Intravascular ultrasound assessment of atherosclerosis

Evaluation of Blood Induced Influence for High-Definition Intravascular Ultrasound (HD-IVUS)

High-definition intravascular ultrasound (HD-IVUS) utilizing more than 80 MHz frequency to assess atherosclerotic plaque, can theoretically achieve an axial resolution of less than [Formula: see text]. However, the blood is a high-attenuation source at high frequency, which would affect the imaging quality. There has been no research evaluating the blood-induced influence on HD-IVUS imaging. And whether a temporary removal of blood is needed for HD-IVUS is unknown. In this study, an ultrahigh-frequency (100 MHz) ultrasound transducer was developed to evaluate the blood-induced attenuation for HD-IVUS imaging. A series of tungsten-wire phantom images in saline and blood at varying hematocrits were obtained. The images showed that blood did influence the ultrahigh-frequency imaging quality greatly. The signal-to-noise ratio (SNR) decrease by 71.7% in porcine whole blood compared to that in saline at the same depth of 2.3 mm. Moreover, the potential flushing schemes for HD-IVUS were studied in varying hematocrits. Three flushing agents commonly used in intravascular optical coherence tomography (IV-OCT) were investigated, including iohexol, mannitol, and dextran 5% and saline as the control group. The attenuation of blood in varying hematocrits/flushing agents was measured from 90 to 110 MHz. The result indicated dextran 5% was a suitable flushing agent for HD-IVUS due to its less signal attenuation compared to others.

A prospective randomized feasibility trial comparing angiography and angiography with intravascular ultrasound for treatment of hemodialysis access failures

OBJECTIVE

Hemodialysis accesses suffer from limited primary patency requiring frequent interventions, revisions, or even abandonment. Prolongation of access life and usability with minimization of these adverse events is paramount. Endovascular methods are established first-line interventions for failing arteriovenous access and treatment of venous outflow stenoses. The Primary goal of this feasibility study was to evaluate intravascular ultrasound (IVUS) during interventional treatments on outcomes in those undergoing angiography for failing hemodialysis access. Secondary goals were to determine differences between IVUS and angiography on vessel and lesion characteristics and impact on treatment.

METHODS

In this prospective, randomized controlled trial, patients scheduled for angiography to evaluate and treat a failing hemodialysis access were randomized to use of angiography (DSA) alone or angiography plus IVUS (DSA + IVUS). Patients were treated by a standardized protocol and seen in follow-up at 2 weeks, and every 3 months for 2 years or until a study endpoint was reached. Measurement of vessel diameters, % stenosis, lesion length, and study endpoints (AV access thrombosis, re-intervention, or surgical revision) were recorded.

RESULTS

A total of 55 subjects were enrolled, 27 in the DSA cohort and 28 in the DSA + IVUS cohort. There were 41 treated lesions in each group. Freedom from the composite endpoint of AV access thrombosis or re-intervention was 46.3% in the DSA cohort and 61.0% in the DSA + IVUS cohort (p = 0.27). Diameter measurements matched between the two imaging modalities only 9 times out of 41 total comparison measures. In pre-treatment lesions with >80% stenosis, IVUS had a greater tendency than DSA to underestimate the severity of stenosis, whereas in pre-treatment lesions with 50-80% stenosis, DSA was more likely than IVUS to underestimate the severity of stenosis. Post-treatment % stenosis had mean difference of -7.5% between DSA versus DSA + IVUS cohorts. In five lesions with <30% stenosis measured by angiogram, IVUS led to treatment escalation.

CONCLUSION

In the interventional treatment of failing angioaccess, IVUS and angiography differ in the vast majority of cases in measurement of vessel diameter. A significant number of patients were found to have suboptimal therapeutic response by IVUS only, which led to an escalation in treatment, and in over one-third of cases, the IVUS results led to a change in treatment plan. The improved patency rates in the IVUS group was not statistically significant in this small population but should be further investigated in a larger trial.

