Limitations of angiography in the assessment of plaque distribution in coronary artery disease: a systematic study of target lesion eccentricity in 1446 lesions

The association of pericardial fat with coronary artery plaque index at MR imaging: The Multi-Ethnic Study of Atherosclerosis (MESA)

PURPOSE

To determine the relationship of pericardial fat, which secretes proinflammatory markers that have been implicated in coronary atherosclerosis, with atherosclerotic plaque in an asymptomatic population-based cohort.

MATERIALS AND METHODS

In this institutional review board-approved study, all participants supplied written informed consent. One hundred eighty-three participants (89 women, 94 men; mean age, 61 years ± 9 [standard deviation]) from the community-based Multi-Ethnic Study of Atherosclerosis (MESA) were included. The coronary artery eccentricity (ratio of maximal to minimal coronary artery wall thickness) was determined by using magnetic resonance (MR) imaging and served as an index of plaque burden. The pericardial fat volume was determined by using computed tomography. Linear regression coefficient analysis was used to correlate pericardial fat volume with coronary artery wall thickness and plaque eccentricity.

RESULTS

Pericardial fat volume correlated significantly with degree of plaque eccentricity (P < .05) in both men and women. After adjustments for body mass index (BMI) and waist circumference, traditional risk factors, C-reactive protein level, and coronary artery calcium content, the relationship between pericardial fat and plaque eccentricity remained significant in men (P < .01) but not in women. BMI and waist circumference correlated with degree of plaque eccentricity in the univariate model (P < .05) but not after adjustment for pericardial fat volume or traditional risk factors.

CONCLUSION

Pericardial fat volume, rather than BMI and waist circumference, was more strongly related to plaque eccentricity as a measure of coronary atherosclerotic plaque burden. The results support the proposed role of pericardial fat in association with atherosclerosis.

Plaque volume derived from three-dimensional reconstruction of coronary angiography predicts the fractional flow reserve

OBJECTIVES

To compare the data calculated from the three dimensional (3D) reconstruction of a coronary stenosis with the fractional flow reserve (FFR) values measured on the same coronary segment.

METHODS

Multiple projections of 22 patients (7 female, 15 male, age: 61 ± 9.73 years) were evaluated by the IC30 software of the Axiom Artis X-ray machine. 3D reconstruction was successfully carried out on 23 coronary arteries (14 LAD, 4 CX and 5 RCA).

RESULTS

Regression analysis demonstrated significant relationship between the cross-sectional area percentage stenosis (AS) calculated based on the 3D measurement and the FFR (r: -0.566, p: 0.008), as well as between the 3D derived plaque volume (PV) and the FFR (r: -0.501, p: 0.018). On the other hand, the diameter stenosis (DS) and the minimal lumen diameter (MLD) did not correlate with the FFR values. According to the Receiver Operating Characteristic (ROC) analysis the rank of the areas under the ROC curves (AUC) was the following: 1. PV (0.76), 2. AS (0.74), 3. DS (0.62), 4. MLA (0.55), and 5. MLD (0.51). The difference between the AUC of the PV and MLA was found to be significant (p=0.02). The best agreement with the FFR was found when the PV was >44% (sensitivity 66.67%, specificity 82.35%) and the 3D AS was >60% (sensitivity 100%, specificity 47%).

CONCLUSION

Besides the 3D AS the calculated PV characterizing the entire lesion is also an important predictor of the flow consequence of the stenosis.

Location of coronary culprit lesions at autopsy in 41 nondiabetic patients with acute myocardial infarction

BACKGROUND

Coronary artery disease and myocardial infarction (MI) are major causes of patient morbidity, hospital mortality, and out-of-hospital sudden death. The precise location of culprit lesions in acute MI at autopsy has not been reported.

OBJECTIVE

The purpose of this retrospective histopathologic autopsy study was to determine the distribution of coronary culprit lesions in acute fatal MI.

METHODS

Cross-sections of epicardial coronary arteries were evaluated microscopically. For each culprit lesion, its distance from the coronary ostium and its grade of luminal stenosis were recorded.

RESULTS

The study group included 41 nondiabetic patients (mean age of 65 years, 66% males) who underwent autopsy at Mayo Clinic Rochester (1994-2005). Culprit lesions occurred within the proximal 3.0 cm of the left anterior descending artery in 86% and the left circumflex artery in 100%. In contrast, culprit plaques within the right coronary artery (RCA) were distributed evenly throughout its length.

CONCLUSIONS

Among nondiabetic patients with acute fatal MI, culprit lesions exhibited proximal clustering in the left anterior descending artery and left circumflex artery, in contrast to more uniform distribution in the RCA. Thus, for the autopsy investigation of sudden death, evaluation for culprit lesions in the entire length of the RCA, not just its proximal region, is recommended.

The association of lesion eccentricity with plaque morphology and components in the superficial femoral artery: a high-spatial-resolution, multi-contrast weighted CMR study

BACKGROUND

Atherosclerotic plaque morphology and components are predictors of subsequent cardiovascular events. However, associations of plaque eccentricity with plaque morphology and plaque composition are unclear. This study investigated associations of plaque eccentricity with plaque components and morphology in the proximal superficial femoral artery using cardiovascular magnetic resonance (CMR).

METHODS

Twenty-eight subjects with an ankle-brachial index less than 1.00 were examined with 1.5 T high-spatial-resolution, multi-contrast weighted CMR. One hundred and eighty diseased locations of the proximal superficial femoral artery (about 40 mm) were analyzed. The eccentric lesion was defined as [(Maximum wall thickness- Minimum wall thickness)/Maximum wall thickness] >or= 0.5. The arterial morphology and plaque components were measured using semi-automatic image analysis software.

RESULTS

One hundred and fifteen locations were identified as eccentric lesions and sixty-five as concentric lesions. The eccentric lesions had larger wall but similar lumen areas, larger mean and maximum wall thicknesses, and more calcification and lipid rich necrotic core, compared to concentric lesions. For lesions with the same lumen area, the degree of eccentricity was associated with an increased wall area. Eccentricity (dichotomous as eccentric or concentric) was independently correlated with the prevalence of calcification (odds ratio 3.78, 95% CI 1.47-9.70) after adjustment for atherosclerotic risk factors and wall area.

