Compensatory enlargement of angiographically normal coronary segments in patients with coronary artery disease. In vivo documentation using intravascular ultrasound

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

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

Epicardial Adipose Tissue May Mediate Deleterious Effects of Obesity and Inflammation on the Myocardium

Epicardial adipose tissue has unique properties that distinguish it from other depots of visceral fat. Rather than having distinct boundaries, the epicardium shares an unobstructed microcirculation with the underlying myocardium, and in healthy conditions, produces cytokines that nourish the heart. However, in chronic inflammatory disorders (especially those leading to heart failure with preserved ejection fraction), the epicardium becomes a site of deranged adipogenesis, leading to the secretion of proinflammatory adipokines that can cause atrial and ventricular fibrosis. Accordingly, in patients at risk of heart failure with preserved ejection fraction, drugs that promote the accumulation or inflammation of epicardial adipocytes may lead to heart failure, whereas treatments that ameliorate the proinflammatory characteristics of epicardial fat may reduce the risk of heart failure. These observations suggest that epicardial adipose tissue is a transducer of the adverse effects of systemic inflammation and metabolic disorders on the heart, and thus, represents an important target for therapeutic interventions.

The use of echocardiography for the non-invasive evaluation of coronary artery disease

In the Western world, there are now millions of patients who undergo clinical procedures that evaluate coronary artery status each year. Methods span from direct imaging using angiography, computerized tomography, to nuclear magnetic imaging as well as to functional studies, such as positron emission tomography. These techniques have provided significant information to physicians, but there is still need for an improved accessibility. Angiographic methods are expensive and expose the patient to significant amounts of radiation, undesirable in younger patients. Among the novel technologies for coronary diagnostics, transthoracic echocardiography (TTE) of coronary arteries has provided an important alternative, particularly in everyday practice. Diagnostic arterial TTE can allow determination of the coronary wall lumen in at least three major coronary segments (left main [LM], left arterial descending [LAD] and right coronary artery [RCA]). Coronary wall thickness using the LAD has been preliminarily shown to be related to the risk of coronary events. Since it is well ascertained that coronary lesions found in any location indicate that at least 80% of the coronary tree is affected, this is very important clinical information. Evaluation of coronary status by TTE is a novel technology providing important information in ischemic syndromes, in cases of coronary malformations and other coronary diseases. KEY MESSAGES Coronary evaluation can be carried out by a variety of both invasive and non-invasive methods, many requiring radiation exposure or patient immobility. Transthoracic echocardiography (TTE) of the coronaries can, in particular, evaluate the coronary wall thickness, and this may be directly related to the coronary disease risk. TTE is a useful method for the monitoring of coronary flow reserve and can allow the detection of coronary malformations.

Changes in left anterior descending coronary artery wall thickness detected by high resolution transthoracic echocardiography

Recently, it has been demonstrated that high-resolution transthoracic echocardiography (HRTTE) is able to detect differences in the wall thickness of the left anterior descending coronary artery (LAD) between patients with coronary artery disease (CAD) and normal volunteers. The aim of this study was to further validate this technique. One hundred ten volunteers, 58 patients with angiographically proved CAD and 52 control subjects, underwent assessments of their LADs using HRTTE. Anterior and posterior wall thicknesses differed between subjects in the CAD group and controls (1.9 +/- 0.6 vs 1.2 +/- 0.3 mm, p <0.001, and 1.8 +/- 0.5 vs 1.2 +/- 0.3 mm, p <0.001, respectively). External LAD diameter was also greater in subjects in the CAD group compared with controls (5.2 +/- 1.9 vs 4.4 +/- 0.9 mm, respectively, p = 0.01). However, there was no difference in luminal diameter between subjects in the CAD group and the controls (1.9 +/- 0.9 vs 2.1 +/- 0.8 mm, respectively, p = 0.3). In conclusion, HRTTE demonstrated that LAD wall thicknesses and external diameters in patients with CAD were significantly larger than in normal volunteers. Luminal diameter, however, was maintained in the 2 groups, indicating that subjects in the CAD group had undergone positive remodeling at the site measured. This objectively visualized evidence of coronary atherosclerosis with HRTTE would likely be undetected during coronary angiography.

Ultrasound-guided strategy for provisional stenting with focal balloon combination catheter: results from the randomized Strategy for Intracoronary Ultrasound-guided PTCA and Stenting (SIPS) trial

BACKGROUND

Intracoronary ultrasound (ICUS) has provided insights into vascular pathology and interventional therapy. The Strategy for ICUS-Guided PTCA and Stenting (SIPS) trial tested the hypothesis that routine ICUS guidance of coronary interventions improves outcome.

METHODS AND RESULTS

A single-center consecutive-patient randomized design (with 6-month angiographic and 2-year clinical follow-up) was used. Consecutive patients (no chronic total occlusions or emergency procedures) were randomized to ICUS-guided provisional stenting or standard angiographic guidance. Quantitative angiographic minimal lumen diameter (MLD), angiographic restenosis, clinically driven target lesion revascularization, and major adverse cardiac events (MACEs) were evaluated. A total of 291 procedures (356 lesions) were included. Procedure success was higher in the ICUS-guided group than the group randomized to standard guidance (94. 7% versus 87.4%, respectively; P:=0.033), whereas time (65.2+/-31.0 versus 60.5+/-34.0 minutes, P:=0.18) and contrast use (209.3+/-94.1 versus 197.5+/-89.5 mL, P:=0.23) were not significantly different. Stenting rates were similar (49.7% versus 49.5%, P:=0.89). Acute gain was greater in the ICUS-guided group than in the standard guidance group (1.85+/-0.72 versus 1.67+/-0.76 mm, respectively; P:=0.02). Angiographic 6-month analysis revealed no difference in MLD (1.71+/-0.94 versus 1.57+/-0.90, P:=0.19) or binary restenosis rate (>50% diameter stenosis) (29% versus 35%, P:=0.42). Clinical follow-up (602+/-307 days) showed a significant decrease in clinically driven target lesion revascularization in the ICUS group compared with the standard guidance group (17% versus 29%, respectively; P:=0.02).

