No relationship between compensatory arterial remodeling of focal stenotic atherosclerotic lesions and tortuosity of the arterial segment involved.
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Coronary Artery Disease↗
Biomedical subjects
P J Fitzgerald
Publications and source records attributed to P J Fitzgerald.
The renaissance of directional coronary atherectomy: a second look from the inside.
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Angioplasty, Balloon, Coronary↗
Longitudinal plaque redistribution during stent expansion.
The purpose of this study was to clarify the 3-dimensional behavior of plaque during coronary stent expansion. Serial intravascular ultrasound (IVUS) studies, preintervention, and poststenting were evaluated in 32 patients treated with a single-balloon expandable tubular stent. External elastic membrane (EEM), lumen, stent, and plaque + media cross-sectional area were measured at 1-mm intervals through the entire stent as well as proximal and distal reference segments 5 mm from the stent edge. Volumetric calculations were based on Simpson's rule. Overall, the plaque + media volume through the entire lesion did not change during stent expansion (218 +/- 51 vs 217 +/- 47 mm3, p = 0.69). However, EEM and lumen volume increased significantly (EEM volume, 391 +/- 84 vs 448 +/- 87 mm3 [p < 0.0001]; lumen volume, 173 +/- 52 vs 231 +/- 54 mm3 [p < 0.0001]). The change in lumen volume correlated strongly with the change in EEM volume (r = 0.85, p < 0.0001), but poorly with the change in plaque + media volume (r = 0.37, p = 0.03). Plaque + media volume decreased in the midstent zone (59 +/- 14 vs 53 +/- 11 mm3, p = 0.0005), and increased in the distal stent zone (40 +/- 11 vs 44 +/- 9 mm3, p = 0.003), but did not change in either the proximal stent zone or reference segments. The mechanism of stent expansion is a combination of vessel stretch and plaque redistribution, translating disease accumulation from the midstent zone to the distal stent zone.
Angioplasty, Balloon, Coronary↗
Feasibility of a novel blood noise reduction algorithm to enhance reproducibility of ultra-high-frequency intravascular ultrasound images.
BACKGROUND: Ultra-high-frequency (40- to 50-MHz) intravascular ultrasound (IVUS) improves image quality compared with conventional 20- to 30-MHz IVUS. However, as the frequency of IVUS increases, high-intensity backscatter from blood components may cause visual difficulties in discrimination between the lumen and arterial wall structure. The purpose of this study was to evaluate the effect of a novel blood noise reduction algorithm (BNR) on quantitative coronary ultrasound measurements. METHODS AND RESULTS: IVUS studies using a 40-MHz transducer were performed in 35 patients with coronary artery disease. A total of 620 gray-scale images (310 pairs) were processed with and without the BNR, and lumen cross-sectional area (CSA) was determined by 2 independent observers. With the BNR, the intraobserver and interobserver correlation coefficients for lumen CSA were significantly improved (0.85 to 0.99 and 0.80 to 0.98, respectively). In the 270 images (135 pairs) in which vessel wall measurements were possible, the BNR significantly improved the intraobserver and interobserver correlation coefficients for plaque plus media CSA (0.83 to 0.99 and 0.76 to 0.97, respectively), whereas no influence was observed for external elastic membrane CSA (1.00 to 1.00 and 0.99 to 0.99, respectively). CONCLUSIONS: This study demonstrates the feasibility of this novel algorithm to reduce blood noise, thereby enabling accurate lumen border delineation and providing reproducible measurements of both the lumen and plaque plus media CSAs. Incorporating a digital BNR may serve as an important adjunct to ultra-high-frequency IVUS imaging for improving accurate quantitative evaluation of vessel dimensions.
Algorithms↗
Inhibition of restenosis with beta-emitting radiotherapy: Report of the Proliferation Reduction with Vascular Energy Trial (PREVENT).
BACKGROUND: Intracoronary gamma- and beta-radiation have reduced restenosis in animal models. In the clinical setting, the effectiveness of beta-emitters has not been studied in a broad spectrum of patients, particularly those receiving stents. METHODS AND RESULTS: A prospective, randomized, sham-controlled study of intracoronary radiotherapy with the beta-emitting (32)P source wire, using a centering catheter and automated source delivery unit, was conducted. A total of 105 patients with de novo (70%) or restenotic (30%) lesions who were treated by stenting (61%) or balloon angioplasty (39%) received 0 (control), 16, 20, or 24 Gy to a depth of 1 mm in the artery wall. Angiography at 6 months showed a target site late loss index of 11+/-36% in radiotherapy patients versus 55+/-30% in controls (P:<0.0001). A low late loss index was seen in stented and balloon-treated patients and was similar across the 16, 20, and 24 Gy radiotherapy groups. Restenosis (>/=50%) rates were significantly lower in radiotherapy patients at the target site (8% versus 39%; P:=0.012) and at target site plus adjacent segments (22% versus 50%; P:=0.018). Target lesion revascularization was needed in 5 radiotherapy patients (6%) and 6 controls (24%; P:<0.05). Stenosis adjacent to the target site and late thrombotic events reduced the overall clinical benefit of radiotherapy. CONCLUSIONS: beta-radiotherapy with a centered (32)P source is safe and highly effective in inhibiting restenosis at the target site after stent or balloon angioplasty. However, minimizing edge narrowing and late thrombotic events must be accomplished to maximize the clinical benefit of this modality.
