Percutaneous coronary laser balloon angioplasty: initial results of a multicenter experience

Angiographic observations 10 years following coronary laser balloon angioplasty

A patient underwent laser balloon angioplasty (LBA) combined with local intracoronary heparin therapy for treatment of a high grade stenosis of the mid-portion of the left anterior descending (LAD) coronary artery. Sustained patency of the LBA-treated lesion and no new coronary stenoses were found in a 10-year angiographic follow-up study.

Photochemotherapy of vascular cells with 8-methoxypsoralen and visible light: differential effects on endothelial and smooth muscle cells

BACKGROUND

The long-term efficacy of percutaneous transluminal coronary angioplasty is limited by the restenosis which occurs in approximately 40% of patients, usually within 6 months of the procedure.

PURPOSE

The present study was designed to evaluate the effects of 8-methoxypsoralen (8-MOP) activated with visible light on the properties of bovine aortic smooth muscle cells (SMC) and endothelial cells (EC) in vitro.

METHODS

Cells were seeded in polystyrene wells, allowed to attach over a 24-h period, incubated with 1, 20, or 50 microg/ml 8-MOP and then exposed to 12 J/cm2 visible light (447 nm). Cell counts were performed for up 14 days (n = 4-6 wells per time point), and each experiment was performed in triplicate. Cellular migration, morphology, and size were also analyzed.

RESULTS

The lowest 8-MOP dose (1 microg/ml) had no significant effect on SMC proliferation, while the highest dose (50 microg/ml) induced cytostasis. An intermediate dose of 8-MOP (20 microg/ml) produced a transient and reversible inhibition of proliferation. There was no significant effect on proliferation of EC at lowest dose of 8-MOP (1 microg/ml). However, in contrast to the SMC experiments, a transient and reversible inhibition of EC proliferation was seen at both 20 and 50 microg/ml 8-MOP.

CONCLUSIONS

These experiments demonstrate that while 8-MOP photoactivated with 447 nm visible light can reversibly inhibit the proliferation of both SMC and EC in a dose-dependent fashion, SMC are more sensitive to the treatment than EC.

Vascular procedures that thermo-coagulate collagen reduce local platelet deposition and thrombus formation: laser and laser-thermal versus balloon angioplasty

BACKGROUND AND OBJECTIVE

Exposure of the arterial wall matrix to blood leads to platelet deposition resulting in thrombosis. Because heat alters tissue matrix we proposed that heating reduces platelet deposition.

STUDY DESIGN/MATERIALS AND METHODS

Sixty arterial homografts (15 dogs) were mounted in an arterio-venous "shunt." Interventions included balloon angioplasty (BA), direct laser (LA), laser-thermal (LTA), and combined LTABA. 111Indium-labeled platelets were circulated, radio activity measured, and homografts processed for histology.

RESULTS

Radioactivity count (mean+/- SE) at BA sites (13,853+/-3,192 cpm/cm(2)) was greater than LA (7,038+/-981), LTA (5,294 +/-1,145), LTABA (6,176+/-1,571), and control (1,826+/-339), P<0.05. Electron microscopy showed fewer platelets at LA, LTA, and control than BA sites. BA spread the collagen on the arterial lumen while heat gelled collagen and confined it to the arterial media.

CONCLUSIONS

Heating the artery and gelling collagen during LA, LTA, or LTABA significantly reduced thrombogenicity.

Laser coronary angioplasty: history, present and future

The efficacy of percutaneous transluminal coronary angioplasty (PTCA) is limited by remaining plaque tissue and the development of restenosis. It has been demonstrated that the restenosis rate is low if a large lumen diameter is achieved after coronary intervention. Debulking of coronary stenoses is a concept to increase the luminal diameter after intervention. Laser angioplasty debulks coronary stenoses by ablation of atherosclerotic plaque. Since the first intravascular laser intervention, the technique has been significantly improved by the use of optimized wavelength, the development of flexible optimally spaced multifiber catheters and an additional saline flush technique. These technical advancements allowed a reduction in the incidence of adverse events, such as the number of dissections and perforations, associated with the use of the laser technique. Coronary laser angioplasty is commonly combined with adjunctive balloon angioplasty to optimize the outcome. Laser coronary angioplasty was not followed by a lower restenosis rate compared with plain balloon angioplasty in lesions without stents, however, a randomized comparison of the techniques including the use of the saline flush technique is not available yet. The value of excimer (acronym for excited dimer) laser coronary angioplasty for treatment of in-stent restenosis is still under investigation. So far, nonrandomized single center studies have not suggested a relevant benefit for this technique used for in-stent restenosis. In nonstented lesions there remain niche indications for laser angioplasty such as the treatment of ostial lesions, diffuse lesions or lesions traversable with a guidewire but not with an angioplasty balloon. Laser coronary angioplasty may also be useful after a failed balloon angioplasty and in patients with chronic total occlusions. The potential advantages of combining laser coronary angioplasty with vaporization of thrombus in patients with acute coronary syndromes are currently under evaluation.

In vivo intravascular laser photodynamic therapy in rabbit atherosclerotic lesions using a lateral direction fiber

BACKGROUND AND OBJECTIVE

This study was performed to evaluate the possibility of inducing regression of atherosclerotic foci by photodynamic therapy (PDT) using hematoporphyrin derivative (HpD).

