We read the article by Tufekci et al.[1] with a great interest. We believe that we may have some contribution to this study. As this study revealed, the intracoronary shunt is only found to be effective on vessels with stenosis, rather than occluded ones. This is why the intracoronary shunt is used commonly on vessels with some degree of stenosis in our daily practice. The use of shunt on totally occluded vessel is not, indeed, necessary. In this study by Tufekci et al.,[1] we believe that group 3 and 4, which included totally occluded vessels, are not essentially needed in the study design. The authors also found no significant difference between these groups in their study.

Off-pump coronary artery bypass grafting (CABG) has many favorable effects on inflammatory parameters, compared to on-pump procedures, as this fact was repeatedly shown in many studies.[2] Although offpump CABG is not entirely safe, it can still induce inflammation as theoretically explained with ischemiareperfusion injury in myocardium after revascularization of occluded vessels. It is also reasonable to assume that the intracoronary shunt can improve reperfusion injuries on myocardium after revascularization of stenotic vessels, since it allows continuous flow during anastomosis. Is this a potential benefit of the intracoronary shunt?

We would like to highlight another common technical mistake as well. Indeed, this mistake is very common in numerous studies. It is the timing of tests for ischemia parameters postoperatively. As Tufekci et al. suggested in their study, the troponin levels were checked on 24^th hour postoperatively after ischemia. On the other hand, troponin levels start to elevate on 2-4^th hour after an ischemic event and reach to peak levels at 12^th hour, and start to subside to normalize within a week.[3-5] Hence, is not it reasonable to test for the troponin levels on the 12th hour after ischemia? We are looking forward to hearing authors’ opinions on this issue.

Declaration of conflicting interests
The authors declared no conflicts of interest with respect to the authorship and/or publication of this article.

Funding
The authors received no financial support for the research and/or authorship of this article.

REFERENCES
1. Tüfekçi N, Bozok S, Aslan C, İlhan G, Karakişi SO, Ergene S, et al. A prospective study on indication of intracoronary shunt during off-pump coronary bypass grafting surgery for single-vessel disease. Turk Gogus Kalp Dama 2016;24:34-9.

2. Bicer M, Senturk T, Yanar M, Tutuncu A, Oral AY, Ulukaya E, et al. Effects of off-pump versus on-pump coronary artery bypass grafting: apoptosis, inflammation, and oxidative stress. Heart Surg Forum 2014;17:E271-6.

3. Zacharowski K, Otto M, Hafner G, Marsh HC, Thiemermann C. Reduction of myocardial infarct size with sCR1sLe(x), an alternatively glycosylated form of human soluble complement receptor type 1 (sCR1), possessing sialyl Lewis x. British Journal of Pharmacology 1999;128:945-52.

4. Jaffe AS. The clinical impact of the universal diagnosis of myocardial infarction. Clin Chem Lab Med 2008;46:1485-8.

5. Csonka C, Kupai K, Kocsis GF, Novák G, Fekete V, Bencsik P, et al. Measurement of myocardial infarct size in preclinical studies. J Pharmacol Toxicol Methods 2010;61:163-70.

Author Reply
Dear Editor,

We are grateful for the contribution entitled “Use of intracoronary shunt” made for our article entitled “A prospective study on indication of intracoronary shunt during off-pump coronary bypass grafting surgery for single-vessel disease.”[1]

Intracoronary shunts were found to be beneficial during off-pump coronary artery bypass grafting (OPCABG) operations in patients with an isolated left anterior descending (LAD) coronary artery lesion.[2] In his experimental study, Dapunt et al.[3] reported that intra-LAD shunt insertion remarkably preserved the myocardial energy stores compared to LAD occlusion and suggested that intracoronary shunt insertion improved the protection of myocardium during offpump revascularization. Similar findings have been also reported by Gurbuz et al.[4] and Bozok et al.[5] The protective effect of the intracoronary shunt on myocardium demonstrated by these studies may constitute a basis for its usage in OPCABG surgery.[3-5] Patients with total occlusion may not be the ideal candidates for the intracoronary shunt. However, attributed to the potential benefits documented in relevant publications, we used intracoronary shunts in groups 3 and 4 in our study.[2-5]

Repetitive measurements of cardiac markers may probably allow a better assessment of their postoperative release. Sadony et al.[6] reported that a cardiac troponin I value at 24^th hour had a sensitivity of 100% and a specificity of 97% for the discrimination of patients with and without perioperative myocardial infarction. Thus, we evaluated troponin levels at 24 hours following the intervention.

REFERENCES
1. Tüfekçi N, Bozok S, Aslan C, İlhan G, Karakişi SO, Ergene S, et al. A prospective study on indication of intracoronary shunt during off-pump coronary bypass grafting surgery for single-vessel disease. Turk Gogus Kalp Dama 2016;24:34-9.

2. Lucchetti V, Capasso F, Caputo M, Grimaldi G, Capece M, Brando G, et al. Intracoronary shunt prevents left ventricular function impairment during beating heart coronary revascularization. Eur J Cardiothorac Surg 1999;15:255-9.

3. Dapunt OE, Raji MR, Jeschkeit S, Dhein S, Kuhn-Regnier F, Sudkamp M, et al. Intracoronary shunt insertion prevents myocardial stunning in a juvenile porcine MIDCAB model absent of coronary artery disease. Eur J Cardiothorac Surg 1999;15:173-9.

4. Gürbüz A, Emrecan B, Yılık L, Özsöyler I, Kestelli M, Özbek C, et al. Intracoronary shunt reduces postoperative troponin leaks: a prospective randomized study. Eur J Cardiothorac Surg 2006;29:186-9.

5. Bozok S, Ilhan G, Karamustafa H, Ozan Karakisi S, Tufekci N, Tomak Y, et al. Influence of intracoronary shunt on myocardial ishemic injury during off-pump coronary artery bypass surgery. J Cardiovasc Surg (Torino) 2013;54:289-95.

6. Sadony V, Körber M, Albes G, Podtschaske V, Etgen T, Trösken, et al. Cardiac troponin I plasma levels for diagnosis and quantitation of perioperative myocardial damage in patients undergoing coronary artery bypass surgery. Eur J Cardiothorac Surg 1998;13:57-65.

Correspondence: Şahin Bozok, MD. Department of Cardiovascular Surgery, Bahcesehir University, BAU International University Batumi, International University Hospital Batumi, Batumi, Georgia.

Tel: +90 533 - 236 24 42 e-mail: sahinboz@yahoo.com