Ann Thorac Surg 2006;81:706-710
© 2006 The Society of Thoracic Surgeons
New technology
Portable Coronary Active Perfusion System for Off-Pump Coronary Artery Bypass Grafting
Yoshinao Koshida, MD
*
,
Go Watanabe, MD,
Tamotsu Yasuda, MD,
Shigeyuki Tomita, MD,
Shinichi Kadoya, MD,
Taro Kanamori, MD
Department of General and Cardiothoracic Surgery, Kanazawa University School of Medicine, Kanazawa, Ishikawa, Japan
Accepted for publication June 22, 2005.
* Address correspondence to Dr Koshida, 13-1 Takaramachi, Kanazawa, 920-8641 Japan (Email: yoshinaoko2000{at}yahoo.co.jp).
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Abstract
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PURPOSE: The present study was performed to develop a new perfusion system for off-pump coronary artery bypass grafting and to examine whether even a simple coronary perfusion system can maintain adequate blood flow delivery during anastomosis.
DESCRIPTION: The experiment was performed in two stages. In procedure 1, 3 pigs with left anterior descending artery occlusion were used to evaluate optimal perfusion flow rate and coronary artery internal pressure, and to evaluate the safety area of perfusion. In procedure 2, 6 pigs were used to validate the new portable coronary perfusion system.
EVALUATION: The optimal blood flow in the portable coronary active perfusion system was less than approximately 40 mL/min. The small, easy to use pump system (ie, the portable coronary active perfusion system) may prevent hemodynamic deterioration and ventricular arrhythmia during coronary occlusion, resulting in better maintenance of left ventricular function.
CONCLUSIONS: Even a simple pump system can achieve effective perfusion for safe anastomosis. Further studies are required to allow the clinical use of this system.
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Introduction
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Off-pump coronary artery bypass grafting (OPCABG) is a promising technique for the treatment of ischemic heart disease. However, one concern with OPCABG is that temporary occlusion of the coronary artery, which is frequently required during anastomosis in OPCABG, can cause hemodynamic instability and myocardial damage [1]. In addition, retraction and stabilization maneuvers during OPCABG often cause systemic hypotension, especially when the heart is displaced vertically for exposure of its lateral and posterior branches [2].
Several clinical studies have demonstrated the effectiveness of intracoronary shunts, external shunt circuits, or ischemic preconditioning procedures [3, 4] to reduce ischemic injury. These methods are advantageous in terms of both cost and time, and can be easily set up. However, these methods have shown little or no effect in patients with severe proximal coronary artery stenosis or severe ischemic heart disease with low coronary pressure and unstable flow. Moreover, it is unclear how the adequacy of blood flow is affected by internal or external shunts when systemic blood pressure deteriorates during retraction or compression of the heart in OPCABG [5].
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Technology and Technique
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We recently developed the coronary active perfusion system (CAPS) to avoid blood supply inadequacy in the ischemic myocardium in OPCABG [6]. This is an active perfusion technique in which oxygenated blood is supplied from the femoral artery and pressurized by a pump to optimize blood flow to the myocardium, and the amount of blood supply is not dependent on hemodynamic status during the procedure. However, CAPS includes a special pump, controller, and power supply system, and therefore is not easy to access, especially in emergencies. For that reason, use of this procedure has not yet become widespread.
We have developed a new perfusion system that may enable active perfusion of arterial blood into the coronary artery during coronary artery occlusion, and thus avoid ischemic injury during the procedure. Moreover, the apparatus required is small and simple in comparison with other coronary perfusion systems [6–8]. Herein we report details of our new method and describe experience with the new coronary perfusion system.
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Clinical Experience
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All animals received humane care in accordance with the "Principle of Laboratory Animal Care" formulated by the National Society for Medical Research and the "Guide for Care and Use of Laboratory Animals," prepared by the Institute of Laboratory Animal Resources, National Research Council and published by the National Academy Press, revised in 1996.
