Ann Thorac Surg 2005;79:814-818
© 2005 The Society of Thoracic Surgeons
Original article: Cardiovascular
Off-Pump, In Situ Internal Thoracic Artery Grafting: A Durable Treatment for Single-Vessel Coronary Artery Disease
Kerem M. Vural, MD*,
Zafer H. Iscan, MD,
Ay
egul Kunt, MD,
Erol Sener, MD,
Oguz Tasdemir, MD
Department of Cardiovascular Surgery, Yuksek Ihtisas Hospital of Turkey, Ankara, Turkey
Accepted for publication August 23, 2004.
* Address reprint requests to Dr Vural, N. Tandogan cad. 5/6 Kavaklidere, 06540 Ankara, Turkey (E-mail: kvural{at}tr.net).
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Abstract
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BACKGROUND: The value of off-pump in situ left internal thoracic artery to left anterior descending coronary artery bypass grafting in single-vessel coronary artery disease was assessed by long-term angiographic and clinical data.
METHODS: One-hundred three randomly selected patients (87 male, 16 female; mean age, 57.4 ± 10.5 years) underwent postoperative angiographic control after an average postoperative period of 4.8 ± 2.9 years (up to 8.2 years; a total of 490 patient-years).
RESULTS: Fifty-five patients (52%) were asymptomatic, whereas 31 (30%) had anginalike chest pain. Ninety-seven patients (94.2%) were in New York Heart Association class I or II. Five-year angina-free survival was 81% ± 5%. Of 103 left internal thoracic arteries assessed, 99 were patent (overall patency, 96.1%). All four cases having occluded grafts had mild native vessel stenoses (<80%) before operation. The patency rate was 99% ± 1% at 3 years, and 93% ± 4% at 5 years. The left ventricular segmental wall motion score of the left anterior descending coronary arterial distribution improved from 4.1 ± 1.1 to 3.7 ± 0.9 (p = 0.001). Consequently, 15 patients (15%) underwent secondary revascularization (11 interventional and 4 surgical) 4.8 ± 2.1 years after the primary operation. The most frequent indication for interventional revascularization was atherosclerotic progression in systems other than left anterior descending artery. The cases with graft occlusion were treated surgically. Five-year freedom from interventional or surgical repeat revascularization was 91% ± 4%.
CONCLUSIONS: In addition to the well-documented safety and reliability, off-pump in situ left internal thoracic artery grafting is also a durable treatment for isolated left anterior descending artery disease, in both clinical and angiographic terms.
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Introduction
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The optimal approach to the patient with so-called proximal left anterior descending artery (LAD) lesion is usually considered surgical; however, with current advances in the area of interventional cardiology, this may soon become a subject of debate [1, 2]. The separation between the indication zones of surgical and interventional treatments are transforming from a virtual borderline into an ever-growing intersectional area [1]. Despite the advances in the so-called less-invasive interventional techniques, benefits for patients having diabetes mellitus and so-called type-B2/C (Ryan) lesions [3], including total occlusions, are still suboptimal, and restenosis is still the Achilles' heel of such modalities. Off-pump coronary artery bypass grafting (OPCAB) is one derivation of surgical revascularization in an attempt to be less invasive by avoiding cardiopulmonary bypass pathophysiology, and is also more cost-effective. With better stabilization techniques, the safety and efficacy of the procedure is well documented, but data are still needed in terms of long-term objective assessment as one of the major advantages of the procedure over interventional approaches is expected to be its durability [1]. The presented series is an analysis of long-term clinical and angiographic results from a substantial number of patients randomly selected among those undergoing isolated in situ left internal thoracic artery (LITA)-to-LAD OPCAB. The primary goal was to help accumulate data for validation of the surgical approach in the treatment of single-vessel (LAD) coronary artery disease.
