Remodeling after directional coronary atherectomy (with and without adjunct percutaneous transluminal coronary angioplasty): a serial angiographic and intravascular ultrasound analysis from the Optimal Atherectomy Restenosis Study

Novel strategy for ostial left anterior descending artery acute myocardial infarction: Combined treatment with directional coronary atherectomy followed by drug-coated balloon angioplasty

A 69-year-old female diagnosed with ostial left anterior descending artery acute myocardial infarction underwent percutaneous coronary intervention using combined directional coronary atherectomy followed by drug-coated balloon angioplasty. This report highlights a novel management strategy with no permanent scaffold left in the coronary artery.

Disease progression in nonintervened saphenous vein graft segments a serial intravascular ultrasound analysis

OBJECTIVES

We used serial intravascular ultrasound (IVUS) to assess disease progression in nonintervened saphenous vein graft (SVG) segments to determine the natural rate of disease progression in SVG.

BACKGROUND

There are no serial IVUS studies of disease progression or luminal compromise in SVGs.

METHODS

We assessed serial (baseline and follow-up at 16.2 +/- 7.4 months) IVUS findings in 50 nonintervened SVG segments in 44 patients. The SVG age was 13.5 +/- 3.6 years.

RESULTS

Overall, from baseline to follow-up, plaque area increased (Delta = +0.58 +/- 1.25 mm(2), p = 0.003), and SVG and minimum lumen area (MLA) decreased (Delta = -0.50 +/- 1.14 mm(2), p = 0.002, and Delta = -1.08 +/- 1.28 mm(2), p < 0.001, respectively). The MLA decreased in 34 lesions (Delta = -1.67 +/- 1.08 mm(2)), and MLA increased in 16 lesions (Delta = +0.19 +/- 0.47 mm(2)). Compared with lesions with an increase in MLA, lesions with a decrease in MLA were associated with: 1) larger baseline SVG and plaque areas and plaque burden (15.57 +/- 3.90 mm(2) vs. 11.55 +/- 2.30 mm(2), p < 0.001; 7.97 +/- 3.77 mm(2) vs. 4.27 +/- 1.92 mm(2), p < 0.001; and 48.7 +/- 14.2% vs. 36.0 +/- 13.4%, p = 0.004, respectively); and 2) a greater decrease in SVG area (Delta = -0.96 +/- 1.05 mm(2) vs. +0.48 +/- 0.58 mm(2), p < 0.001) and greater increase in plaque area (Delta = +0.71 +/- 1.47 mm(2) vs. +0.29 +/- 0.45 mm(2), p < 0.001). The DeltaMLA correlated with both Deltaplaque area (r = -0.589, p < 0.001) and DeltaSVG area (r = 0.470, p = 0.001), and Deltaplaque area correlated with DeltaSVG area (r = 0.436, p = 0.002). There were linear relations between both the Deltaplaque area (r = 0.519, p < 0.001) and Deltalumen area (r = -0.500, p < 0.001) versus follow-up low-density lipoprotein (LDL) cholesterol; a follow-up LDL cholesterol of 100 mg/dl predicted no plaque increase.

CONCLUSIONS

Lumen loss in nonintervened SVG segments correlated with an increase in plaque area and a decrease in SVG area (plaque growth and negative remodeling) with a linear relationship between plaque growth versus follow-up LDL cholesterol leading to long-term lumen loss.

Regulation of arterial remodeling and angiogenesis by urokinase-type plasminogen activatorThis article is one of a selection of papers from the NATO Advanced Research Workshop on Translational Knowledge for Heart Health (published in part 2 of a 2-part Special Issue)

A wide variety of disorders are associated with an imbalance in the plasminogen activator system, including inflammatory diseases, atherosclerosis, intimal hyperplasia, the response mechanism to vascular injury, and restenosis. Urokinase-type plasminogen activator (uPA) is a multifunctional protein that in addition to its fibrinolytic and matrix degradation capabilities also affects growth factor bioavailability, cytokine modulation, receptor shedding, cell migration and proliferation, phenotypic modulation, protein expression, and cascade activation of proteases, inhibitors, receptors, and modulators. uPA is the crucial protein for neointimal growth and vascular remodeling. Moreover, it was recently shown to be implicated in the stimulation of angiogenesis, which makes it a promising multipurpose therapeutic target. This review is focused on the mechanisms by which uPA can regulate arterial remodeling, angiogenesis, and cell migration and proliferation after arterial injury and the means by which it modulates gene expression in vascular cells. The role of domain specificity of urokinase in these processes is also discussed.

In vivovalidation of a novel semi-automated method for border detection in intravascular ultrasound images

The aim of this work was to evaluate a new semi-automated intravascular ultrasound (IVUS) border detection method. The method was used to identify the lumen and the external elastic membrane or the borders of stents in 80 IVUS images, randomly selected from 10 consecutive human coronary arteries. These semi-automated results were compared with observations of two experts. Several indices in each case were obtained in order fully to evaluate the method. The time required for identification of the borders was also recorded. The interobserver variability of the method ranged from 1.21% to 5.61%, the correlation coefficient from 0.98 to 0.99, the slope was close to unity (0.94-1.03), the y intercept close to zero and the Williams index value was close to unity (range 0.67-0.91). The time (mean+/-SD) required for the method to identify the borders of the different vessel layers for the whole IVUS sequence was 5.2+/-0.2 min. The results demonstrate that the method is reliable and capable of identifying rapidly and accurately the different vessel layers depicted in IVUS images.

