Author + information
- Milan Milojevic, MD, MSc,
- Stuart J. Head, MD, PhD and
- David R. Holmes Jr., MD∗ ()
- ↵∗Cardiovascular Diseases and Internal Medicine, Mayo Clinic, 200 First Street Southwest, Rochester, Minnesota 55905
We thank Dr. Nappi and colleagues for their observations and comments on our cause-of-death report from the SYNTAX (Synergy Between Percutaneous Coronary Intervention With Taxus and Cardiac Surgery) trial (1). They raise some important points.
First, certainly, a well-functioning left internal mammary artery graft to the left anterior descending coronary artery improves survival in patients with multivessel disease and is an established tenant of practice. As they suggest, there are different reasons for this, including prevention of anterior myocardial infarctions (MI), which tend to be associated with mortality and morbidity; hence, the finding that MI-related deaths were significantly lower after coronary artery bypass grafting (CABG) than after percutaneous coronary intervention (PCI) in our paper (1).
Second, evaluation of completeness of revascularization continues to be a moving target. Originally, it was a surgical concept, and subsequently, it has been applied in the field of interventional cardiology. In contrast to CABG, patients with multivessel disease treated with PCI have less chance of being completely revascularized. As shown in one of our publications originating from the SYNTAX data (2), this is particularly true in patients with chronic total occlusion or diffusely diseased small distal vessels, which can be successfully treated with CABG but often not with PCI. Despite this, even CABG patients with very small distal vessels risk receiving only incomplete revascularization.
Third, the impact of incomplete revascularization is much debated. Although it is clear that incomplete revascularization with PCI causes a higher risk of adverse events including death, during follow-up, the negative impact of incomplete revascularization with CABG is less well defined. A related issue that needs to be considered is the degree of ischemia or viable myocardium subtended by the vessel (usually a chronic total occlusion) in question. The degree of incomplete revascularization reported in the studies by Genereux et al. (3) and Farooq et al. (4) is a crucial factor with PCI. With larger areas of myocardium at risk, the risk of myocardial infarction and its associated prognosis is proportionately related. This could be the result of the severity and extent of residual ischemia and the specific impact of completeness of revascularization, which are related but not identical. The higher SYNTAX revascularization index (SRI), while not specifically studied in our current cause-of-death report, continues to make sense for populations of patients in that reducing the total amount of ischemia should confer improved prognosis. It may not, however, affect the specific cause of the death. There are individuals who, by virtue of their anatomy, benefit from targeted revascularization, and that remains a very valid concept in patients with extensive disease and previous myocardial infarctions. With CABG, incomplete revascularization was often present because distal vessels were too small to graft (2), which also means that the area of myocardium at risk was small, limiting the clinical impact.
Fourth, generally, the benefit of CABG over PCI is particularly evident by the prevention of MI and subsequently death, as shown in our report (1). Although the excretion of nitric oxide by arterial grafts is an interesting phenomenon, we believe that there is no substantial evidence to support abandoning one of the largest benefits of CABG derived from the secondary preventive feature of bypass surgery in bypassing potential future lesions. To rely on enough nitric oxide secretion for angiogenesis to ischemic areas would be a premature and risky assumption.
The issues of cause of death and completeness of revascularization still need further study, identifying the cause of death, whether from congestive heart failure, lethal ventricular arrhythmia, or acute MI, so that eventually we can continue to refine the concept of patient-specific therapeutic strategies.
Please note: The authors have reported that they have no relationships relevant to the contents of this paper to disclose. David J. Moliterno, MD, served as Guest Editor for this paper.
- American College of Cardiology Foundation
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