Srivisatava – mechanical support 1-18-18

written by Scott Sullivan, MD

Today it is my pleasure to introduce Dr. Mukta Srivastava. She is the Cardiology Fellowship Program Director and an interventionist actively involved in the insertion and management of these devices. Dr. Srivastava did her undergraduate work at Johns Hopkins University, then went to Virginia for medical school, and Yale for residency.  She has been at University of Maryland for a couple of Cardiology Fellowships and we have been lucky enough to keep her here!

Clinical Pearls

• Indications for Mechanical Circulatory Support:
  • AMI with Cardiogenic Shock
  • Acute Decompensated Heart Failure
  • Acute Cardiac Allograft Failure
  • Post-transplant RV Failure
  • Post-cardiotomy Shock
  • Refractory Arrhythmias
  • High Risk – PCI
  • High Risk – EP Procedure
  • High Risk – Structural Interventions
• Who Needs Mechanical Circulatory Support?
  • Clinical Features
    • LVEF <30-40%
    • Prior CVA, DM, CKD, Chronic Lung Disease
    • Present in Cardiogenic Shock, STEMI, or ACS with unstable features
  • Anatomical Features
    • Left Main Coronary (or Equivalent) Intervention
    • Multi-Vessel Disease
    • Bifurcation Lesions
    • Degenerated Saphenous Vein Grafts
    • Last Conduit
    • Target Vessel subtending >40% of myocardium
    • Syntax Score > 33
  • Hemodynamic Parameters
    • Cardiac Index < 2.2 on Pressors or < 1.8
    • Elevated Pulmonary-Capillary Wedge Pressure
    • Pressor Requirement
    • Or anticipated dysrhythmias, transient intervals of ischemia-reperfusion injury during PCI, or no re-flow (high risk of complication/dissection during procedure) once interventions commence
• Contraindications:
  • Terminal Illness
  • Bleeding Diathesis
  • Severe Peripheral Vascular Disease/Abdominal Aortic Aneurysm
  • Aortic Regurgitation
  • Age Considerations
  • Multi-Organ Failure
• Slope of Emax = contractility of ventricle. Thus, in conditions of depressed myocardial function as the Slope decreases, Contractility decreases. This decreases the stroke volume.
  • As this progresses to Cardiogenic Shock, this depression in contractility is increased and there is increase in end diastolic pressures as the heart produces less forward output.
  • This in turn increases LV work/Myocardial O2 consumption, leading to decreased coronary blood flow and coronary ischemia.
• The SHOCK Trial – Cardiac Power: MAP * CO / 451, this measurement most strongly correlated with mortality
• Mechanical Circulatory Support Physiology Goals
  • Should maintain/Augment vital organ perfusion (MAP)
  • Improve coronary perfusion
  • Reduce intra-cardiac filling pressures (LVEDP/PCWP)
  • Reduce MVO2
• Coronary Perfusion
  • Determined by the pressure gradient between Ao and RAP
  • The other factor to consider is micro-vascular resistance, which is actually increased in acute MI secondary to: vasoconstriction, micro-emboli, ischemia reperfusion injury, increased LVEDP
• Modalities of Mechanical Circulatory Support
  • IABP
  • Impella
  • Tandem Heart
  • ECMO
• Intra-Aortic Balloon Pump (IABP)
  • Concept of Counter Pulsation
    • When LV is contracting, the balloon is deflating
    • When LV is in diastole, the balloon is inflating
  • Active inflation augments diastolic flow (increase in MAP and CBF)
  • Active deflation reduces afterload (decreases LVEDP and work)
  • The support is dependent on the volume of blood (0.3 – 0.5L)

• Requires stable rhythm

• IABP is a Class IIa recommendation for Cardiogenic Shock complicating AMI; Links to IABP Trials:
  • BCIS-1 Trial – Elective IABP before High Risk PCI: No significant difference in Major Adverse Cardiovascular and Cerebrovascular Events (MACCE) at 28 days or 6-month mortality; BUT 5-year all-cause mortality in the IABP group had lower mortality (however not properly powered to look at mortality).
  • CRISP-AMI Trial – Anterior MI Patients without cardiogenic shock, IABP placed prior to PCI vs. provisional use, looked at LV infarct size by MRI at 3-5 days and found no significant difference.
  • IABP-SHOCK II-Trial – AMI with Cardiogenic Shock, looked at 30-day all-cause mortality and found no significant difference.
• Impella
  • Larger than a balloon pump (13 – 21 French)
  • Provides active unloading of LV – moves volume from LV to the Aorta
    • Reduces LVEDP, LVEDV, wall tension, and MVO2
  • Improves MAP, CO, Cardiac Power, and Coronary Perfusion
  • Reduces Pulmonary Capillary Wedge Pressure à unloading of RV
  • Load, not rhythm dependent
  • Ventricle-Aorta gradient impacts flow
• Impella Literature:
  • Protect II
    • IABP vs. Impella in non-emergent high-risk PCI: Showed no difference in 30-day major adverse events

• Tandem Heart
  • 4-5L support
  • Femoral Vein/Trans-Septal 21 Fr Access
  • Femoral Artery Access 17 Fr
  • This system bypasses the Left Ventricle
  • Complications: Limb Ischemia, Hemolysis, Longer Implant Times, Complex Management, and requires a Trans-Septal Puncture
  • Two RCTs in AMI with Cardiogenic Shock show no mortality benefit when compared with IABP
• ECMO
  • Parallel circuit providing cardiopulmonary bypass
  • Some of the flow is shunted through a circuit that can oxygenate blood and return it to the circulation
  • Complications: Hemolysis, Limb Ischemia, CNS Events
  • *This can increase afterload on LV