© 2004 by European Society of Cardiology
Copyright © 2003, The European Society of Cardiology
Myocardial contrast echocardiography demonstrates myocardial hypoperfusion in the LAD territory in patients with acute chest pain at rest—a prospective study using power Doppler harmonic imaging with intravenous bolus application
aDepartment of Cardiology-Angiology, University of Leipzig, Johannisallee 32, 04103 Leipzig, Germany
bJohn Radcliffe Hospital, Department of Cardiology, University of Oxford, Oxford, UK
Received 21 March 2003; received in revised form 16 June 2003; accepted after revision 17 June 2003.
* Corresponding author. Tel.: +49-341-97-12650; fax: +49-341-97-12659. hagea{at}medizin.uni-leipzig.de
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Abstract |
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 Top Abstract 1 Introduction2 Methods3 Results4 Discussion5 Limitations of the...6 ConclusionReferences |
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Aims: Using a previously published algorithm we hypothesize that myocardial contrast echocardiography (MCE) with power Doppler harmonic imaging (PDHI) is able to detect regional hypoperfusion within the territory of the left anterior descending artery (LAD) using intravenous (i.v.) injection of contrast in patients (pts) with coronary syndrome at rest.
Methods and results: Forty-seven consecutive patients (pts) were prospectively evaluated using a standardized i.v. bolus application of OPTISON. MCE data were acquired within 2 h before angiography. Cut-off Doppler intensity (DI)-values determined in the apical, mid, and basal septum were distinguished between normal and hypoperfused myocardium (e.g. 23.5 and 22.5 dB for maximum DI of the apical or mid-septum triggering on every third heart cycle). Seventeen of 42 pts were classified as normal and the remaining 25 pts as pathologic (10 of these 25 pts had elevated troponines). Angiography detected open vessels or TIMI-III-flow in 15 pts of the normal MCE group, significant stenosis (>70%) or reduced TIMI-flow in 22 pts of the pathologic MCE group. The highest sensitivities (83–92%) were found in the apical septum.
Conclusion: Assessment of the myocardial perfusion deficits in the LAD territory of pts with acute coronary syndrome is feasible with MCE with PDHI using an i.v. bolus protocol.
Keywords: power Doppler harmonic imaging; myocardial contrast echocardiography; bolus application; prospective study
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1 Introduction |
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TopAbstract1 Introduction2 Methods3 Results4 Discussion5 Limitations of the...6 ConclusionReferences |
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The calculation of a replenishment curve during continuous infusion of contrast agent seems to be an attractive algorithm for quantitative analysis of regional myocardial perfusion by myocardial contrast echocardiography (MCE).1–7 The microbubble replenishment during the steady state of a contrast infusion is determined after a short-term ultrasound flush by real-time data acquisition using low mechanical index techniques or by triggered data acquisition at different trigger intervals using high mechanical index techniques like power Doppler harmonic imaging (PDHI). This approach is thought to replace the intravenous (i.v.) bolus application, which has been criticized because of several methodological limitations. MCE during continuous infusion is suitable for quantitative analysis of perfusion in experimental and clinical settings.6–8 Continuous infusion of contrast, however, is less convenient than bolus application in clinical practice. Therefore, for clinical use the i.v. bolus application using MCE with PDHI is still an attractive modality for analysis of regional myocardial perfusion.9–14
In a smaller previous study we could show that the up- and down-slope of Doppler intensity (DI) versus time plots an i.v. bolus protocol of echo contrast could be used to identify patients (pts) with acute myocardial ischemia in the territory of the left anterior descending (LAD) artery.13 The present prospective study was designed to test this approach in a controlled trial involving consecutive pts. We hypothesize that MCE with PDHI is able to detect regional ischemia within the territory of the LAD using i.v. injection of contrast in pts with coronary syndrome at rest.
Figure 1 shows a scheme of the regional DI versus time plots of normal and hypoperfused myocardium after an i.v. bolus injection of microbubbles.
