Use of the PercuSurge GuardWire® Distal Balloon Occlusion System as an Endovascular Clamp during Off-Pump Coronary Bypass Surger

Off-pump coronary bypass surgery has emerged as an alternative to conventional coronary bypass surgery (CABG) in recent years. This involves the creation of an anastomosis on a normothermic, beating heart while blood flows down partially occluded coronary arteries. Off-pump CABG avoids many of the complications of cardiopulmonary bypass and may reduce the risk of cerebral embolization.¹ No definitive mortality benefit or consistent reduction in long-term cognitive impairment, perioperative myocardial infarction (MI), or overt stroke have been clearly documented with this technique. However, several studies have demonstrated reduced myocardial necrosis with off-pump CABG, as evidenced by less postprocedural increases in CK-MB and troponin.^1–5 Cardiopulmonary bypass precipitates a complex systemic inflammatory response after cardiac surgery, mediated by neutrophil migration and endothelial binding. Off-pump CABG is associated with less endothelial activation, as reflected by lower postoperative levels of soluble inflammatory adhesion molecules such as P-selectin. Lower levels of adhesion molecules correlate well with the lower levels of CK-MB observed.⁵ In addition, randomized data have demonstrated a reduction in postoperative atrial fibrillation, transfusion requirements, time to extubation and length of hospital stay following off-pump revascularization. Consequently, off-pump CABG has been increasingly used in patients with multiple comorbidities who are otherwise unable to tolerate the physiologic stress of traditional cardiopulmonary bypass with the heart-lung machine. Of interest, off-pump procedures are especially attractive in the setting of a hybrid operating room/cardiac catheterization laboratory where LIMA-to-LAD anastomoses can be performed on a beating heart with angiographic guidance, while less accessible vascular territories can be revascularized percutaneously in the same setting. Despite great initial enthusiasm, off-pump procedures have not emerged as the standard of care at most institutions. Moreover, complications of off-pump surgery may arise, given its technical difficulty. In addition to the difficulty of suturing the graft onto a moving, albeit partially stabilized target, the surgeon’s view is not infrequently obscured by blood in the operative field from partially perfused coronary arteries. There are two commonly used strategies to reduce blood flow following coronary artery incision. The first involves snaring the coronary vessel with elastic sutures to occlude flow. The second involves insertion of an intracoronary shunt, which isolates the anastomotic segment while maintaining perfusion to the distal vessel. In addition, due to incomplete isolation with each of these methods, CO2 gas is blown onto the open vessel to evacuate residual blood. Attempts to temporarily occlude this blood flow by snaring the vessel with an elastic suture may cause myocardial ischemia, and can lead to hemodynamic instability. Notably, both methods also pose a risk of endothelial injury, plaque rupture, atheroma embolization or vessel dissection. Both animal and human studies have demonstrated visible endothelial injury and inflammatory cell adherence following coronary clamping and gas insufflation.^6,7 While these effects can be partly ameliorated by the use of elastic sutures and humidified gas, injury is not eliminated. Intracoronary shunt insertion, which is attractive due to the operator’s ability to maintain distal vessel perfusion, has been compared with coronary snaring. This technique has been shown to cause more severe endothelial damage, often with trauma into the smooth muscle cell layer, which was visible by scanning electron microscopy and multiphoton fluorescence imaging.^8,9 In one study, functional viability was also diminished with reduced nitric oxide generation, intracellular calcium mobilization and esterase activity.⁹ Potential consequences of endothelial or plaque disruption include vessel dissection, abrupt closure and an increase in the predisposition to thrombosis in the short term, and neointimal hyperplasia and stenosis in the long term. We hypothesized that the use of a modified intravascular balloon occlusive device could be used in the hybrid operating room/cardiac catheterization laboratory setting to optimize surgical results while reducing potential complications. We present two cases during which modern endovascular interventional techniques were used to facilitate construction of an off-pump LIMA-to-LAD anastomosis. Case Presentations Patient 1 is a 50-year-old diabetic male who presented with a non-ST-elevation myocardial infarction. He underwent coronary angiography which showed severe