Distal Reference Sites Research Articles

Stable carbon isotopic compositions of archaeal lipids constrain terrestrial, planktonic, and benthic sources in marine sediments

Archaea occupy an important niche in the global carbon cycle and their lipids are widely used as indicators of environmental conditions in both paleoenvironmental and modern biogeochemical studies. The principal sources of archaeal lipids in marine sediments are benthic archaea, fossil remnants of planktonic archaea, and allochthonous sources such as soils. However, the relative contributions of these sources to the sedimentary lipid pool have not been comprehensively constrained, complicating a mechanistic understanding of archaeal lipid proxies. In order to provide insights into the relative contributions of these sources and identify signals derived from sedimentary activity, we performed a systematic survey of stable carbon isotopic compositions (δ13C) of both core and intact archaeal lipids via analyses of their phytanyl (Phy) and biphytanyl (BP) moieties in diverse marine sediments. The sample set consisted of 44 sediment horizons from the Mediterranean and adjacent basins and represented diverse sources of organic matter and depositional conditions. Complementary geochemical data enabled the comparison of lipid distributions and carbon isotopic signatures with prevailing redox conditions. The δ13C of tricyclic BP (BPcren) from the core and intact forms of crenarchaeol ranged from −19.1 to −28.6‰ and −18.1 to −27.4‰, respectively. δ13C values of core and intact BPcren did not differ, suggesting that intact crenarchaeol is either a fossil relic from planktonic archaea or a product of lipid recycling by benthic archaea, as opposed to being synthesized de novo by sedimentary archaea. δ13C values of BP0 derived from core and intact forms of glycerol and butanetriol dibiphytanyl glycerol tetraethers (GDGTs and BGDTs, respectively), but predominantly from caldarchaeol (GDGT-0), ranged from −19.4 to −32.0‰ and −20.9 to −37.0‰, respectively. In contrast to BPcren, intact-lipid derived BP0 was often 13C-depleted relative to its core counterpart, consistent with in situ production by sedimentary archaea. This relative depletion was most pronounced in sulfate reduction zones, likely due to heterotrophic activity. Core and intact archaeol exhibited the largest ranges in δ13C values, from −21.6 to −42.1‰ and −22.7 to −58.9‰, respectively. This strong 13C-depletion relative to both total organic carbon and dissolved inorganic carbon is consistent with mixtures of functional sources of sedimentary chemolithoautotrophic, methanotrophic, methanogenic and heterotrophic archaea. Based on the substantial 13C-depletion of BPcren and BP0 in samples in the vicinity of the Rhône River delta relative to a distal marine reference site, we infer that the terrestrial soil contribution of archaeal lipids to these sediments is as high as 43%. Hence, terrestrial input of archaeal lipids, including their intact forms, can be substantial and suggests caution when using existing molecular proxies aimed at constraining riverine input. In summary, our comparative isotopic analysis of sedimentary core versus intact archaeal lipids improves the apportionment of their diverse sources and confidence in distinguishing in situ lipid production by sedimentary archaea.

Comparison between optical frequency domain imaging and intravascular ultrasound in PCI guidance for Biolimus A9 eluting stent implantation

