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Ann Thorac Surg 2006;81:1249-1255
© 2006 The Society of Thoracic Surgeons
a Department of Cardiothoracic Surgery and Anesthesiology, Karolinska University Hospital, Solna, Sweden
b Department of Cardiology, Karolinska University Hospital, Solna, Sweden
c Department of Clinical Physiology, Karolinska University Hospital, Solna, Sweden
Accepted for publication November 21, 2005.
* Address correspondence to Dr Jönsson, Karolinska University Hospital, Department of Cardiothoracic Surgery and Anesthesiology, SE-171 76 Solna, Sweden (Email: anders.l.jonsson{at}karolinska.se).
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Abstract |
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METHODS: Forty-three patients were operated on with LMCA angioplasty from 1997 to 2003. Follow-up at a mean of 45 months (range, 7 to 79) included a stress test, echocardiography, and angiography with intravascular ultrasound (IVUS) of the LMCA.
RESULTS: There were three late deaths, none related to failure of the angioplasty. All patients included in the follow-up had preserved preoperative left ventricular function, and there was no aortic incompetence. The angioplasties investigated were patent, and no signs of restenosis or dilatation could be observed. The dimensions of the LMCA after angioplasty was in diameter 4.8 mm (3.35 to 6.75 mm) and 5.6 mm (4 to 7.6 mm), and in area 18.9 mm2 (12.3 to 31.9 mm2) and 24.8 mm2 (14.5 to 37 mm2) in the distal and proximal parts, respectively.
CONCLUSIONS: Surgical angioplasty of the left main coronary artery using a proximal segment of the right internal mammary artery as an onlay patch is safe, with good long-term results.
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Introduction |
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TopAbstractIntroductionPatients and MethodsResultsCommentAcknowledgmentsReferences |
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Left main surgical angioplasty is controversial, despite the reported good results, possibly because coronary artery bypass grafting is a well-established and safe treatment for patients with LMCA stenosis [1, 2]. The long-term results of angioplasty have been questioned as restenosis has been observed [3–7].
When performing surgical angioplasty of the LMCA, we have consequently used the proximal segment of the right internal mammary artery (IMA) as an onlay patch for reconstructing the obstructed left main coronary artery, assuming that the beneficial characteristics of the IMA documented after conventional coronary artery bypass surgery would translate into good long-term patency using this vessel wall as a patch material [8, 9]. The aim of this study was to present the clinical results and follow-up findings at angiography and intravascular ultrasound (IVUS) after angioplasty of the LMCA.
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Patients and Methods |
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There were 21 female patients (49%), and average age was 59 years (range, 33 to 79). Body mass index was 26 ± 3.5 kg/m2. Twenty-one patients (49%) had hyperlipidemia, 11 (26%) had hypertension, and 5 (12%) had diabetes mellitus. There was a history of an old myocardial infarction in 9 patients (21%), and 10 (23%) had unstable angina.
Left ventricular function was good, with a left ventricular ejection fraction (LVEF) more than 60% in 37, moderately impaired (LVEF 40% to 60%) in 4, and poor (LVEF < 40%) in 2 patients.
One patient had a combined aortic valve lesion, and 1 patient also had severe mitral valve regurgitation and an atrial septal defect. Eight patients had preoperative atrial fibrillation (3 paroxysmal and 5 chronic). All patients included gave their informed and written consent to participate in the study, which was approved by the Karolinska Hospital Local Ethics Committee (1997-06-07).
Catheterization Data
A significant LMCA stenosis (luminal diameter narrowed more than 50%) was present in all 43 patients. Twenty-five patients (58%) had concomitant coronary artery branch obstruction. Twenty had a significant stenosis in one peripheral coronary vessel (LAD in 9 and RCA in 11 patients), and in 5 patients there were stenoses in two distal vessels (LAD and Cx in 1 and LAD and RCA in 4 patients). Among the patients with a RCA stenosis, 8 had osteal lesions. Patients with concomitant LAD stenosis underwent LMCA angioplasty and coronary artery bypass only if the LAD stenosis was peripheral.
