The index of microcirculatory resistance (IMR) in takotsubo cardiomyopathy

Area of Science:

• Cardiology
• Cardiovascular Physiology
• Diagnostic Imaging

Background:

• Acute chest pain and elevated cardiac enzymes often indicate acute coronary syndrome (ACS).
• Takotsubo cardiomyopathy, or stress-induced cardiomyopathy, presents similarly but with normal coronary arteries.
• Microcirculatory dysfunction plays a role in various cardiac conditions.

Observation:

• A patient presented with symptoms consistent with ACS, including acute chest pain and positive cardiac enzymes.
• Coronary angiography showed normal epicardial arteries and apical ballooning, characteristic of takotsubo cardiomyopathy.
• Invasive pressure wire measurements were performed using Fractional Flow Reserve (FFR) and Index of Microcirculatory Resistance (IMR).

Findings:

• FFR measurements were normal, indicating no significant epicardial stenosis.
• IMR measurements revealed significant microcirculatory dysfunction.
• This case is the first to invasively document microcirculatory dysfunction in takotsubo cardiomyopathy using IMR.

Implications:

• IMR provides a specific and reproducible assessment of microcirculatory function, distinct from Coronary Flow Reserve (CFR).
• These findings highlight the importance of evaluating microcirculation in patients with takotsubo cardiomyopathy.
• Invasive assessment with IMR can differentiate between epicardial and microcirculatory causes of chest pain.