Usefulness of three-dimensional transesophageal echocardiographic imaging for evaluating narrowing in the coronary arteries

Evaluation of coronary arterial stenoses using 2D magnetic resonance coronary angiography

This study investigated the usefulness and limitations of magnetic resonance coronary angiography (MRCA). MRCA was performed with an electrocardiographically gated gradient echo sequence with k-space segmentation. Coronary angiography (CAG) was performed using a conventional system. We had three protocols. In protocol one, 160 consecutive patients (279 coronary arteries) who underwent initial CAG for diagnosing coronary artery disease were enrolled. Out of the 279 coronary arteries, 235 arteries (84.2%) were visualised with an image quality suitable for further analysis. In these 235 arteries, the validity for diagnosing over 75% arterial stenosis was 98%, and sensitivity and specificity was 79%. In protocol two, 48 stenoses were evaluated for restenosis after balloon angioplasty. The validity for diagnosing restenosis by MRCA was 93% in sensitivity and 33% in specificity. In protocol three, comprising 18 coronary arteries with total obstruction, the presence of collaterals was evaluated. The development of collateral circulation improved MRCA findings in the distal portion of obstructed coronary arteries. We conclude that MRCA provides useful information with acceptable sensitivity and specificity before balloon angioplasty. However, MRCA has a tendency to over-estimate restenosis after balloon angioplasty.

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.

In vitro simulation and quantification of temporal jitter artifacts in ECG-gated dynamic three-dimensional echocardiography

The image quality of dynamic 3-D echocardiography is limited by temporal jitter artifacts that result from the asynchronous acquisition of video frames with the cardiac cycle. This paper analyzes the source and extent of these artifacts using in vitro studies. Dynamic 3-D images of a myocardial motion phantom were reconstructed and analyzed for eight cardiac motion patterns. The extent of temporal jitter artifacts was quantified, first, from the images by computing temporal jitter maps and, second, predicted from the motion waveforms. Temporal jitter appeared as a pattern of streak artifacts converging at the axis of rotation of the imaging plane, for the rotational scanning approach used in our study. The results of the experimental analysis techniques were compared with the waveform analysis using linear regression analysis. The least squares line showed good correlation between the data (r > 0.9) and its deviation from the line of identity was calculated to be <9%.

Three-dimensional transesophageal echocardiography (TEE) and other future directions

As faster imaging systems enter the market, three-dimensional echocardiography is gearing up to become a useful tool in assisting the clinician to image the heart in many innovative projections. What started out as a novel idea of displaying a three-dimensional anatomic picture of the heart now provides a multitude of views of the heart and its structures. Information gained from anatomic and dynamic data has helped clinicians and surgeons in making clinical decisions. In the future, this imaging modality may become a routine imaging modality for assessing cardiac pathology and may serve to increase understanding of the dynamics of the heart.

Usefulness of topography of coronary calcium by electron-beam computed tomography in predicting the natural history of coronary atherosclerosis

Electron-beam computed tomography (EBCT) allows for accurate noninvasive detection and quantification of coronary calcium that is representative of underlying atherosclerotic disease. The present study quantitatively analyzes the topography and establishes the natural history of coronary calcium in patients with variable degrees of coronary atherosclerosis. EBCT was performed in 330 consecutive patients aged 56 +/- 12 years (70% men) with recent (<3 months) onset of signs or symptoms of coronary artery disease (CAD) or who were evaluated because of a presumed high risk. Total calcium scores, computed by the Agatston method, were positive in 269 patients (82%) (mean age 58 +/- 11 years, 73% men). These patients were classified into 4 groups, with total calcium scores ranging between 1 and 30, >30 and 100, >100 and 400, and >400, respectively. The presence and amount of calcium was additionally assessed in 10 major segments of the coronary arterial tree, including the major coronary arteries. Of the 72 patients with calcium of only 1 of the major coronary arteries, the left anterior descending coronary artery was involved in 39 patients (54%) and the right coronary artery in 18 patients (25%). Left main stem calcium was observed in only 10 of 139 patients (7%) with 1- or 2-vessel calcium and in 17 of 77 patients (23%) with 3-vessel calcium. Calcium was consistent most frequently in the proximal left anterior descending coronary artery, followed by the proximal left circumflex and right coronary artery segments. A significant decrease of frequency and amount of calcium from the proximal to distal segments was observed in the left coronary system but not in the right coronary artery, where the distribution was more even. With increasing total calcium scores, segmental scores in the more distal segments were enhanced, but the increase was most pronounced in the proximal segments and particularly in the proximal left anterior descending coronary artery. EBCT-derived coronary calcium shows an axial distribution that appears comparable to that of atherosclerotic lesions observed in pathologic and angiographic studies, highlighting the potential role of EBCT for studying the natural history of CAD.