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J Thorac Cardiovasc Surg 1999;117:873-880
© 1999 Mosby, Inc.
SURGERY FOR ADULT CARDIOVASCULAR DISEASE |
From the Divisions of Cardiac Surgery, Sinai Hospital at Baltimore and Washington Adventist Hospital, Takoma Park, Md.
Received for publication May 14, 1998. Revisions requested July 13, 1998. Revisions received Dec 23, 1998. Accepted for publication Dec 30, 1998. Address for reprints: James D. Fonger, MD, Adventist Heart, 7610 Carroll Ave, Suite 440, Washington Adventist Hospital, Takoma Park, MD 20912.
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Abstract |
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 Top Abstract IntroductionPatients and methodsResultsDiscussionReferences |
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Introduction |
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TopAbstractIntroductionPatients and methodsResultsDiscussionReferences |
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1-4 MIDCAB techniques were developed in an effort to avoid some of the potential complications of conventional coronary artery bypass grafting by using smaller incisions, eliminating cardiopulmonary bypass, avoiding manipulation of the great vessels or of existing grafts, and using arterial conduits. Repeated sternotomy in particular has inherent risks, including injury to patent grafts, the heart, and great vessels; embolization of atherosclerotic debris from the aorta or diseased vein grafts; and subsequent wound complications. Conventional coronary artery bypass grafting in reoperative cases is associated with both prolonged cardiopulmonary bypass and increased operative times as a result of more extensive dissection.
This experience demonstrates that minimally invasive techniques that use the internal thoracic artery (ITA) can result in favorable early patient outcomes, reduce some of the morbidity associated with conventional coronary artery bypass grafting, and result in a more rapid recovery after the operation. Long-term outcomes, however, are necessary for a full evaluation of the value of the MIDCAB approach.
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Patients and methods |
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TopAbstractIntroductionPatients and methodsResultsDiscussionReferences |
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An 8-cm transverse skin incision was made at the level of the fourth costal cartilage, just lateral to the sternal border. In male patients the incision was located above the nipple; in female patients the incision was placed just above the submammary fold. The fourth cartilage was released just lateral to the ITA and reflected inferiorly, or removed in early cases. Exposure was optimized by means of a conventional retraction system (Rultract, Inc, Cleveland, Ohio) to simultaneously elevate the third cartilage and the sternal table. The ITA was dissected off the chest wall and skeletonized from the undersurfaces of the first through fifth costal cartilages to ensure a tension-free anastomosis for left anterior descending coronary artery (LAD), left anterior descending diagonal coronary artery (LADD), and proximal right coronary artery (RCA) targets.
The pericardium was opened longitudinally over the intended target vessel and 10,000 units heparin was administered intravenously. Silicone elastomer retraction tapes (Quest Medical, Dallas, Tex) were passed around the native coronary artery proximal and distal to the site of intended grafting. Heavily diseased coronary targets were not occluded distally to prevent luminal plaque fracture. One to three 5-minute cycles of ischemic preconditioning were performed as required to confirm stable hemodynamics.
An arteriotomy was fashioned in the target vessel and the conduit was prepared for grafting. Probing of the distal target vessel was avoided because this may result in vessel wall dissection or disruption of plaque when performed on a nonarrested heart. The arteriotomy site was stabilized with a handheld right-angle clamp with rubber bolsters. The conduit was anastomosed end to side in an antegrade fashion with a 7-0 polypropylene single parachute suture technique. Intraoperative graft flow was measured after completion of the anastomosis with a transit-time ultrasonographic flow probe (Transonic Systems, Inc, Ithaca, NY) to assist in detection of technical problems with the anastomosis before closure. After completion of the anastomosis the ITA pedicle was secured to the epicardium to ensure proper orientation. A small suction drain (Hemovac; Zimmer Patient Care Division, Dover, Ohio) without underwater seal was placed across the open pericardium and into the pleural space. The fourth costal cartilage was secured to the sternum with a single sternal wire, and a lateral intercostal block was placed with 0.5% bupivacaine hydrochloride (INN: bupivacaine) with epinephrine. The muscle and soft tissue were closed in layers and the drain was secured to the skin.