CONCLUSIONS

Although angiographic MLD did not differ significantly after 6 months, ICUS-guided provisional stenting improved 2-year clinical results after intervention.

Longitudinal study of vascular remodeling in coronary arteries after heart transplantation

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

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

BACKGROUND

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

METHODS AND RESULTS

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

CONCLUSIONS

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

Assessment of coronary compensatory enlargement by three-dimensional intravascular ultrasound

Several techniques have been used to demonstrate that human arteries respond to atherosclerosis by increasing their total arterial area to prevent a decrease in blood flow. Three-dimensional reconstructions of coronary arteries can document this compensatory response accurately and specifically. Seven human coronary arteries were reconstructed using intravascular ultrasound and biplane angiography, and vessel geometries were quantified. In all seven vessels, as plaque area increased, overall vessel area increased (R = 0.986, 0.933, 0.984, 0.678, 0.763, 0.963, and 0.830), but luminal cross-sectional area did not significantly decrease. Focal compensatory enlargement was identified in each vessel, and in some cases this response appeared to occur until the vessel was 65% occluded. Luminal enlargement near the proximal ends was attributed to the natural taper of the vessel. The semi-automated, three-dimensional segmentation technique used in this study allows reproducible quantification, as there is no subjective manual tracing involved. Following the intravascular ultrasound transducer in time and space with biplane angiography allows for accurate reconstruction with or without automated pullback devices. Information on the rate of change of vessel measurements is also presented, which, when combined with visualization of accurate 3D geometry, provides a unique assessment of coronary compensatory enlargement. This reconstruction technique can be applied in a clinical environment with no major modification.

Compensatory arterial enlargement is a common pathobiologic response in early atherosclerosis

BACKGROUND

Human arteries are dynamic conduits that respond to different stimuli by remodeling their structure and size. Arterial dilatation has been shown to occur in moderate and advanced atherosclerosis in studies that evaluated only one artery, either coronary, carotid, or superficial femoral artery (SFA). The purpose of this study was to quantify and compare compensatory arterial enlargement throughout the peripheral vascular system in early atherosclerosis.

METHODS

Seventy-two patients (40 male, 32 female, mean age 67 +/- 12 years) underwent transcutaneous B-mode ultrasound imaging during routine examinations. Thirty-nine carotid, 19 aorta, 19 iliac, 23 common femoral (CFA), 21 SFA, and 23 popliteal arteries were longitudinally imaged. Eight healthy volunteers (6 male, 2 female, mean age 27 +/- 2.2 years) had the same arteries evaluated (n = 48). Internal diameter (ID) and external diameter (ED) were measured in disease-free areas and in paired adjacent areas exhibiting increased intima-media thickening (IMT) and small atherosclerotic plaques. The percent change in ID, ED, IMT, and plaque thickness were calculated.

RESULTS

There was no observed change in ID or ED in all arteries of the healthy volunteers. When compared with normal vessel segments, all arteries demonstrated a marked decrease in ID and increase in ED in areas of small, hemodynamically insignificant plaque. The aorta had a 6.00% +/- 1.92% increase in ED, which was significantly less than the percent increase in ED observed in carotid (8.14 +/- 4.5%. P = 0.05), CFA (9.73 +/- 3.54%, P = 0.0001), SFA (9.15 +/- 4.25%, P = 0.005), and popliteal arteries (9.67 +/- 4.34, P = 0.002). In all arteries there was a strong correlation between plaque thickness and percent change in ED with the best correlation observed in the popliteal artery (R2 = 0.823, P < 0.0001). IMT was significantly increased in all normal vessel segments of the patients when compared with the healthy volunteers (P < 0.001).

CONCLUSION

All peripheral arteries dilate in response to intima-media thickening and early atherosclerotic plaque formation. This adaptive response occurs at the site of the lesion to preserve luminal area. The percent change in ED is strongly related to plaque thickness and is greatest in the more distal arteries.

Regional remodeling of atherosclerotic arteries: a major determinant of clinical manifestations of disease

In this review we present the current data on remodeling, based on in vivo ultrasound imaging or postmortem histologic analysis of native peripheral and coronary arteries from animal models and studies in patients (coronary artery saphenous vein bypass grafts, lesions of restenosis after balloon angioplasty and other catheter-based interventions). Histologic and ultrasound imaging studies of arteries with atherosclerosis and after vascular injury reveal that arterial remodeling is common and that the cross-sectional area of the vessel is not constant. Compensatory enlargement, inadequate compensatory enlargement and shrinkage at the site of atherosclerotic lesions occurs in coronary and peripheral arteries. Current studies demonstrate that arterial remodeling is a major determinant of vessel lumen size.