Extent of atherosclerosis and remodeling of the left main coronary artery determined by intravascular ultrasound

A Multi-Modality Image-Based FSI Modeling Approach for Prediction of Coronary Plaque Progression Using IVUS and OCT Data with Follow-Up

Medical image resolution has been a serious limitation in plaque progression research. A modeling approach combining intravascular ultrasound (IVUS) and optical coherence tomography (OCT) was introduced and patient follow-up IVUS and OCT data were acquired to construct 3D coronary models for plaque progression investigations. Baseline and follow-up in vivo IVUS and OCT coronary plaque data were acquired from one patient with 105 matched slices selected for model construction. 3D FSI models based on IVUS and OCT data (denoted as IVUS+OCT model) were constructed to obtain stress/strain and wall shear stress (WSS) for plaque progression prediction. IVUS-based IVUS50 and IVUS200 models were constructed for comparison with cap thickness set as 50 and 200 microns, respectively. Lumen area increase (LAI), plaque area increase (PAI) and plaque burden increase (PBI) were chosen to measure plaque progression. The least squares support vector machine method was employed for plaque progression prediction using 19 risk factors. For IVUS+OCT model with LAI, PAI and PBI, the best single predictor was plaque strain, local plaque stress, and minimal cap thickness, with prediction accuracy as 0.766, 0.838 and 0.890, respectively; The prediction accuracy using best combinations of 19 factors was 0.911, 0.881 and 0.905, respectively. Compared to IVUS+OCT model, IVUS50 and IVUS200 models had errors ranging from 1% to 66.5% in quantifying cap thickness, stress, strain and prediction accuracies. WSS showed relatively lower prediction accuracy compared to other predictors in all 9 prediction studies.

Intravascular Ultrasonic Imaging of Coronary Arterial Remodeling in Heart Transplant Recipients

The purpose of this study was to evaluate long-term changes of transplant coronary arteries, including vessel, plaque, and lumen areas. There are limited long-term data on vessel remodeling after heart transplantation. We analyzed serial intravascular ultrasound images of the left anterior descending coronary artery (LAD) in 54 heart transplantation recipients. Nine patients (16.7%) had a history of rejection. Proximal left anterior descending artery segments were matched among time points, a ≥20-mm long segment was analyzed every 1 mm, and results were normalized for analysis length and reported as mm(3)/mm. During follow-up, vessel area decreased (-0.48 ± 1.3 mm(3)/mm/year), and plaque area did not change (-0.01 ± 0.47 mm(3)/mm/year). As a result, lumen area decreased (-0.52 ± 1.34 mm(3)/mm/year). The change in mean lumen area was well correlated to the change in mean vessel area (r = 0.94, p <0.01) but not to the change in mean plaque area (r = -0.27, p = 0.05). In conclusion, lumen loss occurred during long-term follow-up of patients who underwent heart transplantation, primarily secondary to negative remodeling (decrease in vessel dimensions).

[Progression and regression of atherosclerotic plaques. New results based on intracoronary ultrasound]

Intravascular ultrasound has been established as the gold standard for analyzing alterations in coronary artery atherosclerosis during monitoring investigations. Cross-sectional imaging can be used to visualize the area of the lumen and the vessel size and the plaque size as the difference between them. New technology allows the 3-D reconstruction of the volume for prespecified vessel segments using specific algorithms. Investigations on the natural course demonstrated predominantly progression. Even regression of coronary atherosclerosis can be visualized and quantified. Regression can only be expected when the level of low-density lipoprotein (LDL) cholesterol is below the critical level of 75 mg/dl. Prospective randomized studies with highly effective statins showed that regression occurred in up to two thirds of patients when LDL cholesterol was below a cut-off of 78 mg/dl and was, therefore, very close to the threshold, which was calculated based on investigations of the natural course. Although the absolute values for plaque volume are in the range of 1 % over 1-2 years, it must be taken into consideration that coronary artery diseases are chronic diseases and a 1 % change per year will correspond to an enormous effect on plaque growth of coronary vessels. The great success of statins in reducing cardiovascular events is due to the possibility for reduction of progression and induction of regression. New developments in medication will be measured against the effectiveness of statins.

Intravascular Ultrasound for the Diagnosis and Treatment of Left Main Coronary Artery Disease

Limitations of angiography for assessment of coronary artery disease are well-known, but are more evident and relevant in the left main coronary artery (LMCA) segment given the amount of myocardium this vessel subtends and the risks associated with the presence of atherosclerosis and subsequent intervention. Intravascular ultrasound (IVUS) characterizes the severity of luminal narrowing, plaque morphology, and plaque extension into the distal bifurcation. Once the indication for percutaneous intervention (PCI) is established, information provided by IVUS is crucial to plan treatment and optimize results. IVUS-guided PCI with drug-eluting stents improves clinical outcomes, particularly in patients with distal left main disease.

Invasive assessment modalities of unprotected left main stenosis

Among all coronary lesions, the decision-making process for the treatment of unprotected left main (ULM) stem lesions is still challenging. Indeed, the optimal therapeutic strategy for patients with ULM disease remains controversial: coronary artery bypass grafting was established as the gold standard, but it is without doubt that percutaneous coronary intervention (PCI) performed by experienced operators achieves good results at long term follow up, especially in cases where the ostium and/or shaft of ULM are treated. Thanks to the widespread use of invasive assessment of atherothrombotic ULM stenosis, improved selection of PCI cases and techniques of stenting, better outcomes are now possible. This review seeks to define the place of PCI in ULM disease by describing the different modalities of ULM stenosis assessment.

Prospective application of pre-defined intravascular ultrasound criteria for assessment of intermediate left main coronary artery lesions results from the multicenter LITRO study

OBJECTIVES

This study is a prospective validation of 6 mm(2) as a minimum lumen area (MLA) cutoff value for revascularization of left main coronary artery (LMCA) lesions.

BACKGROUND

Lesions involving the LMCA are prognostically relevant. Angiography has important limitations in the evaluation of LMCA lesions with intermediate severity. An MLA of 6 mm(2) assessed by intravascular ultrasound has been proposed as a cutoff value to determine lesion severity, but there are no large studies evaluating the prospective application and safety of this approach.

METHODS

We have designed a multicenter, prospective study. Consecutive patients with intermediate lesions in unprotected LMCA were evaluated with intravascular ultrasound. An MLA <6 mm(2) was used as criterion for revascularization.

RESULTS

A total of 354 patients were included in 22 centers. LMCA revascularization was performed in 90.5% (152 of 168) of patients with an MLA <6 mm(2) and was deferred in 96% (179 of 186) of patients with an MLA of 6 mm(2) or more. A large scatter was observed between both groups regarding angiographic parameters. In a 2-year follow-up period, cardiac death-free survival was 97.7% in the deferred group versus 94.5% in the revascularized group (p = 0.5), and event-free survival was 87.3% versus 80.6%, respectively (p = 0.3). In the 2-year period, only 8 (4.4%) patients in the deferred group required subsequent LMCA revascularization, none with an infarction.

CONCLUSIONS

Angiographic measurements are not reliable in the assessment of intermediate LMCA lesions. An MLA of 6 mm(2) or more is a safe value for deferring revascularization of the LMCA, given the application of the clinical and angiographic inclusion criteria used in this study.