Patient follow-up
Routine systematic serial cardiac enzyme analyses were performed at 1 hour, 8 hours, and 16 hours after the operation in all cases, and additional analyses were performed as indicated. Patients were followed up prospectively after the operation with clinic visits at 2 weeks of follow-up, at 3 months of follow-up, and then annually. Transcutaneous Doppler velocimetric evaluation was performed at 2 weeks, 3 months, and 1 year to assess graft patency. Exercise thallium stress testing was performed at 3 months to evaluate improvement in myocardial perfusion in the grafted distribution. Coronary angiography was performed selectively for persistent or recurrent anginal symptoms, for failure to visualize the graft on subsequent outpatient Doppler velocimetric evaluation, or for a significant persistent ischemic defect on postoperative thallium stress testing.
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Results |
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TopAbstractIntroductionPatients and methodsResultsDiscussionReferences |
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Twenty-two (13.6%) patients had atrial fibrillation or supraventricular tachycardia develop during the postoperative period; 20 of the episodes occurred before discharge. Three (1.9%) patients had stroke or other significant neurologic impairment. The first patient died 2 weeks after the operation, after development of a stroke during hospitalization for pneumonia at another institution. The second patient had left-sided weakness several hours after discharge on the sixth postoperative day; this subsequently resolved. The third patient had symptoms consistent with transient cerebral ischemia on postoperative day 2; these symptoms resolved spontaneously.
Twenty-four patients (14.8%) had inflammation or infection develop at the primary operative site. Six patients (3.7%) had infections that necessitated operative débridement or revision of the incision. The remaining 18 patients with infections had inflammation or minor infections treated in the clinic with dressings or antibiotics. Most of these wound complications occurred in patients with submammary incisions. No patient had sternal infection or evidence of mediastinitis.
Three patients (1.9%) required surgical reexploration. The first patient was returned to the operating room twice on the day of operation for bleeding; no site was found at either exploration. A second patient had acute graft occlusion immediately after the operation; reexploration was performed and the graft was revised. This patient sustained a postinfarction ventricular septal defect despite these measures, as described previously. A third patient had early postoperative electrocardiographic changes that were treated urgently with angioplasty of the native LAD. Reexploration the next morning revealed graft compression by the migrated lateral edge of the pericardium; release of this impingement restored normal graft flow.
Fifteen patients (9.3%) required thoracentesis, chest tube placement, or both for pleural effusion after MIDCAB grafting. Eight of the patients required this intervention before their discharge from the hospital and in 7 patients the pleural effusion necessitating thoracocentesis developed after their discharge.
Conversion to conventional bypass grafting
Ten patients (6.2%) required conversion to conventional coronary bypass grafting. Seven of these patients had primary left ITA (LITA) to LAD grafting, 1 patient had reoperative LITA to LAD grafting, 1 patient had primary bilateral ITA grafting to the LAD and RCA, and 1 patient had primary right ITA to RCA grafting. Indications for conversion to conventional coronary artery bypass with cardiopulmonary bypass included hemodynamic instability in 4 cases, arrhythmia in 2 cases, inadequate exposure in 2 cases, ITA dissection in 1 case, and excessive bleeding in 1 case.
Five patients (3.1%) underwent full sternotomy without cardiopulmonary bypass. Three of these patients underwent primary ITA grafting and 2 underwent reoperative grafting. Two of the patients required a full sternotomy because of inadequate exposure for grafting through the MIDCAB incision. One patient required a full sternotomy during reexploration for bleeding.
Length of stay
Mean overall postoperative length of stay for all patients was 2.5 days (range 0-27 days). Mean overall length of stay for all patients except those who died while in the hospital was 2.2 days (range 1-12 days).
