Peer Reviewed Content

CASE STUDY: INFERIOR MYOCARDIAL INFARCTION RESULTING IN CARDIOGENIC SHOCK REQUIRING MULTIMODAL MECHANICAL SUPPORT

Authors: Richard H. Bengel PA-C, Claudine Pasquarello PA-C, Qiong Yang MD, Hitoshi Hirose MD

Key words: cardiogenic shock, mechanical, ECMO, RVAD, shock team

Abstract:

Introduction: Cardiogenic Shock initiatives throughout the country have come to the forefront of tertiary care centers. Cardiogenic shock presents in different ways; however, a post myocardial infarction hospital course is a common pathway yet results in nearly a 40% mortality rate. The course of this case study is an outlier in the setting of having a total of four different mechanical circulatory support devices placed ensuing survival.

Case Presentation: 61-year-old male with end-stage-renal-disease presented to the emergency department with an acute inferior wall myocardial infarction. He underwent revascularization; however, he had a complicated hospital course that required the utilization of an intra-aortic balloon pump, veno-arterial ECMO, and percutaneous left and right ventricular assist devices. He survived his course and was discharged.

Discussion: The necessity of each of these devices is important to explore and understand because of their individual indications and how they impact patient survival.

Introduction

Cardiogenic Shock initiatives throughout the country have come to the forefront of tertiary care centers. Cardiogenic shock presents in different ways; however, a post myocardial infarction hospital course is a common pathway yet results in nearly a 40% mortality rate.1 The course of this case study is an outlier in the setting of having a total of four different mechanical circulatory support devices placed ensuring survival. Among the variety of mechanical circulatory support (MCS) devices available for cardiogenic shock, decision making of the appropriate device is critical. The different MCS devices are used for different pathologies and carry their own possible complications. Implantation and explantation of MCS must be constantly evaluated and executed with timely sensitivity. In this case study, the study institution successfully implanted and explanted four MCS devices during the course of a patient who experienced cardiogenic shock after acute myocardial infarction.

Case Presentation

A 61-year-old male with a past medical history of hypertension, end-stage renal disease (ESRD) requiring peritoneal dialysis (PD), and active tobacco use who initially called emergency services for chest pain with associated nausea and insomnia. While in the emergency department, he was diagnosed with an inferior wall ST-elevation myocardial infarction (STEMI). He was taken emergently to the cardiac catheterization laboratory.

The left sided cardiac catheterization (LHC) showed an acute thrombotic proximal right coronary artery (RCA) occlusion of 100%. The interventional cardiologist performed a balloon angioplasty three times prior to regaining coronary flow. The interval “Thrombolysis in Myocardial Infarction” (TIMI) flow revealed extensive clot burden throughout the RCA.2 Following balloon angioplasty, the guidewire was advanced down the RCA into the posterior left ventricular artery (PLV) which caused profound bradycardia. He subsequently went into ventricular fibrillation (Vfib). Per protocol, cardiopulmonary resuscitation (CPR) and advanced cardiac life support (ACLS) were initiated.

The arrhythmia required three rounds of defibrillation before return of spontaneous circulation (ROSC) was achieved. He remained severely bradycardic and a transvenous pacing wire was placed in the right ventricle via the right femoral vein and ventricular pacing was initiated. The patient regained consciousness and followed commands promptly after these events. He then developed profound worsening hypotension requiring norepinephrine, vasopressin, and epinephrine infusions. He was intubated by anesthesia in a controlled fashion. Despite ROSC and being on the ventilator his arterial blood gas (ABG) continued to show a severe metabolic acidosis, presumably a lactic acidosis. The acidosis was treated medically while the mechanical thrombectomy of the RCA was completed. Finally, a drug eluting stent was placed in the RCA. Following revascularization, the patient continued to require high dose vasopressor and inotropic support and a right heart catheterization (RHC) was performed. The patient’s Swan Ganz values were 29/16 with a central venous pressure (CVP) of 24, and a thermodilution cardiac index of 1.2. The calculated pulmonary artery pulsatility index (PAPi) was 0.54 and the calculated cardiac power output (CPO) was 0.17. These values indicated biventricular failure.3 A percutaneous left ventricular assist device was considered; however, his left ventricle was underfilled and an intraaortic balloon pump (IABP) was placed. Following IABP placement, a transthoracic echocardiogram (TTE) was performed which showed an ejection fraction (EF) of 35- 40% with inferior, inferoseptal akinesis, and anterior hypokinesis. The right ventricle was akinetic and dilated. A Cardiogenic Shock consult was placed at that time.4 Via conference call, the cardiac surgeon, cardiac intensivist, interventional cardiologist, cardiologist, and cardiothoracic surgery physician assistant discussed the case and appropriate intervention. Based upon current Extracorporeal Life Support Organization (ELSO) guidelines, the patient was deemed an appropriate candidate for veno -arterial extracorporeal membrane oxygenation (VA ECMO).5 VA ECMO was cannulated with a 22 French arterial cannula in the right femoral artery and a 25 French venous cannula was placed in the left femoral vein. Following successful initiation of ECMO, the IABP was removed in favor of a percutaneous left ventricular assist device (Impella CPTM, Abiomed, Danvers, MA) to act as a left ventricle vent (LV vent). The Impella CP was set to level P2 for a flow of 1.8 liters per minute (l/min).

