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Ann Thorac Surg 2002;73:798-802
© 2002 The Society of Thoracic Surgeons
a Harefield Hospital, Uxbridge, United Kingdom
Accepted for publication October 15, 2001.
* Address reprint requests to Dr Amrani, Harefield Hospital, Uxbridge, Middlesex UB9 6JH, United Kingdom
e-mail: mr.amrani{at}rbh.nthames.nhs.uk
| Abstract |
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Methods. Data on our first 285 off-pump procedures using the Octopus system (Medtronic Inc, Minneapolis, MN) represent our learning curve. This is a complete experience in coronary bypass surgery over 16 months.
Results. The cohort was nonselected. All patients had at least two-vessel disease. Eight hundred seven grafts were performed (mean, 2.8 per patient) of which 647 grafts (84%) were arterial (mean, 2.3 per patient). One hundred seventy nine patients (63%) underwent total arterial revascularization. Eight patients required cardiopulmonary bypass; all other operations were completed off-pump. Complications were: mortality, 3 patients (1.5%); renal failure, 24 patients (8%); stroke, 2 patients (< 1%); and atrial fibrillation, 60 patients (21%). The morbidity data and frequency of arterial grafting did not differ from that of 355 patients who underwent coronary bypass operations in a preceding 18-month period.
Conclusions. Complete shift from routine use of cardiopulmonary bypass to nonselective off-pump coronary bypass operation is possible with a low conversion rate and without an apparent increase in morbidity or change in technique. Whereas short-term safety and efficacy seem certain, studies of long-term outcome are necessary before the eventual role of off-pump coronary bypass in myocardial revascularization can be defined.
| Introduction |
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| Material and methods |
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Operations were performed by median sternotomy initially using the Octopus 2 tissue stabilization system and then subsequently the Octopus 3 (Medtronic Inc, Minneapolis, MN). We prefer to perform the graft to the left anterior descending artery first and any circumflex grafts last. When a vessel was occluded and collateralized, we grafted the occluded vessel first. Deep pericardial verticalization sutures were used to aid circumflex exposure. Intracoronary shunts were selectively used in nonoccluded vessels. When intracoronary shunting was not used, the coronary artery was simply occluded distally and proximally using vascular bulldog clamps or occasionally plegetted 4-0 polypropylene snares. Shunts between the aorta and distal coronary artery or devices to improve right heart emptying were not used.
Our choice of conduits remained unchanged from our pre-OPCAB practice [1]. The left internal thoracic artery was the conduit of choice and was preferentially placed as a pedicle graft to the left anterior descending artery. The right internal thoracic artery preferentially was grafted to a circumflex artery as a pedicle through the transverse sinus. When the right internal thoracic artery was of insufficient length it was used as a free graft or connected as a pedicle to the left anterior descending artery (and the left internal thoracic artery was connected to the circumflex or used as a free graft to the circumflex). When use of a second internal thoracic artery was contraindicated (some insulin-dependent diabetics, previous radiotherapy, severe obstructive airway disease, or corticosteroid use), the radial artery was preferentially used for the circumflex graft. Otherwise the radial artery was placed on the right coronary system. No other arterial conduits were used. Sequential grafts or saphenous veins were used for additional grafts as required. The saphenous vein was also used if multiple arterial grafting was deemed to be of minimal marginal benefit (severe distal coronary artery disease, advanced age, and disease conditions limiting life-expectancy).
General anesthetic technique comprised low-intermediate dose opioid (usually fentanyl 8 to 15 µgkg-1) and a propofol infusion (3 mg/kg per hour). Some patients had thoracic epidural blockade using bupivicaine and fentanyl that was maintained for 24 to 72 hours postoperatively (depending on preference of the anesthesiologist). Standard intraoperative monitoring techniques were used. Additional monitoring was undertaken with transesophageal echocardiography. Pulmonary artery flotation catheters were not placed routinely. Heating mattresses and a warm airflow sheet on the lower half of the body were used to prevent excessive heat loss during the procedure. Anticoagulation was achieved using 150 units per kg of heparin. The activated clotting time was maintained at more than 250 seconds. Heparin was reversed with protamine at completion of the procedure. Cell-saving devices were not used routinely. Blood pressure was optimized during the procedure by means of repositioning the heart and selective use of vasoconstrictors. Other measures to improve cardiac output, such as elevation of feet and increasing the heart rate, were used as appropriate. Perfusionist standby was available for all patients. "Conversion" was defined strictly as the use of CPB at any stage during the treatment episode. For example, patients who arrested on induction of anesthesia, or who arrested on the intensive care unit and required CPB as part of resuscitative measure, would be classified as conversions. Patients who were converted at any stage during the operation (including prior to the onset of grafting) were also considered conversions. Criteria for intraoperative conversion to CPB were persistent hypotension (mean arterial blood pressure less than 50 mm Hg) ie, nonresponsive to pharmacological and surgical maneuvers and worsening arrhythmias related to ischemia.