Abstract Background It has been reported that intravascular ultrasound (IVUS) guided PCI reduced a risk of major adverse cardiac event compared to conventional angiography guided PCI, while comparison between IVUS-guided and optical frequency domain imaging (OFDI)-guided PCI specifically in long-term clinical outcomes (>1 year) has been unexplored. Purpose We sought to compare imaging surrogates at 8 months and clinical outcomes beyond 1 year after drug-eluting stent implantation between IVUS and OFDI guidance. Methods The MISTIC-1 is a prospective, multi-centre, single-blinded, randomised-controlled, non-inferiority trial comparing OFDI-guided and IVUS-guided PCI using Biolimus A9 eluting Nobori stent. We enrolled patients with stable coronary artery disease who have symptoms or clinically relevant myocardial ischemia. Stent landing zones were selected in the most normal looking sites with largest lumen and without percentage plaque area >50% in IVUS group while without lipidic plaque of >2 quadrants or suggestive thin-cap fibroatheroma in OFDI group. Stent sizing was based on external elastic lamina (EEL) in IVUS group, while by taking 10% or 0.25mm larger than mean lumen diameter at reference sites in OFDI group. Stent optimisation with in-stent minimum lumen area ≥80% of the average lumen area at proximal and distal reference sites was encouraged in both groups. Primary efficacy endpoint is in-segment minimum lumen area (MLA) assessed by OFDI at 8 months. Secondary safety endpoint is a composite of cardiovascular death, target vessel myocardial infarction, or target lesion revascularisation. Based on the assumption that mean in-segment MLA at follow-up was 4.5mm2 with a standard deviation of 2.0mm2 in the control (IVUS) group and a non-inferiority limit of 1.2mm2 for OFDI group, sample size was estimated as 48 cases in each group with 5% type I error and 90% statistical power. Results Since June-2014 and August-2016, we prospectively enrolled 109 patients (mean age 70 years, male 78%) with 126 lesions. Baseline patient and lesion characteristics were well balanced and average nominal size and length of stent used did not differ between OFDI-guided and IVUS-guided PCI (3.0 and 19.1mm vs. 3.1 and 19.3mm, respectively). Post-procedural minimum stent area was 6.24mm2 in OFDI group and 6.72mm2 in IVUS group (p=0.20). At 8-month follow-up, in-segment MLA was 4.56mm2 in OFDI group and 4.13mm2 in IVUS group (P for non-inferiority <0.001). During the follow-up (median 4.5 years [1654 days]), incidence rates of major adverse cardiac event were comparable between the two groups (7.4% in OFDI group and 7.3% in IVUS group, hazard ratio 0.96, 95% CI 0.24–3.83, p=0.95). No definite or probable stent thrombosis were documented in both groups. Conclusion OFDI-guided PCI demonstrated comparable results in achieving satisfactory imaging surrogates as well as long-term clinical outcomes after newer generation DES implantation as compared to IVUS-guided PCI. Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): Suzuken Memorial Foundation

Intravascular Ultrasound Validation of Contemporary Angiographic Scores Evaluating the Severity of Calcification in Peripheral Arteries

Purpose: To validate 3 angiographic scoring systems for peripheral artery calcification using intravascular ultrasound (IVUS) as the gold standard. Methods: The study employed preprocedure angiography and IVUS data from 47 patients (median age 72 years; 34 men) in the 55-patient JetStream G3 Calcium Study ( ClinicalTrials.gov identifier NCT01273623) to validate the 3 angiographic scoring systems [Peripheral Academic Research Consortium (PARC), Peripheral Arterial Calcium Scoring System (PACSS), and the DEFINITIVE Ca++ trial]. Preprocedure angiograms were analyzed using conventional quantitative vessel analysis software in 2 orthogonal views. Calcium length was evaluated by markers placed beside the artery during the procedure; calcium deposit(s) were assessed as being on one or both sides of the vessel wall. The 3 calcium scoring systems used these 2 basic angiographic elements to evaluate calcium severity. Based on these criteria, calcium severity varied from none to focal, mild, moderate, or severe in PARC; grade 0 to 4 in PACSS; and none, moderate, or severe in the DEFINITIVE Ca++ system. Calcium location on IVUS was classified as superficial, deep, or mixed. Lesion length was the segment between the most normal looking proximal and distal reference sites. Superficial, deep, and calcium length were based on motorized IVUS pullback. Results: IVUS detected calcium in 44/47 (93.6%) lesions, and angiography detected calcium in 26/47 (55.3%) lesions (p<0.001). The sensitivity, specificity, positive predictive value, and negative predictive value of angiography relative to IVUS were 59%, 100%, 100%, and 14%, respectively. With increasing severity of angiographic calcium, there was a stepwise increase in the prevalence of IVUS superficial calcium and the maximum arc and length of superficial calcium. Using PARC criteria, with increasing severity of calcification, IVUS maximum calcium arc increased from 120° for none to 305° for severe (p<0.001); the length of calcium increased from 7 to 68 mm (p<0.001). Though a similar trend was seen in IVUS superficial calcium, it was not observed in IVUS deep calcium. Similar observations were seen when using the PACSS and DEFINITIVE Ca++ scoring systems. Conclusion: IVUS confirmed that the PARC, PACSS, and DEFINITIVE Ca++ calcium scoring systems can be used to classify the degree of calcium in peripheral artery disease, especially superficial calcium.

