Biomedical subjects

J Sklenar

Publications and source records attributed to J Sklenar.

17 recordsLinked to original sources

PubMed2001

Noninvasive prediction of ultimate infarct size at the time of acute coronary occlusion based on the extent and magnitude of collateral-derived myocardial blood flow.

BACKGROUND: We hypothesized that by detecting regions with adequate collateral-derived myocardial blood flow (MBF) within the risk area (RA), we could predict ultimate infarct size (IS) at the time of coronary occlusion. METHODS AND RESULTS: Group 1 dogs (n=15) underwent coronary occlusion without reperfusion, whereas group 2 dogs (n=6) underwent both occlusion and reperfusion. RA was measured with aortic root injections of microbubbles. Myocardial contrast echocardiography (MCE) was performed with high mechanical index intermittent harmonic imaging at pulsing intervals (PIs) of <1 to 30 cardiac cycles during an intravenous infusion of microbubbles (Sonozoid). MBF was measured with radiolabeled microspheres, and postmortem tissue staining was used to determine IS. Perfusion defect size (PDS) on MCE varied with the PI and was largest at a PI of 2.6+/-0.4 seconds, where it correlated well with RA (r=0.82). PDS was smallest at a PI of >/=10.6+/-1.5 seconds, where it correlated closely with IS (r>/=0.92). Areas that underwent necrosis could be identified early after coronary occlusion as having the lowest microvascular flow velocity (beta) and MCE-derived MBF (Axbeta). The results were similar with or without reperfusion. Because of variability in collateral-derived MBF, there was no correlation between RA and ultimate IS (P=0.37). The extent of regional dysfunction also correlated poorly with IS (r=0.31). CONCLUSIONS: MCE can be used immediately after coronary occlusion to define ultimate IS by measuring the magnitude and spatial extent of collateral-derived residual MBF within the RA. Thus, it could help individualize risk and management in acute myocardial infarction.

Animals↗

PubMed2001

Detection of coronary artery stenosis with power Doppler imaging.

BACKGROUND: Power Doppler is a new imaging method for detecting microbubbles during myocardial contrast echocardiography (MCE) based on the registration of variance resulting from ultrasound-induced nonlinear bubble behavior. We tested the hypothesis that power Doppler imaging can be used to quantify coronary stenoses. METHODS AND RESULTS: Three left anterior descending (LAD) coronary stenoses of varying severity were created in each of 9 open-chest dogs. MCE was performed by continuous intravenous infusion of a nitrogen-filled bilayer shell microbubble, PB127, during triggered power Doppler imaging at incremental pulsing intervals. MCE and radiolabeled microsphere measurements were made at baseline and during each stenosis, with and without adenosine stress. Videointensities in the LAD and left circumflex (LCx) beds were plotted against pulsing interval and fit to a previously described exponential function modeling microbubble destruction and replenishment, which was used to derive parameters of bubble velocity (beta) and peak plateau videointensity (A). Contrast defects matching the location of radiolabeled microsphere hypoperfusion were clearly seen, without need for image processing. The product of beta and A was linearly related to LAD/LCx flow (r=0.90, P<0.0001) and inversely related to stenosis gradient (r=-0.70, P<0.0001). Endocardial/epicardial flow ratios were visualized and quantifiable. CONCLUSIONS: As with B-mode harmonics, a model of microbubble destruction/replenishment can be applied to power Doppler data as a means to detect a broad range of stenoses. Image clarity and the lack of attenuation or requirement for background subtraction are additional advantages of this imaging approach. Power Doppler MCE imaging holds promise for the detection of coronary artery disease.

Animals↗

PubMed2000

Ordering an echocardiogram for evaluation of left ventricular function: level of expertise necessary for efficient use.