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Material and Methods
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Demographics
One hundred three patients, of 1261 cases undergoing OPCAB for single-vessel (LAD) coronary artery disease between May 1993 and October 1996, were randomly selected among those who gave consent for angiographic control after an average postoperative period of 4.8 ± 2.9 years (up to 9 years, a total of 490 patient-years). Eighty-seven patients (84.5%) were male and 16 were female (15.5%), with a mean age of 57.4 ± 10.5 years (range, 32 to 80 years). All operations were elective, isolated single-vessel grafting procedures. A total of 103 in situ LITAs have been assessed. As risk factors, there were 16 patients (15.5%) with positive family history for arteriosclerosis, 21 (20.4%) had diabetes mellitus, 40 (38.8%) had hypertension, 40 (38.8%) had hypercholesterolemia, 16 (15.5%) had hypertriglyceridemia, and 8 (7.8%) were obese. In 11 patients (10.7%), preoperative left ventricular performance was severely disturbed, defined as a left ventricle segmental wall motion score (LVSWMS; see below) exceeding 11 or a left ventricular end-diastolic pressure greater than 25 mm Hg. Thirty-one patients (30%) had normal left ventricular function (LVSWMS = 7).
Operative Technique
As described previously [4, 5], after median sternotomy, the LITA is harvested and dilated by topical papaverine hydrochloride. One or more wet gauzes may be placed beneath the heart for purposes of elevation. The LAD is exposed, and an appropriate portion of approximately 1 cm is dissected free from the surrounding fat tissue. Then the arteriotomy is made with an iris scalpel and enlarged using Pott's scissors. If profuse rinsing with warm saline solution is insufficient against bleeding, we apply an atraumatic bulldog clamp approximately 1.5 cm proximal to the coronary artery (together with a bulk of surrounding fat pad) during anastomosis. A simple intermittent regional immobilization method is applied to facilitate the anastomosis. During the manipulation of the native coronary vessel (ie, arteriotomy, needle passage), the surgeon and the first assistant grasp the opposite sides of adjacent epicardium with forceps, pulling up with a slight tension. Thus approximately 2 to 3 cm of epicardial segment is rendered motionless, with the heart beating underneath. No special fixation device was used in the present series. After completing the anastomosis, before tying the suture, a 1- or 1.5-mm probe is passed through the coronary artery, not only to check the anastomosis but also to dilate possible native coronary vessel spasm caused by the temporary hemostatic bulldog clamp application.
Postoperative Coronary Angiography
Informed patient consent and institutional authorities' approval was obtained before the postoperative control coronary angiography. Coronary angiograms were performed in two planes, right anterior-oblique and left anterior-oblique positions. At least three physicians, including both cardiologists and surgeons who were unaware of the aim of the study, interpreted all angiograms. For scoring the left ventricular segmental wall performance, the biplane left ventriculogram was divided to a total of seven segments (five in the right anterior oblique projection: apical, anterobasal, anterior, posterobasal, and inferior; and two in the left anterior oblique projection: septal and posterolateral). Then points were given for the each segment, and the LVSWMS was calculated as the sum of these scores as follows: normal wall motion, 1 point; hypokinetic, 2 points; akinetic, 3 points; dyskinetic, 4 points; aneurysm, 5 points. The combined anterior-apical-septal LVSWMS was calculated as the sum of the scores of these three segments, reflecting the performance score of a region presumably supplied by the LAD. The quality of the native coronary vessel was defined as good/fair or poor, and the diameter was assessed using 1-, 1.5-, and 2-mm coronary probes intraoperatively. Also, low-grade <80%) and high-grade lesions (
80%) were defined on the basis of preoperative angiograms.
Statistical Analysis
Data are presented as mean ± standard deviation. Determinants of patency were analyzed by 
2 or Fisher's exact tests when applicable. Survival and patency estimates were expressed as Kaplan-Meier curves. A p value equal to or less than 0.05 was considered statistically significant.
