EXPERIMENTAL STUDIES
Coronary collateral development during chronic ischemia: serial assessment using harmonic myocardial contrast echocardiography
James D. Mills, MD, FACCa,
David Fischer, BSa and
Flordeliza S. Villanueva, MD, FACCa
a Division of Cardiology, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
Manuscript received August 10, 1999;
revised manuscript received December 3, 1999,
accepted March 29, 2000.
Reprint requests and correspondence: Dr. Flordeliza S. Villanueva, Division of Cardiology, University of Pittsburgh, S568 Scaife Hall, 200 Lothrop Street, Pittsburgh, Pennsylvania 15213
villanuevafs{at}msx.upmc.edu
 |
Abstract
|
|---|
OBJECTIVES
We sought to characterize collateral development in an experimental model of chronic myocardial ischemia by using myocardial contrast echocardiography (MCE).
BACKGROUND
Coronary collaterals maintain myocyte viability during myocardial ischemia. The natural history and determinants of collateral development are difficult to study serially in vivo.
METHODS
The left anterior descending coronary artery (LAD) in nine dogs was encircled (day 0) with a hydraulic occluder and ameroid constrictor to enable reversible and gradual total LAD occlusion, respectively. Myocardial contrast echocardiography was performed using intravenous injection of perfluorocarbon gas-containing microbubbles during two-dimensional harmonic echocardiographic imaging. Myocardial contrast echocardiography images and radiolabeled microsphere flow measurements were obtained during transient LAD occlusion on day 0. Over the ensuing six weeks, MCE imaging was performed during LAD occlusion at 10-day intervals.
RESULTS
Myocardial contrast echocardiography risk area size (expressed as a percent of the left ventricular short axis slice) decreased over the course of six weeks (32% ± 3% on day 0, 21% ± 3% at day 10, 5 ± 3% at day 20, 1% ± 1% at day 30 and 1% ± 1% at day 42, p  0.001 vs. day 0). Radiolabeled microsphere-derived LAD flow, normalized to left circumflex flow, correspondingly increased between day 0 and day 42 (0.14 ± 0.02 to 0.90 ± 0.07, p < 0.02).
CONCLUSIONS
Collateral development occurs relatively early and rapidly in this chronic canine model. Myocardial contrast echocardiography using harmonic imaging and intravenous injection of microbubbles can uniquely track the spatial and temporal course of collateral growth, and may be a powerful tool for noninvasively mapping the efficacy of therapeutic angiogenic strategies in vivo.
|
Abbreviations and Acronyms
| | LAD | = left anterior descending coronary artery | | LCX | = left circumflex coronary artery | | MCE | = myocardial contrast echocardiography | | TTC | = triphenyl tetrazolium chloride |
|
The coronary collateral circulation provides an alternate supply of blood to myocardium at risk for necrosis during coronary occlusion. Collateral vessels mitigate myocardial ischemia (1), maintain myocyte viability during coronary occlusion (2) and limit the extent of infarction (3,4). The natural history and pathophysiologic determinants of angiogenesis and vasculogenic growth are not completely understood. Recent reports of successful attempts to stimulate
angiogenesis in animal and human models of ischemia (5–8) have spawned increasing interest in therapeutic angiogenesis and highlighted the need to demonstrate and measure the efficacy of such treatments.
Current methods to assess the development of the coronary collateral circulation have limitations. Coronary angiography, which is a common standard for clinically evaluating collateral flow, visualizes vessels with intraluminal diameters greater than 100 microns, whereas most collaterals are smaller in size (9,10). Radiolabeled microsphere technology is a postmortem method and has limited spatial resolution (11), as do scintigraphic perfusion imaging techniques (12).
Myocardial contrast echocardiography (MCE) is an ultrasound imaging technique that utilizes physiologically inert gas-filled microbubbles as red blood cell tracers (13). Because these microbubbles are acoustic scatterers as they transit the microcirculation in the presence of ultrasound, they delineate regional microvascular perfusion in vivo (14,15). These properties make MCE a potentially attractive imaging approach for studying the collateral circulation, but its requirement for intracoronary or intraaortic injection of fragile microbubbles has heretofore relegated its clinical application to invasive settings such as the cardiac catheterization laboratory or operating room (16,17). The recent development of more stable intravenous contrast agents and new ultrasound imaging approaches, such as harmonic imaging, has broadened the possibilities for using MCE in a noninvasive setting (18–21).
Based on these considerations, we sought to characterize the temporal course and spatial extent of coronary collateral development using MCE. We used a canine model of chronic, progressive coronary occlusion to test the hypothesis that serial harmonic echocardiographic imaging can noninvasively evaluate the natural history of coronary collateral development in real time.
|
Methods
|
|---|
Surgical preparation.