CONCLUSIONS

Plaque eccentricity is associated with preserved lumen size and advanced plaque features such as larger plaque burden, more lipid content, and increased calcification in the superficial femoral artery.

Virtual histology intravascular ultrasound analysis of non-culprit attenuated plaques detected by grayscale intravascular ultrasound in patients with acute coronary syndromes

Noncalcific attenuated plaques identified by grayscale intravascular ultrasound (IVUS) are often seen in patients with acute coronary syndromes and have been associated with no reflow and creatine kinase-MB elevation after percutaneous coronary intervention. Histopathology has shown cholesterol clefts, microcalcification, or organized thrombus. One hundred twenty-four vessels in 64 patients with acute coronary syndromes from the PROSPECT trial were identified for inclusion in the present analysis. After excluding 4 vessels with severe calcification, 9 vessels with <40% plaque burden, and 3 vessels with too few (<3) virtual histology (VH)-IVUS frames for analysis, complete grayscale IVUS and VH-IVUS was available for 108 vessels in 64 patients that contained 39 VH-IVUS thin-capped fibroatheromas (VH-TCFA), 40 thick-capped fibroatheromas (VH-ThFA), and 33 pathologic intimal thickening but no fibrotic or fibrocalcific plaques. Overall, there were 47 grayscale IVUS attenuated plaques in 43 vessels. Compared to the minimum luminal sites of the remaining 65 vessels (controls), attenuated plaques contained larger necrotic core areas (1.5 +/- 0.9 vs 0.9 +/- 0.8 mm(2) in controls, p = 0.001). Fibroatheromas (VH-TCFA or VH-ThFA) were more common at the sites of attenuated plaques than at control sites (VH-TCFA 42.5% vs 29.2%, VH-ThFA 53.2% vs 23.1%, pathologic intimal thickening 4.3% vs 47.7%, p <0.0001). In conclusion, grayscale IVUS attenuated plaques are associated with a large amount of VH-IVUS necrotic core and are markers of the presence of fibroatheromas (VH-TCFA or VH-ThFA). This may explain the biologic instability of these lesions.

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.

The role of the out-of-operating room anesthesiologist in the care of the cardiac patient

Modern invasive cardiovascular procedures require patients to be both comfortable and cooperative. In addition, these procedures demand the complete attention of the attending cardiovascular specialist, and, to a large degree, the outcomes of these procedures depend on the amount of focus and concentration the cardiovascular specialist can give to performing the procedure itself. A team approach using the specialized skills of a cardiologist and an anesthesiologist frequently is required to optimize results. This article clearly delineates the procedures cardiologists perform that might involve anesthesiologists. Mutual knowledge, understanding, and respect are fundamental requirements for integration of cardiology and anesthesia services to optimize patient outcomes.

Vulnerable plaque: detection and management

Because most myocardial infarctions result from the rupture of a plaque that did not significantly compromise the coronary lumen before the event, experts widely accept that the morphology, composition, and degree of inflammation of a coronary atherosclerotic plaque is more important than the degree of luminal stenosis. Two depicting examples are the concentric, calcified lesion that shows significant luminal stenosis but is stable because of the stabilizing clasp of calcification. In contrast, a smaller but inflamed thin fibrous cap atheroma with a big lipid/necrotic core may rupture and cause an immediate fatal coronary occlusion.

Assessment of intermediate severity coronary lesions in the catheterization laboratory

The management of intermediate coronary lesions, defined by a diameter stenosis of 40% to 70%, continues to be a therapeutic dilemma for cardiologists. The 2-dimensional representation of the arterial lesion provided by angiography is limited in distinguishing intermediate lesions that require stenting from those that simply need appropriate medical therapy. In the era of drug-eluting stents, some might propose that stenting all intermediate coronary lesions is an appropriate solution. However, the possibility of procedural complications such as coronary dissection, no reflow phenomenon, in-stent restenosis, and stent thrombosis requires accurate stratification of patients with intermediate coronary lesions to appropriate therapy. Intravascular ultrasound (IVUS) and fractional flow reserve index (FFR) provide anatomic and functional information that can be used in the catheterization laboratory to designate patients to the most appropriate therapy. The purpose of this review is to discuss the critical information obtained from IVUS and FFR in guiding treatment of patients with intermediate coronary lesions. In addition, the importance of IVUS and FFR in the management of patients with serial stenosis, bifurcation lesions, left main disease, saphenous vein graft disease, and acute coronary syndrome will be discussed.

The eccentric lumenology

Coronary angiography has a poor predictive value for the detection of eccentric plaque morphology. Many reports have demonstrated discordance between the angiographic classification and the intravascular ultrasound (IVUS) classification. Although eccentricity is usually considered a dichotomous character, more than two-thirds of all coronary stenosis have some degree of eccentricity. The American College of Cardiology/American Heart Association (ACC/AHA) Task force included lesion eccentricity as a risk factor for moderate procedural success (60-85%) and moderate complications (type B). Although lesion eccentricity has been implicated as a risk factor for reduced short-term procedural results, current available data does not support the adverse impact of eccentricity on procedural success or restenosis. The present article reviews the incidence and the various clinical scenarios known to be associated with the eccentric lumenogram and the impact of coronary artery remodeling contributing to misinterpretation of disease eccentricity. Various therapeutic modalities with reference to eccentric lesions are also considered.

Coronary pressure measurement to identify the lesion requiring percutaneous coronary intervention in equivocal tandem lesions

OBJECTIVES

No reliable methods are available for determining application of percutaneous coronary intervention for treatment of equivocal tandem lesions. We investigated whether coronary pressure measurement is useful for determining the lesion that requires percutaneous coronary intervention in tandem lesions.

METHODS

We measured coronary pressure in 72 consecutive patients with tandem lesions. Myocardial fractional flow reserve (FFRmyo) was obtained as the ratio of coronary pressure distal to the lesion/aortic pressure under maximal hyperemia. If the FFRmyo across the tandem lesions was >or=0.75, we deferred percutaneous coronary intervention for the lesion. When the tandem lesions showed FFRmyo<0.75, percutaneous coronary intervention was performed on the lesion that showed angiographically higher stenosis. When FFRmyo was <0.75 after one-lesion percutaneous coronary intervention, this intervention was carried out on the remaining lesion.

