Correlation Between Index of Microcirculatory Resistance and Angiography-Derived Microcirculatory Resistance in Takotsubo Syndrome.

Takotsubo syndrome (TTS) is an acute stress-induced cardiomyopathy characterized by transient left ventricular dysfunction, often mimicking acute coronary syndrome (ACS). Coronary microvascular dysfunction has been implicated in its pathophysiology. The index of microcirculatory resistance (IMR) is the invasive reference standard for microvascular assessment, whereas angiography-derived microcirculatory resistance (AMR) offers a noninvasive alternative. The correlation between IMR and AMR in TTS has not yet been established. A prospective monocentric study was conducted at Clinique Saint-Hilaire, Rouen between May 2021 and May 2024. Consecutive patients admitted for ACS with angiographically non-obstructive coronary arteries and ventriculographic/echocardiographic features consistent with TTS were included. IMR was measured using a Pressure Wire X during intravenous adenosine-induced hyperemia. AMR was retrospectively derived from angiographic images using Angioplus software. Among 1738 ACS, 23 cases of TTS were identified (1.3% of ACS). After exclusions, 10 female patients (meanage 70.5 ± 6 years) were analyzed. Hypertension and overweight were the most prevalent risk factors (40%). Mean IMR was 50 (median 39 [29.25; 48.25]), positive in 8/10 patients; mean AMR was 33.4 (median 32.5 [32; 35.5]), positive in all cases. A concordant positivity between the cut off at 25 for IMR and AMR was observed in 80% of patients and in 100% of "classic" (noninverted) TTS cases. This is the first prospective study demonstrating a strong correlation between IMR and AMR in TTS. AMR appears as a reliable, faster, and less invasive alternative to IMR in the assessment of coronary microvascular dysfunction in classic TTS. Larger multicenter studies are warranted to confirm these findings.