Quantification of coronary arterial stenoses by multidetector CT angiography in comparison with conventional angiography methods, caveats, and implications

Multidetector computed tomography (MDCT) is a rapidly evolving technology for performing noninvasive coronary angiography. Despite good sensitivity and specificity for detecting significant coronary artery disease in patients, disagreement on individual coronary arterial stenosis severity is common between MDCT and the current gold standard, conventional angiography. The reasons for such disagreement are numerous, but are at least partly inherent to MDCT's modest spatial and temporal resolution at present. Less well acknowledged, however, is the fact that MDCT and conventional angiography are fundamentally different technologies, rendering good agreement on the degree of lumen narrowing rather unrealistic, given both of their respective limitations. Discrepant stenosis assessment by MDCT and conventional angiography receives remarkable attention, whereas its significance for patient outcome is less certain. On the other hand, the ability to noninvasively assess coronary arterial plaque characteristics and composition in addition to lumen obstruction shows strong promise for improved risk assessment and may at last enable us to move beyond mere coronary stenosis assessment for the management of patients with coronary artery disease.

Percutaneous coronary intervention for unprotected left main coronary artery stenosis

Hemodynamically significant left main coronary artery stenosis (LMCA) is found in around 4% of diagnostic coronary angiograms and is known as unprotected LMCA stenosis if the left coronary artery and left circumflex artery has no previous patent grafts. Previous randomized studies have demonstrated a significant reduction in mortality when revascularization by coronary artery bypass graft (CABG) surgery was undertaken compared with medical treatment. Therefore, current practice guidelines do not recommend percutaneous coronary intervention (PCI) for such a lesion because of the proven benefit of surgery and high rates of restenosis with the use of bare metal stents. However, with the advent of drug-eluting stents (DES), the long term outcomes of PCI with DES to treat unprotected LMCA stenoses have been acceptable. Therefore, apart from the current guidelines, PCI for treatment of unprotected LMCA stenosis is often undertaken in individuals who are at a very high risk of CABG or refuse to undergo a sternotomy. Future randomized studies comparing CABG vs PCI using DES for treatment of unprotected LMCA stenosis would be a great advance in clinical knowledge for the adoption of appropriate treatment.

Intravascular Ultrasound Classification of Plaque Distribution in Left Main Coronary Artery Bifurcations

Background— Angiographic classifications of the location and severity of disease in the main vessel and side branch of coronary artery bifurcations have been proposed and applied to distal left main coronary artery (LMCA) bifurcation.

Methods and Results— We reviewed 140 angiograms of distal LMCA and ostial left anterior descending (LAD) and left circumflex (LCX) artery lesions with preintervention intravascular ultrasound (IVUS) of both the LAD and LCX arteries as well as the LMCA. Of 140 patients, 92.9% had at least 1 cross section with ≥40% IVUS plaque burden versus 57.2% of patients with an angiographic diameter stenosis ≥50%. Contrary to angiographic classifications, IVUS showed that bifurcation disease was rarely focal and that both sides of the flow divider were always disease-free. Continuous plaque from the LMCA into the proximal LAD artery was seen in 90%, from the LMCA into the LCX artery in 66.4%, and from the LMCA into both the LAD and LCX arteries in 62%. Plaque localized to either the LAD or LCX ostium and not involving the distal LMCA was seen in only 9.3% of LAD arteries and 17.1% of LCX arteries. Plaque distribution was not influenced by the LAD/LCX angiographic angle, lesion severity, LMCA length, or remodeling. We proposed an IVUS classification for bifurcation lesions illustrating longitudinal and circumferential spatial plaque distribution.

Conclusions— Angiographic classification of LMCA bifurcation lesions is rarely accurate. IVUS shows that the carina is always spared and that the disease is diffuse rather than focal.

Clinical Trial Registration— URL: http://www.clinicaltrials.gov. Unique identifier: NCT00180466.

Coronary pressure measurement based decision making for percutaneous coronary intervention

The fractional flow reserve (FFR) is a simple, reliable, and reproducible physiologic index of lesion severity. In patients with intermediate stenosis, FFR≥0.75 can be used to safely defer percutaneous coronary intervention (PCI), and patients with FFR≥0.75 have a very low cardiac event rate. Coronary pressure measurement can determine which lesion should be treated with PCI in patients with tandem lesions, and PCI on the basis of FFR has been demonstrated to result in an acceptably low repeat PCI rate. FFR can identify patients with equivocal left main coronary artery disease who benefit from coronary bypass surgery. Coronary pressure measurement distinguishes patients with an abrupt pressure drop pattern from those with a gradual pressure drop pattern, and the former group of patients benefit from PCI. Coronary pressure measurement is clinically useful in evaluating sufficient recruitable coronary collateral blood flow for prevention of ischemia, which affects future cardiac events. FFR is useful for the prediction of restenosis after PCI. As an end-point of PCI, FFR ≥0.95 and ≥0.90 would be appropriate for coronary stenting and coronary angioplasty, respectively. In summary, if you encounter a coronary stenosis in doubt you should measure pressure rather than dilate it.

Intravascular ultrasound predictors of major adverse cardiac events in patients with unstable angina

BACKGROUND

Intravascular ultrasound (IVUS) predictors of native culprit lesion morphology for occurrence of major adverse cardiac events (MACE) have not been reported. Moreover, the published data on IVUS predictors of restenosis include patients with stable and unstable angina, although the development and progression of atherosclerosis related to unstable coronary syndrome is different from that of stable angina.

HYPOTHESIS

This study investigated whether IVUS-derived qualitative and quantitative parameters of native (preangioplastic) plaque morphologic features can predict major adverse cardiac events in patients with unstable angina.

METHODS

Clinical (age, gender, coronary risk factors), qualitative and quantitative angiographic (lesion localization, morphology, pre- and postangioplastic minimal lumen diameter, reference diameter, and percent diameter stenosis), and IVUS variables (soft/fibrocalcific plaque, calcification, presence of thrombus or plaque disruption, different types of arterial remodeling, pre- or postangioplastic minimal lumen, external elastic membrane and plaque cross-sectional area, and plaque burden of the target lesion and reference segments) were analyzed by regression analyses using the Cox model, assuming proportional hazards.

RESULTS

Of 60 consecutively enrolled patients, 21 suffered from MACE, while 39 remained event-free during the followup period. Multivariate regression analyses revealed that the presence of adaptive remodeling [p = 0.0177, risk ratio (RR) = 3.108, with 95% confidence interval (CI) = 1.371-8.289] and the preangioplastic lumen cross-sectional area (p = 0.0130, RR = 0.869, with 95% CI = 0.667-0.913) are independent predictors of MACE during follow-up, as is postangioplastic angiographic minimal lumen diameter (p = 0.0330, RR = 0.715 with 95% CI = 0.678-0.812).

CONCLUSIONS

Adaptive remodeling and preangioplastic lumen cross-sectional area determined by IVUS and postangioplastic minimal lumen diameter calculated by quantitative angiography are significant independent predictors of time-dependent MACE in patients with unstable angina.