Stenting after directional coronary atherectomy compared with directional coronary atherectomy alone and stenting alone: a serial intravascular ultrasound study

BACKGROUND

Directional coronary atherectomy prior to stent implantation (DCA-stent) is expected to be an effective approach to reduce restenosis. The purpose of this study was to determine whether DCA-stent has advantages over DCA alone or stenting alone using serial intravascular ultrasound (IVUS).

METHODS AND RESULTS

Serial (pre-, post- and follow-up) IVUS was performed in 187 native coronary lesions treated with each of the 3 strategies. External elastic membrane cross-sectional area (CSA), lumen CSA and plaque CSA were measured. Baseline characteristics were similar. Postprocedural lumen CSA was largest after DCA-stent (11.2+/-2.7 mm2) and DCA (10.8+/-2.5 mm2) than stenting alone (9.0+/-2.9 mm2) (p<0.0005). Follow-up lumen loss was similar. As a result, follow-up lumen CSA was largest after DCA-stent (DCA-stent: 9.1+/-3.4 mm2, DCA: 7.8+/-4.2 mm2, stent: 6.3+/-2.6 mm2, p<0.0005). There was a trend toward a lower rate of restenosis with DCA-stent (DCA-stent, 12.5%; DCA, 18.3%; stent, 18.8%; p=0.57).

CONCLUSIONS

DCA-stent is superior to both DCA alone and stent alone in terms of the ability to gain a larger lumen as assessed by IVUS.

Comparison of directional coronary atherectomy and stenting versus stenting alone for the treatment of de novo and restenotic coronary artery narrowing

Late lumen loss after directional coronary atherectomy (DCA) is mainly determined by arterial remodeling. We hypothesized that stent implantation after optimal lesion debulking could be an effective approach to reduce restenosis. A total of 753 patients with de novo or restenotic coronary lesions were prospectively randomized to DCA plus stenting (n = 381) or stenting alone (n = 372). The patients were followed for 12 months. Procedural success was achieved in 91.5% versus 97.3% (p = 0.0007) of patients treated with DCA plus stent versus stent alone. Optimal atherectomy (<20% residual stenosis) was achieved in 26.5% of patients. The final minimal luminal diameter and the acute gain were similar in the 2 groups. There was no increase in 30-day major adverse cardiac events in the DCA plus stent group (3.9% vs 2.4%, p = 0.30). The primary end point, angiographic restenosis at 8 months, occurred in 26.7% of patients treated with DCA plus stents and in 22.1% of patients treated with stents alone (p = 0.237). Clinical follow-up to 1 year showed no difference in mortality (1.3% vs 0.8%, p = 0.725), acute myocardial infarction (4.2% vs 3.5%, p = 0.706), and target vessel failure (composite of death, Q-wave myocardial infarction, and target vessel revascularization) (23.9% vs 21.5%, p = 0.487) between patients with DCA plus stents and those with stents alone. This study failed to support the hypothesis that DCA before stenting lowers the angiographic restenosis rate compared with stents alone. At 12-month follow-up, there were no significant differences between the 2 groups in rates of death, reinfarction, or target vessel failure.

Quantitative angiographic and intravascular ultrasound study >5 years after directional coronary atherectomy

Aggressive and optimal directional coronary atherectomy (DCA) using intravascular ultrasound (IVUS) guidance provides favorable outcomes within 1 year. However, no previous data are available on the changes that occur in target lesions for the long term after stand-alone DCA. This study's aim evaluates, using quantitative angiography and intravascular ultrasonography, the natural history of changes that occur in target lesions between short- (about 6 months) and long-term (>5 years) follow-up angiography after stand-alone DCA. Of 186 patients (221 lesions) with successful stand-alone DCA, 48 patients (53 lesions) underwent revascularization within 6 months, and 14 patients subsequently died, leaving a study population of 124 patients (154 lesions). Complete quantitative coronary angiography (QCA) was obtained in 91 patients (101 lesions) and complete serial IVUS assessment was obtained for 38 lesions before and after intervention and during follow-up. From short- to long-term follow-up angiography, the minimal luminal diameter significantly increased (from 2.12 to 2.56 mm; p <0.0001); lesion subgroups with >30% diameter stenosis at short-term follow-up angiography showed significant late regression as assessed by QCA. Serial IVUS assessment revealed that the vessel cross-sectional area did not change (from 17.3 to 17.4 mm(2); p = NS); however the lumen cross-sectional area significantly increased (from 7.3 to 9.5 mm(2); p <0.0001) due to the reduction of plaque plus media cross-sectional area (from 10.0 to 7.9 mm(2); p <0.0001). The change in lumen cross-sectional area correlated with the change in plaque plus media cross-sectional area (r = -0.686, p <0.0001). Target lesions show late regression due to plaque reduction at >5 years after stand-alone DCA.