RESULTS

We deferred percutaneous coronary intervention for 26 patients (36.1%), and performed percutaneous coronary intervention in 46 patients (63.8%). We performed percutaneous coronary intervention for one lesion in 19 patients (26.4%) and for both lesions in 27 patients (37.5%). Among patients in whom percutaneous coronary intervention was deferred, only two patients (7.7%) required target lesion revascularization during the follow-up period. This rate was not higher than that in the 46 patients who underwent percutaneous coronary intervention for one or two lesions (six patients, 13.0%). Similarly, the target lesion revascularization in lesions with initially deferred percutaneous coronary intervention (5.6%, 4/71 lesions) was not higher than that in lesions with percutaneous coronary intervention (15.1%, 11/73 lesions). Major cardiac events, cardiac death and acute myocardial infarction, did not occur in patients with deferred percutaneous coronary intervention and in those with percutaneous coronary intervention during the follow-up period.

CONCLUSION

Our results clearly showed that coronary pressure measurement was clinically useful for identifying equivocal tandem lesions requiring percutaneous coronary intervention.

Coronary atherosclerosis in end-stage idiopathic dilated cardiomyopathy: an innocent bystander?

AIMS

Coronary atherosclerosis is occasionally found in the hearts of patients diagnosed with idiopathic dilated cardiomyopathy (IDCM), who have undergone heart transplantation (HTx). This study investigates the pathology of coronary trees in IDCM patients and correlates the findings with risk factors for atherosclerosis.

METHODS AND RESULTS

The coronary trees of hearts excised at transplantation from 55 IDCM patients [43 males, mean (+/-SD) age at diagnosis and HTx: 37.4+/-13.4 and 42.1+/-14.6 years, respectively] underwent systematic pathological investigation. The inclusion criteria were: interval between the last pre-HTx angiography and the HTx of <10 years and the absence of ischaemic events in between; the absence of ventricular scars at pathological study; optimal pre-HTx medical treatment, and no ventricular assist devices. The median time between the pre-HTx angiography and the HTx was 13 months (range: 1-93). Fifteen of the 55 patients (27%) had critical plaques in at least one of the 70 segments of the epicardial coronary tree. A multivariate statistical analysis showed that male sex, age, and dyslipidaemia were independent predictors of critical atherosclerosis.

CONCLUSION

One-fourth of the patients with end-stage IDCM hearts excised at HTx (all with angiographically normal coronary arteries at first diagnosis) have bystander critical coronary atherosclerosis whose functional role (if any) deserves investigation.

Three-dimensional trajectory assessment of an IVUS transducer from single-plane cineangiograms: a phantom study

The recovery of the three-dimensional (3-D) path of the transducer used during an intravascular ultrasound (IVUS) examination is of primary importance to assess the exact 3-D shape of the vessel under study. Traditionally, the reconstruction is done by simply stacking the images during the pullback, or more recently using biplane angiography to recover the vessel curvature. In this paper, we explain, how single-plane angiography can be used with two projection models, to perform this task. Two types of projection geometry are analyzed: weak-perspective and full-perspective. In weak-perspective projection geometry, the catheter path can be reconstructed without prior transducer depth information. With full-perspective projection geometry, precise depth location of reference points are needed in order to minimize the error of the recovered transducer angle of incidence. The transducer angulation reconstruction is based on the foreshortening effect as seen from the X-ray images. By comparing the measured to the true transducer length, we are able to get its incidence angle. The transducer trajectory is reconstructed by stitching together the different estimated angulations obtained from each image in a cineangiogram sequence. The method is described and validated on two helical vessel phantoms, giving on average a reconstructed path that is less than 2 mm distant from the true path when using full-perspective projection.

Ultrasound imaging versus morphopathology in cardiovascular diseases. Coronary atherosclerotic plaque

This review article is aimed at comparing the results of histopathological and clinical imaging studies to assess coronary atherosclerotic plaques in humans. In particular, the gap between the two techniques and its effect on the understanding of the pathophysiological basis of coronary artery disease is critically discussed.

Routine intravascular ultrasound guidance of percutaneous coronary intervention

Intravascular ultrasound (IVUS) has played an integral role in the evolution of interventional cardiology. However, routine IVUS guidance of coronary stent implantation is not supported by a critical reappraisal of the available evidence. Although there is a trend toward a benefit with respect to target lumen revascularization favoring IVUS-guided coronary stent implantation, it is likely that this effect is driven by improved outcomes in small vessels, long coronary stenoses, and possibly saphenous vein graft interventions. No consistent trend in the incidence of death or myocardial infarction is apparent. Furthermore, the safety, efficacy, and effectiveness of IVUS should be taken into account when considering the goals, risks, benefits, and alternatives to such a treatment strategy.

Simulated characterization of atherosclerotic lesions in the coronary arteries by measurement of bioimpedance

FEM software was used to determine the feasibility of characterizing various types of atherosclerotic lesions in vivo. This was accomplished by simulating two electrodes as being attached to an angioplasty balloon in the coronary artery. The electrodes on the "balloon" touched and measured the simulated complex impedance of type III, IV, and Va and Vb lesions, as defined by the American Heart Association (AHA). Additionally, the effect of changes in morphology on the complex impedance was determined for type Va and Vb lesions. The simulations showed that the layer closest to the electrodes had the most significant effect on the measured complex impedance. As a consequence of these simulations, it appears plausible that electrodes could be placed in vivo to determine the characteristics and type of a given atherosclerotic lesion.

Comparison of the morphological changes of restenosis after the implantation of various types of stents in a swine model

BACKGROUND

Stent design causes the differences of restenosis rate, but the morphological differences after the various types of stent implantation have not been clarified.

DESIGN

Seven types of stents were implanted in pig coronary arteries to clarify how the mechanism of restenosis differs with coil stents and tube stents.

METHODS

The left anterior descending coronary arteries (LADs) of pigs were injured using coronary angioplasty balloons (diameter: 3.0 mm; length: 20 mm; balloon/artery ratio: 1 : 2). Fourteen days after the injury, four types of coil stents (Cordis, Wiktor, GR-I, and GR-II) and three types of tube stents (Palmaz-Schatz, gfx, and Multilink) were implanted, and the LADs were extracted 28 days after the implantation.