Left main coronary artery stenosis: state-of-the-art

Patients with stenosis of the left main coronary artery present difficult challenges. The risks associated with this lesion have been known since the early days of angiography when patients were found to have increased mortality during follow-up. This information led to the general guidelines that surgical revascularization should be considered the treatment of choice in patients with significant left main coronary artery stenosis. Current advances in invasive cardiology have brought important information to the field. Intravascular ultrasound is now used routinely to evaluate angiographically indeterminate lesions with criteria now set forward as to what constitutes an indication for revascularization. Stents have even further dramatically changed the landscape. There are substantial issues, however, that need to addressed. These include the following: (1) the effect of specific lesion location on outcome - it is known that patients with distal bifurcation left main disease have worse outcome; (2) the potential for subacute thrombosis of the left main coronary artery; (3) the impact of left ventricular function and patient comorbidities irrespective of the degree and location of left main coronary artery stenosis; and (4) the risk-benefit ratio of stenting versus coronary artery bypass graft surgery. These issues are currently being addressed in two seminally important trials including the SYNTAX trial, which randomizes patients with left main and/or three-vessel disease to either coronary artery bypass graft surgery or a TAXUS drug-eluting stent. This trial is in the final stages of patient recruitment and will have important implications for the field. The other trial is the COMBAT trial, which is focused exclusively on left main coronary artery stenosis and randomizes patients with left main coronary artery disease either to a Sirolimus-eluting stent (Cypher, Johnson and Johnson Cordis, USA) or to coronary artery bypass graft surgery. The field of left main coronary artery disease continues to expand in terms of the evidence available for optimal patient evaluation and selection of treatment modalities.

The impact of cardiovascular risk factors on subclinical left main coronary artery disease: an intravascular ultrasound study

BACKGROUND

The impact of cardiovascular risk factors on subclinical but measurable left main coronary artery (LMCA) atherosclerosis is not well known.

METHODS

We analyzed 150 consecutive patients with first-time coronary artery disease presentation undergoing intervention of a left anterior descending coronary artery or left circumflex lesion with motorized intravascular ultrasound transducer pullback that included a nonstenotic LMCA. Framingham, PROCAM, and European SCORE risk assessments were determined in 107 patients <65 years of age (because the Framingham, PROCAM, and European SCORE studies excluded patients >65 years old). Intravascular ultrasound measurements were compared in patients with <10% vs 10% to 20% risk of events.

RESULTS

Plaque volumes were greater in patients with higher risk scores: P = .007 in patients with 10% to 20% PROCAM risk, P = .063 in patients with 10% to 20% Framingham risk, and P = .059 in patients with 10% to 20% SCORE risk (P = .059). The mean arc of LMCA calcium (12 degrees +/- 25 degrees overall) correlated with plaque volume (51 +/- 28 mm3, r = 0.30, P = .0001) and with the number of coronary risk factors (P = .048) and ranged from 0.28 degrees +/- 0.74 degrees in patients with 0 to 1 risk factors to 9.95 degrees +/- 21.55 degrees in patients with 2 to 4 risk factors to 19.38 degrees +/- 32.51 degrees in patients with 5 to 7 risk factors. Regression analysis showed obesity and age were the most important factors contributing to LMCA calcium.

CONCLUSION

Intravascular ultrasound measurable atherosclerosis in nonstenotic LMCA correlates with conventional primary coronary risk scores. Left main coronary artery calcium correlates both with LMCA plaque volume and risk factors. Thus, subclinical LMCA atherosclerosis may be a marker for events that are predicted by commonly used primary risk-assessment algorithms.

Association of coronary shear stress with endothelial function and vascular remodeling in patients with normal or mildly diseased coronary arteries

BACKGROUND

The relationship between coronary remodeling, shear stress and endothelial function remains unclear.

OBJECTIVE

The present study investigated the effects of mechanical factors on structure and function of epicardial coronary arteries.

METHODS

Patients (group 1: %area stenosis<40%, n=55; or group 2: %area stenosis>or=40%, n=17) with a discrete mildly stenotic lesion (%diameter stenosis<30%) underwent intravascular ultrasound examination of the left anterior descending coronary artery for determination of vessel area, lumen area, plaque area, cross-sectional areas at reference segments, and remodeling index (the ratio of vessel area at the culprit lesion to vessel area at the proximal reference site). Further, vascular reactivity was examined using intracoronary administration of acetylcholine, papaverine, and nitroglycerin.

RESULTS

Vessel area significantly correlated with plaque area in both groups (r=0.65, P<0.0001 and r=0.85, P<0.0001). Group 1 showed significantly greater acetylcholine-induced percentage changes in coronary blood flow (67+/-70 vs. 16+/-75%, P<0.05) and coronary artery diameter (-7+/-18 vs.-32+/-31%, P<0.01) and also significantly smaller coronary wall shear stress (65+/-27 vs. 81+/-32 dynes/cm, P<0.05) than group 2. The percentage increase in coronary blood flow induced by acetylcholine was significantly and positively correlated with remodeling index in group 1 (r=0.64, P<0.0001) but not in group 2 (r=-0.03, P=0.90) and was also significantly and positively correlated with coronary wall shear stress in group 1 (r=0.46, P<0.001) but not in group 2 (r=-0.33, P=0.19).

CONCLUSIONS

Endothelium-dependent vasodilation in the resistance coronary artery correlates with remodeling via increased wall shear stress when target lesions %area stenosis is <40%.

Coronary pressure measurement to determine treatment strategy for equivocal left main coronary artery lesions

It is often hard to select a treatment strategy for equivocal left main coronary artery (LMCA) disease. We investigated the usefulness of coronary pressure (CP) measurement for determining the treatment strategy in intermediate LMCA disease. We measured CP in 15 consecutive patients with equivocal LMCA disease (age 67.6 +/- 7.5 years, 14 males). Myocardial fractional flow reserve (FFRmyo) was obtained as the ratio of CP distal to the lesion/aortic pressure under maximal coronary dilation. Patients with FFRmyo > or = 0.75 and <0.75 received medical therapy and coronary artery bypass grafting (CABG), respectively, and were followed up for 32.5 +/- 9.7 (20-47) months. Eight patients received medical therapy and 7 patients underwent CABG in accordance with the FFRmyo criteria noted above. FFRmyo of the LMCA was 0.91 +/- 0.01 and 0.61 +/- 0.03 in patients who received medical and surgical therapy, respectively. Neither reference vessel diameter, minimal lumen diameter, nor percent diameter stenosis was significantly different between patients who received medical and surgical therapy. During the follow-up period, no patients with medical therapy showed symptoms due to the LMCA lesion. Similarly, 5 of 7 patients with CABG showed improvement of symptoms and the remaining 2 patients were hospitalized with congestive heart failure. No cardiac death was recorded in the patients with medical or surgical therapy. In conclusion, the present results clearly demonstrated that CP is clinically useful for determining the treatment strategy for equivocal LMCA lesions but coronary angiography is not.

Atherosclerosis found on carotid ultrasonography is associated with atherosclerosis on coronary intravascular ultrasonography

OBJECTIVE

Little has been reported on the relationship between left main coronary artery atherosclerosis and carotid ultrasonographic results. We evaluated the association between carotid and coronary atherosclerosis assessed by coronary intravascular ultrasonography (IVUS) in 45 patients.