Figure 1 fluoroscopy were also utilized to ensure proper placement. Next, 5 French antegrade distal perfusion catheters were placed in bilateral superficial femoral arteries spliced from the VA ECMO circuit to provide perfusion to the lower extremities. Despite adequate mechanical flow rates, the patient developed ventricular fibrillation requiring three more defibrillation attempts prior to success. Unfortunately, the echo after this event showed complete cardiac standstill. He was transferred to the Cardiac Care Unit (CCU).

On arrival to the CCU, a full set of laboratory values were assessed, and imaging was obtained to ensure correct placement of the current devices. He required blood transfusion, which is not uncommon for ECMO. The laboratory values demonstrated a continued lactic acidosis and hyperkalemia; meanwhile, he was oliguric trending towards anuria. A central venous hemodialysis catheter was placed, nephrology was consulted, and he was started on continuous veno-venous hemodialysis (CVVHD).6 Again, he had recurrent episodes of Vfib for which he was defibrillated successfully. On post-operative day (POD) #1 from VA ECMO insertion, sedation was removed to assess brain activity, and he followed commands. Because of the acute nature of this event, and required transplant workup time a consult was placed to a heart transplant center; unfortunately, due to multi-organ system failure, he was deemed too high of a surgical risk and was denied.7 A palliative medicine consultation was performed, as per protocol for all mechanical circulatory support patients at the investigating institution.8 The family continued to pursue aggressive measures. Over the course of next several days, aggressive fluid removal was performed with CCVHD, tube feeds were initiated, the ventilator was weaned to minimal settings and a sedation vacation was performed assuring he remained neurologically intact.9

The first attempted ECMO wean was performed three days after implantation, which was successful. On the following day, a formal ECMO wean was performed.10 The heart function improved enough to consider decannulation on the following day; however, on the day of planned decannulation, the patient developed diffuse alveolar hemorrhage. Anticoagulation was held and decannulation was postponed as ECMO was supporting the ventilation and oxygenation of the patient.

Over the course of the next several days, continued hemoptysis delayed decannulation and the patient required multiple bronchoscopies. At that time, the Shock Team reconvened and collectively decided that the risk of continuing ECMO support outweighed the benefit due to the anticoagulation goals of operating this type of mechanical support.11 On POD #7, the team developed a plan to keep the Impella CP and decannulate the VA ECMO in the hybrid OR. Interventional cardiology presence was coordinated and simultaneous cannulation of a right ventricular assist device with an oxygenator was inserted via the right internal jugular vein (ProtekDuo TM , Tandem Life, Pittsburgh, PA). A ProtekDuo was placed, and the VA ECMO was removed, refer to Figure 2 and Figure 3 for reference. The removal of the VA ECMO arterial cannula was complicated by acute limb ischemia requiring vascular surgery intervention including right lower extremity angiogram, repair of the right common femoral artery and femoral artery thrombectomy. Following this, he returned to the CCU in critical yet stable condition. Over the course of the following 24 hours, he remained grossly stable despite frequent suction alarms from the Impella CP, and severely elevated liver function studies concerned the Shock Team of hemolysis. At that time, another TTE was performed which showed a significantly improved left ventricle EF of 4045%. The Impella CP was removed on POD #9 as risk of hemolysis outweighed the benefit of continued mechanical left ventricular support.12 The patient’s course required bilateral chest tube insertion for increasing pleural effusions and repeated bronchoscopies were performed for lavage of remnant hemorrhage.

Over the course of the next several days, his sedation remained light so that he could participate in rehabilitation, but remained bound by renal replacement therapy. His ventilator settings remained minimal. He remained on aggressive CVVHD volume removal goals and his wound vacuum dressings were changed at standard times. On POD #13, he began to “ pressuresupport ventilate” per ventilator weaning strategies.13 Furthermore, his LFTs and myoglobin peaked and began trending down. On POD #19, after serial echocardiograms, the right ventricle regained life sustaining function and the ProtekDuo was removed.

