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Do Different Techniques of Left Internal Mammary Graft Harvesting Really Affect Hospital Outcome?
Ann Thorac Surg 2008;86:1052–1060
1. Odell JA. Coronary artery bypass grafting after previous stenting is associated with compromised long-term efficacy (letter). Ann Thorac Surg 2008; 86:1052. 2. Rao C, Stanbridge RL, Chikwe J, et al. Does previous percutaneous coronary stenting compromise the long-term efficacy of subsequent coronary artery bypass surgery? A microsimulation study. Ann Thorac Surg 2008; 85:501–7. 3. Tovar EA, Blau N, Borsari A, Landa DW, Packer JM. Severe deformity of a Palmaz-Schatz stent after normal surgical manipulation. Ann Thorac Surg 1997; 63:220 –1. 4. Tovar EA, Borsari A. Effects of surgical manipulation on coronary stents: should surgical strategy be altered? Ann Thorac Surg 1997; 63:37– 40. 5. Thielmann M, Leyh R, Massoudy P, et al. Prognostic significance of multiple previous percutaneous coronary interventions in patients undergoing elective coronary artery bypass surgery. Circulation 2006; 114(1 Suppl):I441–7. 6. Thielmann M, Neuhauser M, Knipp S, et al. Prognostic impact of previous percutaneous coronary intervention in patients with diabetes mellitus and triple-vessel disease undergoing coronary artery bypass surgery. J Thorac Cardiovasc Surg 2007; 134:470 – 6.
Do Different Techniques of Left Internal Mammary Graft Harvesting Really Affect Hospital Outcome? To the Editor: We read with great interest the article by Onorati and colleagues [1], who tried to analyze transit-time flow and in-hospital results of pedicled vs skeletonized left internal mammary artery (LIMA) in first-time myocardial revascularization. Although we are impressed with the results, we ponder over a few queries that arise in our minds. Because the study is based on the comparison between pedicled vs skeletonized LIMA, the study needs to be designed such that the myocardial territory nourished by the left anterior descending artery (presumably to which all LIMAs have been anastomosed) can be evaluated. On the other hand, an average of more than 3 anastomoses were performed in each patient; therefore, it does not seem reasonable to attribute the rise of troponin I to the LIMA, because this may equally be related to any of other bypass grafts. This is also true regarding the 5 patients with perioperative myocardial infarction. In the scope of the higher rate of venous graft occlusion compared with the LIMA, the doubt in the conclusion of this study becomes even more meaningful. Even in the echocardiographic studies, we would recommend evaluation of the anterior and septal myocardium if the LIMA flow were to be evaluated. Abnormal wall motion in these sections of the heart would be a more acceptable guide to the patency of the LIMA in the two groups of patients. It is noted that nitric oxide, as the active component of nitrovasodilators such as nitroglycerin, induces vasodilation through the activation of soluble guanylate cyclase in the vascular smooth muscle. Also, a normally functioning endothelium inhibits platelet aggregation and adhesion by negative feedback secondary to platelet-derived adenosine diphosphate-stimulated nitric oxide production. Impairment of nitric oxide production by the traumatized endothelium might be expected to interrupt the protective feedback, and platelet aggregation and adhesion could occur [2]. It is already and accurately mentioned in the Comment section of the article that “different pathologic studies show a © 2008 by The Society of Thoracic Surgeons Published by Elsevier Inc
1053
tendency for skeletonized grafts to contain a larger number of lesions in the endothelium, microscopic intimal dissection and detachment, and injuries to the external elastic lamina . . . .” [1]. We think, however, this may not affect free flow measurements immediately at the time of surgery. Because of the close relation between endothelial integrity and nitric oxide production, any vessel wall injury will have a strong effect on early and late postoperative LIMA patency, and normal operative pulsation and a free conduit flow does not exclude this unpleasant result. Because this excellent article is evaluating a very important issue, with its results and conclusions crucial to the strategic planning of the coronary artery bypass grafting surgery by cardiac surgeons, we recommend consideration of all aspects of such study designs. Hopefully, by overcoming all study limitations, a satisfactory guideline may be proposed. Mahnoosh Foroughi, MD Seyed-Ahmad Hassantash, MD Manoochehr Hekmat, MD Aliasghar Bolourian, MD Mehran Shahzamani, MD Zahra Ansari, MD Department of Cardiac Surgery Modarres Hospital Saadat-Abad Tehran, Iran e-mail: [email protected]
References 1. Onorati F, Esposito A, Pezzo F, di Virgilio F, Mastroroberto P, Renzulli A. Hospital outcome analysis after different techniques of left internal mammary grafts harvesting. Ann Thorac Surg 2007;84:1912–9. 2. Pearson PJ, Evora PRB, Seccombe JF, Schaff HV. Hypomagnesemia inhibits nitric oxide release from coronary endothelium: Protective role of magnesium infusion after cardiac operations. Ann Thorac Surg 1998;65:967–72.