Patients selected for angioplasty had three different type of LMCA lesions: ostial, if the narrowing was exclusively located at the aortic ostium not involving the rest of the LMCA; midshaft, if the narrowing was located in the middle part of the LMCA distal to the ostium and proximal of the bifurcation of the LAD and circumflex artery; and circular, if the entire LMCA was diseased from the ostium, reaching but not involving the bifurcation [10]. The LMCA classification and other angiographic findings are presented in Table 1.
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In the first 12 patients, we used the posterior approach and technique described by Hitchcock and associates [11] and Ridley and Wisheart [12]. Endarterectomy was never performed. The IMA was longitudinally divided, and trimmed to fit the incised LMCA and the extension out in the aortotomy of approximately 1 of 1.5 cm. The IMA onlay patch was sutured to LMCA and free aortic wall with a continuous 6-0 Prolene suture (Ethicon, Sommerville, NJ); the remaining aortotomy was sutured with 4-0 Prolene. Angioplasty of the RCA was performed through a vertical incision in the aortic wall; the incision was further extended approximately 1.0 to 1.5 cm into the proximal RCA. An onlay IMA patch was then sutured into place as described above.
In the last 31 patients, our previously described technique [8] was used, the aortic transsection technique, where the ascending aorta is completely transected approximately 1 cm above the commisures and the pulmonary trunk retracted in a leftward direction. By the discontinuation of the ascending aorta, the aortic root can easily be mobilized in an anterior direction, and thereby excellent exposure of the LMCA obtained. An incision is carried out through the aortic wall extending obliquely into the roof of the LMCA. An IMA patch is sutured into place to the level of the transverse aortic transsection. The aortotomy was closed with 4-0 Prolene. Mean aortic cross-clamp time was 91 minutes (range, 46 to 162), and mean cardiopulmonary bypass time was 120 minutes (range, 61 to 218). The patients' mean preoperative bleeding was 578 mL (range, 150 to 1,600 mL). Two patients had concomitant valve replacements, 1 patient receiving a 29-mm Carbomedics mitral valve prosthesis (model 700) and the other, a 21-mm Carbomedics aortic valve prosthesis (model R 500) (Carbomedics, Austin, TX), and in this patient, an ASD repair was also performed. Two patients underwent Cox MAZE 3 procedures. Additional bypass grafts were inserted in 21 patients (49%). There were 26 distal anastomosis, and the LIMA was used in 14 and the RIMA as a free graft in 5 patients.
Postoperative Protocol
Initially, all patients were examined with coronary angiography postoperatively, but as our experience grew and we became more confident with the procedure, angiography was only done when the surgeon was in doubt about the operative result.
Another abandoned routine was the antithrombotic regime, consisting of sodium warfarin for 2 months postoperatively and dalteparinsodium (Fragmin; Pharmacia-Upjohn, Stockholm, Sweden) 5,000 IU per day, until the therapeutic level of sodium warfarin was obtained. Instead, a daily dose of 160 mg acetylsalicylic acid was started immediately postoperatively and recommended as a life-long regimen if tolerated by the patient.
Follow-Up
Thirty-six patients underwent a stress test on an ergometer bicycle and were examined with transthoracic echocardiography to determine systolic and diastolic ventricular function, assess any valvular incompetence, and determine the dimension of the aortic root.
Thirty-three patients were examined with angiography, and in 30 of these patients, IVUS of the LMCA was performed. Intravascular ultrasound was used to assess the LMCA in as many patients as possible, as it is known that angiographic investigation of a left main coronary artery stenosis can be unreliable [13, 14].
Angiography and Intravascular Ultrasound Protocol
After an angiography had been performed with standard multiple projections using a 5F diagnostic catheter, the LMCA was engaged with a 6F guiding catheter. After administration of weight-adjusted low molecular weight heparin and intracoronary nitroglycerin, a guide wire (BMW; Guidant, Indianapolis, IN) was positioned distally in the coronary vessels, and the guiding catheter was slightly retracted from the ostium of the LMCA.