Day 0: initial instrumentation
The experimental protocol was approved by the Institutional Animal Care and Use Committee at the University of Pittsburgh and conformed to the American Heart Association Guidelines for Use of Animals in Research. Nine adult dogs were premedicated with transdermal fentanyl (75 µg/h), intravenous thiopental sodium (15 mg/kg), intubated and ventilated. A 21G peripheral intravenous catheter was placed in the forearm for administration of drugs and microbubbles. General anesthesia was maintained with 0.5% to 2.0%-inhaled isofluourane. Cefazolin (1.0–2.0 g, intravenous) was administered just before surgery and hourly thereafter.
A left lateral thoracotomy was performed, and the heart was suspended in a pericardial cradle. The right femoral artery was percutaneously cannulated with a 5F catheter for arterial pressure monitoring and radiolabeled microsphere reference sample withdrawal. The proximal left anterior descending coronary artery (LAD) was encircled with an ameroid constrictor (Research Instruments, Corvallis, Oregon) appropriately sized to progressively occlude the LAD by three weeks postoperatively (10). Immediately adjacent to the ameroid constrictor, a hydraulic balloon occluder (R.E. Jones Biomedical Products, Rockville, Maryland) was placed around the LAD and subcutaneously exteriorized to enable transient LAD occlusion during closed chest imaging. A 7F catheter was placed in the left atrium for radiolabeled microsphere injection.
The atrial and arterial catheters were removed before closure of the pericardium and chest, the dogs were allowed to recover and buprenorphine (6 µg/kg, intramuscular) was used for postoperative pain. Aspirin (325 mg, orally) was administered daily for 24 days to reduce the risk of acute thrombotic LAD occlusion.
In three dogs, a transit time flow probe (Transonic Systems Inc., Ithaca, New York) was placed around the mid-LAD, left in the chest and subcutaneously exteriorized upon chest closure. The probe was used to document complete absence of anterograde LAD flow during balloon occlusions. Additionally, serial flow probe readings were used to confirm total ameroid-induced LAD occlusion by three weeks postoperatively in our model.
Six weeks: terminal surgery
The dogs were returned to the operative suite after six weeks, anesthetized with 30 mg/kg sodium pentobarbital, intubated and mechanically ventilated. A left lateral thoracotomy was performed and the heart was exposed. 7F catheters were placed in the left atrium, femoral artery and femoral vein.
|
MCE
|
|---|
Harmonic B-mode MCE was performed using either of two imaging systems: HDI 3000 (Advanced Technology Laboratories, Bothell, Washington) transmitting at 1.8 MHz and receiving 3.6 MHz or a Hewlett-Packard 2500 prototype transmitting at 1.6 MHz and receiving at 3.2 MHz). Mechanical index varied from 0.7 to 0.9 in a given dog. Gain, depth and mechanical index were kept constant. Maximal dynamic range and a linear signal to video postprocessing algorithm were chosen.
Open chest epicardial imaging was performed on the initial and terminal days of surgery, while transthoracic MCE was performed periodically during the subsequent weeks. For these imaging sessions, conscious dogs were lightly sedated with acepromazine (0.1 mg/kg, intramuscular) and positioned in the right lateral decubitus position.
Myocardial contrast echocardiography imaging at the midpapillary muscle level in the short-axis plane was performed at baseline and during LAD occlusion, with ultrasound pulsing electrocardiographically gated to end-systole (19). Images were recorded on 1.25 cm sVHS videotape.
Microbubbles containing a mixture of gaseous perfluoropropane and air inside a bilayer phospholipid shell (Definity, DuPont Pharmaceuticals Company) was used as the contrast agent. This agent has a mean diameter of 2.3 microns, concentration of 1.2 x 109 bubbles/ml and does not produce significant physiologic changes (18). Myocardial contrast echocardiography was performed by slowly injecting 0.1 ml to 0.2 ml of the microbubbles through a peripheral intravenous catheter during simultaneous echocardiographic imaging.
Myocardial contrast echocardiography images were analyzed off-line using previously described digital subtraction techniques (22): images were transferred from videotape to image memory of a computer analysis system (Mipron, Kontron Electronics, Germany). Consecutive end-systolic frames were aligned using cross-correlation techniques, and background-subtracted videointensity data were derived from regions of interest in the LAD and left circumflex coronary artery (LCX) beds as defined on day 0 during brief LAD occlusion. Only regions of interest outside of attenuated areas were selected.