Changes in the reference lumen size of target lesions before and after coronary stent implantation: Evaluation with frequency domain optical coherence tomography

ObjectiveIn optical coherence tomography (OCT)-guided percutaneous coronary intervention (PCI), stent size is usually determined according to the pre-PCI lumen size of either the distal or proximal reference site. However, the effect of the OCT imaging catheter crossing the target lesion on the reference lumen measurements has not been studied. We evaluated changes in the reference lumen size before and after PCI using frequency domain OCT. MethodsFor 100 consecutive patients with PCI, mean lumen diameter (LD) and lumen area (LA) were measured at the proximal and distal reference sites before and after coronary stent implantation with OCT. ResultsMean LD and LA of the distal reference site were significantly increased after PCI with stent implantation (2.57±0.6 to 2.62±0.64 mm, p<0.01 and 5.20±2.66 to 5.41±2.54 mm2, p<0.01, respectively). By contrast, these indices at the proximal reference site were significantly decreased. ROC curve analysis selected MLA of 1.50mm2 as the best cutoff value for changes in mean LD. Distal mean LD was markedly increased after PCI in lesions with MLA<1.50mm (2.28±0.48 to 2.40±0.17mm, P<0.001), but did not change in lesions with MLA>1.50mm2. Tissue characteristics were not correlated with changes in reference lumen size. ConclusionsWhen we select the stent size during OCT-guided PCI, we need to pay attention to the decrease in the luminal measurement of the reference sites, especially in lesions with tight stenosis.

Longitudinal heterogeneity of coronary artery distensibility in plaques related to acute coronary syndrome

How coronary distensibility contributes to stable or unstable clinical manifestations remains obscure. We postulated that the heterogeneous plaque distensibility is associated with unstable clinical presentations in patients with acute coronary syndrome (ACS). Seventeen and 19 ACS-related and -unrelated lesions, respectively, were visualized using intravascular ultrasound imaging with simultaneous intracoronary pressure recording. Systolic and diastolic lumen cross-sectional areas were measured at the lesion site and at five evenly spaced sites between the proximal and distal reference sites. The coronary distensibility index and stiffness index β were calculated for each site and averaged for each coronary segment. Maximal distensibility index, standard deviation and the difference between maximal and minimal distensibility indices within each segment were significantly higher in the ACS-related than -unrelated plaques (5.6 ± 2.3 vs. 3.7 ± 1.8, p < 0.001, 2.1 ± 0.9 vs. 1.1 ± 0.6, p < 0.001 and 5.3 ± 2.3 vs. 2.8 ± 1.5, p < 0.001, respectively). Moreover, the difference in the distensibility index between the lesion site of ACS-related plaques and the immediate proximal site was significantly larger (2.88 ± 2.35 vs. 1.17 ± 1.44, p = 0.022) than that in ACS-unrelated plaques. Coronary artery distensibility is longitudinally more heterogeneous in ACS-related than-unrelated plaques, especially between the lesion and the immediate proximal site.

