Microaxial flow pump–assisted off-pump coronary artery bypass for low ejection fraction with relative contraindication to cardiopulmonary bypass

Intraoperative positioning of Impella 5.5 device 5 cm into the left ventricle.

Central Message.

The Impella left ventricular assist device can be used to assist in low EF off-pump coronary artery bypass as a means to avoid CPB and its associated complications.

Current guidelines for patients with stable ischemic heart disease recommend surgical revascularization with coronary artery bypass grafting (CABG) in those with multivessel disease and reduced ejection fraction (EF).¹ Oftentimes, these patients will also have multiple concomitant comorbidities increasing their operative risks. In the interventional cardiology space, protected percutaneous coronary intervention (PCI) using microaxial flow pumps (Impella, Abiomed Inc) has been studied in high-risk PCI and endorsed in an expert consensus statement from the Society for Cardiovascular Angiography & Interventions/American College of Cardiology/Heart Failure Society of America/Society of Thoracic Surgeons.^2,3 The surgical community use of the Impella left ventricular assist device in low EF CABG has not been well explored, with only limited case series demonstrating its feasibility.⁴ We report the case of an Impella-assisted off-pump coronary artery bypass grafting (OPCAB) in a patient deemed to be at high risk of complications with full cardiopulmonary bypass (CPB) but thought not to have the cardiac reserve to tolerate OPCAB.

Case Summary

This is a case of a 72-year-old man with known coronary artery disease who had undergone multiple PCIs previously and had developed ischemic cardiomyopathy with an EF of 35%, a dilated left ventricle with left ventricular end-diastolic diameter of 5.3 cm, no valvular disease, and preserved viability. Institutional Review Board and individual consent were not required for this case report. On preoperative coronary catheterization, the patient had a right dominant system with 80% to 90% lesions in all 3 major vessels. In addition to his coronary artery disease, he had multiple other comorbidities, the most significant of which were a hemorrhagic stroke a few months before his planned operation and diabetic nephropathy with a baseline creatinine of 2.7 mg/dL and estimated glomerular filtration rate of 26 mL/min/1.73 m². Given his recent stroke, the neurologists were concerned about the potential for rebleed with full heparinization and coagulopathy of CPB. Therefore, the patient was referred for OPCAB. To complete his neurologic workup, we obtained a carotid ultrasound that showed 0% to 19% stenosis in both internal carotid arteries and a computed tomography scan of his chest that demonstrated no ascending aortic calcification but moderate calcification in the abdominal aorta and iliac arteries. We were concerned that his left ventricle may not tolerate manipulation of the heart during grafting. If this were to occur, it would threaten his neurologic and renal perfusion and also risk conversion to CPB. Therefore, we opted to use an Impella 5.5 left ventricular assist device to provide hemodynamic support during heart manipulation and optimize renal perfusion throughout the operation, while minimizing the bleeding risk of full heparinization.

At operation, both internal thoracic arteries were harvested in a skeletonized fashion and the left radial artery was harvested endoscopically. The left radial artery was then anastomosed to the right internal thoracic artery end-to-end to create a composite graft. At this stage, a side clamp was placed on the ascending aorta to anastomose a 10-mm Dacron graft through which an Impella 5.5 device was introduced and advanced across the aortic valve into the left ventricle under transesophageal echocardiographic guidance (Figure 1). Impella support was commenced at speed P6. We then proceeded with off-pump revascularization, using standard techniques, and performed a bypass with a left internal thoracic artery to left anterior descending and a sequential graft with the right internal thoracic artery radial composite to the first obtuse marginal and the right posterior descending artery. We opted for total arterial revascularization for the survival and patency benefit over vein conduits. The patient remained hemodynamically stable throughout the procedure without the need for Impella repositioning. After completion of all anastomoses, confirmation of good flows and low pulsatility index with the Medistim device (Medistim Inc) was achieved and the Impella device was weaned and removed without complication. Total time with the Impella in place was 186 minutes, and during this time there were only 5 time points when mean arterial pressure fell below 50 mm Hg, for a total time of approximately 5 minutes. The patient was then brought to the intensive care unit on minimal inotropic and vasopressor support.

