The evolving landscape of Impella use in the United States among patients undergoing percutaneous coronary intervention with mechanical circulatory support

Selected in Circulation by M. Alasnag , M. Alasnag

The use of MCS has been increasing over the last 10 years. This study mainly aims at defining the indications for Impella use in the U.S as well as comparing the outcomes, costs, and length of stay in the pre-Impella versus Impella era.

Reviewers

Manal Alasnag

@manalalasnag

Consultant Pediatric Intensivist

King Fahd Armed Forces Hospital - Jeddah, Saudi Arabia

Mirvat Alasnag

@mirvatalasnag

Interventional cardiologist / Cardiologist

King Fahd Armed Forces Hospital - Jeddah, Saudi Arabia

Our Comment

Why this study – the rationale/objective?

In daily practice, the use of mechanical circulatory devices (MCS) has been steadily increasing over the last decade. As a result of the lack of robust randomized data, its use remains at the discretion of the individual operator with no guideline recommendations to date. This article explores the following:

1. Indications for Impella use (shock and Complex High-Risk Indicated Procedure (CHIP)) in the United States
2. Outcomes for Impella and intra-aortic Balloon Counterpulsation (IABP) with respect to in-hospital mortality, bleeding, acute kidney injury and stroke
3. Variation in outcomes, costs, and length of stay
4. Comparison of outcomes, costs, and length of stay in the pre-Impella versus Impella era (also analysis for low vs high use hospitals).

How was it executed – the methodology?

An analysis of 48,306 patients undergoing percutaneous coronary intervention (PCI) with MCS from the Premier Healthcare Database at 432 hospitals in the United States between January 2004 and December 2016 was performed at 3 levels. Time period, hospital, and patient. Mixed effects modeling (hierarchical models) and propensity score adjustments were used for association. Temporal trends and use in critically ill patients were also defined.

What is the main result?

A total of 4782 patients undergoing PCI received Impella (9.9% of the total cohort). IABP accounted for 90.1% of the total receiving MCS (43, 524). A temporal increase in use over time was observed, reaching 31.9% of MCS in 2016. There was >5-fold variation in Impella use across hospitals. Similarly, there was a wide variation in outcomes:

• Bleeding >2.5-fold variation
• Death, acute kidney injury, and stroke all ≈1.5-fold variation
• Adverse outcomes and costs were higher in the Impella era (2008-2016)
• Steady or slight decrease in IABP use in the Impella era (2008-2016)
• Hospitals with higher Impella use had higher rates of adverse outcomes and costs (but shorter in-hospital stay)

Using propensity score adjustments and accounting for clustering by hospitals, Impella use was associated with the following:

• Death: odds ratio, 1.24 (95% CI, 1.13-1.36)
• Bleeding: odds ratio, 1.10 (95% CI, 1.00-1.21)
• Stroke: odds ratio, 1.34 (95% CI, 1.18-1.53)
• Acute kidney injury: odds ratio, 1.08 (95% CI, 1.00-1.17)

The reported comorbidities in this observational dataset was high; heart failure (50%), chronic renal failure (20%), diabetes mellitus (40%), chronic obstructive pulmonary disease (20%), and atrial fibrillation (23%). Critically ill patients with cardiogenic shock were 50% of the total cohort; 38% were on mechanical ventilation; 62% presented with ST-segment-elevation myocardial infarction and 26% underwent multivessel PCI.

Those receiving Impella were more likely to be male, nonwhite, and had a higher prevalence of diabetes mellitus, heart failure, chronic kidney disease, chronic obstructive pulmonary disease and multivessel disease. They were also more likely to receive ticagrelor and bivalirudin.

Those in cardiogenic shock, requiring mechanical ventilation or had a cardiac arrest were less likely to receive an Impella device. Compared to IABP, use of an Impella device was higher in those undergoing complex interventions that included laser atherectomy (3.4% vs 14%), rotational atherectomy (1.3% vs 7.1%) or had complex anatomy eg chronic total occlusions (7% vs 22%).

Critical reading and the relevance for clinical practice

The data presented is observational; nevertheless, it provides a clear understanding of temporal changes in the application of MCS with an overview of adverse outcomes and cost. There is an unexpectedly high use in CHIP and low use in critically ill and shock patients in the United States. In spite of a reduction in overall PCI costs, the cost of adding MCS to complex PCI has undoubtedly driven the cost in this analysis. This is, however, a strictly US based dataset that may not reflect global use.

Generally, European and Asian centers have a higher threshold for MCS. As an example, the IMP-IT registry is a multicenter observational study from Italy where 56.4% of MCS use was in shock and 43.6% in CHIP cases. The in-hospital and 1-year mortality of the shock patients remained high irrespective of the MCS device used (46.9% and 57.0% respectively) in this registry. All these registries are confounded by the variable definition of shock, variable time to MCS, expertise in the management of shock in the intensive care unit and not only the catheterization laboratory and expertise in the management of large bore access.

When discussing MCS, it is important to understand that multiple devices are available ranging from IABP to ECMO; therefore, the discussion shouldn't be limited to Impella. There are few head to head comparisons of devices in the setting of shock. The PROTECT II trial compared IABP to Impella in CHIP, not shock.

A retrospective study by Karami et al from two centers evaluated the role of Extra-corporeal membrane oxygenation and Impella in acute myocardial infarction and shock. It showed comparable mortality for both devices with a lower complication rate for Impella.

An important ongoing trial is the DanGer Shock study that randomized patients presenting with acute MI and shock to Impella to standard therapy alone. The preliminary data suggests those in profound shock were enrolled (mean lactate 5.5 mmol/L, median systolic blood pressure of 76 mmHg and median LV ejection fraction of 20%).

Other understudied populations with high mortality are those with outside of hospital arrest and right ventricular failure. They are largely excluded from major trials.

Interestingly, the Cardiogenic Shock initiative reports an unprecedented reduction in mortality in shock. This initiative emphasizes early MCS support and provides a standardized pathway that is guided by parameters such as lactate levels and PAPi. It also defines protocols for the escalation and de-escalation of therapy.

More recently, the Society of Cardiovascular Angiography and Interventions (SCAI) released a new definition of shock. A randomized study with a standardized definition of shock (all stages) and standardized protocol is important to truly determine whether MCS can positively impact mortality. Until then, observational data suggests more rationed use of MCS is necessary.