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2 Methods |
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TopAbstract1 Introduction2 Methods3 Results4 Discussion5 Limitations of the...6 ConclusionReferences |
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2.1 Characteristics of the patients
Within a time period of three months all pts referred to the emergency room with acute coronary syndrome who were scheduled for acute coronary angiography by clinical reasons were included in the trial. If the pts had clear evidence of transmural lateral, inferior or posterior infarction, they were excluded. Ordinary two-dimensional (2D) echocardiography and Doppler echocardiography documented normal or slightly reduced global left ventricular function in all pts of the present study. Like in the previous retrospective studies13,14 heart rate, ejection fraction and cardiac output (CO) were measured by 2D and pulsed Doppler echocardiography. If CO was less than 4.5 l min–1, pts were excluded from the study because the width of the bolus curve is dependent upon CO. MCE measurements with PDHI at rest as well as coronary angiography were performed in 47 symptomatic consecutive pts. Five of 47 pts were excluded because of poor image quality due to persistent wall motion artefacts within the septum and due to high acoustic impedance of the chest wall. All pts of this study underwent coronary angiography because of acute thoracic chest pain or signs of acute myocardial ischemia documented by ST elevation or elevated troponines. Exclusion criteria were old transmural myocardial infarctions of the septum. Contrast was given as a bolus injection of 0.4 ml OPTISON after information and consent of the pts. Ethical approval of the local committee was obtained for the present study.
2.2 Coronary angiography
In all pts coronary angiography was performed within 2 h after MCE. Coronary arteries were assessed by biplane recordings using a Poly Diagnostic C with an Optimus M2000 generator (Phillips, Einthoven, The Netherlands). Quantification of stenosis was performed by quantitative contour analysis with INTURIS CIVP (Phillips, Einthoven, The Netherlands). Stenoses were defined as significant when narrowing was detected more than 70% of pre-stenotic diameter. In addition, low flow conditions were also assumed if reduced thrombolysis in myocardial infarction trial (TIMI)-flow in the LAD territory was detected.
2.3 Myocardial contrast echocardiography and echo contrast agent
MCE was performed at rest using i.v. bolus application of OPTISON (Amersham Health, Buckinghamshire, United Kingdom). A bolus of 0.4 ml OPTISON was intravenously injected into a forearm vein followed by a rapid flush of 5 ml 0.9% saline solution.
2.4 Study protocol
Two repetitive i.v. boli of OPTISON were administrated in each patient. The apical four-chamber view was chosen for perfusion analysis of the interventricular septum (LAD territory). Images were acquired for 90 s using trigger intervals of every (1:1) or every third heart beat (3:1) to analyze reproducibility of the PDHI measurements and feasibility of triggered imaging with different trigger intervals in clinical practice. The ECG trigger was gated to end systole (133–233 ms after the R-wave). To avoid or minimize wall motion artefacts prior to MCE, system parameters and trigger were carefully adjusted to optimize scanning of the cineloop.
2.5 Imaging modalities
The PDHI investigations were performed with a System Five Performance Ultrasound System (GE Vingmed Ultrasound AS, Horten, Norway). Imaging was acquired in continuous second harmonic (octave) mode for conventional diagnostics, in the intermittent coded harmonic angiomode for perfusion imaging with a standard phased array transducer which transmits ultrasound at a mean frequency of 1.5 MHz and receives it at 3.0 MHz. Ultrasound pulses were gated to end systole once every or every third cardiac cycle. The transmission power was set at maximum power. Mechanical index was 1.4. The transmit focus was set between 6 and 10 cm. A maximum dynamic range of 60 dB was used. Pulse repetition frequency was 3000 Hz. Gain compensations were optimized before the injection of echo contrast agent. The settings of the ultrasound system during the PDHI measurements were as follows: compression 10 (according to the scale of the SystemFive); dynamic range 6 (according to the scale of the SystemFive); power –2 dB, gain –29 dB; pulse repetition frequency 3.00 kHz; frequency 1.5 MHz; sample volume 1.9 mm; low velocity reject 32.5 cm/s; color gain –18 dB. The data were digitally stored as cineloops and transferred after completion of the investigation to a standard Macintosh personal computer.