Nine pigs were used in this study. All pigs were sedated by intramuscular injection of ketamine (20 mg/kg body weight). Anesthesia was maintained with halothane (0.5% to 1.5%), and muscle relaxation was induced with pancuronium (0.1 mg/kg), which was administered through the peripheral intravenous route.
An arterial pressure line was inserted into the brachiocephalic artery through the common carotid artery. A Swan-Ganz catheter was inserted into the pulmonary artery through the right internal jugular vein for pressure monitoring and continuous cardiac output measurement (IntelliCath CCO/VIP, SAT-2 [Deerfield, Baxter, IL]). A 4-French catheter was inserted into the right femoral artery to remove arterial blood for the perfusion system. The experiment consisted of two stages.
Procedure 1
In procedure 1, 3 left descending coronary artery occluded pigs were used to determine the optimal perfusion flow rate. After systemic heparinization (200 u/kg), the left descending coronary artery was snared at a point just distal from the first diagonal branch, and a coronary arteriotomy was performed. A pressure wire (WaveMap [Endosonics, Rancho Cordova, CA]) and coronary perfusion cannula were then inserted through the arteriotomy site. To prevent escape of pressure from the arteriotomy site, a site distal to that of arteriotomy was snared. The resulting arterial blood passed through a modified percutaneous cardiopulmonary support circuit with a centrifugal pump (Mix Flow [JMS, Tokyo, Japan]) was led to the installed inline electromagnetic flow probe (Nihon-Kohden, Tokyo, Japan) in the last part of the circuit to measure flow of coronary active perfusion (Fig 1). Coronary perfusion flow was gradually increased in a stepwise manner to determine how much flow it raised to critical pressure and to evaluate the upper limit of optimal perfusion flow.
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Fig 1. Measurement of coronary perfusion flow and coronary arterial pressure during coronary active perfusion. (A) Schematic presentation of perfusion circuit. (B) Efferent pump and flow meter. (C) The CAPS cannula. (CAPS = coronary active perfusion system; LAD = left anterior descending artery; PCPS = percutaneous cardiopulmonary support.)
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Procedure 2
In procedure 2, 6 pigs were used to validate the new coronary perfusion system, including cardiac function during perfusion. The portable CAPS is shown in Figure 2. Arterial blood was passed through extension tubes and was pumped out from the microdiaphragm pump (CM 15W Enomoto Micro Pump [Enomoto Kogyo, Tokyo, Japan]). This pump system is small, simple, battery-driven, and inexpensive. The pump and battery can be placed in a small waterproof case and can be operated by a surgeon alone without the assistance of a perfusionist. This small pump can transfer liquid at a maximum rate of 100 mL/min. The approximate flow rate can be set using the coronary perfusion cannula. The coronary cannula used in the present study has already been applied in our unit as previously reported [6, 7]. The enlarged fixed portion of the cannula can prevent back bleeding from the arteriotomy site by selecting a size of enlarged portion suitable for each coronary artery. In this procedure, we used a cannula measuring 1.25 mm in external diameter and 0.8 mm in inner diameter.
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Fig 2. (A) Small diaphragm pump and motor unit. (B) Portable coronary active perfusion system (CAPS). (C) The CAPS cannula.
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Coronary perfusion was performed for 30 minutes as described in procedure 1, and hemodynamic and mechanical data were recorded. Suitable portable CAPS perfusion flow was set based on flow that did not surpass the upper limit set in procedure 1. A conductance catheter (Conductance-PC software [Cardio Dynamics BV, Zoetermeer, The Netherlands]) was used to evaluate left ventricular function and mechanical data. Left ventricular contractility was quantified based on the slope of the end systolic pressure-volume relation (end-systolic elastance [Ees] [mm Hg/mL]). The endpoint of this study was 30 minutes of observation without ventricular arrhythmia. At the end of the experiment, the pigs were given a lethal intravenous injection of pentobarbital and potassium chloride, and transmural samples of the left ventricular anterior wall were taken for histologic examination.
