Use of a new myocardial centroid for measurement of regional myocardial dysfunction by electron beam computed tomography: comparison with technetium-99m sestamibi infarct size quantification

Endocardial center motion for quantification of left ventricular discoordination in heart failure using cine MRI

OBJECTIVE

To compare a novel cardiovascular magnetic resonance technique for the assessment of left ventricular (LV) mechanical discoordination by characterizing the endocardial center motion (ECM) in short-axis cine MRI in healthy volunteers and heart failure patients with left bundle branch block (HF-LBBB).

APPROACH

To evaluate ECM analysis as mechanical discoordination measure, we retrospectively compared spatial and temporal features of the ECM between a group of healthy volunteers (n  =  14) and conduction defect patients (HF-LBBB, n  =  31). We tracked the center of the endocardial borders on short-axis view MRI cine loops during the cardiac cycle. From the ECM trajectory we calculated the overall traveled distance, the enclosed area, the eccentricity of the trajectory, and the maximum traveled distance. The ECM can be visualized in spatial coordinates as well as by its temporal behavior. We evaluated the classification performance of these measures for LBBB detection. We also quantified the coherence of the ECM on the longitudinal direction by considering the variability of the ECM measures between different short-axis slices.

MAIN RESULTS

Patients with LBBB showed significantly higher traveled distance (p  <  0.0001), enclosed area (p  <  0.002), eccentricity (p  <  0.02), and peak displacement (p  <  0.02) of the endocardial center. Patients with positive late gadolinium enhancement showed a higher variability of ECM measures across different slices (p  <  0.05).

SIGNIFICANCE

ECM analysis is feasible and it allows the assessment of left ventricular mechanical discoordination. Differences in ECM measures permit one to distinguish between LBBB and healthy volunteers.

Method to create regional mechanical dyssynchrony maps from short-axis cine steady-state free-precession images

PURPOSE

To develop a robust method to assess regional mechanical dyssynchrony from cine short-axis MR images. Cardiac resynchronization therapy (CRT) is an effective treatment for patients with heart failure and evidence of left-ventricular (LV) dyssynchrony. Patient response to CRT is greatest when the LV pacing lead is placed in the most dyssynchronous segment. Existing techniques for assessing regional dyssynchrony require difficult acquisition and/or postprocessing. Our goal was to develop a widely applicable and robust method to assess regional mechanical dyssynchrony.

MATERIALS AND METHODS

Using the endocardial boundary, radial displacement curves (RDCs) were generated throughout the LV. Cross-correlation was used to determine the delay time between each RDC and a patient-specific reference. Delay times were projected onto the American Heart Association 17-segment model creating a regional dyssynchrony map. Our method was tested in 10 normal individuals and 10 patients enrolled for CRT (QRS > 120 ms, NYHA III-IV, EF < 35%).

RESULTS

Delay times over the LV were 23.9 ± 33.8 ms and 93.1 ± 99.9 ms (P < 0.001) in normal subjects and patients, respectively. Interobserver reproducibility for segment averages was 6.8 ± 39.3 ms and there was 70% agreement in identifying the latest contracting segment.

CONCLUSION

We have developed a method that can reliably calculate regional delay times from cine steady-state free-precession (SSFP) images. Maps of regional dyssynchrony could be used to identify the latest-contracting segment to assist in CRT lead implantation.

Assessment of cardiac function by electron-beam computed tomography

The measurement of parameters relating to the assessment of cardiac function and morphology are critically important prognostic determinates in patients with known or suspected cardiac disease, such as coronary artery disease and myocardial infarction. Similarly, the measurement of indices, such as ejection fraction and myocardial mass, are key in assessing the efficacy of therapy in patients with valvular, coronary artery and intrinsic myocardial diseases. Electron-beam computed tomography has been proven to be a reliable and accurate modality for measuring a host of parameters relating to cardiac function. This article reviews the unique technologic design of the electron-beam computed tomography scanner and specifically addresses how this technology has enabled electron-beam computed tomography to become the gold standard for the quantification of cardiac function.

Current results and new developments of coronary angiography with use of contrast-enhanced computed tomography of the heart

Electron beam computed tomography (EBCT) is the reference standard for x-ray-based tomographic imaging of the heart because of its high temporal resolution, but it is available in only a few centers. Quantification of coronary calcium is the most widely recognized use of EBCT for cardiac imaging. This technique requires no contrast media and provides an accurate assessment of overall plaque burden in the coronary tree; however, it does not directly identify or localize coronary stenoses. Multislice spiral (helical) CT (MSCT) is a new technology that provides images of the beating heart in diagnostic quality under many circumstances and may facilitate the broader application of cardiac and coronary CT. Currently, for imaging of the heart, much more experience exists with EBCT than with MSCT. Contrast-enhanced CT coronary angiography (CTCA) can be done with EBCT or MSCT to obtain images of the major branches of the coronary tree and to define luminal narrowing. Studies at experienced centers performed with small numbers of patients show that sensitivity, specificity, and negative predictive value are good with CTCA in the assessment of obstructive coronary artery disease, but CTCA remains an investigational technique for these applications. Computed tomographic coronary angiography can be clinically useful for assessing coronary artery bypass graft patency and congenital coronary abnormalities.