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      Quantification of resting myocardial blood flow velocity in normal humans using real-time contrast echocardiography. A feasibility study

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          Abstract

          Background

          Real-time myocardial contrast echocardiography (MCE) is a novel method for assessing myocardial perfusion. The aim of this study was to evaluate the feasibility of a very low-power real-time MCE for quantification of regional resting myocardial blood flow (MBF) velocity in normal human myocardium.

          Methods

          Twenty study subjects with normal left ventricular (LV) wall motion and normal coronary arteries, underwent low-power real-time MCE based on color-coded pulse inversion Doppler. Standard apical LV views were acquired during constant IV. infusion of SonoVue ®. Following transient microbubble destruction, the contrast replenishment rate (β), reflecting MBF velocity, was derived by plotting signal intensity vs. time and fitting data to the exponential function; y (t) =A (1-e -β(t-t0)) + C.

          Results

          Quantification was feasible in 82%, 49% and 63% of four-chamber, two-chamber and apical long-axis view segments, respectively. The LAD (left anterior descending artery) and RCA (right coronary artery) territories could potentially be evaluated in most, but contrast detection in the LCx (left circumflex artery) bed was poor. Depending on localisation and which frames to be analysed, mean values of were 0.21–0.69 s -1, with higher values in medial than lateral, and in basal compared to apical regions of scan plane (p = 0.03 and p < 0.01). Higher β-values were obtained from end-diastole than end-systole (p < 0.001), values from all-frames analysis lying between.

          Conclusion

          Low-power real-time MCE did have the potential to give contrast enhancement for quantification of resting regional MBF velocity. However, the technique is difficult and subjected to several limitations. Significant variability in β suggests that this parameter is best suited for with-in patient changes, comparing values of stress studies to baseline.

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          Most cited references28

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          Recommendations for quantitation of the left ventricle by two-dimensional echocardiography. American Society of Echocardiography Committee on Standards, Subcommittee on Quantitation of Two-Dimensional Echocardiograms.

          We have presented recommendations for the optimum acquisition of quantitative two-dimensional data in the current echocardiographic environment. It is likely that advances in imaging may enhance or supplement these approaches. For example, three-dimensional reconstruction methods may greatly augment the accuracy of volume determination if they become more efficient. The development of three-dimensional methods will depend in turn on vastly improved transthoracic resolution similar to that now obtainable by transesophageal echocardiography. Better resolution will also make the use of more direct methods of measuring myocardial mass practical. For example, if the epicardium were well resolved in the long-axis apical views, the myocardial shell volume could be measured directly by the biplane method of discs rather than extrapolating myocardial thickness from a single short-axis view. At present, it is our opinion that current technology justifies the clinical use of the quantitative two-dimensional methods described in this article. When technically feasible, and if resources permit, we recommend the routine reporting of left ventricular ejection fraction, diastolic volume, mass, and wall motion score.
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            Noninvasive quantification of coronary blood flow reserve in humans using myocardial contrast echocardiography.

            We hypothesized that coronary blood flow (CBF) reserve could be quantified noninvasively in humans using myocardial contrast echocardiography (MCE). Eleven patients with normal epicardial coronary arteries (group I) and 19 with single-vessel coronary stenosis (group II) underwent quantitative coronary angiography, MCE, and CBF velocity measurements at rest and during intravenous adenosine infusion. In group I patients, MCE-derived myocardial blood flow (MBF) velocity reserve (2.4+/-0.08) was similar to CBF velocity reserve using a Doppler flow wire (2.4+/-1.1). Patients with a single risk factor had a significantly higher MBF reserve (3.0+/-0.89) than those with >/=2 risk factors (1.7+/-0.22). In group II patients, significant differences were found in MBF velocity reserve in patients with mild ( 75%) stenoses (2.2+/-0.40, 1.6+/-0.65, and 0.55+/-0.19, respectively; P=0.005). A linear relation was found between flow velocity reserve determined using the 2 methods (r=0.76, P<0.001), and a curvilinear relation was noted between the percent coronary stenosis measured using quantitative coronary angiography and velocity reserve using both methods. CBF reserve can be measured in humans using MCE. This method may allow the noninvasive assessment of coronary stenosis severity and the detection of microvascular dysfunction.
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              Recommendations for quantitation of the left ventricle by two dimensional echocardiography. American Society of Echocardiography Committee on Standards, Subcommittee on Quantitation of Two-Dimensional Echocardiograms

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                Author and article information

                Journal
                Cardiovasc Ultrasound
                Cardiovascular Ultrasound
                BioMed Central (London )
                1476-7120
                2005
                16 June 2005
                : 3
                : 16
                Affiliations
                [1 ]Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway
                [2 ]GE Healthcare Technologies, Ultrasound R&D, Trondheim, Norway
                Article
                1476-7120-3-16
                10.1186/1476-7120-3-16
                1184091
                15958173
                b486b54e-32e8-481a-aee2-5345750939ed
                Copyright © 2005 Malm et al; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 30 April 2005
                : 16 June 2005
                Categories
                Research

                Cardiovascular Medicine
                myocardial perfusion,real-time imaging,contrast echocardiography,contrast replenishment rate

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