A patient with extensive ST elevation myocardial infarction who underwent emergent Impella CP® assisted off-pump coronary artery bypass without mechanical complication

Abstract

Impella (Abiomed Inc., Danvers, MA, USA) assisted off-pump coronary artery bypass has been increasingly reported in recent years. However, there have been no reports of the procedures performed for acute myocardial infarction in which the patient is hemodynamically unstable. We report a case of a 73-year-old man with cardiogenic shock due to extensive ST elevation acute myocardial infarction that worsened despite Impella CP® support. Because of the fragile myocardium in the acute phase of myocardial infarction, Impella assisted off-pump coronary artery bypass graft causes a high risk of myocardial injury, but we were able to safely perform the procedure by ingenious techniques.

Learning objective

When performing Impella-assisted off-pump coronary artery bypass for extensive acute myocardial infarction patients, the high risk of mechanical complications due to myocardial fragility must be considered. The position of Impella should be carefully monitored intraoperatively, and elevation of cardiac apex should be kept to a minimum to prevent myocardial damage caused by Impella.

Introduction

Impella devices (Abiomed Inc., Danvers, MA, USA) are mechanical circulatory support devices for percutaneous coronary intervention (PCI) in patients with cardiogenic shock (CS) due to acute myocardial infarction (AMI). Their utilization rate is comparable to that of intraaortic balloon pumping (IABP) and venoarterial extracorporeal membrane oxygenation (V-A ECMO) [1]. Therefore, the opportunities for coronary artery bypass (CABG) to be performed with Impella inserted are expected to increase further in the future.

Case report

A 73-year-old man presented to our hospital with persistent chest pain that had been present for the past hour. He had a history of hypertension but otherwise had no remarkable medical history. On arrival, the patient's blood pressure, heart rate, and oxygen saturation were 100/68 mm Hg, 90/min, and 100 % (inspired oxygen concentration: 0.9), respectively. On physical examination, the patient had a height, body weight, and body mass index of 165 cm, 53 kg, and 19.5 kg/m², respectively. Electrocardiogram (ECG) showed ST elevation in the anterior wall and reciprocal ST depression in the inferior leads (Fig. 1). Blood tests showed a high level of troponin I (0.55 ng/mL). Transthoracic echocardiogram (TTE) revealed decreasing wall motion from the anterior wall to the apex and an ejection fraction (EF) of 30 %. Computed tomography showed no abnormalities in the large thoracic vessels except for calcification of the surface of the ascending aorta. Mild pulmonary congestion was also observed. ST-elevation myocardial infarction (STEMI) was diagnosed, and urgent coronary angiography was attempted. We identified complete occlusion of the proximal right coronary artery (RCA) and complete occlusion of the left anterior descending artery (LAD) with severe calcification (Fig. 2A, B, C, D). Because a collateral blood flow from the left coronary artery to the RCA was observed, the RCA was considered to be chronically completely occluded, and the LAD was the culprit lesion; therefore, the decision was made to attempt PCI to the LAD with support from an Impella CP® inserted through the right common femoral artery. However, PCI was difficult owing to severe calcification, and standard balloon angioplasty was performed instead, resulting in Thrombolysis in Myocardial Infarction flow 3, while the LAD stenosis remained at 25 % (Fig. 2E, F). Aspirin and continuous heparin infusion were started with a target-activated clotting time of 180–200 s. Pulmonary artery catheterization performed under the assistance of Impella (P6 level) revealed no signs of right-sided heart failure (cardiac output: 3.32 L/min, pulmonary capillary wedge pressure: 22 mm Hg, mean pulmonary artery pressure: 25 mm Hg, and pulmonary artery pulsatility index: 4). At this point, the plan was to wait for improvement of CS with Impella support before attempting CABG. However, the next day, with increased Impella CP® support and catecholamine administration (dobutamine: 5γ, noradrenaline: 0.3γ), his pulmonary congestion worsened. Blood tests showed liver (aspartate aminotransferase: 827 U/L, alanine aminotransferase: 115 U/L) and mild renal (creatinine: 1.1 mg/dL) dysfunctions. ECG showed persistent ST elevation in the anterior wall, and TTE revealed that cardiac function remained decreased. Our heart team considered switching to Impella 5.0® or adding V-A ECMO, but early revascularization was necessary, and emergent Impella assisted off-pump coronary artery bypass (OPCAB) was performed. The patient's Society of Thoracic Surgeons risk score and the EuroSCORE II were 8.8 % and 15.0 %, respectively. We had to be very careful with the Impella assisted OPCAB because we thought this STEMI patient with a relatively high peak creatinine kinase level (10,656 U/L) had a high potential for mechanical complications by the intraoperative procedures.

Fig. 1.

Electrocardiogram shows ST elevation in the V1-V5 and reciprocal ST depression in the II, III, and aVF.

Fig. 2.

Coronary angiography shows complete occlusion of the right coronary artery proximally (A) and LAD proximally (B, C, D). Standard balloon angioplasty is performed for the LAD lesion with Impella assistance, but stenosis remains (E). Intravascular ultrasound at the location of the red arrow in the (E) shows severe calcification (F).

LAD, left anterior descending artery.

