Three-months optical coherence tomography analysis of a biodegradable polymer, sirolimus-eluting stent

OBJECTIVE

We aimed to assess early neointimal healing by optical coherence tomography (OCT) 3 months after implantation of the ultrathin Orsiro® sirolimus-eluting stent with biodegradable polymer.

BACKGROUND

New generations of drug-eluting stents with biodegradable polymer have been developed to avoid the continued vascular irritation of durable polymers.

METHODS

In this prospective, open-label study, 34 patients received an Orsiro® sirolimus-eluting stent with biodegradable polymer. In a subgroup of patients (n = 15), the intervention was performed under OCT guidance. All patients underwent OCT-examination at three months. The primary endpoint was 3-month neointimal healing (NIH) score, calculated by weighing the presence of filling defects, malapposed and uncovered struts. Secondary endpoint was maturity of tissue coverage at 3 months.

RESULTS

At 3 months, NIH score was 13.7 (5.4-22), covered struts per lesion were 90% (84-97%), malapposed struts were 2.7% (0.8-5.4%) and rate of mature tissue coverage was 47% (42-53%). No target lesion failure occurred up to 12 months. Patients with OCT-guided stent implantation demonstrated a trend toward earlier stent healing as demonstrated by superior NIH scores (angio guided: 17.6% [8.8-26.4]; OCT-guided: 9.8% [4.0-15.5]; mean difference -8, [95%CI: -18.7-2.9], P = 0.123). This group had significantly more covered struts per lesion (angio-guided: 86% [82-90]; 95% [92-99]; mean difference 9% [95%CI: 3-15], P = 0.001).

CONCLUSION

The Orsiro® sirolimus-eluting stent with biodegradable polymer shows early vascular healing with a high rate of strut coverage at 3-month follow-up. OCT guided stent implantation had a positive impact on early vascular healing.

Incidence of Atrial Fibrillation after Percutaneous Closure of Patent Foramen Ovale and Small Atrial Septal Defects in Patients Presenting with Cryptogenic Stroke

Objective

The occurrence of atrial fibrillation after percutaneous closure of a patent foramen ovale for cryptogenic stroke has been reported in a variable percentage of patients. However, its precise incidence and mechanism are presently unclear and remain to be elucidated.

Design

Prospective follow-up study.

Patients

Ninety-two patients undergoing a percutaneous patent foramen ovale closure procedure (closure group) for cryptogenic stroke were compared with a similar group of 51 patients, who were medically treated.

Methods

A systematic arrhythmia follow-up protocol to assess the incidence of AF was performed including a 7-day event-loop recording at day 1, after 6 and 12 months in patients of the closure group and compared with those of the medically treated group.

Results

The incidence of AF was similar in both study groups during a follow-up of 12 months, including 7·6% (95% CI: 3·1–15·0%) in the closure and 7·8% (95% CI: 2·18–18·9%) in the medically treated group ( P = 1·0). The presence of a large patent foramen ovale was the only significant risk factor for the occurrence of AF as demonstrated by a multivariate Cox regression analysis (95% CI, 1·275–20·018; P = 0·021).

Conclusions

Our findings indicate that patients with cryptogenic stroke and patent foramen ovale have a rather high incidence of AF during a follow-up of 12 months. Atrial fibrillation occurred with a similar frequency whether the patent foramen ovale/atrial septal defect was successfully percutaneously closed or was medically managed. The presence of a large patent foramen ovale was the only significant predictor of AF occurrence during follow-up.

The role of the sizing balloon in selection of the patent foramen ovale closure device size

OBJECTIVES

To find a correlation between the patent foramen ovale (PFO) size measured by the sizing balloon and the appropriate closure device size.

METHODS

The PFO of 57 patients was closed using a sizing balloon. A mathematical model was introduced to relate the PFO balloon waist diameter to the closure device size based on the PFO transformation from a slit-like to a circular form during balloon inflation. According to this model, PFOs smaller than 8 mm should be closed with a 25 mm device, PFOs 8 mm to 11 mm with a 35 mm device, and PFOs larger than 11 mm with an Amplatzer septal occluder. In the first group, 36 patients (63.2%) received an appropriately sized device and six patients (10.5%) received an oversized device. In the second group, 15 patients (26.3%) received an undersized device.

RESULTS

A comparison of the PFO dimensions in two views showed that the PFO slit was circular when the balloon was inflated. A six-month echocardiography follow-up was obtained in 46 patients (80.7%). Five patients (13.9%) in the group with an appropriately sized device had a discrete residual shunt during Valsalva. In the second group, five patients (33.3%) had a residual shunt (P = 0.06), of which one was considered large.

CONCLUSION

The sizing balloon is helpful in selecting the PFO closure device size. Consequently, the incidence of residual shunt and recurrent events may be reduced.

A morphological–mechanical explanation of edge restenosis in lesions treated with vascular brachytherapy

PURPOSE

Edge restenosis in stenotic lesions treated by implantation of a conventional stent followed (or preceded) by a catheter-based brachytherapy is often attributed to "geographic miss" (GM). We propose a complementary (or, possibly, alternative) explanation based on the concept that a clear postprocedural mismatch between the in-stent lumen and the normal (undilated) lumens of the proximal and/or distal vessel segments results in an excessive, damageable increase of axial wall stress in these segments.