Atherosclerotic reference segments influence assessment of coronary remodeling by intravascular ultrasound in patients with acute coronary syndrome

Objective To investigate the influence of atherosclerotic reference segments on coronary remodeling by intravascular ultrasound(IVUS) in patients with acute coronary syndrome(ACS). Methods One hundred and three consecutively enrolled patients [male 68 cases,female 35 cases,average age (60 ±11) years] with ACS were undergone by coronary artery angiography and IVUS with time selecting operation. The remodeling index(RI) was defined as lesion external elastic membrane cross section aere (EEM CSA) divided by the mean reference EEM CSA at the culprit vessel. Positive remodeling was RI≥ (67 cases), negative remodeling was RI <1(36 cases). The parameters of plaque were analysed between two remodeling groups, as well as compared between distal and proximal references. Results Only one patients do not have plaque at reference sites. In the analysis of 103 lesions and 102 reference sites, there were not significant different in plaque burden,plaque CSA,lumen CSA and lesion EEM CSA between two groups. Distal plaque burden[(39. 76 ±12. 54)% vs (32.38 ± 13.97)%, P <0.001] and plaque CSA [(6.14 ± 3.20)mm2 vs (4. 75 ± 3. 07) mm2, P = 0. 001] were larger than those at proximal reference. EEM CSA at distal reference was smaller than proximal one[(14. 99 ± 4. 12)mm2 vs (28. 37 ± 4. 48)mm2 , P <0. 001]. Plaque burden, plaque CSA and lumen CSA persented positive corelation between distal and proximal reference sites. Conclusions The reference segments lay a severe diffuse atherosclerosis in the group of ACS, which may influence assessment of coronary remodeling. Coronary remodeling as a process, a accurate evaluation could be result from the combination of static and serial approach by IVUS. Key words: Endosonography; Coronary disease; Ventricular remodeling; Acute coronary syndrome

Optimal Stent-Sizing With Intravascular Ultrasound Contributes to Complete Neointimal Coverage After Sirolimus-Eluting Stent Implantation Assessed by Angioscopy

The aim of this study was to explore the determinants of neointimal coverage after sirolimus-eluting stent (SES). Although SES has significantly reduced in-stent restenosis by inhibiting neointimal hyperplasia, insufficient neointimal coverage after stenting might result in adverse outcomes. We evaluated 28 SES lesions with both angioscopy and intravascular ultrasound (IVUS). Quantitative assessments of the lesions and stent expansion were performed by IVUS at the time of stent implantation, and degree of neointimal coverage was judged by angioscopy at follow-up (11 +/- 6 months) whether the stent struts were embedded by the neointima ("complete/incomplete" neointimal coverage). "Complete" coverage was identified in 10 (36%), and "incomplete" coverage was identified in 18 (64%). Time from the stenting to angioscopy as well as the lesion and procedural characteristics were similar between the complete and incomplete coverage groups. The IVUS parameters were also similar, except for the final minimum stent cross-sectional area (CSA) (7.0 +/- 1.8 mm(2) in complete vs. 5.3 +/- 1.9 mm(2) in incomplete, p = 0.02) and lumen CSA at the distal reference site (6.1 +/- 1.4 mm(2) in complete vs. 4.9 +/- 1.2 mm(2) in incomplete, p = 0.02). The ratio of the stent area to the vessel area was significantly larger in the complete coverage than in the incomplete coverage group (0.52 +/- 0.11 vs. 0.39 +/- 0.09, p = 0.002). Adequate stent sizing relative to the vessel size might contribute to the angioscopically complete neointimal coverage after SES implantation.

Impact of vascular remodeling on the coronary plaque compositions: An investigation with in vivo tissue characterization using integrated backscatter-intravascular ultrasound