Cable shared dual-frequency catheter for intravascular ultrasound

This study proposes a catheter consisting of dual-frequency transducer for intravascular ultrasound. Both ultrasonic elements with different frequencies were connected to one coaxial cable to make the connection simple. The aperture size of the ultrasound elements were 0.4×0.6 mm2 and 0.3×0.4 mm2 for the low frequency element and high frequency element, respectively. The center frequency and bandwidth of the fabricated low frequency transducer were 33.8 MHz and 49.3%, respectively. Meanwhile, the center frequency and bandwidth of the high frequency transducer were 80.6 MHz and 50.3%, respectively. Imaging evaluations of wire phantom, tissue phantom and vessel tissue demonstrated good imaging capability of the dual-frequency catheter. The spatial resolution are 19 μm axially and 128 μm laterally for the high frequency transducer, and 37 μm axially and 199 μm laterally for the low frequency transducer. Band-pass filters were designed to separate the mixed echo signals. After filtering, the images from different ultrasound elements can be successfully identified, indicating the feasibility of the proposed cable shared dual-frequency imaging strategy. The proposed method has simple structure, good imaging resolution, and large penetration depth, showing good application prospect for intravascular ultrasound.

Optical coherence tomography guided PCI - initial experience at Apollo Health City, Jubilee Hills, Hyderabad

Background

The capability of OCT to examine the structure of the arterial wall before or after PCI is superior to those of other imaging modalities. Therefore the application of OCT during PCI seems logical and has the potential to enhance our performance during the PCI procedures.

Methods

OCT was performed in fifty-two patients out of which, 45 patients underwent PCI. Out of these 45 patients, in 25 patients both pre and post PCI OCT assessment was done. In 20 patients only post PCI OCT assessment was done. In seven patients PCI was not done due to nonsignificant obstruction, these seven patients were not included in final analysis.

Results

Over all OCT leads to management changes in 65% of the time it was used. Alteration of stent length was done in 56% of the cases when evaluated pre PCI. Alteration of stent diameter was done in 36% cases when evaluated pre PCI. Treatment of malapposition was done in 24% of total cases. Further balloon dilatation for vessel expansion was done in 15% of total cases. In one case left main stenting was done after proximal edge dissection.

Conclusion

OCT makes better visualization of plaque, thrombus, stent malapposition, dissection, plaque prolapse and helps in optimization of PCI results. More extensive, long-term studies will be needed to assess the prognostic implications of these findings.

Assessment of inflammation in large arteries with 18F-FDG-PET in elderly

This paper presents repeated measurements of atherosclerosis using bimodality positron emission tomography and computed tomography (PET/CT) with 18F-fluorodeoxyglucose (18F-FDG) to assess its uptake in aorta, iliac and femoral arteries in three groups of elderly subjects classified as normals (N), hypercholesterolemics (H) and with stable angina (A) in a 12 months follow-up (T0 to T12). The subjects in group H were taking rosuvastatin (20mg/d) for 12 months before the second scan. The calcifications in the arteries were determined by CT imaging and the artery PET images were analyzed slice by slice. The standard uptake values (SUVs) for 18F-FDG uptake were classified in two main groups: calcified and non-calcified arteries and each main group comprises six sub-groups for the three subject groups N, H and A, and for the two measurements 12 months apart. Although the calcifications were present at some portions of the arteries in all subjects (23%, 36% and 44% of calcified sites to total sites analyzed, respectively, in groups N, H and A), the results show the most noticeable SUV changes after 12 months was in group N of non-calcified arteries. In the three groups, the calcified arteries showed no significant differences between T0 and T12 while significant differences were observed for the non-calcified arteries. However, there were no significant changes at T12 between groups N and H following rosuvastatin intake in group H. In conclusion, the quantitative analysis with 18F-FDG-PET/CT could be efficient in the localization of the inflammation and evaluation of its progression in atherosclerosis instead of global evaluations with systemic inflammation biomarkers.

