Ann Thorac Surg 2005;80:1893-1897
© 2005 The Society of Thoracic Surgeons
New technology
Off-Pump CABG with Synchronized Arterial Flow Ensuring System
Go Watanabe, MD, PhD
*
,
Hiroyuki Kamiya, MD,
Hiroshi Nagamine, MD,
Shigeyuki Tomita, MD,
Yoshinao Koshida, MD,
Satoshi Nishida, MD,
Hiroshi Ohtake, MD,
Sadahiko Arai, MD,
Tamotsu Yasuda, MD
Department of General and Cardiothoracic Surgery, Kanazawa University School of Medicine, Kanazawa, Japan
Accepted for publication December 28, 2004.
* Address correspondence to Dr Watanabe, Department of General and Cardiothoracic Surgery, 13-1 Takaramachi, Kanazawa, Ishikawa 920-9641, Japan (Email: go{at}med.kanazawa-u.ac.jp).
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Abstract
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PURPOSE: We developed a synchronized, arterial-flow, ensuring system to perform coronary anastomoses safely without any ischemia-related event.
DESCRIPTION: Arterial blood is removed from the femoral artery. The resulting blood passes a switching valve and is pumped out to a syringe pump. This pump controller provides pulsatile arterial blood flow synchronized with the diastolic phase on an electrocardiogram. The arterial blood is perfused to the coronary artery through a fine flexible cannula during anastomosis.
EVALUATION: From February 1999, 524 consecutive patients were operated on using the synchronized arterial flow ensuring system. Mean duration for each anastomosis was 7.6 ± 3.3 minutes (range, 4 to 20 min). There were no intraoperative fatal arrhythmias, ventricular arrhythmias, or short-run or hemodynamic deterioration during anastomoses. No hospital death was observed, and postoperative myocardial infarction occurred in 2 patients (0.4%). Postoperative angiography showed a 98.1% patency rate.
CONCLUSIONS: The early clinical and angiographical results for off-pump CABG with the synchronized arterial flow ensuring system were excellent without mortality. We believe that off-pump CABG can be more safely performed using the synchronized arterial flow ensuring system based on our favorable results.
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Introduction
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We developed a synchronized, arterial-flow, ensuring system to perform coronary anastomoses safely without any ischemia-related event, and believe that off-pump coronary artery bypass grafting (CABG) can be more safely performed using the synchronized arterial-flow ensuring system based on our favorable results.
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Technology
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Off-pump CABG without cardiopulmonary bypass has emerged as a promising technique for the surgical revascularization of patients with coronary artery disease. Cumulative regional impairment caused by prolonged coronary occlusion during distal anastomosis to the target vessels may lead to hemodynamic deterioration or produce hazardous ventricular arrhythmias. Strategies to decrease ischemic injury and to promote early recovery of each grafted myocardial region include the use of intraluminal shunts or ischemic preconditioning procedure grafting, but these methods have shown little or no effect in patients with severe proximal coronary artery stenosis suffering from angina or severe ischemic heart disease who had low coronary pressure and unstable flow [1, 2]. It would be more desirable if the surgery could be performed safely without any consideration of myocardial ischemia.
To perform anastomoses safely without any ischemia-related event, we developed the synchronized arterial flow ensuring system (SAFE-System [Nemoto Kyorindo, Tokyo, Japan]). Our SAFE-System ensures a physiologic arterial blood flow synchronized with the heart beat during the anastomoses using a syringe pump system [3]. We report herein the details of our method and our initial clinical experience with the SAFE-System.
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Technique
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Basic Concept of the SAFE-System
Figure 1
shows the SAFE-System circuit. A catheter is normally inserted into the femoral artery to avoid complications due to manipulation of the ascending aorta, and arterial blood is removed. The resulting blood passes a switching valve and is pumped out to a syringe pump. This pump controller provides pulsatile arterial blood flow synchronized with the diastolic phase on an electrocardiogram. The arterial blood is perfused to the coronary artery through a fine flexible cannula during anastomosis. Although the proximal site of anastomosis is snared, myocardial ischemia does not occur during anastomosis due to the SAFE-System.