METHODS

We counted the number of plaques with intima-media thickness (IMT) greater than or equal to 1.1 mm and calculated a plaque score by summing all plaque thicknesses. With the use of IVUS, the percent plaque area was calculated at the proximal, middle, and distal sites of the left main coronary artery. The maximum percent plaque area and mean percent plaque area of the 3 sites were also calculated. Relationships among the degree of left main coronary artery atherosclerosis and carotid atherosclerosis and vascular risk factors were evaluated.

RESULTS

The mean percent plaque area and maximum percent plaque area were increased in men and in patients with hypertension compared with women and those without hypertension (P < .1). Both the average of the maximum common carotid IMT and plaque number were correlated with both the mean percent plaque area and maximum percent plaque area (P < .05). Men, the presence of hypertension, and the average of the maximum common carotid IMT were correlated with both the mean percent plaque area and maximum percent plaque area by multiple linear regression analysis (P < .05).

CONCLUSIONS

The average of the maximum common carotid IMT was significantly correlated with left main coronary artery atherosclerosis evaluated by IVUS.

Protein kinase C regulation of GABAA receptors

Pharmacological studies with drugs that activate or inhibit several protein kinase C (PKC) isozymes have identified the PKC family of serine-threonine kinases as important in the regulation of gamma-aminobutyric acid type A (GABA(A)) receptor function. PKC modulates GABA(A) receptor surface density, chloride conductance and receptor sensitivity to positive allosteric modulators such as neurosteroids, ethanol, benzodiazepines and barbiturates. Recent studies using PKC isozyme-selective reagents and gene-targeted mice have begun to identify critical roles for three isozymes, PKCbetaII, PKCvarepsilon and PKCgamma, in various aspects of GABA(A) receptor regulation. Progress in this field touches upon therapeutic areas that are of great clinical importance such as anxiety and addiction. Increased understanding of how PKC regulates GABA(A) receptors and which PKC isozymes are involved holds promise for development of new treatments for diverse neuropsychiatric disorders.

Intravascular ultrasound assessment of atherosclerosis

Atherosclerosis imaging has taken on increasing importance in the understanding of the natural history of coronary artery disease and the processes leading to luminal narrowing, as well as the assessment of disease burden and therapy efficacy. Intravascular ultrasound (IVUS) has emerged as the new gold standard for atherosclerosis imaging because it provides cross-sectional images of both the arterial wall and lumen with excellent resolution, reveals the diffuse nature of atherosclerosis and the involvement of reference segments, and takes into account vessel wall remodeling. In addition to its clinical indications, IVUS is now widely used as the primary efficacy assessment measure of several antiatherosclerotic approaches in randomized clinical trials. Advantages of IVUS include its ability to reveal antiatherosclerotic effects within a relatively short period of time and with a reasonable sample size, which is in contrast to trials assessing angiographic changes or clinical events. IVUS can also help to determine dose-response relationships in the development of novel pharmacologic agents. IVUS is currently the ideal imaging modality for clinical trials of atherosclerosis progression/regression.

Physiological and intravascular ultrasound assessment of an ambiguous left main coronary artery stenosis

The angiographic assessment of an ambiguous left main coronary artery (LMCA) stenosis is often difficult and not reliable. Intravascular ultrasound (IVUS) and fractional flow reserve (FFR) have improved the diagnostic utility of an ambiguous LMCA stenosis. The combined role of FFR and IVUS in patients with an ambiguous LMCA stenosis is discussed.

Coronary artery calcium and its relationship to coronary artery disease

Electron-beam computed tomography (EBCT) and the recent generation of multi-slice computed tomography scanners (MSCT) permit high-resolution imaging of the beating heart and the coronary arteries. The visualization of coronary calcium offers the opportunity to non-invasively obtain direct information on coronary anatomy and plaque burden. For clinical purposes, coronary calcium represents the presence of arteriosclerotic plaques. Coronary calcium is deposited in an actively regulated process related to lipid content of and apoptosis within coronary plaques. The amount of coronary calcium is related to the extent of coronary plaque disease, which has substantial diagnostic and prognostic implications. Visualization of coronary calcium by cardiac CT allows to non-invasively detect and localize coronary plaques and describe their distribution in the coronary tree. Approximately 50% to 70% of all plaques are calcified. Calcium cannot be used to reliably identify plaques at risk for developing complications such as rupture or erosion with ensuing thrombus formation. However, data are accumulating that indicate that calcium is an indicator of coronary arteriosclerotic disease activity. A scan negative for coronary calcium has a high negative predictive value indicating absence of stenotic coronary artery disease and an excellent short- to mid-term prognosis. Studies using serial CT scans indicate that the annual progression of coronary calcium varies between 30% to 50% in symptomatic or high-risk individuals and 0% to 20% in patients treated effectively with lipid-lowering medication. An increased rate of progression of coronary calcium seems to indicate a substantially increased risk for adverse cardiac events.

Angiographically silent left main disease detected by intravascular ultrasound: a marker for future adverse cardiac events

BACKGROUND

Concomitant moderate obstructive left main (LM) disease is associated with future cardiac events and poor prognosis in patients undergoing percutaneous intervention (PCI). Whether prognosis is similarly effected by LM disease not detected by angiography, but evident on intravascular ultrasound (IVUS) imaging, is not known. The purpose of this study was to evaluate the long-term prognosis of patients with angiographically insignificant LM coronary artery disease undergoing PCI.

METHODS AND RESULTS

One hundred and seven consecutive patients undergoing PCI with angiographically normal or mild LM disease had 2- and 3-dimensional IVUS imaging. IVUS images were digitized, and 3-dimensional reconstruction was performed. Percent diameter and area stenosis by angiography were 4.8% +/- 3.5% and 18.2% +/- 9.8%, respectively. IVUS mean luminal area and area stenosis were 17.9 +/- 5.6 mm2 and 30.2% +/- 14.7%, respectively. Long-term follow-up was available in 102 (95%) patients at a median of 29 (range 8-52) months. Major adverse cardiac events, defined as death (6), myocardial infarction (4), repeat PCI (13), or CABG (16), were associated with female sex (P =.04), diabetes (P =.02), angiographic minimum lumen diameter (P =.04), and IVUS minimum (P =.01) and mean (P =.01) lumen area. Multivariate predictors of late cardiac events were diabetes (hazard ratio 2.69, P =.014) and minimum lumen area by IVUS (hazard ratio 0.59, P =.015).

CONCLUSIONS

Despite being angiographically silent, LM disease detected by IVUS is an independent predictor of cardiac events and may serve as a marker for such events. These data extend the spectrum of LM disease severity and its relationship to cardiac prognosis in patients undergoing PCI.

Advancing age is associated with diminished vascular remodeling and impaired vasodilation in resistance coronary arteries

BACKGROUND

Compensatory enlargement of the coronary arterial wall has been described in the early stages of native atherosclerosis. However, little is known about the specific effect of aging on this adaptive process in atherosclerosis. The purpose of the current study was to characterize the effects of advancing age on vascular remodeling and endothelium-dependent and -independent coronary vasodilation in patients without coronary artery disease risk factors.

