Chart 1: Cardiogenic Shock Assessment of the study institution, developed by Virtua Our Lady of Lourdes

Virtuaourladyoflourdes Cardiogenic Shockalgorithm

InclusionCriteria

AcuteMyocardialInfarction:STEMIorNSTEMI

• IschemicSymptoms

• EKGand/orbiomarkerevidenceofAMI (STEMIorNSTEMI)

CardiogenicShock

• Hypotension(<90/60)ortheneedforvasopressor orinotropestomaintainsystolicbloodpressure>90

• Evidenceofendorganhypoperfusion (coolextremities,oliguria,lacticacidosis-sendlactate alongwithotherpertinentlabs)

ACTIVATECATHLAB

Notifythe

CardiogenicShock

TeamviaDoc

Halo/Qliq

WeanOFFVasopressorsandInotropes

ACCESS&HEMODYNAMICSUPPORT

• Obtainfemoralarterialaccess(viadirectvisualizationwithuseofultrasound andfluro)

• Obtainvenousaccess(FemoralorInternalJugular)

• ObtaineitherFickcalculatedcardiacindexorLVEDP IFLVEDP>15ORCARDIACINDEX,2.2ANDANATOMYSUITABLE,PLACE IMPELLA

CoronaryAngiography&PCI

• AttempttoprovideTIMIIIIflowinallmajorepicardiavesselsotherthanCTO

• IfunabletoobtainTIMIIIIflow,consideradministrationofintra-coronary

PerformPost-PCIHemodynamicCalculations

1.CardiacPowerOutput(CPO):MAPxCO 451

2.PulmonaryArteryPulsatilityIndex(PAPI): sPAP-dPAP RA

IfCPOis>0.6andPAPI>0.9,operatorsshouldweanvasopressorsandinotropesanddetermineifImpellacanbeweanedandremovedintheCath LaborleftinplacewithtransfertoICU.

EscalationofSupport-Shouldmonitorhourlyhemo'sanddetermineQ4-6hrsneedformoresupport IfCPOremains<0.6operatorsshouldconsiderthefollowingoptions:

• PAPIis<0.9considerrightsidedhemodynamicsupport

• PAPIis.0.96considerationforadditionalhemodynamicsupport Localpracticepatternsshoulddictatethenextsteps:

• PlacementofmorerobustMCSdevice(s)-ECMO,ProtekDuo,RVAD.

• TransfertoLVAD/Transplantcenter

IfCPOis>0.6andPAPI<0.9considerprovidingrightsidedhemodynamicsupportifclinicalsuspicionforRVdysfunction/failure.

VascularAssessment

• PriortodischargefromtheCathLab,adetailedvascularexamshouldbeperformedincludingfemoralangiogramandDopplerassessment oftheaffectedlimb

• Ifindicated,externalbypassshouldbeperformed.

ICUCare

• Hourlyhemodynamicassessments,includingdetailedvascularassessment-NEEDQ4-6hrsre-evaluationwithTeamtodecideescalationof careorweaningofsupport.

• MonitorforsignsofhemolysisandadjustImpellapositonasindicated

DeviceWeaning

Impellashouldonlybeconsideredforexplanationoncethefollowingcriteriaaremet:

• Weaningofffromallinotropesandvasopressors

• CPO>0.6andPAPI>0.9

DeviceWeaning

Patientswhodonotregainmyocardialrecoverywithin3-5days,asclinicallyindicated,shouldbetransferredtoanLVAD/TransplantCenter.If patientsarenotcandidates,palliativecareoptionsshouldbeimplemented predicting mortality surrounding chronic heart failure and cardiogenic shock.17 Once the PAPi, CPO, PAWP, and FICK cardiac index are assessed, the treatment for mechanical support should be made. 4, 18 Once the treatment pathway comes to warrant mechanical support, the team will discuss which device would best benefit the patient. The devices range in which side of the heart is supported, how much cardiac output support is offered, if the ventilation and oxygenation are supported, and if cardiac perfusion is supported. Furthermore, accessibility of insertion is also discussed. The ability to insert the correct device in an appropriate amount of time is crucial to decreasing morbidity and mortality in cardiogenic shock.

