Simple Risk Score Model Helps Wean Patients from Mechanical Circulatory Support

Patients experiencing severe heart failure or cardiogenic shock often require support from mechanical circulatory support (MCS) devices, such as venoarterial extracorporeal membrane oxygenation (VA-ECMO) or the IMPELLA heart pump. These devices help ensure adequate blood flow to vital organs when the heart is too weak to function independently. A crucial part of the recovery process for these patients is assessing when their heart has regained enough strength to operate on its own, allowing for a gradual reduction in external support or weaning off the devices. Currently, physicians determine whether a patient can be weaned off MCS by monitoring essential health indicators, including blood pressure, cardiac output, and left ventricular ejection fraction (LVEF), which assess the heart's ability to pump blood effectively. Although these parameters are recognized as important for guiding the weaning process, there is a lack of standardized protocols or guidelines, making the decision of when to safely wean patients a significant challenge. Researchers have now developed a simple risk score model that utilizes easily measurable health indicators to predict the success of MCS weaning.

Instead of relying on complicated and invasive tests to assess heart function, the method developed by researchers from Shinshu University School of Medicine (Nagano, Japan) is simple and safe, making it feasible to implement for most hospitals. In their study published in Journal of Cardiac Failure, the researchers proposed a simple risk score to predict the successful weaning of patients with cardiogenic shock from MCS. They utilized metrics that guide the weaning process from real-world clinical data to formulate the risk score. Conducting a retrospective single-center cohort study, the researchers analyzed data from 114 patients with cardiogenic shock who received treatment with either VA-ECMO or the IMPELLA heart pump between January 2013 and June 2023. They evaluated patient data and outcomes related to weaning decisions made by a multidisciplinary heart team, which included cardiologists and cardiovascular surgeons. A patient was deemed successfully weaned from MCS if the device was removed (or decannulation was performed) without the need for re-implantation and the patient survived until discharge from the hospital.

Out of the total cohort, 86 patients underwent the weaning procedure, and 55 were successfully weaned off MCS. Those who were not weaned had a higher incidence of acute myocardial infarction (AMI) and poorer health indicators. Their average blood pressure was lower (71 mm Hg) compared to those who successfully weaned (85 mm Hg), and they had a reduced pulse pressure (38 ± 20 mm Hg versus 50 ± 19 mm Hg) and weaker heart function (30% versus 40% LVEF). Additionally, they presented with elevated lactate levels in their blood (11 mg/dL versus 9 mg/dL) and longer QRS durations (106 ms vs. 92 ms), indicating slower electrical activity in the heart's ventricles. Utilizing these variables (AMI, mean blood pressure, lactate, QRS duration, and LVEF), the researchers developed two risk score formulas: one for general weaning and a simplified version.

The simplified version, known as the simple MCS weaning score, classifies patients into five groups based on their success rates by summing the points linked to each risk factor. A score of 0 or 1 indicates the absence of risk factors, corresponding to a 100% success rate; 2 points reflect two risk factors, with an 81% success rate; 3 points signify three risk factors with a 63% success rate; 4 points relate to an 11% success rate; and 5 points indicate a 0% success rate. The health indicators incorporated into the formula for this score are easily measurable with standard medical equipment, rendering the risk-scoring method practical and accessible for most hospitals.

“We propose a score model that can accurately predict successful weaning from MCS in patients with cardiogenic shock,” said Clinical Fellow Sho Suzuki who led the research team. “Interestingly, this score can be used to make bedside predictions about weaning, considering advanced therapy, or withdrawing the patient from care. We are looking forward to further research on such non-invasive methods for weaning patients and hope to establish a prediction model that successfully predicts weaning without the need for hemodynamic assessments.”

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Shinshu University School of Medicine