Imaging

PHILADELPHIA — Screening patients scheduled to undergo carotid artery stenting by three-dimensional CT angiography led to a change in the planned procedure in 37% of patients in a pilot study with a total of 59 patients.

Screening with computed tomography angiography provides a standardized view of the patient's vascular anatomy and allows exclusion of patients who have clear anatomic contraindications, Dr. Mark C. Wyers said at the Vascular Annual Meeting, sponsored by the Society for Vascular Surgery.

Further study of this screening method is warranted to assess its impact on stroke rates and its cost effectiveness, added Dr. Wyers, a vascular surgeon at Dartmouth-Hitchcock Medical Center in Lebanon, N.H.

“We need to do a better job in selecting patients for carotid artery stenting in order to improve our results,” he said. The anatomic assessments that have been used until now, most often Doppler ultrasound or conventional arteriography, have not provided adequate guidance for patient selection.

The imaging method tested was an orthogonal three-dimensional reconstruction of angiography data collected by CT, using the technique developed for imaging abdominal aortic aneurysms. This imaging was used at the discretion of the carotid stenting operators at Dartmouth-Hitchcock on 59 patients during a 3-year period.

During the same time, another 51 patients underwent carotid artery stenting without first undergoing imaging by CT angiography.

Of the 59 patients reviewed with CT angiography, 37 were approved for carotid stenting. Another 15 of the imaged patients were judged unsuitable for stenting based on the anatomy of their carotid arteries and other vessels, and 5 were considered to have anatomy with borderline suitability. In four of those five borderline patients, the procedure was not attempted, and in one patient, it was attempted but failed.

The number of patients who underwent stenting in the entire series was small (37 who were screened and 51 who weren't screened, for a total group of 88 patients), which makes comparisons between the two subgroups difficult.

The technical success rate of carotid stenting was 100% in the patients who were screened and 98% in those who weren't. The rate of unplanned or nonstandard maneuvers during stenting was 5% (two patients) in the screened subgroup and 12% (six patients) among those who weren't screened.

Screening not only appeared to help operators anticipate potential problems, it also reduced the need to make treatment decisions on the fly and helped reduce the tendency of some physicians to forge ahead with stenting in patients who have suboptimal vascular anatomy, Dr. Wyers said.

A 3-D CT angiogram reveals a heavily diseased aortic arch and carotid artery. The technique may help in appropriate patient selection. Courtesy Dr. Mark C. Wyers

PHILADELPHIA — Screening patients scheduled to undergo carotid artery stenting by three-dimensional CT angiography led to a change in the planned procedure in 37% of patients in a pilot study with a total of 59 patients.

Screening with computed tomography angiography provides a standardized view of the patient's vascular anatomy and allows exclusion of patients who have clear anatomic contraindications, Dr. Mark C. Wyers said at the Vascular Annual Meeting, sponsored by the Society for Vascular Surgery.

Further study of this screening method is warranted to assess its impact on stroke rates and its cost effectiveness, added Dr. Wyers, a vascular surgeon at Dartmouth-Hitchcock Medical Center in Lebanon, N.H.

“We need to do a better job in selecting patients for carotid artery stenting in order to improve our results,” he said. The anatomic assessments that have been used until now, most often Doppler ultrasound or conventional arteriography, have not provided adequate guidance for patient selection.

The imaging method tested was an orthogonal three-dimensional reconstruction of angiography data collected by CT, using the technique developed for imaging abdominal aortic aneurysms. This imaging was used at the discretion of the carotid stenting operators at Dartmouth-Hitchcock on 59 patients during a 3-year period.

During the same time, another 51 patients underwent carotid artery stenting without first undergoing imaging by CT angiography.

Of the 59 patients reviewed with CT angiography, 37 were approved for carotid stenting. Another 15 of the imaged patients were judged unsuitable for stenting based on the anatomy of their carotid arteries and other vessels, and 5 were considered to have anatomy with borderline suitability. In four of those five borderline patients, the procedure was not attempted, and in one patient, it was attempted but failed.

The number of patients who underwent stenting in the entire series was small (37 who were screened and 51 who weren't screened, for a total group of 88 patients), which makes comparisons between the two subgroups difficult.

The technical success rate of carotid stenting was 100% in the patients who were screened and 98% in those who weren't. The rate of unplanned or nonstandard maneuvers during stenting was 5% (two patients) in the screened subgroup and 12% (six patients) among those who weren't screened.

Screening not only appeared to help operators anticipate potential problems, it also reduced the need to make treatment decisions on the fly and helped reduce the tendency of some physicians to forge ahead with stenting in patients who have suboptimal vascular anatomy, Dr. Wyers said.

