Magnetocardiography as a Noninvasive Diagnostic Strategy for Suspected Coronary Microvascular Dysfunction.
MCG appears to correlate significantly better with CFR measured via the Doppler guidewire than it does with CFR measured via the thermodilution method, consistent with data demonstrating differences between these invasive CFR methods.
Authors
Namrita Ashokprabhu1,2, Khaled Ziada, MD3, Edouard Daher, MD4, Leslie Cho, MD3, ChristianW. Schmidt, MS2, Yulith Roca, MD1,2, Cassady Palmer1,2, Sukhleen Kaur1,2,Timothy D. Henry,MD2,Carl J. Pepine, MD5, and Odayme Quesada, MD1,2,6
1Women’s Heart Center, The Christ Hospital Heart and Vascular Institute, Cincinnati, OH, USA; 2The Carl and Edyth Lindner Center for Research and Education at The Christ Hospital, Cincinnati,OH, USA; 3Cleveland Clinic, Cleveland, OH; 4Ascension St.John, Detroit, MI; 5University of Florida, Gainesville, FL; 6Department of Internal Medicine, University of Cincinnati, Cincinnati, OH
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Background
- Coronary microvascular dysfunction (CMD) is associated with a nearly 4-fold increase in mortality.
- Current diagnostic modalities for CMD are limited by access, cost, and exposure of ionizing radiation.
- Magnetocardiography (MCG) is a rest-based scan that measures weak magnetic fields generated by natural cardiac ionic currents.
Purpose
Investigate MCG’s ability to detect CMD in patients with ischemia and no obstructive coronary artery disease (ANOCA).
- Observational, prospective study of ANOCA patients who underwent invasive coronary flow reserve (CFR) assessment for diagnosis of CMD and MCG scans.
- CMD was defined as an invasive CFR < 2 by Doppler wire or CFR < 2.5 by thermodilution assessment.
Feature Explanation
ST Island
Monopolar field map patterns in the ST segment
RT Angle
A significant angular difference between the orientations of the R peak and T wave magnetic field maps
ST Dynamics
Correlated collective variation of channels in the ST segment waveform
ST Elevation
Excess electromagnetic energy in the ST segment
Case 1
A 52-year-old woman with invasive CFR measure of 4.3 (normal) and 38 days later received an MCG scan with no abnormal findings (results shown below).
Case 2
A 55-year-old woman with invasive CFR measure of 1.4 (consistent with CMD) and 16 days later received an MCG scan with multiple abnormal findings, including: ST island and excessive RT angle (results shown below).
MCG had a sensitivity of 65% and specificity of 64% for the detection of CMD using gold standard invasive CFR as reference.
In the subset of patients with Doppler measurements, the sensitivity and specificity of MCG increased to 75% and 76%, respectively.
MCG had a positive predictive value of 47% and a negative predictive value of 79%.
The positive predictive value improved to 65% when reviewing only patients with Doppler measurements, with negative predictive value remaining high at 84%.
The area under the ROC curve (AUC-ROC) for this method was 0.64.
For patients with Doppler measurements, the AUC-ROC increased to 0.74.
54 ± 12.3
61 ± 11.5
81.1%
92.3%
9.4%
11.5%
90.6%
88.5%
1.9%
3.8%
96.3%
96.2%
31.6
31.2
13.2%
15.4%
64.2%
84.6%
86.8%
88.5%
34.0%
23.1%
37.7%
57.7%
47.2%
76.9%
58.5%
73.1%
75.5%
80.7%
66.0%
80.7%
71.7%
92.3%
35.8%
65.4%
35.8%
23.1%
64.2%
76.9%
3.37%
1.57%
32.0
23.0
7.5%
38.5%
- MCG performance in this first of its kind study demonstrates good efficacy at detecting CMD in ANOCA patients.
- These findings (AUC-ROC = 0.64-0.74) compare favorably to results published on stress echocardiography (AUC-ROC = 0.5) and cardiac magnetic resonance imaging (AUC-ROC = 0.6-0.8).
- MCG appears to correlate significantly better with CFR measured via the Doppler guidewire than it does with CFR measured via the thermodilution method, consistent with data demonstrating differences between these invasive CFR methods.
- The MICRO trial provides novel proof-of-concept demonstrating the potential for MCG to serve as a non-invasive imaging tool for the diagnosis of CMD in ANOCA patients that warrants further investigation.