Incidence, Mechanism, Predictors, and Long-Term Prognosis of Late Stent Malapposition After Bare-Metal Stent Implantation

BACKGROUND

Predictors and long-term prognosis of late stent malapposition (LSM) after bare-metal stent (BMS) implantation are unknown.

METHODS AND RESULTS

We evaluated the incidence, mechanisms, predictors, and long-term prognosis of LSM after BMS implantation in 881 patients (992 native lesions) in whom intravascular ultrasound was performed at index and 6-month follow-up. LSM was defined as a separation of stent struts from the intimal surface of the arterial wall that was not presented at stent implantation. LSM occurred in 54 patients with 54 lesions (5.4% overall); the incidence was 10.3% (9 of 87) after directional coronary atherectomy (DCA) before stenting and 11.5% (11 of 96) after primary stenting in acute myocardial infarction (P=0.031 and P=0.007, respectively, versus elective stenting with conventional balloon pre-dilation, 4.3% [30 of 692]). There was an increase of external elastic membrane area (18.9+/-3.9 to 24.5+/-5.1 mm2, P<0.001) that was greater than the increase in plaque area (9.6+/-3.0 to 11.4+/-2.9 mm2, P<0.001). Independent predictors of LSM were primary stenting in acute myocardial infarction (P=0.023, OR=2.55, 95% CI=1.14 to 5.69) and DCA before stenting (P=0.025, OR=3.02, 95% CI=1.15 to 7.96). There were no significant differences in major adverse cardiac events between LSM and non-LSM groups during mean 3-year follow-up (1.9% versus 1.8%, respectively, P=NS).

CONCLUSIONS

LSM occurs in approximately 5% after BMS implantation. The predictors of LSM are primary stenting in acute myocardial infarction and DCA before stenting. Compared with complete stent apposition at follow-up, LSM after BMS implantation is not associated with any major adverse cardiac events during a mean 3-year follow-up after detection of LSM.

Effect of preintervention remodeling type on subsequent coronary artery behavior after directional atherectomy

To evaluate the influence of preintervention remodeling on subsequent vessel behavior after directional coronary atherectomy (DCA) under intravascular ultrasound (IVUS) guidance, serial (before and after DCA and at 6-month follow-up) IVUS data were analyzed for 246 lesions that were classified into 2 categories: positive remodeling (PR) in 77 lesions versus intermediate or negative remodeling in 169 lesions. Although the 2 groups had similar baseline characteristics, IVUS data showed that the PR group had a greater acute lumen area (LA) gain without an increased late LA loss, resulting in a greater net (acute plus late) LA gain and follow-up LA. This suggests that IVUS-guided DCA may neutralize the negative impact of preintervention PR on late vessel patency.

Lesion regression after percutaneous coronary intervention for unprotected left main trunk disease

BACKGROUND

Although some studies have documented the six-month angiographic outcomes of percutaneous coronary intervention (PCI) with new devices for unprotected left main trunk disease (ULMTD), a long-term angiographic analysis is mandatory to evaluate the safety and effectiveness of this procedure. This study aims to assess a long-term (one year or more) angiographic analysis after PCI for this lesion.

METHODS

PCI was performed for 225 ULMTD with de novo or restenotic lesions. There were 19 deaths and 12 repeat PCIs during the hospital stay. The remaining 194 lesions were followed, and 126 lesions showed no angiographic restenosis or target lesion revascularization within six months. Finally, long-term quantitative angiographic follow-up was completed in 78 lesions (mean 2.4 years, maximum 7.5 years after PCI).

RESULTS

Minimal lumen diameter increased significantly from 2.46 +/- 0.59 mm to 2.72 +/- 0.65 mm (p < 0.0001) and percent diameter stenosis decreased significantly from 26 +/- 14% to 19 +/- 14% (p < 0.0001) between the six-month and the long-term follow-ups. No additional restenosis or new lesions were found at long-term follow-up, and significant lesion regression was ascertained in each procedure (directional coronary atherectomy, p < 0.005; ballooning, p < 0.005; stenting, p < 0.05).

CONCLUSIONS

These findings support the safety and effectiveness of PCI for ULMTD during the long-term period.

Effect of plaque debulking before stent implantation on in-stent neointimal proliferation: a serial 3-dimensional intravascular ultrasound study

BACKGROUND

Recent intravascular ultrasound (IVUS) studies have suggested that plaque burden has a role in promoting intimal hyperplasia after stenting. We report on volumetric assessments of in-stent neointimal formation with 3-dimensional IVUS analysis, comparing directional coronary atherectomy (DCA) plus stenting (DCA/stenting) to stenting without DCA.