Shock Team Approach

The Shock Team Approach is a multidisciplinary team that evaluates, discusses, and intervenes on cardiogenic shock, bringing different perspectives to form a unified plan for complex patients. The Shock Team primarily treats cardiogenic shock; however, it is involved in assessing different pathological shock patients. The purpose of the team evaluating all shock patients is to ensure capture of all shock cardiogenic in nature; meanwhile, excluding those patients who would not benefit from cardiac or mechanical support.4, 19

The team primarily consists of a cardiologist, interventional cardiologist (IC), cardiac surgeon, and cardiac intensivist. These providers are typically the on-call providers; therefore, the system is reliant on broad acceptance of the terms and obligations of the team. The ancillary support comes from the catheterization laboratory (cath lab), operating room staff, critical care unit (CCU), advanced providers (APP), perfusionists, nurses, transfer center, and systemic knowledge of the shock pathway to initiate Shock Team involvement. Each facet of the team has a duty that equates to their respective skill sets and abilities. The cardiologist typically holds the longest relationship with a patient, from the time that the alert is initiated until outpatient follow-up. Having a heart failure cardiologist is preferred; although, not necessary at every institution if a relationship with a destination center is bridged. If a patient needs destination therapy through either heart transplantation or long term LVAD, they will require transport to that center after stabilization and ready for further advanced therapy.

The IC holds multiple responsibilities as well and intervention including implantation is heavily decided in conjunction with the cardiac surgeon. The IC can initiate a shock activation, implant devices, explant devices and intervene on coronary arteries causing hemodynamic instability. A shock activation from the IC usually evolves from acute coronary syndrome (ACS) or catheterization complication. Implanting certain devices can be done percutaneously requiring fluoroscopy utilizing a specified skill set by the IC. The main objective of the cath lab is to identify right sided and left sided function, and coronary anatomy. By evaluating the left and right side of the heart, the team can decide which device to choose, which is discussed in further detail in subsequent sections. Through evaluation of the coronary arteries, the IC and cardiac surgeon can determine if percutaneous coronary intervention or coronary artery bypass graft is best suited for the patient. Current literature depicts that during a STEMI, the culprit lesion is intervened upon; however, in the setting of shock, all flow limiting stenosis should be intervened upon. Furthermore, current literature supports hemodynamic stabilization and systemic tissue reperfusion prior to bypass grafting. The cardiac surgeon is involved with multiple responsibilities; typically, the surgeon has two main objectives, supporting implantation of the devices and recognizing surgical candidacy of both revascularization and destination therapy. Implanting devices usually falls into the scope of practice of the surgeon when a conduit graft or cannulation of a cardiopulmonary bypass circuit is indicated. Furthermore, the surgical candidacy of the patient is evaluated at two different levels by the surgeon. Revascularization is only part of the surgical evaluation. During this part of the evaluation bypass targets are identified, conduit limitations and surgical complexity revolving around comorbidities are discussed in relation to risk versus benefit to the patient. Meanwhile, the surgeon also evaluates the likelihood of the patient being a candidate for heart transplantation or destination Left Ventricular Assist Device (LVAD) implantation. The cardiac intensivist holds a role that culminates in the assessment and plan of these other specialists. The intensivist must assess the likelihood of recovery and ability to stabilize the patient given the revascularization strategy and mechanical circulatory support device choice.

The discussion during the shock activation conference call allows the specialists to voice expert opinion and concern from different perspectives. The conversation starts with a case presentation by the provider who identified shock and called the transfer center. The next several parts of the conversation lead to answers surrounding specific questions led by the IC, surgeon, and intensivist about chronicity of the patient’s heart function, pertinent medical history, patient presentation, and family/patient wishes. Through this discussion a plan is formulated, the patient is assessed including catheterization, and a device is implanted.

Table 1: Mechanical circulatory support devices including indications, contraindications and benefits of devices utilized during this case presentation.

Device Indications

Intraaortic Balloon Pump (IABP) AMI, cardiogenic shock, acute mitral valve regurgitation, cardiac catheterization with or without percutaneous coronary intervention (PCI), refractory unstable angina, cardiac surgery, inability to wean from cardiopulmonary bypass, left ventricular failure, refractory ventricular rhythms.