A previously described approach using digital subtraction and color-coding was used to delineate risk area size (22). Briefly, three precontrast end-systolic frames were averaged, and three contrast-enhanced end-systolic frames were similarly averaged. The averaged precontrast frame was digitally subtracted from the averaged contrast-enhanced frame. The gray scale values on the subtracted image were color-coded using a heated object color map, with red shades progressing to orange, yellow and white colors representing incremental degrees of contrast change (23). Regions with minimal myocardial flow during occlusion (risk area) were represented by little to no color enhancement and were planimetered and expressed as a percentage of the short-axis slice.
|
Determination of infarct size
|
|---|
Postmortem, the heart was excised, sliced cross-sectionally from base to apex and immersed in a solution of 1.3% 2,3,5-triphenyl tetrazolium chloride (TTC) and 0.2 mol/L Sorensen’s buffer (KH2PO4 and K2HPO4 in distilled water, pH 7.4) at 37° C for 20 min, followed by fixation in 10% formalin. This method stains viable areas brick red, while necrotic regions remain unstained (24). The TTC-stained slices were digitized into the off-line computer, and infarcted regions were planimetered and expressed as a percentage of the short-axis slice (15).
|
Regional myocardial blood flow measurement
|
|---|
Regional myocardial perfusion was measured using the radiolabeled microsphere technique (11). Approximately 2 x 106 11-µm radiolabeled microspheres (New England Nuclear, Boston, Massachusetts) were suspended in 3 ml of 0.9% saline solution/0.01% Tween 80. The microspheres were injected into the left atrium, followed by a flush, during simultaneous 90 s reference sample withdrawal from the femoral artery. The left ventricular short-axis slice corresponding to the MCE image was sectioned into 16 pieces, which were further divided into endocardial, midwall and epicardial portions. Tissue and reference samples were weighed and counted in a Gamma scintillation counter (model 5535, Packard Instruments, Downer’s Grove, Illinois), and data were transferred to a personal computer. Corrections for energy spillover into neighboring windows were made using customized software, and averaged transmural blood flow (ml/min/g) was calculated as previously described (11).
|
Experimental protocol
|
|---|
The six-week experimental protocol is diagrammed in Figure 1. On day 0, epicardial MCE was performed before and during transient LAD occlusion in order to define the area at risk. Radiolabeled microspheres (Sn113) were injected during transient LAD occlusion to measure the initial collateral flow to the risk bed, and the chest was closed as described above.
View larger version (25K):
[in this window]
[in a new window]
|
Figure 1 Outline of six-week experimental protocol. LAD = left anterior descending coronary artery; MCE = myocardial contrast echocardiography; Usph = radiolabeled microspheres.
|
|
Over the ensuing weeks, transthoracic MCE was performed three additional times at 10 day intervals with the dog in the conscious state. Images were obtained at baseline and during transient LAD occlusion using the externalized perivascular balloon occluder to delineate changes in collateral flow to the LAD risk bed.
Six weeks after instrumentation, the dog was returned to the operative suite and instrumented as described above. Myocardial contrast echocardiography imaging and radiolabeled microsphere injections were performed after a silk suture was tied around the LAD at the site of the ameroid. The dog was euthanized with pentobarbital and potassium chloride overdose, and the heart was excised and processed as described above. In two dogs, coronary arteriography performed three weeks after ameroid placement confirmed total LAD occlusion.
|
Statistical analysis
|
|---|
Data are expressed as mean ± SEM. Within-dog comparisons were made at successive time points using repeated measures analysis of variance (ANOVA). Paired t testing (2-tailed) was performed when a significant difference was found, and Bonferroni criteria were used to adjust for multiple comparisons. Statistical significance was defined as p < 0.05.
|
Results
|
|---|
Changes in MCE perfusion defect size.
There was a progressive decrease in MCE-determined risk area size during the six-week period, as exemplified in Figure 2, which illustrates serial open chest MCE images from one dog during LAD occlusion on day 0 (panel A) and the terminal day of the protocol (panel B). The left ventricle was filled with contrast, resulting in mild posterior wall attenuation in the field farthest from the transducer. On day 0, MCE during acute LAD occlusion demonstrated a risk area involving the anteroseptal and anterior segments (region between arrows). By week six, despite the presence of total LAD occlusion, there was homogeneous myocardial contrast enhancement, with contrast filling the region previously identified as the risk area on day 0.
View larger version (72K):
[in this window]
[in a new window]
|
Figure 2 Myocardial contrast echocardiography images in one dog demonstrating decrease in risk area size. On day 0 (panel A) there is a large anteroseptal and anterior perfusion defect during transient acute LAD occlusion (region between arrows), which is no longer present during chronic occlusion six weeks later (panel B). The curved double yellow lines schematically indicate the anterior right ventricular-left ventricular junction.
|
|
Figure 3 depicts transthoracic images obtained during the intervening weeks in the same dog shown in Figure 2. Because the dog was imaged in the right lateral decubitus position with the transducer on the right chest, the orientation of the short-axis image is reversed from that in Figure 2: the anterior segments appear in the far field, and the posterior segments and right ventricular cavity are in the near-field. At 10 days (Panel A), there is a relative perfusion defect that is smaller than that seen on day 0 (Fig. 2, Panel A), indicated by the orange region in the anterior septum (segment between arrows). By day 20 (Panel B), there is a subtle, small region of relative hypoperfusion (orange region between arrows), and by day 30 (Panel C) there is no detectable risk area despite total LAD occlusion. As shown in Panels A through C, the decrease in risk area size appeared to be due to progressive inward migration of the lateral and epicardial borders of the original risk bed, with the lowest intensity remaining in the center of the area at risk.
