Clinical Trial Finds Pump Not Effective for Reducing Heart Damage in Severe Heart Attacks

A recent clinical trial indicated that using a microaxial flow pump before and during cardiac stenting procedures for patients experiencing severe heart attacks without cardiogenic shock did not significantly reduce heart damage.

This was the primary conclusion of "The STEMI-Door to Unload (DTU)" trial, the first study of its kind to investigate the impact of resting the heart to reduce heart attack size in high-risk patients.

Dr. Gregg W. Stone, Professor of Medicine (Cardiology) at the Icahn School of Medicine at Mount Sinai, presented these results on March 28 at the American College of Cardiology Scientific Sessions. The findings were also published simultaneously in the Journal of the American College of Cardiology.

Understanding the Challenge: STEMI and Infarct Size

STEMI (ST-segment elevation myocardial infarction) represents the most severe type of life-threatening heart attack, caused by a sudden blockage in a major coronary artery. Urgent percutaneous coronary intervention (PCI), involving the placement of stents to restore blood flow, is crucial for these patients.

While interventional cardiologists are effective at unblocking arteries, reducing the size of the heart attack, or infarct, remains a significant challenge. This often leads to heart failure or mortality.

Experimental studies over decades have suggested that using a flow pump to eject blood from the heart's pumping chamber could rest the heart, improve blood flow, and potentially reduce damage. The DTU trial aimed to test this hypothesis.

Study Design and Key Results

The trial focused on the Impella CP device, an FDA-approved catheter-based microaxial heart pump. Researchers investigated the device in 527 patients with confirmed anterior STEMI who were not in cardiogenic shock.

Patients were randomized into two groups: one received the Impella CP and delayed PCI, while the other received immediate PCI without the Impella device.

The primary effectiveness endpoint was a reduction in infarct size, measured by cardiac MRI three to five days post-procedure. The primary safety endpoint evaluated the rate of major bleeding or major vascular complications.

The results indicated that infarct size, expressed as a percentage of total left ventricular mass, was slightly lower in the Impella group (mean 30.8% ± 16.2%) compared to the immediate PCI group (31.9% ± 16.9%). However, this difference was not statistically significant.

Notably, infarct size in Impella patients did not increase despite a delay of approximately 47 minutes in total ischemic time. Bleeding and vascular complications were more frequent in the Impella CP group, occurring in 30.8% of patients, which exceeded the predefined performance goal of 26.5%. Differences in cardiovascular mortality between the groups were not statistically significant.

Conclusion and Future Directions

Based on these findings, routine use of the microaxial flow pump is not currently recommended for patients with evolving heart attacks who are not in cardiogenic shock.

While the device did not significantly decrease infarct size, it also did not increase it despite procedure delays, suggesting some beneficial effects on myocardial recovery. Future studies may explore the pump's use in conjunction with pharmacologic or other therapies for high-risk, non-shock heart attack patients.

Abiomed provided funding for this study.