68Ga-DOTATATE PET/CT for the detection of inflammation of large arteries: correlation with18F-FDG, calcium burden and risk factors

Background

Ga-[1,4,7,10-tetraazacyclododecane-N,N′,N″,N′″-tetraacetic acid]-d-Phe¹,Tyr³-octreotate (DOTATATE) positron emission tomography (PET) is commonly used for the visualization of somatostatin receptor (SSTR)-positive neuroendocrine tumors. SSTR is also known to be expressed on macrophages, which play a major role in inflammatory processes in the walls of coronary arteries and large vessels. Therefore, imaging SSTR expression has the potential to visualize vulnerable plaques. We assessed ⁶⁸Ga-DOTATATE accumulation in large vessels in comparison to ¹⁸F-2-fluorodeoxyglucose (FDG) uptake, calcified plaques (CPs), and cardiovascular risk factors.

Methods

Sixteen consecutive patients with neuroendocrine tumors or thyroid cancer underwent both ⁶⁸Ga-DOTATATE and ¹⁸F-FDG PET/CT for staging or restaging purposes. Detailed clinical data, including common cardiovascular risk factors, were recorded. For a separate assessment, they were divided into a high-risk and a low-risk group. In each patient, we calculated the maximum target-to-background ratio (TBR) of eight arterial segments. The correlation of the TBR_mean of both tracers with risk factors including plaque burden was assessed.

Results

The mean TBR of ⁶⁸Ga-DOTATATE in all large arteries correlated significantly with the presence of CPs (r = 0.52; p < 0.05), hypertension (r = 0.60; p < 0.05), age (r = 0.56; p < 0.05), and uptake of ¹⁸F-FDG (r = 0.64; p < 0.01). There was one significant correlation between ¹⁸F-FDG uptake and hypertension (0.58; p < 0.05). Out of the 37 sites with the highest focal ⁶⁸Ga-DOTATATE uptake, 16 (43.2%) also had focal ¹⁸F-FDG uptake. Of 39 sites with the highest ¹⁸F-FDG uptake, only 11 (28.2%) had a colocalized ⁶⁸Ga-DOTATATE accumulation.

Conclusions

In this series of cancer patients, we found a stronger association of increased ⁶⁸Ga-DOTATATE uptake with known risk factors of cardiovascular disease as compared to ¹⁸F-FDG, suggesting a potential role for plaque imaging in large arteries. Strikingly, we found that focal uptake of ⁶⁸Ga-DOTATATE and ¹⁸F-FDG does not colocalize in a significant number of lesions.

Anatomical landmarks for endosonography of the larynx

BACKGROUND

A precise knowledge of anatomy is necessary to allow a correct interpretation of sonographic images when investigating a particular region of the body. The objective of the present study was to establish anatomical landmarks for endosonography of the larynx.

METHODS

In an experimental study, a total of 32 normal human larynges were examined endosonographically, and the classical landmarks were correlated to horizontal whole-organ sections of the scanned specimens.

RESULTS

All laryngeal specimens showed a similar and reproducible sonoanatomy, which could be verified consistently on corresponding histological cross sections. Anatomical structures readily identified included the laryngeal framework, the vocal ligament, the vocal muscle, the ventricular fold, the preepiglottic and paraglottic space, and the epiglottis.

CONCLUSIONS

Due to a reproducible sonoanatomy of the larynx, endosonography might be an interesting complementary tool in the diagnostic investigation of laryngeal lesions such as medium-sized tumors, cysts, laryngoceles, and stenoses.

Intravascular ultrasound: principles and cerebrovascular applications

Intravascular sonography is a valuable tool for the morphologic assessment of coronary atherosclerosis and the effect of pharmacologic and nonpharmacologic interventions on the progression or stabilization of atherosclerosis. An analysis of the different modes, applications, and limitations is provided on the basis of review of existing data from multiple clinical case studies, trials, and mechanistic studies. Intravascular sonography has been used to assess the outcomes of different percutaneous interventions, including angioplasty and stent implantation, and to provide detailed characterization of atherosclerotic lesions, aneurysms, and dissections within the cerebrovascular circulation. Evolution of intravascular sonographic technology has led to the development of more sophisticated diagnostic tools such as color-flow, virtual histology, and integrated backscatter intravascular sonography. The technologic advancement in intravascular sonography has the potential of providing more accurate information prior, during, and after a medical or endovascular intervention. Continued assessment of this diagnostic technique in both the intracranial and extracranial circulation will lead to increased use in clinical practice with the intent to improve outcomes.