This prospective study was performed to test the hypothesis that the yield of 2-dimensional echocardiography (2DE) would be higher when it is ordered by a cardiologist than by a noncardiologist. Patients referred for transthoracic 2DE for the evaluation of left ventricular systolic function for the 11-month period between July 10, 1995, and June 10, 1996, were included in the study. Demographic, historical, and clinical findings were recorded. Whether the patient was referred by a cardiologist versus a noncardiologist was used as the predictor variable in a binary logistic regression analysis. To address the possibility that the yield of 2DE may be higher for cardiologists because the prevalence of disease in patients referred to them may be higher (selection bias), the analysis was subjected to a propensity score adjustment. Of 2176 patients referred for 2DE during the study, 1033 were referred for the evaluation of left ventricular function. The test had a positive yield in 52% of patients for cardiologists versus 31% for noncardiologists (chi(2) = 45.5, P <.0001, odds ratio 2.4 [CI = 1. 9-3.1]). This difference remained highly significant even when propensity score risk adjustment was made (chi(2) = 54.2, P <.0001, odds ratio 2.0 [CI = 1.5-2.8]). We conclude that the yield of 2DE is higher for cardiologists compared with noncardiologists and that this result was not related to differences in patient populations examined by the two groups. Thus, more efficient use of 2DE may be achieved if patients are referred to cardiologists rather than directly sent for 2DE.

Aged↗

PubMed2000

Assessment of resting perfusion with myocardial contrast echocardiography: theoretical and practical considerations.

BACKGROUND: The aim of this study was to perform a quantitative comparison between myocardial contrast echocardiography (MCE) and single-photon emission computed tomography (SPECT) in patients with prior myocardial infarction (MI). We also wanted to determine the optimal method for the intravenous administration of an ultrasound contrast agent in the clinical setting. METHODS AND RESULTS: Seventeen patients with resting perfusion defects in a single vascular territory on SPECT were studied. MCE was performed with intermittent harmonic imaging during continuous infusions of a second-generation ultrasound contrast agent (Sonovue, Bracco Diagnostics) in all 17 patients and after bolus injection in 8 of them. During continuous infusions, the video intensity (VI) ratio between the abnormal and normal myocardium at a pulsing interval (PI) of 8 cardiac cycles correlated well with the activity ratio between these segments on SPECT (r = 0.73, P <.01). When information regarding microbubble velocity (MV) denoted as change in VI with increasing PIs was added, the correlation with SPECT activity ratio improved (P <.05) significantly (r = 0.87, P <.0001). Higher microbubble doses resulted in higher VI during continuous infusions with good myocardial opacification and no far-field attenuation until the highest dose was reached. With bolus injections, the VI ratio between the abnormal and normal myocardium at PI of 1 and 5 cardiac cycles showed a modest correlation (r = 0.46 and r = 0.48, respectively, P <.05) with activity ratios between these regions on SPECT. When a dose of microbubbles administered as a bolus produced adequate myocardial opacification, it invariably resulted in far-field attenuation. CONCLUSIONS: In patients with prior MI, quantitative assessment of resting perfusion defects on MCE correlates well with regional activity on SPECT. Continuous infusions offer an advantage over bolus injections because they can provide an assessment of both relative VI and MV. Adjustment of the microbubble infusion rate produces adequate myocardial opacification without attenuation.

Coronary Circulation↗

PubMed2000

Efficient utilization of echocardiography for the assessment of left ventricular systolic function.