METHODS

The possible poststenting situations at both margins of a stent are examined, and based on the presence or absence of an increase in axial wall stress, predictions are made about the lesion evolution. The concept is then also examined in the light of published observations.

RESULTS

None of the analyzed observations appeared to be incompatible with the proposed morphological-mechanical explanation.

CONCLUSION

From a mechanical point of view, optimal matching of the proximal and distal stent diameters to the corresponding normal diameters of the adjacent arterial segment is likely to reduce the rate of edge restenosis.

Gamma-Irradiation Markedly Inhibits the Hydrated Collagen Gel Contraction by Arterial Smooth Muscle Cells

BACKGROUND

Vessel wall responses to percutaneous transluminal coronary angioplasty include neointimal proliferation and arterial remodeling. The contraction of a collagen gel is a good in vitro model of wound repair and vascular remodeling. Because irradiation is an important new therapeutic modality capable of preventing restenosis, the purpose of this study was to evaluate the effect of irradiation on the contraction of a collagen gel by smooth muscle cells (SMCs), on SMCs viability, and on DNA synthesis.

METHODS

We studied the effect of different doses of gamma-irradiation (0 [control], 6, 12, and 18 Gy) on the contraction of a collagen gel seeded with SMCs (calf carotid arteries) during a period of 15 days.

RESULTS

Maximal gel diameter reduction (from 35 to 6.8 mm, +/-0.5 mm in control) was markedly inhibited in the 6-, 12-, and 18-Gy groups (35 to 13.7 mm, +/-0.8 mm; 35 to 15.5 mm, +/-0.9 mm; and 35 to 16.1 mm, +/-0.9 mm, respectively; P<0.0001). The irradiated gels showed a dose-dependent reduction in the SMC proliferation rate (P<0.0001) and an increase in the number of nonviable SMCs (P<0.002) 15 days after irradiation.

CONCLUSIONS

Gamma-irradiation produces a significant dose-dependent inhibition of the contraction of collagen gels seeded with arterial SMCs. This effect is related to a significant decrease in SMC viability and a decrease in SMC proliferation rate. These findings shed light on mechanisms whereby irradiation may positively affect arterial remodeling after percutaneous transluminal coronary angioplasties.

Mechanisms of neointima formation and remodeling in the porcine coronary artery

BACKGROUND

To characterize the cells responsible for neointima formation after porcine coronary artery wall injury, we studied the expression of smooth muscle cell (SMC) differentiation markers in 2 models: (1) self-expanding stent implantation resulting in no or little interruption of internal elastic lamina and (2) percutaneous transluminal coronary angioplasty (PTCA) resulting in complete medial rupture and exposure of adventitia to blood components.

METHODS AND RESULTS

The expression of alpha-smooth muscle (SM) actin, SM myosin heavy chain isoforms 1 and 2, desmin, and smoothelin was investigated by means of immunohistochemistry and Western blots in tissues of the arterial wall collected at different time points and in cell populations cultured from these tissues. The expression of smoothelin, a marker of late SMC differentiation, was used to discriminate between SMCs and myofibroblasts. Both stent- and PTCA-induced neointimal tissues and their cultured cell populations expressed all 4 markers. The adventitial tissue underlying PTCA-induced lesions temporarily expressed alpha-SM actin, desmin, and SM myosin heavy chain isoforms, but not smoothelin. When placed in culture, adventitial cells expressed only alpha-SM actin.

CONCLUSIONS

Our results suggest that SMCs are the main components of coronary artery neointima after both self-expanding stent implantation and PTCA. The adventitial reaction observed after PTCA evolves with a chronology independent of that of neointima formation and probably corresponds to a myofibroblastic reaction.

Endoluminal beta-radiation therapy for the prevention of coronary restenosis after balloon angioplasty. The Dose-Finding Study Group

BACKGROUND

Beta radiation is effective in reducing vascular neointimal proliferation in animals after injury caused by balloon angioplasty. However, the lowest dose that can prevent restenosis after coronary angioplasty has yet to be determined.

METHODS

After successful balloon angioplasty of a previously untreated coronary stenosis, 181 patients were randomly assigned to receive 9, 12, 15, or 18 Gy of radiation delivered by a centered yttrium-90 source. Adjunctive stenting was required in 28 percent of the patients. The primary end point was the minimal luminal diameter six months after treatment, as a function of the delivered dose of radiation.