Evaluation of coronary atheroma by 64-slice multidetector computed tomography: Comparison with intravascular ultrasound and angiography

BACKGROUND

Recent improvements in multidetector computed tomography (MDCT) with 64-slice scanners have allowed acquisition of a coronary study in 5 s to 6 s, with good temporal and spatial resolution. Previous studies have reported an underestimation of plaque burden by MDCT. Whether shorter scan times can allow correct assessment of plaque volume requires comparison with intravascular ultrasound (IVUS).

METHODS

Patients (n=30) scheduled for coronary angiography also underwent MDCT and IVUS examinations within 96 h. MDCT examination was performed with a 64-slice scanner. Nitroglycerin was administered before all imaging procedures. MDCT, quantitative coronary angiography (QCA) and IVUS analyses were performed by observers blinded to other results. Plaque volumes were determined by MDCT and IVUS in one vessel, and maximum percentage diameter stenosis was identified in each coronary segment by MDCT and QCA.

RESULTS

The mean (+ or - SD) plaque volume was determined to be 179.1 + or - 78.9 mm(3) by MDCT and 176.1 + or - 87.9 mm(3) by IVUS. There was a strong positive correlation for plaque volume between MDCT and IVUS (r=0.84, P<0.0001). Percentage diameter stenosis assessed by MDCT and QCA also correlated well (r=0.88 per patient and r=0.87 per vessel, P<0.0001 for both). The maximum percentage diameter stenosis per vessel was 38.1 + or - 30.2% with MDCT and 34.1 + or - 27.6% with QCA. The sensitivity and specificity of MDCT in detecting stenoses above 50% per vessel were 100% and 91.0%, respectively.

CONCLUSIONS

Plaque volumes measured by 64-slice MDCT and IVUS correlate well, without systematic underestimation. The sensitivity and specificity of MDCT to detect stenoses greater than 50% by QCA are excellent with the administration of nitroglycerin before imaging.

Acute effects of statin therapy on coronary atherosclerosis following an acute coronary syndrome

No data exist on the acute effects of statin therapy on human coronary atherosclerotic plaques. The objective of our study was to evaluate the early (<2 months) effects of newly initiated statin therapy on coronary atherosclerosis as evaluated by intravascular ultrasonography. The study population consisted of 74 patients (mean age 58 +/- 8 years) who had been included in the ERASE trial (evaluating the effects of reconstituted high-density lipoprotein infusions). All patients underwent serial intravascular ultrasonographic (IVUS) evaluation at baseline (3 +/- 2 days after an acute coronary syndrome [ACS]) and after 6 +/- 1 weeks of follow-up. Statin therapy was initiated after ACS in 36 patients who received < or =1 dose of statins before baseline IVUS examination (newly initiated statin therapy group), and 38 patients were already on a stable statin dose before the ACS (long-term statin therapy group). Atorvastatin at a dose of 40 mg/day was the most common regimen in the 2 groups. Percent changes in atheroma volume (prespecified primary efficacy parameter) were -4.71 +/- 0.96% in the newly initiated statin therapy group (p <0.0001) and -0.54 +/- 0.89% in the long-term statin therapy group (p = 0.546; p = 0.002 for comparison between groups). Median nominal changes in atheroma volume were -9.10 mm(3) (interquartile range -12.56 to -3.73, p <0.0001 vs baseline) and 1.21 mm(3) (interquartile range -6.41 to 3.76, p = 0.429 vs baseline) in the newly initiated and long-term statin therapy groups, respectively (p = 0.003 for comparison between groups). Greater decreases in total cholesterol (r = 0.25, p = 0.035), ratio of total to high-density lipoprotein cholesterol (r = 0.28, p = 0.018), and high-sensitivity C-reactive protein (r = 0.31, p = 0.046, for patients with high-sensitivity C-reactive protein measurements within 7 days after IVUS examination) were associated with larger percent changes in atheroma volume. In conclusion, newly initiated statin therapy is associated with rapid regression of coronary atherosclerosis within 2 months. This effect was in part associated with decreases in atherogenic lipid and inflammatory parameters. These results provide insight into the rapid clinical benefits of statin therapy after an ACS.