BACKGROUND: We hypothesized that patients could be selected for echocardiographic evaluation of left ventricular (LV) systolic function on the basis of historic, clinical, radiographic, and electrocardiographic criteria. METHODS AND RESULTS: We prospectively evaluated 300 consecutive inpatients referred for the echocardiographic assessment of LV function, of whom 124 (41%) had LV systolic dysfunction (LVSD) (LV ejection fraction <0.45). Among the historic variables, male sex was the only predictor of LVSD, whereas of the abnormal physical and radiographic findings, cardiomegaly on chest radiography was the only predictor. Among the electrocardiographic findings, the presence of left bundle branch block was positively correlated with the presence of LVSD, whereas a normal electrocardiogram was negatively correlated with this finding. Only 2 patients with LVSD had a normal electrocardiogram. The addition of significant predictors on physical examination and chest radiography doubled the predictive value of the historic variables for determining LVSD. The addition of electrocardiographic findings further doubled the predictive value of the model. Almost 45% of the predictive power of the final multivariate model (chi-square of 48 of the total chi-square of 108) was based on the absence of normal electrocardiogram in patients with LVSD. When chest radiographic findings were excluded from the model, the overall predictive power of the model did not change, with the normal electrocardiogram gaining greater prominence: Full 56% of the predictive power of the model (chi-square of 60 of the total chi-square of 108) resided in the ability of a normal electrocardiogram to discriminate between patients with and those without LVSD. CONCLUSIONS: Historic, chest radiographic, and electrocardiographic variables can be used to predict low likelihood of LVSD on echocardiography. In particular, when the electrocardiogram is normal, it is extremely unlikely to have LVSD. It can be argued that such patients should not be referred for echocardiography.

Aged↗

PubMed1999

Potential advantage of flash echocardiography for digital subtraction of B-mode images acquired during myocardial contrast echocardiography.

Optimal assessment of myocardial perfusion with contrast echocardiography by using B-mode imaging often requires image alignment and background subtraction, which are time consuming and need extensive expertise. Flash echocardiography is a new technique in which primary images are gated to the electrocardiogram and secondary images are obtained by transmitting ultrasound pulses in rapid succession after each primary image. Myocardial opacification is seen in the primary image and not in the secondary images because of ultrasound-induced bubble destruction. Because the interval between the primary and first few secondary images is very short, cardiac motion between these images should be minimal. Therefore we hypothesized that 1 or more secondary images could be subtracted from the primary image without the need for image alignment. The ability of ultrasound to destroy microbubbles was assessed by varying the sampling rate, line density, and mechanical index in 6 open-chest dogs. The degree of translation between images was quantified in the x and y directions with the use of computer cross-correlation. At sampling rates of 158 Hz or less and a mechanical index of more than 0.6, videointensity rapidly declined to baseline levels by 25 ms. Significant translation between images was noted only at intervals of more than 112 ms. It is concluded that flash echocardiography can be used for digital subtraction of baseline from contrast-enhanced B-mode images without image alignment. Background subtraction is therefore feasible on-line, potentially eliminating the need for off-line image processing in the future.

Animals↗

PubMed1998

Assessment of transmural distribution of myocardial perfusion with contrast echocardiography.

BACKGROUND: We hypothesized that by using our newly defined method of destroying microbubbles and measuring their rate of tissue replenishment, we could assess the transmural distribution of myocardial perfusion. METHODS AND RESULTS: We studied 12 dogs before and after creation of left anterior descending coronary artery stenoses both at rest and during hyperemia (n=62 stages). Microbubbles were administered as a constant infusion, and myocardial contrast echocardiography (MCE) was performed with the use of different pulsing intervals. The video intensity versus pulsing interval plots derived from each myocardial pixel were fitted to an exponential function: y=A(1-ebetat), where A reflects microvascular cross-sectional area (or myocardial blood volume), and beta reflects mean myocardial microbubble velocity. The product A . beta represents myocardial blood flow (MBF). Average values for these parameters were derived from the endocardial and epicardial regions of interest placed over the left anterior descending coronary artery bed. Radiolabeled microsphere-derived MBF was also measured from the same regions. There was poor correlation between radiolabeled microsphere-derived MBF and A-endocardial/epicardial ratios (EER) (r=0.46). The correlation with beta-EER was better (r=0. 69, P<0.01). The best correlation with radiolabeled microsphere-derived MBF-EER was noted with A . beta-EER (r=0.88, P<0. 01). CONCLUSIONS: The transmural distribution of myocardial perfusion can be accurately assessed with MCE with the use of our newly described method of tissue replenishment of microbubbles after their ultrasound-induced destruction. In the model studied, an uncoupling of the transmural distribution of MBF and myocardial blood volume was observed during reversal of the MBF-EER.

Air↗

PubMed1996

Contractile versus microvascular reserve for the determination of the extent of myocardial salvage after reperfusion. The effect of residual coronary stenosis.