Impella CP High-risk PCI, post-cardiotomy cardiogenic shock, cardiogenic shock secondary to myocardial infarction and shock states refractory to medical therapy with or without IABP.

ProtekDuo Primary right ventricular failure without left ventricular failure secondary to acute MI.

Contraindication

Absolute: aortic insufficiency, aortic dissection, end-stage heart disease without available destination and aortic stents.

Benefits

Increase coronary perfusion pressure.

0.5 LPM CO

Mural thrombus, mechanical AV, moderate to severe AI or AS, PAD that does not allow for implantation, significant right heart failure, cardiorespiratory failure, atrial or ventricular septal defects, cardiac tamponade, or LV rupture.

Increase coronary perfusion pressure

4.0 LPM CO

Right sided heart failure with concomitant left sided heart failure. Fully support right ventricular CO with ability to utilize oxygenator.

Veno-arterial extracorporeal membranous oxygenation

(VA ECMO)

Cardiac index less than 2.0 l/min2 and hypotension as defined by systolic blood pressure less than 90 mmHg on high dose inotropic support and/or IABP support.

Cardiogenic shock from acute coronary syndrome, arrhythmia, myocarditis, drug overdose, cardiac trauma, pulmonary embolism, postcardiotomy shock, inability to wean from cardiopulmonary bypass, and bridge to therapy such as LVAD or transplant.

No foreseeable myocardial recovery or noncandidacy for durable LVAD implantation or heart transplantation.

Unrepaired aortic dissection, severe aortic insufficiency, unknown downtime prior to cardiac arrest, inadequate CPR leading to massive tissue malperfusion, brain injury, disseminated malignancy, and severe peripheral vascular disease.

Full right and left ventricle CO support, with ability to support ventilation and oxygenation.

At the study institution, the Shock Team is activated via the transfer center. Once a patient is identified as having tissue malperfusion, the evaluating provider, whether that is an emergency medicine provider or a patient in the cath lab, is informed to call the transfer center. Once the transfer center is aware of the Shock Activation, a conference phone call is made between the activating provider, the cardiologist, IC, cardiac surgeon, and cardiac intensivist. The patient and case are discussed. The plan is developed, and a device is implanted if indicated. Once the device is in and the team is satisfied with the stabilization of cardiogenic shock, the patient is admitted to the CCU for continuous critical care management. The subsequent management is done primarily by the cardiac intensivist; however, a team approach is continued throughout the hospital course, particularly involving transport to a destination center.

Intraaortic Balloon Pump (IABP)

The intraaortic balloon pump (IABP) is a counterpulsation heart pump. Counterpulsation is a technique to lower the afterload on the heart during contraction resulting in decreased workload on the left ventricle. The IABP deflates at the end of diastole, just before the left ventricle contracts. This causes a void in the column of blood beyond the left ventricle; therefore, there is less pressure the heart has to overcome to create output. The IABP generates approximately 0.5 liters/minute of increased cardiac output.19 As opposed to intuition because the lack of significant increase in cardiac output, the IABP 30-day mortality rate of cardiogenic shock patients was found to be noninferior when compared to the Impella CP.20 Next, the IABP inflates at the end of systole, just before the aortic valve closes. As the aortic valve closes and the IABP inflates. This causes a rise in coronary perfusion pressure. Lastly, the IABP is the easiest and fastest device to implant, making it enticing in emergent cardiogenic and hemodynamic situations as a first line device.

IABP Indications

The indications for IABP are acute myocardial infarction, cardiogenic shock, acute mitral valve regurgitation, cardiac catheterization with or without percutaneous coronary intervention (PCI), refractory unstable angina, cardiac surgery, inability to wean from cardiopulmonary bypass, left ventricular failure, refractory ventricular rhythms, sepsis, and complex congenital heart disease.