Risk factor management: antiatherogenic therapies

Despite the advances in interventional techniques, the management of stable atherosclerosis remains the domain of optimal guideline-oriented therapy. Recent studies on the effects of aggressive lipid lowering on atheroma volume changes using intravascular ultrasound indicate that it is possible to achieve atherosclerosis regression by reaching low-density lipoprotein (LDL) levels less than 75 mg/dl. The pleiotropic anti-inflammatory effects of statins contribute to the reduction of cardiovascular (CV) event observed with aggressive lipid lowering. As a second important strategy to prevent disease progression, lifestyle changes with regular physical exercise are capable of halting the atherosclerotic process and reducing angina symptoms and CV events. Optimal medical therapy, a healthy lifestyle with regular physical exercise, and coronary interventions are not mutually exclusive treatment strategies. Over the last few decades, both have proved to be effective in significantly reducing the CV mortality in the Western world. However, risk factor modification contributed to at least half the effect in the reduction of CV mortality. This figure provides an estimate of what could be achieved if we were to take risk factor modification more seriously – especially in the acute care setting. The knowledge is there: today we have a better understanding on how to stop progression and even induce regression of atherosclerosis. Much research still needs to be done and will be done. In the meantime, however, our primary focus should lie in implementing what is already known. In addition, it is essential not just to treat CV risk factors, but also to treat them to achieve the target values as set by the guidelines of European Society of Cardiology.

Antioxidants: the good, the bad and the ugly

Inflammation has a fundamental role in mediating all stages of atherosclerotic disease. The key role of oxidation in linking lipids and inflammation to atherosclerosis is compelling and is supported by experimental evidence. However, the relevance of the antioxidant hypothesis for the treatment of patients with atherosclerosis has not been definitively proven. Results of randomized trials with 'antioxidant' vitamins have been disappointing, and there are potentially important problems associated with their use, including their potential pro-oxidant effects. Probucol has reduced postpercutaneous coronary intervention (PCI)-restenosis and progression of carotid atherosclerosis in clinical trials. The antioxidant vascular protectant AGI-1067 has also been effective at preventing atherosclerosis in all tested animal models. The nonintervened reference coronary segments of the PCI vessel demonstrated improvements with AGI-1067 in the Canadian Antioxidant Restenosis Trial-1 (CART-1), evidence supportive of a clinical effect on slowing atherosclerosis progression. Two trials test the antioxidant/anti-inflammatory hypothesis with AGI-1067; CART-2 assesses its value for the reduction of both atherosclerosis progression and post-PCI restenosis, and Aggressive Reduction of Inflammation Stops Events (ARISE), which is evaluating its effects on hard cardiovascular outcomes.

Comparison of intravascular ultrasound and quantitative coronary angiography for the assessment of coronary artery disease progression

BACKGROUND

The relative merits of quantitative coronary analysis (QCA) and intravascular ultrasound (IVUS) for the assessment of progression/regression in coronary artery disease are uncertain. To explore this subject further, we analyzed the angiographic and IVUS data derived from a contemporary clinical trial population.

METHODS AND RESULTS

We investigated the relationships between QCA and IVUS at single time points (n=525) and also for the changes over time (n=432). QCA and IVUS data underwent central laboratory analyses. Statistically significant correlations were observed between the QCA coronary artery score and the IVUS-derived lumen volume (r=0.65, P<0.0001) and total vessel volume (r=0.55, P<0.0001) and between the QCA cumulative coronary stenosis score and percent atheroma volume on IVUS (r=0.32, P<0.0001) at baseline for matched segments. A similar pattern of correlations was observed for global (all segments) QCA-derived and single-vessel IVUS-derived data. There were statistically significant but weak correlations between the changes over time in lumen dimensions on QCA and IVUS (P=0.005) and between the change in cumulative coronary stenosis score on QCA and percent atheroma volume on IVUS (r=0.14, P=0.01). Nevertheless, patients with and without angiographic progression had changes in plaque volume on IVUS of 9.13 and 0.20 mm3, respectively (P=0.028).

