Dhiran Verghese, MD; Saraschandra Vallabhajosyula, MD, MSc; and Konstantinos Dean Boudoulas, MD, FSCAI

Introduction

Cardiogenic shock (CS) is a state of progressive end-organ hypoperfusion due to low cardiac output caused by a primary cardiac dysfunction.¹ CS can rapidly spiral and progress to multiorgan failure without timely correction of the underlying etiology and appropriate hemodynamic support. There has been a growing body of evidence supporting early recognition of CS with hemodynamic profiling, escalation to appropriate mechanical circulatory support (MCS), and development of multidisciplinary teams leading to improvement in clinical outcomes.^2,3

Recognition of CS

Appropriate profiling of patients is vital for assessment of initiation and escalation/weaning of MCS. This can effectively be achieved using clinical and hemodynamic data supplemented by echocardiography and/or pulmonary artery catheter (PAC) information, when available. Furthermore, the Society for Cardiovascular Angiography and Interventions’ (SCAI’s) stages of shock provide a stepwise mortality risk stratification and can be useful in selecting optimal timing for MCS, with data supporting use of MCS in SCAI stages C or greater being the most appropriate (see Figure 1).^4,5 Accurate profiling in patients indicating a deteriorating stage B despite initial stabilization and optimized efforts directed to the underlying CS etiology may additionally warrant candidacy for early MCS initiation to prevent interval worsening of the hemometabolic cascade. Implementation of a multidisciplinary shock team, comprising of an interventional cardiologist, heart failure cardiologist, critical care physician, and cardiothoracic surgeon, participating together in decisions and management of patients with CS has shown to improve outcomes.^2,6 Development of shock teams tailored to local resources should be encouraged at centers aiming to provide high-quality care for patients with CS. Given the heterogeneity of CS, a one-call activation of the team with well-integrated protocols and consensus-driven decisions can improve survival of patients with CS.^7,8

Comprehensive Profiling of Patients for the Need of MCS

1. Clinical assessment – Cool extremities, peripheral edema, altered mentation, and oliguria
2. Hemodynamic parameters – Systolic blood pressure <90, cardiac index ≤2.2 L/min/m², heart rate >100 beats/min
3. Metabolic derangements – Lactate > 2 mmol/L, pH <7.35
4. Echocardiographic findings – Severe left ventricular (LV) dysfunction (de novo LVEF <25%), severe right ventricular (RV) dysfunction, large territory of regional wall motion abnormality, and severe acute valvulopathy
5. Pulmonary artery catheter (PAC) monitoring – Pulmonary capillary wedge pressure (PCWP) ≥15 mmHg, pulmonary artery pulsatility index (PAPI) < 1.0, mixed venous oxygen saturation (SvO2) < 60%, cardiac power output (CPO) <0.6 watts, Fick cardiac index < 2.2 L/min/m², central venous pressure (CVP) >15 mm Hg, and CVP/PCWP >0.63 mm Hg

CS is a dynamic process, and escalation of the SCAI stage from the initial presenting baseline stage is common.⁹ Time to escalation varies significantly based on the baseline SCAI stage and underlying etiology.⁹ A recent analysis from the Cardiogenic Shock Working Group (CSWG) demonstrated the importance of early and continuous staging throughout the course of the hospitalization.⁹ This highlights the importance of accurate profiling of patients throughout all phases of CS and can be achieved by integrating parameters from clinical, hemodynamic, biochemical, and imaging criteria mentioned above. Furthermore, progression using the SCAI CSWG shock stage measures, employing well-defined thresholds incorporating lactate (<2, 2–5, 5–10, >10 mmol/L), alanine transaminase (<200, 200–500, >500 IU/L), pH (<7.2 or >7.2), and systolic blood pressure (<60, 60–90, >90 mmHg) could provide a clinically actionable framework that can be easily implemented across hospitals.

