Background
Intravenous adenosine is a well-established method for inducing stable myocardial hyperemia, essential for testing coronary microvascular function. Conversely, iodinated radiographic contrast media provide a transient and submaximal hyperemia. This study examines the feasibility, diagnostic efficacy, and potential cost-effectiveness of newly developed contrast-derived indices related to microvascular function in the coronary arteries.
Methods
We assessed three key parameters: coronary flow reserve (CFR), index of microvascular resistance (IMR), and microvascular resistance reserve (MRR) using a diagnostic guidewire. The protocol involved conducting intracoronary bolus thermodilution injections at rest, immediately after administering an 8-mL bolus of iohexol, then repeating this process with a second 8-mL bolus, and during an intravenous adenosine infusion. We performed receiver operating characteristic (ROC) analyses to evaluate the ability of the contrast-derived indices (CFR, IMR, and MRR) to detect abnormal adenosine-derived indices, defined as CFR < 2.0, IMR ≥ 25, and MRR < 2.1.
Results
The study evaluated 106 coronary arteries from 93 patients (median age 63 years; 62% female; 13% diabetic). Notably, 88% of the assessments were conducted in the left anterior descending artery. The median CFR registered at 0.88, with an interquartile range of 0.85 to 0.92. Our results indicated that a contrast-derived CFR 47 demonstrated an AUC of 0.82, while the contrast-derived MRR < 1.9 also yielded an AUC of 0.82, enhancing the prediction accuracy for their respective adenosine-derived counterpart indices. Importantly, we observed strong correlations during repeatability testing following the second contrast bolus. The hybrid approach utilized showed a significant reduction in adenosine use by 40%, translating to a savings of $30,800 (USA) or £8,000 (UK) per 1,000 vessels assessed.
Conclusions
In conclusion, the newly defined contrast-derived indices exhibit high specificity and negative predictive value, allowing for swift exclusion of microvascular dysfunctions. This methodology proves feasible, clinically beneficial, and cost-saving when compared to conventional adenosine testing, reinforcing its integration into clinical practice.
Registration
For further details, this study is registered at ClinicalTrials.gov under the unique identifier NCT04674449.
Reference
Ang DTY, Collison DG, McGeoch RJ, Carrick D, Sykes RA, Bradley C, Kamdar AL, Jong A, Brogan RA, MacDougall DA, McCartney PJ, Rocchiccioli JP, Apps AP, Murphy CA, Robertson KE, Shaukat A, Ghattas A, Joshi FR, Sood A, Good RIS, O’Rourke B, Eteiba H, Lindsay MM, McConnachie A, Berry C. Novel Contrast-Derived Indices of Coronary Microvascular Function: Potential Clinical and Cost Benefits. Circ Cardiovasc Interv. 2025 Jun;18(6):e015058. doi: 10.1161/CIRCINTERVENTIONS.124.015058. Epub 2025 May 1. PMID: 40308206.