Reply To the Editor: We would like to thank Foroughi and colleagues [1] for their discussion and stimulating comments. We agree that more focused evaluation between pedicled or skeletonized left internal mammary artery (LIMA) grafts should be related to endpoints that directly refer to the conduit itself or to the downstream myocardium. Anterolateral myocardial kinetics reflect LIMA to left anterior descending coronary artery (LAD) function. Perioperative troponins relate to both the effectiveness of myocardial revascularization and the quality of myocardial protection. However, when hospital outcomes are considered enzymatic leakage, myocardial functional recovery and the incidence of perioperative acute myocardial infarction (AMI) must be considered. Moreover, collateral circulation in patients undergoing three-vessel revascularization [2] may mask graft malfunction in the territory supplied by the graft. The potential for remote perioperative AMI exists in patients with LIMA to LAD graft failure and a well-developed collateral circulation [2]. However, when wall motion score indices (WMSI) were calculated for the nine segments nourished by the LAD, our postoperative echocardiographic results were comparable between the two groups: 0003-4975/08/$34.00
MISCELLANEOUS
References
CORRESPONDENCE
1. Odell JA. Coronary artery bypass grafting after previous stenting is associated with compromised long-term efficacy (letter). Ann Thorac Surg 2008; 86:1052. 2. Rao C, Stanbridge RL, Chikwe J, et al. Does previous percutaneous coronary stenting compromise the long-term efficacy of subsequent coronary artery bypass surgery? A microsimulation study. Ann Thorac Surg 2008; 85:501–7. 3. Tovar EA, Blau N, Borsari A, Landa DW, Packer JM. Severe deformity of a Palmaz-Schatz stent after normal surgical manipulation. Ann Thorac Surg 1997; 63:220 –1. 4. Tovar EA, Borsari A. Effects of surgical manipulation on coronary stents: should surgical strategy be altered? Ann Thorac Surg 1997; 63:37– 40. 5. Thielmann M, Leyh R, Massoudy P, et al. Prognostic significance of multiple previous percutaneous coronary interventions in patients undergoing elective coronary artery bypass surgery. Circulation 2006; 114(1 Suppl):I441–7. 6. Thielmann M, Neuhauser M, Knipp S, et al. Prognostic impact of previous percutaneous coronary intervention in patients with diabetes mellitus and triple-vessel disease undergoing coronary artery bypass surgery. J Thorac Cardiovasc Surg 2007; 134:470 – 6.