RESULTS

At the time of follow-up coronary angiography, the mean minimal luminal diameter was 1.67 mm in the 9-Gy group, 1.76 mm in the 12-Gy group, 1.83 mm in the 15-Gy group, and 1.97 mm in the 18-Gy group (P=0.06 for the comparison of 9 Gy with 18 Gy), resulting in restenosis rates of 29 percent, 21 percent, 16 percent, and 15 percent, respectively (P=0.14 for the comparison of 9 Gy with 18 Gy). At that time, 86 percent of the patients had had no serious cardiac events. In 130 patients treated with balloon angioplasty alone, restenosis rates were 28 percent, 17 percent, 16 percent, and 4 percent, respectively (P=0.02 for the comparison of 9 Gy with 18 Gy). Among these patients, there was a dose-dependent enlargement of the lumen in 28 percent, 50 percent, 45 percent, and 74 percent of patients, respectively (P<0.001 for the comparison of 9 Gy with 18 Gy). The rate of repeated revascularization was 18 percent with 9 Gy and 6 percent with 18 Gy (P=0.26).

CONCLUSIONS

Intracoronary beta radiation therapy produces a significant dose-dependent decrease in the rate of restenosis after angioplasty. An 18-Gy dose not only prevents the renarrowing of the lumen typically observed after successful balloon angioplasty, but actually induces luminal enlargement.

Methodological and clinical implications of the relocation of the minimal luminal diameter after intracoronary radiation therapy. Dose Finding Study Group

OBJECTIVES

The aims of the study were to determine the incidence of relocation of the minimal luminal diameter (MLD) after beta-radiation therapy following balloon angioplasty (BA) and to describe a new methodological approach to define the effect of brachytherapy on treated coronary stenoses.

BACKGROUND

Luminal diameter of coronary lesions may increase over time following angioplasty and irradiation. As a result, the MLD at follow-up may be relocated from its location preintervention, which may induce misleading results when a restricted definition of the target segment by quantitative coronary angiography (QCA) is performed.

METHODS

Patients treated with BA followed by intracoronary brachytherapy according to the Dose-Finding Study constituted the study population. A historical cohort of patients treated with BA was used as control group. To be included in the analysis, an accurate angiographic documentation of all instrumentations during the procedure was mandatory. In the irradiated patients, four regions were defined by QCA: vessel segment (VS), target segment (TS), injured segment (INS), and irradiated segment (IRS).

RESULTS

Sixty-five patients from the Dose-Finding Study and 179 control patients were included. At follow-up, MLD was relocated more often in the radiation group (78.5% vs. 26.3%; p < 0.0001). The rate of >50% diameter stenosis differed among the four predefined regions: 3.1% in the TS; 7.7% in the INS; 9.2% in the IRS and 13.8% in the VS.

CONCLUSIONS

Relocation of the MLD is commonly demonstrated after BA and brachytherapy, and it should be taken into account during the analysis of the results of radiation clinical trials.

Intraarterial beta irradiation induces smooth muscle cell apoptosis and reduces medial cellularity in a hypercholesterolemic rabbit restenosis model

PURPOSE

Ionizing radiation has been shown to be a powerful inhibitor of neointimal hyperplasia following arterial injury in several animal models of post-percutaneous transluminal coronary angioplasty (post-PTCA) restenosis. This was previously shown to be associated with a reduction in smooth muscle cell (SMC) mitotic activity. This study evaluated the effect of intraarterial beta irradiation on the arterial wall SMC density and apoptosis.

METHODS AND MATERIALS

Twenty-five carotid and 7 iliac arteries of hypercholesterolemic New Zealand white rabbits were injured using the Baumgartner technique. The impact of an 18 Gy beta radiation dose administered after balloon injury was studied and compared to a nonirradiated injured control group. The medial SMC density as well as the percentage of apoptotic cells were determined at 8 days, 21 days, and 6 weeks after injury using an automated computer-based software. Apoptotic cells were identified using in situ end-labeling of fragmented DNA.

RESULTS

The values for medial apoptosis in control vs. irradiated arteries were: 0.014 +/- 0.023 vs. 0.23 +/- 0.28%, p = NS, at 8 days; 0.012 +/- 0.018 vs. 0.07 +/- 0.07%, p = 0.05, at 21 days; and 0 +/- 0 vs. 0.16 +/- 0.11%, p = 0.03, at 6 weeks. The overall incidence of medial apoptotic cells at all time points was 0.01 +/- 0.017 vs. 0.13 +/- 0.14% in controls and irradiated arteries respectively, p = 0.004. Medial SMC density was significantly decreased in irradiated arteries in comparison with controls (p < 0.01 at all time-points).

CONCLUSIONS

Intraarterial beta irradiation stimulates medial SMC apoptosis in balloon-injured arteries. This, together with a decrease in SMC mitotic activity, contributes to a decrease in the arterial wall cellularity.

Yttrium-90 delivered via a centering catheter and afterloader, given both before and after stent implantation, inhibits neointima formation in porcine coronary arteries

BACKGROUND

Intracoronary radiation (IR) studies have shown reduction of neointima formation (NF). Extrapolation of animal studies with beta-radiation to clinical trials have shown variable results, which may be related to dosimetry, centering issues, and/or shielding of beta-rays by the stent metal. We examined the effect of yttrium-90 (90Y), a pure beta-emitter delivered via an automatic afterloader to a centering catheter, on the inhibition of NF in balloon-injured (BI) porcine coronary arteries as well as in arteries receiving 90Y either prior to or following stent implantation (SI).