RESULTS

The proliferated neointima was eccentric in the coil stents and concentric in the tube stents. Although there was no significant difference in the area of neointima, the area of the lumen was significantly larger in the tube stents than in the coil stents ( < 0.01) because of the larger area of stent. Cells positive for anti-proliferating cell nuclear antigen antibody were mainly observed around the stent struts, and most of these cells were also positive for either anti-macrophage or anti-smooth muscle actin antibodies.

CONCLUSIONS

Compared to the coil stents, the tube stents induce less negative remodelling including stent recoil, resulting in a wider luminal area. In order to prevent restenosis, it is crucial to implant a stent that will cause less negative remodelling.

Impact of vessel curvature on the accuracy of three-dimensional intravascular ultrasound: validation by phantoms and coronary segments

BACKGROUND

Three-dimensional intravascular ultrasound (IVUS) is used for volumetric assessment of arteriosclerotic plaque burden and restenotic tissue at follow-up after coronary interventions. However, the accuracy of these measurements, especially in tortuous vessels, is unclear.

METHODS

A commercially available electrocardiogram (ECG)-gated 3-dimensional-IVUS system was tested in volume-validated straight and curved hydrocolloid phantoms and in volume-validated coronary specimens. Catheter withdrawal (30 MHz, 3.2F) was triggered using standardized ECG source with 0.2-mm step intervals per cardiac cycle simulation.

RESULTS

On the basis of automated phantom volume measurements, IVUS overestimated true phantom volume (relative error = [measured V - true V]/true V x 100) by a median of 0.9%, 0.25%, and 1.96% for straight, mildly curved, and severely curved segments, respectively. The true volume of the coronary specimens was overestimated by a median of 5.79%.

CONCLUSION

A median percentage deviation of 3-dimensional-IVUS-measured volumes from the true volumes of less than 10% in phantoms and coronary artery segments can be achieved.

Measurement of the ultrasonic properties of human coronary arteries in vitro with a 50-MHz acoustic microscope

Ultrasonic attenuation coefficient, wave propagation speed and integrated backscatter coefficient (IBC) of human coronary arteries were measured in vitro over the -6 dB frequency bandwidth (36 to 67 MHz) of a focused ultrasound transducer (50 MHz, focal distance 5.7 mm, f/number 1.7). Corrections were made for diffraction effects. Normal and diseased coronary artery sub-samples (N = 38) were obtained from 10 individuals at autopsy. The measured mean +/- SD of the wave speed (average over the entire vessel wall thickness) was 1581.04 +/- 53.88 m/s. At 50 MHz, the average attenuation coefficient was 4.99 +/- 1.33 dB/mm with a frequency dependence term of 1.55 +/- 0.18 determined over the 36- to 67-MHz frequency range. The IBC values were: 17.42 +/- 13.02 (sr.m)-1 for thickened intima, 11.35 +/- 6.54 (sr.m)-1 for fibrotic intima, 39.93 +/- 50.95 (sr.m)-1 for plaque, 4.26 +/- 2.34 (sr.m)-1 for foam cells, 5.12 +/- 5.85 (sr.m)-1 for media and 21.26 +/- 31.77 (sr.m)-1 for adventitia layers. The IBC results indicate the possibility for ultrasound characterization of human coronary artery wall tissue layer, including the situations of diseased arteries with the presence of thickened intima, fibrotic intima and plaque. The mean IBC normalized with respect to the mean IBC of the media layer seems promising for use as a parameter to differentiate a plaque or a thickened intima from a fibrotic intima.

Coronary disease morphology and distribution determined by quantitative angiography and intravascular ultrasound--re-evaluation in a cooperative multicenter intravascular ultrasound study (COMIUS)

Although previous studies have demonstrated that even quantitative coronary angiography (QCA) can not provide accurate disease morphology, there has not been a systematic comparison of disease morphology determined by QCA and intravascular ultrasound (IVUS), particularly in Japanese patients. Therefore, the present study prospectively examined patients in a multicenter cooperative study. A total of 491 coronary sites from 562 patients (446 men, 116 women; mean age, 64+/-11 years) who underwent coronary interventions were enrolled. The target lesions (>50% diameter stenosis) were evaluated pre-operatively by both QCA and IVUS operating at 30-40 MHz and the percent area stenosis, eccentricity index (EI) and lesion length were determined. The minimal (min) and maximal (max) distances from the center of the stenotic lesion to the outline of the vessel wall were measured, and the EI was calculated by the formula: [(max - min)/max]. By QCA, lesion length was determined by measuring the distance between the proximal and distal shoulders of the lesion. When the lesions were observed by IVUS with a motorized pull-back system, the length was calculated by multiplying the time for observation of the disease and 0.5 or 1 mm/s. Although the severity of the stenosis determined by QCA (86+/-10%, mean +/- SD) did not differ from that by IVUS (83+/-13%), there was no correlation between them (r=0.32, y=0.25x+65) and the correlation did not improve when lesions with remodeling, enlargement (n=176) or shrinkage (n=79) were omitted from the calculation. The EIs by QCA and IVUS were 0.51+/-0.26 and 0.52+/-0.22, respectively (NS), and there was no correlation between them (r=0.30, y=0.36x+33). However, when the lesions with remodeling were excluded, the correlation greatly improved (r=0.80, y=0.84x+10.6, p<0.05). Lesion length determined by QCA (12.4+/-6.1 mm) was significantly shorter than that by IVUS (16.3+/-8.9 mm, p<0.01). These results demonstrate that coronary angiography significantly misinterprets disease morphology in terms of severity, eccentricity and length, in part because of vessel remodeling that can be accurately determined only by IVUS.

Visual assessment of procedural results following treatment with Sr-90 beta-radiation for instent restenosis

BACKGROUND

Visual assessment (VA) of postprocedural % diameter stenosis (DS) is used routinely in clinical practice to determine the adequacy of coronary intervention. Although VA has been shown to underestimate final %DS after balloon angioplasty compared to quantitative coronary angiography (QCA), the impact of this effect on clinical outcomes following treatment with intracoronary radiation therapy (IRT) with Sr-90 for instent restenosis (ISR) is unknown.

METHODS

To determine the effect of VA on the rate of major adverse cardiac events (MACEs) after IRT for ISR, we compared the clinical outcomes of 102 consecutive patients based on postprocedural %DS by QCA vs. %DS by VA. MACE was defined as death, M1 or need for target vessel revascularization (TVR).

