When should Impella 5.5 (intra-aortic cardiac support device) be used in patients?

Impella 5.5 Clinical Indications and Use

The Impella 5.5 should be used in patients with severe cardiogenic shock requiring prolonged mechanical circulatory support (>14 days) as a bridge to heart transplantation, durable left ventricular assist device, or myocardial recovery, particularly in those with heart failure-related cardiogenic shock or acute myocardial infarction who need higher flow support than smaller Impella devices can provide. 1, 2

Device Specifications and Capabilities

• The Impella 5.5 is a micro-axial flow transaortic cardiac support device mounted on a 9 Fr steering catheter with a 21 Fr pump cannula, capable of delivering up to 5.5 L/min of flow 1, 3
• The device requires surgical placement of a conduit graft (typically axillary artery) for endovascular delivery, unlike the smaller percutaneous Impella models 3
• The Impella 5.5 is approved for 30 days of support in Europe (CE mark) and 14 days in the United States (FDA approval), though clinical use frequently extends beyond these durations 1, 2

Primary Clinical Indications

Cardiogenic Shock Etiologies

• Heart failure-related cardiogenic shock (HF-CS): This represents the most common indication, with 78% of patients supported >14 days having HF-CS rather than MI-related shock 2
• Acute myocardial infarction with cardiogenic shock: Ischemic cardiomyopathy and acute MI account for 47.8% of Impella 5.5 implantations 1
• Postcardiotomy cardiogenic shock: The device provides suitable treatment for severe postcardiotomy shock refractory to conventional therapy 4
• Acute-on-chronic heart failure: Approximately 50% of patients have acute decompensation of chronic heart failure 1

Bridge Strategies

• Bridge to heart transplantation: 58% of patients supported >14 days were successfully bridged to heart replacement therapies, compared to 38% in those supported ≤14 days 2
• Bridge to durable LVAD: 41.3% of patients were successfully bridged to durable mechanical circulatory support devices 1
• Bridge to recovery: 34.8% of patients achieved native heart recovery and were successfully weaned from the device 1, 5

Patient Selection Criteria

Ideal Candidates

• Younger patients: Mean age 57-59 years in successful cohorts, with those supported >14 days being significantly younger (57 vs 61 years) 1, 2, 5
• Dilated cardiomyopathy: Patients with larger left ventricular end-diastolic dimensions (6.4 cm vs 5.9 cm) are more likely to require prolonged support 2
• SCAI shock stage D or E: The majority of patients (63 of 64 in one series) were classified as SCAI class D or E, representing severe cardiogenic shock 5
• Patients requiring flow >2.5 L/min: Those with large body mass index or severe shock who exceed the capacity of smaller Impella devices 6

Contraindications

• Absolute contraindications: Left ventricular thrombus, severe aortic stenosis, significant aortic insufficiency, severe peripheral artery disease, or aortic dissection 7, 8
• Relative contraindications: Severe aortic valve disease that may be damaged by prolonged device placement 1

Clinical Outcomes and Survival Data

Short-Term Outcomes (30-90 Days)

• 30-day survival: 73.9% (95% CI: 63.3-88.9%) in the initial CE mark approval cohort 1
• 90-day survival: 71.7% (95% CI: 60.7-87.1%) in the same cohort 1
• Favorable outcomes in prolonged support: 75% of patients supported >14 days achieved favorable outcomes (recovery, bridge to HRT, or discharge alive) 2

Prolonged Support Outcomes (>14 Days)

• Overall survival with prolonged support: 80% survival in patients supported >14 days, compared to 68% in those supported ≤14 days 2
• Single-center experience: 81.3% overall survival (including heart recovery, OHT, or LVAD) in patients supported beyond 14 days 5
• Mean duration of support: 15.5-27.1 days, with some patients supported up to 164 days 1, 5

Complications and Adverse Events

Major Complications

• Pump thrombosis: Occurs in 15.2% of patients, requiring careful anticoagulation management 1
• Device exchange: Required in 19.6% of patients due to malfunction or thrombosis 1
• Bleeding requiring transfusion: Affects 34.8% of patients during the entire treatment course 1
• Inflow cannula dislocation: Occurred in 21.7% of patients in early series, though this has been addressed by design changes 1