CONCLUSIONS

QCA- and IVUS-derived measures of lumen dimensions are correlated at single time points and for changes over time. Although the change in percent atheroma volume is only weakly correlated with QCA changes as continuous variables, disease progression on QCA is associated with significant increases in plaque volume on IVUS compared with no angiographic progression.

Carotid intima-media thickness as a surrogate marker for cardiovascular disease in intervention studies

BACKGROUND

Cardiovascular trials using clinical endpoints to assess efficacy typically require follow-up of large numbers of participants for 3-5 years. This disadvantage has encouraged the search for well-validated surrogate markers for cardiovascular disease (CVD). These markers may provide earlier indications of efficacy in trials involving fewer participants. One approach gaining interest in recent years is the measurement of atherosclerotic progression, a major underlying cause of CVD.

SCOPE

This review article aims to further substantiate the evidence supporting the use of measurement of carotid intima-media thickness (CIMT) as a surrogate marker for atherosclerosis and cardiovascular risk.

FINDINGS

CIMT has consistently been related to future CVD events in population studies. CIMT is significantly related with other markers for CVD risk, such as elevated levels of risk factors and presence of atherosclerosis in the coronary arteries. Furthermore, almost all lipid-lowering trials and a large number of blood pressure lowering trials have consistently shown a reduction in progression of CIMT. In addition, the ultrasound technique for measuring CIMT is safe and highly reproducible.

CONCLUSION

Thus, CIMT may be used as a surrogate endpoint in clinical trials to enable the benefits of new therapies or regimens to be more rapidly translated into clinical practice.

Effect of atherosclerotic regression on total luminal size of coronary arteries as determined by intravascular ultrasound

We assessed vascular changes during atherosclerosis regression. Compensatory enlargement of coronary arteries accommodates plaque burden during atherosclerosis development. Lipid-lowering therapy has altered the natural history of coronary atherosclerosis, but the arterial changes that occur during disease regression need to be clarified. Intravascular ultrasound was performed at baseline and after approximately 18 months in 432 patients with coronary disease. Mean plaque, lumen, and total vessel area were computed in a 30-mm coronary segment of interest. Mean low-density lipoprotein cholesterol level was 2.4 mmol/L, and 88% of patients received statins. Overall, changes in plaque and total vessel areas were highly correlated (r = 0.82, p <0.0001). Among the 227 patients with plaque regression, the plaque area decrease was -0.58 +/- 0.54 mm(2), and changes in total vessel and lumen areas were -1.02 +/- 1.10 and -0.44 +/- 0.86 mm(2), respectively. The decrease in plaque area correlated better with the change in total vessel area (r = 0.64, p <0.0001) than with the change in lumen area (r = 0.20, p = 0.003). The relation between plaque regression and decrease in total vessel area was significantly better (p = 0.019) for patients with a >40% atheroma area (r = 0.72; p <0.0001) than for those with <or=40% (r = 0.48; p = 0.0004). In conclusion, regression of atherosclerotic plaque is generally accompanied by a decrease in total vessel size, without an increase in luminal dimensions. This reverse vascular remodeling may be responsible for the "regression paradox," whereby secondary prevention is associated with clinical benefits despite minimal improvement in coronary lumen dimensions.