RESULTS

MACE rates for the 102 consecutive patients grouped according to postprocedural %DS by QCA and VA were compared. The mean %DS by QCA was 30.7%, while the mean %DS by VA was 12.5%. The mean %DS by VA across the QCA subgroups were 13.67%, 10.71% and 13.37%, respectively (P = .244). Fifty-two patients (51.0%) had %DS > 30% by QCA with the highest MACE percentage occurring in this subgroup.

CONCLUSION

VA underestimated the %DS compared to QCA, and it was associated with worse MACE following treatment with Sr-90 for ISR.

Targeting the adventitia with intracoronary beta-radiation: comparison of two dose prescriptions and the role of centering coronary arteries

PURPOSE

To compare by intravascular ultrasound (IVUS) the efficacy of delivering the prescribed dose to the adventitia between two commonly used dose prescriptions for intracoronary radiotherapy.

METHODS AND MATERIALS

In 59 human postangioplasty coronary vessels, one IVUS cross-section (1 mm thick) with the highest plaque burden was used for creating dose-volume histograms with different hypothetical positions of the source.

RESULTS

On average, prescription to 1 mm beyond lumen surface resulted in delivery of the prescribed dose (20 Gy +/- 20%) to a higher fraction of adventitial volume than with the prescription to 2 mm from the source, with source placed in vessel center, lumen center, or in the IVUS catheter position. Source placement in the lumen center resulted in a low dose heterogeneity to the adventitia and the least dose heterogeneity to the intima.

CONCLUSIONS

Prescription to 1 mm beyond lumen surface appeared more effective in delivering the prescribed dose to the adventitia than the American Association of Physicists in Medicine (AAPM) recommended prescription to 2 mm from the source center. Moreover, centering the source in the lumen provides the better balance of effective adventitial targeting and intimal dose homogeneity. Modification of the current AAPM recommendation for dose prescription for intracoronary radiotherapy should be considered.

Coronary intravascular ultrasound: implications for understanding the development and potential regression of atherosclerosis

The incremental value of intravascular ultrasound (IVUS), compared with angiographic analysis of coronary atherosclerosis, originates principally from 2 key features-its tomographic perspective and the ability to image coronary atheroma directly. Whereas angiography depicts the cross-sectional coronary anatomy as a planar silhouette of the lumen, ultrasound directly images the atheroma within the vessel wall, allowing measurement of atheroma size, distribution, and to some extent, composition. Although angiography remains the principal method to assess the extent of coronary atherosclerosis and to guide percutaneous coronary interventions, IVUS is rapidly altering conventional paradigms in the diagnosis and therapy of coronary artery disease. Thus, IVUS has become a vital adjunctive imaging modality for the aggressive coronary interventional cardiologist. As such, ultrasound has earned a role as a viable complementary technique relative to angiography, rather than an alternative to conventional angiographic methods. This article reviews the rationale, technical advantages and limitations, and interpretation of intravascular ultrasonography from the perspective of the general and invasive cardiologist. We emphasize the impact that IVUS studies have had on our understanding of the atherosclerotic coronary artery disease process, because these findings have important implications for all cardiologists. We then review several trials that are currently using intravascular ultrasonography for the study of coronary artery disease regression.

A novel realistic three-layer phantom for intravascular ultrasound imaging

Intravascular ultrasound (IVUS) is an imaging modality that experienced a tremendous development over the last 20 years. Phantoms for IVUS are rare and poorly documented. The aim of this paper is to propose an original IVUS phantom that has geometries and specular textures closer to those of coronary arteries than conventional tube-like phantoms. The proposed phantom has a three-layer aspect, reproducing the intima, media and adventitia that compose the arterial wall. It is made of an agar-based compound, with water, glycerol and cellulose particles. Fourteen phantoms were quantified using IVUS. Six phantoms were evaluated by both photomacroscopy and IVUS. There was an excellent correlation between phantom dimensions evaluated by photomacroscopy and the nominal values (mold dimensions). The IVUS quantification of the phantom was closely correlated to the measurements obtained by photomacroscopy. These results demonstrate that a multilayer phantom, with known and reproducible dimensions and with realistic geometric and echographic properties has been developed.

Increased heterogeneity of coronary perfusion in patients with early coronary atherosclerosis

BACKGROUND

In patients with typical angina but angiographically normal coronary arteries, abnormal vasomotor function is assumed to be a major underlying cause. However, data on this issue are conflicting, and recent studies suggest that fluid dynamic abnormalities exist in these patients. The aim of the study was to evaluate whether early stages of atherosclerosis are characterized by alterations of baseline coronary hemodynamics and endothelium-independent vasomotion. Besides established intracoronary Doppler parameters, heterogeneity of perfusion was assessed and related to early signs of atherosclerosis as determined by electron-beam computed tomography (EBCT).

METHODS

In 59 patients with typical angina and angiographically normal or near-normal coronary arteries, intracoronary Doppler measurements were performed in all 3 major coronary arteries. Baseline average peak velocity (bAPV) and hyperemic average peak velocity (hAPV) in response to intracoronary injection of adenosine were measured, and coronary flow velocity reserve (CFVR) was calculated. Heterogeneity was assessed as variability of bAPV, hAPV, and CFVR and was calculated as (STD/MEAN). 100. Doppler data were analyzed according to tertiles of the EBCT-derived Agatston calcium score (ie, score 0-1 [lowest tertile], 2-28 [medium tertile], and >28 [highest tertile]).

RESULTS

The mean EBCT-derived Agatston calcium score was 49 +/- 107. No coronary calcium was observed in 17 (29%) patients. The mean values of bAPV, hAPV, and CFVR were not different between the calcium score tertiles. However, patients in the highest tertile had a significantly increased variability index of bAPV (29.6% +/- 11.6%) compared with patients in the lowest tertile (13.4% +/- 7.3%, P <.0001). Variability of CFVR was also increased in these patients (15.5% +/- 11.7% vs 10.5% +/- 4.0%, P =.03).

CONCLUSION

These results indicate that early stages of atherosclerosis are characterized by microvascular abnormalities that do not uniformly affect the myocardium but are heterogeneous. The high variability of baseline coronary flow velocity with increasing coronary calcium suggests that in patients with early stages of atherosclerosis fluid dynamic effects may play a crucial role even in the absence of angiographically appreciable epicardial stenoses.

