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Can an observational case-controlled study assess survival benefits in a group of patients undergoing CABG or medical treatment sufficiently?/Survival of patients with well-developed collaterals undergoing CABG or medical treatment: an observational case-controlled study ...

Dear Editor,

We read with great interest the article by Tatli et al. (1) regarding survival of patients with well-developed collaterals undergoing coronary artery bypass grafting (CABG) or medical treatment. Tatli et al. (1) concluded that there was no significant difference regarding the survival rates in those patients. We admire their work but we have some concerns about the methodology of the study, which may affect the interpretation of the results.

Survival benefit of CABG depends on several variables. Extent of ischemic myocardium on preoperative imaging study is one of those variables. If preoperative functional assessment of patients with chronic totally or sub totally occluded left anterior descending artery (LAD) could be provided, there would be mainly two subsets of patients: patients with predominantly non-viable/infracted LAD territories and patients with predominantly viable/ischemic LAD territories. At this point one can speculate that there is possibility that the patients who refused surgery may be more commonly angina-free patients who also had non-viable/infracted LAD territories and the patients who accepted surgery may be more commonly patients with severe angina who also had viable/ischemic LAD territories. If this assumption is true, there would be a selection bias for CABG and medical therapy groups and this bias may affect survival rates since we know that patients with more severe angina and patients with more severe ischemia benefit most from CABG (2).

Another noteworthy issue is the high rate (approximately 50%) of refusing surgery in the study population. As we know that symptomatic patients have greater tendency to refuse surgical interventions, this situation arouses questions about the symptomatic status of the patients of the study group. It would be informative to mention the preoperative symptomatic status of the patients; more severe symptomatic the patients enjoy improved survival benefit of bypass surgery.

As a result, we believe that survival benefit of any intervention can be discussed by the results of a randomized study, which nullifies effects of selection bias. Such studies are needed to reach a conclusion on this interesting topic.

References

(1.) Tatli E, Aktoz M, Cakar MA, Dogan E, Alkan M, Ozalp B. Survival of patients with well-developed collaterals undergoing CABG or medical treatment: an observational case controlled study. Anadolu Kardiyol Derg 2012; 12: 97-101.

(2.) Morrow DA and Gersh BJ. Coronary artery bypass surgery, Effects on survival. In: Libby P Bonow RO, Zipes DP editors. Braunwald's Heart Disease. 8 ed. Philadelphia: Saunders; 2008. p. 1387-8.

Tugrul Norgaz, Sevket Gorgulu

Department of Cardiology, Faculty of Medicine Acibadem University, Kocaeli-Turkey

Address for Correspondence/Yazisma Adresi: Dr. Tugrul Norgaz Acibadem Universitesi Tip Fakultesi, Kardiyoloji Anabilim Dali, Kocaeli-Turkiye Phone: +90 262 317 41 23 Fax: +90 262 226 80 34 E-mail: tnorgaz@yahoo.com Available Online Date/Cevrimici Yayin Tarihi: 23.05.2012 doi: 10.5152/akd.2012.137

Author's Reply

Dear Editor,

We appreciate the comments of the authors concerning our manuscript "Survival of patients with well-developed collaterals undergoing CABG or medical treatment: An observational case-controlled study" (1).

It is inevitable that presence of extended ischemia will affect the clinical outcomes of revascularization as it is mentioned your statement. However, the patient population in our study have had well protected left ventricular function and more than 50% of this population have had angina which is the sign of viability and ischemia. Therefore, we thought that both of these patients have had similar viability and ischemia. As a right criticism of yours, myocardial perfusion scintigraphy should be done for sign of viability and ischemia in this study.

Performing myocardial perfusion scintigraphy to these patients would made this study more valuable. The presence of angina in both patient groups is in equal ratios. Therefore, we thought that there would be no bias in this respect. We want to thank your valuable criticism.

References

(1.) Tatli E, Aktoz M, Cakar MA, Dogan E, Alkan M, Ozalp B. Survival of patients with well-developed collaterals undergoing CABG or medical treatment: an observational case controlled study. Anadolu Kardiyol Derg 2012; 12: 97-101.

Ersan Tatli

Clinic of Cardiology, Ada Hospital, Sakarya-Turkey

Address for Correspondence/Yazisma Adresi: Dr. Ersan Tatli Ada Hastanesi, Kardiyoloji Klinigi, Sakarya-Turkiye Phone: +90 264 236 20 20 Fax: +90 264 211 16 12 E-mail: ersantatli@yahoo.com Available Online Date/Cevrimici Yayin Tarihi: 23.05.2012
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Title Annotation:Letters to the Editor/Editore Mektuplar
Author:Norgaz, Tugrul; Gorgulu, Sevket
Publication:The Anatolian Journal of Cardiology (Anadolu Kardiyoloji Dergisi)
Article Type:Letter to the editor
Date:Aug 1, 2012
Words:709
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