METHODS

Twenty-three swine (44 coronary arteries) were studied. In the first study, IR (18 Gy at 1.2 mm from the balloon surface) was administered in 17 arteries following BI, while eight control arteries were subjected to BI only. In the second study, 10 swine (19 coronary arteries) underwent SI. IR (18 Gy) was administered in six arteries before and in eight arteries after SI, while five control arteries received SI only. The animals were sacrificed 2 weeks after BI and 4 weeks after SI. Their coronaries were perfusion fixed and stained, and vessel parameters (intimal area [IA] and medial fracture length [FL]) were analyzed by computer-aided histomorphometry.

RESULTS

Arteries subjected to IR following BI had less NF compared to controls (IA/FL = 0.14 +/- 0.2 mm vs. 0.49 +/- 0.2 mm; P = 0.003). IA was reduced significantly in the arteries receiving radiation before and after SI compared to controls (0.92 +/- 0.98 and 0.00 +/- 0/00 vs. 2.72 +/- 1.2 mm2; P = 0.014), despite similar SI in all groups.

CONCLUSIONS

IR with 90Y delivered via a centering catheter is safe and effective with complete and homogenous inhibition of NF in the context of BI or SI in the porcine coronary model.

Intraarterial beta irradiation to reduce restenosis after PTCA. Experimental and clinical experience

The present data demonstrate clinical feasibility of intracoronary beta brachytherapy and fail to reveal any complications that could be attributed to it. Definitive conclusions regarding safety will have to await longer term evaluation. Proof of efficacy will require strict dose finding evaluation of higher doses than those used in the present pilot study followed by a controlled, randomized trial using both clinical and angiographic end-points.

[Early percutaneous coronary angioplasty in unstable angina]

The risks of complications of percutaneous transluminal coronary angioplasty (PTCA) are increased in unstable angina. Medical treatment for a few days before PTCA is widely adopted to reduce the risk of thrombosis or occlusive dissection during and after the procedure. Over the last few years, the authors have adopted a strategy of early coronary angiography completed by immediate angioplasty when possible, without waiting for the eventual benefit of aspirin or heparin therapy. Their experience from 1988 to 1995 of 853 patients treated by PTCA (151/853 or 17.7%, with implantation of a stent) for unstable angina, was reviewed. Group I comprised 402 patients treated on the day of or the day after admission. Group II comprised 451 patients treated 2 days or more after admission. Patients in Group I were younger (62 +/- 11 vs 64 +/- 12, p < 0.001), and had single vessel disease more often (61 vs 52%, p < 0.005). The success rate of PTCA was similar in the 2 groups (85.3 vs 88.2%, NS), as was the rate of complications (death, infarction or coronary bypass surgery, 9.9 vs 7.3%, NS). The length of hospital stay was significantly shorter in Group I (6.1 +/- 5.6 vs 8.7 +/- 6.9 days, p < 0.0001). With the limitations inherent to all retrospective studies, these data suggest that an early interventional approach in unstable angina has a similar success rate with no more complications than angioplasty. This approach is associated with a deferred significant decrease in the duration of hospital stay.

Feasibility and safety of beta irradiation in human coronary arteries

We have developed a technique of endoluminally centred endovascular beta irradiation aimed at preventing restenosis after PTCA. The source consists of a pure metallic 90-Yttrium coil that can be positioned within the lumen at the target site by the use of a centering device and an afterloading console. Experimental evaluation of this approach showed that a dose of 18 Gy delivered at the inner arterial surface was highly effective in preventing fibrointimal hyperplasia in rabbit carotid and iliac arteries. A pilot clinical evaluation in the coronary arteries of 15 patients using the same dose demonstrated excellent feasibility and no unexpected side-effects. A dose-finding evaluation in the clinical setting is now planned.

New device for compression of the radial artery after diagnostic and interventional cardiac procedures

Recently the transradial route has emerged as a valuable alternative to the femoral approach for coronary angiography and angioplasty. However, sheath and catheter size and their immediate removal after the procedure, combined with aggressive antiplatelet and anticoagulant therapies, have favored mechanical compression of the radial artery to achieve satisfactory hemostasis. We report on our initial clinical experience with a new device specially designed for prolonged controlled mechanical compression of the radial artery (the RadiStop radial compression system, RADI Medical Systems AB, Uppsala, Sweden). A total of 159 consecutive patients (mean age 60 +/- 11 yr, 130 males) who required either coronary angiography (group 1, 103 patients) or ad hoc or elective coronary angioplasty (group 2, 56 patients) via the right radial route had local hemostasis with the RadiStop system. In group 1, 4F and 5F sheaths and catheters were used, whereas in group 2, 6F systems were inserted in the radial artery. Hemostasis was achieved with the device in all patients but was considered difficult to obtain in 4 patients (2.5%). Twenty-eight patients (18%) considered the device uncomfortable or painful, but no release of pressure was necessary. The mean compression time was 151 +/- 82 min (114 +/- 64 min in group 1, and 223 +/- 64 min in group 2; P = 0.0001). There were 23 local complications (15%). In 7 patients (4.4%), the radial pulse was absent after compression and at discharge, without major clinical consequences. In one patient, recurrent bleeding occurred 2 hr after compression, requiring a new compression session. In 15 patients, a small local hematoma was observed. Neither heparin dosage nor the use of a 6F sheath affected the rate of radial artery patency in this survey. We conclude that the use of this device for mechanical compression of the radial artery after coronary angiography and angioplasty is efficient, and that its use is related to an acceptable rate of local complications.