Recent studies have indicated that positive remodeling is strongly associated with development of acute coronary syndrome (ACS). The aim of this study was to compare plaque composition of vascular remodeling patterns by an established in vivo tissue characterization method using integrated backscatter (IB)-intravascular ultrasound (IVUS). The study population consisted of 41 consecutive patients who received IVUS prior to percutaneous coronary intervention. Remodeling index (RI) was calculated as the external elastic membrane (EEM) area at the minimal lumen area (MLA) site divided by average EEM area at the proximal and distal reference sites. The patients were divided into two groups based on RI: positive remodeling (PR) defined as RI > 1 and non-PR as RI ≤ 1. A total of 21 areas centered at MLA per lesion site were evaluated by IB-IVUS at 1 mm intervals. The occupancy rate of four tissue types within atherosclerotic plaques was compared between the two groups. Percent lipid volume in the PR group ( n = 20) was significantly greater than the non-PR group ( n = 21) (40.5 ± 14.8% vs. 26.4 ± 15.9%, p < 0.001). In contrast, % fibrous volume in the PR group was significantly lower than the non-PR group (49.9 ± 9.4% vs. 56.1 ± 9.6%, p = 0.042). Percent dense fibrous volume and % calcified volume were slightly but significantly lower in the PR group compared with the non-PR group (dense fibrous: 6.8 ± 5.0% vs. 11.6 ± 8.4%, p = 0.034, calcified: 2.6 ± 2.0% vs. 5.1 ± 4.4%, p = 0.026). In conclusions, PR lesions contain more lipid-rich and less hard plaque components compared with non-PR lesions, which may account for the higher incidence of ACS and plaque vulnerability.

Abstract 2777: Optimal Expansion of the Stent is a Major Contributor to the Neointimal Coverage Following Sirolimus-eluting Stent Implantation: A Combined Study of Angioscopy and Intravascular Ultrasound

Background: Although sirolimus-eluting stent (SES) has significantly reduced in-stent restenosis by inhibiting neointimal hyperplasia, insufficient neointimal coverage after stenting may result in adverse outcomes. Determinants of neointimal coverage following SES, however, are poorly understood. Methods: We evaluated 28 SES lesions using both angioscopy and intravascular ultrasound (IVUS). Degree of neointimal coverage was judged by angioscopy at follow-up (11 ± 6 months): complete/incomplete coverage, based on whether the stent struts were embedded by the neointima. Minimal stent area (MSA), external elastic membrane (EEM), lumen cross-sectional area (CSA) and plaque burden (EEM minus lumen/EEM CSA) were measured by IVUS at stent implantation. Both proximal and distal references were used. Stent expansion was assessed by stent expansion index (SEI) as MSA/reference EEM CSA. Under-expansion was defined as SEI &lt; 0.4. Incomplete apposition was defined as the lack of contact between any strut and the underlying vessel wall. Results: Complete coverage was identified in 10 (36%), and incomplete coverage in 18 (64%). Time from the stenting to angioscopy (10 ± 5 versus 11 ± 7 months, p=0.8) as well as the lesion and procedural characteristics was similar between the complete/incomplete coverage groups. IVUS parameters were also similar, except for the final MSA (7.0±1.8mm 2 in complete versus 5.3±1.9mm 2 in incomplete , p=0.02) and lumen CSA at the distal reference site (6.1±1.4mm 2 in complete versus 4.9 ±1.2mm 2 in incomplete , p= 0.02). The frequency of incomplete apposition was similar between the groups (20% in complete versus 39% in incomplete , P= 0.4); however, SEI was significantly larger in the complete coverage than in the incomplete coverage group (0.52 ± 0.11 versus 0.39 ± 0.09, p=0.002). Stent under-expansion was identified only in 2 (20%) of the complete coverage, as compared to 67% of the incomplete coverage group (P=0.046). By multivariate logistic regression analysis, large SEI was strongly associated with complete neointimal coverage (P=0.04). Conclusion: Optimal expansion of the stent is a major contributor to the complete neointimal coverage following sirolimus-eluting stent implantation.