The use of mechanical devices as adjuncts to intracoronary stenting

A number of mechanical adjuncts to intracoronary stenting are now available to the interventional cardiologist. These devices have assisted in the development of a safer and more effective stenting practice. Intravascular ultrasound-guided stenting has been shown to reduce the rate of subacute thrombosis and subsequent restenosis. It allows a greater appreciation of lesion structure and severity so that an appropriate intervention strategy can be devised. Debulking techniques may allow the optimal deployment of stents so that restenosis is reduced; however, the results of large randomized studies are still awaited. The use of thrombectomy and distal embolization protection devices is emerging as a safer alternate to stenting alone in difficult patient subsets, such as those with thrombus-laden lesions and degenerated vein grafts. Doppler and pressure wires may be useful in determining optimal stent deployment and predict subsequent patient outcomes. An understanding of the indications and limitations of these devices is of increasing importance to the interventional cardiologist as the coming decade threatens to yield an impressive array of high-tech innovations.

Atheromas that cause fatal thrombosis are usually large and frequently accompanied by vessel enlargement

Several lines of clinical evidence show that AMI frequently occurs at sites with mild to moderate degree of coronary stenosis. The degree of luminal stenosis depends on plaque deposition and degree of vessel remodeling, features poorly assessed by coronary angiography. This postmortem study tested the hypothesis that the size of coronary atheroma and the type of remodeling distinguish culprit lesion responsible for fatal AMI from equi-stenotic nonculprit lesion in the same coronary tree. The main coronary branches from 36 consecutive patients with fatal AMI were studied. The culprit lesion (Group 1) and an equi-stenotic nonculprit segment (Group 2) obtained in measurements of another coronary branch from the same patient were compared. Morphometry and plaque composition was assessed in both groups. Compared to Group 2, Group 1 had larger areas of: plaque 9.6 vs. 4.7 mm(2), vessel 12.7 vs. 7.4 mm(2) and lumen 1.7 vs. 1.2 mm(2); (P< .01). Positive remodeling was more frequent in Group 1 than Group 2: 21/30 (70%) vs. 8/26 (31%). Plaque area correlated positively with lipid core and macrophages and negatively with fibrosis and smooth muscle cells. Atherosclerotic plaques that cause fatal thrombosis are more frequently positively remodeled and tend to be larger than nonculprit plaques with the same degree of cross-sectional stenosis. We tested whether arterial remodeling and plaque size vary between segments containing a fatal thrombosed plaque versus an equi-stenotic nonculprit plaque. Culprit vessel segments had higher cross-sectional areas of intimal plaque and of vessel wall than equi-stenotic nonculprit plaques. The cross-sectional area of the vessel correlated positively with both the lipid core area and CD68(+) macrophage content, and negatively with fibrosis area and smooth muscle cell content. These results add elements explaining limitations of angiography in identifying plaques and provide new insights into the role of remodeling in plaque instability.

Intravascular-ultrasound-guided percutaneous transluminal coronary angioplasty/provisional stent implantation strategy: impact on long-term clinical follow-up

Two hundred and eighty-four consecutive patients with 438 native coronary artery stenoses were enrolled prospectively in a study of intravascular ultrasound (IVUS)-guided percutaneous transluminal coronary angioplasty (PTCA) with provisional stenting: (1) aggressive lesion-site media-to-media balloon-sizing; (2) IVUS-assessment of residual lumen dimensions to identify optimal PTCA results (minimum lumen area = 65% of the average of the proximal and distal reference lumen areas or = 6.0 mm(2) and no major dissection); and (3) liberal stent crossover. Overall, 206 stenoses in 134 patients (47%) were treated with PTCA alone. Reasons for crossover were flow-limiting or lumen-compromising dissections in 28% of patients and suboptimal IVUS minimum lumen area in 72% of patients. At one year, 8% of stenoses in the PTCA group and 16% in the stent crossover group required revascularization. In approximately half of the patients treated using an IVUS-guided aggressive PTCA strategy, stent implantation could be avoided without sacrificing an increase in acute complications or worse clinical outcome.

Coronary atherosclerosis in unheralded sudden coronary death under age 50: histo-pathologic comparison with 'healthy' subjects dying out of hospital

AIM

sudden coronary death (SCD) in older individuals is generally associated with extensive coronary atherosclerosis, although it may be the first manifestation of ischaemic heart disease. In younger age-groups, SCD may occur in the presence of less severe disease. We sought to (1) examine the extent of coronary atherosclerosis in young victims of SCD compared with age- and sex-matched controls, (2) analyse the composition of atherosclerotic plaques in these patients, (3) identify the predominant mechanism of SCD, and (4) evaluate the possibility of detecting this mechanism on the basis of morphologic plaque features, in particular presence and amount of lipid accumulation and calcific deposits.

METHODS AND RESULTS

coronary arteries were obtained at autopsy from 28 victims of SCD under age 50 with no prior clinical manifestation of ischaemic heart disease (IHD) and no myocardial scar formation and from 16 age- and sex-matched subjects dying of noncardiac causes out of hospital. Sections of all available major coronary arteries were cut in 5-mm intervals to yield a total of 1357 histologic sections, which were analysed using digitised planimetry. Victims of SCD had significantly more major coronary arteries per subject with luminal area narrowing > or = 75% than controls (on average, 2.1 vs. 0.2). Plaque area per histologic section was 5.1 +/- 2.1 mm(2) in SCD cases and 2.0 +/- 0.9 mm(2) in controls (P < 0.001). The major constituent of all plaques was fibrous tissue. Lipid core area per section was 0.49 +/- 0.59 mm(2) in SCD cases and 0.004 +/- 0.01 mm(2) in controls (P < 0.001), and calcified plaque area was 0.18 +/- 0.19 mm(2) in SCD cases and 0.02 +/- 0.05 mm(2) in controls (P < 0.001), both defining significant differences between SCD cases and controls. Arterial thrombosis, most often with underlying plaque rupture was the mechanism of SCD in > 80% of the cases. Considering histologic sections with > or = 50 and with > or = 75% area stenosis, plaque rupture was independently predicted by lipid core area. Calcific deposits were a frequent feature of plaque rupture but were only associated with it in univariate analysis.