View larger version (56K):
[in this window]
[in a new window]
|
Figure 3 Serial MCE images obtained in the same dog shown in Figure 2 at day 10 (panel A), day 20 (panel B) and day 30 (panel C). There is a progressive decrease in perfusion defect size (region between arrows). The spatial orientation of these transthoracic images is opposite from the open chest images shown in Figure 2. The curved double yellow lines schematically represent the anterior right ventricular-left ventricular junction.
|
|
Of the nine dogs initially instrumented, one died suddenly two weeks after surgery. Figure 4 summarizes the risk area data in the surviving eight dogs. There was a significant decrease in perfusion defect size over time (p < 0.001). The risk bed measured 32% ± 3% of the left ventricular short-axis area on day 0 and decreased to 21% ± 3% at day 10, 5% ± 3% at day 20, 1% ± 1% at day 30 and 1% ± 1% on the terminal day of the protocol. In the two dogs with a persistent MCE defect on the terminal day, there was evidence of subendocardial infarction on postmortem TTC-staining, measuring 6% and 2% of the corresponding midpapillary short-axis slice, respectively.
View larger version (10K):
[in this window]
[in a new window]
|
Figure 4 Mean MCE perfusion defect size in all dogs, expressed as a percent of the short axis left ventricular slice. MCE = myocardial contrast echocardiography.
|
|
The peak videointensity measurements in the LAD bed, normalized to the LCX bed, are summarized in Figure 5. There was a significant increase in the relative LAD peak intensity between day 0 and the subsequent weeks (p < 0.01), with the peak intensity nearly equivalent to LCX intensity by the final day of imaging.
View larger version (12K):
[in this window]
[in a new window]
|
Figure 5 Ratio of videointensity in the LAD relative to LCX bed as a function of time. LAD = left anterior descending coronary artery; LCX = left circumflex coronary artery.
|
|
Radiolabeled microsphere flow.
Changes in microsphere-derived flow to the risk bed (expressed as LAD flow normalized to LCX flow) paralleled the MCE findings. There was a significant increase in collateral flow to the LAD risk bed between day 0 and day 42 (0.14 ± 0.05 vs. 0.90 ± 0.04, p < 0.01).
|
Discussion
|
|---|
We sought to prospectively characterize the temporal and spatial development of coronary collaterals in a clinically relevant model of chronic myocardial ischemia. This study demonstrates that MCE, using harmonic imaging and peripheral intravenous injection of microbubbles, can track the spatial distribution and time course of coronary collateral development in an ischemic bed over time. We suggest that this method may yield pathophysiologic insight into the process of collateral development and could be a potentially valuable tool to serially study angiogenesis in the clinical setting.
Natural history of collateral development in the canine model.
The dogs in this study had a substantial MCE-defined risk area during transient LAD occlusion on day 0. With the exception of two dogs that developed small subendocardial infarction, there was no identifiable risk area on the MCE images six weeks later, despite the presence of total LAD occlusion. The radiolabeled microsphere data confirm that blood flow to the occluded LAD bed was comparable with LCX flow by six weeks and significantly greater than flow to the acutely occluded LAD bed measured on day 0, indicating the interval development of functionally significant collaterals.
Serial MCE imaging highlighted two features of the natural history of collateral development in this model. First, it was shown that the restoration of flow to the risk bed begins relatively early after ameroid placement. This pattern is consistent with previous postmortem canine studies, indicating that the maturation of pre-existing collaterals, as opposed to de novo growth of vessels, constitutes an early phase of collateral development in chronically ischemic dogs (10,25).
Second, the MCE images indicate that the spatial pattern of collateral development appears to commence at the lateral borders of the risk bed, as shown by the progressive inward migration of risk bed borders over the course of six weeks, culminating in normalization of flow to the LAD bed. This observation is consistent with previous speculations concerning the existence of a collateral-dependent lateral risk bed border (26,27). In an acute model of coronary occlusion, Kaul et al. (28) found that the lateral borders of a risk bed were dynamic and could acutely change as a function of collateral perfusion pressure in the contralateral artery. The findings of this study support the existence of a lateral border and suggest that, in the dog, collateral flow initially emanates from this region.
Advantages of MCE for imaging collateral development.
Currently available techniques to study the coronary collateral circulation in vivo are limited. Coronary angiography is capable of delineating epicardial coronary anatomy but cannot define vessels less than 100 microns in size and is, thus, suboptimally suited for demonstrating total perfusion through collaterals (9). Furthermore, serial arteriographic assessment of collateral growth, in response to an intervention for example, is neither practical nor feasible. Similarly, radionuclide techniques such as thallium-201 scintigraphy or positron emission tomography are limited in spatial resolution and cannot be performed repetitively in short periods of time.