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Fig 1. Mini-pump system: (A) Femoral blood is directed from the femoral cannula (B) through the mini-pump system to the perfusion set, and finally, (C) the distal coronary branches. (D) The infusion rate is controlled by the surgeon using the remote control unit.
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The Pump Controller
This controller controls a blood amount to be injected, a piston speed, a delay time duration from the R wave of the electrocardiogram to adjust the blood flow to the diastolic phase of the cardiac cycle. The flow rate of the SAFE-System can be set at 0.1 mL/beat (approximately 15–20 mL/min), 0.2 mL/min (approximately 20–25 mL/min), or up to 0.3 mL/beat (approximately 25–30 mL/min). Differences between set flow and real flow were investigated and confirmed in detail in our previous animal experiment, and it showed that the mean coronary pressure under the SAFE-System perfusion was within physiologic range (range, 50 to 65 mm Hg) [3]. This pump controller can be operated with a remote control. Using this remote control, the surgeon can control various settings of the SAFE-System.
The Blood Transmission Tube and Syringe Pump
The blood removal catheter is inserted into the femoral artery and connected to a flexible blood transmission tube. The material of this tube was chosen for its elasticity, which is similar to human arterial walls making it possible to obtain physiologic blood flow. The syringe can trap air contained in the circuit and blood intake, because the top of the syringe positions lower, and discharging can be done without fear of myocardium air embolization [3].
Coronary Cannula
With the coronary cannula for the SAFE-System, coronary arteries more than 1 mm can be perfused. This cannula has flexibility with the aim of absorbing extremely high pressure blood flow and preventing direct coronary artery endothelial injury due to insertion [3]. It is also designed as a suture guide during anastomosis. The operation field can be made easily by handling the cannula, and accidental miss-stitching of the posterior coronary wall can be prevented. The cannula includes an enlarged portion at the tip, which can also prevent back bleeding from the arteriotomy site by selecting a suitable size to the coronary artery.
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Clinical Experience
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Patients
From February 1999 to April 2004, 524 consecutive patients were on operated using the SAFE-System. In this period, we performed all CABGs as off-pump or on-pump beating (8%). Clinical and angiographic characteristics at admission of all the patients are shown in Table 1. We initiated the application of the SAFE-System in clinical use after obtaining approval from the local ethics committee and informed consent from the patients.
Surgical Procedure
Standard median sternotomy or a small anterior thoracotomy was performed according to the number of bypasses as well as the anatomy of the target coronary artery. After systemic heparinization (1.5 mg/kg), the SAFE-System circuit was established. The flow rate of the SAFE-System was set at 0.1 mL/beat and adjusted up to 0.3 mL/beat according to myocardial tissue oxygenation monitoring at the distal myocardium using a three-wavelength near-infrared spectroscopy (PSA-500 [Biomedical Science, Kanazawa, Japan]). Activated clotting time was maintained to be greater than 200 seconds. Sutures (5-0 polypropylene) were used to encircle the target coronary artery to snare the upstream from the arteriotomy site. After the 3-minute test snaring, a coronary arteriotomy was performed, and the distal end of the coronary cannula was inserted into the target vessel. Then the proximal snare was tightened and the distal coronary artery was perfused by the SAFE-System. The bypass graft was anastomosed to the coronary artery with a running suture of 8-0 or 7-0 polypropylene with the flexible cannula in place. The suture was secured after removing the catheter.
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Results
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Number of Distal Anastomoses and Successful Safe-System Insertion
A total of 1,583 anastomoses were performed and a total of 1,558 anastomoses were accomplished using this SAFE-System to either the left anterior descending artery (100%, 511 of 511 anastomosis), diagonal branch (97%, 230 of 238 anastomoses) circumflex coronary artery (98%, 433 of 442 anastomoses) or the right coronary artery (98%, 384 of 392 anastomoses). The coronary cannula of the SAFE-System could not be inserted for 25 anastomoses because of anatomical reasons, such as a small coronary less than 1 mm and a kink of the coronary artery. Mean duration for each anastomosis was 7.6 ± 3.3 minutes (range, 4 to 20 min).