A 3-D CT angiogram reveals a heavily diseased aortic arch and carotid artery. The technique may help in appropriate patient selection. Courtesy Dr. Mark C. Wyers

PHILADELPHIA — Screening patients scheduled to undergo carotid artery stenting by three-dimensional CT angiography led to a change in the planned procedure in 37% of patients in a pilot study with a total of 59 patients.

Screening with computed tomography angiography provides a standardized view of the patient's vascular anatomy and allows exclusion of patients who have clear anatomic contraindications, Dr. Mark C. Wyers said at the Vascular Annual Meeting, sponsored by the Society for Vascular Surgery.

Further study of this screening method is warranted to assess its impact on stroke rates and its cost effectiveness, added Dr. Wyers, a vascular surgeon at Dartmouth-Hitchcock Medical Center in Lebanon, N.H.

“We need to do a better job in selecting patients for carotid artery stenting in order to improve our results,” he said. The anatomic assessments that have been used until now, most often Doppler ultrasound or conventional arteriography, have not provided adequate guidance for patient selection.

The imaging method tested was an orthogonal three-dimensional reconstruction of angiography data collected by CT, using the technique developed for imaging abdominal aortic aneurysms. This imaging was used at the discretion of the carotid stenting operators at Dartmouth-Hitchcock on 59 patients during a 3-year period.

During the same time, another 51 patients underwent carotid artery stenting without first undergoing imaging by CT angiography.

Of the 59 patients reviewed with CT angiography, 37 were approved for carotid stenting. Another 15 of the imaged patients were judged unsuitable for stenting based on the anatomy of their carotid arteries and other vessels, and 5 were considered to have anatomy with borderline suitability. In four of those five borderline patients, the procedure was not attempted, and in one patient, it was attempted but failed.

The number of patients who underwent stenting in the entire series was small (37 who were screened and 51 who weren't screened, for a total group of 88 patients), which makes comparisons between the two subgroups difficult.

The technical success rate of carotid stenting was 100% in the patients who were screened and 98% in those who weren't. The rate of unplanned or nonstandard maneuvers during stenting was 5% (two patients) in the screened subgroup and 12% (six patients) among those who weren't screened.

Screening not only appeared to help operators anticipate potential problems, it also reduced the need to make treatment decisions on the fly and helped reduce the tendency of some physicians to forge ahead with stenting in patients who have suboptimal vascular anatomy, Dr. Wyers said.

A 3-D CT angiogram reveals a heavily diseased aortic arch and carotid artery. The technique may help in appropriate patient selection. Courtesy Dr. Mark C. Wyers

CHICAGO — The use of 64-slice computed tomography coronary angiography seems to render invasive angiography unnecessary in many intermediate-risk patients, Dr. Mark A. Peterman reported at the annual meeting of the Society for Cardiovascular Angiography and Interventions.

Dr. Peterman observed the first 100 consecutive patients referred for 64-slice CT angiography for the indications of chest pain or an abnormal stress test following the installation of the imaging system at Baylor University Medical Center, Dallas.

Of those referred patients, 85 were reclassified as low risk on the basis of normal CT scans in the curved reformat, maximum-intensity pixel, and 3-D reconstruction views, said Dr. Peterman, of the university.

During 6 months of follow-up, there have been no coronary events in this group.

In the remaining 15 patients, whose CT findings were abnormal or suspicious, invasive coronary angiography was ordered by their primary cardiologists a mean of 20 days after CT angiography. The correlation between CT and conventional angiography proved to be excellent.

Thus, CT coronary angiography could obviate the need for invasive angiography in a significant number of intermediate-risk patients, although the real-world experience documented in this study requires confirmation in a larger, controlled study with longer follow-up. A cost-effectiveness analysis would be a useful component of any such study, Dr. Peterman added.

CHICAGO — The use of 64-slice computed tomography coronary angiography seems to render invasive angiography unnecessary in many intermediate-risk patients, Dr. Mark A. Peterman reported at the annual meeting of the Society for Cardiovascular Angiography and Interventions.

Dr. Peterman observed the first 100 consecutive patients referred for 64-slice CT angiography for the indications of chest pain or an abnormal stress test following the installation of the imaging system at Baylor University Medical Center, Dallas.

Of those referred patients, 85 were reclassified as low risk on the basis of normal CT scans in the curved reformat, maximum-intensity pixel, and 3-D reconstruction views, said Dr. Peterman, of the university.

During 6 months of follow-up, there have been no coronary events in this group.

In the remaining 15 patients, whose CT findings were abnormal or suspicious, invasive coronary angiography was ordered by their primary cardiologists a mean of 20 days after CT angiography. The correlation between CT and conventional angiography proved to be excellent.