METHODS

Twenty-six patients without coronary risk factors and with normal and mildly diseased coronary arteries were studied. Vessel, lumen and atherosclerotic plaque areas were evaluated by intravascular ultrasound and coronary flow response was assessed using papaverine and acetylcholine in the left anterior descending coronary artery.

RESULTS

There was a weak but significant correlation between plaque area and age (r = 0.29, P<0.01). Vessel area was also weakly but significantly correlated with age (r = 0.22, P<0.05). However, lumen area had no correlation with age. Vessel area in the younger group (<50 years) and the older group (> or =50 years) increased 1.64 and 0.55 mm2 for every 1 mm2 increase in plaque area (r = 0.62, P<0.0001 and r = 0.39, P<0.05, respectively). With regard to vascular reactivity, there was an inverse correlation between the percentage increases in coronary blood flow (CBF) evoked by acetylcholine and aging (r = -0.49, P<0.05). The percentage increases in CBF evoked by papaverine also inversely correlated with aging (r=-0.53, P<0.01). However, the percentage changes in coronary artery diameter evoked with acetylcholine did not correlate with aging.

CONCLUSION

This study suggests that endothelium-dependent and -independent vasodilation of the resistance coronary artery are impaired with advancing age, which may be in association with attenuated coronary vascular remodeling with aging.

Correlation of coronary arterial remodeling determined by intravascular ultrasound with angiographic diameter reduction of 20% to 60%

Negative remodeling is commonly observed in stenotic coronary lesions. It is unknown whether negative remodeling is an early or late event. This study was designed to elucidate when negative remodeling occurs in the development of coronary stenosis. Remodeling was assessed by preintervention intravascular ultrasound in 104 native coronary lesions with intermediate stenosis (20% to 60% of diameter stenosis measured by quantitative coronary angiography). Positive remodeling was defined as lesion external elastic membrane (EEM) cross-sectional area (CSA) greater than the proximal reference, intermediate remodeling as lesion EEM CSA between those of the proximal and distal references, and negative remodeling as lesion EEM CSA less than the distal reference. Positive, intermediate, and negative remodeling were observed in 18%, 32%, and 50%, respectively, of lesions with intermediate stenosis. Lesions with negative and intermediate remodeling had more hard plaque compared with those with positive remodeling (79% vs 70% vs 42%, p = 0.02). Calcium was more frequent in lesions with negative and intermediate remodeling than in those with positive remodeling (52% vs 55% vs 16%, p = 0.01). Lesions with negative remodeling had smaller EEM CSA (11.5 +/- 5.2 vs. 13.7 +/- 3.4 vs 14.5 +/- 5.6 mm(2), p = 0.03) and less plaque (7.9 +/- 4.6 vs 10.8 +/- 3.4 vs 10.8 +/- 4.9 mm(2), p = 0.004) compared with positive and intermediate remodeling lesions, although lumen CSA (3.7 +/- 1.7 vs 2.8 +/- 0.8 vs 3.6 +/- 1.3 mm(2), p = 0.1) and area stenosis (57 +/- 15% vs 59 +/- 14% vs 56 +/- 10%, p = 0.7) were similar. Negative remodeling is frequently observed in lesions with intermediate stenosis. This suggests that negative remodeling occurs early in lesion formation.

Assessment of ambiguous coronary lesions by intravascular ultrasound

Until recently, coronary angiography has been regarded as the 'gold standard' for visualizing and quantifying coronary artery disease. Coronary angiography, however, is a luminographic technique revealing only the inner lumen of the coronary artery. In contrast, intravascular ultrasound investigations yield a detailed morphological description of the vessel wall and plaque characteristics. Based on these analyses, new insights into the pathogenesis of atherosclerotic coronary disease have evolved, including the remodeling phenomena. Thus, nowadays intravascular ultrasound can be regarded as the new 'gold standard' for the morphological assessment of lesion severity during cardiac catheterizations. Likewise, intracoronary Doppler and intracoronary pressure measurements have demonstrated their superiority in the functional assessment of coronary stenoses. Intravascular ultrasound investigations can be performed with high success and low complication rates. The present manuscript concentrates on the value of IVUS for the assessment of ambiguous lesions. Several forms of ambiguous lesions based on the angiographic appearance, i.e. intermediate lesion with undetermined stenosis severity, aneurysmatic widening of the coronary segment, ostial lesions, branching vessels, vessel tortuosity, main stem lesions, focal spasm, sites of plaque rupture, dissections, unclear haziness and contrast density changes are discussed and illustrated by respective angiographic and IVUS examples. Both the advantages and the limitations of angiographic and intravascular ultrasound examination are discussed in detail. In conclusion, additional intravascular ultrasound examination helps to diagnose accurately the underlying atherosclerotic disease, to define lesion characteristics and to optimize individual patient care and cost with respect to diagnostic catheterizations and coronary interventions.

Intracoronary ultrasound in acute coronary syndromes: from characterization of vulnerable plaques to guidance of percutaneous treatment of complex stenoses

Our current knowledge on the substrate and genesis of acute coronary syndromes (ACS) results from the integration of pathological, angiographic, and intracoronary imaging techniques. To summarize briefly the current paradigm, eight differentiated stages of development of atherosclerotic lesions are currently accepted, defined not only by the cellular elements involved, but also by the appearance of sudden alterations of plaque structure and coronary thrombosis. The latter constitutes not only the dominant substrate for the most devastating manifestations of coronary artery disease, but also accelerates plaque size at a faster pace than in earlier stages. The composition of atherosclerotic plaque varies significantly along the different evolutive stages, and thus includes cellular (macrophage, smooth muscle cells) and noncellular elements (glicosaminglycan or collagen-rich cellular matrix, extracellular lipid deposits, calcification, fresh, or organized thrombus) in a varying proportion. Furthermore, a dynamic process of vessel remodeling occurs along the atherosclerotic process, resulting, in most cases, in a protective mechanism against myocardial ischemia by preserving luminal dimensions during plaque enlargement. Intravascular ultrasound (IVUS) is one of the intracoronary imaging techniques that has contributed to the understanding of these changes in man. In addition, IVUS has the potential of being a useful clinical tool for predicting the chances of future acute coronary events by identifying vulnerable plaques, of characterizing which is the culprit lesion in ACS, and in guiding revascularization procedures in the treacherous field of thrombotic coronary syndromes. In this article, we review the current evidence on the potential of IVUS imaging for fulfilling these purposes.

Lumen loss in transplant coronary artery disease is a biphasic process involving early intimal thickening and late constrictive remodeling: results from a 5-year serial intravascular ultrasound study

BACKGROUND

Coronary artery disease is the major cause of late cardiac allograft failure. However, few data exist regarding the natural history of changes in intimal and external elastic membrane (EEM) areas after heart transplantation.

METHODS AND RESULTS

In 38 transplant recipients, serial intravascular ultrasound examinations were performed 3.7+/-2.2 weeks after transplantation and annually thereafter for 5 years. In 59 coronary arteries, we compared 135 matched segments among serial studies. In each segment, intravascular ultrasound images were digitized at 1-mm intervals, and mean values of EEM and lumen and intimal areas were analyzed. In the first year after transplantation, the intimal area increased significantly from 1.8+/-1.6 to 3.0+/-2.1 mm(2) (P<0.001). Subsequently, the annual increase in intimal area decreased. EEM area did not change during the first year; however, between years 1 and 3, significant expansion of EEM area occurred (15.4+/-4.6 to 17.2+/-5.4 mm(2), P<0.001). Thereafter, EEM area decreased significantly from 17.2+/-5.4 mm(2) (year 3) to 15.1+/-4.9 mm(2) (year 5, P=0.01). Different mechanisms of lumen loss were observed during 2 phases after transplantation: early lumen loss primarily caused by intimal thickening and late lumen loss caused by EEM area constriction.