Improving outcomes in heart transplantation: the potential of proliferation signal inhibitors

Graft failure and mortality among heart transplant recipients remains higher than in populations receiving renal transplants. A major cause of graft loss is cardiac allograft vasculopathy (CAV), a condition characterized by diffuse thickening of coronary blood vessels. CAV often progresses silently, with major cardiac events (eg, ventricular arrhythmia) being the first presentation. Better diagnosis and monitoring of CAV is now possible with intravascular ultrasonography, a sensitive technique for measuring intimal thickness. To date, immunosuppressants have shown little efficacy for preventing CAV. However, a new class of agents, proliferation signal inhibitors (sirolimus and everolimus), have shown considerable efficacy in this regard and for preventing rejection. In an open-label trial, sirolimus therapy was associated with less intimal and medial proliferation than azathioprine. More robust evidence is available from a larger-scale, double-blind trial involving everolimus. At 12-month follow-up the incidence of CAV was significantly lower in patients receiving everolimus (35.7% and 30.4% for everolimus 1.5 and 3.0 mg/d vs 52.8% for azathioprine; P < .05). Sirolimus and everolimus were also associated with a lower rate of cytomegalovirus infection. As with other immunosuppressants, these agents are associated with adverse events (eg, hyperlipidemia), but they can be managed. Coadministration with calcineurin inhibitors (CNIs) can exacerbate CNI-related nephrotoxicity, but evidence suggests that everolimus administered with reduced-exposure cyclosporine in the maintenance phase preserves renal function without loss of immunosuppressive efficacy. Reduced CNI dosing in de novo patients is also a potential future benefit. Proliferation signal inhibitors have considerable potential for improving outcomes in heart transplantation.

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.

Long-term safety of intravascular ultrasound in nontransplant, nonintervened, atherosclerotic coronary arteries

OBJECTIVES

The goal of this study was to demonstrate that intravascular ultrasound (IVUS) examination of native coronary arteries does not result in an acceleration of the atherosclerotic process.

BACKGROUND

Intravascular ultrasound is increasingly used to assess the effects of pharmacologic agents on atherosclerosis.

METHODS

Intravascular ultrasound examinations of one coronary artery and coronary angiography were performed in 525 patients at baseline. Patients then underwent a follow-up angiogram 18 to 24 months later. All end points were evaluated in IVUS-related and non-IVUS arteries using quantitative coronary analysis. The study end points were the coronary change score (per-patient mean of minimum lumen diameter changes for all lesions measured), occurrence of new coronary lesions, and progression of preexistent lesions at follow-up. Acute angiographic and clinical complications were also analyzed.

RESULTS

Coronary change score was -0.06 +/- 0.23 mm and -0.05 +/- 0.21 mm for IVUS-related and non-IVUS arteries, respectively (p = 0.35). The increase in percent diameter stenosis from baseline to follow-up was 0.8 +/- 6.7% and 1.2 +/- 7.0% in the IVUS-related and non-IVUS arteries (p = 0.29). New lesions occurred in 3.6% and 3.9% of IVUS-related and non-IVUS arteries, respectively (p = 0.84). When all coronary lesions were considered, the incidence of lesion progression was not significantly different between IVUS-related (11.6%) and non-IVUS (9.8%) arteries. Coronary spasm occurred in 1.9% of IVUS procedures, and there was one case of acute occlusion with no long-term sequelae.

CONCLUSIONS

Intravascular ultrasound does not significantly accelerate atherosclerosis in native coronary arteries and can be used safely to assess progression/regression in clinical trials.

Antioxidants and atherosclerosis: Emerging drug therapies

Inflammation has a fundamental role in mediating all stages of atherosclerotic disease. The key role of oxidation in linking lipids and inflammation to atherosclerosis is compelling and supported by experimental evidence. However, the relevance of the antioxidant hypothesis for the treatment of patients with atherosclerosis has not been definitively proven. Probucol has reduced post-percutaneous coronary intervention (PCI) restenosis and progression of carotid atherosclerosis in clinical trials. The antioxidant/vascular protectant AGI-1067 has also been effective at preventing atherosclerosis in all tested animal models. The nonintervened reference coronary segments of the PCI vessel demonstrated improvements with AGI-1067 in the Canadian Antioxidant Restenosis Trial-1 (CART-1), evidence supportive of a clinical effect on slowing atherosclerosis progression. Results of randomized trials with the "antioxidant" vitamins have been disappointing, but there are potentially important problems associated with their use, including their potential pro-oxidant effects. Two important trials that test the antioxidant/anti-inflammatory hypothesis are ongoing with AGI-1067: CART-2, which assesses its value for the reduction of both atherosclerosis progression in non-PCI vessels and post-PCI restenosis; and Aggressive Reduction of Inflammation Stops Events (ARISE), which is evaluating the effects of AGI-1067 on hard cardiovascular outcomes.