STUDY DESIGN/MATERIALS AND METHODS

Atherosclerotic rabbits were divided into four groups: A (n = 6) and C (n = 6) were given 5 mg/kg of HpD intravenously; Groups B (n = 4) and D (n = 4) were not. Twenty-four hours after HpD administration, the aortae of groups A and B were exposed to 200 mw output argon dye laser beam at 630 nm for 10 minutes; groups C and D were exposed to 400 mw for 5 minutes. Three rabbits from groups A and C and two rabbits from groups B and D were sacrificed immediately after laser photoradiation, being named groups A 0, C 0 and groups B 0, D 0, respectively. Groups A 7, C 7, and Groups B 7, D 7 were sacrificed 7 days after the photoradiation.

RESULTS

In groups A 7 and C 7, most intimal cells and endothelial cells had become necrotic and disappeared, and a loss of intima was observed. No such changes were found in groups B 7, D 7.

CONCLUSION

The above data suggest that PDT caused effective regression of the atherosclerotic lesions.

Novel approach to rotational atherectomy results in low restenosis rates in long, calcified lesions: long-term results of the San Antonio Rotablator Study (SARS)

Ablation technique and adjunctive strategy may affect restenosis after rotational atherectomy. To minimize trauma to the vascular wall, we changed the technique of rotablation as follows: the RPM range was decreased to 140,000-160,000 RPM, the ablation was performed using a repetitive pecking motion, avoiding a decrease in the rotational speed of the burr greater than 3,000 RPM, long lesions were divided into segments and each segment was separately ablated, and the burr-to-artery ratio was intended to be approximately 0.75. To prevent coronary spasm, before and after each pass, 100-200 microg nitroglycerin and 100-200 microg verapamil i.c. boluses were administered. Adjunctive PTCA was performed using a closely sized 1.1:1 balloon-to-artery ratio with a noncompliant balloon at low pressures for 120 sec. The study incorporated 111 patients with a combined total of 146 calcified lesions. Results. A total of 31.5% of patients underwent a multivessel procedure. No deaths occurred. Q-wave MI and/or creatine kinase elevation greater than three times baseline levels occurred in 4.5% of patients. By quantitative coronary angiography (QCA), the reference vessel diameter was 3.13+/-0.59 mm, mean lesion length was 33.41+/-18.58 mm. Percent stenosis and mean luminal diameter were as follows: at baseline 75.7%+/-10.8%, or 0.76+/-0.41mm, Post-rotational atherectomy 41.5%+/-3.6%, or 1.83+/-0.43 mm, Post-PTCA 18.2%+/-11.9%, or 2.56+/-0.50 mm. Six-month angiographic follow-up was available in 64 (57.7%) pts. Net luminal gain was 1.15+/-0.76 mm, with a late luminal loss of 0.65+/-0.84 mm. The mean diameter stenosis at follow-up was 37.6%+/-28.5%, with MLD 1.91+/-1.21 mm. The binary restenosis rate was 28.1%. Therefore, modification of rotational atherectomy technique with adjunctive PTCA resulted in a favorable restenosis rate in long, calcified lesions. Cathet. Cardiovasc. Intervent. 48:48-53, 1999.

Effect of low grade radiofrequency heating on arterial vasospasm in the porcine model

Nineteen pigs were studied in order to assess the effect of low grade, radiofrequency-powered, thermal balloon angioplasty on the vasoconstrictor response of peripheral arteries. A mechanical stimulus was used to induce vasospasm. Thermal angioplasty reduced the extent of inducible vasospasm from 79% to 6% compared to nonthermal control inflations, which reduced the vasoconstrictor response from 75% to 60% (P < 0.001). Histologic studies demonstrated that the extent of myocyte necrosis was significantly greater in the thermally treated arteries than in the control vessels (P < 0.01). Thermal balloon angioplasty at 60 degrees C significantly attenuates peripheral arterial vasospasm induced by mechanical trauma in the porcine model. This paralytic effect may be related to the loss of myocytes secondary to thermal necrosis.

Abrupt vessel closure: changing importance, management, and consequences

Percutaneous coronary interventions have been performed for 20 years. Despite the success and progress of these interventions, abrupt vessel closure has been a dramatic adverse event of coronary interventions. Closure has frequently led to the major complications of death, myocardial infarction, and emergency coronary artery bypass. Because of the fear of this adverse event and its subsequent complications, the applicability of coronary interventions is sometimes limited. The pathologic characteristics of abrupt vessel closure have been recognized as predominantly caused by dissection, with vessel recoil and thrombus formation playing important secondary roles. The recognition of the lesions at risk for abrupt vessel closure has led to a strategy of lesion-specific device therapy to reduce complications. Similarly the role of antiplatelet and antithrombotic therapies have reduced complications. The earliest methods of dealing with abrupt closure was emergency coronary artery bypass surgery with significant rates of morbidity and mortality. With the advent of second-generation devices and techniques, particularly stents, the management of abrupt vessel closure has been simplified and alternatives to emergency coronary bypass are more available. This article will review the history and current status of the prevention and management of abrupt vessel closure and demonstrate that anticipation and management of this complication have been facilitated with reduction of subsequent complications and increased applicability of coronary interventions.