METHODS

Twenty-four patients (24 lesions) treated with DCA before stenting were matched to 24 patients (24 lesions) receiving stenting without DCA. All stents were a single Multilink stent. In both groups, serial IVUS was performed before and after intervention and during the 6-month follow-up period. The arterial segments that were analyzed with a computer-based contour detection program were the same as the stented segments analyzed on serial studies. These measurements were obtained: (1) lumen volume (LV), (2) stent volume (SV), (3) vessel volume (VV), (4) in-stent neointimal volume (ISV) calculated as SV-LV, and (5) percent in-stent neointimal volume (%ISV) calculated as ([SV-LV]/SV) x 100.

RESULTS

Baseline characteristics of the 2 groups were similar. After intervention, both groups achieved similar LV (140.0 mm(3) DCA/stenting vs 135.2 mm(3) stenting alone). However, the follow-up ISV and %ISV were significantly smaller in the DCA/stenting group (19.6 +/- 12.2 mm(3) DCA/stenting vs 44.6 +/- 29.5 mm(3) stenting alone; P =.00040; 15.3% +/- 10.6% DCA/stenting vs 31.5% +/- 17.7% stenting alone; P =.00040). Consequently, the DCA/stenting group showed a significantly greater follow-up LV (121.0 +/- 51.5 mm(3) DCA/stenting vs 91.5 +/- 26.7 mm(3) stenting alone; P =.016).

CONCLUSIONS

Plaque removal with DCA before stenting inhibits in-stent neointimal hyperplasia.

Impact of deep vessel wall injury on acute response and remodeling of coronary artery segments after cutting balloon angioplasty

Deep vessel wall injury is believed to affect vessel dimension following coronary intervention. The cutting balloon is designed to treat coronary artery stenoses with dilatation and surgical incisions, thereby reducing excess vessel injury. This study examines the effect of deep vessel wall injury on acute and late coronary arterial response after cutting balloon angioplasty. Serial volumetric intravascular ultrasound (IVUS) analyses were performed in 63 lesions treated with cutting balloon angioplasty alone. Before intervention, the longitudinal range of the lesion segment that included the smallest lumen area (LA) was determined as LA <4 mm(2) and/or LA stenosis >60%. The exact corresponding site at postintervention and follow-up was aligned using peri- and intravascular landmarks. Average vessel area (VA), plaque area (PA), and LA were measured. Lesion segments were categorized as with or without deep vessel wall injury, which was defined as the presence of plaque/vessel wall fracture extending to the sonolucent (medial) layer. Before intervention, the lesion vessel size of deep injury group was smaller than that of the nondeep injury group (p <0.05 for average VA and PA), whereas average lesion LA, lesion length, and reference vessel size did not differ. Immediately after cutting balloon angioplasty, the deep injury group showed a significant increase in VA (p <0.0001) and a lesser decrease in PA (p <0.01) compared with the nondeep injury group. During follow-up, the increase of VA tended to be greater in the deep injury group than in the nondeep injury group (p = 0.06), whereas the change of PA did not differ. Consequently, LA decrease was less in the deep injury group than in the nondeep injury group (p <0.05). From these results, it is suggested that deep vessel wall injury tends to occur in lesions with relatively small size and such lesions show favorable vessel response after cutting balloon angioplasty.

Predictors of vessel remodeling following directional coronary atherectomy

The purpose of this study was to clarify predictors of vessel remodeling following directional coronary atherectomy (DCA). Negative remodeling after DCA leads to restenosis. However, little is known about the predictors of the vessel remodeling. Serial IVUS was performed in 43 lesions. The vessel remodeling was defined as adaptive if vessel area at follow-up minus postprocedure vessel area was > 0 mm2, or as constrictive if < 0 mm2. Adaptive remodeling occurred in 21 (49%) lesions. Postprocedure percent plaque area was smaller in the adaptive group (32.9% +/- 5.7% vs. 45.5% +/- 8.8%; P < 0.005). At follow-up, vessel area was larger in the adaptive group. However, plaque area was similar between the two groups. As a result, lumen area was larger in the adaptive group. Multivariate analyses showed that postprocedure percent plaque area < 40% was the only predictor of adaptive remodeling (odds ratio, 6.68; P < 0.05).

Angiographic analysis of the angioplasty versus rotational atherectomy for the treatment of diffuse in-stent restenosis trial (ARTIST)