Feasibility of intracoronary beta-irradiation to reduce restenosis after balloon angioplasty. A clinical pilot study

BACKGROUND

With the aim of decreasing the incidence of restenosis after coronary balloon angioplasty, we developed a technique of intracoronary beta-irradiation using an endoluminally centered pure metallic 90Y source. The purpose of the present study was to evaluate the clinical feasibility and safety profile of this approach with a dose of 18 Gy delivered to the inner arterial surface.

METHODS AND RESULTS

Between June 21 and November 15, 1995, fifteen patients (6 women and 9 men; mean age, 71 +/- 5 years) underwent intracoronary beta-irradiation immediately after a conventional percutaneous transluminal coronary angioplasty (PTCA) procedure. The PTCA/irradiation procedure was technically feasible in all attempted cases, and the delivery of the 18 Gy dose was accomplished without complications. In 4 patients, the intervention was completed through intra-arterial stent implantation because of dissection induced by the initial PTCA. During the follow-up period of 178 +/- 17 days (range, 150 to 225 days), no complication occurred that could be attributed to radiation therapy. No aneurysm or angiographically detectable thrombus was observed in any of the irradiated arterial segments. The clinical event rate (4 of 15 patients underwent further target lesion revascularization) and the angiographic follow-up (6 of 15 patients had a > 50%-diameter stenosis at the previously treated site) did not suggest a marked impact on the expected restenosis rate.

CONCLUSIONS

This early experience demonstrates that our approach is feasible, and no side effects attributable to radiation were noted during a 6-month period of follow-up. Whether higher doses of beta-irradiation will favorably affect post-PTCA restenosis in patients must await further evaluation.

New device for compression of the radial artery after diagnostic and interventional cardiac procedures

Recently the transradial route has emerged as a valuable alternative to the femoral approach for coronary angiography and angioplasty. However, sheath and catheter size and their immediate removal after the procedure, combined with aggressive antiplatelet and anticoagulant therapies, have favored mechanical compression of the radial artery to achieve satisfactory hemostasis. We report on our initial clinical experience with a new device specially designed for prolonged controlled mechanical compression of the radial artery (the RadiStop radial compression system, RADI Medical Systems AB, Uppsala, Sweden). A total of 159 consecutive patients (mean age 60 +/- 11 yr, 130 males) who required either coronary angiography (group 1, 103 patients) or ad hoc or elective coronary angioplasty (group 2, 56 patients) via the right radial route had local hemostasis with the RadiStop system. In group 1, 4F and 5F sheaths and catheters were used, whereas in group 2, 6F systems were inserted in the radial artery. Hemostasis was achieved with the device in all patients but was considered difficult to obtain in 4 patients (2.5%). Twenty-eight patients (18%) considered the device uncomfortable or painful, but no release of pressure was necessary. The mean compression time was 151 +/- 82 min (114 +/- 64 min in group 1, and 223 +/- 64 min in group 2; P = 0.0001). There were 23 local complications (15%). In 7 patients (4.4%), the radial pulse was absent after compression and at discharge, without major clinical consequences. In one patient, recurrent bleeding occurred 2 hr after compression, requiring a new compression session. In 15 patients, a small local hematoma was observed. Neither heparin dosage nor the use of a 6F sheath affected the rate of radial artery patency in this survey. We conclude that the use of this device for mechanical compression of the radial artery after coronary angiography and angioplasty is efficient, and that its use is related to an acceptable rate of local complications.

Effect of pre-treatment with transdermal glyceryl trinitrate on myocardial ischaemia during coronary angioplasty

OBJECTIVE

In the light of the reported inconsistent anti-ischaemic and antianginal effects of transdermal glyceryl trinitrate, its efficacy and influence on the effects of intracoronary glyceryl trinitrate were examined during coronary angioplasty, which provides a model of controlled, reversible ischaemia.

DESIGN

Double blind, randomised study of the effect of transdermal and intracoronary glyceryl trinitrate on ischaemia during coronary angioplasty.

PATIENTS

40 patients with isolated severe stenosis of the left anterior descending coronary artery.

INTERVENTIONS

Patients were randomised (double blind) to transdermal glyceryl trinitrate (10 mg per day) and placebo, starting four to six hours before angioplasty. After 4 one-minute balloon inflations intracoronary glyceryl trinitrate was injected (0.2 mg) and then 4 further one-minute inflations were performed.

MAIN OUTCOME MEASURES

The time to angina and the time to > 0.2 mV ST shift on surface electrocardiogram (ECG) or intracoronary ECG during the individual inflations.