Figure 1.

Intraoperative positioning of the Impella 5.5 device 5 cm into the left ventricle under transesophageal echocardiography guidance.

The patient was extubated on postoperative day (POD) 1 on minimal cardioactive medications. The evening of POD 1, the patient developed sudden onset of right upper-extremity weakness concerning for stroke. He was taken immediately for computed tomography of the head, which demonstrated a moderate right middle cerebral artery stenosis and bilateral vertebral artery stenosis that had been present preoperatively, neither of which could explain his presentation. Follow-up brain magnetic resonance imaging demonstrated multiple acute and subacute supra- and infratentorial infarcts favoring an embolic etiology (Figure 2). No other cardio-embolic etiology could be identified because the patient had no episodes of atrial fibrillation, no intracardiac thrombus, and no sources of right-to-left shunts. After rigorous physical therapy, his strength improved, and he was discharged on POD 20. His predischarge transthoracic echocardiogram demonstrated an EF of 41%. At last follow-up with his cardiologist 2 years after surgery, he was asymptomatic and doing well.

Figure 2.

Postoperative brain magnetic resonance imaging demonstrating innumerable bilateral scattered foci of hyperintensity due to embolic infarcts.

Discussion

CABG does a better job of improving survival in patients with low EF compared with medical therapy alone but comes with the inherent risks of CPB.^1,5 OPCAB offers the opportunity to mitigate these risks; however, in the severely diseased heart this may not be tolerated from a hemodynamic standpoint, such that the incremental risk of avoiding CPB could eclipse the benefits due to effects of end-organ hypoperfusion and occasional emergency conversion to CPB. Intra-aortic balloon pump counterpulsation has been used but may not provide enough support in certain patients, which is why the Impella assist device represents an intriguing alternative.⁴ In our patient, his low baseline cardiac function, prior hemorrhagic stroke, and chronic kidney disease had to be carefully balanced, which is why we opted to proceed with an Impella-assisted OPCAB procedure to both minimize the bleeding risk of full heparinization and to optimize his hemodynamics during cardiac manipulation to prevent hypoperfusion of the brain or kidneys. The option of CPB-assisted beating heart surgery was also discussed, but it was believed that the additional hemodynamic benefit of pump-assisted beating heart surgery would be outweighed by the risk of hemorrhagic conversion under full heparinization. Both these goals were seemingly met because he had no major bleeding events and no periods of prolonged hypotension intraoperatively. Unfortunately, he did have a postoperative ischemic stroke, which raises the question of what role the Impella device played as an exacerbating or mitigating factor in his stroke risk. On the one hand, Impella assistance requires aortic manipulation, which increases stroke risk. On the other hand, given the diffuse nature of his magnetic resonance imaging findings, it is possible the device may have actually reduced his stroke burden by minimizing periods of hypotension intraoperatively.

Conclusions

Impella-assisted OPCAB represents a feasible tool in the surgical armamentarium in managing patients requiring low EF CABG; however, careful patient selection is essential. Trials are ongoing to ascertain the general effectiveness and risk of preemptive Impella use in high-risk CABG, but these studies focus on prevention of postcardiotomy shock and low cardiac output syndrome.⁶ Our case demonstrates a unique application of the device when it is thought desirable to avoid CPB to mitigate against the problems associated with full heparinization or bypass, as opposed to the typical goal of preventing perioperative shock.

Conflict of Interest Statement

The authors reported no conflicts of interest.

The Journal policy requires editors and reviewers to disclose conflicts of interest and to decline handling or reviewing manuscripts for which they may have a conflict of interest. The editors and reviewers of this article have no conflicts of interest.