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Results
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Clinical Results: Symptomatology
Fifty-five patients were asymptomatic (52%), 12 had nonspecific complaints (11%), 26 had anginalike chest pain (25%), 7 had exertional dyspnea (7%), and 5 had chest pain and dyspnea together (7%). Chest pain was the most frequent symptom, presenting in 31 patients (30%; Table 1). Ten patients had Canadian Cardiovascular Society class III and 4 patients had class IV angina pectoris. Sixty-two patients were in New York Heart Association functional class I, 35 were in class II, and 6 were in class III. Ninety-seven patients (94.2%) were in New York Heart Association class I or II. Four patients exhibited ischemic electrocardiographic changes on exercise test. Five-year angina-free survival was 81% ± 5% (Fig 1), whereas 5-year symptom-free survival was 73% ± 6%.
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Fig 1. The 5-year freedom from angina pectoris in patients with single-vessel (left anterior descending coronary artery) disease treated surgically by off-pump in situ left internal thoracic artery grafting.
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Angiographic Data and Risk Factor Analysis
Of 103 LITAs assessed, 99 were patent (overall patency, 96.1%). The patency rate was 99% ± 1% at 3 years and 93% ± 4% at 8 years (Fig 2). The combined anterior-apical-septal LVSWMS improved from 4.1 ± 1.1 to 3.7 ± 0.9 (p = 0.001). No association of graft occlusion with uncontrolled hypercholesterolemia, hypertriglyceridemia, diabetes mellitus, hypertension, cigarette smoking, or family history for arteriosclerosis was found. In regard to native vessel characteristics, no impact of the quality or the caliber of the target vessel on patency was detected in this particular in situ LITA-to-LAD context. However, all 4 patients with occluded LITA grafts were among those having mild (low-grade) LAD artery stenosis (<80%) at the primary operation (Fig 3). There were no cases with occluded grafts among those having high-grade stenosis in the LAD artery.
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Fig 2. The 5-year patency of in situ left internal thoracic artery grafts anastomosed to the left anterior descending coronary artery by means of off-pump technique.
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Secondary Revascularization
The patients with occluded LAD grafts or significant native LAD lesions beyond the anastomosis were referred to undergo redo CABG in cases when they have good target vessels and salvageable myocardium. Patients with native vessel disease progression in the circumflex or right coronary arterial systems were often referred to undergo percutaneous transluminal coronary angioplasty or stenting, when their lesions were suitable for such procedures. Consequently, 15 patients (15%) underwent secondary revascularization (11 percutaneous transluminal coronary angioplasty and 4 redo CABG) 4.8 ± 2.1 years after the primary operation. The average period for percutaneous transluminal coronary angioplasty or stenting after the operation was 5.4 ± 1.8 years, with the most frequent indication being native coronary artery disease progression in systems other than the LAD (right coronary artery in 7 patients, circumflex system in 3, and diagonal coronary artery in 1). The cases with LAD graft occlusion were treated surgically (4 cases) 2.8 ± 2.1 years after the primary operation. Five-year freedom from revascularization (interventional or surgical) was 91% ± 4% (Fig 4). Five-year freedom from redo CABG (secondary surgical revascularization) was 92% ± 4%.
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Fig 4. Five-year freedom from secondary revascularization (percutaneous transluminal coronary angioplasty/stenting or repeat coronary arterial bypass grafting) in patients with single-vessel (left anterior descending coronary artery) disease treated surgically by off-pump in situ left internal thoracic artery grafting.
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Comment
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In situ arterial grafting with ITA grafts are the gold standard in surgical revascularization of atherosclerotic coronary arteries in terms of durability [6]. The LITA, in particular, is a perfect mate for the LAD coronary artery. In recent years, great advances in interventional techniques, such as drug-eluting stents, have challenged the concept of surgical revascularization with a growing popularity and an ever-expanding field of indication. Major advantages over standard CABG procedure are supposed to be less invasiveness by avoiding the risk and complications of general anesthesia, surgical incision, cardiopulmonary bypass, and also by elimination of a painful and unpleasant postoperative recovery period. However, in situ LITA-to-LAD bypass has proven to be highly efficient, the efficacy is durable, and the procedure can also be used in the setting of type B2/C lesions, extended disease, or total occlusion of the native coronary artery. In addition to these, salvation of nearby septal or diagonal artery origins is always possible, and the outcome in patients with diabetes is good. Application of OPCAB techniques may render this type of approach relatively less invasive. The safety and reliability of OPCAB technique in the short term have been well demonstrated; however, objective documentation for the durability of these good results is still needed.
