Quantitative assessment of coronary stenosis by harmonic power Doppler with a simple pulsing sequence and vasodilator stress in patients

Trends in myocardial contrast echocardiography: parameteric versus volumetric imaging

It is now possible to perform myocardial contrast echocardiography at the bedside with an intravenous injection of commercially available contrast media. Although myocardial contrast echocardiography is a sensitive method for the detection of coronary stenosis and myocardial viability, its diagnosis has relied largely on the subjective interpretation of regional perfusion by experienced clinicians. Thus, quantification of myocardial contrast echocardiography data and displaying comprehensive images have been necessary for its routine application. In this review, new methods for quantifying or displaying myocardial contrast echocardiography parameters will be introduced: firstly, parametric imaging that displays the parameters of myocardial blood volume, blood flow velocity and myocardial blood flow separately; and secondly, color-coded maps of myocardial blood volume established from one myocardial contrast echocardiography image. These quantitative techniques can provide comprehensive and easy-to-understand images, although the quality of the baseline image remains a critical factor.

Clinical Application of Harmonic Power Doppler Imaging in the Assessment of Myocardial Perfusion by Contrast Echocardiography

Myocardial contrast echocardiography has moved from the research laboratory to clinical echocardiography. As with any emerging technology, background information and understanding the process of image acquisition will help to integrate the technology into everyday practice. Harmonic power Doppler imaging (HPDI) is a high-power, triggered imaging modality used to assess myocardial perfusion. Contrast agents used in echocardiography provide microvascular tracers that enable HPDI to accurately visualize myocardial blood flow. This article aims to provide direction in the clinical performance of myocardial contrast echocardiography by providing background in the theory and physics of HPDI and a guide to the technical acquisition of images and recognition of artifacts that arise during HPDI.

Noninvasive assessment of coronary vasodilation using magnetic resonance angiography

OBJECTIVES

The purpose of this study was to investigate the use of coronary magnetic resonance angiography (MRA) for assessing human epicardial coronary artery vasodilation.

BACKGROUND

Coronary vasodilation plays a vital role in the human coronary circulation. Previous studies of epicardial coronary vasodilation have used invasive coronary angiography. Coronary MRA may provide an alternative noninvasive method to directly assess changes in coronary size.

METHODS

Thirty-two subjects were studied: 12 patients (age 55 +/- 18 years) and 20 healthy subjects (age 34 +/- 4 years). High-resolution multi-slice spiral coronary MRA (in-plane resolution of 0.52 to 0.75 mm) was performed before and after sublingual nitroglycerin (NTG). Quantitative analysis of coronary vasodilation was performed on cross-sectional images of the right coronary artery (RCA). A time-course analysis of coronary vasodilation was performed in a subset of eight subjects for 30 min after NTG. Signal-to-noise ratio was also measured on the in-plane RCA images.

RESULTS

Coronary MRA demonstrated a 23% increase in cross-sectional area after NTG (16.9 +/- 7.8 mm2 to 20.8 +/- 8.9 mm2, p <0.0001), with significant vasodilation between 3 and 15 min after NTG on time-course analysis. The MRA measurements had low interobserver variability (< or =5%) and good correlation with X-ray angiography (r=0.98). The magnitude of vasodilation correlated with baseline cross-sectional area (r=0.52, p=0.03) and age (r=0.40, p=0.019). Post-NTG images also demonstrated a 31% improvement in coronary signal-to-noise ratio (p = 0.002).

CONCLUSIONS

Nitroglycerin-enhanced coronary MRA can noninvasively measure coronary artery vasodilation and is a promising noninvasive technique to study coronary vasomotor function.

Myocardial contrast echocardiography with a new calibration method can estimate myocardial viabilityin patients with myocardial infarction

OBJECTIVES

We have developed a novel calibration technique applicable for myocardial contrast echocardiography (MCE). We assessed the value of this technique in the recognition of myocardial infarction (MI) and its spatial extent, and we also performed a validation study in normal subjects.

BACKGROUND

The heterogeneity of contrast intensity (CI) among myocardial segments limits the clinical use of MCE.

METHODS

We performed MCE with a slow-bolus injection of Levovist and recorded end-systolic harmonic power Doppler images at intervals of four heart beats in 15 normal volunteers and 30 patients with MI. We divided the left ventricular (LV) wall into 12 segments and placed the region of interest in the subendocardial region in each segment and in the adjacent LV cavity. We measured calibrated CI (dB) by subtracting the cavity CI from myocardial CI.

RESULTS

The mean intersegmental difference in myocardial CI was 15.8 dB at baseline, whereas it was reduced to 6.3 dB after calibration (p < 0.01). Calibrated CI was higher in the kinetic segments than in the akinetic segments (-14.5 +/- 2.3 dB [range -18.7 to -9.9 dB] vs. -22.5 +/- 2.6 dB [-27.8 to -17.7 dB], p < 0.001), and -18.0 dB was the optimal cutoff point to discriminate these from each other. Color-coded mapping of calibrated CI may identify the spatial extent of persistently akinetic myocardium as areas of calibrated CI of <or=-18.0 dB.

CONCLUSIONS

This new calibration method reduces the intersegmental difference in CI in normal subjects. Calibrated CI provides an estimate of persistently akinetic myocardium in patients with MI, and its color-coded mapping is comprehensive and identifies the spatial extent of MI.