2.6 Qualitative analysis
Visual grading was performed using the following criteria: perfusion defect was defined as a non-opacified myocardium when there was full LV-opacification. In addition, patchy perfusion pattern was also diagnosed as abnormal when it was found at peak LV-opacification and within the first 20 s after peak maximum DI. Accordingly normal perfusion was complete and homogeneous opacification in each segment of the interventricular septum.
2.7 Quantitative analysis
Quantitative analysis of the data was performed using the EchoPac 6.2b.134 software (GE Vingmed Ultrasound AS, Horten, Norway). After storage of the cineloops myocardial regions of interest (ROI) with a size of 3x3 to 7x7 pixels were defined. For illustration of the MCE data, the traces of each ROI were shown in a logarithmic scale with DI of the acoustic power in dB on the y-axis and time in seconds on the x-axis; in addition, the colored M-modes right-angled to the scanning axis. Analysis of the PDHI data was performed by two independent investigators experienced with PDHI and MCE as well as with the EchoPac 6.2b.134 software. The following parameters were numerically evaluated: the peak maximum DI determined in the apical (DImax1a; DImax3a), mid (DImax1m; DImax3m), and basal septal myocardium (DImax1b; DImax3b) during triggering on every cardiac cycle (1) as well as on every third cardiac cycle (3); the DI determined in the apical (DIT10,T201a; DIT10,T203a), mid (DIT10,T201m; DIT10,T203m), and basal septal myocardium (DIT10,T201b; DIT10,T203b) during triggering on every (1) cardiac cycle and on every third (3) cardiac cycle 10 and 20 s after peak maximum DI. For each region of interest a cut-off value to distinguish between normal and hypoperfused areas was calculated by previous retrospective data analysis. According to these values the sensitivity and specificity as well as the odds ratio are given. For illustration the DI-curves are smoothed in the figures by calculation of mean values of three consecutive DI-values for each measurement. The septal opacification was additionally illustrated by colored M-modes.
2.8 Statistical analysis
Numerical data are presented as mean values ± standard deviation. F-test was performed to test the presence of normal distribution of the data and the comparability of the variances. Differences between the normal perfused and hypoperfused LAD territory were evaluated for all parameters using the Wilcoxon-W-test and Mann–Whitney-U-test for independent samples. Differences were considered significant at P-levels <0.05, 0.1, and 0.001. Correlations between original data were performed using logistic regression with Spearman's rank and Pearson's R-test. Logistic regression analysis and model Chi-square test had been performed to calculate cut-off values for clinical relevant PDHI parameters of regional myocardial hypoperfusion. Cut-off values were given at significance P<0.05 at highest value for –2 log likelihood.
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3 Results |
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TopAbstract1 Introduction2 Methods3 Results4 Discussion5 Limitations of the...6 ConclusionReferences |
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Calcifications due to coronary artery disease were present in all pts. Significant stenoses of the LAD were detected in 22 pts by angiography. In two additional pts low flow conditions in the LAD territory were observed presumably due to no reflow phenomenon after spontaneous lysis. Ten pts of 24 pts with low flow conditions documented by angiography had positive troponine levels; ST elevation was observed in eight pts. The 2D echocardiography and tissue velocity imaging documented akinesis of the LAD territory in six pts (all with elevated troponines levels); hypokinesis in 14 pts (four with elevated troponines levels), and normokinesis in 22 pts. In eight of the 22 pts with LAD stenosis additional stenosis of the circumflex artery or the right coronary artery were detected.
Eighteen of the 42 pts showed open epicardial arteries of the LAD territory and TIMI-III-flow. However, in 11 of these pts significant stenosis of the right coronary artery or the circumflex branch was found. In five of these pts troponin was positive, four pts had pathological ECG-recordings of the inferior and posterior regions.