Mechanisms of lumen narrowing of saphenous vein bypass grafts 12 months after implantation: An intravascular ultrasound study

Previous long-term (>1 year) studies have suggested that saphenous vein bypass grafts (SVGs) undergo vascular remodeling similar to native coronary arteries. However, early morphologic stages of SVG remodeling have not been characterized in vivo. Thirty SVGs were studied 12 months after implantation using an intravascular ultrasound automated pullback system. Intravascular ultrasound images were analyzed between 10 and 60 mm from the tip of the guide. Lumen area (LA), intima area (IA), and vessel area (VA, defined as the area within the outer border of a hypoechoic intimal layer) were computed at 3 cross sections: the minimum LA (MLA) site and the proximal and distal reference sites. Area changes (Delta) were calculated as the MLA site minus the average of the reference sites. In this cohort, 70% of the MLA sites had a smaller VA than the average references. On average, MLA sites had significantly smaller VA (9.7 +/- 2.9 vs 10.7 +/- 3.2 mm2, P < .01) and larger IA (2.5 +/- 2.1 vs 1.2 +/- 1.3 mm2, P < .01) than at the reference sites. The relative contribution of DeltaVA (-1.0 +/- 1.4 mm2) and DeltaIA (1.3 +/- 1.3 mm2) to lumen compromise (-2.3 +/- 1.4 mm2) were 43% and 57%, respectively. On the other hand, simple linear regression analysis revealed a significant positive correlation between DeltaIA and DeltaVA (y = -1.7 + 0.52x, r = 0.50, P < .01). Within the first year, the mechanism of lumen compromise in SVG is a combination of negative remodeling and intimal hyperplasia. Positive remodeling is seen in a minority of cases. However, the direction and extent of remodeling correlated with change in intimal thickness.

Effect of coronary risk factors on arterial compensatory enlargement in japanese middle-aged patients with de novo single-vessel disease--an intravascular ultrasound study.

Compensatory enlargement (CE) of atherosclerotic human arteries has been reported; however, the pattern of arterial remodeling in response to plaque formation is not unique. The study was undertaken to determine the extent of coronary artery compensatory enlargement at stenotic lesions and to correlate the arterial compensatory enlargement with risk factors. We studied 62 patients with stable angina and de novo single-vessel disease using intravascular ultrasound and obtained good images in 42 patients (68%). The vessel cross-sectional area (VA), lumen cross-sectional area (LA), and plaque cross-sectional area (PA) were measured at the lesion site and at proximal and distal reference sites. Positive CE was defined as increase in VA of lesion site > 10% compared with that of proximal reference site (CE group, n = 15); shrinkage was defined as reduction in VA of lesion site > 10% compared with that of proximal reference site (S group, n = 14); inadequate CE was defined as intermediate between CE and S (IE group, n = 13). All subjects had coronary risk factors measured before this study. There was no difference in VA, LA, or PA among the three groups at the proximal and distal reference sites, nor in LA at the lesion site; however, VA and PA were significantly smaller in the S group than in the other groups (p < 0.01). Of coronary risk factors, increased systolic blood pressure (SBP), increased diastolic blood pressure (DBP), and decreased high-density lipoprotein cholesterol (HDL-c) levels had the strongest association with shrinkage (p < 0.05). Hypertension and decreased HDL level may contribute to the shrinkage response in middle-aged patients with stable angina.

Vascular remodeling in atherosclerotic coronary arteries is affected by plaque composition.

Narrowing of lumen in atherosclerotic lesions is determined not solely by accumulation of plaque but also by constrictive or expansive vascular remodeling. Underlying mechanisms and determinants of these bidirectional processes are not known. To elucidate the response of vascular remodeling to progressive atherosclerosis by analyzing its potential association with composition of plaque. Seventy patients with 77 de-novo coronary artery lesions underwent intravascular ultrasound imaging before coronary intervention. Target lesions were defined as soft, fibrous/mixed, and calcified plaques. Quantitative measurements of area of lumen (A(L)), total area of vessel (A(TV)) and area of plaque (A(P) = A(TV)-A(L)) were performed at the lesion site and at the proximal and distal reference sites. Remodeling was determined by using a remodeling index [I(R) = (stenosis of A(TV)/mean reference A(TV)) x 100]. Overall vascular remodeling was balanced with a mean remodeling index of 100.2+/-19.3% and a high interlesion range (60.2-152.4%). The remodeling index for soft lesions was significantly higher than those for fibrous/mixed and calcified lesions (110+/-18.8 versus 96.2+/-14.4 and 85.9+/-15.1%, P < 0.01). Calcified lesions exhibited lower remodeling indexes than did uncalcified lesions (85.9+/-15.1 versus 104.6+/-18.4%, P < 0.01). Processes involved in vascular remodeling are affected by composition of plaque insofar as there is a higher prevalence of constrictive remodeling among calcified plaques and a higher prevalence of expansive remodeling among soft lesions. These findings indicate that constrictive remodeling is a late manifestation in atherogenesis. Future studies are warranted in order to enhance the understanding of progression of atherosclerosis, and of mechanisms of vascular remodeling and their impacts on interventional therapy.

