STORM-PE Trial: Computer-Assisted Vacuum Thrombectomy (CAVT) in Pulmonary Embolism

The STORM-PE (Randomized Controlled Trial of Mechanical Thrombectomy With Anticoagulation Versus Anticoagulation Alone for Acute Intermediate-High Risk Pulmonary Embolism) trial is a landmark study that provides evidence for the use of mechanical thrombectomy in pulmonary embolism (PE). Presented in late 2025 and published in Circulation, the trial used computer-assisted vacuum thrombectomy (CAVT) system. This endovascular therapy uses a dynamic microprocessor controlled system to aspirate thrombus while minimizing blood loss.

Key Study Details

• Population: 100 patients with acute intermediate-high risk PE (defined by RV/LV ratio ≥ 1.0 and elevated cardiac biomarkers).
• Design: International, 1:1 randomized controlled trial comparing CAVT + anticoagulation (AC) vs. AC alone.
• Primary Endpoint: Mean reduction in the right ventricular to left ventricular (RV/LV) diameter ratio at 48 hours.

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Major Findings

Metric	CAVT + Anticoagulation	Anticoagulation Alone	P-value
Mean RV/LV Reduction (48h)	0.52	0.24	< 0.001
Thrombus Burden Reduction (Refined modified Miller score)	42.1% (relative)	15.6% (relative)	< 0.001
RV/LV Normalization (48h)	39.1%	13.5%	P=0.005
Major Adverse Events (7d)	4.3% (Two PE-related deaths)	7.5%	0.681 (NS)

Clinical & Functional Outcomes

• Hemodynamic Recovery: Patients in the CAVT arm showed significantly earlier normalization of heart rate and lower supplemental oxygen requirements.
• 90-Day Mobility: The CAVT group walked significantly further in the 6-minute walk test (472m vs 376m; P = 0.019), achieving roughly 94% of their predicted distance compared to 75% in the AC group.
• Safety: There were no device-related deaths and no significant difference in major bleeding or PE recurrence between the two groups.

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Clinical Significance

The STORM-PE trial is considered “foundational” because it moves beyond single-arm registry data to prove that mechanical thrombectomy is superior to standard anticoagulation for rapidly reversing right heart strain. While it wasn’t powered to show a mortality benefit, the significant improvements in both short-term hemodynamics and long-term functional status are expected to influence future PE treatment guidelines.

Refined Modified Miller Score on CT Pulmonary angiography

While the original Miller score was designed for invasive catheter angiography, the “refined” version adapts these principles to CT Pulmonary Angiography (CTPA), allowing for a non-invasive, semi-quantitative assessment of clot resolution. Original Miller score has a cumulative range from 0-34.

Modified Miller score has a cumulative score ranging from 0 to 40. It is calculated by assigning a score of 0 for no obstruction, one for partial obstruction, and 2 for complete obstruction to each of the segmental arteries. The refined modified Miller score also has ranges from 0 to 40 but allows finer distinction of partial obstruction into 3 categories.