CONCLUSIONS

This serial ultrasound study revealed that most of the intimal thickening occurred during the first year after heart transplantation. Changes in the EEM area showed a biphasic response, consisting of early expansion and late constriction. Thus, different mechanisms of lumen loss were observed during the early and late phases after transplantation.

Vascular remodeling in atherosclerotic coronary arteries is affected by plaque composition

BACKGROUND

Narrowing of lumen in atherosclerotic lesions is determined not solely by accumulation of plaque but also by constrictive or expansive vascular remodeling. Underlying mechanisms and determinants of these bidirectional processes are not known.

OBJECTIVES

To elucidate the response of vascular remodeling to progressive atherosclerosis by analyzing its potential association with composition of plaque.

METHODS

Seventy patients with 77 de-novo coronary artery lesions underwent intravascular ultrasound imaging before coronary intervention. Target lesions were defined as soft, fibrous/mixed, and calcified plaques. Quantitative measurements of area of lumen (A(L)), total area of vessel (A(TV)) and area of plaque (A(P) = A(TV)-A(L)) were performed at the lesion site and at the proximal and distal reference sites. Remodeling was determined by using a remodeling index [I(R) = (stenosis of A(TV)/mean reference A(TV)) x 100].

RESULTS

Overall vascular remodeling was balanced with a mean remodeling index of 100.2+/-19.3% and a high interlesion range (60.2-152.4%). The remodeling index for soft lesions was significantly higher than those for fibrous/mixed and calcified lesions (110+/-18.8 versus 96.2+/-14.4 and 85.9+/-15.1%, P < 0.01). Calcified lesions exhibited lower remodeling indexes than did uncalcified lesions (85.9+/-15.1 versus 104.6+/-18.4%, P < 0.01).

CONCLUSIONS

Processes involved in vascular remodeling are affected by composition of plaque insofar as there is a higher prevalence of constrictive remodeling among calcified plaques and a higher prevalence of expansive remodeling among soft lesions. These findings indicate that constrictive remodeling is a late manifestation in atherogenesis. Future studies are warranted in order to enhance the understanding of progression of atherosclerosis, and of mechanisms of vascular remodeling and their impacts on interventional therapy.

Coronary remodeling of proximal and distal stenotic atherosclerotic plaques within the same artery by intravascular ultrasound study

The aim of this intravascular ultrasound study was to compare the type and the degree of vessel remodeling in proximal and distal de novo lesions within the same coronary artery in patients with stable angina pectoris. Seventy-six de novo coronary artery lesions in 38 coronary arteries of 38 patients were imaged by intravascular ultrasound. The vessel area (VA) within the external elastic lamina and the lumen area (LA) were measured, and the wall area (VA-LA) was calculated at the lesion site, and the proximal and distal reference sites. The VA ratio was defined as (lesion VA/average of the proximal and distal reference VAs) to represent the degree of vessel remodeling. The proximal coronary segments showed compensatory enlargement more often (68% vs 29%, p < 0.01) than the distal segments, and the VA ratio at the lesion site was significantly larger (1.1 +/- 0.3 vs 1.0 +/- 0.2, p <0 .01) in proximal segments than in distal segments. The type of coronary remodeling was discordant in 61% and concordant in only 39% of coronary arteries between the proximal and distal segments. The type of coronary remodeling of proximal and distal coronary lesions was inhomogeneous, even within the same vessel. Proximal coronary segments showed more prominent compensatory enlargement than distal segments, which have a similar degree of luminal narrowings.

Arterial remodeling influences the development of intimal hyperplasia after stent implantation

OBJECTIVES

We examined whether preinterventional arterial remodeling influenced the interventional results after stenting.

BACKGROUND

Arterial remodeling is seen in atherosclerotic lesions, and it may play an important role in the early stage of atherosclerosis.

METHODS

We examined 113 lesions that underwent elective stenting using tubular slotted stents under intravascular ultrasound guidance. The lesions were divided into three groups--adequate, intermediate and inadequate remodeling group--according to preinterventional arterial remodeling. The patients were subjected to coronary angiography and intravascular ultrasound evaluation on average 6.4 months after stenting.

RESULTS

At baseline and immediately after stenting, there were no differences in quantitative angiographic analysis among remodeling groups. However, the plaque cross-sectional area (CSA) in the minimal lumen CSA at preintervention and intimal hyperplasia CSA at follow-up were significantly larger in the adequate remodeling group than in the inadequate remodeling group. The restenosis rate of stenting for the lesions with inadequate arterial remodeling was very low (9.4%). A significant positive correlation was found between preinterventional plaque CSA and intimal hyperplasia CSA at follow-up (r = 0.47, p < 0.0001). Moreover, remodeling index significantly correlated with relative intimal hyperplasia CSA (r = 0.28, p < 0.01).

CONCLUSIONS

Preinterventional arterial remodeling influenced the development of intimal hyperplasia after stenting.

Longitudinal study of vascular remodeling in coronary arteries after heart transplantation

Cross-sectional studies by intravascular ultrasound (IVUS) in heart transplant recipients have suggested that vascular remodeling occurs in coronary arteries years after transplant. However, no reports describe vascular remodeling in the same cohort of patients studied prospectively using morphometric analysis (10 evenly spaced images obtained from a slow pullback from the left anterior descending coronary artery). Morphometric analysis better reflects total vessel anatomy compared with previously reported site (2 to 3 images) analysis. We reviewed 20 patients studied by IVUS at 2 months, 1 year, 2 years, and 3 years after heart transplant.Over time, the coronary artery luminal area decreased from baseline level of 12.0 mm(2) to a 3-year mark of 9.7 mm(2) (p = 0.02). Vessel shrinkage was seen in 16/20 patients. After an initial rise in intimal parameters (maximal intimal thickness, intimal index, and plaque area) from baseline to 1 year, we found a significant decrease in intimal parameters between Year 1 and Year 3 after transplant. For example, plaque area decreased from 2.05 mm(2) at 1 year post-transplant to 1.48 mm(2) by 3 years post-transplant (p = 0.05). In a majority of heart transplant patients, early intimal thickening in the first year post-transplant is accompanied by constrictive remodeling. Over the subsequent 2 years, further constrictive remodeling is seen despite a decrease in intimal area.

Three-dimensional reconstruction of the coronary artery wall by image fusion of intravascular ultrasound and bi-plane angiography

BACKGROUND

Intravascular ultrasound (IVUS) is becoming increasingly accepted for assessing coronary anatomy. However, its utility in visualizing and quantifying coronary morphology has been limited by its 2D tomographic nature. This study presents a 3D reconstruction technique that accurately preserves 3D geometric information.