Recatheterization and reintervention
Twenty-seven patients (16.7%) underwent postoperative recatheterization for symptoms, for inadequate graft flow according to Doppler velocimetric evaluation, for persistent defect according to thallium stress testing, or during a planned procedure on another vessel (Table IV). Fourteen patients had normal grafts and 2 had progression of native coronary vessel disease at other locations. Nine patients (5.6%) required reintervention for stenotic or occluded grafts. Kaplan-Meier analysis values for freedom from reintervention were 95% (95% CI, 91%-98%) at 12 months and 92% (95% CI, 82%-96%) at 24 months (Fig. 2).
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Four patients (2.5%) had graft stenoses develop. One patient had graft impingement by the pericardial edge, as described previously. Two patients had non–flow-limiting narrowings in the graft that did not require reintervention. A fourth patient had a reversible ischemic defect according to follow-up thallium stress testing 18 months after the operation. Recatheterization showed stenosis of the ITA graft, and a stent was successfully placed. Three patients (1.9%) had anastomotic stenoses; all stenoses occurred within 3 months after the operation and were successfully dilated with percutaneous methods.
Follow-up
Intraoperative graft flow assessed by transit-time ultrasonography averaged 23.8 mL/min (range 1-70 mL/min). Postoperative transcutaneous Doppler velocimetric analyses of the ITA graft were performed in 138 cases (85.2%). Three patients had evidence of decreased flow in the conduit, 2 at the 2-week examination and 1 at the 5-week examination. The former 2 patients were both free of symptoms, and recatheterization was not performed. The latter patient had graft occlusion on recatheterization, as described previously. Doppler velocimetric analyses were performed in 122 cases at 2 weeks of follow-up, in 109 cases at 3 months, and in 60 cases at 1 year. Three patients have had Doppler velocimetric evaluations at 2 years of follow-up; all have evidence of patent grafts.
Thallium stress testing was performed in 106 cases (65.4%) at 3 months of follow-up. Nineteen patients were found to have a persistent reversible ischemic defect, although all grafts evaluated by Doppler velocimetric study demonstrated flow. Ten of these patients underwent recatheterization, 1 had graft occlusion, 2 had anastomotic stenoses, and 2 had native vessel stenoses, as described in detail previously.
One hundred forty-one (95.9%) of 147 surviving patients were evaluated for symptoms during clinic visits at 2 weeks of follow-up, at 3 months of follow-up, and then annually. Of these, 6 (4.1%) had persistent symptoms and 5 (3.4%) required additional medical therapy to relieve their anginal symptoms. Antegrade flow of the ITA conduit was documented by Doppler velocimetry in 135 (97.8%) of 138 patients studied. One hundred thirty-five (95.7%) of 141 patients seen in the clinic had resolution of their symptoms either with or without additional medical therapy.
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Discussion |
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TopAbstractIntroductionPatients and methodsResultsDiscussionReferences |
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5-10 This knowledge was applied to MIDCAB procedures early in the development of minimally invasive techniques because the LITA lends itself well to this approach.
This series of patients represents the initial experience with MIDCAB grafting performed with early exposure techniques and without currently available automated mechanical stabilization. In addition, a selective approach for recatheterization was employed, which is an inherent weakness of this report. Nevertheless, this experience is comparable to other published reports of MIDCAB grafting with the ITA conduit. Calafiore and associates 3 have reported on the largest series to date (n = 155 patients) of use of the LITA to graft the LAD, with excellent mortality and patency rates, and other, smaller series have also demonstrated encouraging early results. 1,2,4,5 In this series most (7/9) graft stenoses or occlusions necessitating reintervention occurred within 3 months after the operation. The 3-year follow-up suggests that these conduits behave as would be expected after successful graft placement with conventional coronary artery bypass techniques.