Angioplasty, Balloon, Coronary↗
Final results of the Can Routine Ultrasound Influence Stent Expansion (CRUISE) study.
BACKGROUND: Intravascular ultrasound (IVUS) can assess stent geometry more accurately than angiography. Several studies have demonstrated that the degree of stent expansion as measured by IVUS directly correlated to clinical outcome. However, it is unclear if routine ultrasound guidance of stent implantation improves clinical outcome as compared with angiographic guidance alone. METHODS AND RESULTS: The CRUISE (Can Routine Ultrasound Influence Stent Expansion) study, a multicenter study IVUS substudy of the Stent Anti-thrombotic Regimen Study, was designed to assess the impact of IVUS on stent deployment in the high-pressure era. Nine centers were prospectively assigned to stent deployment with the use of ultrasound guidance and 7 centers to angiographic guidance alone with documentary (blinded) IVUS at the conclusion of the procedure. A total of 525 patients were enrolled with completed quantitative coronary angiography, quantitative coronary ultrasound, and clinical events adjudicated at 9 months for 499 patients. The IVUS-guided group had a larger minimal lumen diameter (2.9+/-0.4 versus 2.7+/-0. 5 mm, P<0.001) by quantitative coronary angiography and a larger minimal stent area (7.78+/-1.72 versus 7.06+/-2.13 mm(2), P<0.001) by quantitative coronary ultrasound. Target vessel revascularization, defined as clinically driven repeat interventional or surgical therapy of the index vessel at 9 month-follow-up, occurred significantly less frequently in the IVUS-guided group (8.5% versus 15.3%, P<0.05; relative reduction of 44%). CONCLUSIONS: These data suggest that ultrasound guidance of stent implantation may result in more effective stent expansion compared with angiographic guidance alone.
Aspirin↗
Determinants of coronary remodeling in transplant coronary disease: a simultaneous intravascular ultrasound and Doppler flow study.
BACKGROUND: Coronary remodeling plays a significant role in lumen loss in transplant allograft vasculopathy (TxCAD), but the determinants of remodeling are unknown. We assessed the relationship between remodeling and plaque topography, coronary compliance, and blood flow in TxCAD. METHODS AND RESULTS: One artery in each of 27 transplant patients was investigated with simultaneous intravascular ultrasound and coronary flow measurements (basal and hyperemic by Doppler flow wire). At 4 to 8 different cross sections (mean 5.1+/-1. 2), plaque topography (concentric or eccentric) was determined, and total vessel area, lumen area, and intimal/medial area (IMA) were measured. Mean remodeling ratio (vessel area/IMA) in eccentric lesions (E, n=28) was significantly larger than that in concentric lesions (C, n=70) (E 5.87+/-0.93 versus C 3.58+/-0.62; P<0.001), despite similar IMA (E 3.89+/-0.68 versus C 3.90+/-0.41; P=NS) and distribution of imaged segments. Remodeling ratio was consistently larger in eccentric lesions in all 3 vessel segments when analyzed separately, and mean remodeling ratio for each artery was larger in vessels with predominantly eccentric lesions. Coronary compliance ([Delta lumen area/diastolic lumen area]/Delta mean arterial pressure x 10(3)) was also significantly greater in eccentric lesions versus concentric lesions (proximal 1.00+/-0.39 versus 0.22+/-0.04; mid 0.71+/-0.17 versus 0.21+/-0.10; distal 0.43+/-0.13 versus 0. 01+/-0.08; all P<0.01). Coronary flow reserve was also significantly higher in coronary arteries with primarily eccentric lesions (E 2. 49+/-0.64 versus C 1.87+/-0.28; P<0.01). CONCLUSIONS: Vessel remodeling in transplant vasculopathy is significantly greater in eccentric lesions than in concentric lesions, possibly due to greater coronary compliance and resistive vessel function.
Compliance↗
Acute myocardial infarction and vascular remodeling.