Arterial remodeling after experimental percutaneous injury is highly dependent on adventitial injury and histopathology

BACKGROUND

The extent and nature of unfavorable geometric remodeling, especially related to the adventitia, has not been studied previously. The purpose of this study was to examine two methods of experimental arterial injury, characterize the extent of remodeling, and determine if remodeling is injury-specific.

METHODS

Two methods for producing coronary stenoses in pigs were used: heat injury using thermal balloon angioplasty (resulting in adventitial fibrosis), and copper stent implantation (resulting in intense inflammation). Histomorphometric parameters included changes in neointimal thickness (delta neointima) from uninjured to injured sections, and differences in area circumscribed by the internal and external elastic laminas (delta internal elastic lamina area and delta external elastic lamina area, respectively). Remodeling was calculated for each lesion as the enlargement of the external elastic lamina area or internal elastic lamina area for incremental neointimal thickening, expressed as the slopes delta external elastic area/delta neointima and delta internal elastic lamina area/delta neointima.

RESULTS

Remodeling indices for the heat lesions for the heat lesions were negative (delta internal elastic lamina area/delta neointima = 0.15, delta external elastic lamina area/delta neointima = 0.64) and indicated little remodeling in contrast to copper stent injury (delta internal elastic lamina area/delta neointima = 0.95, delta external elastic lamina area/delta neointima = 1.20).

CONCLUSIONS

Remodeling in fibrotic compared to inflammatory lesions differs markedly, and may explain increased restenosis rates observed in thermal balloon angioplasty in patients. This formulation may be useful to study remodeling and restenosis following interventional technologies.

A new adjustable temporary stent catheter for management of acute dissection during balloon angioplasty

Acute coronary dissection remains a limitation of percutaneous transluminal coronary angioplasty. For the management of acute coronary dissection, a new adjustable temporary stent catheter that can be positioned to the lesion, deployed, and retrieved at a later stage was developed. This catheter has at its distal end a spiral stent that can be reduced and expanded in a controlled fashion by external manipulations. The adjustable temporary stent catheter was applied in three clinical cases with acute coronary dissection during balloon angioplasty. In all cases, the adjustable temporary stent catheter restored blood flow when it was expanded to the lesion for 60 min and this restoration was maintained after device removal. It is envisioned that this temporary stent device may prove a useful means for the treatment of acute coronary dissection during percutaneous transluminal coronary angioplasty.

The history of interventional cardiology: cardiac catheterization, angioplasty, and related interventions

The histories of cardiac catheterization, angioplasty, and other catheter interventions are spectacular journeys marked by undeterred genius, serendipity, and the vindication of the scientific method. Cardiac catheterization began with Hales's 1711 equine biventricular catheterization, other early experimental catheterizations in the nineteenth century, and Forssmann's dramatic 1929 right-heart self-catheterization. Cournand, Richards, and others finished unlocking the right heart in the 1940s; Zimmerman, Cope, Ross, and others unlocked the left heart in the 1950s; and the coronary arteries were inadvertently unlocked by Sones in 1958, leading to the advent of percutaneous femoral coronary angiography by Judkins and by Amplatz in 1967. Dotter's accidental catheter recanalization of a peripheral artery in 1963 ushered in the era of intervention, crowned by Gruentzig's balloon angioplasty in the mid-1970s and leading to today's panoply of devices used percutaneously to revascularize the coronary arteries in a variety of clinical settings.

Initial clinical experiences with rescue unipolar radiofrequency thermal balloon angioplasty after abrupt or threatened vessel closure complicating elective conventional balloon coronary angioplasty

OBJECTIVES

The purpose of this study was to evaluate the effectiveness of radiofrequency thermal balloon angioplasty and rescue procedure after abrupt or threatened vessel closure complicating elective percutaneous transluminal coronary angioplasty.

BACKGROUND

Coronary angioplasty is an established therapy for ischemic heart disease. However, abrupt closure after successful angioplasty remains a serious problem.

METHOD

We utilized a unipolar radiofrequency balloon in which a radiofrequency potential of 13.56 MHz was transmitted between the coil within the balloon and a plate electrode attached to the patient's body. The temperature within the balloon could be monitored through a thermistor within the balloon. From October 1991 through December 1993, 31 patients who had abrupt or threatened vessel closure during 1,005 consecutive elective coronary angioplasty procedures were randomly assigned to radiofrequency balloon angioplasty or to other procedures as rescue

RESULTS

Fifteen patients were assigned to radiofrequency balloon angioplasty (5 with abrupt vessel closure and 10 with threatened closure). The average balloon temperature and inflation time were 62 +/- 9 degrees C and 129 +/- 62 s, respectively. Percent diameter stenosis decreased from 87 +/- 14% to 36 +/- 25% (p < 0.01). The procedure was successful in 14 patients. The rate of restenosis was 67%, but the success rate of repeat conventional coronary angioplasty for restenosed lesions was 86%.

CONCLUSIONS

Radiofrequency balloon angioplasty is effective in the treatment of abrupt or threatened vessel closure complicating elective coronary angioplasty even though the procedure is associated with a relatively high rate of restenosis.