Patients with diffuse in-stent restenoses (ISRs) are at high risk for recurrent restenosis after percutaneous transluminal balloon angioplasty (PTCA). Percutaneous transluminal rotational ablation (PTCR) has proved effective in removing neointimal burden in ISRs. This study compares the acute and long-term results of PTCA and PTCR for the treatment of diffuse ISR in a randomized, multicenter investigation. The primary end point was the comparison of the minimum luminal diameter (MLD) between both groups at 6-month follow-up. Patients with symptomatic, diffuse, or high-grade ISRs were included; 146 patients were randomized to PTCA and 152 patients to PTCR. Diameter stenosis was reduced from 80 +/- 12% to 29 +/- 10% and from 80 +/- 11% to 28 +/- 12%, respectively, and MLD increased from 0.55 +/- 0.3 to 1.9 +/- 0.3 mm in the PTCA group and from 0.54 +/- 0.3 mm to 1.9 +/- 0.4 mm in the PTCR group. Spasm in the treated vessel and an intermittent slow flow phenomenon occurred more often after rotational ablation (17.7% vs 8.6%, p = 0.001; 5.3% vs 0%, p = 0.007). Minimum stenosis diameter at 6-month follow-up was smaller in the PTCR group than in the PTCA group (1.0 +/- 0.6 vs 1.2 +/- 0.6 mm, p = 0.008) and the restenosis rate was higher (64.9% vs 51.2%, p = 0.027). Procedural factors did not influence long-term outcome. In the PTCR group, the restenosis rate increased with decreasing vessel size, whereas this was not seen in the PTCA group. The lesion length and the baseline diameter stenosis were found to be predictive of restenosis with both treatment strategies; however, a residual diameter stenosis of <30% predicted absence of a restenosis only in the PTCR group. Thus, PTCA and PTCR of diffuse ISRs yield comparable acute angiographic results. The recurrence of a restenosis is higher after PTCR than after PTCA.

Impact of deep vessel wall injury and vessel stretching on subsequent arterial remodeling after balloon angioplasty: a serial intravascular ultrasound study

BACKGROUND

Arterial remodeling has been shown to be responsible for lumen narrowing after nonstent interventions.

METHODS

To examine the impact of deep vessel wall injury (DI) after balloon angioplasty on the subsequent vessel remodeling process, we performed serial intravascular ultrasound (IVUS) analysis in 47 native coronary artery lesions that underwent balloon angioplasty. An IVUS study was performed before and after balloon angioplasty and repeated at follow-up. Vessel and lumen area were measured at the narrowest site before intervention. Plaque area was calculated as vessel area minus lumen area. DI was defined as the presence of plaque/vessel wall fracture deep in the medial layer (sonolucent zone by IVUS) after angioplasty.

RESULTS

After angioplasty, DI was present in 18 (38%, DI group) and absent in 29 (62%, non-DI group) of lesions. During follow-up, changes in vessel area in the DI group were significantly larger than in the non-DI group (P =.007). There were no significant differences in changes in plaque area. A trend toward greater late lumen loss was observed in the non-DI group (P =.05). In the DI group, changes in lumen area correlated better with changes in vessel area (r = 0.81, P <.0001) than with changes in plaque area (r = 0.32, P =.20). However, in the non-DI group, changes in lumen area correlated with changes in plaque area (r = -0.55, P =.002), but not with changes in vessel area (r = 0.30, P =.11).

CONCLUSIONS

Deep vessel wall injury after balloon angioplasty is associated with the magnitude of the subsequent vessel remodeling process. The differences in the remodeling process may have implications regarding adjunctive therapies to prevent restenosis after balloon angioplasty.

Peristent tissue proliferation of multilink stents is dependent on preprocedural plaque area: a serial intravascular ultrasound analysis

It is not known whether any factors are related to tissue proliferation within and surrounding stents in humans. The authors used serial intravascular ultrasound (IVUS) to evaluate the relationship between IVUS parameters and tissue proliferation within and surrounding Multilink stents. They were able to analyze preinterventional and postinterventional and follow-up IVUS studies in 33 native vessel lesions in 33 patients with stable angina pectoris. Quantitative coronary angiography and IVUS measurements were performed before and after intervention and at follow-up. IVUS imaging using an automatic transducer pullback device allowed follow-up analysis of the same lesion site. The vessel area at the lesion site increased from 17.1 +/- 4.5 mm2 after intervention to 18.5 +/- 5.9 mm2 at follow-up (p<0.01). The in-stent tissue growth (after intervention to follow-up) in-stent plaque area (PA) was 1.6 +/- 1.1 mm2, and the peristent tissue growth (after intervention to follow-up) peristent PA was 0.8 +/- 2.3 mm2. In multivariate analysis, the preprocedural PA at the lesion site was the best predictor of the peristent tissue growth, whereas no factors predicted the in-stent tissue growth. Risk factors, clinical characteristics, and quantitative coronary angiographic parameters showed no relation to the peristent tissue growth or the in-stent tissue growth. The peristent tissue growth was closely related to the preprocedural plaque size, while the factors that affect the in-stent tissue growth were not identified.

Role of plaque proliferation in late lumen loss after directional coronary atherectomy

Previous reports suggest that vessel remodeling is the most important factor in late lumen loss in non-stented lesions, but because results of directional coronary atherectomy (DCA) show that increased plaque area (PA) is also important, the aim of this study was to redefine the mechanism of late lumen loss after DCA. One hundred and twenty lesions that underwent DCA with intravascular ultrasound (IVUS) guidance and serial IVUS analysis were studied, and vessel area (VA), lumen area (LA), PA (VA-LA) and corrected values (each value divided by the value of VA pre procedure to correct the vessel size) were analyzed. During follow-up, corrected VA (cVA) decreased by 0.058 +/- 0.191, whereas corrected PA (cPA) increased by 0.087 +/- 0.159. Though the %PA (PA/VA) after the procedure showed significant negative correlation with the subsequent change in cPA, it did not correlate with the subsequent change in cVA. In conclusions, the mechanism of late lumen loss after DCA consists of both arterial remodeling and plaque proliferation, and the residual %PA after the procedure determines the subsequent lumen loss. With a lower %PA, a change in the PA contributes more to late lumen loss than do changes in VA. With a high %PA, a change in the VA contributes more to late lumen loss.