We used intravascular ultrasound to show that outward remodeling predominates in lesions responsible for acute myocardial infarction, whereas negative remodeling is far more prevalent in lesions responsible for chronic stable angina. The total cholesterol:high-density lipoprotein ratio was also strongly correlated with outward remodeling.
Aged↗
Attention modulates synchronized neuronal firing in primate somatosensory cortex.
A potentially powerful information processing strategy in the brain is to take advantage of the temporal structure of neuronal spike trains. An increase in synchrony within the neural representation of an object or location increases the efficacy of that neural representation at the next synaptic stage in the brain; thus, increasing synchrony is a candidate for the neural correlate of attentional selection. We investigated the synchronous firing of pairs of neurons in the secondary somatosensory cortex (SII) of three monkeys trained to switch attention between a visual task and a tactile discrimination task. We found that most neuron pairs in SII cortex fired synchronously and, furthermore, that the degree of synchrony was affected by the monkey's attentional state. In the monkey performing the most difficult task, 35% of neuron pairs that fired synchronously changed their degree of synchrony when the monkey switched attention between the tactile and visual tasks. Synchrony increased in 80% and decreased in 20% of neuron pairs affected by attention.
Action Potentials↗
Accentuated remodeling on the upstream side of atherosclerotic lesions.
Although it has been postulated that atherosclerotic stenotic lesions cannot remodel in response to altered flow, evidence to support or refute this hypothesis has been elusive. In vitro models have shown that accelerated endothelial shear stress occurs on the upstream side of stenoses, while turbulent lower shear stress is seen on the downstream side. We therefore compared vascular remodeling at paired sites 2 mm upstream and 2 mm downstream of the site of minimal lumen area in 25 atherosclerotic lesions in 23 patients using intravascular ultrasound. Remodeling was compared by 2 methods: normalized vessel area (vessel area(lesion)/vessel(reference) and remodeling index (change in vessel area/change in plaque area from reference). Normalized vessel area was significantly greater upstream than downstream (1.21+/-0.06 vs. 1.12+/-0.09; p<0.05), despite similar plaque burden (8.84+/-0.81 vs. 8.42+/-0.85 mm2) resulting in larger lumen area (8.15+/-1.02 vs. 6.10+/-0.88 mm2; p<0.05). Remodeling index was also significantly higher upstream than downstream (0.67+/-0.20 vs. 0.12+/-0.24, respectively, p<0.05). Accentuation of remodeling on the upstream side was significantly correlated (r = 0.54, p = 0.01) with the mean degree of shear acceleration expected by stenosis severity. Impaired remodeling on the downstream side may partly explain stenosis propagation down a vessel.
Coronary Artery Disease↗
Comparison of coronary stent expansion by intravascular ultrasonic imaging in younger versus older patients with diabetes mellitus.
The poor long-term outcome in young diabetic patients receiving stents is not well understood. The purpose of this study was to characterize the pastprocedural results of stent placement in diabetic patients using intravascular ultrasound to identify factors that might be associated with poor clinical outcome. The acute dimensions from intravascular ultrasound studies after stent deployment at 5 sites were measured from 39 coronary segments from patients with diabetes mellitus (DM) and 161 segments from nondiabetic patients (non-DM). Within these 2 groups, segments were subgrouped into young (y) and old (o) in reference to the mean study age of 64 years, forming 4 groups: yDM (n = 20), y non-DM (n = 65), oDM (n = 19), and o non-DM (n = 96). Results are reported as mean +/- 1 SD. Diabetic patients had smaller mean lumen area within the treated segment than o non-DM (8.37+/-2.59 vs. 9.11+/-3.35 mm2, p<0.01). These differences were more pronounced at the distal reference vessel lumen of yDM than y non-DM (7.6+/-2.3 vs. 10.3+/-4.5 mm2, p<0.003), and were associated with greater percent plaque area in the distal reference vessel (43.4+/-13% vs. 34.1+/-11.2%, p<0.003). In young diabetic patients undergoing elective stent placement, underexpansion of the stented segment is common, which may contribute to the relatively poor long-term outcome in these patients. We suggest that when stenting is the procedure of choice in this subgroup of high-risk patients, special attention should be given to optimizing lumen dimensions.
Age Factors↗
Effects of intravenous and intracoronary adenosine 5'-triphosphate as compared with adenosine on coronary flow and pressure dynamics.