CONCLUSIONS

the extent and severity of coronary atherosclerosis in young victims of SCD as the first manifestation of IHD was substantially greater than in age-and sex-matched controls and comparable with that previously reported in SCD cases with a broader age range. Lipid core and calcified plaque areas provided for excellent separation between the two groups, which may have implications for identifying persons at increased risk for SCD by non invasive visualisation and assessment of the coronary arteries.

Intravascular ultrasound assessment of the morphologic similarities between stenoses located in different arteries in the same patient

To study the relation in lesion morphology and composition between multiple vessels, intravascular ultrasound studies were performed on both vessels of 131 patients undergoing subsequent 2-vessel angioplasty. Because multiple stenoses in the same patient appear more dissimilar than similar, we conclude that local factors tend to be more important than patient factors in determining the lesion morphology.

Ultrasonic integrated backscatter coefficient profiling of human coronary arteries in vitro

A theoretical formulation for the profile of the integrated backscatter coefficient (IBC) is derived. This new formulation is based on a theoretical treatment by Chen et al. [1]. It includes correction for the diffraction of the ultrasonic beam and correction for the non-ideal nature of the reference signal. The inclusion of these correction factors permits accurate quantitative profiling of the IBC over the transducer focal zone. Experimental measurements are first performed on well-calibrated vessel-equivalent phantom materials and subsequently on human coronary arteries in vitro. A spherically focused 50.0 MHz f/1.83 transducer is used. IBC profiles are shown for three samples that are representative of early, mid, and advanced atherosclerotic coronary disease. The IBC profiles clearly differentiate the arterial tissues. However, variation between samples with histologically confirmed intimal thickening (N = 24) was large. The mean IBC (+/- 1 standard deviation), in (Sr.mm)-1, for media, adventitia, and thickened intima were 3.86 x 10(-3), 1.53 x 10(-2), and 2.24 x 10(-2), respectively. The mean IBC of thickened intima is larger than previous measurements obtained from femoral arteries, and the mean IBC for media and adventitia layers are lower, reflecting differences in tissue composition between coronary and femoral vessels.

Three dimensional intravascular ultrasonic assessment of the local mechanism of restenosis after balloon angioplasty

OBJECTIVE

To assess the mechanism of restenosis after balloon angioplasty.

DESIGN

Prospective study.

PATIENTS

13 patients treated with balloon angioplasty.

INTERVENTIONS

111 coronary subsegments (2 mm each) were analysed after balloon angioplasty and at a six month follow up using three dimensional intravascular ultrasound (IVUS).

MAIN OUTCOME MEASURES

Qualitative and quantitative IVUS analysis. Total vessel (external elastic membrane), plaque, and lumen volume were measured in each 2 mm subsegment. Delta values were calculated (follow up - postprocedure). Remodelling was defined as any (positive or negative) change in total vessel volume.

RESULTS

Positive remodelling was observed in 52 subsegments while negative remodelling occurred in 44. Remodelling, plaque type, and dissection were heterogeneously distributed along the coronary segments. Plaque composition was not associated with changes in IVUS indices, whereas dissected subsegments had a greater increase in total vessel volume than those without dissection (1.7 mm(3) v -0.33 mm(3), p = 0.04). Change in total vessel volume was correlated with changes in lumen (p < 0.05, r = 0.56) and plaque volumes (p < 0.05, r = 0.64). The site with maximum lumen loss was not the same site as the minimum lumen area at follow up in the majority (n = 10) of the vessels. In the multivariate model, residual plaque burden had an influence on negative remodelling (p = 0.001, 95% confidence interval (CI) -0.391 to -0.108), whereas dissection had an effect on total vessel increase (p = 0.002, 95% CI 1.168 to 4.969).

CONCLUSIONS

The mechanism of lumen renarrowing after balloon angioplasty appears to be determined by unfavourable remodelling. However, different patterns of remodelling may occur in individual injured coronary segments, which highlights the complexity and influence of local factors in the restenotic process.

Coronary artery injury and the biology of atherosclerosis: inflammation, thrombosis, and stabilization

Conventional concepts of the pathogenesis of acute coronary syndromes are changing. High-risk lesions are not necessarily the angiographically "tight" stenoses. Rather, unstable vulnerable lesions have large lipid cores and thin fibrous caps. Plaque instability relates closely to the development of inflammation within the intima. Acute coronary syndromes usually result from rupture of a vulnerable atherosclerotic plaque mechanistically linked to the inflammatory process. Stabilization of lesions, rather than percutaneous or surgical procedures, provides a new therapeutic target. Lipid lowering may stabilize lesions by mitigating the inflammatory response.

Coronary artery compliance and adaptive vessel remodelling in patients with stable and unstable coronary artery disease

OBJECTIVE

To test the hypothesis that patients with unstable coronary syndromes show accentuated compensatory vessel enlargement compared with patients with stable angina, and that this may in part be related to increased coronary artery distensibility.

DESIGN AND PATIENTS

In 23 patients with unstable coronary syndromes (10 with non-Q wave myocardial infarction and 13 with unstable angina), the culprit lesion was investigated by intravascular ultrasound before intervention. The vessel cross sectional area (VA), lumen area (LA), and plaque area (VA minus LA) were measured at end diastole and end systole at the lesion site and at the proximal and distal reference segments. Similar measurements were made in 23 patients with stable angina admitted during the same period and matched for age, sex, and target vessel. Calculations were made of remodelling index (VA at lesion site / VA at reference site), distensibility index ([(delta A/A)/delta P] x 10(3), where delta A is the luminal area change in systole and diastole and delta P the difference in systolic and diastolic blood pressure measured at the tip of the guiding catheter during a cardiac cycle), and stiffness index beta ([ln(P(sys)/P(dias))]/(delta D/D), where P(sys) is systolic pressure, P(dias) is diastolic pressure, and delta D is the difference between systolic and diastolic lumen diameters). Positive remodelling was defined as when the VA at the lesion was > 1.05 times larger than at the proximal reference site, and negative remodelling when the VA at the lesion was < 0.95 of the reference site.