Data were obtained from a prospective database held on all cardiac procedures done at our institution, with additional data obtained from a retrospective chart review. Comparisons were made with the pre-OPCAB practice of the same surgeon to ascertain if the practice changed with the adoption of off-pump CABG. Mortality was defined as in-hospital deaths and deaths within 30 days. Acute renal failure was defined as postoperative creatinine more than 2.0 mg per dL, regardless of need for dialysis; and stroke was defined as persistent or transient motor neurological deficit, regardless of cause.
| Results |
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| Comment |
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To be a true alternative to conventional CABG operations OPCAB operations should permit the same range of revascularization techniques as is possible using CPB and should be applicable to the majority of patients requiring CABG operations. A desire to avoid CPB should not result in compromise on the optimal revascularization procedure. Several approaches to minimally invasive CABG operations have emerged, including compromise on the number of grafts performed [2, 3], MIDCAB approaches applicable only to single vessel territories, hybrid procedures combining angioplasty with MIDCAB [4], target vessel revascularization, and videoscopic techniques. Although these techniques are useful additions to the surgeons repertoire for treating coronary artery disease, they are not true minimally invasive alternatives to conventional CABG operations because they cannot be applied to the majority of patients requiring CABG operations without compromising the extent or quality of revascularization. These concerns previously limited our interest in minimally invasive CABG operations. However with the advent of improved methods of heart stabilization, such as suction devices [5], off-pump revascularization of all coronary territories can be reproducibly performed. We did not define any criteria to exclude patients from OPCAB operations and have successfully maintained our practice of arterial revascularization despite routine use of OPCAB operations, thus fulfilling our objective of a true alternative to conventional CABG operations.
Several pioneering coworkers have reported the use of OPCAB techniques for arterial grafting. For example, in Jansen and coworkers series [6], 94% of 141 grafts were arterial; whereas Pym [7] used total arterial revascularization in 98% of 125 patients. However these studies differ from our series in which patients were selected from a larger group with the off-pump series representing less than 50% of their CABG practice. Most reports in the literature on off-pump CABG procedures suggest some form of patient selection and concern, either single-vessel MIDCAB or OPCAB operations utilizing saphenous veins for the majority of grafts. For example, Cartiers [8] series of 275 patients reported a mean of 2.9 grafts per patient that included an average of 1.82 vein grafts per patient. Some groups have specifically defined criteria for selecting patients for OPCAB operations [9]. Our belief has been that for an OPCAB operation to be a practical and widely applied technique, patient selection should be minimal. The absence of patient selection in our series is reflected in the average number of grafts per patient, mean age, and proportion of patients with impaired ventricular function, which mirrors that reported in the United Kingdom cardiac surgery registry [10]. This figure was also similar to that reported by Cartier [8] who also used the OPCAB procedure systematically for the majority (97%) of procedures. Patient selection or altered practice is evident in several published series as reflected by the lower number of anastomoses performed per patient (less than 2 per patient in some series). There is a concern that a bid to pursue OPCAB operations increases the rate of incomplete revascularization [11]. Recent evidence suggests that incomplete revascularization predisposes lower long-term survival and higher rates of reintervention [12]; if an OPCAB operation is applied it remains vital that complete revascularization is not compromised.
Even with strict definitions, our conversion rate was low (3%). We used a strict definition because it is the frequency of use of CPB in routine CABG operation practice that will determine the extent to which OPCAB operations can replace conventional CABG operations as the standard technique (assuming future studies do confirm OPCAB procedures are safe and have equivalent graft patency). If conversion rates of 1% or less can be achieved, then perfusionist standby may not be required for all patients, or alternatively, it may be possible to have a single perfusionist covering two or more concurrent procedures. Indeed, even at a conversion rate of 3%, the probability that 2 patients would need CPB simultaneously is 1 in 1,000; this would have large cost-saving implications, and it would also open up the possibility of selected CABG procedures being conducted in community hospitals with minimal perfusionist support. However we did note a high incidence of complications in the patients who required CPB. Although it is possible that these may have occurred even if the procedures were planned as on-pump (six of the eight conversions involved scenarios that also occur in patients having conventional CABG operations), we would caution against routine application of OPCAB operations if the intraoperative conversion rate is high because invariably there would have been undue insult to the heart and possibly other major organs, which may predispose to later morbidity and mortality.
We do not attempt to demonstrate superiority (or equivalence) of the OPCAB technique over conventional CABG operations, because to do so requires a controlled study, preferably randomized. Our study is limited by lack of medium-term follow-up and angiographic data. As part of our quality control, we performed early angiograms in 6 of the first 15 OPCAB patients and did not find any anastomotic failures. Further angiograms were not feasible in this cohort. Available evidence does however suggest that off-pump coronary artery operations generally yield early patency rates of 90% or more [13]. Longer follow-up is needed to determine if OPCAB operations have graft patency and recurrent cardiac event-free rates similar to those seen with conventional CABG operations. Any short-term benefits of avoiding CPB will only be relevant if OPCAB operations have similar long-term success compared with conventional CABG operations. Although there are suggestions of several short-term procedural benefits of OPCAB operations, such as early extubation, shorter intensive care, reduced blood use, and shorter hospital stay [1417], these benefits are not inherent in the OPCAB technique and can also be achieved with conventional CABG operations using modern management protocols. A reduction in short-term complications and a reduction in cost [18] will be the main arguments for adopting the OPCAB technique. Future studies will define the eventual role of OPCAB operations in coronary artery revascularization.
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