Ann Thorac Surg 2008;86:2005-2007. doi:10.1016/j.athoracsur.2008.05.012
© 2008 The Society of Thoracic Surgeons
How To Do It
"Directed" Cardioplegia: A New Approach in Myocardial Protection in Left Main Coronary Artery Disease
Ilias A. Kouerinis, MD, PhDa,b,*,
Marina M. Palaiologou, PhDa,
Michalis Argiriou, MDb,
Panagiotis Dedeilias, MDb,
Efstratios Apostolakis, MD, PhDb,
Aikaterini Giannakopoulou, MDa,
George Papadopoulos, MD, PhDa,
Nikolaos Tsilimingas, MD, PhDc
a Department of Cardiac Surgery, Aghia Sophia Hospital, Athens, Greece
b Department of Cardiac Surgery, Evangelismos Hospital, Athens, Greece
c Department of Thoracic and Cardiovascular Surgery, University of Thessalia, Larissa, Greece
Accepted for publication May 5, 2008.
* Address correspondence to Dr Kouerinis, Doukissis Plakentias 46, Athens, 15127, Greece (Email: ikouerinis{at}hotmail.com).
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Abstract
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"Directed cardioplegia" is a novel approach in myocardial protection in which a certain volume of cardioplegic solution is diverted into a severely diseased coronary artery after surgical occlusion of the other main branches that can be accessed by the surgeon. In this way, the surgeon is able to eliminate the cardioplegic steal from a severely stenosed vessel through other less severely diseased and/or patent arteries during the nonselective antegrade administration of cardioplegia and to protect myocardial regions, which are poorly perfused. We performed this new technique in 2 patients with severe left main coronary artery disease with excellent results.
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Introduction
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Myocardial protection is a major issue for patients with left main coronary artery disease who undergo coronary artery bypass graft surgery. Although the optimum route for the administration of cardioplegia in patients with severe coronary disease has been the subject of many publications in the medical literature, there are no published reports on the phenomenon of cardioplegic steal from an obstructed left main coronary artery (LMCA) through a patent right coronary artery (RCA) during antegrade administration of cardioplegia. Therefore, the exact volume of cardioplegic solution, which will actually protect the myocardium of the left ventricle (LV), is unknown.
Herein, we describe our technique in which the myocardium of the LV is protected by diverting the antegrade administration of cardioplegia into the left coronary artery by occluding the RCA with a vessel loop. We performed this new technique in 2 patients with severe left main coronary artery disease with excellent results. The demography of the 2 patients and perioperative data are presented in Table 1.
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Technique
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Before commencing cardiopulmonary bypass, the RCA is identified, and an occluding suture (vessel loop) is placed around its proximal portion and before the origin of the anterior ventricular arteries (Fig 1). It is always necessary to palpate the RCA to ensure that there is no overt evidence of atherosclerosis at the site of transient occlusion. After clamping the aorta, we occlude the RCA and two thirds of total cardioplegic solution is delivered antegrade (phase 1). This solution will be distributed mainly in the myocardium of the LV through the left coronary artery, as well as in the sinoatrial area and the pulmonary cone through the homonymous branches of the RCA (Fig 2). The sinus node artery and cone artery originate proximal to the site of the occlusion, and therefore are not devoid of any flow during this phase. The temporary occlusion of the RCA is then removed by releasing the occluding suture and the remaining one third of the cardioplegic solution is delivered in the standard manner (phase 2). After the completion of the distal anastomosis to a branch of the left coronary artery, the same manipulation can be repeated before starting the next anastomosis. Obviously, when the RCA is temporarily occluded, and the cardioplegic solution is delivered antegrade for a second and any subsequent time, perfusion of the myocardium of the LV is further enhanced because the cardioplegic infusion is also delivered to the myocardium through the graft(s).
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Fig 1. The occluding suture of the right coronary artery (RCA). The only possible drawback of our method is an inadvertent injury to the temporarily occluded artery, but it did not occur in our two cases. (PDA = posterior descending artery.)
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Fig 2. The occlusion of the right coronary artery (RCA) will divert most of the cardioplegic infusion to the left coronary artery, while the remaining solution will perfuse the coronary sinus and the pulmonary cone through the homonymous branches of the RCA (arrows). (LAD = left anterior descending.)
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The ratio of the distributing cardioplegic volume with occluded and released RCA may vary according to the surgeon estimation about the mass ratio between the left and right ventricle. For example, in those hearts in which LV hypertrophy is not significant, the previously mentioned 2:1 perfusion volume-ratio, with occluded and released RCA, will finally result (by adding the cardioplegic volume that perfuses the LV during the phase 2) in an approximate 3:1 LV/right ventricle perfusion volume ratio, which relates with the normal mass ratio between the left and right heart. In those hearts in which LV hypertrophy is significant, the surgeon can change the perfusion volume-ratio with occluded and released RCA to favor the perfusion of the left ventricle.
Before the clamp around the aorta is released, the occluding suture is removed, and the coronary artery bypass graft surgery is continued according to standard practice.
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Comment
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The term "directed cardioplegia" describes the diversion of a certain volume of cardioplegic solution to a severely diseased coronary artery after surgical occlusion of the other main branches that can be accessed by the surgeon.
We performed this new technique on 2 patients with severe left main coronary artery disease. In our two cases, occlusion of the RCA diverted most of the cardioplegic infusion to the left coronary artery, while the remaining solution perfused the sinoatrial area and the pulmonary cone through the homonymous branches of the RCA. Some of the cardioplegic solution may also flow directly to the left coronary artery through Vieussens' ring. In the arrested heart, the exact distribution of cardioplegic flow through these previously mentioned vessels is dependent on the relative resistances of these more or less autonomous vascular circuits.
Nevertheless, the indications of "directed cardioplegia" may not be restricted to the left main coronary artery disease. The diversion of cardioplegic solution to a severely diseased artery after surgical occlusion of the other patent branches may also find application in other specific cases of coronary artery bypass graft surgery. In a typical nonselective antegrade distribution of cardioplegic solution, the flow through severely stenosed arteries is minimal because their resistance to flow is relatively high and results in a noneffective regional myocardial protection (high resistance–low perfusion areas) [1]. After the completion of the distal anastomosis, the antegrade administration of cardioplegia through the graft will now become effective, because those high resistance–low perfusion myocardial zones have reverted to ones in which resistance to flow is low.
It must be noted that "directed cardioplegia" should not be considered as a replacement for retrograde cardioplegia. On the contrary, it can be a useful alternative when coronary sinus catheterization is very difficult and the efficacy of nonselective antegrade cardioplegia to protect myocardial regions with high resistance to flow is questioned.
Theoretically, the diversion of cardioplegia with the same technique into myocardial areas with high resistance to flow can be applied during its retrograde administration as well. In this case, the occlusion of the main artery that normally drains the blood from a specific area during the retrograde perfusion ("arterial run off") could result in diversion of the cardioplegic solution to myocardial regions in which the resistance to flow is high and were otherwise poorly perfused [1]. In such a situation there is no doubt that the presence of collateral blood vessels that originate from another coronary artery is essential to prevent the occurrence of myocardial edema. For this reason, we believe that the results of "diverted retrograde cardioplegia" are unpredictable, thereby making it an option involving risk.
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References
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- Kouerinis IA, Manopoulos GC, Zografos G, et al. Retrograde cardioplegia in CABG: is it really useful?. The microcirculation and a capillary unit model. Med Sci Monit 2006;12:265-268.
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Abstract
Introduction
