DOI: 10.5281/zenodo.18214525
title: Predictors of Survival and Successful Weaning from Short-Term Mechanical Circulatory Support in Acute Myocardial Infarction Complicated by Cardiogenic Shock: Insights from Contemporary Studies and Registries

description:  

Background: Acute myocardial infarction complicated by cardiogenic shock (AMI-CS) remains a life-threatening condition with persistently high mortality despite advances in revascularization and temporary mechanical circulatory support (MCS). Devices such as Impella, venoarterial extracorporeal membrane oxygenation (VA-ECMO), and intra-aortic balloon pump (IABP) are increasingly used to stabilize hemodynamics, but predictors of survival to discharge and successful weaning (recovery of native heart function without need for durable MCS or transplantation) are incompletely understood. Early studies highlighted age and cardiac index as key factors, but recent data emphasize the role of timely intervention, metabolic status, and device-specific complications.

Objective: To synthesize current evidence on predictors of survival and ability to wean from short-term MCS in AMI-CS patients, incorporating findings from registries (e.g., National Cardiogenic Shock Initiative [NCSI]), meta-analyses, and observational studies up to 2026, while addressing evolving device utilization and weaning protocols.

Methods: This review integrates data from key publications (2018–2025), including retrospective cohorts, propensity-matched analyses, and prospective registries involving patients supported with Impella, VA-ECMO, or combined strategies. Outcomes focused on in-hospital/30-day survival, weaning success (defined as device removal with sustained hemodynamic stability and native heart recovery), and post-weaning events (e.g., mortality or MCS reinitiation). Multivariable models from source studies identified independent predictors, adjusted for confounders like age, comorbidities, and shock severity (e.g., SCAI stage, IABP-SHOCK II score).

Results: Survival to hospital discharge in AMI-CS patients on short-term MCS ranges from ~50–71% in contemporary cohorts, with higher rates (~71–79% in SCAI stage C/D) when early MCS (e.g., Impella pre-PCI) is employed per protocols like NCSI. Successful weaning occurs in 40–60% of cases, but up to 40% experience weaning failure (death within 48 hours post-removal or need for re-support).

Key predictors of survival include:

•  Younger age (protective; OR ~1.3–1.5 per 10-year increase in risk)

•  Lower baseline lactate and rapid clearance within 24 hours (strongest metabolic marker; OR 0.21 for successful weaning)

•  Higher cardiac index/power output pre- or post-MCS

•  Shorter door-to-support time and timely revascularization (PCI with TIMI 3 flow)

•  Absence of cardiac arrest or irreversible neurological injury

Predictors of successful weaning (from recent weaning scores and protocols):

•  Higher mean arterial pressure (≥80 mmHg), left ventricular ejection fraction (>35%), and cardiac power output

•  Lower lactate (<10 mg/dL) and QRS duration (≤95 ms)

•  Absence of AMI etiology (protective in some models), renal replacement therapy, multiple vasoactives, or persistent congestion (e.g., elevated PAWP)

Device comparisons show no consistent survival benefit for Impella over IABP in unselected patients, with Impella linked to higher bleeding/limb complications. VA-ECMO weaning fails in ~40%, often due to age, cardiac arrest, and complications like bleeding or renal failure. Novel tools like the UNLOADERS-PVAD score (incorporating sex, renal therapy, vasoactives, lactate, HR, PAWP, CPO) and simple weaning models improve risk stratification.

Conclusions: In AMI-CS, survival and weaning from short-term MCS depend on patient age, metabolic recovery (lactate clearance), hemodynamic status (cardiac index/power), and procedural timing. Early MCS initiation, guided by invasive monitoring and standardized protocols, improves outcomes, but ~40–50% of patients require escalation to durable therapies or face weaning failure due to irreversible injury or complications. Future randomized trials should focus on selective patient recruitment, multimodal weaning algorithms, and device optimization to further enhance recovery rates.

Keywords: Acute myocardial infarction, cardiogenic shock, mechanical circulatory support, Impella, VA-ECMO, weaning predictors, survival, lactate clearance, cardiac power output, National Cardiogenic Shock Initiative.