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Angiography-Derived Versus Coronary Guidewire-Derived Index of Microcirculatory Resistance in Patients With Ischemia
Ethan Loftspring1, Peter Zhang2, William Beaty3
1Division of Cardiology, Department of Medicine, Rush Medical College, Chicago, Illinois.
Insights
The angiography-derived index of microcirculatory resistance (IMRangio) is not a reliable tool for diagnosing coronary microvascular dysfunction (CMD) in patients with ischemia with nonobstructive coronary arteries (INOCA). Current methods remain the standard for accurate CMD assessment.
Area of Science:
- Cardiology
- Vascular Medicine
- Diagnostic Imaging
Background:
- Coronary function testing (CFT) is recommended for diagnosing coronary microvascular dysfunction (CMD) in ischemia with nonobstructive coronary arteries (INOCA).
- Angiography-derived index of microcirculatory resistance (IMRangio) offers a potential simplified approach to CMD assessment.
- The validity of IMRangio compared to conventional index of microcirculatory resistance (IMR) in INOCA patients requires evaluation.
Purpose of the Study:
- To assess the validity of IMRangio against conventional IMR in patients with INOCA.
- To determine the correlation between IMRangio and IMR in this patient population.
- To evaluate the diagnostic performance of IMRangio for identifying CMD.
Main Methods:
- A single-center observational study enrolled 122 adults with INOCA undergoing invasive coronary angiography.
- Coronary function testing (CFT) with bolus thermodilution determined IMR and coronary flow reserve (CFR).
- IMRangio was calculated retrospectively and blinded to CFT results; CMD was defined by IMR ≥25 or CFR <2.5.
Main Results:
- IMRangio showed a poor correlation with IMR (r = 0.1; P = .14).
- IMRangio sensitivity and specificity for detecting CMD were 44% and 53%, respectively.
- Weak positive correlations were observed only under specific optimal cineangiography conditions.
Conclusions:
- IMRangio demonstrates poor correlation with IMR in patients with INOCA.
- The current IMRangio method appears unreliable for diagnosing CMD in this population.
- Conventional CFT remains essential for accurate CMD assessment in INOCA patients.
Background:
Coronary function testing (CFT) during invasive coronary angiography is guideline-recommended to identify coronary microvascular dysfunction (CMD) in patients with ischemia with nonobstructive coronary arteries (INOCA). Wire-free, angiography-derived index of microcirculatory resistance (IMRangio) measurements have been developed to simplify assessment for CMD. We assessed the validity of IMRangio compared with the conventional index of microcirculatory resistance (IMR) in a cohort of individuals with INOCA.
Methods:
This single-center observational study prospectively enrolled adults aged >18 years who were referred for clinically indicated invasive coronary angiography for the evaluation of chest discomfort or an anginal equivalent and had no coronary artery lesions with ≥50% stenosis. Participants underwent invasive CFT using bolus thermodilution techniques to determine IMR and coronary flow reserve (CFR) in the left anterior descending artery. IMRangio was calculated retrospectively, blinded to CFT results. CMD was defined by IMR ≥25 or CFR <2.5.
Results:
Among 122 enrolled participants with INOCA (median age 62 years, 77% women), the median IMR in the left anterior descending artery was 20 (13-27), CFR was 3.95 (2.5-4.7), and 54 participants (44%) had CMD. IMRangio did not correlate with IMR (r = 0.1; P = .14). Mean IMRangio was not different among patients with and without IMR ≥25 (P = .21). IMRangio ≥25 had a sensitivity of 44% and a specificity of 53% in identifying participants with CMD. In sensitivity analyses among participants with cineangiography at 10 to 15 frames per second (r = 0.37; P = .02) and limited to participants with both optimal angiographic view and frame rates ≥10 (r = 0.48; P = .03), we observed weak positive correlations between IMRangio and IMR.
Conclusions:
In patients with INOCA, correlations between IMRangio and IMR were poor. IMRangio appears unreliable for identifying CMD in patients with INOCA.