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

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

Type and extent of vascular remodeling in significant coronary lesions: An intravascular ultrasound study

The purpose of this study was to assess the dimension of regional vascular remodeling and its influence on lumen narrowing in vivo. Sixty-three patients with 68 coronary lesions were imaged by intravascular ultrasound before transcatheter therapy. Quantitative measurements of lumen area, vessel area, and plaque area were performed at the lesion site and at the proximal and distal reference site. Area stenosis was calculated as plaque area/vessel area. 100. The extent of remodeling was quantified by a remodeling index (RI = stenosis vessel area - mean reference vessel area/mean reference vessel area. 100). Additionally, three different groups of vascular remodeling were defined: 1) positive remodeling = stenosis vessel area > maximal reference vessel area; 2) intermediate remodeling = maximal reference vessel area >/= stenosis vessel area >/= minimal reference vessel area; 3) negative remodeling = stenosis vessel area < minimal reference vessel area. In 57% of lesions stenosis vessel area was not in between the proximal and distal reference area: 29% of lesions (20/68) had positive, 28% (19/68) negative, and 43% (29/68) intermediate remodeling. Overall remodeling index averaged -0.8+/-19.7%. In the negative remodeling group, reduction of vessel area contributed to 40+/-21% of lumen narrowing, in the positive remodeling group, stenosis vessel area was 21+/-12% enlarged (p<0.001). Lesions with negative remodeling exhibit a lesser plaque area, lesions with positive remodeling a larger than other vessels (8.2+/-2.4 mm(2), 13.8+/-3.7 mm(2), 10. 8+/-3.7 mm(2); p <0.001). Distinct vascular remodeling occurred in the majority of atherosclerotic lesions and is a bidirectional process. Overall, the extent and the frequency of positive and negative remodeling was almost balanced. In lesions with negative remodeling the plaque area was significantly lesser than in other lesions.

Coronary artery disease: arterial remodelling and clinical presentation

OBJECTIVETo investigate the hypothesis that in coronary artery disease large plaques in compensatorily enlarged segments are associated with acute coronary syndromes, whereas smaller plaques in shrunken segments are associated with...

Intravascular Ultrasound Evidence for Coarctation Causing Symptomatic Renal Artery Stenosis

A recent study of human cadaveric renal arteries revealed that renal artery narrowing could be due not only to atherosclerotic plaque compensated for by adaptive remodeling, but also to hitherto undescribed focal narrowing of an otherwise normal renal arterial wall (ie, coarctation). The present study investigated whether vessel coarctation could be identified in patients with symptomatic renal artery stenosis (RAS). Consecutive symptomatic patients with angiographically proven atherosclerotic RAS who were referred for stent placement were studied by 30-MHz intravascular ultrasound before intervention (n=18) or after predilatation (n=18). Analysis included assessment of the media-bounded area and plaque area (PLA) at the most stenotic site and at a distal reference site (most distal cross-section in the main renal artery with normal appearance). Coarctation was considered present whenever the target/reference media-bounded area was </=85%. Before intervention, coarctation was observed in 9 of 18 patients and adaptive remodeling in 9 of 18 patients. Coarctation lesions had a significantly smaller PLA than adaptive remodeled lesions (P=0.001). Similarly, despite predilatation, coarctation was seen in 8 of 18 patients who had significantly smaller PLAs (P=0. 008) when compared with those patients who had adaptive remodeled lesions. No differences in severity of RAS or angiographic or clinical parameters were observed. Low-plaque coarctation may cause a considerable proportion of symptomatic RAS, which is angiographically and clinically indistinguishable from plaque-rich RAS.

