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Interact CardioVasc Thorac Surg 2009;8:49-53. doi:10.1510/icvts.2008.185280 © 2009 European Association of Cardio-Thoracic Surgery
Factors affecting post minimally invasive direct coronary artery bypass grafting incidence of myocardial infarction, percutaneous transluminal coronary angioplasty, coronary artery bypass grafting and mortality of cardiac origin
a Department of Cardiac, Thoracic and Vascular Surgery, National University Hospital, National University of Singapore, 5 Lower Kent Ridge Road, Level 2, 119074 Singapore Received 3 June 2008; received in revised form 26 August 2008; accepted 27 August 2008
*Corresponding author. Tel.: +65 6772 2065; fax: +65 6776 6475.
In the present study we identify parameters which influence the incidence of myocardial infarction (MI), need for percutaneous coronary intervention (PCI), coronary artery bypass grafting (CABG) and cardiac mortality after minimal invasive coronary artery bypass grafting (MIDCABG). With a mean follow-up of 30±11.2 months, 390 patients were assessed with Wald test-corrected  2 analysis to identify preoperative factors which correlate with a higher incidence of post-MIDCABG MI, PCI, CABG and mortality from cardiac causes. We found an increased incidence of postoperative MI in patients with 2-vessel (8.7%) and 3-vessel (7.7%) vs. 1.3% 1-vessel coronary artery disease (CAD) (P=0.023), and in patients with preceding cardiac procedure (CABG and PCI: 8.4% vs. 2.0% without, P=0.023). Also diabetes was associated with higher post-MIDCABG frequency of MI (P=0.035). Severity of angina was associated with lesser post-MIDCAB-PCI (P=0.011) while preceding CABG predicted a higher incidence (P=0.012). Preoperative low ejection fraction (EF) (multivariate, P<0.001), preoperative MI (P=0.007) and extent of CAD (P=0.001) were associated with a higher post-MIDCABG mortality. None of the parameters correlated with subsequent CABG MIDCABG. The extent and history of CAD, history of cardiac interventions and low EF seem to influence the outcome adversely and should be considered deciding pro or against the MIDCAB-option.
Key Words: Coronary disease; Procedures; Minimally invasive surgical; Predictive factors; Follow-up
The demand for a less invasive access in coronary surgery resulted in the introduction of the minimal invasive coronary bypass grafting (MIDCABG) procedure in the late 1970s, first published in the early 1980s [1, 2]. In the meanwhile this technique is ubiquitously well established and primarily indicated in patients with proximal one-vessel disease [3]. Alternatively it is utilized in two-vessel coronary disease in coordination with angioplasty or stenting in the non-LAD vessel, which is not accessible through the mini-thoracotomy. The latter is known as hybrid revascularization approach [4, 5]. Most recently, the multi-vessel small thoracotomy bypass procedure (MVST) using suction devices for heart stabilization further expanded the indication spectrum for the minimal access cardiac surgery. This way, the LAD plus a lateral major coronary vessel can be supplied. Despite the wide acceptance of the procedure in high volume centers, decision-making as to whether it is indicated or not in selected patients is not based upon commonly approved criteria or predictive factors. Singular reports of the impact of comorbidities on the outcome of the procedure are present but rare [6–8]. In view of an appreciable conversion rate, considerable postoperative pain, intraoperative ischemia and not complete revascularization in some cases, it is mandatory to evaluate the impact of conditions, such as low ejection fraction (EF), extent of the coronary disease or reported myocardial infarctions and preceding cardiac procedures on the postoperative outcome following MIDCABG. Furthermore, a more analytical view of preoperative demographic data in a given single population may assist in delineating predictors of adverse postoperative outcomes. The present work evaluates the correlation of such parameters with adverse postoperative events, such as postoperative myocardial infarction, mortality of cardiac origin and the need for PCI and CABG operation, which largely define postoperative quality of life and may retrospectively help stipulate borderline indications.