Anatomic and morphometric methods, such as postmortem casts, dyes and colored microspheres, have been used to identify coronary collateral macrovascular and microvascular anatomy (29–32). Using colored microspheres in canines, Cicutti et al., described the presence of an interface transition zone, which included a boundary watershed zone between two perfusion beds (29). This method, however, requires ex vivo analysis of myocardial tissue, precludes serial study of collateral development and, as with other anatomic methods, does not provide information on tissue perfusion.
Pearlman and colleagues (33) used magnetic resonance imaging with gadodiamide to assess myocardial perfusion in a porcine model of vascular endothelial growth factor-mediated angiogenesis. This approach, however, is limited by the heterogeneity in the intravascular flow of gadodiamide (which may alter the signal intensity) and the fact that gadodiamide extravasates from the intravascular space and is, thus, not a pure intravascular tracer.
Myocardial contrast echocardiography has unique advantages for the assessment of collateral blood flow. The microbubbles are physiologically inert, nonocclusive and remain entirely within the intravascular space (13). As shown in Figures 3 and 4, echocardiography delineates changes in the location of perfusion bed borders resulting from angiogenesis with a spatial resolution unavailable using other clinical imaging techniques.
The ability to spatially locate regions of collateral development can be a useful tool for understanding the physiology of angiogenesis. Unlike the anatomic methods described above, MCE interrogates the microvascular compartment and, thus, conveys information at the level of nutritive perfusion (34). Myocardial contrast echocardiography has the potential to provide more than mere anatomic information, such as physiologic data on collateral flow reserve (35). Furthermore, MCE can be performed repetitively.
Using intracoronary injections of microbubbles, Sabia et al. (2) demonstrated the existence of extensive collateral circulation in patients with recent infarction and a totally occluded infarct-related coronary artery. In that study, there was a poor correlation between the presence of angiographic and MCE collaterals, and it was the MCE collaterals that predicted improvement in left ventricular systolic function after revascularization.
The evaluation of collaterals using MCE has previously been limited by the requirement for intracoronary injection due to the fragility of air-filled microbubbles. The development of more robust microbubbles, and the observation that these microbubbles exhibit nonlinear acoustic behavior at ultrasound frequencies used in medical imaging, have been the bases for harmonic imaging (36). This study extends the work of Sabia et al. by demonstrating that not only can the existence of collaterals be identified at a given moment using MCE but also that the development of these collaterals can be tracked serially without the requirement for invasive coronary manipulation.
The relative contribution of microvascular versus macrovascular (epicardial) collateral development in this canine model has been debated (37,38). Although there are data to suggest the predominance of epicardial collateral maturation in the canine model (25), some studies also suggest a substantial contribution of new microvessel growth to the restoration of perfusion to the occluded bed (39). This study does not answer this question, but MCE may have the potential to parcel out these distinctions. Because 95% of intramyocardial blood volume consists of capillaries, the MCE image is predominantly a representation of capillary volume (40). We have previously shown, using intracoronary microbubble injection, that MCE can detect changes in coronary blood volume in the presence of nonflow limiting coronary stenosis (41). Using continuous intravenous contrast infusion and triggered harmonic imaging at varying cycles in acute models, Wei and colleagues (34) have recently suggested that MCE is capable of quantifying capillary cross sectional area. Using similar imaging methods, Linka et al. (42) have described a method for quantifying endocardial/epicardial intramyocardial volume ratios using MCE. With these unique capabilities for interrogating intramyocardial blood volume and its transmural distribution, MCE may yield insight into the pathophysiologic questions concerning micro- versus macrovascular collateral development during chronic myocardial ischemia.
Study limitations.
This is the first MCE demonstration of the natural history of collateral development. The approach using harmonic imaging and intravenous contrast agents for MCE is relatively new, and the optimal strategies for imaging have not been fully defined. For example, intravenous injection results in intense left ventricular cavity opacification, leading to attenuation and obscuration of perfusion bed borders. Additionally, although changes in relative videointensity measurements directionally paralleled changes in flow, this study did not establish a precise quantitative relationship between flow and videointensity measurements.
Approaches to quantification of blood flow using intravenous contrast injection are confounded by the extended nature of the contrast bolus, which precludes the application of indicator dilution theory, and the protracted exposure of bubbles to ultrasound, which results in microbubble destruction (40). Wei et al. (34) have recently reported a novel method based on the occurrence of microbubble destruction that uses continuous infusion of microbubbles with triggered imaging at varying intervals, which may have the potential to quantify both perfusion and intramyocardial blood volume (34) while minimizing the pitfalls of acoustic attenuation.