How Should We Define Inadequate Coronary Arterial Remodeling?

To the Editor: After our report1 showing the contribution of “inadequate compensatory enlargement” to the development of coronary narrowing, Mintz et al2 in their recently published report confirmed this concept in a larger study population by using a different definition of “inadequate arterial remodeling.” However, the assessment of the relative importance of “inadequate arterial remodeling” is highly dependent on the definition used. As pointed out by Mintz et al, the assessment of the true effect of vessel remodeling on the progression of coronary narrowing would require serial or longitudinal intravascular ultrasound studies (IVUS) over a long time period. However, such longitudinal, serial studies are time consuming and impractical. Consequently, we compared the size of the external elastic lamina (EEL) area (the area within the outer border of the sonolucent zone considered to represent EEL) at the lesion site with those at the reference sites. The proximal and distal reference sites were defined as the sites with minimal narrowing by angiography and the largest lumen area and <50% area stenosis as determined by IVUS. In our study,1 the EEL area of all arteries was larger at the proximal reference sites than at the distal reference sites, and “inadequate compensatory enlargement” was defined …

Mechanism of luminal narrowing in cardiac allograft vasculopathy: Inadequate vascular remodeling rather than intimal hyperplasia is the major predictor of coronary artery stenosis

Background: Despite increasing knowledge about degree and distribution pattern of intimal hyperplasia in cardiac allograft vasculopathy, coronary artery remodeling is only poorly understood in this disease. Methods: To evaluate vascular geometry, intravascular ultrasound was used to characterize 57 advanced lesions in 35 consecutive transplant recipients. Lumen, plaque, and vessel area in these target lesions were compared with proximal and distal reference sites. Results and Conclusions: Vascular remodeling by compensatory local vessel enlargement (positive remodeling) and circumscript vascular constriction (negative remodeling) could be demonstrated. Plaque area in stenotic lesions was significantly increased compared with the mean reference site (5.6 ± 3.0 mm 2 versus 2.8 ± 1.5 mm 2, p < 0.001); however, inadequate compensatory enlargement rather than intimal hyperplasia was shown to be the most important predictor of luminal obstruction ( r = 0.77, p < 0.001). (Am Heart J 1998;135:628-33.)

Discrepancy between stent deployment and balloon size used assessed by intravascular ultrasound

This study was designed to assess the discrepancy in stent deployment seen on intravascular ultrasound and its relation to the balloon size selected for stent delivery. Prospective study. The study group comprised 27 patients treated using a stent (n = 18) or stent-graft combination (n = 9). Following angiographically optimal stent deployment (< 10% residual stenosis) intravascular ultrasound was used to compare the smallest intra-stent lumen area with measurements at both stent edges and the lumen area of the proximal and distal reference sites. In 14 of the 27 stents the intra-stent dimension was the same as the dimension of the stent edge (difference < or = +/- 10%). Of the remaining stents the intra-stent dimension was smaller (difference > 10%) than the proximal stent edge in seven stents (range 11-39%), smaller than the distal stent edge in three stents (range 11-20%) and smaller than both stent edges in three stents (range 12-37%). Both in patients treated with a stent or stent-graft combination, the resulting smallest intra-stent lumen area was smaller than the balloon size used (mean difference 32% and 42%, respectively) and smaller than the mean lumen area of the reference sites (mean difference 25% and 23%, respectively). This intravascular ultrasound study shows a discrepancy between intra-stent lumen area, the area of the stent edges and the balloon size used.

Successful Directional Atherectomy of De Novo Coronary Lesions Assessed With Three-Dimensional Intravascular Ultrasound and Angiographic Follow-Up

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