Intravascular ultrasonography of the LMCA was then performed with an IVUS imaging catheter (Eagle Eye; Volcano Therapeutics, Rancho Cordova, CA). Ultrasound images were recorded after initiation of automated pullback at 0.5 mm/s, starting at a point distal to the bifurcation of the LAD and Cx, and then the entire LMCA was imaged in retrograde fashion to the aorto-ostial junction. All studies were recorded for offline analysis.
The IVUS images were reviewed and analyzed for quantitative parameters by two independent interpreters using In-Vision View (MediMatic, Genova, Italy). The measured vascular dimensions of the LMCA consisted of area and diameter in the same transversal cross-section in the distal, mid, and proximal portions. The length of the patched LMCA was also measured in a longitudinal cross-section.
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Results |
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TopAbstractIntroductionPatients and MethodsResultsCommentAcknowledgmentsReferences |
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In 1 patient with a stenosis involving the entire LMCA, the surgeon encountered calcifications reaching the distal bifurcation of the LAD and Cx not visible on the preoperative angiography. The angioplasty was completed, and the patient had an uneventful early postoperative course. Because of the peroperative findings and a suspicion of a narrowing still present distal to the angioplasty, this patient had a postoperative angiography. Notably, the angiography failed to visualize the distal LMCA stenosis, which was verified using intracoronary pressure measurements demonstrating a fractional flow reserve of 0.71, thus indicating a significant coronary artery stenosis [15, 16]. This patient was reoperated on with conventional coronary artery bypass technique, receiving a LIMA to the LAD and a saphenous vein graft to the Cx. The postoperative course was uneventful, and the patient was discharged from hospital a week later.
Late Results
Average follow-up was 45 months (range, 7 to 79). Of the 43 operated on patients, 3 patients were dead and 1 was lost to follow-up. Only 1 of the 39 patients who were contacted postoperatively had symptoms of angina pectoris. Six patients did not consent to reangiography. There was 1 death from malignancy and 2 from cardiac causes. One of the patients who sustained a wound infection was readmitted 4 months after discharge with prosthetic valve endocarditis and underwent reoperation. This patient died after 1 month because of continuous prosthetic mitral valve endocardits with dehiscence of the prothesis. A second patient was angina free with a normal stress test before discharge, but died suddenly after 17 months; at autopsy, the bilateral angioplasties were without signs of restenosis or dilatation.
Exercise Capacity
Of the 39 restudied patients after LMCA angioplasty, 36 patients consented to a maximal stress test. None was left with residual ischemia, but 1 patient had pathologic electrocardiographic changes and chest pain. The maximum working capacity was 140 Watts (60 to 250 Watts).
Echocardiographic Evaluation
The 36 patients had preserved preoperative ejection fraction, and dilatations of the aortic root or significant aortic incompetence could not be seen.
Angiographic Evaluation
In 33 patients, the LMCA angioplasty was restudied with an angiography in the late follow-up. All the angiographies demonstrated excellent results of all the LMCA angioplasties. One angiography revealed a significant LAD stenosis, in the same patient who had angina and residual ischemia on the stress test. This patient underwent percutaneous coronary intervention, and the LAD stenosis was successfully dilated and stented. Figure 1
illustrates a preoperative angiographic image of a circular LMCA lesion, and Figure 2, the same lesion after angioplasty.
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The IVUS demonstrated excellent angioplasty patency without signs of restenosis or dilatation of the patch. The IVUS assessment of the LMCA in the patient who had an early reoperation demonstrated no restenosis in the patched LMCA but heavy calcifications in the entire vessel and a significant stenosis in the very distal part.
The vascular dimensions of the 29 successful LMCA angioplasties evaluated with IVUS are demonstrated in Table 2. The length of the LMCA in these patients were 9.8 ± 4.2 mm (3.2 to 21.4 mm). Figure 3 demonstrates an IVUS image of a transversal cross-section of the LMCA after angioplasty.
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Comment |
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TopAbstractIntroductionPatients and MethodsResultsCommentAcknowledgmentsReferences |
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Patients with stenosis of the LMCA have a poor prognosis if left untreated [17, 18]. Conventional coronary artery bypass surgery is recognized as the treatment of choice. Subsequent progression of the LMCA stenosis may lead to complete LMCA occlusion [19–24].