Comparison of Perioperative Ischemia-Related Events
Perioperative ischemia-related events are presented in Table 2. Several events happened during the positioning; however, there were no intraoperative fatal arrhythmias, ventricular arrhythmias, or short-run or hemodynamic deterioration during anastomoses. There was one case in which a third degree atrioventricular block occurred on occlusion at the right coronary artery, but was resolved quickly after placing the SAFE-System.
Early Clinical Results
No hospital death was observed. Postoperative myocardial infarction occurred in 2 patients (0.4%). Low output syndrome occurred in 2 patients (0.4%). Two patients suffered from newly developed cerebrovascular events (0.4%). Two patients had sternal wound infection develop (0.4%). Six patients needed reoperation for postoperative bleeding in the SAFE-System group (1.1%). Postoperative temporally atrial fibrillation occurred in 63 patients (12%).
Postoperative Angiography
The necessity and significance of postoperative coronary angiography were explained to all patients, and angiography was performed if patients agreed. Postoperative angiography was performed about 2 weeks after the operation in 385 patients (73%) in the SAFE-System group. Results of postoperative angiography are shown in Table 3. Angiographically, no stenosis was observed in distal coronary arteries in which the coronary perfusion catheters had been placed.
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Comment
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In the current series, the SAFE-System was applied as an intraoperative technical maneuver that made it possible to achieve excellent results while performing off-pump CABG.
The introduction of off-pump CABG has broadened worldwide, and many centers have introduced this procedure along with the use of a coronary stabilizer that is now commercially available in an extensive area. However, even with the introduction of this device to facilitate the application of this novel technique, the problem of myocardial ischemia during coronary occlusion could not be circumvented. During the time of coronary occlusion, theoretically myocardial ischemia is in progress even though the occlusion lasts for a very short period. Prolonged coronary occlusion may cause fatal ventricular arrhythmias, hemodynamic deterioration, or perioperative myocardial infarction in cases with severe coronary stenosis [1, 2].
Several methods have been devised to avoid or reduce myocardial ischemia during anastomoses, and at present the most popular method for such a purpose is the one using the intracoronary shunt tube [4]. However, it may not be able to provide adequate perfusion in cases with low blood pressure or severe proximal coronary artery stenosis [5]. Furthermore, blunt insertion or extraction of a stiff intraluminal shunt at both proximal and distal sites can cause endotherial denudation or sometimes catastrophic endotherial damage in the presence of diffuse calcified coronary artery vessels [6].
Recently, two similar perfusion systems for off-pump CABG were reported. One is the perfusion-assisted direct coronary artery bypass (PADCAB) system by Cooper and colleagues [7], and another is the coronary-assisted perfusion system by Walker and colleagues [8]. Their methods provide non-pulsatile flow using a servo-controlled pump during anastomoses. On the other hand, we also reported experimental investigations of the perfusion-assisted device in almost simultaneous timing (in the year 2002) as the coronary active perfusion system [3], which we call a SAFE-System in the present article. Our SAFE-System provides coronary flow independent of systemic blood pressure similar to their devices, but it is essentially different from their devices in two points of the following. The flow ejected from the SAFE-System is the pulsatile one, which is synchronized with the diastolic phase of the native cardiac cycle from the syringe pump, whereas their systems generate steady flow. Moreover, coronary perfusion pressure stays within the physiologic range from 50 to 65 mm Hg [3] in our SAFE-System, whereas their systems need supra-systemic perfusion pressure, which can cause endothelial injury because of non-physiological high pressure. In contrast to their systems, drug administration through the circuit is not adopted in our SAFE-System, because we consider that selective drug delivery into coronary arteries is not physiologic and can cause some adverse effects.