Thus, CT coronary angiography could obviate the need for invasive angiography in a significant number of intermediate-risk patients, although the real-world experience documented in this study requires confirmation in a larger, controlled study with longer follow-up. A cost-effectiveness analysis would be a useful component of any such study, Dr. Peterman added.

CHICAGO — The use of 64-slice computed tomography coronary angiography seems to render invasive angiography unnecessary in many intermediate-risk patients, Dr. Mark A. Peterman reported at the annual meeting of the Society for Cardiovascular Angiography and Interventions.

Dr. Peterman observed the first 100 consecutive patients referred for 64-slice CT angiography for the indications of chest pain or an abnormal stress test following the installation of the imaging system at Baylor University Medical Center, Dallas.

Of those referred patients, 85 were reclassified as low risk on the basis of normal CT scans in the curved reformat, maximum-intensity pixel, and 3-D reconstruction views, said Dr. Peterman, of the university.

During 6 months of follow-up, there have been no coronary events in this group.

In the remaining 15 patients, whose CT findings were abnormal or suspicious, invasive coronary angiography was ordered by their primary cardiologists a mean of 20 days after CT angiography. The correlation between CT and conventional angiography proved to be excellent.

Thus, CT coronary angiography could obviate the need for invasive angiography in a significant number of intermediate-risk patients, although the real-world experience documented in this study requires confirmation in a larger, controlled study with longer follow-up. A cost-effectiveness analysis would be a useful component of any such study, Dr. Peterman added.

SAN FRANCISCO — Multisection CT imaging affected surgical management in 12 of 40 patients undergoing repeat coronary artery bypass grafting and provided helpful information on 30 patients with acute aortic dissection, Dr. Chris Probst said at the annual meeting of the International Society for Minimally Invasive Cardiothoracic Surgery.

“In our clinic, we use it routinely for any patient” scheduled for reoperation after a previous coronary artery bypass graft (CABG), said Dr. Probst, of the department of cardiac surgery at the University of Bonn (Germany). “It is an excellent imaging modality for planning the optimal surgical strategy for reoperative patients, as well as for patients with aortic syndromes to prevent injury to the patient.”

In the group referred for repeat CABG, 99% of all grafts could be visualized by multisection CT, including 34 arterial and 69 vein grafts. Of these, multisection CT allowed assessment of the complete anatomical course of 33 arterial grafts (97%) and 67 vein grafts (97%).

The imaging showed that 83 grafts were patent and 20 were occluded, he said. Among the patent grafts, 12 (14%) showed nonstenotic soft plaques.

Adherence of the right ventricle to the sternum was seen in 10 patients. Four patients showed adherence of the left internal mammary artery graft; another four patients showed adherence of the saphenous vein graft. Extensive calcifications of the ascending aorta were seen in three patients.

In the 30 patients with acute Stanford type A dissections, the investigators used multisection CT preoperatively to visualize the aortic valve and coronary tree, achieving good pictures of the aortic valve and the proximal and medium segments of the coronary tree. In one 64-year-old patient, for example, it clearly showed that the aortic valve was not involved in the dissection.

Multisection CT may be an important alternative to catheter angiography, which can delay urgent surgery and may only partially provide the sophisticated preoperative evaluation needed for safe surgery, Dr. Probst said. Evaluation of the thoracic aorta, coronary arteries, and grafts, as well as the anatomical relationships of cardiac structures, informs the surgical management of these two groups of patients.

Dr. Probst has no financial relationships with companies that make multisection CT machines.

ECG-gated CT scans of a 64-year-old patient with type A dissection revealed that neither the aortic valve (left) nor the coronary arteries (right, showing left coronary artery) were involved in the dissection, thereby sparing the patient coronary catheterization that would have delayed surgery. Photos courtesy Dr. Chris Probst

SAN FRANCISCO — Multisection CT imaging affected surgical management in 12 of 40 patients undergoing repeat coronary artery bypass grafting and provided helpful information on 30 patients with acute aortic dissection, Dr. Chris Probst said at the annual meeting of the International Society for Minimally Invasive Cardiothoracic Surgery.

“In our clinic, we use it routinely for any patient” scheduled for reoperation after a previous coronary artery bypass graft (CABG), said Dr. Probst, of the department of cardiac surgery at the University of Bonn (Germany). “It is an excellent imaging modality for planning the optimal surgical strategy for reoperative patients, as well as for patients with aortic syndromes to prevent injury to the patient.”

In the group referred for repeat CABG, 99% of all grafts could be visualized by multisection CT, including 34 arterial and 69 vein grafts. Of these, multisection CT allowed assessment of the complete anatomical course of 33 arterial grafts (97%) and 67 vein grafts (97%).

The imaging showed that 83 grafts were patent and 20 were occluded, he said. Among the patent grafts, 12 (14%) showed nonstenotic soft plaques.