Using qualitative visual analysis of the MCE data only 12 of 24 pts with angiographically defined hypoperfusion of the LAD territory were found to have a pathologic pattern of regional myocardial perfusion. Quantitative analysis showed DI patterns of septal hypoperfusion in 25 pts (in these 25 pts all 12 were detected as pathologic by visual analysis), DI patterns of normal septal perfusion in 17 pts. Twenty-two of 25 pts with low flow conditions detected by angiography had an abnormal MCE. The three additional pts, however, had significant stenoses of the right coronary artery. In 15 of 18 pts with open LAD MCE was normal; two pts with normal MCE data showed significant stenosis of the LAD. Table 1 shows the match and mismatch of the data determined by MCE and angiography.
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The variability of the DI-parameters DImax,T10,T201a,m,b; DImax,T10,T203a,m,b calculated by the two different investigators was in the range of 1–2 dB. Thus, the analysis of MCE measurements was well reproducible. The same pts were detected as normal and abnormal by the two investigators using the described algorithms.
Table 2 shows the results of the regional DI evaluation. The maximum DI value was not always suitable to distinguish between normal and hypoperfused areas mostly due to blooming. The early DI wash-out seems to be the best interval for detection of pathologic results. Ten to 20 seconds after maximum DI the parameter DI shows significant difference between the normal and hypoperfused regions in all apical and distal regions of the interventricular septum. Even the basal parts of the septum are often evaluable despite tissue attenuation. The sensitivities of the DIT10 and DIT20 cut-off values to detect regional hypoperfusion were 92 and 78% in the apical septum, 83 and 70% in the mid-septum, and 74 and 83% in the basal septum. The corresponding specificities were 61 and 83%, 67 and 67%, and 67 and 56%, respectively. As shown in Table 2 as well as in Figures 2 and 3
triggering on every as well as every third heart cycle produces a high reproducibility of the shape of the DI traces. Triggering on every heart cycle, however, seems to be more feasible in clinical practice and provides better agreement with the angiographic data than triggering on every third heart cycle.
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Figure 2 illustrates a typical example of the DI versus time plot in a normal perfused septum; Figure 3 illustrates a typical example of the DI versus time plot in a hypoperfused septum.
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4 Discussion |
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TopAbstract1 Introduction2 Methods3 Results4 Discussion5 Limitations of the...6 ConclusionReferences |
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The qualitative visual assessment of the PDHI data as well as the quantitative analysis of the DI versus time plot during constant triggering has been shown to provide the detection of regional myocardial hypoperfusion.8,13,14 MCE using triggered PDHI has been shown to be the most sensitive method to image myocardial contrast in comparison to other contrast methods.5,9–14,18,19 Contrast infusion techniques are necessary to acquire PDHI data for calculation of a replenishment curve. This approach has become very popular in recent studies and is an attractive algorithm for quantitative perfusion analysis. Contrast infusion techniques however, seem to be limited for practical reasons. Using an i.v. bolus of contrast the first pass effect of the microbubbles through the myocardium is comparable to that of contrast agents in magnetic resonance studies.15–17 Thus, DI versus time plots can be obtained using PDHI with MCE. The plots, however, are influenced by cardiac output, inhomogeneous ultrasound field and the settings of the ultrasound system. According to previous results regional DI versus time plots provide the information about regional myocardial perfusion if cardiac output is in normal ranges and the ultrasound settings are kept constant.13,14