RESULTS

These times did not significantly differ during initial inflations between transdermal glyceryl trinitrate (27 (11), 25 (9), and 19 (9) s, respectively) and placebo (34 (11), 30 (8), and 21 (7) s. After intracoronary glyceryl trinitrate, they were significantly prolonged compared with the initial values, without differences between patients with transdermal glyceryl trinitrate (37 (10), 30 (8), and 23 (8) s, respectively) or placebo (39 (15), 36 (11), and 28 (12) s). Ischaemic preconditioning was not seen.

CONCLUSIONS

Transdermal glyceryl trinitrate (10 mg per day), unlike intracoronary glyceryl trinitrate, did not alleviate the myocardial ischaemia produced by balloon inflation during coronary angioplasty.

A novel system for intracoronary beta-irradiation: description and dosimetric results

PURPOSE

A dosimetric evaluation of a new device dedicated to intravascular irradiation, associating a beta source and a centering device, was carried out before initiation of a clinical pilot study.

METHODS AND MATERIALS

A 29-mm-long 90Y coil, coated with titanium and fixed to the end of a thrust wire, was introduced into the inner lumen of purpose-built centering balloons of different diameters (2.5, 3, 3.5, and 4 mm). Dose homogeneity was evaluated by studying both axial and circumferential dose variations, based on readings from thermoluminescent dosimeters (TLDs) placed on the balloon surface. Axial homogeneity was determined by comparing the readout values of dosimeters located on peripheral balloon segments with those located on segments adjacent to the midpoint of the source. The centering ability of the device was studied by comparing measurements on opposing surfaces of the balloon. The dose attenuation by water and contrast medium was evaluated and compared with that in air. The balloon contamination was studied using a contamination counter. The total 90Y coil activity was measured by liquid scintillation to relate activity to surface dose.

RESULTS

Activity-surface dose correlation showed that for a linear coil activity of 1 mCi/mm, the mean dose rate at the surface of a 2.5-mm balloon filled with contrast medium was 8.29 Gy/min. The doses at the surface of larger balloons (3, 3.5, and 4 mm) filled with contrast were 78%, 59%, and 47%, respectively, of the dose measured at the surface of the 2.5-mm balloon. The coefficient of variation (CV) in surface dose for 2.5-, 3-, 3.5-, and 4-mm centering devices filled with contrast medium were 9%, 8%, 9%, and 12%, respectively. There was no statistically significant difference between readouts from central and peripheral balloon segments or among rows of dosimeters facing each other. For a 2.5-mm balloon, compared with air the dose attenuation by water and contrast medium was similar (0.70 and 0.69, respectively), but a significant difference was seen between the readouts of water- and contrast-filled balloons when the diameter was larger than 3 mm (p < 0.001). No contamination was found in the balloon shaft after source retrieval.

CONCLUSION

The dosimetric tests showed very good surface dose homogeneity, demonstrating satisfactory centering of the source within the centering balloons. The achievable dose rates will permit intravascular irradiation within a short time interval. The absence of residual balloon contamination after source retrieval meets the requirements for a sealed source used in a clinical setting.

Endovascular beta-irradiation after percutaneous transluminal coronary balloon angioplasty

PURPOSE

Intraluminal beta-irradiation has been shown to markedly decrease fibrointimal proliferation after arterial injury in experimental models. With the aim of reducing the incidence of restenosis after percutaneous transluminal coronary angioplasty (PTCA), we undertook a pilot clinical evaluation to assess both the technical feasibility and the clinical safety of this treatment after balloon coronary angioplasty.

METHODS AND MATERIALS

Between June 21 and November 15, 1995, 15 patients (6 women and 9 men, aged 72 +/- 5 years) underwent intracoronary beta-irradiation immediately after a conventional PTCA procedure. Both the PTCA and irradiation procedure were done in a conventional catheterization laboratory, using an endoluminally centered pure metallic 90Y source, a newly developed technique of intracoronary beta-irradiation. This was done after documenting the ability of the system to generate reproducible dose delivery to the arterial wall.

RESULTS

Both the PTCA and the irradiation procedure were technically feasible in all attempted cases, and a dose of 18 Gy was delivered with a local exposure time of 391 +/- 206 s (range 153-768). In four patients, the intervention was completed by intraarterial stent implantation because of dissection induced by the initial PTCA. No in-hospital complications occurred, and serial creatine kinase measurements remained within the normal range in all cases.

CONCLUSION

Our early experience thus suggests that reliable and reproducible dose delivery can be achieved, and that coronary endoluminally centered beta-brachytherapy is both feasible and safe on a short-term basis in the clinical setting. Whether this novel mode of therapy will favorably influence post-PTCA restenosis in patients, as it does in experimental models, must await long-term angiographic follow-up of the present series as well as further clinical study.

Intra-arterial beta irradiation prevents neointimal hyperplasia in a hypercholesterolemic rabbit restenosis model

BACKGROUND

Intra-arterial gamma irradiation has been shown to reduce restenosis after balloon angioplasty. The use of beta emitters should allow similar effects while inducing less undue tissue irradiation radioprotection problems.