Dose–volume histograms based on serial intravascular ultrasound: a calculation model for radioactive stents

BACKGROUND AND PURPOSE

Radioactive stents are under investigation for reduction of coronary restenosis. However, the actual dose delivered to specific parts of the coronary artery wall based on the individual vessel anatomy has not been determined so far. Dose-volume histograms (DVHs) permit an estimation of the actual dose absorbed by the target volume. We present a method to calculate DVHs based on intravascular ultrasound (IVUS) measurements to determine the dose distribution within the vessel wall.

MATERIALS AND METHODS

Ten patients were studied by intravascular ultrasound after radioactive stenting (BX Stent, P-32, 15-mm length) to obtain tomographic cross-sections of the treated segments. We developed a computer algorithm using the actual dose distribution of the stent to calculate differential and cumulative DVHs. The minimal target dose, the mean target dose, the minimal doses delivered to 10 and 90% of the adventitia (DV10, DV90), and the percentage of volume receiving a reference dose at 0.5 mm from the stent surface cumulated over 28 days were derived from the DVH plots. Results were expressed as mean+/-SD.

RESULTS

The mean activity of the stents was 438+/-140 kBq at implantation. The mean reference dose was 111+/-35 Gy, whereas the calculated mean target dose within the adventitia along the stent was 68+/-20 Gy. On average, DV90 and DV10 were 33+/-9 Gy and 117+/-41 Gy, respectively. Expanding the target volume to include 2.5-mm-long segments at the proximal and distal ends of the stent, the calculated mean target dose decreased to 55+/-17 Gy, and DV 90 and DV 10 were 6.4+/-2.4 Gy and 107+/-36 Gy, respectively.

CONCLUSIONS

The assessment of DVHs seems in principle to be a valuable tool for both prospective and retrospective analysis of dose-distribution of radioactive stents. It may provide the basis to adapt treatment planning in coronary brachytherapy to the common standards of radiotherapy.

What has intravascular ultrasound taught us about plaque biology?

Intravascular ultrasound (IVUS) has a defined role in the cardiac catheterization laboratory to assess lesion severity and the procedural success of vascular interventions. However, IVUS has also contributed to our understanding of the biology of atherosclerosis and restenosis. In acute coronary syndromes, IVUS has revealed varying degrees of stenosis, thrombosis, and plaque derangement typical of the plaque disruption seen in many pathologic studies of patients who have died of this condition. IVUS has demonstrated that the culprit lesions of patients surviving acute coronary syndromes also tend to be softer, with less calcium, and tend to have more plaque with positive arterial remodeling (compensatory enlargement) than lesions causing stable coronary syndromes. Arterial remodeling is also an important component of restenosis after coronary interventions. IVUS has suggested that interventions that reduce restenosis tend to have a greater impact on preventing negative remodeling (constriction) rather than reducing neointimal proliferation. Oxidant stress may be an important contributor to negative remodeling, as IVUS has demonstrated this anatomy at sites of coronary artery spasm. Positive remodeling seen by IVUS is also associated with impaired endothelial vasomotor dysfunction, and IVUS studies have demonstrated the contribution of vasomotor tone to arterial elasticity. Future directions include integrating IVUS with other imaging modalities, such as angiography, to study the interaction of anatomic and physiologic factors in atherosclerosis progression, and using the raw ultrasound signal to distinguish plaque components and differences in wall strain that may identify vulnerable plaques.

Impact of peri-stent remodeling on restenosis: a volumetric intravascular ultrasound study

BACKGROUND

Vessel remodeling is an important mechanism of late lumen loss after nonstent coronary interventions. However, its impact on in-stent restenosis has not been systematically investigated.

METHODS AND RESULTS

Serial volumetric intravascular ultrasound analyses (poststent and follow-up) were performed in 55 lesions treated with a balloon-expandable stent (ACS MultiLink) using standard stent deployment techniques. The vessel volume (VV), lumen volume (LV), and volume bordered by the stent (SV) were measured using Simpson's method. The volume of plaque and neointima outside the stent (peri-stent volume, PSV) and volume of neointima within the stent (intrastent volume) were also measured. The change of each parameter during the follow-up period (follow-up minus poststent) was calculated and then divided by SV to normalize these values (designated as percent change [%]). As expected, %PSV directly correlated with %VV (P<0.0001, r=0.935), with no significant SV. A highly significant inverse correlation was seen between %PSV and the percent change of intrastent volume (P<0.0001, r=0.517). Consequently, %LV significantly correlated with peri-stent remodeling, as measured by %VV (P<0.0001, r=0.602).