Adherence of the right ventricle to the sternum was seen in 10 patients. Four patients showed adherence of the left internal mammary artery graft; another four patients showed adherence of the saphenous vein graft. Extensive calcifications of the ascending aorta were seen in three patients.

In the 30 patients with acute Stanford type A dissections, the investigators used multisection CT preoperatively to visualize the aortic valve and coronary tree, achieving good pictures of the aortic valve and the proximal and medium segments of the coronary tree. In one 64-year-old patient, for example, it clearly showed that the aortic valve was not involved in the dissection.

Multisection CT may be an important alternative to catheter angiography, which can delay urgent surgery and may only partially provide the sophisticated preoperative evaluation needed for safe surgery, Dr. Probst said. Evaluation of the thoracic aorta, coronary arteries, and grafts, as well as the anatomical relationships of cardiac structures, informs the surgical management of these two groups of patients.

Dr. Probst has no financial relationships with companies that make multisection CT machines.

ECG-gated CT scans of a 64-year-old patient with type A dissection revealed that neither the aortic valve (left) nor the coronary arteries (right, showing left coronary artery) were involved in the dissection, thereby sparing the patient coronary catheterization that would have delayed surgery. Photos courtesy Dr. Chris Probst

SAN FRANCISCO — Multisection CT imaging affected surgical management in 12 of 40 patients undergoing repeat coronary artery bypass grafting and provided helpful information on 30 patients with acute aortic dissection, Dr. Chris Probst said at the annual meeting of the International Society for Minimally Invasive Cardiothoracic Surgery.

“In our clinic, we use it routinely for any patient” scheduled for reoperation after a previous coronary artery bypass graft (CABG), said Dr. Probst, of the department of cardiac surgery at the University of Bonn (Germany). “It is an excellent imaging modality for planning the optimal surgical strategy for reoperative patients, as well as for patients with aortic syndromes to prevent injury to the patient.”

In the group referred for repeat CABG, 99% of all grafts could be visualized by multisection CT, including 34 arterial and 69 vein grafts. Of these, multisection CT allowed assessment of the complete anatomical course of 33 arterial grafts (97%) and 67 vein grafts (97%).

The imaging showed that 83 grafts were patent and 20 were occluded, he said. Among the patent grafts, 12 (14%) showed nonstenotic soft plaques.

Adherence of the right ventricle to the sternum was seen in 10 patients. Four patients showed adherence of the left internal mammary artery graft; another four patients showed adherence of the saphenous vein graft. Extensive calcifications of the ascending aorta were seen in three patients.

In the 30 patients with acute Stanford type A dissections, the investigators used multisection CT preoperatively to visualize the aortic valve and coronary tree, achieving good pictures of the aortic valve and the proximal and medium segments of the coronary tree. In one 64-year-old patient, for example, it clearly showed that the aortic valve was not involved in the dissection.

Multisection CT may be an important alternative to catheter angiography, which can delay urgent surgery and may only partially provide the sophisticated preoperative evaluation needed for safe surgery, Dr. Probst said. Evaluation of the thoracic aorta, coronary arteries, and grafts, as well as the anatomical relationships of cardiac structures, informs the surgical management of these two groups of patients.

Dr. Probst has no financial relationships with companies that make multisection CT machines.

ECG-gated CT scans of a 64-year-old patient with type A dissection revealed that neither the aortic valve (left) nor the coronary arteries (right, showing left coronary artery) were involved in the dissection, thereby sparing the patient coronary catheterization that would have delayed surgery. Photos courtesy Dr. Chris Probst

CHICAGO — Intriguing invasive methods of identifying vulnerable coronary plaques include vaso vasorum imaging, intraarterial MRI, and several variants of optical coherence tomography, according to speakers at the annual meeting of the Society for Cardiovascular Angiography and Interventions.

▸ Vaso vasorum imaging. The vaso vasorum—the microcapillaries that form in the adventitia adjacent to atherosclerotic plaque in response to vascular injury—become more dense as inflammation due to macrophage activity increases. And this inflammation is a key factor in plaque rupture, said Dr. Stephane Carlier of Columbia University, New York.

He and his coworkers have developed an intravascular ultrasound-based technique that uses gas-filled microbubbles for contrast enhancement in order to assess vaso vasorum density and identify areas of intraplaque leakage or hemorrhage.

The hypothesis is that these findings will correlate with high likelihood of plaque rupture, said Dr. Carlier, who is also director of intravascular imaging and physiology at the Cardiovascular Research Foundation in New York.

▸ Intraarterial MRI. Conventional magnetic resonance imaging using a big external magnet isn't well suited for evaluating the composition of atheromatous plaques. Adequate resolution is difficult because the coronary arteries are small, are situated deep in the thorax, and move with respiration and systolic motion of the heart.