Statistical analyses were performed using SPSS for Windows (version 10.1.3J [SPSS Inc, Chicago, IL]). Cumulative data are expressed as means ± standard deviation. Simple linear regression was used to analyze the relationship between the perfusion flow rate and coronary pressure. The paired t test was performed for analysis of hemodynamics before and after the experiments, and repeated analysis of variance was used for analysis of changes in the hemodynamics, coronary artery pressure, coronary perfusion flow, and Ees.
Results of Procedure 1
Coronary pressure increased proportionately with gradual increases in perfusion flow. Until a perfusion flow of 40 mL/min, the mean slope was expressed by Y = 1.41X + 22.1. However, with perfusion flow in excess of 40 mL/min, the mean slope was greater than the values expected from the perfusion flow until 40 mL (Y = 6.66X – 184; r = 0.999; p < 0.01), and the increase in peripheral resistance predicted endothelial injury (Fig 3). At a perfusion flow exceeding 60 mL/min, coronary pressure increased regardless of changes in perfusion flow.
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Fig 3. The relationship between perfusion flow and mean coronary artery pressure. Data are presented as means ± standard deviation.
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Results of Procedure 2
Ventricular arrhythmia was not observed in any of the pigs for 30 minutes. None of the hemodynamic variables (ie, heart rate, aortic pressure, cardiac output) changed during the 30-minute observation period (Fig 4A). The changes in Ees are shown in Figure 4B. The value of Ees did not change significantly during the experiment.
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Fig 4. Changes in mean arterial pressure (top). Changes in the slope of the end systolic pressure volume relation (Ees) during the experiments (bottom). Data are presented as means ± standard deviation.
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Free flow was 35.8 ± 1.16 mL/min. Perfusion flow was 30.5 ± 3.50 mL/min, and the decrement in perfusion was 14.9%. Coronary pressure and perfusion flow rate during the experiment are shown in Figure 5. The coronary pressure was lower than that in procedure 1, and was not greater than the physiologic range. Flow pattern was slightly dominant in the diastric phase (Fig 6).
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Fig. 6. Waveform of coronary perfusion flow and electrocardiogram. The coronary active perfusion system pattern (upper). Electrocardiogram (lower).
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On pathologic examination none of the pigs showed tissue edema or vessel injury. Endothelium cells were well preserved at the coronary artery distal to the cannula tip.
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Comment
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Several methods have been developed for perfusion of the coronary artery and to avoid myocardial ischemia during OPCABG. The intracoronary shunt method and external shunt circuit have been used extensively for this purpose [3, 4]. These methods are advantageous with regard to both cost and time because they are inexpensive and can be easily set up as they do not require any specialized apparatus. These two methods have the same characteristics given that distal coronary bed perfusion can be provided passively. However, several studies have indicated little flow with these methods. Muraki and colleagues [5] reported that intracoronary shunts provided only 10% 
30% of baseline blood flow in dogs even without stenosis of the coronary artery. Moreover, it is unclear how the adequacy of blood flow is affected by internal or external shunts when systemic blood pressure deteriorates during retraction or compression of the heart in OPCABG. Therefore, some active perfusion systems may be required to obtain stable flow.
To prevent myocardial ischemia during OPCABG, several active perfusion methods have been reported. Muraki and colleagues [8] investigated the efficacy of active coronary perfusion with a nonpulsatile pump (perfusion-assisted direct coronary artery bypass). Recently we reported the CAPS to avoid inadequate blood supply for ischemic myocardium [6, 7]. These procedures are active perfusion techniques and have the characteristic that the amount of blood supply does not depend on hemodynamic status during the procedure. Vassiliades and colleagues [9] reported that active coronary perfusion using an in-line pump resulted in superior myocardial protection and performance during OPCABG as compared with either no coronary perfusion or passive coronary perfusion. However, these active perfusion systems have a number of disadvantages in that they require large, expensive, and complicated settings, and therefore these systems have not yet gained widespread acceptance among cardiac surgeons.
