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Relationship between echocardiographic index of ventricular filling pressure and intraoperative haem
- Young Lan Kwak, JK Shim, YS Choi (7 April 2009)
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Diastolic dysfunction and OPCAB
- Mark E Edsell (1 April 2009)
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Young Lan Kwak , JK Shim, YS Choi
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Dear Editor, we thank Dr. Edsell for his constructive comments on our manuscript. As he pointed out, increasing age and hypertension are well known risk factors of diastolic dysfunction. The cause of diastolic dysfunction with age is largely unknown, but it is most likely that the age-related changes in the ventricle’s passive elastic properties cause decrease in the rate of ventricular relaxation [1]. Similar mechanism can also be applied in patients with hypertension. Therefore, it is not surprising that older patients having hypertension would have greater incidence of diastolic dysfunction manifested as elevated E/e’ since e’ reflects the rate of myocardial relaxation. Thus, possibilities exist that these two variables could be confounders. However, no statistical significance was reached with regard to these variables between the groups, and the ventricular wall thicknesses during diastole between the groups were also similar (posterior wall 9.6 [1.4] mm vs. 10 [1.6] mm, p = 0.430, interventricular septum 9.8 [1.4] mm vs. 10.2 [2.0] mm, p = 0.407, in the E/e’ < 8 and > 15 group, respectively). Furthermore, none of the studies addressing the risk factors for haemodynamic deterioration and conversion to cardiopulmonary bypass during off-pump coronary bypass surgery have identified age or hypertension as risk factors [2-4], and we feel that the results of our study clearly validate the prognostic importance of E/e’ in terms of intraoperative haemodynamic changes during off-pump coronary bypass surgery. As to the use of greater amount of norepinephrine in the E/e’ >15 group and the possible association with antihypertensive medications and decreased cardiac index, our answers are as follows. The numbers of patients taking antihypertensive medications were all similar, especially with regard to the angiotensin converting enzyme inhibitor which is associated with increased hypotensive episodes during anaesthesia then the beta blockers or calcium channel blockers [5]. Moreover, greater amount of norepinephrine in the E/e’ >15 group was used during grafting of left circumflex artery (64 [56] µg vs. 29 [29] µg, p = 0.016) and right coronary artery (58 [36] µg vs. 20 [27] µg, p = 0.019) and after sternum closure (28 [46] µg vs. 8 [20] µg, p = 0.049). Before that the amount used was similar between the groups and thus the association with antihypertensive medication should be negligible. Also, norepinephrine was used to maintain the mean arterial pressure between 70-80 mmHg, which should have minimal effects on wall tension, thus on decrease in cardiac index. We hope that our answers and additional data will clarify the questions raised by Dr. Edsell and hope that our study can draw many interests regarding this area. Jae Kwang Shim MD, Yong Seon Choi MD, Young Lan Kwak MD. References 1. Downes TR, Nomeir AM, Smith KM, Stewart KP, Little WC. Mechanisms of altered pattern of left ventricular filling with aging in subjects without cardiac disease. Am J Cardiol 1989;64:523-7. 2. Mishra M, Shrivastava S, Dhar A, et al. A prospective evaluation of hemodynamic instability during off-pump coronary artery bypass surgery. J Cardiothorac Vasc Anesth 2003;17:452-8. 3. Jin R, Hiratzka LF, Grunkemeier GL, Krause A, Page US. Aborted off-pump coronary artery bypass patients have much worse outcomes than on-pump or successful off-pump patients. Circulation 2005;112[suppl I]:I-332-7. 4. Edgerton JR, Dewey TM, Magee MJ, et al. Conversion in off-pump coronary artery bypass grafting: an analysis of predictors and outcomes. Ann Thorac Surg 2003;76:1138-43. 5. Comfere T, Sprung J, Kumar MM, et al. Angiotensin system inhibitors in a general surgical population. Anesth Analg 2005;100:636-44. Conflict of Interest:None declared |
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Mark E Edsell, Anaesthetist St George's Hospital
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Editor I would like to thank Shim and colleagues for their interesting paper exploring the relationship between diastolic dysfunction and haemodynamic derangement during off-pump coronary bypass surgery (OPCAB)1. However, there are some important differences between the groups that I feel should have been discussed. The E/e’ group tended to be older (66 verses 62) with a greater incidence of hypertension (13 of 25 verses 19 of 25 patients). Perhaps unsurprisingly therefore they were also more likely to be on antihypertensive medications. Whilst, in isolation, none of these differences reached statistical significance, they may have made the groups behave clinically different. The E/e’ group received a significantly greater amount of Norepinephrine (p=0.029). This may, in part have been influenced by preoperative antihypertensive medication and not diastolic dysfunction. In addition, Norepinephrine itself can cause a decrease in cardiac output. The paper rightly highlights the importance of diastolic dysfunction in OPCAB but a discussion of these potential confounders should have been included. Dr Mark Edsell. St George’s Hospital, London References 1. Shim JK, Choi YS, Chun DH, Hong SW, Kim DH and Kwak YL. Relationship between echocardiographic index of ventricular filling and intraoperative haemodynamic changes during off-pump coronary bypass surgery. BJA 2009; 102 (3): 316-21 Conflict of Interest:None declared |
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