The contraindications are divided into absolute and relative lists. The absolute contraindications include aortic insufficiency, aortic dissection, end-stage heart disease without available destination and aortic stents. The relative contraindications are uncontrolled sepsis, abdominal aortic aneurysm, tachyarrhythmias, severe peripheral arterial disease (PAD) with or without complex arterial surgery.21

IABP Recommendations

The intraaortic balloon pump (IABP) had historically been a class I recommendation for cardiogenic shock; however, over the past several years the IABP has fallen to a IIa and IIb recommendation in both America and Europe. Despite the downgraded recommendation, it remains the most commonly used device for cardiogenic shock.22 Current literature is moving to a more unfavorable picture for the IABP in the setting of cardiogenic shock. In the IABP-SHOCK I trial, the researchers were only able to describe a modest improvement in the APCHE II score, which is the most commonly used ICU mortality predictor score.23, 24 Following that study, the IABP-SHOCK II study only confirmed that the use of IABP in the setting of myocardial infarction was only superior in comparison to medical therapy. Furthermore, the study failed to show a difference in 30-day mortality in the setting of cardiogenic shock with myocardial revascularization.25

Complications of IABP

Complication rates for IABP fall between 9-30% based on current literature. The most common complication is lower extremity limb ischemia requiring emergent revascularization. Other complications include false aneurysm formation, thromboemboli, and femoral artery stenosis. Other non-vascular complications include seromas, spinal cord ischemia, visceral ischemia, groin infection, balloon rupture or entrapment, peripheral neuropathy, and atheroemboli.26

In the presented case study, the IABP was used to temporize hemodynamics and increase myocardial perfusion. Although the IABP can improve LV function, this was not the patient’s main hemodynamic issue. The IABP may have improved coronary perfusion during intervention while the RCA was intervened upon with PCI. Despite intervention to the culprit lesion, the patient continued to hemodynamically deteriorate leading to escalation of mechanical support that better supported the right ventricle.

Percutaneous Left Ventricular Device

Percutaneous left ventricular devices are temporary mechanical heart pumps that are inserted to assist in unloading the workload of the heart by generating cardiac output. These devices are inserted via percutaneous catheter in the femoral arteries or surgically via axillary approach. Although other devices are currently on the market, in the present case an Impella CP was utilized; therefore, discussion will focus on this particular device. The Impella CP is a mechanical pump utilizing microaxial flow. This device is inserted percutaneously via a femoral artery catheter. It is inserted retrograde through the aortic valve. The inflow cannula is located in the left ventricle and the outflow cannula resides above the aortic valve. The device pulls blood out of the left ventricle and expels the blood above the aortic valve. By pulling the blood out of the left ventricle, it decreases the workload of the left ventricle by reducing preload. The Impella CP can provide up to 4.0 liters/ minute of cardiac output. In addition, it can provide increased coronary perfusion pressure.27 By increasing coronary perfusion pressure, the myocardium has a higher likelihood of recovery. The increased probability of recovery is secondary to decreased end diastolic pressures and increased microvascular circulation.28 Because the Impella CP can significantly unload the left ventricle and increase microvascular circulation, it holds a place in the treatment of ischemic cardiogenic shock. In initial studies such as the IMPRESS trial, the Impella did not show added benefit to myocardial infarction patients in cardiogenic shock. However, more recent data has proven that the Impella improves morbidity and mortality outcomes after cardiogenic shock. The largest cohorts to date, published in The Journal of Interventional Cardiology, provided a clinically significant improvement in patients who received left ventricle off-loading prior to PCI, and it went on to outline the improved outcomes in patients who failed inotropes with and without IABP therapies.28 Furthermore, according to the same study, the likelihood of more complete revascularization is achieved with the Impella compared to IABP.29 In another article published in the Annals of Thoracic Surgery, the Impella CP had superiority in 30 -day mortality at the study institution compared to historical data at the same institution in a similar cohort of patients.30

Indications for CP Impella

Indications for Impella CP placement revolve around similar principles as the IABP. The Impella is indicated for high-risk percutaneous revascularization, post-cardiotomy cardiogenic shock, and cardiogenic shock secondary to myocardial infarction. The Impella CP is indicated for shock states refractory to medical therapy with or without IABP. The Impella CP is limited to a four-day time limit of implantation according to the Food and Drug Administration (FDA). The contraindications for the Impella CP include mural thrombus, mechanical aortic valve, aortic valve stenosis with an aortic valve area of <0.6 cm2, moderate to severe aortic insufficiency, peripheral vascular disease that does not allow for implantation, significant right heart failure, cardiorespiratory failure, atrial or ventricular septal defects, cardiac tamponade, or LV rupture.31

Complications of Impella CP

Introducing a mechanical circulatory device into the body carries significant risks, from both surgical and medical perspectives. The main categories of risk revolve around implantation, embolization, and hemolysis. The implantation of Impella CP can cause injury to the vasculature in the femoral artery resulting in dissection, retroperitoneal hematoma, or limb ischemia. The aortic valve may be damaged, or the patient may experience left ventricular rupture. Embolization typically occurs during implantation on diseased aortas and is less common in the subsequent duration.

