Z Kardiol 87: Suppl 2, 175 – 180 (1998)© Steinkopff Verlag 1998

A. HaverichJ. Cremer

Perspectives of operative myocardialrevascularization – minimally invasivecoronary bypass – an alternative?

rung konnte das Verfahren zunehmendan Akzeptanz gewinnen. So wird eineständig wachsende Anzahl von Patien-ten mit proximalen LAD-Stenosenzugewiesen, und das Verfahren wirdmit wachsenden Erfolgsraten durchge-führt, wobei die frühpostoperativeIMA-Offenheitsrate etwa 98 % beträgt.

Besondere Charakteristika dieserneuen Technik zur Behandlung derkoronaren Eingefäßerkrankung stellendie verbesserten kosmetischen Ergeb-nisse, das geringe chirurgische Trauma,der verkürzte Krankenhausaufenthaltsowie Langzeitergebnisse vergleichbardenen konventionell angelegterMammaria-Bypässe zur LAD dar.

Schlüsselwörter Koronarchirurgie –minimal-invasiv – Mammaria-Bypass– MIDCAB

Summary Minimally invasive directcoronary artery bypass surgery hasevolved as a reliable method to performleft internal mammary artery (LIMA)bypass surgery to the LAD. This novel

technique represents a synthesis ofknown approaches to coronary surgeryusing sternotomy without extracorpo-real circulation and limited access tech-niques in general thoracic surgery.Applying specially designed tools forboth harvesting the internal mammaryartery and mechanically stabilizing theanterior surface of the heart duringanastomosis, this approach is gainingwidespread acceptance. A steadilygrowing number of patients with proxi-mal LAD lesions are submitted to car-diac surgery and the procedure is per-formed with increasing success rates,now approaching 98 % short termpatency.

Improved cosmetic results, less sur-gical trauma, decreased length of stayin the hospital, and comparable long-term results to open LIMA bypass toLAD are the key characteristics of thisnew approach to single vessel coronarydisease.

Key words Coronary surgery – mini-mally invasive – internal mammaryartery – MIDCAB

Prof. Dr. Axel Haverich (Y) · Jochen CremerKlinik für THG-ChirurgieMedizinische Hochschule HannoverCarl-Neuberg-Str. 130625 Hannover

Perspektiven der operativen Myo-kardrevaskularisation. Minimal-invasiver Bypass: Eine Alternative?

Zusammenfassung Die minimal-invasive, direkte koronare Bypasschirur-gie hat sich als zuverlässige Methodezur Durchführung von Mammaria-Bypässen zur left anterior descendingartery (LAD) entwickelt. Diese neuar-tige Technik stellt eine Synthesebekannter Verfahren der Koronar-chirurgie, über Sternotomie aber ohneextrakorporale Zirkulation, sowie mini-mal-invasiver Techniken der Thorax-chirurgie dar. Durch Verwendung spe-zieller Instrumente zur internal mam-mary artery (IMA) Präparation und zurmechanischen Stabilisierung der Her-zoberfläche während der Anastomosie-

Introduction

Minimally invasive or key hole surgery has entered the fieldof cardiac surgery rather late. First performed in gynecologicoperations, it has advanced to a routine mode of access in anumber of general surgical indications during the past decade.

In general thoracic surgery, a number of procedures are nowperformed by minimally invasive approaches, such as bull-ectomies of the lung and atypical resections for unknown lungdisease.

The main reason for cardiac surgery to be approached latewas the fact that direct visualization of the operative field,

176 Z Kardiol 87: Suppl 2 (1998)© Steinkopff Verlag 1998

extracorporeal circulation, and access to the entire organ,cannulation for delivery of cardioplegia and deairing weredeemed necessary for both safety and accuracy of the surgicalprocedure. In addition, the vast majority of patients with coro-nary artery disease with multi vessel disease are even today notsuitable for routine application of minimally invasive tech-niques. Like in many other medical and surgical fields, con-centration on single indications has resulted in acceptabletechnical approaches, patient management, and the resultsseen today with minimal invasive direct coronary arterybypass procedures (MIDCAB).