Intraarterial MRI is a novel imaging method that sidesteps these obstacles. There is no external magnet. Magnet and coil are incorporated within the probe, which also contains radiofrequency transmission and receiver units. Unlike conventional MRI, the intraarterial version doesn't provide pictures of the arteries in cross section; instead, it is designed specifically to analyze the lipid content within the arterial wall.

The current device is No. 6 French and deployed in a No. 8 French guiding catheter. A balloon is inflated to push the probe against an arterial plaque. Interrogation of the lesion takes about 25 seconds, according to Dr. Robert L. Wilensky, a cardiologist at the University of Pennsylvania, Philadelphia.

A 29-patient phase I study has been completed. A larger phase II international trial evaluating higher-risk patients will begin soon. Efforts are also underway to streamline the delivery catheter from No. 8 to No. 6 French, added Dr. Wilensky, who heads the scientific advisory board for TopSpin Medical, the Israeli company developing intraarterial MRI.

▸ Optical coherence tomography. This extremely high-resolution, broadband, light-based imaging method provides tremendous structural detail. With a theoretic resolution of 5–7 m and somewhat less in actual practice, optical coherence tomography (OCT) is well suited for in-depth morphologic evaluation of thin-capped fibroatheromas, the plaque type believed to be at greatest risk of rupture and resultant myocardial infarction, said Dr. Gregg W. Stone, professor of medicine at Columbia University and vice chairman of the Cardiovascular Research Foundation.

There is a daunting obstacle to commercial development of OCT, however: At present, the intravascular probe requires arterial occlusion, as do OCT's variants, including optical frequency domain imaging and polarization-sensitive OCT.

Optical frequency domain imaging “is basically OCT on steroids,” according to Dr. Stone. “It allows much, much faster acquisition rates. In fact, you can pull back at up to 12 mm/second, so you could image a whole coronary artery in 5 or 6 seconds and get incredibly high- resolution images.”

Polarization-sensitive OCT takes advantage of the birefringence of collagen fibers, enabling physicians to readily separate collagen from noncollagen tissues, said Dr. Stone.

CHICAGO — Intriguing invasive methods of identifying vulnerable coronary plaques include vaso vasorum imaging, intraarterial MRI, and several variants of optical coherence tomography, according to speakers at the annual meeting of the Society for Cardiovascular Angiography and Interventions.

▸ Vaso vasorum imaging. The vaso vasorum—the microcapillaries that form in the adventitia adjacent to atherosclerotic plaque in response to vascular injury—become more dense as inflammation due to macrophage activity increases. And this inflammation is a key factor in plaque rupture, said Dr. Stephane Carlier of Columbia University, New York.

He and his coworkers have developed an intravascular ultrasound-based technique that uses gas-filled microbubbles for contrast enhancement in order to assess vaso vasorum density and identify areas of intraplaque leakage or hemorrhage.

The hypothesis is that these findings will correlate with high likelihood of plaque rupture, said Dr. Carlier, who is also director of intravascular imaging and physiology at the Cardiovascular Research Foundation in New York.

▸ Intraarterial MRI. Conventional magnetic resonance imaging using a big external magnet isn't well suited for evaluating the composition of atheromatous plaques. Adequate resolution is difficult because the coronary arteries are small, are situated deep in the thorax, and move with respiration and systolic motion of the heart.

Intraarterial MRI is a novel imaging method that sidesteps these obstacles. There is no external magnet. Magnet and coil are incorporated within the probe, which also contains radiofrequency transmission and receiver units. Unlike conventional MRI, the intraarterial version doesn't provide pictures of the arteries in cross section; instead, it is designed specifically to analyze the lipid content within the arterial wall.

The current device is No. 6 French and deployed in a No. 8 French guiding catheter. A balloon is inflated to push the probe against an arterial plaque. Interrogation of the lesion takes about 25 seconds, according to Dr. Robert L. Wilensky, a cardiologist at the University of Pennsylvania, Philadelphia.

A 29-patient phase I study has been completed. A larger phase II international trial evaluating higher-risk patients will begin soon. Efforts are also underway to streamline the delivery catheter from No. 8 to No. 6 French, added Dr. Wilensky, who heads the scientific advisory board for TopSpin Medical, the Israeli company developing intraarterial MRI.

▸ Optical coherence tomography. This extremely high-resolution, broadband, light-based imaging method provides tremendous structural detail. With a theoretic resolution of 5–7 m and somewhat less in actual practice, optical coherence tomography (OCT) is well suited for in-depth morphologic evaluation of thin-capped fibroatheromas, the plaque type believed to be at greatest risk of rupture and resultant myocardial infarction, said Dr. Gregg W. Stone, professor of medicine at Columbia University and vice chairman of the Cardiovascular Research Foundation.