BACKGROUND: We hypothesized that microvascular reserve is a better indicator of the extent of viable myocardium postinfarction than contractile reserve, especially in the presence of a residual stenosis of the infarct-related artery. METHODS AND RESULTS: Fifteen dogs with various infarct sizes were studied after reperfusion. Contractile reserve, studied by use of dobutamine echocardiography, and microvascular reserve, studied by use of myocardial contrast echocardiography, were measured both before and after creation of a stenosis. In the absence of a stenosis, the relation between infarct size, expressed as percent of risk area, and wall thickening improved with increasing doses of dobutamine (r = .41, .71, and .90 for 5, 10, and 15 micrograms.kg-1.min-1, respectively; P < .01 for dobutamine 15 micrograms.kg-1.min-1). In the presence of a stenosis, however, the relation was poor for all doses of dobutamine (r = .22, .57, and .32 for 5, 10, and 15 micrograms.kg-1.min-1, respectively; P < .01 for 15 micrograms.kg-1.min-1 dobutamine in the absence of a stenosis). There was a fair correlation between infarct size and perfusion defect size on myocardial contrast echocardiography after reperfusion (r = .82), with the defect size underestimating infarct size by approximately 20%. This relationship improved (P < .01) during infusions of both adenosine (r = .99) and dobutamine (r = .94) in the absence of a stenosis. The correlations between infarct size and perfusion defect on myocardial contrast echocardiography also remained good in the presence of a stenosis (r = .95 and .81 for adenosine and dobutamine, respectively; P = NS compared with stenosis). CONCLUSIONS: Microvascular reserve is superior to contractile reserve for definition of the spatial topography of necrosis and hence the extent of viable myocardium within the infarct bed after reperfusion, particularly when a residual stenosis is present in the infarct-related artery.

Adenosine↗

PubMed1996

Coronary reserve abnormalities in the infarcted myocardium. Assessment of myocardial viability immediately versus late after reflow by contrast echocardiography.

BACKGROUND: The aim of this study was to determine whether myocardial contrast echocardiography (MCE) during exogenous vasodilation can accurately delineate infarct size, and hence the extent of myocardial viability, both immediately (15 minutes) and late (3 hours) after reperfusion when postreflow coronary hyperema is still present. METHODS AND RESULTS: Twenty-one open-chest anesthetized dogs underwent 3 to 6 hours of coronary occlusion followed by reperfusion. MCE was performed 15 minutes after reflow before and during infusion of 0.2 mg.kg-1.min-1 adenosine i.v.. In 12 dogs, infarct size was measured at this time. In the remaining 9 dogs, reperfusion was continued for 3 hours, when MCE was repeated before and after an infusion of 0.56 mg.kg-1.min-1 dipyridamole i.v. and infarct size was measured. In the absence of adenosine, MCE perfusion defect at 15 minutes underestimated infarct sizes at both 15 minutes and 3 hours, whereas in the presence of adenosine, the estimate of infarct size was more accurate. Similarly, in the absence of dipyridamole, although MCE perfusion defect underestimated infarct size (both measured 3 hours after reflow), in the presence of dipyridamole, the estimate of infarct size was more accurate. CONCLUSIONS: By unmasking abnormalities in flow reserve within the infarct bed, MCE in conjunction with coronary vasodilators can accurately predict infarct size both 15 minutes and 3 hours after reperfusion. Thus, MCE can be used for assessing the extent of myocardial viability both immediately and late after reperfusion when postreflow coronary hyperemia is still present.

Adenosine↗

PubMed1994

Quantification of images obtained during myocardial contrast echocardiography.

This article describes currently used quantitative methods for analysis of data obtained during myocardial contrast echocardiography. The specific issues addressed are: obtaining time-intensity curves from the myocardium in order to derive transit rates of microbubbles through the myocardium; defining spatial distribution of flow within a myocardial segment; and color-coding algorithms used to define the extent and magnitude of hypoperfusion within a cross-section of the heart. These methods are being adopted by several companies dealing with acquisition and analysis of echocardiographic data and should become available soon for clinical use.