proximal LAD disease (Figure 1). He was referred for off-pump LIMA-to-LAD grafting, which was performed in the Vanderbilt University Medical Center hybrid operating room/catheterization laboratory. Following successful LIMA harvesting, his left main artery was engaged with a 6 Fr EBU 3.75 guide catheter. Two PercuSurge GuardWires® (Medtronic, Inc., Minneapolis, Minnesota) (Figure 2A) were inserted into the mid and distal LAD. The GuardWire balloons were positioned 15–20 mm proximal and distal to the planned anastomotic site, which was marked by the surgeon with a surgical clip. The balloons were then sequentially inflated to occlude antegrade and retrograde collateral flow to isolate the anastomotic segment (Figure 3). The LIMA distal anastomosis to the LAD was performed in a bloodless field in the standard fashion using a Guidant (Indianapolis, Indiana) off-pump stabilizing system (Figures 2 B–C). At the completion of the anastomosis the GuardWire balloons were deflated and removed. Post-bypass angiography demonstrated no LAD trauma or dissection and a widely patent LIMA to the mid LAD (Figure 4). There were no complications in the postoperative period. Patient 2 is a 62-year-old male with multiple comorbidities, including multiple prior angioplasties and stent placements, as well as mild chronic renal insufficiency (baseline creatinine 1.6) and chronic immunosuppression post-liver transplantation. The patient presented with recurrent angina and was found to have a 60% left main stenosis and a 50% proximal LAD stenosis. He was referred for an off-pump LIMA-to-LAD graft with intended postoperative lateral wall stenting. This case was also performed in the Vanderbilt University Medical Center hybrid operating room/catheterization laboratory. Endovascular clamping of the mid LAD anastamotic site was performed in the aforementioned fashion without complication. The left main and left circumflex arteries were successfully stented immediately after off-pump LIMA-to-LAD surgery. Discussion. The cases presented here illustrate the use of an FDA-approved embolic protection device as a vascular clamp during off-pump CABG in a hybrid operating room/catheterization laboratory. While the PercuSurge device has been proven to reduce the risk of embolization in saphenous graft PTCA and stenting,¹⁰ it has also been demonstrated to be safe for use in a native coronary.¹¹ The device consists of a coronary guidewire with a compliant (low-pressure) elastomeric balloon at the tip. The balloon is inflated by infusion of contrast down a hollow wire core. This maneuver occludes arterial blood flow for better operative visualization. Of significance, this form of endovascular clamping provides several potential advantages over traditional operative snaring or shunt insertion. First, the anastomotic site can be more accurately identified by the surgeon since the GuardWire balloons are carefully positioned at the ideal target under direct angiographic guidance. By conventional methods, the targeted vessel, when viewed from its exterior by the surgeon, can be difficult to correlate with an angiogram. As such, it becomes problematic for the surgeon to precisely identify where to make the best anastomosis. Angiographic guidance avoids the potential mistake of suturing a graft near areas of heavy plaque burden or even proximal to an otherwise unvisualized significant lesion. Second, the balloons are inflated with very low pressure (6–9,12 There have also been well publicized cases of surgeons erroneously grafting the wrong vessels with severe adverse consequences. On occasion, we have performed angiograms of LIMA conduits anastomosed at sites of significant stenosis into false lumens of dissection planes, or even to diagonal side branches when the intended target was the LAD. Endovascular clamping with appropriate postprocedural imaging has the potential to avoid most, if not all, of these complications. While currently available endovascular devices occlude flow to the distal vessel, more advanced devices with a perfusion channel can be developed. In conclusion, beating-heart surgery avoids the use of cardiopulmonary bypass and has been shown to reduce several markers of perioperative morbidity. Off-pump coronary bypass surgery has been slow to emerge as the standard of care due to increased difficulty in anastamotic construction and potentially suboptimal results.¹³ Consequently, these procedures are ideally suited to be performed in the hybrid operating room/catheterization laboratory setting. The above cases clearly illustrate the feasibility of using an endovascular clamp technique to help facilitate the creation of a surgical anastomosis and further reduce the potential for coronary endothelial trauma and subsequent graft failure.

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