Do Different Techniques of Left Internal Mammary Graft Harvesting Really Affect Hospital Outcome? To the Editor: We read with great interest the article by Onorati and colleagues [1], who tried to analyze transit-time flow and in-hospital results of pedicled vs skeletonized left internal mammary artery (LIMA) in first-time myocardial revascularization. Although we are impressed with the results, we ponder over a few queries that arise in our minds. Because the study is based on the comparison between pedicled vs skeletonized LIMA, the study needs to be designed such that the myocardial territory nourished by the left anterior descending artery (presumably to which all LIMAs have been anastomosed) can be evaluated. On the other hand, an average of more than 3 anastomoses were performed in each patient; therefore, it does not seem reasonable to attribute the rise of troponin I to the LIMA, because this may equally be related to any of other bypass grafts. This is also true regarding the 5 patients with perioperative myocardial infarction. In the scope of the higher rate of venous graft occlusion compared with the LIMA, the doubt in the conclusion of this study becomes even more meaningful. Even in the echocardiographic studies, we would recommend evaluation of the anterior and septal myocardium if the LIMA flow were to be evaluated. Abnormal wall motion in these sections of the heart would be a more acceptable guide to the patency of the LIMA in the two groups of patients. It is noted that nitric oxide, as the active component of nitrovasodilators such as nitroglycerin, induces vasodilation through the activation of soluble guanylate cyclase in the vascular smooth muscle. Also, a normally functioning endothelium inhibits platelet aggregation and adhesion by negative feedback secondary to platelet-derived adenosine diphosphate-stimulated nitric oxide production. Impairment of nitric oxide production by the traumatized endothelium might be expected to interrupt the protective feedback, and platelet aggregation and adhesion could occur [2]. It is already and accurately mentioned in the Comment section of the article that “different pathologic studies show a © 2008 by The Society of Thoracic Surgeons Published by Elsevier Inc
1053
tendency for skeletonized grafts to contain a larger number of lesions in the endothelium, microscopic intimal dissection and detachment, and injuries to the external elastic lamina . . . .” [1]. We think, however, this may not affect free flow measurements immediately at the time of surgery. Because of the close relation between endothelial integrity and nitric oxide production, any vessel wall injury will have a strong effect on early and late postoperative LIMA patency, and normal operative pulsation and a free conduit flow does not exclude this unpleasant result. Because this excellent article is evaluating a very important issue, with its results and conclusions crucial to the strategic planning of the coronary artery bypass grafting surgery by cardiac surgeons, we recommend consideration of all aspects of such study designs. Hopefully, by overcoming all study limitations, a satisfactory guideline may be proposed. Mahnoosh Foroughi, MD Seyed-Ahmad Hassantash, MD Manoochehr Hekmat, MD Aliasghar Bolourian, MD Mehran Shahzamani, MD Zahra Ansari, MD Department of Cardiac Surgery Modarres Hospital Saadat-Abad Tehran, Iran e-mail: [email protected]
References 1. Onorati F, Esposito A, Pezzo F, di Virgilio F, Mastroroberto P, Renzulli A. Hospital outcome analysis after different techniques of left internal mammary grafts harvesting. Ann Thorac Surg 2007;84:1912–9. 2. Pearson PJ, Evora PRB, Seccombe JF, Schaff HV. Hypomagnesemia inhibits nitric oxide release from coronary endothelium: Protective role of magnesium infusion after cardiac operations. Ann Thorac Surg 1998;65:967–72.
Reply To the Editor: We would like to thank Foroughi and colleagues [1] for their discussion and stimulating comments. We agree that more focused evaluation between pedicled or skeletonized left internal mammary artery (LIMA) grafts should be related to endpoints that directly refer to the conduit itself or to the downstream myocardium. Anterolateral myocardial kinetics reflect LIMA to left anterior descending coronary artery (LAD) function. Perioperative troponins relate to both the effectiveness of myocardial revascularization and the quality of myocardial protection. However, when hospital outcomes are considered enzymatic leakage, myocardial functional recovery and the incidence of perioperative acute myocardial infarction (AMI) must be considered. Moreover, collateral circulation in patients undergoing three-vessel revascularization [2] may mask graft malfunction in the territory supplied by the graft. The potential for remote perioperative AMI exists in patients with LIMA to LAD graft failure and a well-developed collateral circulation [2]. However, when wall motion score indices (WMSI) were calculated for the nine segments nourished by the LAD, our postoperative echocardiographic results were comparable between the two groups: 0003-4975/08/$34.00
MISCELLANEOUS
References
CORRESPONDENCE