BACKGROUND: Measurements of Doppler derived coronary flow reserve (CFR) and pressure derived fractional flow reserve (FFR) for coronary stenosis assessment depend on the induction of maximal hyperemia. Adenosine is the most widely used pharmacological agent but is expensive and poorly tolerated by some patients. METHODS AND RESULTS: The objective of this study was to test the equivalency of adenosine 5'-triphosphate (ATP) to adenosine in their ability to cause maximal hyperemia as compared with the hyperemic response of complete coronary occlusion in 6 canines. Intracoronary administration of either ATP or adenosine resulted in a significant increase in CFR (2.79+/-0.64 and 2.22+/-0.7 for 10 microgram versus 4. 65+/-1.22 and 4.25+/-0.78 for 100 microgram for ATP and adenosine, respectively, P for trend <0.001) but not reaching the level of coronary occlusion (6.35+/-2.26). Additionally, FFR and CFR were measured in 35 different stenoses using ATP, adenosine, and coronary occlusion. There was an excellent linear correlation between ATP and adenosine for both CFR (R=0.934, P<0.001) and FFR (R=0.985, P<0.001). However, hyperemia with either ATP or adenosine was less than postocclusion hyperemia, resulting in significantly different reserve measurements (CFR: 1.93+/-0.66 and 2.08+/-0.81 versus 2.35+/-0.97, P<0.001; FFR: 0.62+/-0.24 and 0.63+/-0.23 versus 0.58+/-0.2, P<0.001). CONCLUSIONS: 1) Step up in dosage of ATP and adenosine beyond currently recommended clinical doses resulted in a significant increase in coronary hyperemia; 2) ATP was equivalent to adenosine for both CFR and FFR; and 3) complete coronary occlusion yielded a better hyperemic response than either drug, indicating that maximal hyperemia was not achieved by either pharmacological stimulus.
Adenosine↗
Selective regional myocardial infiltration by the percutaneous coronary venous route: A novel technique for local drug delivery.
Recent advances in the treatment of heart disease, in particular cardiovascular gene therapy and therapeutic angiogenesis, highlight the need for efficient and practical local delivery methods for the heart. We assessed the feasibility of percutaneous selective coronary venous cannulation and injection as a novel approach to local myocardial drug delivery. In anesthetized swine, the coronary sinus was cannulated percutaneously and a balloon-tipped catheter advanced to the anterior interventricular vein (AIV) or middle cardiac vein (MCV). During balloon occlusion, venous injection of radiographic contrast caused regional infiltration of targeted myocardial regions. Complete AIV occlusion had no impact on LAD flow parameters. Videodensitometric analysis following venous injection showed that radiographic contrast persisted for at least 30 min. Selective regional myocardial infiltration is feasible by this approach, targeting selected myocardial beds, including the apex, anterior wall, septum, and inferoposterior wall. This novel technique has potential application for local myocardial drug or growth factor delivery. Cathet. Cardiovasc. Intervent. 51:358-363, 2000.
Animals↗
Coronary calcification: assessment by intravascular ultrasound imaging.
The role of intralesional coronary calcification is not only an important prognostic factor with respect to interventions, but can be extremely important with respect to diagnostic classification of lesion subsets. Intravascular ultrasound details the relationship between plaque and vessel wall in real time throughout the coronary arterial tree. This provides the opportunity to exactly define not only the quantity but also the distribution of calcium within the vessel wall. This is particularly important from a diagnostic standpoint, as plaque-containing calcification can often lead to ambiguous or erroneous angiographic information. Being able to classify different plaque substructures with intravascular ultrasound can help not only to clarify the ambiguous angiogram but delineate the exact nature of luminal encroachment. From a treatment standpoint, the identification of calcification patterns, particularly those on the superficial intimal surface, can alert the operator to change the compliance prior to definitive therapy. High-speed rotational atherectomy is a technique that provides significant de-calcification in preparation for optimizing the stent geometry within such lesion subsets. Although electron beam computed tomography can accurately locate calcification patterns within the coronary tree in a non-invasive manner, it's often difficult to know the extent of calcification and the relationship to fibrofatty plaques. Intravascular ultrasound albeit invasive, provides the opportunity to delineate these plaque substructures and potentially identify lesion subsets that may have an important natural history in the development of coronary atherosclerosis.
Atherectomy, Coronary↗
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.
Aged↗
Automated contour detection for high-frequency intravascular ultrasound imaging: a technique with blood noise reduction for edge enhancement.