This study used an experimental model in which large resting perfusion defects were initially present and the subsequent collateral response was robust, thus favoring MCE detection of obvious changes in perfusion with time. In the application to human patients in whom angiogenesis is the therapeutic end point in question, resting defects may not be present, and the magnitude of change in perfusion resulting from collateral development may be less. It remains to be seen whether MCE can detect these subtler differences. In instances where there are no perfusion defects because resting flow remains normal despite severe coronary artery disease, MCE during pharmacologic stress may be required to elicit abnormalities in collateral flow reserve and to evaluate for changes in flow reserve resulting from angiogenic therapies. Moreover, the quantitative methods reported by Wei et al. (34) may enable more precise detection of subtle changes in perfusion resulting from collateral growth.
Future clinical applications.
There is individual variability in the propensity to develop collaterals, with the result being that some patients with coronary artery disease have more collaterals than others and are, thus, more protected against ischemia. Novel approaches to stimulating the growth of new vessels, such as therapeutic angiogenesis, have shown promise in both animal and early clinical trials (5–8). Myocardial contrast echocardiography may prove valuable in the progress of this effort in several ways. First, it provides a tool that may allow basic investigation of the physiology of collateral development in vivo that was heretofore not possible; its potential to quantify microvascular coronary volume (32) and distinguish endocardial-epicardial flow ratios (42) could broaden our understanding of the process of angiogenesis. Second, MCE could have practical clinical applications in the area of therapeutic angiogenesis: one of the challenges in designing clinical trials in myocardial angiogenesis is to delineate the optimal end points for defining therapeutic efficacy, some of which must necessarily include indexes of perfusion. The ability to monitor tissue perfusion serially in response to angiogenic treatments will be important to the advancement of this revascularization strategy to clinical settings. As shown in this study, MCE provides a readily accessible, portable, high resolution, nonradiographic method for evaluating collateral development over time, and may be a powerful tool for noninvasively mapping the efficacy of therapeutic angiogenic strategies.
|
Acknowledgments
|
|---|
The authors would like to thank DuPont Pharmaceuticals Company for providing the ultrasound contrast agent used in this study. They would also like to thank Maris Fenyus for providing technical assistance in animal care and in the performance of experiments.
|
Footnotes
|
|---|
Dr. Villaneuva was supported by a FIRST Award from the National Institutes of Health (R29 HL58865-01). Dr. Mills was supported by a fellowship grant from the American Heart Association, Pennsylvania Affiliate.
|
References
|
|---|
1. Levin DC. Pathways and functional significance of coronary collateral circulation. Circulation. 1974;50:831–837[Abstract/Free Full Text]
2. Sabia RJ, Powers ER, Jayaweera AR, Ragosta M, Kaul S. Functional significance of collateral blood flow in patients with recent acute myocardial infarction: a study using myocardial contrast echocardiography. N Engl J Med. 1992;327:1825–1831[Abstract]
3. Hirai T, Fujita M, Nakajima H, et al. Importance of collateral circulation for prevention of left ventricular aneurysm formation on acute myocardial infarction. Circulation. 1989;79:791–796[Abstract/Free Full Text]
4. Saito Y, Yasuno M, Ishida M, Suzuki K. Importance of coronary collaterals for restoration of left ventricular function after intracoronary thrombolysis. Am J Cardiol. 1985;55:1259–1263[CrossRef][Medline]
5. Takeshita S, Zheng LP, Brogi E, et al. Therapeutic angiogenesis. A single intraarterial bolus of vascular endothelial growth factor augments revascularization in a rabbit ischemic hind limb model. J Clin Invest. 1994;93:662–670[Medline]
6. Harada K, Friedman M, Lopez JJ, et al. Vascular endothelial growth factor administration in chronic myocardial ischemia. Am J Physiol. 1996;270:H1791–H1802[Medline]
7. Isner JM, Pieczek A, Schainfeld R, et al. Clinical evidence of angiogenesis after arterial gene transfer of phVEGF165 in patient with ischemic limb. Lancet. 1996;348:370–374[CrossRef][Medline]
8. Schumacher B, Pecher P, von Specht BU, Stegmann T. Induction of neoangiogenesis in ischemic myocardium by human growth factors: first clinical results of a new treatment of coronary heart disease. Circulation. 1998;97:645–650[Abstract/Free Full Text]
9. Jochem W, Soto B, Karp RB, Russell RO Jr, Holt JH, Barcia A. Radiographic anatomy of the coronary collateral circulation. Am J Roent Rad Ther Nuc Med. 1972;116:50–61
10. Schaper W. The Collateral Circulation of the Heart. New York: Elvesier; 1971.
11. Heymann MA, Payne BD, Hoffman JI, Rudolph AM. Blood flow measurements with radionuclide-labeled particles. Prog Cardiovasc Dis. 1977;20:55–79[CrossRef][Medline]