Lastly, hemolysis is the destruction of blood cells caused by axial blood flow. The destruction of platelets can lead to an acquired thrombocytopenia. Furthermore, the hemolysis of red blood cells can lead to anemia, bilirubinemia and, if severe enough, acute renal failure.32

The limitations of the Impella CP were demonstrated in the present case. The patient was experiencing biventricular failure status post cardiac arrest. The Impella CP was able to assist in unloading the LV. However, because the patient presented with an RCA territory infarct, the patient needed right ventricular support. In many settings, left sided heart failure is the most common cause of right sided heart failure. In this case, the right ventricular function was compromised by the MI.

The left ventricular dysfunction was secondary to post-cardiac arrest stunning of the myocardium.

The Impella assisted in LV output; however, the patient required more support leading to prolonged Impella utilization in this case. VA ECMO was placed emergently to support biventricular failure and respiratory compromise. The Impella CP was left in place as a left ventricle vent, to ensure complete decompression of the left ventricle. The concomitant use of Impella CP with VA ECMO has shown in a randomized trial to have clinically significant lower hospital mortality and a higher rate of bridge to recovery or advanced therapy such as permanent LVAD.33

Veno-Arterial Extracorporeal Membrane Oxygenation (VA ECMO)

Veno-Arterial Extracorporeal Membrane Oxygenation (VA ECMO) is a cardiopulmonary bypass circuit that drains blood from the venous system, passes the blood through a semi-permeable membrane allowing for diffusion of carbon dioxide (CO2) and oxygen, and returns the blood in retrograde flow into the aorta. The venous blood is drained by the inflow cannula. By draining the blood from the venous system, it reduces the preload to the RV thus not giving preload to the LV. Subsequently, the workload of the heart is reduced by decreasing the myocardial stress of the LV. By removing preload to the right ventricle, it does not allow for blood to pass through the pulmonary vasculature which does not support native ventilation and oxygenation. The blood drained from the venous system must pass through a semi-permeable membrane, referred to as the oxygenator, allowing for CO2 removal and oxygen diffusion into the blood. The blood is then returned to the patient via the outflow cannula into the abdominal aorta via retrograde flow providing antegrade perfusion to the cerebral and coronary circulation.

Indications for VA ECMO

Indication for VA ECMO is based on two key factors: hemodynamic support needs and underlying diagnosis. Hemodynamic support factors include a cardiac index less than 2.0 l/min2 and hypotension as defined by systolic blood pressure less than 90 mmHg on high dose inotropic support and/or IABP support. Underlying diagnosis is important in initiation of ECMO because reversing the cause or bridge therapy needs to be determined, as cannulation of ECMO without those parameters is futile. Underlying diagnoses include but are not limited to cardiogenic shock from acute coronary syndrome, arrhythmia, myocarditis, drug overdose, cardiac trauma, pulmonary embolism, postcardiotomy shock, inability to wean from cardiopulmonary bypass, and bridge to therapy such as LVAD or transplant.34

Contraindications of VA ECMO

The most discussed contraindication for VA ECMO is the recoverability of heart function or the ability to bridge to a long-term device or transplant candidacy. The other contraindications include unrepaired aortic dissection, severe aortic insufficiency, unknown down-time prior to cardiac arrest, inadequate CPR leading to massive tissue malperfusion, brain injury, disseminated malignancy, and severe peripheral vascular disease.34