Algorithms↗

PubMed1994

Dobutamine echocardiography for determining the extent of myocardial salvage after reperfusion. An experimental evaluation.

BACKGROUND: Although dobutamine echocardiography is being increasingly used to determine the presence of viable myocardium in patients who have undergone successful reperfusion therapy, the physiological basis for such a use has not been clearly defined. Because postischemic myocardium has contractile reserve, we hypothesized that the absolute degree of wall thickening induced by dobutamine during reflow would be directly related to the amount of myocardium that has escaped necrosis. METHODS AND RESULTS: Three groups of 12 dogs each were studied at baseline and during 2 to 6 hours of coronary artery occlusion and 15 minutes of reperfusion. In group 1 dogs, which did not receive dobutamine during any of these stages, percent wall thickening at these stages was 32 +/- 6%, -2 +/- 6%, and 5 +/- 6%, respectively, and there was no relation between infarct size and percent wall thickening during reflow (r = .20, P = .51). In group 2 dogs, which received 15 micrograms/kg per minute of dobutamine at all stages, wall thickening at these stages was 40 +/- 8%, 0 +/- 8%, and 19 +/- 10%, respectively, and a good inverse correlation was noted between infarct size and percent wall thickening during reflow (r = -.81, P = .001). In group 3 dogs, in which wall thickening during reflow was measured both before and during infusion of 15 micrograms/kg per minute of dobutamine, it was 5 +/- 8% and 18 +/- 14%, respectively, at these stages. Although the correlation between infarct size and percent wall thickening was poor in the absence of dobutamine (r = .36, P = .26), an excellent inverse correlation was noted between the two in the presence of dobutamine (r = -.93, P < .001). A fair inverse correlation was also noted between infarct size and the absolute change in wall thickening induced by dobutamine (r = -.72, P < .01). Maximal wall thickening was noted at a dobutamine dose of 15 micrograms/kg per minute, and lower doses did not elicit thickening in the presence of larger infarcts despite the presence of viable myocardium. CONCLUSIONS: When myocardial necrosis coexists with post-ischemic myocardial dysfunction and no residual coronary stenosis, the absolute degree of wall thickening during dobutamine can be used to determine the extent of myocardium that has escaped necrosis. The dose of dobutamine needed to elicit maximal thickening of the postischemic myocardium is related to the amount of myocardial necrosis.

Animals↗

PubMed1993

Assessment of risk area during coronary occlusion and infarct size after reperfusion with myocardial contrast echocardiography using left and right atrial injections of contrast.

BACKGROUND: Myocardial opacification during echocardiography has been demonstrated after left (LA) and right (RA) atrial injections of contrast, and microvascular damage with reduced blood flow and impaired flow reserve has been documented in necrotic myocardial tissue. Therefore, we hypothesized that because of its ability to depict capillary perfusion, myocardial contrast echocardiography (MCE) can be used to define risk area during coronary occlusion and infarct size after reperfusion with LA and RA injections of contrast in the presence of pharmacologically induced coronary hyperemia. METHODS AND RESULTS: Eighteen open-chest anesthetized dogs with 3 to 6 hours of left anterior descending artery occlusion and 15 minutes of reflow were studied in the presence of either dipyridamole (0.56 mg/kg over a period of 4 minutes) or dobutamine (15 micrograms.kg-1.min-1). Technetium autoradiography was performed for risk area assessment; infarct size was measured with triphenyl tetrazolium chloride; and in 11 dogs, myocardial blood flow was measured with radiolabeled microspheres. A close linear relation was noted between the MCE defect size and autoradiographic risk area during coronary occlusion both during LA (y = 0.95x-0.25, r = .97, P < .001) and RA (y = 0.90x+0.98, r = .86, P < .001) injections of contrast. During reperfusion, the contrast defect size on MCE was always less transmural than during occlusion and correlated closely with infarct size during both LA (y = 1.07x-2.37, r = .98, P < .001) and RA (y = 1.02x-0.61, r = .95, P < .001) injections of contrast. In the 11 dogs in whom radiolabeled microsphere-derived blood flow was measured during reperfusion, an inverse relation was noted between infarct size and transmural blood flow (y = -1.12x+121, r = -.95, P = .001), implying that MCE defects after reperfusion indicate necrotic regions with reduced blood flow or impaired microvascular flow reserve. A close linear relation (y = 0.79x-0.001, r = .98, P < .001) was also noted between endocardial/epicardial ratio of background-subtracted peak video intensity on MCE and endocardial/epicardial blood flow ratio in the eight dogs with infarction who underwent this measurement after reperfusion. CONCLUSIONS: MCE performed with LA and RA injections of contrast in the presence of pharmacologically induced coronary hyperemia can be used to determine, in vivo, the risk area during coronary occlusion and infarct size after reperfusion. These results could have important implications in this era of myocardial reperfusion.

