SPC365

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

Session: CO 21 - Miocardiopatias
Speaker: Silvia Aguiar

Congress: CPC 2021
Topic: F. Valvular, Myocardial, Pericardial, Pulmonary, Congenital Heart Disease
Theme: 17. Myocardial Disease
Subtheme: 17.3 Myocardial Disease – Diagnostic Methods
Session Type: Comunicações Orais
FP Number: ---
Authors: Sílvia Aguiar Rosa; Miguel Mota Carmo; Luís Rocha Lopes; Eunice Oliveira; Boban Thomas; Luis Baquero; Rui Cruz Ferreira; António Fiarresga

<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">Introduction: Coronary microvascular dysfunction (CMD) constitutes one of the most important pathophysiological features in hypertrophic cardiomyopathy (HCM) and may lead to recurrent ischemia, cardiomyocyte death and myocardial fibrosis. The index of microcirculatory resistance (IMR) constitutes an invasive method to evaluate the coronary microcirculation.</span></span></p>

<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">Objectives: a) to evaluate CMD in HCM by IMR and coronary flow reserve (CFR), complemented with the detection of perfusion defects by stress cardiovascular magnetic resonance (CMR); b) to investigate the relationship between CMD and myocardial fibrosis.</span></span></p>

<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">Methods: Prospective study. HCM adult patients without epicardial coronary artery disease underwent cardiac catheterization for the assessment of CMD by IMR (normal cut off value &le;22.0) and coronary flow reserve (CFR)(normal cut off value &ge;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<strong> </strong>assessed by late gadolinium enhancement (LGE), native T1 mapping and extracellular volume (ECV). </span></span></p>

<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">Results: Fourteen patients with a mean age of 62.8&plusmn;6.2years, 8 (57.1%) males, 9 (64.3%)<strong> </strong>of whom<strong> </strong>had obstructive HCM. </span></span></p>

<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">In the overall population, Pd was 68.8&plusmn;18.8mmHg, T<sub>mnRest</sub> 0.61&plusmn;0.25s, T<sub>mnHyper&nbsp;</sub>0.32&plusmn;0.10s, CFR 1.93&plusmn;0.69 and IMR was 21.4&plusmn;6.3U.</span></span></p>

<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">Among the 4 patients with an IMR &gt;22.0, all had non-obstructive HCM and 2 had angina.&nbsp; </span></span><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">Among the 10 patients with an IMR &le;22, 1 had non-obstructive HCM, 6 patients complained of angina.&nbsp;</span></span><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">CFR&lt;2 was reported in 8 patients (57%). Concordance between IMR and CFR (both normal or both abnormal) was verified in 6 patients (43%). </span></span></p>

<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">All patients except one, due to claustrophobia, underwent CMR. Stress CMR demonstrated perfusion defects in 12 out of 13 patients (92%), with an ischemic burden between 3 and 54% of LV.&nbsp; </span></span><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">Among the 4 patients with IMR&gt;22.0, perfusion defects were found in 2 of the 3 patients who underwent stress CMR.&nbsp;</span></span></p>

<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">In the overall sample, ECV was increased in 5 patients (36%) (normal ECV values 25&plusmn;3%).&nbsp;</span></span><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">Increased ECV (&gt;28%) was documented in 2 of the patients with IMR&gt;22 patients and in 3 of the patients with IMR&le;22.0.</span></span></p>

<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">LGE was found in all patients with a range between 3.4 to 39.8% of LV mass.&nbsp;</span></span><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">LGE was &gt;15% in 2 of the patients with IMR&gt;22 and in 4 with IMR&le;22.0.</span></span></p>

<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">Conclusion: IMR detected CMD in a significant proportion of HCM patients. IMR has the potential to become a useful tool for microcirculation assessment in HCM patients.</span></span></p>