METHODS AND RESULTS

Flexible 90-yttrium (90Y) coils inside a centering balloon were used to allow homogeneous intraarterial dose delivery. One carotid and one iliac artery of 21 hypercholesterolemic rabbits were deendothelialized and then irradiated. Four dose schedules were studied: (1) control (dilated, nonirradiated); (2) 6 Gy; (3) 12 Gy; and (4) 18 Gy. Arterial specimens were histologically evaluated at 8 days and at 6 weeks. For all radiation doses at 8 days compared with controls, there was a significant decrease in bromodeoxyuridine-labeled cells (245 +/- 93 cells/cm in control, 42 +/- 27 in 6 Gy, 72 +/- 107 in 12 Gy, and 2 +/- 2 in 18 Gy groups; P < .001) and in total neointimal cells (891 +/- 415 cells/cm in control, 79 +/- 43 in 6 Gy, 192 +/- 264 in 12 Gy and 22 +/- 13 in 18 Gy groups; P < .0002). At 6 weeks, computer-derived histological percent area stenosis was reduced from 26 +/- 10% in the control group to 1 +/- 1.3% in the 18 Gy group (P < .0001), but lower doses had no significant effect.

CONCLUSIONS

Administration of intra-arterial beta irradiation with a 90Y source is technically feasible and compatible with an ordinary catheterization laboratory environment. A dose of 18 Gy effectively induces long-term inhibition of neointimal hyperplasia.

Intra-arterial 90Y brachytherapy: preliminary dosimetric study using a specially modified angioplasty balloon

PURPOSE

Irradiation has been shown to be effective in preventing restenosis after dilatation in human peripheral arteries. We have developed a dedicated system for coronary intraarterial irradiation using a 90Y pure beta-emitting source inside a specially modified angioplasty balloon. This paper presents a preliminary dosimetric evaluation of this system.

METHODS AND MATERIALS

Specially fabricated titanium-covered and activated yttrium wires (outer diameter 0.32 mm) were used for these studies. Dosimetry was performed using small thermoluminescent dosimeters (TLDs) placed on the surface of the 2-cm long angioplasty balloons, inflated with contrast medium to a diameter of 2.5, 3, 3.5, and 4 mm. Radioactive 90Y wires were left in the inner balloon catheter and the surface dose rate was measured and extrapolated to 72 h after activation to allow a comparison between the values obtained. After observing the poor centering of the source within the standard angioplasty balloon, a new centering balloon was developed. A conventional balloon was subdivided into four evenly spaced interconnecting chambers, thus assuring adequate centering of the inner catheter. Thermoluminescent dosimetric measurements were performed with a 3.5 mm centering balloon to evaluate the homogeneity of the surface doses compared to those measured with the conventional balloon.

RESULTS

Thermoluminescent dosimetric measurements using the standard balloons filled with contrast medium were plotted semilogarithmically as a function of distance from the balloon surface. The logarithms of the measured doses fit a straight line as a function of depth. The doses at 1 mm and 3 mm are approximately 50 and 10% of the surface dose, respectively. Due to the poor centering of the source in the conventional balloons, the dispersion and standard deviations (SDs) of the measured surface doses increased proportionally to the balloon diameter (SDs are 1.89, 5.52, 5.79, and 6.46 Gy for 2.5, 3, 3.5, and 4 mm balloon diameters, respectively). For the 3.5 mm centering and conventional balloons the respective mean, minimum, and maximum surface doses were 8.41 Gy (min. 7.26; max. 9.46) and 7.89 Gy (min. 2.18; max. 16.06) and their standard deviations were 0.66 and 5.79 Gy, respectively.

CONCLUSIONS

Conventional angioplasty balloons cannot ensure a homogeneous dose delivery to an arterial wall with an intralumenal 90Y beta source. Preliminary dosimetric results using a modified centering balloon show that it permits improved surface dose distribution (axial and circumferential homogeneity), making it suitable for clinical applications.

High dose rate brachytherapy for prevention of restenosis after percutaneous transluminal coronary angioplasty: preliminary dosimetric tests of a new source presentation

PURPOSE

Balloon dilatation of coronary artery stenosis has become a standard treatment of atherosclerotic heart disease. Restenosis due to excessive intimal cell proliferation, which subsequently occurs in 20-50% of patients, represents one of the major clinical problems in contemporary cardiology, and no satisfactory method for its prevention has thus far been found. Because modest doses of radiation have proved effective in preventing certain types of abnormal cellular proliferation resulting from surgical trauma, and brachytherapy has already been used successfully after dilation of peripheral arteries, development of a radioactive source suitable for coronary artery applications would be of great interest.

METHODS AND MATERIALS

Nonradioactive flexible yttrium-89 wires (diameter of 0.15 and 0.26 mm) were activated within the thermal neutron flux of an experimental reactor. Standard angioplasty balloons (2 cm long, 2.5 mm in diameter when inflated) were inserted for dosimetry into a specially manufactured tissue equivalent phantom. Four wells, drilled perpendicular to the axis of the balloon, allowed for the insertion of thermal luminescent dosimeters (TLDs; 2 mm of diameter) and spacers. The angioplasty balloon was inflated with air or with contrast media. Radioactive yttrium-90 wires were left in the central lumen of the balloon for 2 min. Doses at the surface of the balloon, and at 1, 2, and 3 mm were determined from TLD readings.