Animals↗

PubMed1993

Characterization of spatial patterns of flow within the reperfused myocardium by myocardial contrast echocardiography. Implications in determining extent of myocardial salvage.

BACKGROUND: Since myocardial blood flow changes dynamically after reperfusion and since both hyperemia and impairment in microvascular function exist within the acutely reperfused bed, we sought to investigate the role of myocardial contrast echocardiography (MCE) in (1) defining the temporal variability in perfusion patterns after reflow and relating these to microsphere-derived blood flow; (2) differentiating viable from infarcted tissue during different periods of reflow; and (3) defining spatial perfusion patterns within the infarct bed in response to exogenously induced maximal vasodilation and relating these to infarct size and extent of myocardial salvage. METHODS AND RESULTS: Twenty-one dogs with 3 hours of left anterior descending coronary artery occlusion and 2 to 3 hours of reflow were studied. MCE was performed at 15 and 45 minutes and 2 and 3 hours after reflow. It was also performed at either 2 or 3 hours after reflow in the presence of 0.56 mg/kg of dipyridamole. Radiolabeled microsphere-derived blood flow was measured at 15 minutes and 2 and 3 hours after reflow and during dipyridamole effect. Infarct size was measured at the end of the experiment by use of triphenyl tetrazolium chloride. MCE data were processed with color-coding schemes that highlighted differences in myocardial videointensities in proportion to the concentration of microbubbles within the microvasculature. There was significant variability in MCE-defined perfusion patterns after reflow, with contrast defects noted mainly within the endocardium. There were fair and significant (P < .05) correlation (r = -.73 to r = -.55) between MCE defect size and normalized endocardial blood flow. Except at 15 minutes after reflow, there was poor correlation (r = .31 to r = .51) between MCE defect and infarct sizes. Even at 15 minutes after reflow, MCE defect size underestimated infarct size by 50%. In comparison, in the presence of dipyridamole, MCE defect size correlated strongly (r = .87, P < .001) with infarct size and reasonably well with normalized transmural blood flow (r = -.62, P = .04). Moreover, the topography of the MCE perfusion defect reflected the topography of the infarct. CONCLUSIONS: MCE revealed striking temporal heterogeneity in the spatial distribution of myocardial perfusion during postischemia reflow and either significantly underestimated or did not correlate with infarct size during reperfusion. Because of abnormalities in coronary vascular reserve specific to infarcted tissue, MCE in conjunction with intravenous dipyridamole depicted, in vivo, the actual topography of the infarct with remarkable accuracy.

Animals↗

PubMed1992

Successful and reproducible myocardial opacification during two-dimensional echocardiography from right heart injection of contrast.