12. Beller GA. Clinical Nuclear Cardiology. Philadelphia: W.B. Saunders Co; 1995.
13. Jayaweera AR, Edwards N, Glasheen WP, Villanueva FS, Abbott RD, Kaul S. In vivo myocardial kinetics of air-filled albumin microbubbles during myocardial contrast echocardiography. Comparison with radiolabeled red blood cells. Circ Res. 1994;74:1157–1165[Abstract/Free Full Text]
14. Ragosta M, Camarano G, Kaul S, Powers ER, Sarembock IJ, Gimple LW. Microvascular integrity indicates myocellular viability in patients with recent myocardial infarction. New insights using myocardial contrast echocardiography. Circulation. 1994;89:2562–2569[Abstract/Free Full Text]
15. Villanueva FS, Glasheen WP, Sklenar J, Kaul S. Characterization of spatial patterns of flow within the reperfused myocardium by myocardial contrast echocardiography. Implications in determining extent of myocardial salvage. Circulation. 1993;88:2596–2606[Abstract/Free Full Text]
16. Ito H, Tomooka T, Sakai N, et al. Lack of myocardial perfusion immediately after successful thrombolysis. A predictor of poor recovery of left ventricular function in anterior myocardial infarction. Circulation. 1992;85:1699–1705[Abstract/Free Full Text]
17. Villanueva FS, Spotnitz WD, Jayaweera AR, Dent J, Gimple LW, Kaul S. On-line intraoperative quantitation of regional myocardial perfusion during coronary artery bypass graft operations with myocardial contrast two-dimensional echocardiography. J Thorac Cardiovasc Surg. 1992;104:1524–1531[Abstract]
18. Lindner JR, Firschke C, Wei K, Goodman NC, Skyba DM, Kaul S. Myocardial perfusion characteristics and hemodynamic profile of MRX-115, a venous echocardiographic contrast agent, during acute myocardial infarction. J Am Soc Echo. 1998;11:36–46[CrossRef][Medline]
19. Porter TR, Xie F. Transient myocardial contrast after initial exposure to diagnostic ultrasound pressures with minute doses of intravenously injected microbubbles. Demonstration and potential mechanisms. Circulation. 1995;92:2391–2395[Abstract/Free Full Text]
20. Mulvagh SL, Foley DA, Aeschbacher BC, Klarich KK, Seward JB. Second harmonic imaging of an intravenously administered echocardiographic contrast agent: visualization of coronary arteries and measurement of coronary blood flow. J Am Coll Cardiol. 1996;27:1519–2525[Abstract]
21. Porter TR, Xie F, Kricsfeld D, Armbruster RW. Improved myocardial contrast with second harmonic transient ultrasound response imaging in humans using intravenous perfluorocarbon-exposed sonicated dextrose albumin. J Am Coll Cardiol. 1996;27:1497–1501[Abstract]
22. Jayaweera AR, Matthew TL, Sklenar J, Spotnitz WD, Watson DD, Kaul S. Method for the quantitation of myocardial perfusion during myocardial contrast two-dimensional echocardiography. J Am Soc Echo. 1990;3:91–98[Medline]
23. Villanueva FS, Glasheen WP, Sklenar J, Jayaweera AR, Kaul S. Successful and reproducible myocardial opacification during two-dimensional echocardiography from right heart injection of contrast. Circulation. 1992;85:1557–1564[Abstract/Free Full Text]
24. Fishbein MC, Meerbaum S, Rit J, et al. Early phase acute myocardial infarct size quantification: validation of the triphenyl tetrazolium chloride tissue enzyme staining technique. Am Heart J. 1981;101:593–600[CrossRef][Medline]
25. Schaper J, Borgers M, Schaper W. Ultrastructure of ischemia-induced changes in the precapillary anastomotic network of the heart. Am J Cardiol. 1972;29:851–859[CrossRef][Medline]
26. Jugdutt BI, Becker LC, Hutchins GM. Early changes in collateral blood flow during myocardial infarction in conscious dogs. Am J Physiol. 1975;237:H371–H380
27. Jugdutt BI, Hutchins GM, Bulkley BH, Becker LC. Myocardial infarction in the conscious dog: three-dimensional mapping of infarct, collateral flow and region at risk. Circulation. 1979;60:1141–1150[Free Full Text]
28. Kaul S, Pandian NG, Guerrero JL, Gillam LD, Okada RD, Weyman AE. Effects of selectively altering collateral driving pressure on regional perfusion and function in occluded coronary bed in the dog. Circ Res. 1987;61:77–85[Abstract/Free Full Text]
29. Cicutti N, Rakusan K, Downey HF. Colored microspheres reveal interaraterial microvascular anastomoses in canine myocardium. Bas Res Cardiol. 1992;87:400–409[CrossRef][Medline]
30. Baroldi G, Mantero O, Scomazzoni G. The collateral of the coronary arteries in normal and pathologic hearts. Circ Res. 1956;4:223–229[Abstract/Free Full Text]