New methods of making blocked coronary arteries patent again

The use of percutaneous transluminal coronary angioplasty is limited by procedural complications and the serious drawback of restenosis, but some new techniques have been developed in an attempt to lower the complication rate for difficult lesions and reduce the rate of restenosis. These include devices to physically remove atheromatous plaque, such as the Simpson Coronary AtheroCath and the transluminal extraction catheter, as well as devices to ablate the plaque in situ, including the Rotablator and the excimer laser catheter. Although each device may have advantages in certain types of lesion, few data on their use have been reported in properly controlled randomised trials. The data available so far do not suggest that these devices will be safer than balloon angioplasty or that they will reduce restenosis. However, using metallic stents to support coronary arteries after balloon angioplasty seems to reduce acute complications and to lower the rate of restenosis, and the use of stents is likely to increase.

Inhibition of smooth muscle cell proliferation by visible light-activated psoralen

The present study was designed to evaluate the effect of 8-methoxypsoralen (8-MOP) activated with visible light (419 nm) on the suppression of smooth muscle cell (SMC) proliferation in vitro. We hypothesize that if visible light (VL) instead of UVA is used to photoactivate 8-MOP, cytotoxic 8-MOP-DNA cross-link formation can be minimized. Bovine aorta SMCs (2 x 10(4)/cm2) were incubated with 8-MOP (1 micrograms/mL) for 30 minutes (in the dark) and exposed to a range of VL (2 to 69 J/cm2) to determine the dose of VL that inhibits SMC proliferation with minimal toxicity. The results show that 8-MOP in combination with 2 to 12 J/cm2 VL reversibly inhibited SMC proliferation for up to 5 days after treatment. SMC viability was confirmed by trypan blue exclusion. 8-MOP in combination with 23- or 69-J/cm2 VL irreversibly inhibited SMC proliferation. In cell cycle studies, 12-J/cm2 VL was used to activate 8-MOP. A phase-specific G2 blockade that correlated temporally with recovery of SMC replication was observed. Photoadduct repair studies showed that cell proliferation rates recovered when 60% of the adducts had been removed. These results demonstrate for the first time the possibility of using VL to activate 8-MOP to inhibit cell proliferation and suggest that 8-MOP/VL photochemotherapy can be used to control SMC growth.

Temporary stents: the ACS RX flow support catheter

Although permanent stents have been successfully used as bail-out devices in the treatment of abrupt occlusion, the risk of stent thrombosis and of bleeding complications, as well as the cost of a prolonged hospitalization, have been deterrents to their universal acceptance. Temporary stents were conceived to provide internal scaffolding of the coronary arteries, which could stabilize occlusive dissections, yet still allow the stent to be removed before the time of peak incidence of subacute thrombosis. The ACS RX flow support catheter is a prototype temporary stent which has been recently evaluated in phase I and II clinical trials. The device is effective in improving angina score, coronary flow, and decreasing residual stenosis when used in cases of suboptimal percutaneous interventional results. However, the incidence of major complications and the need for adjunctive percutaneous interventions remain significant. Further studies are needed to define the optimal time of cage expansion as well as the clinical, anatomical, and procedural factors that predict efficacy and safety of this new device.

Microwave balloon angioplasty effectively seals arterial dissections in an atherosclerotic rabbit model

OBJECTIVES

The purpose of this study was to determine the effectiveness of microwave balloon angioplasty in sealing arterial dissections and to characterize the histologic features associated with this intervention.

BACKGROUND

Coronary dissection accompanying balloon dilation is frequently associated with abrupt closure and acute ischemic complications. Effective management of this complication remains an active area of investigation. Because thermal energy is effective in welding separated atherosclerotic plaques, a microwave-based catheter system that provides controlled local heating was utilized in vessels with angioplasty-induced dissections.

METHODS

Iliac artery dissections were induced in ahypercholesterolemic rabbit model. Vessels were randomly assigned to treatment with standard balloon angioplasty (control vessels) or microwave balloon angioplasty using an average temperature of 80 degrees C. The response of the artery was assessed angiographically and histologically.

RESULTS

Angiographic success, defined as a reduction of dissection length by > 50% or the resolution of lumen haziness, was achieved in 63% of microwave-treated vessels and in 16% of control vessels (p < 0.005). Dissection length (mean +/- SD) was reduced 8.0 +/- 4.8 mm in microwave-treated vessels compared with 0.1 +/- 7.9 mm in vessels receiving standard balloon inflations (p < 0.005). Cellular necrosis was more commonly observed in microwave-treated vessels than in control vessels (73% vs. 17%, p < 0.05), but less intraluminal thrombus was seen in vessels exposed to microwave energy (p < 0.05).

CONCLUSIONS

Microwave balloon angioplasty is more effective than routine balloon inflations in sealing arterial dissections in this model and appears to be less thrombogenic in these markedly disrupted vessels.

Radiofrequency thermal balloon coronary angioplasty: a new device for successful percutaneous transluminal coronary angioplasty

OBJECTIVES

The purpose of this study was to evaluate the effects of thermal balloon percutaneous transluminal coronary angioplasty using radiofrequency energy in the treatment of patients with failed coronary angioplasty and complex lesions. In addition, we evaluated restenosis after radiofrequency thermal balloon applications.