CONCLUSION

Positive remodeling of the vessel exterior to a coronary stent occurs to a variable degree after stent implantation. There is a distinct trade-off between positive remodeling and in-stent hyperplasia: in segments in which the degree of peri-stent remodeling is less, intrastent neointimal proliferation is greater and accompanied by more significant late lumen loss.

Pre-existing arterial remodeling is associated with in-hospital and late adverse cardiac events after coronary interventions in patients with stable angina pectoris

OBJECTIVES

The goal of this study was to investigate the association between the atherosclerotic arterial remodeling and the incidence of cardiac events after coronary interventions in patients with stable angina.

BACKGROUND

The local mode of de novo atherosclerotic remodeling is associated with plaque vulnerability and clinical symptoms. It may, therefore, reflect plaque morphology influencing the long-term outcome after coronary interventions.

METHODS

Quantitative angiography and intravascular ultrasound were obtained in 244 patients with stable angina before and after single-vessel revascularization. On the basis of the lesion and the reference segment vessel size, patients were categorized into three groups (adaptive [AR], constrictive [CR] and intermediate [IR] remodeling). The lesion was analyzed for lumen, total vessel and plaque areas. Clinical follow-up was obtained at a mean period of 7.7+/-3.7 months.

RESULTS

Patients with CR had a higher rate of in-hospital complications (10.9% vs. 2.9% and 2.7% in group CR vs. AR and IR, p = 0.035). In contrast, patients with AR had the highest rate of major adverse cardiac events (MACE) (44.3% vs. 25.5% in IR and 28.1% in CR, p = 0.024) with a predominance of revascularization at follow-up. Both target lesion restenosis (p = 0.036) and nontarget lesion de novo stenosis (p = 0.007) occurred more frequently in this group. Adaptive remodeling was a significant predictor of MACE in multivariate analysis.

CONCLUSIONS

Adaptive remodeling is associated with a higher rate of MACE, target lesion restenosis and nontarget de novo stenosis. This finding may be due to differential responses of the adaptively remodeled vessel to revascularization and a generally accelerated course of systemic atherosclerosis.

Initial and 6-month results of biodegradable poly-l-lactic acid coronary stents in humans

BACKGROUND

Although metallic stents are effective in preventing acute occlusion and reducing late restenosis after coronary angioplasty, many concerns still remain. Compared with metallic stents, poly-l-lactic acid (PLLA) stents are biodegradable and can deliver drugs locally. The aim of this study was to evaluate the feasibility, safety, and efficacy of the PLLA stent.

METHODS AND RESULTS

Fifteen patients electively underwent PLLA Igaki-Tamai stent implantation for coronary artery stenoses. The Igaki-Tamai stent is made of a PLLA monopolymer, has a thickness of 0.17 mm, and has a zigzag helical coil pattern. A balloon-expandable covered sheath system was used, and the stent expanded by itself to its original size with an adequate temperature. A total of 25 stents were successfully implanted in 19 lesions in 15 patients, and angiographic success was achieved in all procedures. No stent thrombosis and no major cardiac event occurred within 30 days. Coronary angiography and intravascular ultrasound were serially performed 1 day, 3 months, and 6 months after the procedure. Angiographically, both the restenosis rate and target lesion revascularization rate per lesion were 10.5%; the rates per patient were 6.7% at 6 months. Intravascular ultrasound findings revealed no significant stent recoil at 1 day, and they revealed stent expansion at follow-up. No major cardiac event, except for repeat angioplasty, developed within 6 months.

CONCLUSIONS

Our preliminary experience suggests that coronary PLLA biodegradable stents are feasible, safe, and effective in humans. Long-term follow-up with more patients will be required to validate the long-term efficacy of PLLA stents.

Relation between stent expansion and arterial remodeling: a serial intravascular ultrasound study

Previous studies suggested that stent area (SA) did not change after the Palmaz-Schatz stent implantation. Whether these findings apply to other types of stent, however, is unknown. This study assessed vascular response to stent implantation using intravascular ultrasound (IVUS) studies. Serial (pre-intervention to follow-up) IVUS imagings were used to study 57 native coronary lesions after the GFX stent or the Multilink stent implantation. The vessel area (VA) at lesion site increased at follow-up (16.92 +/- 3.67 mm(2) after intervention to 18.17 +/- 4.66 mm(2) at follow-up, P < 0.01). The SA also increased from 8.39 +/- 1.90 mm(2) after intervention to 8.80 +/- 2.08 mm(2) at follow-up (P = 0.02). Thirty-two percent of lesions showed late stent expansion. The stent expansion [Delta (after intervention to follow-up) SA] correlated significantly with the VA growth [Delta (after intervention to follow-up) VA] (r = 0.59, P < 0.0001). In conclusion, some lesions reveal late stent expansion after both the GFX stent and the Multilink stent implantation. Adaptive vessel remodeling may be followed by stent expansion.

Safety of intracoronary gamma-radiation on uninjured reference segments during the first 6 months after treatment of in-stent restenosis: a serial intravascular ultrasound study

BACKGROUND

The effects of endovascular irradiation on uninjured reference segments during the treatment of in-stent restenosis are unknown.

