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Ann Thorac Surg 2005;79:511-516
© 2005 The Society of Thoracic Surgeons

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Original article: Cardiovascular

Impact of Concomitant Coronary Artery Bypass Grafting on Hospital Survival After Aortic Root Replacement

Division of Cardiac Surgery, Brigham and Women's Hospital, Boston, Massachusetts

Accepted for publication July 19, 2004.

^* Address reprint requests to Dr Byrne, Division of Cardiac Surgery, Brigham and Women's Hospital, 75 Francis St, Boston, MA 02115 (E-mail: jbyrne{at}partners.org).

	Abstract

Top Abstract Introduction Patients and Methods Results Comment References

 
BACKGROUND: We examined the impact of concomitant coronary artery bypass grafting (CABG) on hospital survival after aortic root replacement. We sought to determine whether CABG procedures that were not originally planned but rather added after the aortic root procedure was completed (CABG/bailout) skewed the results to shift patients with bad outcomes to the CABG group, making the non-CABG group appear undeservedly low risk.

METHODS: Between May 1992 and January 2001, 369 consecutive patients underwent aortic root replacement. Concomitant CABG was required in 95 patients (26%). Indications for CABG were significant coronary artery disease in 73 patients (20%), active endocarditis or acute aortic dissection involving the coronary orifices in 14 patients (4%), and difficulty weaning from bypass because of regional wall motion abnormality from presumed but unconfirmed coronary artery disease or technical error at coronary ostial reimplantation (CABG/bailout) in 8 patients (2%).

RESULTS: Operative mortality for the entire cohort was 5.7% (21 patients). The operative mortality rate for the non-CABG group was 0.4% (1 of 274 patients), and for the CABG group, 21% (20 of 95 patients; p < 0.001). Independent predictors of operative mortality in the CABG group were New York Heart Association functional class III or IV (odds ratio, 3.9; 95% confidence interval, 1.07 to 14.5), active endocarditis (odds ratio, 9.2; 95% confidence interval, 2.06 to 41.5), acute aortic dissection (odds ratio, 7.6; 95% confidence interval, 1.81 to 32.0), and failure to use retrograde cardioplegia (odds ratio, 6.4; 95% confidence interval, 1.06 to 38.8). The use of CABG/bailout was not a predictor.

CONCLUSIONS: Adding CABG at the end of an aortic root procedure is a rare event, and because it is rare, there is no significant shift of risk as a result of the CABG/bailout patients on the overall CABG group.

	Introduction

Top Abstract Introduction Patients and Methods Results Comment References

 
Several previous reports have recorded the evolution of aortic root surgery [1]. Postoperative morbidity and mortality have decreased substantially with advances in operative technique and perioperative care. Among those patients undergoing aortic root surgery, concomitant coronary artery bypass grafting (CABG) is often deemed necessary. Concomitant CABG has been shown to increase operative risk [2]. Indications include the presence of known coronary artery disease (CAD) or the destruction of the coronary ostia by endocarditis or aortic dissection. Furthermore, in some patients, CABG is deemed necessary after the aortic root procedure is completed. This can be as a result of a technical error in the coronary button anastomosis or because of regional wall motion abnormalities after separating from bypass from suspected but unconfirmed CAD or myocardial protection error. These are patients who, although not initially planned for CABG, cross over to the CABG group (CABG/bailout). No studies have reported the effect that these patients may have on the postoperative morbidity and mortality of the CABG group.

	Patients and Methods

Top Abstract Introduction Patients and Methods Results Comment References

 
Patients
Between May 1992 and January 2001, 369 consecutive patients underwent aortic root surgery at the Brigham and Women's Hospital. After approval by the institutional review board, medical records were reviewed.

Median age was 51 years (range, 19 to 90 years), and 108 patients (29%) were female. Ejection fraction ranged between 0.15 and 0.85 (median, 0.60), and 145 patients (39%) had New York Heart Association functional class III or IV symptoms. Aortic valve regurgitation was evident on presentation in 199 patients (54%), aortic stenosis in 84 patients (23%), mixed regurgitation and stenosis in 36 patients (10%), and other pathologic processes (endocarditis, dissection) in 50 patients (14%). One hundred patients (27%) presented urgently or emergently, and 24 patients (7%) were in cardiogenic shock. Sixty-three patients (17%) had undergone previous cardiac surgery, and 48 patients (13%) had undergone previous valve surgery.

