Eur J Cardiothorac Surg 1999;16:S67-S72
© 1999 Elsevier Science NL
Quality assessment in minimally invasive coronary artery bypass grafting
Anno Diegeler*,
Merhajoddin Matin,
Volkmar Falk,
Christian Binner,
Thomas Walther,
Rüdiger Autschbach,
Friedrich-Wilhelm Mohr
University of Leipzig, Heartcenter, Clinic of Cardiac Surgery, Russenstrasse 19, D 04289 Leipzig, Germany
* Corresponding author. Tel.: +49-341-865-1421; fax: +49-341-869-1452 (Email: diea{at}server3.medizin.uni-leipzig.de).
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Abstract
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Objectives: The most important determinant for the success of minimally invasive coronary artery bypass grafting (MIDCAB) is the quality and long-term patency of the graft and anastomosis. Intra and postoperative quality assessment is important to confirm the safety and effectiveness of minimally invasive techniques. Methods: From January to December 1998 MIDCAB was performed in 246 patients using a limited minithoracotomy for single left anterior descending artery (LAD) revascularization. According to our standard protocol quality assessment of the graft and anastomosis consisted of intraoperative flow measurement, early postoperative angiography and follow-up angiography after 6 months. Results: Intraoperative flow measurement was performed in patients with anastomoses unsuitable for coronary probing (75/246, mean flow of 34.3±17.7 ml/min). Early patency was confirmed by intraoperative monoplane angiogram in 37/246 (15.0%) patients and by postoperative multiplan angiography in 205/246 (83.3%). Early patency rate was 98.0%. Six months follow-up showed a patency rate of 97.5% (one occluded graft, two severe and two moderate stenoses at the anastomotic site). Eighty-nine percent of the patients were in a CCS angina class I, 11% in class II, respectively. Six months mortality was 0.8%. Re-intervention had to be performed in 5/116 (4.3%). Conclusions: A standardized protocol for quality assessment is mandatory for MIDCAB surgery. The proposed algorithm serves to ensure the safety and effectiveness of this new technique. Our recent series document an excellent outcome of the MIDCAB approach. Postoperative multiplan angiography is the only technique to achieve valid information about the quality of graft and anastomosis.
Key Words: Quality assessment in CABG • MIDCAB • Coronary probe • Transit time flow measurement • Coronary angiography
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1. Introduction
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Minimally invasive direct coronary artery bypass grafting (MIDCAB) reduces invasiveness by a limited access and the avoidance of cardiopulmonary bypass in single left anterior descending artery (LAD) coronary artery revascularization, but success of this treatment grafting is directly related to the quality and long-term patency of the conduit and the anastomosis [1,2]. Quality assessment in MIDCAB surgery has to answer two major questions: (1) is MIDCAB safe; and (2) is it effective in terms of the long-term benefit.
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2. Materials and methods
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In 1998 246 patients underwent MIDCAB surgery without using cardiopulmonary bypass (CPB). All patients were operated through a small left antero-lateral minithoracotomy. The MIDCAB technique has been described in detail elsewhere [3,4]. In brief: a minithoracotomy was performed through the 4th intercostal space and ITA-graft was harvested under direct vision. Heparin was applied at a dosage of 100 IU/kg. Temporary occlusion of the target coronary artery was achieved by proximal and distal 4/0 monofile suture- snares supported by a piece of pericardium. Local immobilization of the anastomosis was achieved using a variety of stabilizers. The anastomosis was performed using a single running 8/0 polypropylene suture, starting at the heel. Protamin was applied to neutralize 80% of the heparin dosage.
The standardized protocol for quality assessment consisted of the following algorithm.
- 1. Probing of both the tip and the toe of the anastomosis using a 1 mm coronary probe before completion of the anastomosis.
- 2. If probing could not be performed (limited access, fragile vessel), transit time flow measurement was used.
- 3. In case of a transit time flow below 15 ml/min, intraoperative monoplane angiography was performed.
- 4. All patients underwent early postoperative multiplane angiography and 6 months follow-up angiography.
2.1 Techniques of intraoperative quality assessment
Transit time flow measurement was performed using flow probes (2 or 3 mm) (Cardio-Med Flowmeter CM 4000, Medi-Stim, Oslo Norway).
Intraoperative monoplane angiography was performed using a mobile digital angiography unit (Series 9600 OEC, Salt Lake City, UT) via femoral access, using a 5 Fr ITA angiography catheter (Medtronic-CascadeTM, Minneapolis, MN).
Postoperative multiplane angiography was performed in the cathlab (Siemens, Munich, Germany) between POD 2 and POD 5.
At follow-up, classification of angina was evaluated according to the Canadian Cardiovascular Society (CCS). A follow-up angiogram was performed as described above.
Data of this prospective study are presented as mean±standard deviation (SD) or percentage of the whole group.