Statins and LDL-cholesterol lowering: an overview

Statins have become a cornerstone of treatment for dyslipidaemia primarily due to their marked lowering of low-density lipoprotein cholesterol (LDL-C). Studies show that statin treatment typically reduces relative risk of cardiovascular disease by 24-37%, regardless of age, sex, prior history of coronary heart disease (CHD), or other co-morbid conditions. There is also a growing body of evidence that statins can be effective in people whose LDL-C is not considered elevated under current guidelines. In both the Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT) and the Collaborative Atorvastatin Diabetes Study (CARDS), participants randomised to atorvastatin (10 mg/day) experienced at least a one-third reduction in major cardiovascular events, even though at baseline, their LDL-C was within the normal range. Other studies have also provided evidence that more intensive lipid-lowering regimens could provide additional clinical benefits. In the Reversal of Atherosclerosis with Aggressive Lipid Lowering (REVERSAL) trial, the first active-control clinical trial of CHD progression, an intensive lipid-lowering regimen using atorvastatin (80 mg/day) decreased atherogenic lipoproteins and atheroma volume in patients with established CHD, compared with a moderate regimen using pravastatin (40 mg/day). Furthermore, relative to baseline, there was no measurable atheroma progression in the atorvastatin group. While statin therapy does offer significant clinical benefit, 60-70% of major cardiovascular events are still not prevented, which underscores the need for alternative interventions. Targeting inflammatory mediators of atherosclerosis such as C-reactive protein (CRP), as well as combination therapy to simultaneously raise high-density lipoprotein cholesterol (HDL-C) and lower LDL-C, are among the promising new strategies for primary and secondary prevention of atherosclerotic disease. This article will summarise data concerning use of statins in patients without markedly elevated LDL-C. The issue of the ideal LDL-C target will also be considered before addressing future treatment options for dyslipidaemia.

Effects of the acyl coenzyme A:cholesterol acyltransferase inhibitor avasimibe on human atherosclerotic lesions

BACKGROUND

Inhibition of the acyl coenzyme A:cholesterol acyltransferase (ACAT) enzyme may prevent excess accumulation of cholesteryl esters in macrophages. The ACAT inhibitor avasimibe was shown to reduce experimental atherosclerosis. This study was designed to investigate the effects of avasimibe on human coronary atherosclerosis.

METHODS AND RESULTS

This randomized, double-blind, placebo-controlled trial assessed the effects of avasimibe at dosages of 50, 250, and 750 mg QD on the progression of coronary atherosclerosis as assessed by intravascular ultrasound (IVUS). All patients received background lipid-lowering therapy if necessary to reach a target baseline LDL level <125 mg/dL (3.2 mmol/L). IVUS and coronary angiography were performed at baseline and repeated after up to 24 months of treatment. Approximately equal percentages of patients across groups received concurrent statin therapy (87% to 89%). The mean total plaque volume at baseline was approximately 200 mm3, and the least squares mean change at end of treatment was 0.7 mm3 for placebo and 7.7, 4.1, and 4.8 mm3 for the avasimibe 50, 250, and 750 mg groups, respectively (adjusted P=0.17 [unadjusted P=0.057], 0.37, and 0.37, respectively). Percent atheroma volume increased by 0.4% with placebo and by 0.7%, 0.8%, and 1.0% in the respective avasimibe groups (P=NS). LDL cholesterol increased during the study by 1.7% with placebo but by 7.8%, 9.1%, and 10.9% in the respective avasimibe groups (P<0.05 in all groups).

CONCLUSIONS

Avasimibe did not favorably alter coronary atherosclerosis as assessed by IVUS. This ACAT inhibitor also caused a mild increase in LDL cholesterol.