METHODS AND RESULTS

In the Washington Radiation for In-Stent restenosis Trial (WRIST), patients with in-stent restenosis were first treated with conventional catheter-based techniques and then randomized (blinded) to receive either gamma-irradiation ((192)Ir) or a placebo (dummy seeds). We identified all patients in whom the active (n=19) or dummy seeds (n=19) extended >10 mm proximal and distal to the in-stent restenosis lesion. Serial (postirradiation and follow-up) external elastic membrane (EEM), lumen, and plaque and media (EEM-lumen) areas were measured (using intravascular ultrasound) every 1 mm over 5-mm-long reference segments that were 6 to 10 mm proximal and distal to the in-stent restenosis lesion. During follow-up, a similar small increase occurred in the plaque and media area in the proximal and distal reference segments in both (192)Ir and placebo patients. However, in the (192)Ir patients, an increase in both proximal and distal EEM area occurred; as a result, no change in lumen area occurred. Conversely, in the placebo patients, the proximal reference EEM area decreased, and no change occurred in the distal reference EEM area; this contributed to a decrease in lumen area.

CONCLUSIONS

There was no evidence of a deleterious effect of gamma-irradiation on angiographically normal uninjured reference segments in the first 6 months after the treatment of in-stent restenosis.

[The practical clinical guidelines of the Sociedad Española de Cardiología on interventional cardiology: coronary angioplasty and other technics]

Interventional cardiology has had an extraordinary expansion in last years. This clinical guideline is a review of the scientific evidence of the techniques in relation to clinical and anatomic findings. The review includes: 1. Coronary arteriography. 2. Coronary balloon angioplasty. 3. Coronary stents. 4. Other techniques: directional atherectomy, rotational atherectomy, transluminal extraction atherectomy, cutting balloon, laser angioplasty and transmyocardial laser and endovascular radiotherapy. 5. Platelet glycoprotein IIb/IIIa inhibitors. 6. New diagnostic techniques: intravascular ultrasound, coronary angioscopy, Doppler and pressure wire. For the recommendations we have used the classification system: class I, IIa, IIb, III like in the guidelines of the American College of Cardiology and the American Heart Association.

Final results of the STent versus directional coronary Atherectomy Randomized Trial (START)

OBJECTIVES

This study was designed to compare primary stenting with optimal directional coronary atherectomy (DCA).

BACKGROUND

No previous prospective randomized trial comparing stenting and DCA has been performed.

METHODS

One hundred and twenty-two lesions suitable for both Palmaz-Schatz stenting and DCA were randomly assigned to stent (62 lesions) or DCA (60 lesions) arm. Single or multiple stents were implanted with high-pressure dilation in the stent arm. Aggressive debulking using intravascular ultrasound (IVUS) was performed in the DCA arm. Serial quantitative angiography and IVUS were performed preprocedure, postprocedure and at six months. The primary end point was restenosis, defined as > or =50% diameter stenosis at six months. Clinical event rates at one year were also assessed.

RESULTS

Baseline characteristics were similar. Procedural success was achieved in all lesions. Although the postprocedural lumen diameter was similar (2.79 vs. 2.90 mm, stent vs. DCA), the follow-up lumen diameter was significantly smaller (1.89 vs. 2.18 mm; p = 0.023) in the stent arm. The IVUS revealed that intimal proliferation was significantly larger in the stent arm than in the DCA arm (3.1 vs. 1.1 mm ; p < 0.0001), which accounted for the significantly smaller follow-up lumen area of the stent arm (5.3 vs. 7.0 mm2; p = 0.030). Restenosis was significantly lower (32.8% vs. 15.8%; p = 0.032), and target vessel failure at one year tended to be lower in the DCA arm (33.9% vs. 18.3%; p = 0.056).

CONCLUSIONS

These results suggest that aggressive DCA may provide superior angiographic and clinical outcomes to primary stenting.

Review: Clinical aspects of vascular remodeling

Vascular remodeling represents a spectrum of structural changes whereby the vascular wall responds to changes in its hemodynamic environment. Such changes may be classified as vessel enlargement (outward remodeling), diminution (inward remodeling), alternatively as adaptive (compensatory, appropriate to the hemodynamic stimulus), or maladaptive (dysfunctional, inappropriate). The direction and scale of remodeling are coordinated by endothelial production of growth factors, proteases, and cellular adhesion molecules in response to sensed changes in blood flow. In early atherosclerosis, outward remodeling preserves lumen size. Although protective in the long-term, the matrix degradation involved in this process may predispose atherosclerotic plaques to rupture, hence increasing the risks of acute coronary syndromes. Inward remodeling also occurs in advanced atherosclerotic lesions, whereby the vessel shrinks rather than enlarging, exacerbating rather than ameliorating stenosis. In transplant coronary artery disease, early inward remodeling may be a more important component of vessel stenosis than intimal thickening, while inappropriate inward remodeling appears to be as least as important as excessive intimal growth in the development of restenosis after angioplasty. Increased awareness of vascular remodeling, and in particular its malaptive forms, may provide new therapeutic insights for the future.