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3. Results
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According to the protocol outlined above, flow measurement was performed using the transit time method in 75/246 patients (30.5%). Mean flow was 34.3%±17.7 ml/min. In 37 patients flow was less than 15 ml/min. In these patients an intraoperative monoplane angiogram was performed to confirm the patency of the anastomosis. In two of these patients (2/37, 5.4%) low bypass flow was documented and subsequently intraoperative revision of the anastomosis was performed. The remaining patients showed good run off and a patent anastomosis. Two-hundred and five patients of 246 (83.3%) underwent postoperative angiography between POD 2 and POD 5 (31 patients did not consent to the angiographic study). Two grafts (2/205, 1.0%) were occluded, four grafts (1.9%) showed a severe stenosis (>75%) at the anastomotic site, and four grafts (1.9%) had a minor to moderate stenosis (20–75%). Currently, 6 months follow-up angiograms are available in 116 of the 246 patients. One patient showed an occluded graft (0.9%), 4/116 patients (3.4%) showed a severe stenosis >75% and another 2/116 patients (1.7%) a minor to moderate stenosis (20–75%). As a result 94.0% of the patients showed a patent anastomosis free from stenosis at 6 months after surgery. Five re-interventions had to be performed, two early postoperatively (redo) and another after 3 months (PTCA). Consequently the 6 months freedom from re-intervention was 95.7% in that group.
In 1998 there was no hospital deaths, but 2/246 patients (0.8%) died during follow-up of unknown causes. The preoperative diagnosis, results of the early and follow-up angiography, and the clinical follow-up data are depicted in Tables 1–3
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4. Discussion
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The patient's perspective in the treatment of coronary artery disease with isolated LAD lesion could be defined as follows: small or no incision, no pain, early postoperative recovery with a short period of hospitalization, and a long-term success without multiple re-interventions. PTCA may be attractive since it covers the first four of these perspectives, but it does not cover the latter two since long-term benefit is not guarantied and re-interventions are necessary in 15–30% during the first few months depending on the grade and morphology of the LAD lesion [5,6]. The MIDCAB approach may overcome this disadvantage by providing the well known long-term patency rate of ITA to LAD bypass grafts combined with little trauma. However, to demonstrate the superiority of MIDCAB compared to PTCA two major questions have to be answered. First, is MIDCAB safe despite its nature of a life threatening microsurgical procedure on the moving target? and second, does it provide improved long-term patency? Apart from these principal issues another concern has to be refuted: is it guaranteed that the excellent outcome of MIDCAB reported by some authors [7–10] is reproducible for a huge number of cardiovascular centers? This issue is of major importance, since PTCA is a standardized treatment with a reliable outcome.
To confirm the benefit of minimally invasive coronary artery bypass grafting a multi-center data base with a standardized quality assessment is necessary to ensure the reproducibility of results of different cardiovascular centers as well as to evaluate the benefit of competing treatments. Consequently the data collection should include patient selection, perioperative data and a follow-up of at least 6 months. The quality of the conduit and the anastomosis is the most important determinant for the success of the procedure. Therefore intraoperative, postoperative and follow-up evaluation are equally important. For an intraoperative quality assessment flow measurement is possible using the transit time method. Several authors have shown, that the information about a positive run off is reliable, but that the detection of moderate or even severe stenosis at the anastomotic site is difficult to achieve and moreover false negative results are possible [11,12]. Thus it may be difficult to draw the right intraoperative decision on the basis of transit time measurement only. In case of a reduced graft flow of less than 15 ml/min or absence of diastolic flow our strategy is to perform an intraoperative angiography. However, the information which can be achieved by this technique is rather sufficient to confirm the correct anastomosis at the target vessel and an unobstructed distal run off, than reflecting real quality of the anastomosis. Even moderate stenosis, spasm or very short stenosis, usually localized at the heel of the anastomoses, may not be detected by this method. Thus, a further postoperative angiography is necessary to get the complete information about the quality of graft and anastomosis (Fig. 1).
On the basis of our data from all 246 patients operated in 1998 we may answer two of the former raised questions. First, MIDCAB is a safe procedure as demonstrated by the low incidence of perioperative complications. This is also true in patients having multiple vessel coronary artery disease without other target vessels to bypass than the LAD and for patients with severely reduced left ventricular function. Second, the early and 6-months patency rate confirm the equal quality of MIDCAB grafting as compared with the results of conventional surgical techniques and yield more favorable results than those that can be achieved with PTCA. Nevertheless, there is a small number of patients showing stenosis at the anastomotic site or even within the conduit. On the basis of a comparison between early and 6-months angiograms we found that about 25% of the early stenoses may disappear (Fig. 2), but also new stenoses may appear during the postoperative period. Early re-intervention may not be necessary if there is no decreased run off on the postoperative angiogram and no ischemia under stress conditions (ECG or nuclear scan), but a reangiogram after 6 months is mandatory as it is for PTCA. Fig. 3
shows the currently used algorithm of treatment in patients having postoperative graft stenosis.
MIDCAB grafting is an alternative treatment for coronary artery disease especially in patients with a single LAD lesion. The procedure is less invasive as compared to conventional CABG with equal patency rates [13,14]. Compared to PTCA both the patency rate as well as less need of additional intervention are in favor of the MIDCAB approach [15]. However, it has to be stressed that MIDCAB is not a simple, rather a more challenging surgical procedure. Due to the modalities of sophisticated minimally invasive techniques careful patient selection, meticulous surgical techniques and comprehensive quality assessment is required to definitely place MIDCAB between PTCA and conventional CABG with reproducible long-term results.
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Footnotes
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Presented at the International Symposium ‘Present State of Minimally Invasive Cardiac Surgery – Meet the Experts', Dresden, Germany, December 3– 5, 1998.
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References
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Abstract
1. Introduction