BACKGROUND

The efficacy of coronary angioplasty is limited by the relatively low success rate in complex lesions and the high frequency of restenosis. Few reports have studied the combined effects of pressure and laser thermal energy. This study describes a new device for coronary angioplasty using radiofrequency thermal energy.

METHODS

Thirty-two patients with failed conventional coronary angioplasty or complex lesions were treated with radiofrequency thermal balloon coronary angioplasty. Radiofrequency energy was delivered up to 11 times in exposures ranging from 30 to 60 s in duration. This combined effect allowed the vascular wall to be heated to temperatures ranging from 60 to 70 degrees C. Follow-up coronary angiography was performed, on average, 6 months after the procedure.

RESULTS

Successful radiofrequency coronary angioplasty was achieved in 28 (82%) of 34 lesions. There was one abrupt coronary artery occlusion (3%) and no death, perforation or dissection. Angiographic restenosis occurred in 14 (56%) of 25 lesions.

CONCLUSIONS

In patients with failed coronary angioplasty and difficult complex lesions, radiofrequency coronary angioplasty could potentially improve angioplasty success rates and may have important implications for bailout cases with abrupt occlusion. However, restenosis remains a significant problem.

Cardiovascular applications of laser technology

Laser technology has been evaluated for the treatment of coronary artery disease, ventricular and supraventricular arrythmias, hypertrophic cardiomyopathy, and congenital heart disease. Developments in laser angioplasty, laser thrombolysis, transmyocardial laser revascularization, photochemotherapy, laser treatment of arrhythmias and/or laser diagnostics are directed at improving upon conventional non-laser approaches, and providing new therapeutic and diagnostic options. This review will summarize the current status of the multiple applications of laser technology for cardiovascular diagnosis and therapy.

Acute biological response to laser balloon angioplasty in the atherosclerotic rabbit

Laser balloon angioplasty with Nd:YAG energy has been proposed as a method to seal intimal dissection and prevent elastic recoil after balloon angioplasty. To better define the vessel response to laser balloon angioplasty, its effects on luminal diameter, Indium-111 labelled platelet deposition, and histology were studied in 10 atherosclerotic rabbits. Balloon angioplasty was performed in both iliac arteries and was followed by laser balloon angioplasty in only one iliac artery. The nonlased artery served as a control. Single (15-35 W for 20 sec) or repetitive laser pulses (12-25 W for 20 sec x 3) were used. Platelet deposition was quantified 2 hr after the intervention. Lumen diameter (mm) increased following balloon angioplasty from 0.99 +/- 0.47 (mean +/- SD) to 1.92 +/- 0.43 and 0.89 +/- 0.46 to 1.99 +/- 0.57 in the balloon and laser-treated arteries, respectively (P < 0.001 for both groups for comparisons to baseline, P = NS for between groups comparison). Laser balloon angioplasty resulted in a further increase in luminal diameter to 2.42 +/- 0.53 (P < 0.02) when compared to the post balloon angioplasty diameter. Platelet deposition (10(6)/cm vessel) was higher following laser balloon angioplasty (26.9, 10.2-189; median range) than after balloon angioplasty (10.6, 3.4-30), P < 0.001. Histologic evidence of laser "sealing" was present in only one artery. Thus although laser balloon angioplasty results in an improved lumen diameter, it is accompanied by increased platelet deposition. In the atherosclerotic rabbit model, abolition of vascular recoil rather than "sealing" seems to be the most important advantage of laser balloon angioplasty over conventional balloon angioplasty.

Effects of thermal exposure on binding of heparin in vitro to the arterial wall and to clot and on the chronic angiographic luminal response to local application of a heparin film during angioplasty in an in vivo rabbit model

Experimentally, heparin inhibits mechanisms that promote fibrosis, neointimal cellular proliferation, and thrombin bound to fibrin at the surface of intraluminal thrombus, but only in relatively high concentrations. A preliminary hypothesis was tested and confirmed in vitro that initial binding of 3H-heparin to mechanically injured porcine aorta is concentration-dependent over a 1,000-50,000 units/ml range (r = 0.9). The hypothesis was then tested in vitro that thermal exposure during contact of heparin to arterial tissue and to clot would enhance binding of the drug. 3H-heparin binding to clot, whole blood particulates, and washed erythrocytes was markedly enhanced by exposure to temperatures > 70 degrees C. Thermal exposure (80 degrees C x 40 s) also enhanced tissue persistence of the drug within porcine aorta subjected to a shear rate of 1,100(-1) in an annular Baumgartner chamber perfused with normal saline at 37 degrees C for 48 h. Heparin in vitro anticoagulant activity persisted after thermal exposure and binding to tissues. A new method was developed for local application of a heparin film that provides a maximum concentration with a tolerable systemic dose during an angioplasty procedure. In an in vivo rabbit model of mural fibrosis after iliac artery angioplasty, the 1-month mean angiographic luminal diameter loss (23% compared to the acute postangioplasty result by computer image analysis) in response to conventional balloon angioplasty (BA) and laser balloon angioplasty (LBA) was the same (P > 0.05). Local application of a heparin film (3,000 units at a concentration > 100,000 units/g), however, reduced the mean % loss in diameter 1 month after LBA (12%), but not after BA (29%), compared to arteries subjected to angioplasty without local heparin (P < .05). The results are consistent with the hypothesis that thermal energy enhances heparin binding to tissues and that local application of a heparin film favorably modulates arterial luminal responses to LBA, but not to BA, in this animal model.