Incisions and Myocardial Protection
The majority of patients (308 patients, 83%) were approached by means of a full sternotomy, whereas 56 patients (15%) underwent upper hemisternotomy, 2 patients (0.5%) were approached through a right parasternal incision, and 3 patients (0.8%) through a right thoracotomy incision.

Myocardial protection techniques, based on surgeon preference, were accomplished with topical and systemic hypothermia (median, 25°C; range, 11°–37°C), as well as 4:1 cardioplegia (CP), which was delivered antegrade only in 51 patients (14%), retrograde only in 17 patients (5%), and both antegrade and retrograde in 298 patients (81%). One patient (0.3%) did not receive CP and the myocardium was protected solely by systemic hypothermia.

Concomitant Coronary Artery Bypass Grafting
Patients undergoing concomitant CABG (95 patients, 26%) were divided into three subsets on the basis of the indication for coronary revascularization (Fig 1). The CAD group (73 patients, 20%; CABG/CAD group) included 66 patients with significant CAD, confirmed by preoperative coronary angiography, plus 7 patients who had known or suspected CAD that was not confirmed angiographically immediately before surgery owing to the urgent status of the procedure. In these 7 patients, revascularization was performed on the basis of inspection and palpation. In the CABG/CAD group, there were 21 of 73 patients (29%) who also had either active endocarditis or acute aortic dissection.

View larger version (38K): [in this window] [in a new window]   Fig 1. The operative mortality (OM) rate for the entire non–coronary artery bypass grafting (CABG) group (top right) was 0.4% (1 of 274 patients), whereas the operative mortality rate for the entire CABG group (bottom right) was 21% (20 of 95 patients; p < 0.001). The operative mortality rate for the CABG/coronary artery disease group (bottom left, gray) was 19% (14 of 73 patients), for the CABG/coronary orifice group (bottom left, white) was 29% (4 of 14 patients), and for the CABG/bailout group (middle of figure) was 25% (2 of 8 patients). The operative mortality rate in patients initially planned for CABG (patients in the CABG/coronary artery disease group plus the CABG/coronary orifice group) versus those not planned for CABG (patients in non-CABG group plus the CABG/bailout group), remained significant (3 of 282 patients, 1%; versus 18 of 87 patients, 20%; p < 0.01).

In both the CABG/CAD and CABG/coronary orifice groups (87 patients, 24%), an anatomic obstruction was present and known before commencing the root replacement procedure. Thus, the CABG procedure was planned in these 87 patients. In contrast to these patients, another 8 patients (2%) required CABG after completion of the root procedure secondary to ventricular dysfunction or bleeding from the coronary button(s) during weaning from bypass (CABG/bailout group). In these 8 patients, CABG was not deemed necessary until after the aortic root procedure was performed. These were patients with regional wall motion abnormalities and therefore suspected but unconfirmed CAD (n = 3), or a torn or edematous right coronary artery ostium resulting in ventricular dysfunction or bleeding, requiring ligation of the right coronary artery ostia and placement of a CABG to the right coronary artery (n = 5).

Statistics
Statistical analysis was performed using STATA 6.0 Intercooled (College Station, TX). The Fisher's exact test and Mann-Whitney U test were used for the univariate analysis of dichotomous and continuous independent variables, respectively. Multivariate analysis was performed using logistic regression. Inclusion criterion was p less than or equal to 0.200; however, the clinical significance of each variable was taken into consideration before inclusion or exclusion from the multivariate analysis. The Appendix summarizes the variables used in the logistic regression analysis. All statistical analyses were performed at a level of = 0.05, one-sided for mortality and myocardial infarction (MI) and two-sided for all other observations. The one-sided analysis was used for mortality and MI to avoid using variables that promoted survival or MI.

	Results

Top Abstract Introduction Patients and Methods Results Comment References

 
Pathologic Findings and Implantation Techniques
Pathologic findings were annuloaortic ectasia in 102 patients (28%), aortic valve calcification in 91 patients (25%), bicuspid or congenital deformation of the aortic valve (AV) in 61 patients (17%), active endocarditis in 44 patients (12%), and acute type A dissection in 40 patients (11%). Thirty-one patients (8%) had other pathologic findings. Thirty-one patients (8%) had the clinical manifestations of Marfan's syndrome, 1 patient (0.3%) had Ehlers-Danlos syndrome, and another 1 patient (0.3%) had hereditary telangiectasia. Two patients (0.5%) had findings consistent with cystic medial necrosis, and 1 patient (0.3%) had giant cell aortitis.