RESULTS

Doses obtained at the surface of the balloon, for a 2-min exposure for the 0.26 mm wire (balloon inflated with air) and the 0.15 mm wire (air or contrast), were 56.5 Gy, 17.8 Gy, 5.4 Gy, respectively. As expected for a beta emitter, the fall-off in dose as a function of depth was rapid. External irradiation from the beta source was negligible.

CONCLUSIONS

Our experiments indicate that the dose rates attainable at the surface of the angioplasty balloon using this technique allow the doses necessary for the inhibition of intimal cell proliferation to be reached within a relatively short period of time. The thin yttrium-90 wires are very easy to handle, and their mechanical and radioactive properties are well suited to the requirements of the catheterization procedure.

Lack of predictors of left ventricular functional improvement following coronary angioplasty

Coronary angioplasty is frequently performed in a vessel with corresponding regional wall motion abnormalities. However, late improvement of left ventricular function remains questionable in many cases and is difficult to predict. A retrospective analysis of 115 patients with single vessel disease and corresponding abnormal regional left ventricular function at the time of coronary angioplasty was performed. All patients had control coronary angiography and a new contrast ventriculography 5.6 +/- 3.1 months later (range 0.8-11.8 months). Among those patients, 61 (53%) showed improvement of regional left ventricular function, which was not seen in the 54 (47%) others. Global ejection fraction increased significantly in the former group, whereas it remained unchanged in the later group. Before angioplasty, patients with and without improvement of systolic left ventricular function were indistinguishable in terms of history, medication, rest and stress electrocardiogram, and angiographic characteristics. During angioplasty, angina was more frequent (65% vs. 44%, p < 0.02) in patients with subsequent left ventricular functional improvement. At follow-up study, significant angiographic restenosis was more frequently encountered (68% vs. 43%, p < 0.05) in patients with no evidence of functional improvement. Thus, coronary angioplasty in a vessel responsible for left ventricular systolic dysfunction is followed in only half the cases by improvement of this parameter. No predictor of the functional outcome of the myocardium can be pointed out before the procedure is performed.

[Closure of patent ductus arteriosus using interventional catheterization]

Percutaneous closure of patent ductus arteriosus can be performed with the Rashkind technique. This procedure has been performed in 16 patients in Geneva since 1989. The age of the patients varied from 2 to 44 years (4 boys, 7 girls, and 5 women). Pulmonary hypertension was present in only 1 child. A 12 mm Rashkind umbrella was used in 11 patients with ductus of < or = 4 mm inner diameter, while a 17 mm umbrella was used in 5 cases for larger ducts. Ductus closure was carried out through a transvenous femoral approach in 15 cases, while in 1 patient a transarterial approach was employed because of impossibility of passing the ductus from the pulmonary artery. There was neither mortality nor morbidity in this series. The aortography performed just after device placement showed total ductus occlusion in 8 patients and partial closure in 8 others. The follow-up by color Doppler showed disappearance of the residual shunt in 4 of these 8 patients. Prophylaxis of bacterial endocarditis is therefore no longer necessary in 13 patients with complete ductus closure. Our experience with this technique confirms its efficacy and the possibility it offers of avoiding thoracotomy in the vast majority of patients with a patent ductus arteriosus. Further miniaturization of the device and delivery system should make it applicable in the neonatal period.

Early experience with coronary stenting

From April 1988 to December 1991, we implanted 75 coronary stents (29 self-expanding and 46 balloon expandable) in 62 patients. All had New York Heart Association class II to IV angina, and 11 (18%) had prior coronary artery bypass grafting (CABG). Thirty nine patients (63%) had 1 vessel disease, and 23 (37%) had multivessel disease. The mean left ventricular ejection fraction was 63 +/- 11%. The indications for coronary stenting were acute post percutaneous transluminal coronary angioplasty (PTCA) occlusion in 45 (73%) (bail out stenting) and restenosis in 17 (24%) (elective stenting). There were 52 single stent (84%), 7 double stent (11%), and 3 triple stent procedures (5%). The mean stent diameter was 3.8 +/- 0.5 mm, and the mean stent length 21 +/- 7 mm. The attempted vessels were the left main coronary artery in 2(3%), left anterior descending coronary artery in 27 (44%), left circumflex coronary artery in 8 (13%), right coronary artery in 17 (27%), and a saphenous vein graft in 8 (13%). Technical success was achieved in 74 stent implantations (98%). Technical failure occurred in 1 case with a self expanding stent because of inability to reach the lesion. In hospital complications (mean hospital stay 10 +/- 10, range 2-60 days) included temporary stent occlusion in 2 patients (3%) treated by balloon dilatation and thrombolysis with intravenous urokinase, permanent stent occlusion in 5 patients (8%), Q-wave infarction in 5 patients (8%), CABG in 4 patients (11%), and death in 3 patients (5%). At least 1 major complication (Q wave infarction, CABG, or death) occurred in 8 patients (13%).(ABSTRACT TRUNCATED AT 250 WORDS)