obvious and striking advantages of a left internal mammary artery bypass graft to left anterior descending artery by the cardiology community. The heart surgery community will have to repeatedly underline the superiority of the LIMA to LAD. In addition heart surgery needs to persistently transport the information that a single LIMA to LAD bypass graft can be offered in a minimally invasive fashion with lowest mortality and morbidity rates
Maybe a more positive term for these procedures needs to be found. Such a term should include the technique applied and should be understandable for both patients and physicians. Integrated Coronary Revascularization (ICR), Combined Coronary Intervention (CCI), Stent and Surgery (SAS), and CABG “light” have all been suggested in discussions among cardiac surgeons and interventional cardiologists. Probably the term “intervention” should be used rather than an “operation."
Maybe more intense cooperation and opening of borders between cardiac surgery and interventional cardiology in a way that teams including members from both subspecialties work together in the OR, in the cath lab, or in a combined unit could push the acceptance of combined coronary intervention. In such a “fuzzy” structure where personnel and method flow is allowed between different specialities the potential for knowledge generation and innovative highlights is dramatically increased [Boekhoff ICR Workshop Innsbruck 2004]. We personally think that implementation of such structures is absolutely mandatory in order to enable a breakthrough of the hybrid concept.
References:
1. Angelini GD, Wilde P, Salerno TA, Bosco G, Calafiore AM. Integrated left small thoracotomy and angioplasty for multivessel coronary artery revascularisation. Lancet 1996;347:757-8 .
2. Benetti FJ, Ballester C. Use of thoracoscopy and a minimal thoracotomy, in mammary-coronary bypass to left anterior descending artery, without extracorporeal circulation. Experience in 2 cases. J Cardiovasc Surg (Torino). 1995;36(2):159-61
3. Bonatti J, Schachner T, Bonaros N, Laufer G, Kolbitsch C, Margreiter J, Jonetzko P, Pachinger O, Friedrich G. Robotic totally endoscopic coronary artery bypass and catheter based coronary intervention in one operative session. Ann Thorac Surg 2004 in press.
4. Boylan MJ, Lytle BW, Loop FD, Taylor PC, Borsh JA, Goormastic M, Cosgrove DM. Surgical treatment of isolated left anterior descending coronary stenosis. Comparison of left internal mammary artery and venous autograft at 18 to 20 years of follow-up. J Thorac Cardiovasc Surg. 1994;107:657-62 .
5. Briguori C, Nishida T, Adamian M, Di Mario C, Moses J, Colombo A. Multivessel coronary stenting: predictors of early and late outcome. Ital Heart J. 2000;1:420-5 .
6. Cisowski M, Morawski W, Drzewiecki J, Kruczak W, Toczek K, Bis J, Bochenek A. Integrated minimally invasive direct coronary artery bypass grafting and angioplasty for coronary artery revascularization. Eur J Cardiothorac Surg. 2002;22:261-5 .
7. D'Ancona G, Vassiliades TA, Boyd WD, Donias HW, Stahl KD, Karamanoukian H. Is hybrid coronary revascularization favored by cardiologists or cardiac surgeons?
Heart Surg Forum. 2002;5:393-5 .
8. Diegeler A, Thiele H, Falk V, Hambrecht R, Spyrantis N, Sick P, Diederich KW, Mohr FW, Schuler G. Comparison of stenting with minimally invasive bypass surgery for stenosis of the left anterior descending coronary artery. N Engl J Med. 2002;347:61-6 .
9. Dogan S, Aybek T, Andressen E, Byhahn C, Mierdl S, Westphal K, Matheis G, Moritz A, Wimmer-Greinecker G. Totally endoscopic coronary artery bypass grafting on cardiopulmonary bypass with robotically enhanced telemanipulation: report of forty-five cases. J Thorac Cardiovasc Surg. 2002;123:1125-31
10. Friedrich GJ, Bonatti J, Dapunt OE. Preliminary experience with minimally invasive coronary-artery bypass surgery combined with coronary angioplasty.