The pts of the present prospective study were investigated at rest within 6 h after an acute event of thoracic chest pain and within 2 h before invasive diagnostic and/or therapeutical intervention. Thus, the cohort represents hemodynamically stable pts with coronary artery who are obviously at risk of myocardial ischemia, and in whom a quick decision to angiography has to be taken. It is well known from experimental settings with healthy animals that a stenosis of more than 90% will induce significant resting myocardial flow reduction. Only six pts had a LAD occlusion or TIMI I- or TIMI II-flow. Thus, it has to be discussed why a reduced opacification of the septum indicated hypoperfusion in 25 pts. Normally, significant regional myocardial hypoperfusion will induce angina at rest. Regional hypoperfusion, however, was surprisingly detected in 22 of 24 pts at rest with MCE although only 12 pts had angina during the investigation. Explanations for this discrepancy can be repetitive stress-induced episodes of ischemia due to a reduction of coronary flow reserve presumably inducing stunning and/or limitations of perfusion at the microcirculatory level. Clinical studies also showed that narrowing of the coronary arteries between 50 and 85% could induce distinct reductions of myocardial blood volume and blood flow in pts with severe arteriosclerosis, especially during intermittent stress.6–8,13,18–21 In these cases myocardial perfusion seems to be significantly reduced although the pain threshold is not yet exceeded. Hypoperfusion can also be detected in the presence of hibernating myocardium, enhanced 
-adrenergic vasoconstriction after short-term ischemic episodes, and endothelial dysfunction with the formation of edema at the microcirculatory level and after repetitive microembolisms due to ruptures of instable plaques. In addition, it cannot be excluded that the reduction of the regional DI signal is due to disseminated myocardial infarctions in the pts with positive troponines levels. Therefore MCE in this study seems not only to identify pts with acute ischemia, but also pts with stunning and hibernating. This includes all pts with limitation of perfusion at the microcirculatory level.
Three additional questions arise using MCE by i.v. bolus application with PDHI in pts with acute chest pain at rest: 1. how can the contrast findings physiologically and methodologically can be explained?, 2. is MCE using PDHI practicable and feasible? and 3. can we get important additional information on top of a conventional echocardiogram?
The differences in the DI versus time plots between normal and ischemic myocardial regions may probably less due to the contrast ‘kinetics’. The plots represent the bolus and subsequent spreading as it passes to the systemic circulation. Using PDHI with short trigger intervals, the DI differences reflect differences in the rate of replenishment and blood volume. The different replenishment and blood volume in normal, ischemic as well as infarcted tissue generates the differences of the DI versus time plots. As illustrated in the scheme (see Fig. 1) the DI versus time plot in hypoperfused septal territories significantly differ from normal perfused areas: compared to normally perfused areas the DI maximum in hypoperfused myocardium is reduced, and the slope of DI wash-out in hypoperfused myocardium is decelerated. The reason contrast defects appear earlier during the ‘wash-out’ is that the concentration of microbubbles in the hypoperfused areas get below the saturation threshold of the ultrasound system sooner than in the normally perfused regions.
The present study shows that acquisition of the DI versus time plot during 1:1 triggering after i.v. contrast bolus is easy to perform especially in pts with acute coronary syndrome. In addition, the DI kinetics observed during 1:1 or 3:1 triggering in this study show a high reproducibility. It needs no additional staff and it does not significantly prolong a routine transthoracic echocardiography.
Important additional information is obtained within the LAD territory, which is not provided by other methods. Pts with acute chest pain and normal or non-specific ECG findings have a wide spectrum of differential diagnosis. MCE may play an important role identifying those pts with low flow conditions who need further invasive testing. Although the detection of septal wall motion abnormality seemed to be as sensitive as the contrast data for detecting hypoperfused myocardium, there were few pts in whom hypoperfusion and normal myocardial function as well as normoperfusion and hypokinesis were detected. Thus, the potential advantage of MCE could be the discrimination of regional myocardial dysfunction, which is not due to hypoperfusion.
The transfer of a diagnostic procedure from bench to bedside depends not only on its diagnotic value but also on its feasibility. The procedure of MCE does not prolong the door-to-needle time in pts with acute coronary syndromes. Therefore, MCE data acquisition and the MCE data analysis have to be performed easily and quickly in clinical practice as shown in the present paper by using the i.v. bolus approach and by the illustration of the regional DI tracings or the colored M-modes.