Evaluating new devices. Acute (in-hospital) results from the New Approaches to Coronary Intervention Registry

BACKGROUND

To be used optimally, new interventional devices (stent, lasers, atherectomy catheters) must be carefully evaluated in terms of optimal patient and lesion selection, technique of use, expected acute success and complications, and long-term results. Sources for that information include single-center and multicenter (single-device) reports, although randomized trials may then be performed to provide a more definitive picture of any clinical benefits. One interim option, however, consists of carefully collected registry data. The purpose of this article is to review data collected in the National Heart, Lung, and Blood Institute-funded New Approaches to Coronary Intervention (NACI) Registry and to compare them with existing reports.

METHODS AND RESULTS

NACI is an independent, investigator-driven effort that seeks to collect uniform data on patients undergoing treatment with one of several investigational devices and thereby provide an unbiased report of procedure outcome. Between November 1990 and November 1992, 36 participating centers treated a total of 3201 lesions in 2835 patients, using one of seven study devices: directional atherectomy (1084 lesions), transluminal extraction atherectomy (240 lesions), rotational atherectomy (349 lesions), Palmaz-Schatz stent (674 lesions), Gianturco-Roubin stent (213 lesions), and the Advanced Interventional Systems (474 lesions) or Spectranetics (167 lesions) excimer lasers. Data on each procedure were recorded on a unique modular database that captured the reason for (and interim result after) each device use. Device success (defined here as stenosis improvement by > or = 20% and a residual stenosis < 50% after new device use) was 66.5% overall. Adjunctive angioplasty was used in 75.5% of lesions, either before (25.9%) or after (43.5%) new device use, yielding an overall lesion success (> or = 20% stenosis improvement with a final residual stenosis < 50% after all devices) of 92.2%. Adjunctive angioplasty after new device use produced further enlargement in minimal lumen diameter (from 2.2 to 2.7 mm) and further reduction in residual stenosis (26.4% to 16.1%) compared with the results present after use of the new devices themselves. Major complications consisting of death (1.6%), Q-wave myocardial infarction (1.3%), or emergency bypass surgery (1.7%) occurred in 4.0% of patients (range, 2.6% to 8.7% across devices). Procedural success, defined as lesion success in all new device-treated lesions without a major complication, was achieved in 90.8% of patients, with a median length of hospital stay of 4 days.

CONCLUSIONS

NACI illustrates the type of information that can be obtained in a registry format that examines the acute angiographic and clinical results of new devices according to uniform definitions. Although no registry can substitute for formal interdevice trials, registries such as this can supplement earlier single-center and multicenter reports. In doing so, they can help focus subsequent randomized interdevice comparisons on lesion types for which two or more devices have promising acute results. Given the substantial interdevice differences in baseline patient and lesion characteristics found in NACI, simple "head-to-head" comparison of the results of different devices might give misleading impressions and should be avoided unless such comparisons are restricted to carefully matched patient and lesion subgroups.

Mechanisms of cardiac pain during coronary angioplasty

OBJECTIVES

This study was conducted to establish whether the cardiac pain patients experience during coronary angioplasty is modulated by 1) the stretching of the coronary artery wall, and 2) the mechanisms responsible for the ischemic preconditioning.

BACKGROUND

Anecdotal experimental observations indicate that stretching of the coronary artery wall is a stimulus adequate to cause cardiac pain. Furthermore, recent experimental studies indicate that adenosine, a mediator of the anginal pain, appears to play an important role in the genesis of ischemic preconditioning.

METHODS

We randomly allocated 48 consecutive patients undergoing coronary angioplasty into two groups. In Group A the second balloon inflation was performed at a higher level than the first; in Group B the first two inflations were performed at the same level of balloon pressure. The mean values (+/- 1 SD) of ST segment shift on the surface 12-lead electrocardiogram (ECG) and the intracoronary ECG were measured at the end of each inflation period. Severity of cardiac pain was also obtained at the same time by using a visual analog scale.

RESULTS

The mean ST segment shift during the second balloon inflation was significantly less than that during the first inflation in both groups of patients (12.8 +/- 9.3 vs. 18.5 +/- 11.9 mm, p < 0.001 and 13.7 +/- 10.1 vs. 21.3 +/- 13.9 mm, p < 0.001, respectively, in Groups A and B). Yet, the severity of cardiac pain during the second inflation was greater than that during the first inflation in Group A (40.8 +/- 32.7 vs. 26.9 +/- 27.2 mm, p < 0.01), whereas it was lesser in Group B (23.1 +/- 20.7 vs. 32.9 +/- 29.6 mm, p < 0.05). However, in the latter group, pain severity after normalization for the mean ST segment shift was similar during the first and second inflations (2.1 +/- 2.4 vs. 2.7 +/- 3.6, p = NS).

CONCLUSIONS

During coronary angioplasty, the cardiac pain experienced by patients is caused in part by stretching of the coronary artery wall. If the stretching is maintained at a constant level during repeated coronary occlusions, the cardiac pain is entirely predicted by the severity of myocardial ischemia and therefore does not appear to be directly modulated by the mechanisms responsible for the ischemic preconditioning.