31. Schlesinger MJ. New radiopaque mass for vascular injection. Lab Invest. 1957;6:1–11[Medline]
32. James TN. Anatomy of the coronary arteries in health and disease. Circulation. 1965;32:1020–1033[Abstract/Free Full Text]
33. Pearlman JD, Hibberd MG, Chuang ML, et al. Magnetic resonance mapping demonstrates benefits of VEGF-induced myocardial angiogenesis. Nature Med. 1995;1:1085–1089[CrossRef][Medline]
34. Wei K, Skyba DM, Firschke C, Jayaweera AR, Lindner JR, Kaul S. Interactions between microbubbles and ultrasound: in vitro and in vivo observations. J Am Coll Cardiol. 1997;29:1081–1088[Abstract]
35. Villanueva FS, Camarano G, Ismail S, Goodman NC, Sklenar J, Kaul S. Coronary reserve abnormalities in the infarcted myocardium. Assessment of myocardial viability immediately versus late after reflow by contrast echocardiography. Circulation. 1996;94:748–754[Abstract/Free Full Text]
36. Burns PN. Harmonic imaging with ultrasound contrast agents. Clinical Radiol. 1996;51(Suppl 1):50–55
37. Harrison DG, Chapman MP, Christy JP, Marcus ML. Studies of functional site of origin of native coronary collaterals. Am J Physiol. 1986;251:H1217–H1224[Medline]
38. Przyklenk K, Vivaldi MT, Arnold JM, Schoen FJ, Kloner RA. Capillary anastomoses between the left anterior descending and circumflex circulations in the canine heart: possible importance during coronary artery occlusion. Microvasc Res. 1986;31:54–65[CrossRef][Medline]
39. Banai S, Jaklitsch MT, Shou M, et al. Angiogenic-induced enhancement of collateral blood flow to ischemic myocardium by vascular endothelial growth factor in dogs. Circulation. 1984;89:2183–2189
40. Wei K, Jayaweera AR, Firoozan S, Linka A, Skyba DM, Kaul S. Quantification of myocardial blood flow with ultrasound-induced destruction of microbubbles administered as a constant venous infusion. Circulation. 1998;97:473–483[Abstract/Free Full Text]
41. Wu CC, Feldman MD, Mills JD, et al. Myocardial contrast echocardiography can be used to quantify intramyocardial blood volume: new insights into structural mechanisms of coronary autoregulation. Circulation. 1997;96:1004–1011[Abstract/Free Full Text]
42. Linka A, Sklenar J, Wei K, Jayaweera A, Skyba DM, Kaul S. Assessment of transmural distribution of myocardial perfusion with contrast echocardiography. Circulation. 1998;98:1912–1920[Abstract/Free Full Text]
This article has been cited by other articles:
|
|
|
|
 
R. Vogel, R. Zbinden, A. Indermuhle, S. Windecker, B. Meier, and C. Seiler
Collateral-flow measurements in humans by myocardial contrast echocardiography: validation of coronary pressure-derived collateral-flow assessment
Eur. Heart J.,
January 2, 2006;
27(2):
157 - 165.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
S. Verma, M. A. Kuliszewski, S.-H. Li, P. E. Szmitko, L. Zucco, C.-H. Wang, M. V. Badiwala, D. A.G. Mickle, R. D. Weisel, P. W.M. Fedak, et al.
C-Reactive Protein Attenuates Endothelial Progenitor Cell Survival, Differentiation, and Function: Further Evidence of a Mechanistic Link Between C-Reactive Protein and Cardiovascular Disease
Circulation,
May 4, 2004;
109(17):
2058 - 2067.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
H. Fujii, S. Tomita, T. Nakatani, S. Fukuhara, A. Hanatani, Y. Ohtsu, M. Ishida, C. Yutani, K. Miyatake, and S. Kitamura
A novel application of myocardial contrast echocardiography to evaluate angiogenesis by autologous bone marrow cell transplantation in chronic ischemic pig model
J. Am. Coll. Cardiol.,
April 7, 2004;
43(7):
1299 - 1305.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
A. Distante, R. Dankowski, P. Mincarone, C.G. Leo, E. Gianicolo, P. Voci, M.A. Morales, and D. Rovai
Contrast echocardiography and medical economics: looking into the crystal ball
Eur. Heart J. Suppl.,
March 1, 2002;
4(suppl_C):
C39 - C47.
[Abstract]
[PDF]
|
|
|
|
|
|
|
F. S. Villanueva, E. W. Gertz, M. Csikari, G. Pulido, D. Fisher, and J. Sklenar
Detection of Coronary Artery Stenosis With Power Doppler Imaging
Circulation,
May 29, 2001;
103(21):
2624 - 2630.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
F. S. Villanueva, J. A. Abraham, G. F. Schreiner, M. Csikari, D. Fischer, J. D. Mills, U. Schellenberger, B. J. Koci, and J. S. Lee
Myocardial Contrast Echocardiography Can Be Used to Assess the Microvascular Response to Vascular Endothelial Growth Factor-121
Circulation,
February 12, 2002;
105(6):
759 - 765.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
Top
Abstract
Methods