Essentially it is well known that the coronary blood flow is dominant in the diastolic phase because cardiac contraction squeezes the myocardial vessels. In the field of percutaneous transluminal coronary angioplasty, active hemoperfusion has been studied in detail, although it never led to widespread clinical application. Lehmann and colleagues [9] reported that a clinical trial of active perfusion performed with the delivery of blood at 60 mL/min to patients undergoing coronary angioplasty revealed lower levels of maximum pain score and maximum segment elevations than in a control group; however, this flow rate appears to have been too great as the method never became widely practiced, and the pump flow was set as 0.1 mL/beat, which means approximately 15-20 mL/min, in the present study. Thus, we consider that pulsatile perfusion is better than nonpulsatile substitution to effectively maintain myocardial perfusion. However, this issue should be experimentally studied at first, and we are now investigating it using a porcine model.
With the SAFE-System several technical hazards of off-pump CABG can be prevented. First, we could perform off-pump CABG not only safely, but without having to perform anastomosis under severe pressure regarding anastomosis time. It is considered that we could therefore accomplish high quality anastomoses. The SAFE-System provided great advantages to surgeons by maintaining a bloodless field due to specially devised fine cannula, and thereby preventing the occurrence of miss stitch to the back wall of the coronary artery. In addition, with the use of the SAFE-System, no intimal injury was observed to the proximal, distal coronaries and anastomotic sites in our previous animal study [10]. It was due to fine, smooth material of the cannula and simplicity of manipulation, as opposed to intraluminal shunt in which the blind insertion and removal of a stiff shunt is required [5]. Finally, there is an educational advantage to the SAFE-System because it is very helpful for both young surgeons and trainees in terms of providing a bloodless comfortable field to work on. The SAFE-System makes possible a safe and precise construction of coronary artery grafting on the beating heart.
In conclusion, the early clinical and angiographic results of off-pump CABG with the SAFE-System were excellent without mortality. Although further prospective study is necessary, we believe that off-pump CABG can be more safely performed using the SAFE-System from our favorable results.
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Disclosures and Freedom of Investigation
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The authors had full control of the design of the study, methods used, outcomes, parameters, analysis of data, and production of this report. Nemoto Kyorindo (Tokyo, Japan) provided the SAFE-System free of charge for these experiments, but did not fund this study. All the measurements were done by the authors without the assistance of the company.
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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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- Novick RJ, Fox SA, Stitts LW, et al. Cumulative sum failure analysis of a policy change from on pump to off pump coronary artery bypass grafting Ann Thorac Surg 2001;72(Suppl):S1016-S1021.[Abstract/Free Full Text]
- Kamiya H, Watanabe G, Doi T, et al. A coronary active perfusion system for off-pump coronary artery bypassadvantage over passive perfusion regarding the physiology of the coronary artery. ASAIO J 2002;48:658-664.[Medline]
- Rivetti LA, Gandra SMA. Initial experience using an intraluminal shunt during revascularization of the beating heart Ann Thorac Surg 1997;63:1742-1747.[Abstract/Free Full Text]
- Donohue TJ, Kern MJ, Aguirre FV, et al. Assessing the hemodynamic significance of coronary artery stenosisanalysis of translesional pressure-flow velocity relations in patients. J Am Coll Cardiol 1993;22:449-458.[Abstract]
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- Cooper WA, Corvera JS, Thourani VH, et al. Perfusion-assisted direct coronary artery bypass provides early reperfusion of ischemic myocardium and facilitates complete revascularization Ann Thorac Surg 2003;75:1132-1139.[Abstract/Free Full Text]
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- Lehmann KG, Atwood JE, Snyder EL, Ellison RL. Autologous blood perfusion for myocardial protection during coronary angioplastya feasibility study. Circulation 1987;76:312-323.[Abstract/Free Full Text]
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Top
Abstract
Introduction