Automated edge detection may standardize measurements among observers, providing for rapid assessment of intravascular ultrasound (IVUS) images. However, with high frequency images, enhanced blood signals make it difficult to define and trace the lumen borders. Accordingly, we evaluated a fully automated contour analysis facilitated with a blood noise reduction algorithm (BNR) for 40-MHz IVUS images in human coronary arteries of 27 patients. This algorithm is based on the principle that blood echo speckles have higher temporal and spatial variations than the arterial wall. A total of 193 paired lumen areas and 78 external elastic membrane (EEM) areas were measured and compared. Automated measurements showed good agreement with manual tracings for lumen and EEM area, with high correlation coefficients (0.945 and 0.950, respectively) and small variability (0.4 +/- 14.4% and 0.6 +/- 9.7%, respectively). This preliminary finding suggests that automated contour detection facilitated with BNR appeared to be a feasible and reliable technique for area measurements in 40-MHz IVUS imaging.
Blood↗
Tissue characterization of atherosclerotic plaques by intravascular ultrasound radiofrequency signal analysis: an in vitro study of human coronary arteries.
BACKGROUND: Conventional gray-scale images of intravascular ultrasound (IVUS) cannot accurately differentiate histologic subtypes of sonolucent coronary plaques with or without a lipid core. METHODS: We analyzed radiofrequency signals obtained in vitro from 24 regions of interest (ROI) of noncalcified (sonolucent) plaques in 10 atherosclerotic coronary artery specimens pressure-fixed by formalin. Radiofrequency signals were sampled with a 30-MHz IVUS catheter and digitized at 500 MHz in 8-bit resolution. The ROIs were histologically categorized into 12 plaques with a lipid core and 12 plaques without it. Integrated backscatter and statistical parameters of the radiofrequency envelope (mean/SD ratio [MSR], skewness, and kurtosis) within the ROI were calculated offline, and their ability to detect a lipid core was compared with visual analysis of the IVUS video images. In the group with lipid cores, percent area of a lipid core in each ROI was measured in a digitized histologic image by a computerized planimeter. RESULTS: Sensitivity and specificity of MSR, skewness, and kurtosis for lipid core detection were substantially greater than visual video image analysis (83.3% and 91.7%, 100% and 91.7%, 100% and 91.7% vs 53.3% and 71.7%). Furthermore, the parameters of integrated backscatter, MSR, skewness, and kurtosis were significantly correlated to percent of core area (r = -0.64, -0.73, 0.78, and 0.63, respectively; P<.05). CONCLUSIONS: Compared with IVUS video images, the parameters of radiofrequency signal analysis may be used to aid in more accurate detection and quantitative evaluation of a lipid core, which is one of the major factors of a vulnerable coronary plaque.
Coronary Artery Disease↗
Adequacy of intracoronary versus intravenous adenosine-induced maximal coronary hyperemia for fractional flow reserve measurements.
BACKGROUND: Fractional flow reserve (FFR) is a measure of coronary stenosis severity that is based on pressure measurements obtained at maximal hyperemia. The most widely used pharmacologic stimulus for maximal coronary hyperemia is adenosine, administered either as a continuous intravenous (IV) infusion or intracoronary (IC) bolus. IV adenosine has more side effects and is more costly than IC adenosine but has a more stable and prolonged hyperemic effect. METHODS: We compared the efficacy of IC and IV adenosine administration for the measurement of FFR in a multicenter trial. Fifty-two patients with 60 lesions underwent determination of FFR with both IV and IC adenosine. IV adenosine was administered as a continuous infusion at a rate of 140 microgram/kg per minute until a steady state hyperemia was achieved. IC adenosine boluses were administered at a dose of 15 to 20 microgram in the right and 18 to 24 microgram in the left coronary artery. FFR was calculated as the ratio of the distal coronary pressure (from pressure guide wire) to the aortic pressure (guide catheter) at maximal hyperemia. RESULTS: A total of 26 left anterior descending, 23 right, 9 left circumflex, and 3 left main coronary arteries were evaluated. Mean percent stenosis for both groups was 55.8% +/- 23.6% (range 0% to 95%), and mean FFR was 0.78 +/- 0.15 (range 0.41 to 0.98). There was a strong and linear correlation between FFR measurements with IV and IC adenosine (R = 0.978, y = 0. 032 + 0.964x, P <.001). The agreement between the 2 sets of measurements was also high, with a mean difference in FFR of -0.004 +/- 0.03. However, a small random scatter in both directions of FFR measurements was noted with 5 lesions (8.3%) where FFR with IC adenosine was higher by 0.05 or more compared with IV infusions, suggesting a suboptimal hyperemic response in these patients. Changes in heart rate and blood pressure were significantly higher with IV adenosine. Two patients with IV, but none with IC adenosine, had severe side effects (bronchospasm and severe nausea). CONCLUSION: These results suggest that IC adenosine is equivalent to IV infusion for the determination of FFR in the majority of patients. However, in a small percentage of cases, coronary hyperemia was suboptimal with IC adenosine.
Adenosine↗