METHODS AND RESULTS

Images obtained from manual IVUS pullbacks and continuous bi-plane angiography were fused, using angiography to reconstruct the transducer trajectory and aid in solving for the correct rotational orientation. A novel 3D active surface method automatically identified the luminal and medial-adventitial borders which, when superimposed on the transducer trajectory, could be surface-rendered for visualization and morphometry. Segmentation agreed well with manual assessment, and 3D luminal shape matched that of angiography when projected to 2D.

CONCLUSIONS

We conclude that this method provides an accurate reconstruction of the vessel's anatomy, which accounts for the true curvature of the vessel.

Cholesterol-lowering treatment is associated with improvement in coronary vascular remodeling and endothelial function in patients with normal or mildly diseased coronary arteries

Coronary vascular remodeling and altered endothelial function have been described in the early stages of native atherosclerosis. The purpose of this study was to evaluate the association between cholesterol-lowering therapy and coronary vascular remodeling and endothelial function in patients with normal or mildly diseases coronary arteries. Patients (N=101) with normal or mildly diseased coronary arteries by coronary angiography underwent intravascular ultrasound examination of the left anterior descending coronary artery. Vessel and lumen area, atherosclerotic plaque area, and plaque morphology were evaluated. Vascular reactivity was examined with the use of intracoronary adenosine, acetylcholine, and nitroglycerin. Patients were divided into 3 groups based on the total cholesterol levels: group 1 (n=25), patients with a history of hypercholesterolemia adequately treated (total cholesterol <240 mg/dL); group 2 (n=26), patients with hypercholesterolemia not adequately controlled (total cholesterol >/=240 mg/dL); and group 3 (n=50), patients without hypercholesterolemia. Vessel area and lumen area were significantly greater in groups 1 and 3 than in group 2 (for respective values in groups 1, 2, and 3: vessel area 11.9+/-0.5, 10.6+/-0.4, and 11.8+/-0.4 mm(2), both P<0.05; lumen area 8.3+/-0.4, 6.9+/-0.3, and 8.9+/-0.3 mm(2), both P<0.01). However, plaque areas in groups 1 and 2 were similar. Furthermore, acetylcholine-induced percent increases in coronary blood flow were significantly greater in groups 1 and 3 than in group 2 (for respective values in groups 1, 2, and 3: 70.5+/-20.1%, 22.8+/-13.7%, and 68.6+/-14.8%, both P<0. 05). Cholesterol-lowering treatment is associated with an improvement in coronary lumen area that results not from a decrease in plaque area but from an increase in vessel area, reflecting vascular remodeling. Additionally, this adaptive process may occur in association with an improvement of endothelium-dependent vasodilation of the resistance coronary artery.

Preintervention lesion remodelling affects operative mechanisms of balloon optimised directional coronary atherectomy procedures: a volumetric study with three dimensional intravascular ultrasound

AIMS

To classify atherosclerotic coronary lesions on the basis of adequate or inadequate compensatory vascular enlargement, and to examine changes in lumen, plaque, and vessel volumes during balloon optimised directional coronary atherectomy procedures in relation to the state of adaptive remodelling before the intervention.

DESIGN

29 lesion segments in 29 patients were examined with intravascular ultrasound before and after successful balloon optimised directional coronary atherectomy procedures, and a validated volumetric intravascular ultrasound analysis was performed off-line to assess the atherosclerotic lesion remodelling and changes in plaque and vessel volumes that occurred during the intervention. Based on the intravascular ultrasound data, lesions were classified according to whether there was inadequate (group I) or adequate (group II) compensatory enlargement.

RESULTS

There was no significant difference in patient and lesion characteristics between groups I and II (n = 10 and 19), including lesion length and details of the intervention. Quantitative coronary angiographic data were similar for both groups. However, plaque and vessel volumes were significantly smaller in group I than in II. In group I, 9 (4)% (mean (SD)) of the plaque volume was ablated, while in group II 16 (11)% was ablated (p = 0.01). This difference was reflected in a lower lumen volume gain in group I than in group II (46 (18) mm(3) v 80 (49) mm(3) (p < 0.02)).

CONCLUSIONS

Preintervention lesion remodelling has an impact on the operative mechanisms of balloon optimised directional coronary atherectomy procedures. Plaque ablation was found to be particularly low in lesions with inadequate compensatory vascular enlargement.

Three-dimensional segmentation of luminal and adventitial borders in serial intravascular ultrasound images

Intravascular ultrasound (IVUS) provides exact anatomy of arteries, allowing accurate quantitative analysis. Automated segmentation of IVUS images is a prerequisite for routine quantitative analyses. We present a new three-dimensional (3D) segmentation technique, called active surface segmentation, which detects luminal and adventitial borders in IVUS pullback examinations of coronary arteries. The technique was validated against expert tracings by computing correlation coefficients (range 0.83-0.97) and William's index values (range 0.37-0.66). The technique was statistically accurate, robust to image artifacts, and capable of segmenting a large number of images rapidly. Active surface segmentation enabled geometrically accurate 3D reconstruction and visualization of coronary arteries and volumetric measurements.

Arterial remodeling in the left coronary system: the role of high-density lipoprotein cholesterol

OBJECTIVES

We sought to evaluate the plaque and patient variables related to arterial remodeling responses of early, de novo atherosclerotic lesions involving the left coronary artery.

BACKGROUND

Coronary artery remodeling is a lesion-specific process involving either enlargement or shrinkage of atherosclerotic coronary arteries. There are little histologic data available correlating plaque morphologic and patient clinical characteristics with the degree and type of arterial remodeling in early atherosclerosis.

METHODS

We studied 736 serial arterial sections from the left coronary system of 97 autopsy cases (mean age 33 +/- 11 years) by correlating the arterial remodeling response to plaque with demographic, serologic and histologic variables. Using the most proximal section as a reference, and considering the expected degree of internal elastic lamina tapering, remodeling was classified as positive (including neutral remodeling or compensatory enlargement) or negative.

RESULTS

Remodeling was classified as positive in 84.3% (compensatory in 30.6%) and negative in 15.7% of sections with an overall mean luminal stenosis of 10.4 +/- 9.9%. In the lesions with the greatest arterial cross-sectional narrowing from each case, compensatory enlargement was associated with higher high-density lipoprotein (HDL) cholesterol (59.4 +/- 27.2 mg/dl) compared with either neutral (49.3 +/- 15.5 mg/dl) or negative remodeling (30.4 +/- 5.2 mg/dl; p = 0.019). In subjects with advanced atherosclerosis (maximum American Heart Association histologic grade 5 atherosclerosis), there was a modest linear relationship between higher HDL cholesterol and the propensity for positive remodeling (r2 = 0.37; p = 0.025). On multivariate analysis, only HDL cholesterol was related to the arterial remodeling response.

CONCLUSIONS

Negative arterial remodeling occurs in early atherosclerosis. Higher HDL cholesterol may favor positive remodeling.

One-year follow-up after intravascular ultrasound assessment of moderate left main coronary artery disease in patients with ambiguous angiograms

OBJECTIVES

The purpose of this study was to correlate angiographic and intravascular ultrasound (IVUS) findings in left main coronary artery (LMCA) disease and identify the predictors of coronary events at one year in patients with LMCA stenoses.