This is a retrospective follow-up study encompassing 390 patients who had been operated in our department of Cardiac, Thoracic and Vascular Surgery, in Hannover, from 1996 through 2001. The follow-up encompassed the time from 1996 to 2004. A questionnaire was sent to the patient's attending physicians. We were able to collect information (partially incomplete) from 342 of 390 patients. The remaining 48 patients could not be reached and must be considered lost to follow-up. Mean follow-up time was 30±11.2 months. In the original population of 269 male (69%) and 121 female (31%); mean age at the time of operation was 61.6±10.4 years (32–85 years). Inclusion criteria were MIDCABG procedure to revascularize the LAD, or the first or second diagonal branch, or sequentially the LAD and one of the diagonals. Isolated LAD disease was present in 253 of 390 patients (64.9%). Two-vessel disease was present in 91 patients (23.3%), and 3-vessel disease was found in 46 patients (11.8%). In 62 cases (15.9%) the LAD was totally occluded, in 76 patients (19.5%) the stenosis was severe (90–99%), in 157 cases (40.3%) the coronary stenosis was moderate (76–90%), and in 95 patients (24.4%) the stenosis was of lower degree (51–75%). The indication for MIDCABG in patients with 2- and 3-vessel disease was given if: a) the stenosis of the second and third vessels were not significant (clinically silent and <50%), b) their localization was far too distal and thereof dependent myocardium was either scarred or aneurysmatic, c) the second and third coronary targets were severely and globally calcified and of a <1 mm diameter, and d) an operation using cardiopulmonary bypass (CPB) appeared too risky, due to extensive comorbidities. Exclusion criteria from this retrospective study were a) indication for off-pump coronary artery bypass grafting through a median sternotomy and b) planned hybrid procedure. The questionnaire we used inquired for myocardial infarction, subsequent procedures performed (CABG or PCI), and death from cardiac cause. For the description of the operative technique we refer the reader to previous work [7]. The following parameters were evaluated to find potential correlations to the aforementioned cardiac-related events: Gender, age at operation, extent of coronary disease, left ventricular ejection fraction (EF), degree of LAD-stenosis, preceding myocardial infarction, preceding cardiac operation or PCI, intensity of preoperative pectoral angina, and comorbidities such as hypertension, diabetes, hyperlipidemia, renal failure. The degree of target coronary stenosis was classified as follows: non-relevant (<50%), mild stenosis (51–75%), moderate stenosis (76–90%), severe stenosis (90–99%) and occlusion (100%). The preoperative EF was classified as follows: normal or slightly reduced (50%), moderately reduced (30–49%), and severely reduced (<30%). Descriptive statistics are presented as mean±S.D. For covariate analysis of the impact of a preoperative condition on the need for post-MIDCABG PCI, CABG, postoperative cardiac mortality and myocardial infarction the2-test was utilized. Following proof of significance in frequency of events in dichotomized groups, logistic regression analysis was used to access the presence of a relation between pre- and post-MIDCABG conditions. The statistical evaluation was performed using the SPSS 11.0 software and statistical significance was assumed at P<0.05.
3.1. Post-MIDCABG myocardial infarction (Table 1) The incidence of postoperative myocardial infarction correlated with the severity of the diagnosed CAD disease (P=0.023). Only 1.3% patients (3/222) with a single-vessel CAD suffered a postoperative myocardial infarction, compared to 8.7% (7/80) and 7.7% (3/40) of patients with 2- or 3-vessel CAD. Further, a cardiac procedure (CABG and PCI: 8.4% vs. 2.0% without, P=0.023), prior to the MIDCABG operation also correlated with a higher incidence of post-MIDCABG myocardial infarction (P=0.023). Here, 8.4% (7/89) of patients with a preceding CABG or PCI procedure suffered a most-MIDCABG myocardial infarction, as opposed to only 2.0% (5/253) of patients where MIDCABG was a first-time cardiac procedure (no CABG or PCI preceded the MIDCAB procedure). Finally, diabetes patients showed a trend for higher incidence of post-MIDCABG myocardial infarction (P=0.035, only in univariate analysis).
3.2. Post-MIDCABG need for PCI (Table 2) PCI was carried out in 23 patients following MIDCABG, in most cases as a consequence of the native CAD of the patient (8x LAD, 1x first diagonal branch, 14x unrelated territories such as OMs and the right coronary artery). In only two cases the PCI was necessary due to operation-related reasons: one anastomotic stenosis and a case of dissection of the internal thoracic artery (LITA). The necessity for postoperative PCI was more frequent in patients with pre-MIDCABG severe angina (P=0.011). Patients with a CCS class of 1 before the MIDCABG operation required post-MIDCABG PCI in 25% of the cases (3/12 patients) vs. 11.2% in patients with CCS class 2 (11/101 patients), 5.4% in patients with CCS class 3 (9/167 patients) and 3.4% in patients with CCS class 4 (2/60 patients). Further, preceding CABG also correlated with more frequent demand for post-MIDCABG-PCI (P=0.012). In 22.2% of patients (18/82 patients) with preceding CABG a PCI became necessary post-MIDCABG, vs. in 6.8% (18/260 patients) of patients without preceding CABG. Finally, there was a trend for patients with a low EF (EF <49%) to need PCI more frequently following the MIDCABG procedure. This finding was significant in the univariate analysis (P=0.047) but not in the multivariate one.
3.3. Post-MIDCABG mortality of cardiac cause (Table 3) There were seven postoperative deaths related to cardiac etiology (2.1%). The most prominent impact factor over postoperative mortality of cardiac cause was a low EF (moderately and severely reduced, <50%) prior to the MIDCABG procedure: 28.6% (3/14 patients) of patients with a severely reduced EF (<30%), vs. 10% (3/30 patients) of patients with a moderate EF reduction, and only 0.3% (1/308 patients) of patients with a normal pre-MIDCABG EF died postoperatively from a cardiac cause (extensive infarction or fatal arrhythmia). Also the severity of CAD (P=0.001) disease and preceding myocardial infarction (P=0.007) indicated an influence on the occurrence of postoperative mortality from cardiac causes. However, this could not be confirmed in the multivariate analysis.
