Multicenter Prospective Assessment of Coronary Microvascular Dysfunction: Primary Results of the FlowLab Study

Area of Science:

• Cardiology
• Vascular Medicine
• Diagnostic Testing

Background:

• Coronary microvascular dysfunction (CMD) and vasospastic angina (VSA) are prevalent but frequently underdiagnosed conditions.
• Current understanding of invasive CMD/VSA assessment is limited by specific patient selection and procedural techniques, with less known about real-world application.

Purpose of the Study:

• To observe procedural and therapeutic decision-making processes in patients undergoing invasive assessment for CMD/VSA.
• To evaluate the real-world utilization of diagnostic testing for CMD/VSA.

Main Methods:

• The FlowLab study prospectively enrolled patients with suspected CMD at 14 U.S. sites.
• The CoroFlow bolus thermodilution system was used to measure coronary flow reserve and index of microcirculatory resistance (IMR).
• Procedural techniques, including vasospasm testing, were at the operator's discretion to reflect current practice.

Main Results:

• 253 procedures were performed, with chest pain and dyspnea as common presenting symptoms.
• Abnormal coronary flow reserve (<2.5) was found in 43% of patients, and abnormal IMR (≥25) in 28%.
• CMD/VSA was diagnosed in 53% of patients, with 61% of those with elevated IMR receiving additional anginal therapy.

Conclusions:

• Invasive testing for CMD/VSA demonstrated varied procedural approaches but was rapid, yielding common diagnoses.
• The findings indicate immediate implications for patient management following diagnosis.
• Further integration of CMD/VSA evaluation is recommended to address diagnostic and therapeutic gaps.