Most Commonly Used Temporary MCS Devices

• Intra-aortic balloon pump (IABP)
• Percutaneous LV assist devices (pLVAD) (LV support – Impella, TandemHeart; RV support – Impella RP, Protek Duo)
• Extracorporeal membrane oxygenation (ECMO)

There are a number of MCS devices available in the contemporary era. For patients with LV failure, IABP and pLVAD’s, including Impella and TandemHeart, are available in the U.S. and provide different levels of support (see Figure 2). The Impella RP and Protek Duo provide RV support (see Figure 3). Protek Duo offers the additional benefit of the ability for the addition of an oxygenator in cases of concomitant respiratory insufficiency.¹⁰ In patients with biventricular failure, a combination of biventricular Impella pumps, a combination of Impella and Protek Duo, or the more commonly employed venoarterial ECMO (VA-ECMO) can be used. In patients with biventricular and concomitant respiratory failure, VA-ECMO should be considered. Additional LV venting can be considered in patients on ECMO who have elevated PCWP, elevated pulmonary arterial diastolic pressure, and distended hypocontractile LV, using IABP or Impella to decrease the LV myocardial oxygen demand, lower the afterload, and facilitate myocardial recovery.¹¹

pLVADs provide greater augmentation of the cardiac output compared to IABP. There has been a significant increase in the use of pLVADs over the past decade with a decline in the use of IABP, notwithstanding limited randomized control trial (RCT) data in this space demonstrating neutral results.^12–14 Furthermore, positive hemodynamic effects were noted in the ISAR-SHOCK trial but not in the IMPERESS in Severe Shock trial. However, data from dedicated shock centers and multicenter registries have demonstrated improved outcomes with MCS when deployed in a timely manner using invasive hemodynamics, multidisciplinary shock teams, and standardized algorithms.^6,5,16

Temporary MCS is used as a bridge to myocardial recovery, bridge to decision, or a temporizing measure to assess candidacy for a durable ventricular assist device implantation or cardiac transplant. Device selection should be guided by the degree of circulatory support needed, underlying etiology, CS phenotype, anticipated duration, and institutional familiarity with the device. An exception is patients with ongoing CPR in whom ECMO/Extracorporeal Life Support (ECLS) has been specifically shown to improve outcomes in certain instances and, therefore, may be considered in this scenario.¹⁷

Temporary MCS use is approved from a few hours to 30 days depending on the device.⁵ However, readiness to wean should be assessed daily with a goal directed toward early explanation, whenever feasible. Rapid LV recovery post-revascularization may allow for early weaning and explant of MCS in acute myocardial infarction (AMI) complicated by cardiogenic shock (AMI-CS). Employment of algorithms with timely profiling and early initiation of MCS can improve outcomes in patients with AMI-CS.^2,15 A proposed algorithm for CS management and MCS selection in AMI has been presented in Figure 4.

Conclusion

MCS allows for rapid restoration of tissue perfusion in patients with CS. pLVADs provide greater hemodynamic support compared to IABP, and there has been a rise in use of pLVADs. Multicenter registries and real-world studies have reported improved outcomes with hemodynamic profiling and early MCS in patients with CS. There are several ongoing randomized and large-scale registry studies on the use of MCS, which will shed further light on this important topic.

References

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Figure 1. Society for Cardiovascular Angiography and Intervention classification of cardiogenic shock

Abbreviations: AMI: Acute myocardial infarction; SCAI: Society for Cardiovascular Angiography and Intervention

Figure 2. Left ventricular mechanical circulatory support devices

Abbreviations: IABP: Intra-aortic balloon pump; LA: Left atrial; LV: Left ventricle; MCS: Mechanical circulatory support; VA: Venoarterial ECMO: Extracorporeal membrane oxygenation

Figure 3. Right ventricular mechanical circulatory support devices

Abbreviation: MCS: Mechanical circulatory support

Figure 4. Proposed algorithm for acute myocardial infarction with cardiogenic shock evaluation and management

Abbreviations: CI: Cardiac index; CICU: Cardiac intensive care unit; CPO: Cardiac power output; ECHO: Echocardiogram; LV: Left ventricular; LVEDP: Left ventricular end-diastolic pressure; MCS: Mechanical circulatory support; PA: Pulmonary artery; PAC: Pulmonary artery catheterization; PAPI: Pulmonary artery pulsatility index; PCI: Percutaneous coronary intervention; PCWP: Pulmonary capillary wedge pressure; RV: Right ventricular; RWMA: Regional wall motion abnormalities; SBP: Systolic blood pressure; SvO2: Venous oxygen saturation; VAD: Ventricular assist device