Multicenter clinical experience with rescue atherectomy for failed angioplasty

Directional coronary atherectomy (DCA) has been proposed as a "rescue" technique for failed or suboptimal percutaneous transluminal coronary angioplasty (PTCA) in an attempt to avoid myocardial infarction or emergency coronary artery bypass grafting. In this report we review the utilization and outcome of rescue atherectomy from the clinical experience of The Cleveland Clinic Foundation and Medical College of Virginia from November 1988 through January 1993, and from the Coronary Angioplasty Versus Excisional Atherectomy Trial (CAVEAT) database. This analysis includes 100 patients with 103 treated lesions from 44 patients at the Cleveland Clinic, 36 patients from the Medical College of Virginia, and 20 patients from the CAVEAT database. The etiology of failed PTCA was primarily from dissection in 52 lesions (50.5%), "recoil" in 43 lesions (41.8%), and recurrent thrombosis in 8 lesions (7.8%). Complete vessel closure was present in 23 lesions (22.3%). The vessels treated included 51.5% left anterior descending, 24.3% right coronary, and 16.5% circumflex coronary arteries. The average reference vessel diameter in the group was 3.10 +/- 0.06 mm (SEM), with an average stenosis of 78.9 +/- 1.2% before PTCA, 55.8 +/- 2.4% after PTCA, and 24.1 +/- 2.2% after rescue DCA. DCA was successful (Thrombosis in Myocardial Infarction [TIMI] grade 3 flow with > 20% stenosis reduction without death, Q-wave myocardial infarction, or coronary artery bypass grafting) in 94 of 103 lesions (91.3%). Complications included 1 patient with perforation (1%), 2 deaths within 24 hours (2.0%), and 6 patients requiring coronary artery bypass grafting (6%).(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo radiofrequency thermal balloon angioplasty of porcine coronary arteries: histologic effects and safety

The purpose of this study was to assess the safety and histologic effects of radiofrequency thermal balloon angioplasty in the coronary vasculature of normal pigs. Radiofrequency thermal balloon angioplasty was performed in 30 coronary arteries of 16 nonatherosclerotic pigs. Heated inflations were performed at either 50 degrees, 60 degrees, or 70 degrees C for 30 or 60 seconds, and were compared with five nonheated inflations in five additional arteries. All balloon inflations were performed at 2 atm pressure with a balloon/vessel diameter ratio of 1.2 to 1. Heart rate, arterial pressure, and left ventricular pressure were monitored continuously for each animal. A 12-lead ECG, coronary angiography, and two-dimensional transthoracic echocardiography were performed before and 1 hour after each balloon inflation. Each animal was subsequently put to death for postmortem cardiac examination. Heated inflations were well tolerated in 28 of the 30 arteries without significant adverse effects. During one inflation, ventricular fibrillation occurred because of prolonged ischemia from an occlusive guiding catheter. In another artery, a heated inflation resulted in a dissection with a transient decrease in distal coronary flow. Histologic examination revealed a significant increase in wall thinning and elastic fiber straightening with heating at 70 degrees C for both 30 and 60 seconds, and a significant increase in intracoronary thrombus with heating at 70 degrees C for 60 seconds. Depth of periarterial myocardial heat necrosis paralleled the increase in temperature, with an average depth of 166 microns at 50 degrees C, 312 microns at 60 degrees C, and 1031 microns at 70 degrees C. In vivo, radiofrequency coronary angioplasty can be performed relatively safely without significant electrical, hemodynamic, or ischemic changes beyond those seen with conventional nonthermal angioplasty. The extent of heat-induced vessel wall thinning, elastic tissue straightening, intracoronary thrombus formation, and periarterial myocardial necrosis are all related to balloon temperature or duration of heating.

Both increased and decreased platelet adhesion to thermally injured subendothelium is caused by denaturation of von Willebrand factor

BACKGROUND

Thermal angioplasty methods heat the arterial wall. We related platelet adhesion to the temperature to which subendothelium and purified adhesive proteins had been exposed.

METHODS AND RESULTS

Cultured subendothelium, purified von Willebrand factor, collagen types I and III, or fibronectin was applied to glass coverslips. Coverslips were mounted on a heating device that applied a temperature gradient from 30 to 100 degrees C. De-endothelialized umbilical arteries were heated by immersion in phosphate-buffered saline. After cooling to room temperature, the surfaces were perfused with blood at 37 degrees C (shear rate, 1600 sec-1). Compared with 37 degrees C, platelet adhesion to endothelial cell matrix was significantly reduced by 25%, 50% or 75% after heating to 69 +/- 1 degree C (mean +/- SEM, P < .05), 72 +/- 1 degree C, or 75 +/- 1 degree C, respectively. Platelet coverage to umbilical artery subendothelium was in the same way significantly reduced after heating to 71 +/- 1 degree C, or 77 +/- 1 degree C, respectively. In contrast to endothelial cell matrix, however, heating to about 55 degrees C increased platelet coverage from 30 +/- 5% to 54 +/- 6% (P < .05). Both platelet adhesion to von Willebrand factor and monoclonal antibody binding against the GpIb binding site of von Willebrand factor showed a comparable temperature dependence as platelet adhesion to subendothelium, provided the proper von Willebrand factor concentration was used. Platelet adhesion to heated collagen types I and III was increased and maximal at 57 +/- 2 degrees C and 62 +/- 2 degrees C, respectively. Preincubation of collagen III with proteins resulted in decreased platelet adhesion with increasing temperatures. Heating did not affect the reactivity of fibronectin.