Full root replacement was performed in 356 patients (96%) patients, hemiroot in 10 patients (3%), and valve-sparing root replacement in 3 patients (0.8%). The Ross procedure was performed in 42 patients (11%), and 2 patients (0.5%) received a stented biologic valve sutured into a separate aortic tube graft. One hundred fifty-eight patients (43%) received a homograft, 28 patients (8%) received a Freestyle stentless xenograft, and 136 patients (37%) received a mechanical valved conduit. Aortic valve prosthesis diameter ranged between 19 and 31 mm (median, 24 mm).

Of the 356 full root replacements, the button technique was used for both coronaries in 270 of 356 patients (76%), whereas in 86 of 356 patients (23%) deviations from this technique were required secondary to CAD or the inability to directly reimplant one or both coronary arteries (Table 1). The 2 patients in whom neither coronary button reimplantation nor CABG was performed are the same 2 patients as the 2 Cabrol technique patients. The use of mechanical valved conduits decreased in favor of homografts and stentless xenografts throughout the study period: mechanical conduits were used in 48% in the period between 1992 and 1996 versus 30% in the period between 1997 and 2001 (p < 0.001).

Operative Characteristics
Median CPB time was 181 minutes (range, 92 to 561 minutes), and in 111 patients (30%) it was longer than 220 minutes. Median aortic cross-clamp time was 137 minutes (range, 27 to 442 minutes), and in 104 patients (28%) it was longer than 160 minutes. Durations of CPB and aortic cross-clamping of 220 and 160 minutes, respectively, were chosen because they each represented the 75th percentile of those measurements for the entire cohort. Circulatory arrest was required in 71 patients (19%), and this ranged between 4 and 125 minutes (median, 29 minutes). In the majority of circulatory arrest patients, based on surgeon preference, cerebral protection consisted of systemic hypothermia and retrograde cerebral perfusion. There was no relationship between circulatory arrest and perioperative stroke. Aprotinin was used in 86 patients (23%).

Operative Mortality
Overall operative mortality (OM; defined as in-hospital death or death within 30 days of surgery) was 21 patients (5.7%). Etiology-specific OM rate varied: active endocarditis and acute dissection were associated with the highest OM rate. Thirteen of 21 patients (62%) died of myocardial failure, 2 of 21 patients (10%) after postoperative cardiac arrest, and 3 of 21 patients (14%) owing to multisystem organ failure. Other causes of death included hemorrhage (n = 1), embolic stroke (n = 1), and sepsis (n = 1).

The two groups of patients—the CABG group (95 patients, 26%) and the non-CABG group (274 patients, 74%)—were inhomogeneous in terms of preoperative (age, status) and intraoperative (associated arch aneurysms, temperature on CPB, route of CP, duration of aortic cross-clamping and CPB, and utilization of circulatory arrest) characteristics (Table 2).

Because of the extremely low mortality rate in the non-CABG group (0.4%, n = 1) as well as the entire cohort (5.7%, n = 21), multivariate analysis for predictors of OM was performed only on the CABG group. Univariate analysis in the CABG group revealed associations with urgent procedures, New York Heart Association functional class III or IV (but not ejection fraction), reoperations, acute type aortic A dissection, active endocarditis, failure to use retrograde CP, CPB duration greater than 220 minutes, and perioperative MI (Table 3). In the CABG group, all patients who underwent surgery for active endocarditis or acute type A aortic dissection and who failed to receive retrograde cardioplegia (n = 4 of 35 patients) died (OM rate, 100% versus 73%; p = 0.03).

