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Eur J Cardiothorac Surg 2006;30:567
© 2006 Elsevier Science NL

Letter to the Editor

Reply to Kargar and Aazami

Massimo Lemma*, Carlo Antona

Division of Cardiovascular Surgery, Cardio-Nephro-Vascular Department, Luigi Sacco Hospital, Via Grassi 74, 20157 Milan, Italy

Received 29 May 2006; accepted 1 June 2006.

* Corresponding author at: Minimally Invasive Cardiac Surgery Unit, Cardio-Nephro-Vascular Department, Luigi Sacco Hospital, Via Grassi 74, 20157 Milan, Italy. Tel.: +39 0239042333; fax: +39 0239042652. (Email: m.lemma{at}hsacco.it; c.antona{at}hsacco.it).

Key Words: Composite arterial graft • CABG • Myocardial revascularization • Thoracic artery • Radial artery

We thank Kargar and Aazami [1] for their interest in our recent article on flow dynamics and wall shear stress (WSS) in the left internal thoracic artery (LITA) [2]. In this study we show that the LITA has a marked adaptability to flow dynamics with a clear propension to adequate WSS and cross-sectional area to flow requirements. Two modifications take place into proximal LITA used as a composite Y-graft: (1) a ‘passive’ increase in blood flow due to the lower resistance of the parallel vascular circuit represented by the Y-graft, as expressed by the Kirchoff's 2nd law, and (2) an ‘active’ increase of proximal LITA diameter related to the higher average peak velocity and blood flow that stimulate the synthetic and secretory functions of endothelial cells, modulating the production of nitric oxide and endothelin-1 to obtain proximal LITA dilatation. Finally also the flow pattern could have a role in the production of vasoactive substances by vascular endothelial cells, presenting the proximal part of LITA Y-graft a diastolic-predominant peak of flow velocity, probably related to the reduced vascular resistance of the parallel vascular circuit. In conclusion our study shows that in composite Y-graft the proximal LITA is able to actively adapt its dimension to the flow demand, probably through the release of endothelial vasoactive mediators, consequence of higher values of WSS. This process of adaptation begins immediately after the operation because of the passive increase of blood flow due to the lower vascular resistance of the Y-graft system.

Kargar and Aazami seem to be skeptical about the adaptability of the LITA to increased myocardial blood flow requirements. However we have shown that soon after the operation the LITA used as a Y-graft can significantly increase blood flow in response to conditions of increased MVO2, keeping normal the O2 supply-to-demand ratio. We obtained these data measuring blood flow in Y-graft both at rest and during atrial pacing at the 85% of the patient age-predicted maximum, considering the heart rate-systolic blood pressure product an indirect index of MVO2 [3].

Both the afore mentioned functional data and the favourable clinical results coming from LITA used as a Y-graft [4] should comfort Kargar and Azami about the safety and afficacy of the LITA in Y-graft configuration.

We thank again Kargar and Aazami for their interest in our paper.

References

  1. Kargar F, Aazami M. Y-graft and proximal LIMA flow adaptability: the surgical wisdom of iatrogenics. Eur J Cardiothorac Surg 2006;30(3):566.[Free Full Text]
  2. Lemma M, Innorta A, Pettinari M, Mangini A, Gelpi G, Piccaluga M, Danna P, Antona C. Flow dynamics and wall shear stress in the left internal thoracic artery: composite arterial graft versus single graft. Eur J Cardiothorac Surg 2006;29:473-478.[Abstract/Free Full Text]
  3. Lemma M, Mangini A, Gelpi G, Innorta A, Danna P, Lavarra F, Piccaluga E, Antona C. Effects of heart rate on phasic Y-graft blood flow and flow reserve in patients with complete arterial myocardial revascularization: an intravascular Doppler catether study. Eur J Cardiothorac Surg 2003;24:81-85.[Abstract/Free Full Text]
  4. Lemma M, Mangini A, Gelpi G, Innorta A, Spina A, Antona A. Is it better to use the radial artery as a composite graft? Clinical and angiographic results of aorto-coronary versus Y-grat. Eur J Cardiothorac Surg 2004;26(1):110-117.[Abstract/Free Full Text]




This Article
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Massimo Lemma
Carlo Antona
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Right arrow Articles by Lemma, M.
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Related Collections
Right arrow Cardiac - physiology
Right arrow Coronary disease

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