Techniques of minimally invasive coronary bypass

With the many technical modifications available today, theonly accepted technique with a sufficiently widespread appli-cation includes internal mammary artery bypass grafting to theLAD through a minithoracotomy without the use of extra-corporeal circulation (1, 3, 7–9, 11, 14). This technique hasevolved from a number of previous techniques on coronarysurgery via sternotomy without the use of extracorporeal cir-culation (2, 4, 6, 10, 12, 13, 15, 17, 18, 23). In these studies,techniques to slow the heart rate, to stabilize the surface at thesite of the anastomosis, and anesthesiological managementhave been evaluated and defined. An alternative on the oppo-site side of the scale includes induction of extracorporeal cir-culation via mini incisions in the groin, use of cardioplegia,and video-assisted surgery, including both valve operationsand coronary bypass grafting. This technique, the port access,has gained some acceptance in valve surgery, while manyinvestigators have disembarked from coronary operations. Themain issues are the significant morbidity associated withretrograde application of extracorporeal circulation and theimpossibility to perform video-assisted coronary anastomosesat this stage. Therefore, a direct approach to the heart at the siteof the anastomosis is still deemed necessary during minimallyinvasive coronary surgery.

For these reasons, MIDCAB procedures as describedabove, can be considered the only accepted mode of minimallyinvasive coronary surgery allowing for predictable results (9,14, 19).

Theoretically, the entire LAD system and the entire rightcoronary artery may be approached by MIDCAB. For the rightcoronary artery, the right IMAmay be used if the proximal por-tion is to be revascularized. The distal right coronary artery,however, can only be revascularized by a small (< 10 cm)incision in the lower portion of the sternum and the upperabdomen (16, 24). The vast majority of indications, however,is seen in proximal LAD lesions with single bypass graft to theLAD (14, 20). Since this approach has evolved as a comingroutine in coronary surgery both in terms of the equipment

available and number of cases performed worldwide, thetechnique will be presented in detail.

MIDCAB to LAD

MIDCAB to LAD involves a 8 to 10 cm transverse incisionalong the 5th rib parasternally. Using single lung ventilation(14), the chest is opened and a specially designed retractor(CTS) is inserted as to visualize the LIMA. This vessel is firstapproached at the site of the chest incision. Using either directvisualization or video-thorascopic techniques (7), the artery isharvested up to its origin from the subclavian artery and dis-tally to its bifurcation. Then, the epicardial fat is detached fromthe underlying surface, the pericardium is opened along thecourse of the LAD, which often can be visualized through theintact pericardium. The coronary artery is dissected in a rou-tine fashion. Proximally and distally, stay sutures are placedaround the LAD armed with a tourniquet to occlude the vesselduring anastomosis.

Then, a specially designed stabilizing instrument ismounted to the chest retractor and pressed onto the anteriorsurface of the heart with the LAD positioned between the twoarms of the instrument1. Proximal and distal vessel occlusionis performed, the LAD is incised after administration ofheparin (100 I.U./kg) with a previous 2 minute test periodlooking at blood pressure, pulmonary wedge pressure, andECG changes (preconditioning) (14).

Under direct vision, LIMA to LAD anastomosis is per-formed using routine techniques (8–0 prolene, running suture).Then, proximal and distal vessel occlusion is discontinued,final bleeding control and fixation of the IMA tissue pedicle isachieved by application of 0.5 cc of fibrin sealant2, adminis-tered as a spray. This prevents tension on the anastomosisupon reventilation of the left lung and twisting of the IMAalong its epicardial course. A small catheter is placed inter-costally and dorsal to the site of incision in the respective inter-costal space and externalized for later application of anal-getics (14). A single chest tube is inserted and the mini thora-cotomy is closed by two pericostal sutures, running absorbablesutures for the fascia, muscle, subcutaneous tissue, and skin.Usually, patients can be extubated within the next 4 hours afterthe procedure.