The diaphragm pump used in the present study was able to supply a stable flow. In addition, this pump system was small, inexpensive, and consumed little power, and therefore could be driven by a small battery. The flow rate controller was omitted to simplify the system, but some flow rate adjustment was possible by adjusting the inner diameter of the circuit. The flow rate was set at approximately 30 mL/min, the value determined by procedure 1, so that the coronary artery pressure was maintained within the physiologic limits. Simplification of the system prevents measurement of coronary pressure, but if the coronary artery pressure increases too much, excess blood over the lesional myocardial demand may be washed away from the arteriotomy site. Therefore, it is important to select an appropriate cannula size. Thus, critical high pressure does not represent a significant concern.
The portable CAPS developed in the present study can achieve adequate perfusion with a constant volume, nonpulsatile pump. There have been few reports regarding small pumps for coronary perfusion. A miniature vibrating flow pump was reported for external shunt catheter [10]. However, its clinical application has not been reported yet. In future studies it will be necessary to perform comparisons between our system and such a small pump.
In conclusion, hemodynamic deterioration and ventricular arrhythmias during coronary occlusion were prevented by the portable CAPS. Even a simple pump system can achieve effective perfusion. Further studies including examination of adequate coronary active perfusion flow and pressure in humans are necessary to allow clinical application of this system.
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Disclosures and Freedom of Investigation
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The microdiaphragm pump and catheter were purchased by Kanazawa University. The authors have performed a free and independent evaluation of this new technology. The authors had full control of the design of the study, methods used, outcome measurements, analysis of data, and production of the written report.
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Disclaimer
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The Society of Thoracic Surgeons, the Southern Thoracic Surgical Association, and The Annals of Thoracic Surgery neither endorse nor discourage use of the new technology described in this article.
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References
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- Vassiliades Jr TA, Nielsen JL, Lonquist JL. Hemodynamic collapse during off-pump coronary artery bypass grafting Ann Thorac Surg 2002;73:1874-1879.[Abstract/Free Full Text]
- Grundeman PF, Borst C, van Herwaarden JA, Verlaan CW, Jansen EW. Vertical displacement of the beating heart by the octopus tissue stabilizerinfluence on coronary flow. Ann Thorac Surg 1998;65:1348-1352.[Abstract/Free Full Text]
- Lucchetti V, Capasso F, Caputo M, et al. Intracoronary shunt prevents left ventricular function impairment during beating heart coronary revascularization Eur J Cardiothorac Surg 1999;15:255-259.[Abstract/Free Full Text]
- Arai H, Yoshida T, Izumi H, Sunamori M. External shunt for off-pump coronary artery bypass graftingdistal coronary perfusion catheter. Ann Thorac Surg 2000;70:681-682.[Abstract/Free Full Text]
- Muraki S, Morris CD, Budde JM, et al. Preserved myocardial blood flow and oxygen supply-demand balance with active coronary perfusion during simulated off-pump coronary artery bypass grafting J Thorac Cardiovasc Surg 2002;123:53-62.[Abstract/Free Full Text]
- Kamiya H, Watanabe G, Doi T, et al. Coronary active perfusion system can maintain myocardial blood flow and tissue oxygenation Eur J Cardiothorac Surg 2002;22:410-414.[Abstract/Free Full Text]
- Watanabe G, Kamiya H, Nagamine H, et al. Off-pump CABG with Synchronized Arterial Flow Ensuring System (SAFE-System) Ann Thorac Surg (in press)..
- Muraki S, Tsukamoto M, Komatsu K, et al. Minimally ischemic off-pump coronary artery bypass graftingactive perfusion-assist with nitroglycerin-supplemented blood. Ann Thorac Surg 2003;76:298-300.[Abstract/Free Full Text]
- Vassiliades Jr TA, Nielsen JL, Lonquist JL. Coronary perfusion methods during off-pump coronary artery bypassresults of a randomized clinical trial. Ann Thorac Surg 2002;74:S1383-S1389.[Abstract/Free Full Text]
- Kawano S, Isoyama T, Kobayashi S, et al. Miniature vibrating flow blood pump using a cross-slider mechanism for external shunt catheter Artif Organs 2003;27:73-77.[Medline]
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Abstract
Introduction