N Engl J Med. 1997;336:1454-5 .
11. Falk V, Diegeler A, Walther T, Banusch J, Brucerius J, Raumans J, Autschbach R, Mohr FW. Total endoscopic computer enhanced coronary artery bypass grafting. Eur J Cardiothorac Surg. 2000;17:38-45 .
12. Farhat F, Depuydt F, Praet FV, Coddens J, Vanermen H. Hybrid cardiac revascularization using a totally closed-chest robotic technology and a percutaneous transluminal coronary dilatation. Heart Surg Forum. 2000;3:119-20 ; discussion 120-2.
13. Fonger JD. Integrated myocardial revascularization. Eur J Cardiothorac Surg. 1999 Nov;16 Suppl 2:S12-7.
14. Hirshfeld JW Jr, Schwartz JS, Jugo R, MacDonald RG, Goldberg S, Savage MP, Bass TA, Vetrovec G, Cowley M, Taussig AS, et al. Restenosis after coronary angioplasty: a multivariate statistical model to relate lesion and procedure variables to restenosis. The M-HEART Investigators. J Am Coll Cardiol. 1991;18:647-56 .
15. Kappert U, Cichon R, Schneider J, Gulielmos V, Tugtekin SM, Matschke K, Schramm I, Schueler S. Robotic coronary artery surgery--the evolution of a new minimally invasive approach in coronary artery surgery. Thorac Cardiovasc Surg. 2000;48:193-7 .
16. Loulmet D, Carpentier A, d'Attellis N, Berrebi A, Cardon C, Ponzio O, Aupecle B, Relland JY. Endoscopic coronary artery bypass grafting with the aid of robotic assisted instruments.
J Thorac Cardiovasc Surg. 1999;118:4-10 .
17. Mack MJ, Brown DL, Sankaran A. Minimally invasive coronary bypass for protected left main coronary stenosis angioplasty. Ann Thorac Surg. 1997;64:545-6 .
18. Moses JW, Leon MB, Popma JJ, Fitzgerald PJ, Holmes DR, O'Shaughnessy C, Caputo RP, Kereiakes DJ, Williams DO, Teirstein PS, Jaeger JL, Kuntz RE; SIRIUS Investigators. Sirolimus-eluting stents versus standard stents in patients with stenosis in a native coronary artery. N Engl J Med. 2003;349:1315-23 .
19. Nataf P, Al-Attar N, Ramadan R, Scorcin M, Raffoul R, Salvi S, Lessana A. Thoracoscopic IMA takedown. J Card Surg. 2000;15:278-82 .
20. Ovrum E, Tangen G, Am Holen E. Facing the era of minimally invasive coronary grafting: current results of conventional bypass grafting for single-vessel disease. Ann Thorac Surg. 1997;64:159-62 .
21. Riess FC, Schofer J, Kremer P, Riess AG, Bergmann H, Moshar S, Mathey D, Bleese N. Beating heart operations including hybrid revascularization: initial experiences.
Ann Thorac Surg. 1998;66:1076-81 .
22. Stahl KD, Boyd WD, Vassiliades TA, Karamanoukian HL. Hybrid robotic coronary artery surgery and angioplasty in multivessel coronary artery disease. Ann Thorac Surg. 2002;74:S1358-62 .
23. Tatoulis J, Buxton BF, Fuller JA. Patencies of 2127 arterial to coronary conduits over 15 years. Ann Thorac Surg. 2004;77:93-101 .
24. Vassiliades TA Jr. Endoscopic-assisted atraumatic coronary artery bypass. Asian Cardiovasc Thorac Ann. 2003;11:359-61 .
25. Wittwer T, Cremer J, Klima U, Wahlers T, Haverich A. Myocardial "hybrid" revascularization: intermediate results of an alternative approach to multivessel coronary artery disease. J Thorac Cardiovasc Surg. 1999;118:766-7
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