Impella left ventricular assist device

Overview

Impella is a catheter-based percutaneous ventricular assist device (VAD) with a continuous axial flow pump with a propeller at the tip of the catheter, positioned in a retrograde way across the aortic valve to directly vent the left ventricle (Impella CP, 2.5, and 5.0), or inserted percutaneously through the inferior vena cava into the pulmonary artery to support the right ventricle (Impella RP).

  • Impella axial flow pump is the most recent addition for acute short-term MCS
  • continuous, non-pulsatile, axial flow Archimedes-screw pump
  • provides active support by expelling aspirated blood from the left ventricle into the ascending aorta and systemic circulation
  • percutaneously inserted transvalvular left ventricular assist device
  • placed via a retrograde approach across the aortic valve using femoral artery access or via mini-thoracotomy
  • may also be placed surgically via an 8-mm T-graft sewn to the subclavian artery or directly into the ascending aorta during cardiac surgery
  • device should straddle the aortic valve with the inflow tip (distal end of the catheter) residing in the left ventricular cavity and the outflow end in the proximal aorta
  • Unlike an IABP, the Impella does not require ECG or arterial waveform triggering, facilitating stability even in the setting of tachyarrhythmias or electromechanical dissociation
  • Reported complications: device migration, device malfunction due to thrombosis, hemolysis, bleeding requiring transfusion, arrhythmias, limb ischemia, tamponade, aortic or mitral valve injury, stroke
  • There are different versions of Impella:
    • Impella LP 2.5
      • delivers 1.5–2.5 L/min of cardiac output
      • can be placed percutaneously through the femoral artery via a 12–14 Fr sheath
    • Impella LP 5.0
      • delivers 5.0 L/min of cardiac output
      • requires surgical cutdown of the femoral or axillary artery prior to insertion of a 22 Fr sheath
    • Impella LP 5.5
      • can provide blood flow rates up to 5.0 L/min
      • require surgical insertion through the axillary or subclavian artery
    • Impella CP
      • delivers 2–4 L/min of cardiac output
      • can be placed percutaneously through the femoral artery via a 12–14 Fr sheath
    • Impella RP
      • support the right ventricle
      • inserted percutaneously through the inferior vena cava into the pulmonary artery
      • drains blood from the right atrium and ejects blood into the pulmonary artery
      • research to support Impella RP use is scarce
  • Impella works by
    • reducing left ventricular end-diastolic pressure (LVEDP) and preload
    • reduces afterload
    • reduces myocardial O2 demand
    • increases overall forward flow and MAP
    • increases coronary perfusion

Contraindications

  • severe aortic valve replacement
  • previous mechanical aortic valve replacement
  • severe peripheral vascular disease may take percutaneous deployment impossible or mandate a surgical cutdown for placement

Indications

  • high-risk PCI
  • postcardiotomy failure
  • cardiogenic shock complicating myocardial infarction
  • severe allograft rejection following heart trasplant
  • myocarditis
  • bridge to placement of a long-term device (BTR or BTT)

Impella vs. IABP

  • RCTs comparing Impella 2.5 versus IABP support in cardiogenic shock complicating myocardial infarction
    • improved hemodynamics and lab parameters (cardiac index, MAP, serum lactate levels)
    • no difference in 30-day mortality
  • PROTECT-II RCT: Impella vs. IABP for high-risk PCI
    • lower rates of the 2 composite endpoints of major adverse events (MAE) and major adverse cardiac and cerebral events (MACCE = death, stroke, MI, repeat revascularization)
    • at 3 months, rates of both composite endpoints were lower in the Impella group (MAE, 37% vs. 49%, P = 0.014; MACCE, 22% vs. 31%, P = 0.034)

REFERENCES

Windecker S. Percutaneous left ventricular assist devices for treatment of patients with cardiogenic shock. Curr Opin Crit Care 13:521–527.

Combes A, Price S, Slutsky AS, Brodie D. Temporary circulatory support for cardiogenic shock. Lancet. 2020;396(10245):199-212. doi:10.1016/S0140-6736(20)31047-3