Microvascular Dysfunction from Coronary AngioCT? Vascular Remodeling Tiff-Off

Angina Patients studied invasively will show a significant proportion of non-obstructive coronary artery disease (ANOCA). From this group, nearly 50% might present coronary microvascular dysfunction (CMD), characterized by reduced coronary flow reserve (CFR < 2.5). Two different CMD phenotypes have been identified, according to minimal microvascular resistance assessment: patients with functional CMD (with resting elevated blood flow, Rµ hip ≤ 470 UW) and those with structural CMD (with reduced hyperemic flow, Rµ hip > 470).

Both resting and hyperemic CMD can be assessed by continuous thermodilution, by measuring flow (Q) and microvascular resistance (expressed in Woods-WU). Flow and resistance are closely related with myocardial mass (MM) and vascular volume (VV).

Coronary angiotomography (CTA) can be used to quantify MM, VV and V/M relation parameters. Based on this, Collet et al. characterized ANOCA patients by measuring microvascular resistance and vascular remodeling and MM patterns with CTA. 

This was a single center study carried out at the OLV Clinique in Aalst (Belgium), including angina patients with ANOCA (defined as FFR > 0.75). Patients with cardiac function deterioration, chronic kidney disease, concomitant valve disease and micro-cardiomyopathies were excluded. 

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CT data showed vessel specific MM measurements, plaque volume, VV, lumen volume (VL), atheroma percentage and V/M index.  For invasive measurement, PressureWire X devices were used and data were obtained with CoroFlow CV System software.  

Resting measurements were obtained using 3 ml saline injections. To assess hyperemia, 12 mg. intracoronary papaverine was administered, together with injections and a continuous saline infusion. Both resting and hyperemic absolute coronary flow data were registered (Qrest and Qhiper), mean transit time, microvascular resistance (Rµ, WU), CFR and microvascular resistance reserve (MRR). 

The study included 153 patients with ANOCA, 85 had normal CFR (control group), 22 presented structural CMD, and 46 functional CMD. 41% were women, and CMD was more frequent in older patients with hypertension and diabetes. There were no differences in FFR between the different phenotypes; however, CFR and MRR were lower in patients with structural CMD. These presented 40% lower Qhiper vs control and functional patients. 

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There was a strong correlation between lumen volume (LV) and myocardial mass (MM) (r = 0.70 [CI95%: 0.58-0.79]; P < 0.001). Epicardial VL was 40% lower in patients with structural CMD vs control and functional patients. Also, VL significantly correlated with minimal microvascular resistance (r = -0.59 [CI95%: -0.45 a -0.71]; P < 0.001). V/M relation was significantly reduced in patients with structural CMD, mainly because of volume. After regression and adjustment, only lumen volume was independently associated with microvascular resistance, establishing a 591 mm³ VL cut off value for structural CMD detection, with 75% sensitivity and 81% specificity.

Conclusions

In patients with ANOCA, it was observed through CTA that vascular remodeling correlates with the structural CMD phenotype, characterized by low coronary flow reserve and elevated minimal microvascular resistance. These findings highlight the role of CT in the detection of microvascular disease. 

Original Title: Vascular Remodeling in Coronary Microvascular Dysfunction. 

Reference: Collet C, Sakai K, Mizukami T, Ohashi H, Bouisset F, Caglioni S, van Hoe L, Gallinoro E, Bertolone DT, Pardaens S, Brouwers S, Storozhenko T, Seki R, Munhoz D, Tajima A, Buytaert D, Vanderheyden M, Wyffels E, Bartunek J, Sonck J, De Bruyne B. Vascular Remodeling in Coronary Microvascular Dysfunction. JACC Cardiovasc Imaging. 2024 Aug 30:S1936-878X(24)00308-5. doi: 10.1016/j.jcmg.2024.07.018. Epub ahead of print. PMID: 39269414.