RESULTS

Mean (SD) LA at the lesion site was similar in both groups (4.03 (1.8) v 4.01 (1. 93) mm(2)), while plaque area was larger in the unstable group (13. 29 (4.04) v 8.34 (3.6) mm(2), p < 0.001). Remodelling index was greater in the unstable group (1.14 (0.18) v 0.83 (0.15), p < 0.001). Positive remodelling was observed in 15 patients in the unstable group (65%) but in only two (9%) in the stable group (p < 0.001). Negative remodelling occurred only in two patients with unstable symptoms (9%) but in 17 (74%) with stable symptoms. At the proximal reference segment, the difference in LA between systole and diastole was 0.99 (0.66) mm(2) in the unstable group and 0.39 (0.3) mm(2) in the stable group (p < 0.001), and the calculated coronary artery distensibility was 3.09 (2.69) and 0.94 (0.83) per mm Hg in unstable and stable patients, respectively (p < 0.001). The stiffness index beta was lower in patients with unstable angina (1.95 (0.94) v 3.1 (0.96), p < 0.001).

CONCLUSIONS

Compensatory vessel enlargement occurs to a greater degree in patients with unstable than with stable coronary syndromes, and is associated with increased coronary artery distensibility.

Intravascular ultrasound findings of negative arterial remodeling at sites of focal coronary spasm in patients with vasospastic angina

BACKGROUND

There are few data about the intravascular ultrasound (IVUS) findings in patients with vasospastic angina, especially regarding patterns of vascular remodeling.

METHODS AND RESULTS

Coronary spasm was documented by angiography and electrocardiographic evidence of ischemia in 36 patients after administration of ergonovine (cumulative doses up to 350 microg). After relief of spasm with 1000 microg of intracoronary nitroglycerin, quantitative angiography and IVUS imaging were performed and analyzed by standard methods. The 36 focal spasm sites were compared with the proximal and distal reference segments. The angiographic baseline minimum lumen diameter measured 1.78 +/- 0.66 mm, which decreased to 0.66 +/- 0.38 mm with ergonovine provocation (P <.0001), increased to 2.66 +/- 0.64 mm after intracoronary nitroglycerin (P <.0001 compared with baseline and after ergonovine), and did not change after IVUS imaging (2.66 +/- 0.63, P =.9). By IVUS, atherosclerotic lesions were observed at all coronary spasm sites; the mean plaque burden measured 56% at the spasm site and 35% at the reference. Spasm site plaque composition was hypoechoic in 31 and hyperechoic, noncalcific in 5; there was no calcium. The mean eccentricity index (maximum divided by minimum plaque thickness) was 6.7. Positive remodeling (spasm site arterial area greater than proximal reference) was present in 5; intermediate remodeling (proximal reference greater than spasm site greater than distal reference arterial area) was present in 7; and negative remodeling (spasm site arterial area less than distal reference) was present in 24.

CONCLUSIONS

Sites of vasospasm in patients with variant angina showed characteristics of early atherosclerosis, except for an unusually high incidence of negative arterial remodeling.

Spatial orientation of atherosclerotic plaque in non-branching coronary artery segments

It has been postulated that atherosclerotic plaque deposition is spatially related to regions of low shear in non-branching vessel segments. Intravascular ultrasound (IVUS) allows precise spatial orientation of coronary artery plaque formation in humans. The objective of this study was to test the hypothesis that coronary plaques have a higher prevalence on the myocardial side in regions that encounter low surface shear stress. IVUS allows the determination of the inner versus the outer curve of the vessel based on vascular and perivascular landmarks. We studied 30 consecutive patients pre-intervention using IVUS and measured vessel area, lumen area and plaque area (vessel-lumen area) during a motorized pullback at 1 mm intervals. Vessel segments near a side branch (within two times the diameter of the vessel) were excluded from analysis because of flow disturbances. All plaques were classified as concentric or eccentric and all eccentric plaques were further divided with respect to their spatial orientation in the vessel into quadrants: myocardial (inner curve, lower shear stress), epicardial (outer curve, higher shear stress) and lateral (two quadrants intermediate). A total of 613 cross-sections were analyzed in 14 left anterior descending, six left circumflex, and ten right coronary arteries. Plaque distribution was found to be concentric in 321 (52.4%) and eccentric in 292 (47.6%) cross sections. Of all eccentric plaques, 184 cross sections were oriented toward the myocardial side (62.6%) compared to only 54 toward the epicardial side (17.3%) and 54 in the 2 lateral quadrants (19.5%, P<0.001). No difference in plaque area (6.75+/-2.70 vs. 6.76+/-2.60 mm(2)), vessel area (15.28+/-4.73 vs. 15.35+/-4.40 mm(2)), or plaque thickness (1.26+/-0.37 vs. 1.25+/-0.43 mm) was noted between myocardial or epicardial plaques. These results suggest that atherosclerotic plaques develop more frequently on the myocardial side of the vessel wall, which may relate to lower shear stress. However, plaque size is similar on the epicardial and myocardial side.

Acute and long-term results of an intravascular ultrasound-guided percutaneous transluminal coronary angioplasty/provisional stent implantation strategy

Two hundred eighty-four consecutive patients with 438 native coronary artery stenoses were enrolled prospectively in a study of intravascular ultrasound (IVUS)-guided provisional percutaneous transluminal coronary angioplasty (PTCA): (1) IVUS-guided, aggressive lesion-site media-to-media balloon sizing, (2) IVUS assessment of residual lumen dimensions to identify optimal PTCA results (minimum lumen area > or =65% of the average of the proximal and distal reference lumen areas or > or =6.0 mm2 and no major dissection), and (3) liberal stent crossover. Overall, 206 stenoses in 134 patients were treated with PTCA alone. Reasons for crossover were flow-limiting or lumen compromising dissections in 28% of patients or a suboptimal IVUS minimum lumen area in 72% of patients. Sixty-three stenoses (27%) were treated with Gianturco-Roubin stents and 169 (73%) with Palmaz-Schatz stents. The clinical success rate and major in-hospital complication rates were similar in the optimal PTCA and stent crossover groups. At 1 year, 42 patients (15%) with 53 stenoses (12%) underwent revascularization: 8% of stenoses in the PTCA group and 16% in the stent crossover group. In approximately half of the patients treated using an IVUS guided aggressive PTCA strategy, stent implantation could be avoided without sacrificing an increase in acute complications or late clinical outcome. This provides an alternative strategy for interventionalists less inclined to use routine elective stenting.