The surgery was performed via median sternotomy. The bypass targets were LAD and RCA, and the grafts were the left internal thoracic artery and saphenous vein (SVG), respectively. During proximal anastomosis, the running of Impella's shaft was confirmed using an epiaortic ultrasound before it punched out. Flow support was reduced from P4 to P2 to prevent aortic dissection. The anastomosis was performed using 6–0 polypropylene combined with the HEART-STRING III proximal seal system (Maquet, Rastatt, Germany). LAD anastomosis was performed using 8-0 polypropylene with P4 support and the location of Impella was confirmed using transesophageal echocardiography (TEE) before the anastomosis. RCA anastomosis was performed using 8-0 polypropylene proximal to the RCA to prevent moving the heart as much as possible with a heart positioner (Xpose 3 Positioner, Maquet) attached to the right ventricular side of the apex. During the anastomosis, the flow rate remained unchanged with P4 support, and no volume loading was required to maintain systemic circulation. An abnormal pump position alarm was observed; however, minor position adjustments allowed the anastomosis to be completed. No increase in mitral regurgitation was observed during the cardiac apex elevation. In total, 4, 2, and 20 units of red blood cell concentrate, fresh frozen plasma, and platelet concentrate, respectively, were used during the surgery.

The perioperative course is shown in Fig. 3. The Impella support remained in place postoperatively, and the patient was taken back to the intensive care unit. The Impella was subsequently weaned and removed with only a small amount of dobutamine use (3γ) on postoperative day (POD) 4. Pulmonary artery catheterization performed without Impella support showed improvement in cardiac function (cardiac output: 3.3 L/min, cardiac index: 2.0 L/min/m²) without Impella support. He was extubated on POD 6. Postoperative TTE showed an improvement in EF to 47.8 %, without aortic regurgitation or mechanical complications on POD 17. All grafts were patent on computed tomography coronary angiography on POD 19. He was discharged home on POD 23 without complications.

Fig. 3.

Perioperative course of the patient.

CABG, coronary artery bypass graft; NAD, noradrenaline.

Discussion

V-A ECMO, IABP, and Impella are mechanical circulatory support devices for patients with CS after AMI. Although IABP has been widely used for decades for such patients, a randomized controlled trial showed no difference in 30-day mortality when comparing IABP to Impella [2]. Although the comparison between V-A ECMO and Impella is debatable, Impella has been reported to be associated with reduced in-hospital mortality and medium-term mortality [3]. Saito et al. stated that Impella is an effective bridge to cardiac surgery for patients with CS [4]. It is certain that more and more patients will be introduced to Impella prior to CABG.

The patient was in the acute phase of extensive AMI, and PCI was difficult due to severe calcification; therefore, we planned CABG after waiting for the cardiac function to improve with mechanical cardiac assistance. However, despite the introduction of Impella, the patient's CS did not improve, necessitating emergency CABG to salvage myocardium and sufficient perfusion to maintain left ventricular function. We believe that one of the reasons for the improvement in left ventricular function after CABG in this case, despite the extensive AMI, was due to the bypass to RCA with a large perfusion zone. Although there are a few reports of off-pump coronary artery bypass with the sole support of Impella CP® or 5.0® for patients with severe cardiac dysfunction [[5], [6], [7]], there are no reports of OPCAB for extensive STEMI patients with hemodynamic instability. We believe that this report demonstrates that OPCAB with Impella can be safely performed in an extensive STEMI patient at high risk for mechanical complications.

A systematic review by Hwang et al. described that in patients with AMI, OPCAB showed a significant mortality benefit compared to other CABG methods and might be associated with prevention of myocardial damage associated with cardiopulmonary bypass or cardioplegic arrest [8]. We believe that it is debatable whether off-pump or on-pump beating CABG should be performed for patients who have had Impella introduced preoperatively, as in this case. Saito et al. stated that on-pump beating CABG is preferable because Impella support is insufficient because dislocation of the Impella during OPCAB may easily occur when the heart is lifted during the operation [4]. During RCA anastomosis, the Impella's position cannot be confirmed even with the use of TEE because the cardiac apex must be elevated. Therefore, it is necessary, as far as possible, to avoid elevating the cardiac apex. In performing OPCAB in this case, we anastomosed SVG to proximal #3 instead of #4 of the RCA to reduce the elevation of the cardiac apex and to prevent the dislocation of the Impella. In addition, we thought that the heart positioner placed at the apex might promote left ventricular damage caused by Impella, so we attached the positioner closer to the right ventricle than usual. We believe that these ingenuities allowed us to treat this patient with extensive AMI without mechanical complications.

Impella CP® assisted emergent OPCAB in a patient with CS after extensive STEMI could be performed without mechanical complications. Further discussion on performing Impella-assisted OPCAB is needed in the future.

Consent

Written informed consent was obtained from the patient.

Declaration of competing interest

The authors declare that there is no conflict of interest.

Appendix A. Supplementary data

The following are the supplementary data related to this article.

Movie 1

Coronary angiography showing complete occulusion of right coronary artery proximally

Movie 2

Coronary angiography showing complete occulusion of left anterior descending artery with intact left circumflex artery

Movie 3

Coronary angiography showing complete occulusion of left anterior descending artery with collateral blood flow to the right coronary artery

Movie 4

Coronary angiography showing intact left main trunk

Movie 5

Coronary angiography after standard baloon angioplasty showing left anterior descending artery stenosis remained at 25% with Thrombolysis in Myocardial Infarction flow 3

Movie 6

Intravascular ultrasound of left anterior descending artery showing sevre calcification unsuitable for percutaneous coronary intervension