There is a daunting obstacle to commercial development of OCT, however: At present, the intravascular probe requires arterial occlusion, as do OCT's variants, including optical frequency domain imaging and polarization-sensitive OCT.

Optical frequency domain imaging “is basically OCT on steroids,” according to Dr. Stone. “It allows much, much faster acquisition rates. In fact, you can pull back at up to 12 mm/second, so you could image a whole coronary artery in 5 or 6 seconds and get incredibly high- resolution images.”

Polarization-sensitive OCT takes advantage of the birefringence of collagen fibers, enabling physicians to readily separate collagen from noncollagen tissues, said Dr. Stone.

CHICAGO — Intriguing invasive methods of identifying vulnerable coronary plaques include vaso vasorum imaging, intraarterial MRI, and several variants of optical coherence tomography, according to speakers at the annual meeting of the Society for Cardiovascular Angiography and Interventions.

▸ Vaso vasorum imaging. The vaso vasorum—the microcapillaries that form in the adventitia adjacent to atherosclerotic plaque in response to vascular injury—become more dense as inflammation due to macrophage activity increases. And this inflammation is a key factor in plaque rupture, said Dr. Stephane Carlier of Columbia University, New York.

He and his coworkers have developed an intravascular ultrasound-based technique that uses gas-filled microbubbles for contrast enhancement in order to assess vaso vasorum density and identify areas of intraplaque leakage or hemorrhage.

The hypothesis is that these findings will correlate with high likelihood of plaque rupture, said Dr. Carlier, who is also director of intravascular imaging and physiology at the Cardiovascular Research Foundation in New York.

▸ Intraarterial MRI. Conventional magnetic resonance imaging using a big external magnet isn't well suited for evaluating the composition of atheromatous plaques. Adequate resolution is difficult because the coronary arteries are small, are situated deep in the thorax, and move with respiration and systolic motion of the heart.

Intraarterial MRI is a novel imaging method that sidesteps these obstacles. There is no external magnet. Magnet and coil are incorporated within the probe, which also contains radiofrequency transmission and receiver units. Unlike conventional MRI, the intraarterial version doesn't provide pictures of the arteries in cross section; instead, it is designed specifically to analyze the lipid content within the arterial wall.

The current device is No. 6 French and deployed in a No. 8 French guiding catheter. A balloon is inflated to push the probe against an arterial plaque. Interrogation of the lesion takes about 25 seconds, according to Dr. Robert L. Wilensky, a cardiologist at the University of Pennsylvania, Philadelphia.

A 29-patient phase I study has been completed. A larger phase II international trial evaluating higher-risk patients will begin soon. Efforts are also underway to streamline the delivery catheter from No. 8 to No. 6 French, added Dr. Wilensky, who heads the scientific advisory board for TopSpin Medical, the Israeli company developing intraarterial MRI.

▸ Optical coherence tomography. This extremely high-resolution, broadband, light-based imaging method provides tremendous structural detail. With a theoretic resolution of 5–7 m and somewhat less in actual practice, optical coherence tomography (OCT) is well suited for in-depth morphologic evaluation of thin-capped fibroatheromas, the plaque type believed to be at greatest risk of rupture and resultant myocardial infarction, said Dr. Gregg W. Stone, professor of medicine at Columbia University and vice chairman of the Cardiovascular Research Foundation.

There is a daunting obstacle to commercial development of OCT, however: At present, the intravascular probe requires arterial occlusion, as do OCT's variants, including optical frequency domain imaging and polarization-sensitive OCT.

Optical frequency domain imaging “is basically OCT on steroids,” according to Dr. Stone. “It allows much, much faster acquisition rates. In fact, you can pull back at up to 12 mm/second, so you could image a whole coronary artery in 5 or 6 seconds and get incredibly high- resolution images.”

Polarization-sensitive OCT takes advantage of the birefringence of collagen fibers, enabling physicians to readily separate collagen from noncollagen tissues, said Dr. Stone.

CHICAGO — A furiously competitive race is on to develop new imaging methods capable of identifying vulnerable coronary plaques.

The first of these technologies to undergo evaluation in prospective clinical trials are virtual histology, palpography, thermography, and multislice computed tomography. They are being assessed in the pioneering Providing Regional Observations to Study Predictors of Events in the Coronary Tree (PROSPECT) study, a 700-patient international trial whose initial enrollees have completed their first year of follow-up, Dr. Gregg W. Stone said in his Hildner Lecture at the annual meeting of the Society for Cardiovascular Angiography and Interventions.