BACKGROUND: Myocardial contrast echocardiography currently involves intro-arterial injection of contrast. For this technique to have a broader application, it is necessary that myocardial opacification be achieved from a venous injection of contrast. METHODS AND RESULTS: To achieve myocardial opacification after right-side injection of contrast, two groups of open-chest anesthetized dogs were studied. Group 1 included nine dogs in whom microbubbles of various sizes, concentrations, and volumes were injected into the left atrium to determine microbubble characteristics that influence myocardial opacification. Group 2 included eight dogs in whom the effect of the combination of microbubble characteristics and myocardial blood flow on myocardial opacification was evaluated after right atrial injection of contrast. Background-subtracted time-intensity plots were generated from the myocardium to measure peak videointensity. In the group 2 dogs, digital subtraction and color coding were used to further highlight the contrast effect. The number, concentration, and size of the microbubbles all independently affected (p less than 0.01) peak myocardial videointensity after left atrial injection of contrast on multivariate analysis. Highly concentrated microbubbles (4.4 to 5.1 billion/ml) given during dipyridamole-induced coronary hyperemia was most frequently (88%) associated with myocardial opacification after right atrial injection of contrast and was the best predictor of this result on multivariate analysis (chi 2= 9.01, p = 0.003). No changes were noted in left atrial, left ventricular, and pulmonary artery pressures despite injection of large numbers of microbubbles into the right atrium. CONCLUSIONS: Successful and reproducible myocardial opacification can be achieved during myocardial contrast echocardiography after right atrial injection of contrast. These findings could have far-reaching implications in the use of myocardial contrast echocardiography in acute and chronic ischemic syndromes in humans.

Algorithms↗

PubMedDate not supplied

Integrated backscatter and digital acquisition during myocardial contrast echocardiography: is there an advantage over conventional echocardiography for intracoronary injections?

This study was designed to answer the question of whether, despite their theoretic superiority, integrated backscatter imaging (IBS) and digital data acquisition (DA) offer any advantage over conventional echocardiography (CE) during quantitative myocardial contrast echocardiography. In vitro experiments were performed (1) to determine the microbubble concentration versus videointensity relationships for CE and IBS and (2) to define the relationship between flow through and microbubble transit rates for CE and IBS. These data were stored on videotape. In vivo experiments were performed whereby microbubbles were injected into the left anterior descending artery at different flow rates in 14 dogs and IBS and CE data were stored both in digital format and on videotape. Although the level of compression did not affect the microbubble concentration versus videointensity plots during IBS compared with CE, in practical terms the mean transit rate, peak intensity, and area under the curve were not affected by the level of compression for both forms of imaging as long as the postprocessing used for CE imaging was linear and the microbubble dose was small. In addition, although DA resulted in higher peak intensity and area under the curve compared with storage on videotape because of its broader dynamic range, the correlation between these measurements was excellent with both forms of image storage. We conclude that, although differences exist between CE and IBS and between Da and analog acquisition, these differences do not significantly affect the derivation of parameters from time-intensity plots during myocardial contrast echocardiography when contrast material is injected into a coronary artery.

Animals↗

PubMedDate not supplied

A computer-aided approach for the quantitation of regional left ventricular function using two-dimensional echocardiography.

Quantitation of regional left ventricular function is becoming increasingly important in this era of interventional cardiology. In this article we describe a computer-assisted approach for the assessment of regional left ventricular function that integrates three features. First, it measures left ventricular wall thickening and endocardial motion and curvature during an entire systolic contraction sequence. Second, it allows us to easily define endocardial and epicardial borders without actually having to manually trace the entire border. Third, it displays complex data in a simple format for easy assimilation. We believe that this approach is practical and comprehensive and can be used to quantitate regional left ventricular function with two-dimensional echocardiography.

Color↗

PubMedDate not supplied

Method for the quantitation of myocardial perfusion during myocardial contrast two-dimensional echocardiography.

This article describes the hardware and software components of two systems designed for quantitative analysis of data obtained during myocardial contrast two-dimensional echocardiography. One system is meant for off-line analysis of data, whereas the other is designed for on-line analysis, especially in the operating room. The algorithms used for data transfer, selection of appropriate frames, data alignment, derivation of time-intensity plots, and curve-fitting and parameter generation are described in some detail. It is hoped that this information will be of use to others who work in the field of myocardial perfusion imaging.

Algorithms↗