3.4. Post-MIDCABG necessity for a CABG procedure (in the observed follow-up period of almost 1000 patient-years) None of the studied preoperative conditions correlated with a high incidence of postoperative necessity for a CABG procedure, at a mean of 30.0±11.2 months following MIDCABG.
The main finding of our retrospective study is that a low ejection fraction correlates with a higher incidence of death from cardiac causes following MIDCABG. This incidence seems to vary with the severity of preoperative EF reduction. Also, postoperative myocardial infarction seems to be more frequent in patients with more severe CAD and those with preceding cardiac procedures, prior to MIDCABG. Furthermore, the need for post-MIDCABG-PCI is more frequent in patients with preceding cardiac procedures and those with less severe angina, prior to the operation. From these findings one could conclude that MIDCABG may not be the preferred option for high-risk patients, or patients with advanced coronary disease and positive history of interventions. On the other hand, none of the evaluated preoperative parameters correlated with an increased frequency of a CABG procedure following the MIDCAB operation. While the MIDCABG procedure is well established and propagated in selected patients, only few MIDCABG studies encompass a postoperative follow-up longer than one year. Biglioli et al. reported on a collective of 64 patients at 25.0±11.4 months, while Calafiore provided a follow-up over 434 patients at an average of 13.5±7.8 months [9, 10]. Maniani et al. presented postoperative patency comparisons between MIDCABG (n=71) and PCI (n=110) – treated patients with an isolated LAD disease [11]. In the latter study, patients with more advanced CAD had a higher incidence of post-MIDCABG myocardial infarction, in compliance with our results, probably as a result of their native coronary artery disease. In other short-term studies, postoperative infarction after MIDCABG rates range between 1% and 5%. Of note, many of these studies were carried out without the use of mechanical stabilization [6, 12–14]. In view of our results, it is crucial to understand that severe CAD and preceding cardiac procedures should eventually be considered a factor of higher post-MIDCABG risk and question the indication for MIDCABG in individual cases. We were also able to confirm the low rate of perioperative reintervention after MIDCABG operation, which was related to the operative technique only in two cases. This is in compliance with most of the studies involving MIDCABG patients, with an exception of that of Calafiore et al. who reported 6%, and attributed this to surgical learning curves. Similar incidence of post-MIDCABG reintervention rates are reported elsewhere. Mariani et al. [11] reported an incidence of 3% PCI, Biglioli et al. 4.7% [9], while Calafiore et al. observed a post-MIDCABG-PCI of only 0.7%. Latter value, however, was derived from shorter follow-up intervals. Preceding CABG also seems to have a negative post-MIDCABG impact, in terms of necessity for PCI. This is to be anticipated in redo patients who naturally present with more advanced or more aggressive CAD. Diegeler et al. have found that stenting yields excellent short-term results with fewer periprocedural adverse events, but surgery is a superior redo strategy with regard to the need for repeated intervention in the target vessel and freedom from angina at six months of follow-up [15]. None of the included preoperative conditions appears to affect the need for postoperative CABG at the given follow-up time. The negative correlation of the history of more severe angina with the postoperative incidence of PCI cannot be explained by the data we obtained from the present population. One may need to break down the severity of angina according to the extension of coronary artery disease. It may also be of importance to discriminate between PCI in the vessel targeted by MIDCABG and those due to the natural progression of disease elsewhere. In our patient population the incidence of postoperative MIDCABG angina – which in fact may implement a post-MIDCABG PCI – was 15.4% at the time of follow-up. Of note, our patients had a more extensive CAD compared to most of the related studies. Pertaining to the post-MIDCABG mortality, Calafiore reported as much as 1.6% due to cardiac causes at 13.5 months following MIDCABG [10]. Despite similarly favorable more long-term results, the mortality from cardiac causes should be now viewed with caution, considering that a moderately or severely reduced EF prior to the procedure may result in much higher mortality rates. Our follow-up study has some limitations. First, not all operated patients could be reached. Second, many of the involved family physicians did not provide a completed questionnaire, even though most of the variables could be assembled. In the long-term follow-up, angiographic control was only possible in 78 patients who consented for the catheterization. It would be more insightful to document the state of disease years after MIDCABG and examine it in relation to the postoperative course, as well as preoperative extent of disease and related history. Our findings suggest that patients with low EF or presence of other risk factors may have an unfavorable outcome following MIDCABG. Also, preceding coronary interventions and severity of CAD may result in higher risk for post-MIDCABG myocardial infarction. These conclusions may prove crucial at decision-making, and would be further enhanced by longer-term follow-up studies.
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Abstract
1. Introduction