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5 Limitations of the study |
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TopAbstract1 Introduction2 Methods3 Results4 Discussion5 Limitations of the...6 ConclusionReferences |
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The main criticism of the present study is that coronary angiography cannot be considered a standard for detection of myocardial perfusion. Gold standards for perfusion measurements like scintigram or positron emission tomography could actually not be performed according to ethical aspects.
Complete contrast saturation is a methodological problem with the PDHI technique because of blooming artefacts and tissue attenuation. To avoid the weakness of analysis by eye the semiquantitative approach of DI wash-out was proposed to assess myocardial hypoperfusion more objectively. The high sensitivities and specificities to detect myocardial hypoperfusion in the LAD territory document the diagnostic efficacy of PDHI in acute pts with chest pain. However, the diagnostic efficacy depends on the investigators who had to be experienced with triggered imaging and the data analysis using the described algorithms. Because PDHI with MCE seems to be well practicable and efficient for the analysis of the LAD territory, PDHI measurements have to be evaluated in all left ventricular regions to clarify the feasibility of this method in the future. It is likely that diagnostic efficacy would be less in non-LAD territories due to methodological problems.
It has to be assumed that regional myocardial hypoperfusion is less frequent and less detectable at rest in non-symptomatic pts. Under these conditions inducible ischemia has to be provoked by stress tests to detect regional hypoperfusion. MCE during stress has to be evaluated in further studies. It is obvious that the PDHI data and their evaluation depend on the ultrasound system and on the settings, which have to be constant in all investigations.
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6 Conclusion |
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TopAbstract1 Introduction2 Methods3 Results4 Discussion5 Limitations of the...6 ConclusionReferences |
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This prospective trial demonstrated that PDHI is suitable to detect regional myocardial hypoperfusion in the LAD territory in clinical practice. The prerequisites are standardized bolus injection, cardiac performances within the normal ranges and constant ultrasound settings.
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Acknowledgements |
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The authors are grateful for the technical assistance to A. Golding, S. Herrmann, B. Müller, A. Nägler, and A. Ruschel.
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References |
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TopAbstract1 Introduction2 Methods3 Results4 Discussion5 Limitations of the...6 ConclusionReferences |
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- Wu X, Ewert D.L, Liu Y, Ritman E.L. In vivo relation of intramyocardial blood volume to myocardial perfusion: evidence supporting microvascular site for autoregulation. Circulation (1992) 85:730–737.
[Abstract/Free Full Text] - Firschke C, Lindner J.R, Wei K, Goodman N.C, Skyba D.M, Kaul S. Myocardial perfusion imaging in the setting of coronary artery stenosis and acute myocardial infarction using venous injection of a second-generation echocardiographic contrast agent. Circulation (1997) 96:959–967.[Web of Science][Medline]
- Wei K, Jayaweera A.R, Firoozan S, Linka A.Z, Skyba D.M, Kaul S. Quantification of myocardial blood flow with ultrasound-induce destruction of microbubbles administered as a constant venous infusion. Circulation (1998) 97:473–483.
[Abstract/Free Full Text] - Murthy T.H, Locvicchio E, Baisch C, Dairywala I, Armstrong W.F, Vannan M. Real-time myocardial blood flow imaging in normal human beings with the use of myocardial contrast echocardiography. J Am Soc Echocardiogr (2001) 14:698–705.[CrossRef][Web of Science][Medline]
- Wei K, Ragosta M, Thorpe J, Coggins M, Moos S, Kaul S. Noninvasive quantification of coronary blood flow reserve in humans using myocardial contrast echocardiography. Circulation (2001) 2560–2565.
