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Aortic valve surgery after previous coronary artery bypass grafting with functioning internal mammary artery grafts
John G Byrne1, Alexandros N Karavas, Farzan Filsoufi
1Division of Cardiac Surgery, Brigham & Women's Hospital, Boston, Massachusetts 02115, USA. jbyrne@partners.org
Insights
Aortic valve surgery after bypass grafting with patent internal mammary artery (IMA) grafts is safe when the IMA is left undissected. Moderate-to-deep hypothermia protects the heart during aortic clamping (AoX).
Area of Science:
- Cardiovascular Surgery
- Cardiac Surgery
- Thoracic Surgery
Background:
- Aortic valve surgery after coronary artery bypass grafting (CABG) with patent internal mammary artery (IMA) grafts presents significant risks.
- Traditional IMA management involves dissection and clamping, potentially increasing surgical complexity.
- An alternative strategy of leaving the IMA undissected during aortic clamping (AoX) requires evaluation.
Purpose of the Study:
- To evaluate the safety and efficacy of leaving the IMA undissected during aortic valve surgery in patients with patent grafts.
- To assess the outcomes of this alternative strategy compared to traditional methods.
Main Methods:
- Analysis of 94 patients undergoing aortic valve surgery with patent IMA grafts between 1992 and 2001.
- IMA was left undissected and open during AoX, with systemic cooling to a median of 20°C.
- Patients' demographics, surgical details, and outcomes were analyzed for predictors of mortality and morbidity.
Main Results:
- Operative mortality was 6.4%, perioperative myocardial infarction (MI) was 7%, and stroke rate was 11%.
- No independent predictors for operative mortality or MI were identified; urgent procedures and extensive aortic surgery trended towards higher mortality.
- Advanced age and prolonged cardiopulmonary bypass were predictors of stroke; five IMA injuries (5%) occurred, none in minimally invasive cases.
Conclusions:
- Leaving the IMA undissected and unclamped is a viable strategy for aortic valve surgery in patients with patent grafts.
- Systemic cooling is crucial for myocardial protection, preventing regional warming and compensating for cardioplegia washout during AoX.
- This approach offers a reasonable alternative for managing high-risk patients undergoing aortic valve surgery post-CABG.
Background:
Aortic valve surgery after coronary artery bypass grafting (CABG) in the setting of patent pedicled internal mammary artery (IMA) grafts poses a high risk because of the underlying ischemic and valve disease. Unlike mitral valve surgery or CABG, in which aortic clamping (AoX) may be optional, aortic valve surgery uniformly requires AoX unless circulatory arrest is used. Management of the IMA graft in these circumstances has traditionally involved dissection and clamping to prevent regional myocardial warming and cardioplegia "washout" during AoX. An alternative strategy involves avoiding dissection of the IMA, leaving the IMA graft open and establishing moderate-to-deep hypothermia during AoX and cardioplegic arrest. To date, no study has been published documenting the safety and efficacy of the latter practice.
Methods:
A total of 94 patients who had patent IMA graft and underwent aortic valve surgery under AoX and cardioplegia between April 1992 and March 2001 were analyzed. The IMA was avoided and left open during AoX, and the patients were cooled systemically (median 20 degrees C). Patients ranged in age from 55 to 90 years (median 73.5 years). Ejection fraction was 15% to 83% (median 50%). Of the patients, 18 (19%) underwent minimally invasive upper hemi-resternotomy. Analysis for predictors of outcome was performed.
Results:
The operative mortality, perioperative myocardial infarction (MI), and stroke rates were 6.4%, 7%, and 11%, respectively. No significant independent predictors of operative mortality or MI could be identified in the multivariate analysis, although a trend was shown for operative mortality with urgent procedures and patients requiring concomitant surgery of the ascending or arch aorta or aortic root. Advanced age and prolonged cardiopulmonary bypass predicted stroke in the multivariate analysis. There were five (5%) IMA injuries, all occurring during reentry or mediastinal dissection, but none in the subgroup of patients who underwent minimally invasive procedures. All patients survived.
Conclusions:
Patients undergoing aortic valve surgery after CABG in the presence of patent IMA represent a potentially high-risk group. Because AoX is almost uniformly required, a decision regarding the management of the IMA pedicle is needed. We have found that leaving the IMA undissected and unclamped is a reasonable strategy, provided that systemic cooling for myocardial protection is established to prevent regional warming and to compensate for cardioplegia washout effect during AoX.