An alternative surgical technique in selected patients is left main coronary artery surgical angioplasty with reconstruction of the proximal segment of the left main coronary artery. The selection of patients is crucial to avoid unnecessary complications. Suitable candidates usually have well-defined osteal or midshaft noncalcified lesions, representing the majority of patients in this study. As we have become more confident with the procedure, we have included patients in whom the entire LMCA was diseased, and also accepted visible minor calcifications on the preoperative angiography. Stenosis of the LMCA is found in approximately 9% to 14% of the patients undergoing coronary artery bypass surgery, and we have previously declared that 22% of patients with LMCA stenosis could be possible candidates for angioplasty [10].
Surgical angioplasty of the LMCA restores normal antegrade flow and perfusion. In our series of patients undergoing angioplasty of the LMCA, several patients also received a left internal mammary anastomosis to a separate distal LAD stenosis. An alternative to LMCA angioplasty for these patients would, of course, have been a coronary bypass graft to the circumflex artery; however, we considered a LMCA angioplasty as a better option with respect to long-term patency. These patients will accordingly also be better accessible for percutaneous coronary intervention if distal coronary stenoses develop in the future.
The early experiences of surgery on the LMCA involved endarterectomy and onlay patch angioplasty with reported high mortality rate and frequent thrombosis and restenosis at the site of reconstruction [25, 26]. As better techniques for myocardial protection and cardiopulmonary bypass evolved, Hitchcock and coworkers [11] revived and modified the angioplasty procedure of the LMCA with good results. Dion and colleagues [3] have further refined the procedure, reporting the largest series with a follow-up of 47 patients; and an increasing number of surgeons, including our team, have been encouraged in performing surgical angioplasty using different approaches and patch material, and presenting good results [4, 5, 8, 12, 27–37].
Despite the theoretical advantages of surgical angioplasty of the LMCA, it is considered somewhat controversial. A possible explanation is that it is regarded as a more taxing procedure, and that, as a surgeon, you will not be able obtain the same amount of exposure to it as conventional coronary artery bypass grafting, which is an excellent and safe surgical treatment. Another question concerning angioplasty of the LMCA has been the reported for cases of restenosis documented on angiography. In a review by Malyshev and colleagues [31] of all articles published with results of surgical angioplasty since 1983, the restenosis rate was 3.4% when autologous vein was used as patch material and 4.9% when autologous pericardium was used [31]. In our series of patients with the IMA as onlay patch, we have not found any patients with restenosis.
We have routinely used a segment of the proximal right mammary artery as a patch. The rationale for this has been that the IMA better resembles coronary arteries with respect to histologic, physiologic, and fibrinolytic properties than autologous pericardium or the saphenous vein [38–40], and this could possibly reduce the incidence of restenosis and thrombus formation. After initially using the posterior technique in 12 patients, we have consequently used an approach where the ascending aorta is transected just distal to the commissures, offering excellent exposure and visualization of the entire LMCA, including the bifurcation of the LAD and circumflex artery (Fig 4A–D).
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Echocardiography was done to exclude possible aortic root dilatation or aortic valve incompetence inflicted by the angioplasty and neither was seen in any of the patients.
We used angiography with IVUS in as many patients as possible when assessing the LMCA angioplasty. Intravascular ultrasound offers a better definition of the vascular dimensions and can better determine any pathology such as restenosis, dilatation, or calcification present in the LMCA. All angioplasties in this follow-up were patent and free of the above-described pathology, with calcifications limited to the native LMCA wall.
In conclusion, LMCA surgical angioplasty using the proximal segment of the right IMA as an onlay patch is safe, with excellent long-term results.
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Acknowledgments |
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TopAbstractIntroductionPatients and MethodsResultsCommentAcknowledgmentsReferences |
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References |
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TopAbstractIntroductionPatients and MethodsResultsCommentAcknowledgmentsReferences |
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  H. B. Barner Invited commentary Ann. Thorac. Surg., April 1, 2006; 81(4): 1255 - 1255. [Full Text] [PDF]
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