MIDCAB grafting with the ITA has been demonstrated in some series to carry low attendant early mortality and perioperative infarction rates. In this set of patients all early deaths were restricted to patients older than 70 years, and 3 of the 8 deaths were of patients who underwent reoperation. This suggests that MIDCAB grafting with the ITA can be most effectively employed in young, otherwise healthy patients with single-vessel disease. In contrast, elderly patients with significant comorbidities and patients undergoing reoperative procedures, who are at higher risk with conventional coronary artery bypass, did not have a reduced risk with MIDCAB in this series. Earlier studies among patients undergoing conventional coronary artery bypass procedures examined the role of ITA grafting in elderly patients and did not associate the use of the ITA graft with an increased mortality rate among these patients. 8,10 However, a recent study by He and associates 11 of patients undergoing conventional coronary artery bypass grafting demonstrated that use of the right ITA and reoperation were among the risk factors associated with increased early mortality rates among elderly patients receiving ITA grafts. It is unclear from this series why the MIDCAB approach did not reduce the operative risk in this subset of patients.
The MIDCAB approach was effective in reducing some of the common postoperative complications that are associated with conventional coronary artery bypass grafting. There was a low rate of supraventricular arrhythmia (13.6%), with most (20/22) cases occurring before discharge. There was a small but important percentage of patients (9.3%) who required thoracentesis, chest tube placement, or both for pleural effusion. Nearly half of these patients had their effusion after discharge from the hospital or required multiple thoracocenteses for recurrent effusion. Both complications underscore the importance of close follow-up because arrhythmia or effusion may develop after the patient has been discharged.
MIDCAB grafting with the ITA did not substantially reduce the incidence of central nervous system events (1.9%), as indicated by the 3 patients who had neurologic injury. These injuries occurred despite the avoidance of manipulation of the great vessels and cardiopulmonary bypass. The causes of these events are unclear because none occurred within 48 hours after the operation and none were readily attributed to perioperative phenomena.
MIDCAB grafting was associated with a high rate of wound inflammation or infection (14.8%) in this series of patients, although most of these complications were minor. Most of these infections were associated with the submammary incision. This association prompted modification to place the incision 1 cm above the inframammary fold and to avoid its use in patients with diabetes and those with particularly pendulous breast tissue. Importantly, none of these infections resulted in sternal infection or mediastinitis, and most patients required only simple drainage and antibiotics.
Experience with right ITA and bilateral ITA grafting is accumulating in the MIDCAB setting and further extends the range of the minimally invasive approach. Right ITA grafting in conventional coronary artery bypass has had excellent patency rates when grafted to the LAD but is also useful in patients without venous conduits and in isolated proximal RCA disease. 12,13 Combined bilateral right and LITA grafting in conventional coronary artery bypass procedures has been shown to carry good long-term survival and improvement in functional status; it is unclear whether bilateral ITA grafting increases surgical risk or infection rates among these patients. 14-17 Four patients in this series underwent bilateral ITA grafting to the LAD and RCA. No patient had wound infection, and 1 patient died 3 weeks after the MIDCAB procedure of a pulmonary embolus after a hip replacement operation. These anecdotal results confirm the case report by Watanabe and associates 18 and suggest further investigation into this technique.
In conclusion, MIDCAB grafting with the ITA is a versatile operation that results in excellent relief of patients' symptoms. Early mortality rates were not as low as anticipated, however, particularly in the subset of patients considered to be at higher risk when undergoing conventional coronary artery bypass grafting. The ITA can be used for isolated grafting of anterior coronary vessels or for more extensive grafting procedures, including sequential grafting and bilateral ITA grafting. MIDCAB grafting with the ITA reduces the incidence of postoperative supraventricular arrhythmia and reduces postoperative length of stay, allowing patients to return to normal activity much sooner than does conventional coronary bypass grafting. Long-term followup continues to confirm the durability of ITA grafts placed with MIDCAB techniques.
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References |
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TopAbstractIntroductionPatients and methodsResultsDiscussionReferences |
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