But PROSPECT is only the beginning. At least 14 different noninvasive and 28 catheter-based invasive diagnostic techniques aimed at detecting vulnerable plaques are in development, according to Dr. Stone, professor of medicine at Columbia University and vice chairman of the Cardiovascular Research Foundation, New York.

The goal of this effort is to identify asymptomatic coronary lesions that are active, inflamed, and prone to rupture so that in theory they can be preemptively treated before they cause an acute MI.

At this point, progress in vulnerable plaque imaging is well ahead of actual treatment. It is clear, however, that statins and lifestyle modification are not going to be sufficient. This was amply demonstrated in the Pravastatin Or Atorvastatin Evaluation and Infection Therapy (PROVE-IT) trial, in which patients with a history of acute coronary syndrome had a 22% coronary event rate over 2.5 years despite being on 80 mg/day of atorvastatin, Dr. Stone said.

Once it's established that vulnerable plaques can reliably be identified, more aggressive interventions might include drug-eluting stents for high-risk lesions, or catheter-delivered cryoplasty or photodynamic therapy for regional treatment, although all of this will require demonstration of clinical benefit in prospective trials, he continued.

Noninvasive imaging methods are most attractive as tools for population screening, since they in general pose less risk than invasive methods. That's not always true, though. Multislice CT, the noninvasive method that has garnered by far the greatest interest, entails significant exposure to radiation and nephrotoxic contrast media, Dr. Stone noted.

Invasive imaging techniques are more time consuming. But placing a catheter next to an atheroma yields a wealth of data on structure and function.

Invasive imaging methods fall into three broad categories: those that assess plaque morphology, such as virtual histology, optical coherence tomography, and vaso vasorum imaging; tools for evaluating plaque activity or composition, including thermography, spectroscopy, and intravascular MRI; and methods of studying a plaque's physical properties, such as palpography, which measures endothelial sheer stress at the plaque's cap.

Thermography relies on the observation that inflamed, unstable coronary plaques have a consistently slightly higher temperature than indolent ones.

Virtual histology utilizes intravascular ultrasound (IVUS) spectral analysis to assess plaque composition in four colors rather than the standard IVUS gray scale. This imaging tool, which has been validated in an ex vivo histology study using autopsy specimens, is commercially available from Volcano Corp. Virtual histology permits classification of coronary lesions into four types: fibrous, fibro-fatty, densely calcified, or—what is believed to be most worrisome—plaque having a necrotic core, explained Dr. Stone, who is principal investigator of the PROSPECT study.

PROSPECT, funded by Guidant Corp., is a natural history study in which plaque-imaging findings in patients with acute coronary syndrome will be prospectively correlated with future coronary events during 2–5 years of follow-up.

Dr. Stone is a consultant to Guidant, Volcano, and numerous other medical device manufacturers.

CHICAGO — A furiously competitive race is on to develop new imaging methods capable of identifying vulnerable coronary plaques.

The first of these technologies to undergo evaluation in prospective clinical trials are virtual histology, palpography, thermography, and multislice computed tomography. They are being assessed in the pioneering Providing Regional Observations to Study Predictors of Events in the Coronary Tree (PROSPECT) study, a 700-patient international trial whose initial enrollees have completed their first year of follow-up, Dr. Gregg W. Stone said in his Hildner Lecture at the annual meeting of the Society for Cardiovascular Angiography and Interventions.

But PROSPECT is only the beginning. At least 14 different noninvasive and 28 catheter-based invasive diagnostic techniques aimed at detecting vulnerable plaques are in development, according to Dr. Stone, professor of medicine at Columbia University and vice chairman of the Cardiovascular Research Foundation, New York.

The goal of this effort is to identify asymptomatic coronary lesions that are active, inflamed, and prone to rupture so that in theory they can be preemptively treated before they cause an acute MI.

At this point, progress in vulnerable plaque imaging is well ahead of actual treatment. It is clear, however, that statins and lifestyle modification are not going to be sufficient. This was amply demonstrated in the Pravastatin Or Atorvastatin Evaluation and Infection Therapy (PROVE-IT) trial, in which patients with a history of acute coronary syndrome had a 22% coronary event rate over 2.5 years despite being on 80 mg/day of atorvastatin, Dr. Stone said.

Once it's established that vulnerable plaques can reliably be identified, more aggressive interventions might include drug-eluting stents for high-risk lesions, or catheter-delivered cryoplasty or photodynamic therapy for regional treatment, although all of this will require demonstration of clinical benefit in prospective trials, he continued.

Noninvasive imaging methods are most attractive as tools for population screening, since they in general pose less risk than invasive methods. That's not always true, though. Multislice CT, the noninvasive method that has garnered by far the greatest interest, entails significant exposure to radiation and nephrotoxic contrast media, Dr. Stone noted.