	Comment

Top Abstract Introduction Patients and Methods Results Comment References

In our series, overall OM rate was 5.7%, and the majority of these deaths were attributed to cardiac causes, as previously reported [1, 2, 5–11]. Our non-CABG patients (n = 274) revealed an OM rate of 0.4%, which was lower than the 3.6% to 4.3% mortality reported by the US registries for isolated aortic valve replacement [12, 13]. Conversely, our data, and those of previous studies [1, 2, 14], document that patients requiring concomitant CABG had significantly greater OM and perioperative morbidity rates, thus constituting a very high-risk group. Thus, the CABG group represents a multiple-morbidity, high-risk group in which the need for CABG represents a surrogate for multiple comorbidities. In this study, the CABG/bailout group included 8 patients who were not initially planned for CABG but in whom intraoperative complications arose from technical error in the coronary button anastomosis or regional myocardial dysfunction and suspected but unconfirmed CAD mandating "blind" use of CABG. Had CABG/bailout been a more common occurrence, there is little doubt that its effect on our OM rate would have been more significant. Thus, this study, with only 8 patients in the CABG/bailout group, is underpowered to rule out type II error.

Another important finding was that CABG/coronary orifice anatomy, that is the need to perform CABG because of destruction of the native coronary orifices owing to endocarditis or acute aortic dissection, was associated with very high OM rate (29%). In these patients, it is likely that acute myocardial ischemia is ongoing as a result of malperfusion of the coronary arteries. Had the CABG/coronary orifice anatomy been a more common occurrence, it too would have had a more profound influence on overall OM rate. In such patient with coronary malperfusion, myocardial protection becomes even more important.

We have previously documented the importance of myocardial protection in aortic valve and root surgery [15, 16]. The present study showed that failure to use retrograde CP in the CABG group significantly increased the perioperative MI and OM rates. Significant CAD has already been shown to result in inhomogeneous and inadequate distribution of CP when delivered antegrade only [17, 18]. Our study documents that this is also important in patients with compromised coronary flow owing to acute aortic dissection or endocarditis involving the coronary arteries as well as in patients who require CABG as a result of technical error in the coronary button anastomosis or suspected but unconfirmed CAD. Although the protective effects of retrograde CP were seen only in the CABG group and cannot be extended to aortic root replacement in which concomitant CABG is not needed, our results indicate that retrograde CP should be strongly considered when CABG is anticipated. However, this strategy may help minimize the risks in patients in whom coronary angiography is unavailable before surgery owing to acute aortic dissection or active endocarditis.

Perioperative MI was significantly more common in the CABG group (30% versus 8%), which helps explain why the MI rate for the entire cohort was 11%. When MI did occur, it was strongly associated with operative death: of the 28 patients in the CABG group who sustained MI, 12 patients (43%) died. In the univariate analysis, concomitant mitral valve surgery was associated with MI, but this could not be confirmed in the multivariate analysis, probably because of the relative small number of patients. We do not believe any mitral valve patients sustained injury to the circumflex coronary artery, but this cannot be confirmed.

The other predictors of mortality in our study (New York Heart Association class III or IV, acute aortic dissection, and active endocarditis) have been previously described [1, 2, 5–7, 9, 11], but these are less amenable to modification once the patient has presented to the operating room.

	Appendix

 
Variables Used for Predicting Hospital Mortality
Active endocarditis

Acute aortic dissection

Age more than 65 years

Aortic cross-clamp time > 160 minutes

Aprotinin used

Arch aneurysm

Coronary artery bypass grafting/bailout

Coronary artery bypass grafting/coronary orifice

Circulatory arrest

Concomitant coronary artery bypass grafting (all subgroups)

Concomitant mitral valve surgery

Cardiopulmonary bypass temperature < 25°C

Cardiopulmonary bypass > 220 minutes

Cardioplegia antegrade only

Cardioplegia Retrograde or Both
Ejection fraction 0.35

Failure to use retrograde cardioplegia

Myocardial infarction

Nonsinus rhythm

New York Heart Association functional class III or IV

Postoperative bleeding

Reoperation

Respiratory insufficiency

Reoperation for bleeding

Stroke

Urgent or emergent operation

	References

Top Abstract Introduction Patients and Methods Results Comment References

 

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): John G. Byrne Alexandros N. Karavas Marzia Leacche Daniel Unic James D. Rawn Gregory S. Couper Tomislav Mihaljevic Robert J. Rizzo Sary F. Aranki Lawrence H. Cohn Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Byrne, J. G. Articles by Cohn, L. H. Search for Related Content PubMed PubMed Citation Articles by Byrne, J. G. Articles by Cohn, L. H. Related Collections Valve disease