As the acute phase of his hospital course concluded, he required implantation of a permanent pacemaker for sick sinus syndrome on Day #21. He had a tracheostomy and percutaneous

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• …and many more Register now and never miss an episode! https://www.terumocv.com/evh_experts Here’s gastric (PEG) feeding tube placed. On Day #35, he was transitioned from CVVHD to intermittent hemodialysis. His respiratory status improved, and his ventilator support was discontinued on Day #39. Eventually, he passed speech evaluation for oral intake, his tracheostomy was decannulated and he was transferred to an acute rehabilitation unit on Day #46.

Discussion

The main discussion points surrounding this case study revolve around mechanical circulatory support devices and the implications involved in that process. The device choice matters less about preference of a device compared to another as many of them overlap in some fashion. However, the more important factors in device decision making included patient assessment, identifying patient needs, which device meets the demands, and what is the destination of therapy. An ongoing assessment through the continuum of care is also demonstrated in the presented case study. From the report, it can be identified that certain devices have requirements, limitations, and particular complications associated with them respectively. Regarding patient needs, a full assessment must be performed prior to choosing a device. The assessment must correctly identify cardiogenic shock as opposed to other types of shock. Because mechanical support is primarily indicated for cardiogenic shock, other forms of shock must be effectively ruled out from the differential diagnosis. Although, root-cause determination of shock may be challenging in some patient case scenarios, for example a patient who experiences cardiac arrest and aspirates. It would be difficult in that scenario to solely decide which is the definitive diagnosis for shock as it may be a mixed picture including septic shock. Another common scenario includes septic and cardiogenic shock surrounding endocarditis and bacteremia.14, 15 In the assessment of cardiac function, it is imperative to assess both right heart and left heart function as the device choice can differ. All three; right sided heart failure, left sided heart failure or biventricular failure can lead to different decision-making strategies.

The assessment should include laboratory values such as complete blood counts, basic metabolic panels, arterial and venous blood gas assessment, blood cultures, serum lactic acid levels, and procalcitonin. Imaging during the assessment mainly revolves around echocardiography; although, the sequence of events frequently bypasses this step as patients go directly to cardiac catheterization upon diagnosis of acute coronary syndrome. In the case where patients go to the catheterization, it is imperative that both a left heart and a right heart assessment are performed. During the assessment of the left heart, a ventriculogram (LV gram) is important to identify ejection fraction and assessment of the coronary arteries to identify intervenable culprit lesions.16

The assessment of the right heart is performed with a Swan Ganz catheter (pulmonary artery catheter). During the RHC, assessment of the central venous pressure (CVP), pulmonary artery systolic pressure, pulmonary artery diastolic pressure, left ventricular end-diastolic pressure (LVEDP) and cardiac index, both thermodilution and mixed venous via Fick calculation are all important to the appropriate decision-making processes. The CVP is the measurement of the pressure at the right atrium, sometimes referred to as the right atrial pressure (RAP). The pressure at the right atrium is correlated to the preload to the right ventricle. An elevated CVP can be attributed to many different causes; however, in the setting of cardiogenic shock an elevated CVP is indicative of RV volume overload or failure. Pulmonary artery pressures are evaluated to assess the function of the left ventricle. These numbers are most relevant when discussed in relation to the patient’s systemic pressures. As the function of the left ventricle deteriorates, the pulmonary artery pressures become in closer ratio to the systemic blood pressure. By measuring the pulmonary artery pressures and the CVP, a calculation can be made to assess the Pulmonary Artery Pulsatility Index (PAPi). Assessment of the PAPi is crucial in identifying right ventricular dysfunction and studies have correlated more aggressive treatment of low PAPi scores and improvement in morbidity and mortality in relation to inferior wall MI patients suffering right ventricle dysfunction. Furthermore, PAPi has also been found to have the highest sensitivity and specificity to right ventricular dysfunction compared to any other current invasive hemodynamic measurement of the right ventricle.16 Once the PAPi is evaluated, the Cardiac Output Power (CPO) should be calculated to evaluate left ventricular dysfunction. In the non-heart failure setting, cardiac output alone may be sufficient to evaluate heart function; however, in the chronic and acute heart failure settings CPO offers measurement of the hydraulic pumping ability of the heart. This evaluates the strength of contraction and the ability to generate pulsatility. CPO has been linked to a strong correlation in