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Ann Thorac Surg 2003;76:1339-1340
© 2003 The Society of Thoracic Surgeons

Correspondence

Are composite Y-grafts able to fully respond to the left coronary system flow demand early after coronary bypass graft?

Massimo Lemma, MD, Andrea Mangini, MD, Guido Gelpi, MD, Andrea Innorta, MD, Amedeo Spina, MD, Carlo Antona, MD

Department of Cardiovascular Surgery, "L. Sacco" Hospital, Milan, Italy

To the Editor:

We read with great interest the paper by Sakaguchi and colleagues [1]. The authors retrospectively compared the coronary flow reserve (FR) and the regional myocardial blood flow after coronary artery bypass grafting using arterial composite Y-grafts (22 patients) or independent arterial grafts (13 patients). The authors studied their patients 2 weeks after the operation at rest with positron emission tomography. Dipyridamole was used to get maximal hyperemic blood flow. Although regional baseline myocardial blood flow did not differ between the two groups, the coronary FR in the Y-graft group was significantly lower in the anterobasal, apical, septal, and lateral regions. In their comment, the authors state that "the composite Y-graft is unable to fully respond to the flow demand of the whole left coronary system early after coronary artery bypass graft," and conclude that "the indications for Y-graft should be carefully reviewed, especially in the case of a small left internal thoracic artery."

Our experience is different. We have recently reported at the 16th annual meeting of EACTS [2] a series of 27 patients who underwent complete arterial myocardial revascularization using the left internal thoracic artery (LITA) and the radial artery (RA) as Y-graft. These patients underwent predischarge coronary angiography and intravascular flow velocity measurements using a Doppler guide-wire. Hyperemic flow was determined by adenosine injection. In our study protocol, the patient heart rate was increased by atrial pacing up to 85% of the patient age-predicted maximum, significantly increasing myocardial oxygen consumption (MVO2). No patient complained of chest pain or developed ischemic S-T segment modification, perioperative conditions characterized by moderate anemia and microvasculature dysfunction due to the recent surgical trauma [3]. Both these factors reduce the FR in the early postoperative period. The LITA main stem could maintain a normal O2 supply-to-demand ratio during maximal increase of MVO2 caused by atrial pacing. Hyperemic flow in sinus rhythm was significantly greater than baseline flow during atrial pacing in the LITA main stem. This datum confirms previous experimental results showing that the entire coronary reserve is not used during peak muscular exercise [3]. As a consequence, the vasodilatation induced by physiological stimuli does not appear to be as complete as that induced by pharmacological stimuli.

In conclusion, our experience differs from that of Sakaguchi and colleagues in that a Y-graft is able to fully respond to the flow demand of the whole coronary system early after coronary artery bypass grafting and also shows that a Y-graft can maintain a normal O2 supply-to-demand ratio even during maximal increase of MVO2 induced by atrial pacing.

References

  1. Sakaguchi G., Tadamura E., Ohnaka M., Tambara K., Nishimura K., Komeda M. Composite arterial Y graft has less coronary flow reserve than independent grafts. Ann Thorac Surg 2002;74:493-496.[Abstract/Free Full Text]
  2. Lemma M, Mangini A, Gelpi G, et al. Effects of heart rate on phasic Y-graft blood flow and flow reserve in patients with complete arterial myocardial revascularization: an intravascular Doppler catheter study. Presented at the 16th Annual Meeting of the European Association for Cardio-Thoracic Surgery. Monaco, September 22–25, 2002
  3. Barnard R.J., Duncan H.W., Livesay J.J., Bucberg G.D. Coronary vasodilatory reserve and flow distribution during near maximal exercise in dogs. J Appl Physiol 1977;43:988-992.[Free Full Text]




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Andrea Mangini
Guido Gelpi
Carlo Antona
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