- Kaul S, Jayaweera A. Coronary and myocardial blood volumes—noninvasive tools to assess the coronary microcirculation? Circulation (1997) 96:719–724.[Web of Science][Medline]
- Kaul S. Myocardial contrast echocardiography—15 years of research and development. Circulation (1997) 96:3747–3760.[Web of Science]
- Hagendorff A, Goeckritz A, Neugebauer A, Rother T, Pfeiffer D, Becher H. Intravenous myocardial contrast echocardiography during angioplasty. Echocardiography (2003) 20:527–531.[CrossRef][Web of Science][Medline]
- Linka A.Z, Sklenar J, Wei K, Jayaweera A.R, Skyba D.M, Kaul S. Assessment of transmural distribution of myocardial perfusion with contrast echocardiography. Circulation (1998) 98:1912–1920.
[Abstract/Free Full Text] - Lindner J.R, Villanueva F.S, Dent J.M, Wei K, Sklenar J, Kaul S. Assessment of resting perfusion with myocardial contrast echocardiography: theoretical and practical considerations. Am Heart J (2000) 139:231–240.[Web of Science][Medline]
- Senior R, Kaul S, Soman P, Lahiri A. Power Doppler harmonic imaging: a feasibility study of a new technique for the assessment of myocardial perfusion. Am Heart J (2000) 139:245–251.[Web of Science][Medline]
- Wei K, Jayaweera A.R, Firoozan S, Linka A, Skyba D.M, Kaul S. Basis for detection of stenosis using venous administration of microbubbles during myocardial contrast echocardiography: bolus or continuous infusion? J Am Coll Cardiol (1998) 32:252–260.
[Abstract/Free Full Text] - Hagendorff A, Göckritz A, Wunderlich A, Frigstad S, Pfeiffer D, Becher H. Determinants of myocardial hypoperfusion analyzed for the interventricular septum using power Doppler harmonic imaging with contrast echocardiography in humans—a methodological approach for clinical practice. J Am Soc Echocardiogr (2002) 15:404–415.[CrossRef][Web of Science][Medline]
- Hagendorff A, Göckritz A, Neugebauer A, et al. Assessment of regional myocardial hypoperfusion with myocardial contrast echocardiography using intravenous bolus application in patients with acute chest pain—a double case report. Eur J Echocardiogr, 2003; in press.
- Al-Saadi N, Nagel E, Gross M, et al. Noninvasive detection of myocardial ischemia from perfusion reserve based on cardiovascular magnetic resonance. Circulation (2000) 101:1379–1383.
[Abstract/Free Full Text] - Al-Saadi N, Nagel E, Gross M, et al. Improvement of myocardial perfusion reserve early after coronary intervention: assessment with cardiac magnetic resonance imaging. J Am Coll Cardiol (2000) 36:1557–1564.
[Abstract/Free Full Text] - Schwitter J, Nanz D, Kneifel S, et al. Assessment of myocardial perfusion in coronary artery disease by magnetic resonance—a comparison with positron emission tomography and coronary angiography. Circulation (2001) 103:2230–2235.
[Abstract/Free Full Text] - Lepper W, Hoffmann R, Kamp O, Franke A, deCock C.C, Kühl H.P. Assessment of myocardial reperfusion by intravenous myocardial contrast echocardiography and coronary flow reserve after primary percutaneous transluminal coronary angiography in patients with acute myocardial infarction. Circulation (2000) 101:2368–2374.
[Abstract/Free Full Text] - Heinle S.K, Noblin J, Goree-Best P, Mello A, Ravad G, Mull S. Assessment of myocardial perfusion by harmonic power Doppler imaging at rest and during adenosine stress—comparison with 99mTc-Sestamibi SPECT imaging. Circulation (2000) 102:55–60.
[Abstract/Free Full Text] - Agati L, Voci P, Autore C, et al. Combined use of dobutamine echocardiography and myocardial contrast echocardiography in predicting regional dysfunction recovery after coronary revascularization in patients with recent myocardial infarction. Eur Heart J (1997) 18:771–779.
[Abstract/Free Full Text] - Iliceto S, Galiuto L, Marchese A, Colonna P, Oliva S, Rizzon P. Functional role of microvascular integrity in patients with infarct-related artery patency after acute myocardial infarction. Eur Heart J (1997) 18:618–624.
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