Complications of VA ECMO

Complications of ECMO are very common and are highly correlated with increased rates of morbidity and mortality. Complications can be divided into a few sections. The first is insertion. Insertion can be complicated by vascular injury, embolism, and bleeding. Management of ECMO has two major contributors: anticoagulation and pump tubing. Anticoagulation goals can rise and fall between individualized patients. If a patient is hemorrhaging, anticoagulation can be stopped; however, this may lead to circuit thrombosis or other thrombotic events. If the patient is hypercoagulable, increasing anticoagulation goals may lead to bleeding, disseminated intravascular coagulopathy (DIC) or heparin induced thrombocytopenia (HIT). The ECMO tubing has been associated with systemic inflammatory response syndrome (SIRS) presents with profound refractory hypotension and capillary leak. Profound hypotension requires increased vasopressor support which causes ischemia, particularly mesenteric ischemia precipitates a cascade of decompensation. Meanwhile, third spacing through capillary leak may lead to extreme volume overload with a prolonged course of mobilizing fluids, pulmonary edema, effusions, and a protracted rehabilitation course. 32, 34

In this present case, VA ECMO was initiated after the patient failed stabilization with revascularization and hemodynamic support with the IABP. The IABP did not provide enough cardiac output support. After the RHC was performed, the patient was noted to have a PAPi that indicated the need for right ventricular support. In the setting of an emergency, with biventricular failure, implantation of VA ECMO is the most appropriate device to be implanted. VA ECMO offered this patient right sided hemodynamic support, left sided hemodynamic support and the ability to utilize acute respiratory distress syndrome (ARDS) ventilator settings during the recovery of his aspiration pneumonia that occurred during his cardiac arrest.35 Once VA ECMO was initiated, removal of the IABP in favor of the Impella CP was performed. Utilization of the Impella CP at this time was indicated as a LV vent. By venting the left ventricle, the ventricle is decompressed allowing for decreased myocardial oxygen demand and lower incident of LV thrombus if the heart is not generating enough pulsatility to eject blood through the aortic valve. Concomitant use of the Impella CP in the setting of VA ECMO has been proven to improve mortality.36

Percutaneous RVAD

In the presented case, the percutaneous right ventricular device utilized was the ProtekDuo. The ProtekDuo is a dual-lumen percutaneous device that is inserted via Seldinger technique, through the internal jugular vein, into the superior vena cava (SVC), right atrium, in the right ventricle and resides in the pulmonary artery.37 The ProtekDuo drains blood from the SVC. The drained blood passes through a semipermeable membrane where diffusion of CO2 and oxygen occurs. Then the blood is returned through the outflow cannula that resides in the pulmonary artery. Essentially, the preload is drained from the right ventricle, bypassing it and delivering the preload to the left ventricle. Thus, the RVAD hemodynamically supports right sided dysfunction without giving left sided hemodynamic support. This particular product also supports ventilation and oxygenation. At the present time, there are two widely available percutaneous right ventricular support devices. In the presented case the decision to utilize the ProtekDuo over the other available device is because of the availability to splice in an oxygenator to the circuit. In addition to RV support, the patient required ventilation and oxygenation support due to severe hemoptysis. The hemoptysis was attributed to pulmonary hemorrhage and coagulopathy secondary to severe liver dysfunction. As the pulmonary hemorrhaging resolved, more reliance on the ventilator could be achieved; therefore, leading to the decreased need of the gas exchange component provided by the ProtekDuo. Furthermore, the liver slowly returned to baseline secondary to adequate continued hemodynamic support. In the present case, the ProtekDuo was utilized as a long-term RV mechanical support device. The patient’s LV status regained normal function; however, the patient’s RV and pulmonary status were still compromised. The RVAD provided this patient the ability to receive the hemodynamic support that was needed, without the sequela of extended utilization of VA ECMO. Furthermore, by shifting to the RVAD, the patient’s mobility status improved as a patient has an increased ability to be out-ofbed and ambulate compared to VA ECMO. By utilizing this device during this patient’s hospital course, the study institution was able to improve other aspects of patient recovery such as mental status, ambulation, return of bowel function, and decannulation from the ventilator while still maintaining hemodynamic support.

Conclusion

In summary, the case presented offers a detailed look into the decision making, indications and limitations of different mechanical circulatory devices that are utilized in a complex cardiogenic shock course. Each circulatory device offers its own strengths, weaknesses, indications, and complications that must be navigated by the Shock Team in order to increase chances of patient survival. By understanding the process of identifying shock, evaluating patient needs, and executing decision making, proper patient-device matching can be achieved in hope of improving overall mortality and morbidity in cardiogenic shock.

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