1 CardioThoracicSystems, 10600 N. Tantau Avenue, Cupertino, CA,U.S.A.

2 Tissucol, Immuno GmbH, Slevogtstr. 3-5, 69126 Heidelberg, Germany

A. Haverich and J. Cremer 177Minimally invasive coronary bypass

Patient population

CardioThoracicSystems registry

The international registry by the company manufacturinginstruments for MIDCAB surgery compiled 884 cases as ofSeptember 1997. Of these, 28 % were female, and the meanage at the time of operation was 63.0 years with a range from30 years to 91 years.

Significant co-morbidities are listed in Table 1. A signifi-cant proportion of MIDCAB patients had either undergoneprevious coronary artery bypass grafting (CABG) (8.3 %),prior PTCA (25.2 %), or stent implantation (10.4 %).

The vast majority (80.1 %) of LIMA grafts were anasto-mosed to the LAD (Table 2). In 9.9 % of cases, more than onecoronary vessel was either grafted (7.4 %), or treated withsubsequent interventional revascularization (hybrid proce-dure, n = 18).

Mean operation time was 136.7 minutes, ranging from 27to 480 minutes. Stay in the intensive care unit ranged from onehour to 376 hours with a mean of 25.3 hours. Hospital stayaveraged 4.9 days with 62 % of patients being dischargedbefore postoperative day four (Table 3). Pertinent outcomedata are listed in Table 4. Conversion to sternotomy or car-diopulmonary bypass occurred in 2.5 % and 1.6 %, respec-tively. Of note are the zero incidence of strokes and an accept-able incidence of both perioperative myocardial infarction(0.6 %) and death (0.7 %).

Hannover experience

Between 6/1996 and 9/1997, 142 patients underwent MID-CAB to LAD at Hannover Medical School. There were 111

Table 1 CTS registry: co-morbidities in MIDCAB patients

MI 341 (38.6 %)Diabetes 163 (8.4 %)Prior CABG 73 (8.3 %)Prior PTCA 223 (25.2 %)Prior Stent 92 (10.4 %)

Table 2 CTS registry: grafts description in MIDCAB patients

LIMA R LAD 708 (80.1 %)LIMA R D2 23 (2.6 %)Others 153 (17.3 %)Hybrid 18 (2.4 %)Multiples 55 (7.4 %)Comb 5) + 6) 73 (9.9 %)

Table 3 CTS registry: pertinent time intervals in MIDCAB patients (ICU= intensive care unit)

O Operation time 136.7 min (37–480)O ICU stay 25.3 hours (1–376)O Hospital stay 4.9 days (1–36)

< 4 days: 62 %

Table 4 CTS registry: outcome in MIDCAB patients (MI = myocardialinfarction)

Conversion sternotomy 2.5 %Conversion CPB 1.6 %Fractured ribs 9.3 %Strokes 0 %Periop MI 0.6 %Postop MI 0.5 %In-hospital death 0.7 %Reop bleeding 1.6 %

Fig. 1 Single mammary bypassgraft operations at HannoverMedical School 1993–1997

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men and 31 women, the mean age was 64 years with a rangeof 34 to 76 years. 117 patients had proximal stenosis of theLAD; 16 % patients had complete occlusion. The vast major-ity (85 %) had single vessel disease, there were 20 patients(14 %) with two vessel, and 18 patients (13 %) with three ves-sel disease. In the latter population, single LAD revascular-ization was either deemed sufficient for control of both painand impending infarction or the socalled hybrid procedure(vide infra) was attempted. This program developed from alimited experience of single IMA bypass surgery in the years1993 through 1995, where 63 such cases were performed viamedian sternotomy. Of these, only 10 were done without theuse of extracorporeal circulation. The number of single IMAgrafts increased to 50 in 1996 and 120 in 1997, of which 38(1996) and 94 (1997) were performed without the use of extra-corporeal circulation, employing MIDCAB techniques (Fig. 1).