This study provides relatively long-term clinical and angiographic data from a substantial number of patients randomly selected among those undergoing isolated in situ LITA-to-LAD OPCAB for the treatment of single-vessel (LAD) coronary artery disease. In addition to clinical and angiographic data presentation, prognostic factors were also analyzed for their possible influence on graft patency. We observed that the grade of the stenosis may have an impact on the patency of LITA grafts, as all four cases with occluded grafts had been constructed on native coronary vessels (LAD) having less than 80% stenoses, whereas there were no occluded grafts among those constructed on those having high-grade stenoses. This is in accordance with the study of Nakamura and colleagues [7], who observed that the string or coronary-coronary bypass more often in cases in which the recipient coronary artery had less than 75% stenosis. It is possible that competitive flow through the native coronary vessel interferes with that of the graft, and adversely affects graft patency in the long term [8–10]. A noticeable difference from other reports is that our data have not confirmed the importance of target vessel caliber and quality as the determinants of graft patency in this particular LITA-to-LAD context. However, in another study of ours, which includes other coronary targets (circumflex, right coronary, diagonal vessels) and saphenous vein grafts in considerable numbers, important relations between patency and the caliber, quality, and grade of stenosis of the target vessel were found. This is not necessarily an inconsistency. One explanation is that only the in situ LITA-to-LAD cases were considered in the presented study, and the LITA perfectly fits tiny coronary vessels in terms of caliber and flow rate. The inherent differences between the behavior of LITA and saphenous vein grafts seem to be accentuated when the procedure is OPCAB type. Kim and coworkers [11] reported that OPCAB type surgery may lower the patency of saphenous grafts. They concluded that the patency rate of saphenous vein grafts after OPCAB was significantly lower than that of arterial grafts or saphenous vein grafts constructed by conventional on-pump technique both in the early postoperative period and 1 year later. On these grounds, they even suggested some kind of perioperative anticoagulant therapy in patients having saphenous vein grafts if the nature of the procedure is OPCAB type [11].
Also, no adverse effect of known atherosclerotic risk factors (family history, hypercholesterolemia, diabetes mellitus, and so forth) was associated with graft occlusion in the presented study, most probably because of the superior resistance of the LITA to the atherosclerotic process. Indeed, the most frequent indication for repeat revascularization—be it interventional or surgical—in the presented series was atherosclerotic progression in vessels other than the LITA or LAD. However, longer periods of follow-up may reveal the true effect of ongoing arteriosclerosis.
A point deserving more emphasis is the improvement in LVSWMS. This demonstrates that those who may not tolerate on-pump technique because of additional risk of cardiopulmonary bypass and aortic cross-clamping may still benefit from this off-pump procedure to a good extent, even in the setting of single-vessel disease. The existence of triple-vessel disease is not essential to benefit from surgical revascularization.
There may be some limitations of the present study to consider. In long-term angiographic studies like this, including all consecutive patients of a large series at certain intervals is often difficult if not impossible, and randomization may become necessary. Another difficulty is to estimate the exact occlusion time of a graft or anastomosis, especially when calculating patency rates [12, 13]. One can only speculate that the onset of symptoms, which is often the reason that brings the patient to medical attention, may be close to the true occlusion time [12]. Finally, the presented OPCAB series were established in an era in which modern stabilization devices and exposure techniques are yet to be developed. Today's more advanced devices should yield better results.
In an era when novel interventional revascularization techniques are mushrooming, CABG and its variations such as OPCAB or minimally invasive coronary artery bypass grafting will certainly continue to be a key element of treatment options. Main advantages of surgical revascularization are not only the safety, predictability, and reliability, but more importantly the durability of its efficacy and the versatility that makes it applicable in various instances (total occlusion, near-septal origin lesions, diabetics, long-segment disease, calcific plaques, and so forth).
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References
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Abstract
Introduction
