Quantifying "normalized" regional left ventricular contractile function in ischemic coronary artery disease.

OBJECTIVE

When significant coronary lesions are identified by angiography, regional left ventricular (LV) contractile function often plays a role in determining candidacy for revascularization. To improve on current subjective and nonquantitative metrics of regional LV function, we tested a z-score "normalization" of regional strain information quantified from clinically acquired high-resolution LV geometric datasets.

METHODS

Test subjects (n = 120) underwent cardiac MRI with multiple 3-dimensional strain parameters calculated from tissue tag-plane displacement data. Sixty healthy volunteers contributed strain parameter data at each of 15,300 LV grid points, to form a normal human strain database. Point-specific database comparisons were made in 60 patients who had documented coronary artery disease (CAD), by angiography. Patient-specific, color-coded 3-dimensional LV maps of z-score-normalized contractile function were generated.

RESULTS

Blinded clinical review indicated that 55% (33 of 60) of the patients with CAD had significant regional contractile abnormalities by 1 of 3 "gold-standard" criteria: (1) Q waves on electrocardiography (ECG); (2) infarct on radionuclide single-photon emission computed tomography (SPECT); or (3) akinesia or dyskinesia on echocardiography. Consistency among all gold-standard metrics was found for only 19% (6 of 31) of patients with CAD who had ≥2 available metrics. Blinded MRI-based, multiparametric, strain z-score localization of contractile abnormalities was accurate in 89% (ECG), 97% (SPECT), and 95% (echocardiography).

CONCLUSIONS

Nonsubjective normalization of regional LV contractile function by z-score calculation from a normal human strain database can localize and quantitatively display regional wall motion abnormalities in patients with CAD. This high-resolution localization of regional wall motion abnormalities may help improve the accuracy of therapeutic intervention in patients who have CAD.