BACKGROUND

Significant (> or =50% diameter stenosis [DS]) LMCA disease has a poor long-term prognosis.

METHODS

One hundred twenty-two patients who underwent angiographic and IVUS assessment of the severity of LMCA disease and who did not have subsequent catheter or surgical intervention were followed for one year. Standard clinical, angiographic and IVUS parameters were collected.

RESULTS

The quantitative coronary angiography (QCA) reference diameter (3.91 +/- 0.76 mm, mean +/- 1 SD) correlated moderately with IVUS (4.25 +/- 0.78 mm, r = 0.492, p = 0.0001). The lesion site minimum lumen diameter (MLD) (2.26 +/- 0.82 mm) by QCA correlated less well with IVUS (2.8 +/- 0.82 mm, r = 0.364, p = 0.0005). The QCA DS measured 42 +/- 16%. During the follow-up period, 4 patients died, none had a myocardial infarction, 3 underwent catheter-based LMCA intervention and 11 underwent bypass surgery. Univariate predictors of events (p < 0.05) were diabetes, presence of another lesion whether treated with catheter-based intervention or untreated with DS > 50% and IVUS reference plaque burden and lesion lumen area, maximum lumen diameter, MLD, plaque area and area stenosis. Using logistic regression analysis diabetes mellitus, an untreated vessel (with a DS > 50%) and IVUS MLD were independent predictors of cardiac events.

CONCLUSIONS

In selected patients assessed by IVUS, moderate LMCA disease had a one-year event rate of only 14%. Intravascular ultrasound MLD was the most important quantitative predictor of cardiac events. For any given MLD, the event rate was exaggerated in the presence of diabetes or another untreated lesion (>50% DS).

Clinical validation of intravascular ultrasound imaging for assessment of coronary stenosis severity: comparison with stress myocardial perfusion imaging

OBJECTIVES

To validate intravascular ultrasound (IVUS) measurements for differentiating functionally significant from nonsignificant coronary stenosis.

BACKGROUND

To date, there are no validated criteria for the definition of a flow-limiting coronary artery stenosis by IVUS.

METHODS

Preinterventional IVUS imaging (30-MHz imaging catheter) of 70 de novo coronary lesions was performed. The lesion lumen area and three IVUS-derived stenosis indixes comparing lesion lumen area with the lesion external elastic lamina (EEL) area, the mean reference lumen area and the mean reference EEL area were compared with the results of stress myocardial perfusion imaging.

RESULTS

The lesion lumen area and three IVUS-derived stenosis indexes showed sensitivities and specificities ranging between 80% and 90% using stress myocardial perfusion imaging as the gold standard. The lesion lumen area < or =4 mm2 is a simple and highly accurate criterion for significant coronary narrowing.

CONCLUSIONS

Quantitative IVUS indices can be reliably used for identifying significant epicardial coronary artery stenoses.

Quantification of intramural calcification in coronary intravascular ultrasound images with automated image analysis

BACKGROUND

Recent studies have documented the utility of intravascular ultrasonography in quantifying coronary morphologic characteristics and determining an appropriate intervention. Unfortunately, its potential for quantifying lesion calcification is limited by subjective evaluation and manual tracing. The aim of this study was to develop an objective automated method for quantifying calcification in intracoronary images with digital image analysis.

METHODS

Images of human coronary arteries acquired with a 30 MHz intracoronary ultrasound catheter were evaluated with digital image analysis and compared with manual tracings. Calcifications were automatically identified as highly echogenic regions detected by global thresholding within sectors of acoustic shadowing defined as regions devoid of texture.

RESULTS

The mean percentage agreement, sensitivity, and specificity of detecting calcification in 1-degree sectors of calcified vessels were 82%, 73%, and 87%, respectively. Similar results were obtained in noncalcified images.

CONCLUSION

The accuracy of this automated technique was comparable to interoperator and intraoperator variability in manually tracing calcification.

Atherosclerotic coronary lesions with inadequate compensatory enlargement have smaller plaque and vessel volumes: observations with three dimensional intravascular ultrasound in vivo

OBJECTIVE

To compare vessel, lumen, and plaque volumes in atherosclerotic coronary lesions with inadequate compensatory enlargement versus lesions with adequate compensatory enlargement.

DESIGN

35 angiographically significant coronary lesions were examined by intravascular ultrasound (IVUS) during motorised transducer pullback. Segments 20 mm in length were analysed using a validated automated three dimensional analysis system. IVUS was used to classify lesions as having inadequate (group I) or adequate (group II) compensatory enlargement.

RESULTS

There was no significant difference in quantitative angiographic measurements and the IVUS minimum lumen cross sectional area between groups I (n = 15) and II (n = 20). In group I, the vessel cross sectional area was 13.3 (3.0) mm2 at the lesion site and 14.4 (3.6) mm2 at the distal reference (p < 0.01), whereas in group II it was 17.5 (5.6) mm2 at the lesion site and 14.0 (6.0) mm2 at the distal reference (p < 0.001). Vessel and plaque cross sectional areas were significantly smaller in group I than in group II (13.3 (3.0) v 17.5 (5.6) mm2, p < 0.01; and 10.9 (2.8) v 15.2 (4.9) mm2; p < 0.005). Similarly, vessel and plaque volume were smaller in group I (291.0 (61.0) v 353.7 (110.0) mm3, and 177.5 (48.4) v 228.0 (92.8) mm3, p < 0.05 for both). Lumen areas and volumes were similar.

CONCLUSIONS

In lesions with inadequate compensatory enlargement, both vessel and plaque volume appear to be smaller than in lesions with adequate compensatory enlargement.

Successful directional atherectomy of de novo coronary lesions assessed with three-dimensional intravascular ultrasound and angiographic follow-up

Recent histopathologic and intravascular ultrasound (IVUS) data indicate that inadequate compensatory enlargement of atherosclerotic lesions contributes to the development of significant arterial stenoses. Such lesions may contain less plaque, which may have implications for atheroablative interventions. In this study, we compared lesions with (group A, n = 16) and without inadequate compensatory enlargement (group B, n = 30) as determined by IVUS. The acute results and the follow-up lumen dimensions of angiographically successful directional coronary atherectomy procedures were compared. Inadequate compensatory enlargement was considered present when the preintervention arterial cross-sectional area at the target lesion site was smaller than that at the (distal) reference site. Three-dimensional IVUS analysis and quantitative angiography were performed in 46 patients before and after intervention. IVUS measurements included the arterial, lumen, and plaque (arterial minus lumen) cross-sectional areas at the target lesion site (i.e., smallest lumen site) and the (distal) reference site. Angiographic follow-up was performed in 42 patients. Preintervention and postintervention angiographic measurements and IVUS lumen cross-sectional area measurements were similar in both groups. However, at follow-up, the angiographic minimum lumen and reference diameters were significantly smaller in group A compared with group B (1.71 +/- 0.47 mm vs 2.14 +/- 0.73 mm, p <0.03, and 2.97 +/- 0.29 mm vs 3.39 +/- 0.76 mm, p <0.02; group A vs B). The data of this observational study suggest that lesions with inadequate compensatory enlargement, as determined by IVUS before intervention, may have less favorable long-term lumen dimensions after directional coronary atherectomy procedures.