Invasive imaging techniques are more time consuming. But placing a catheter next to an atheroma yields a wealth of data on structure and function.

Invasive imaging methods fall into three broad categories: those that assess plaque morphology, such as virtual histology, optical coherence tomography, and vaso vasorum imaging; tools for evaluating plaque activity or composition, including thermography, spectroscopy, and intravascular MRI; and methods of studying a plaque's physical properties, such as palpography, which measures endothelial sheer stress at the plaque's cap.

Thermography relies on the observation that inflamed, unstable coronary plaques have a consistently slightly higher temperature than indolent ones.

Virtual histology utilizes intravascular ultrasound (IVUS) spectral analysis to assess plaque composition in four colors rather than the standard IVUS gray scale. This imaging tool, which has been validated in an ex vivo histology study using autopsy specimens, is commercially available from Volcano Corp. Virtual histology permits classification of coronary lesions into four types: fibrous, fibro-fatty, densely calcified, or—what is believed to be most worrisome—plaque having a necrotic core, explained Dr. Stone, who is principal investigator of the PROSPECT study.

PROSPECT, funded by Guidant Corp., is a natural history study in which plaque-imaging findings in patients with acute coronary syndrome will be prospectively correlated with future coronary events during 2–5 years of follow-up.

Dr. Stone is a consultant to Guidant, Volcano, and numerous other medical device manufacturers.

CHICAGO — A furiously competitive race is on to develop new imaging methods capable of identifying vulnerable coronary plaques.

The first of these technologies to undergo evaluation in prospective clinical trials are virtual histology, palpography, thermography, and multislice computed tomography. They are being assessed in the pioneering Providing Regional Observations to Study Predictors of Events in the Coronary Tree (PROSPECT) study, a 700-patient international trial whose initial enrollees have completed their first year of follow-up, Dr. Gregg W. Stone said in his Hildner Lecture at the annual meeting of the Society for Cardiovascular Angiography and Interventions.

But PROSPECT is only the beginning. At least 14 different noninvasive and 28 catheter-based invasive diagnostic techniques aimed at detecting vulnerable plaques are in development, according to Dr. Stone, professor of medicine at Columbia University and vice chairman of the Cardiovascular Research Foundation, New York.

The goal of this effort is to identify asymptomatic coronary lesions that are active, inflamed, and prone to rupture so that in theory they can be preemptively treated before they cause an acute MI.

At this point, progress in vulnerable plaque imaging is well ahead of actual treatment. It is clear, however, that statins and lifestyle modification are not going to be sufficient. This was amply demonstrated in the Pravastatin Or Atorvastatin Evaluation and Infection Therapy (PROVE-IT) trial, in which patients with a history of acute coronary syndrome had a 22% coronary event rate over 2.5 years despite being on 80 mg/day of atorvastatin, Dr. Stone said.

Once it's established that vulnerable plaques can reliably be identified, more aggressive interventions might include drug-eluting stents for high-risk lesions, or catheter-delivered cryoplasty or photodynamic therapy for regional treatment, although all of this will require demonstration of clinical benefit in prospective trials, he continued.

Noninvasive imaging methods are most attractive as tools for population screening, since they in general pose less risk than invasive methods. That's not always true, though. Multislice CT, the noninvasive method that has garnered by far the greatest interest, entails significant exposure to radiation and nephrotoxic contrast media, Dr. Stone noted.

Invasive imaging techniques are more time consuming. But placing a catheter next to an atheroma yields a wealth of data on structure and function.

Invasive imaging methods fall into three broad categories: those that assess plaque morphology, such as virtual histology, optical coherence tomography, and vaso vasorum imaging; tools for evaluating plaque activity or composition, including thermography, spectroscopy, and intravascular MRI; and methods of studying a plaque's physical properties, such as palpography, which measures endothelial sheer stress at the plaque's cap.

Thermography relies on the observation that inflamed, unstable coronary plaques have a consistently slightly higher temperature than indolent ones.

Virtual histology utilizes intravascular ultrasound (IVUS) spectral analysis to assess plaque composition in four colors rather than the standard IVUS gray scale. This imaging tool, which has been validated in an ex vivo histology study using autopsy specimens, is commercially available from Volcano Corp. Virtual histology permits classification of coronary lesions into four types: fibrous, fibro-fatty, densely calcified, or—what is believed to be most worrisome—plaque having a necrotic core, explained Dr. Stone, who is principal investigator of the PROSPECT study.

PROSPECT, funded by Guidant Corp., is a natural history study in which plaque-imaging findings in patients with acute coronary syndrome will be prospectively correlated with future coronary events during 2–5 years of follow-up.

Dr. Stone is a consultant to Guidant, Volcano, and numerous other medical device manufacturers.