Index of microcirculatory resistance in the assessment of coronary microvascular dysfunction in hypertrophic cardiomyopathy

Sílvia Aguiar Rosa; Miguel Mota Carmo; Luís Rocha Lopes; Eunice Oliveira; Boban Thomas; Luis Baquero; Rui Cruz Ferreira; António Fiarresga

doi:10.1016/j.repc.2021.07.013

Index of microcirculatory resistance in the assessment of coronary microvascular dysfunction in hypertrophic cardiomyopathy

Rev Port Cardiol. 2022 Sep;41(9):761-767. doi: 10.1016/j.repc.2021.07.013. Epub 2022 Jul 20.

[Article in English, Portuguese]

Authors

Sílvia Aguiar Rosa¹, Miguel Mota Carmo², Luís Rocha Lopes³, Eunice Oliveira⁴, Boban Thomas⁵, Luis Baquero⁵, Rui Cruz Ferreira⁴, António Fiarresga⁴

Affiliations

¹ Department of Cardiology, Hospital de Santa Marta, Lisbon, Portugal; Nova Medical School, Lisbon, Portugal; Heart Center, Hospital da Cruz Vermelha Portuguesa, Lisbon, Portugal. Electronic address: silviaguiarosa@gmail.com.
² Nova Medical School, Lisbon, Portugal.
³ Inherited Cardiac Disease Unit, Barts Heart Centre, St Bartholomew's Hospital, London, United Kingdom; Centre for Heart Muscle Disease, Institute of Cardiovascular Science, University College London, United Kingdom; Cardiovascular Centre, University of Lisbon, Portugal.
⁴ Department of Cardiology, Hospital de Santa Marta, Lisbon, Portugal.
⁵ Heart Center, Hospital da Cruz Vermelha Portuguesa, Lisbon, Portugal.

PMID: 36066271
DOI: 10.1016/j.repc.2021.07.013

Abstract

Introduction and objectives: Coronary microvascular dysfunction (CMD) is one of the most important pathophysiological features in hypertrophic cardiomyopathy (HCM). The index of microcirculatory resistance (IMR) is an invasive method to assess the coronary microcirculation. The aim was to assess CMD in patients with HCM by IMR.

Methods: Adult patients with HCM without epicardial coronary artery disease underwent cardiac catheterization for the assessment of CMD by IMR (normal cut-off value ≤22.0) and coronary flow reserve (CFR) (normal cut-off value ≥2). Cardiovascular magnetic resonance (CMR) was performed to assess the ischemic burden by perfusion imaging during regadenoson-induced hyperemia, and the extent of myocardial fibrosis was assessed by late gadolinium enhancement (LGE), native T1 mapping and extracellular volume (ECV).

Results: Fourteen patients were enrolled with a mean age of 62.8±6.2years, 8 (57.1%) males, of whom 9 (64.3%) had obstructive HCM. Using IMR, CMD was detected in 4 (29%) patients. Among four patients with an IMR>22.0, all had non-obstructive HCM and two had angina. CFR<2 was reported in eight patients (57%). Concordance between IMR and CFR (both normal or both abnormal) was verified in 6 patients (43%). Among four patients with IMR>22.0, perfusion defects were found in two of the three patients who underwent stress CMR. Increased ECV (>28%) was documented in two of the patients with IMR>22 and in three of the patients with IMR≤22.0. LGE was >15% in 2 of the patients with IMR>22 and in 4 with IMR≤22.0.

Conclusions: IMR assessment in HCM is feasible and safe. Patients with abnormal IMR seemed to have more significant tissue abnormalities on CMR.

Keywords: Cardiovascular magnetic resonance; Coronary flow reserve; Disfunção microvascular; Hypertrophic cardiomyopathy; Index of microcirculatory resistance; Indice de resistência microcirculatória; Ischemia; Isquemia; Microvascular dysfunction; Miocardiopatia hipertrófica; Reserva de fluxo coronário; Ressonância magnética cardiovascular.