The number of MIDCAB procedures performed each quar-ter following the first successful attempt in June 1996 isdepicted in Fig. 2. A cumulative description of the program isillustrated in Fig. 3, where both the number of cases and thenumber of referring cardiologists is shown. There has been aparallel development in both categories until September 1997.

Discussion

Minimally invasive techniques are currently applied in a num-ber of cardiac surgical procedures. Compared to aortic andmitral valve surgery as well as to congenital heart surgerycoronary bypass grafting by MIDCAB techniques has gainedsignificantly more acceptance. Adapted from techniques of

Fig. 2 Number of MIDCABprocedures at Hannover MedicalSchool per Quarter 1996/1997

Fig. 3 Cumulative number ofMIDCAB procedures (o-o) atHannover Medical School in1996/1997

I II III IV I II III

A. Haverich and J. Cremer 179Minimally invasive coronary bypass

“off pump” coronary revascularization on one hand andvideoassisted thoracic surgery on the other, the synthesis nowallows for its successful application in selected patients. Thepioneering stages of MIDCAB development are associatedwith Benetti (Argentina), Calafiore (Italy), Grandjean andBoonstra (Netherlands). In Germany, Cremer was the first toreport on a larger patient series (13).

At this stage of experience with the techniques, patientselection plays a pivoting role since the procedure has to bequalified against both conventional LIMAgrafting to the LADand interventional methods to treat proximal LAD lesions. We,therefore, insisted on operating patients with single vessel dis-ease without significant co-morbidity early in our experience(14). Soon, this was considered ethically no longer justified bya number of cardiologists who referred true “high risk”patients for MIDCAB in lack of realistic therapeutic alterna-tives. These high risk constellations involved both the cardiacstatus, especially the number of vessels diseased and left ven-tricular function, and also non-cardiac co-morbidity. Here,severe COPD, disabling cerebrovascular disease, reoperativecoronary surgery (15, 16, 21, 22), and calcifying aortic diseasewere predominant factors (14). For these reasons it soonbecame obvious that a uniform patient population cannot begenerated in this early phase of evaluation of the MIDCABconcept.

Therefore, it seems of special importance to standardize thesurgical approach in order to reject the null-hypothesis thatconventional – sternotomy, cardiopulmonary bypass – LIMAgrafts will provide better clinical and angiographic results.Accordingly, we focussed on single LIMA grafts to the LAD,exclusively. For the first 100 consecutive cases, routine earlyangiographic control of the LIMA graft was performed and aclose surveillance of perioperative complications such as

myocardial infarction, bleeding, and pulmonary complicationsas well as cerebrovascular accidents was performed. Theseresults will be presented elsewhere.

Our preliminary data as well as the data from the Cardio-ThoracicSystems registry would clearly suggest a highly com-petitive outcome in MIDCAB patients (19) when looking atperioperative death, myocardial infarction and, especially,cerebrovascular accidents. However, there is still a lack ofangiographic data proving patency rates of IMA grafts to becomparable to patency after conventional surgery. Our ownangiographic controls have shown 2 of 97 grafts to be occludedearly, within the first week postoperatively. These results mustbe confirmed in larger series, including more surgeons, morecenters, and longer follow-up times. Respective controlledstudies are on their way, namely the POEM study. Here 6 USand 2 European centers will perform routine angiographiccontrol in 200 cases with MIDCAB LIMA to LAD comparedto 200 conventional LIMA to LAD patients in multivesselrevascularization. Also, a prospective randomized study in 2European centers comparing percutaneous interventionalapproaches (PTCA, stent) versus MIDCAB in single proximalLAD disease will be performed.

Finally, the socalled hybrid procedure in multivessel coro-nary disease is currently conceptually addressed. Here, thesequential approach of MIDCAB LIMA to LAD grafting fol-lowed by interventional techniques for treatment of RCA andcircumflex lesions will be investigated. Based on the results sofar obtained with MIDCAB surgery, the authors are positivethat this novel technique will gain its firm place in both singlevessel coronary disease and LIMA protected interventionalcoronary revascularization in future. Its role in multivesseldisease as well as in reoperative surgery, however, needs to bedefined yet.

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