Favorable Safety Profile

• Thromboembolic complications: Only one stroke noted in the initial 46-patient cohort, with no other thromboembolic events 1
• Aortic valve damage: No aortic valve damage observed in the study cohort 1
• Serious adverse events: Only 19.1% of patients supported >14 days experienced serious adverse events, with no linear increase in SAE rates with prolonged duration 2

Anticoagulation Management

• Initial bolus: Administer unfractionated heparin 100 U/kg (maximum 5000 U) at the time of implantation to prevent pump thrombosis 7
• Ongoing anticoagulation: Maintain therapeutic anticoagulation throughout support duration, balancing thrombotic risk (pump thrombosis 15.2%) against bleeding risk (34.8% requiring transfusion) 1

Advantages Over Alternative Devices

Compared to Smaller Impella Models

• Higher flow capacity: Provides 5.5 L/min versus 2.5 L/min (Impella 2.5) or 3.5-4.0 L/min (Impella CP), enabling complete left ventricular support 6, 3
• Longer duration of support: Designed for 30 days versus shorter durations for percutaneous models 1
• Patient mobilization: Axillary placement enables patient mobilization, rehabilitation, and ambulation (32.6% ambulatory in one series) 1, 3

Compared to IABP

• Greater hemodynamic support: Provides direct cardiac output augmentation and superior left ventricular unloading compared to IABP's minimal support 7, 8
• No contraindication with aortic insufficiency: Unlike IABP, can be used in patients with mild-moderate aortic insufficiency 8

Compared to VA-ECMO

• Avoids left ventricular distension: Provides direct LV unloading without requiring additional venting strategies needed with VA-ECMO 7
• Less invasive than surgical VAD: Comparable 30-day survival to surgically implantable VADs (39.5% in postcardiotomy shock) with much less invasive placement 4

Clinical Algorithm for Impella 5.5 Deployment

Step 1: Identify Severe Cardiogenic Shock

• Confirm SCAI stage D or E shock with inadequate response to medical therapy and smaller mechanical support devices 5
• Assess for need of flow >2.5-4.0 L/min based on body size and degree of shock 6

Step 2: Determine Bridge Strategy

• If potential for recovery: Consider Impella 5.5 for bridge to recovery in acute MI, myocarditis, or acute-on-chronic HF 1, 5
• If advanced HF candidate: Use as bridge to heart transplantation or durable LVAD in younger patients with dilated cardiomyopathy 2, 5
• If postcardiotomy shock: Deploy rapidly for refractory postcardiotomy cardiogenic shock 4

Step 3: Exclude Contraindications

• Perform echocardiography to rule out LV thrombus, severe aortic stenosis, or significant aortic insufficiency 7, 8
• Assess peripheral vasculature for severe peripheral artery disease or aortic dissection 7, 8

Step 4: Plan Surgical Access

• Arrange for surgical placement of axillary artery conduit graft for device insertion 3
• Ensure surgical team availability for potential complications or device exchange 1

Step 5: Anticipate Prolonged Support

• Plan for support duration >14 days in patients with HF-CS, younger age, and dilated LV 2, 5
• Prepare for potential bridge to advanced therapies given 58% bridge-to-HRT rate in prolonged support cohort 2

Important Clinical Caveats

• Duration beyond FDA approval: While FDA-approved for 14 days, clinical data supports safe and effective use beyond this duration, with 75% favorable outcomes in patients supported >14 days 2, 5
• Early design limitations: Initial versions had 21.7% cannula dislocation rates, but this has been addressed by design modifications 1
• Mobilization potential: Unlike other high-flow devices, axillary placement enables patient mobilization and rehabilitation, which may improve outcomes 1, 3
• Not for routine use: This device is NOT indicated for routine prophylactic support in stable ischemic heart disease undergoing PCI, where mechanical support has not shown mortality benefit 8