CONCLUSIONS

In vitro platelet adhesion to human subendothelium is reduced by more than 50% after heating it briefly to more than 74 degrees C. Temperatures in excess of 80 degrees C reduce platelet adhesion by at least 85%. Thermal denaturation of von Willebrand factor is responsible not only for the decreased thrombogenicity above 71 degrees C but also for the increased thrombogenicity near 55 degrees C, provided that the von Willebrand factor concentration is low.

Coronary and circulatory support strategies for percutaneous transluminal coronary angioplasty in high-risk patients

PTCA is now applied to patients with unstable acute ischemic syndromes, severe multivessel coronary artery disease, and impaired left ventricular function. To minimize the risk during angioplasty, several coronary and systemic circulation support approaches have been developed as adjuncts to high-risk angioplasty. Local coronary support techniques include the perfusion balloon catheter, the coronary stent, directional coronary atherectomy, laser balloon angioplasty, perfluorocarbon coronary perfusion, coronary sinus retroperfusion, and distal coronary hemoperfusion. Systemic circulatory support includes intraaortic balloon counterpulsation, cardiopulmonary support, the hemopump, and left heart partial bypass. These support devices, while associated with significant complications, may ultimately improve the safety of coronary angioplasty and allow its application to those who would otherwise not be candidates for revascularization.

Endoluminal sealing of vascular wall disruptions with radiofrequency-heated balloon angioplasty

Suboptimal luminal widening or acute closure secondary to arterial dissection remain significant risks of percutaneous transluminal balloon angioplasty. Non surgical techniques are often employed in an attempt to repair dissections either as temporary or definitive treatment. The aim of this study was to test the hypothesis that radiofrequency thermal balloon angioplasty at an operating temperature of 70 degrees C and low inflation pressure could seal dissections and perforations in a model of severe arterial wall damage. Dissections and perforations were created in renal (n = 4) and carotid (n = 4) arteries in four mongrel dogs. Endoluminal sealing was then attempted with conventional balloon angioplasty or radiofrequency thermal balloon angioplasty (2 atm at 70 degrees C). Contrast dye extravasation persisted in all cases following conventional balloon angioplasty but completely resolved with radiofrequency balloon angioplasty in all but one artery. Histologic examination of the arteries treated with radiofrequency balloon angioplasty showed extensive thermal injury, including transmural coagulation necrosis, flattening of the internal elastic lamina, and medial thinning. On the basis of these results, the utility of thermal balloon angioplasty for endoluminal sealing of dissections and perforations complicating angioplasty deserves further evaluation.

Low pressure radiofrequency balloon angioplasty: evaluation in porcine peripheral arteries

OBJECTIVES

The purpose of this study was to evaluate the efficacy of radiofrequency-powered thermal balloon angioplasty in an in vivo porcine model.

BACKGROUND

Various modes of thermal energy used adjunctively during balloon angioplasty have demonstrated the potential to enhance the results of acute lumen dilation.

METHODS

In normal pigs, 75 peripheral arteries were dilated with a newly designed, radiofrequency-powered, thermal angioplasty balloon. All inflations were performed at 2-atm pressure for 85 s. Dilations were performed either with (hot) or without (cold) the application of heat. Lumen dimensions and vessel morphology were assessed with intravascular ultrasonography. At the end of each study, dilated arterial segments were harvested for histologic examination.

RESULTS

Single cold balloon inflations resulted in a 12.7% increase in arterial cross-sectional area whereas single hot inflations resulted in a 22.9% increase (p < 0.03). Similarly, when multiple cold inflations were compared with multiple hot inflations, two, three and four sequential hot inflations resulted in a significantly greater increase in cross-sectional area than an equivalent number of cold inflations (p < 0.03). Histologic examination demonstrated a temperature-dependent effect on the depth of medial necrosis and extent of arterial wall thinning (p < 0.001) as well as evidence for uniform alteration of elastic tissue fibers at temperatures of > or = 60 degrees C (p < 0.03).

CONCLUSIONS

Low pressure radiofrequency thermal balloon angioplasty results in a greater increase in cross-sectional area in porcine peripheral arteries than does nonheated conventional balloon angioplasty. The pathologic basis for this enhanced dilation may be a temperature-dependent effect on medial necrosis, thinning of the arterial wall or alteration of vascular elastic fibers, alone or in combination.

Reduction of vasoreactivity and thrombogenicity with laser-thermal angioplasty: comparison with balloon angioplasty

The vasoreactivity and thrombogenicity of laser-thermal angioplasty were examined and compared with those of balloon angioplasty in an atherosclerotic rabbit iliac artery. Eight rabbits underwent laser-thermal angioplasty with a 1.7-mm hot-tip probe activated at 7 W with a probe temperature of 126 +/- 19 degrees C in one iliac artery. The other iliac artery was treated with balloon angioplasty using a 2.0-mm balloon. Angiographic luminal diameter increased from 0.19 +/- 0.15 to 1.54 +/- 0.35 mm by laser and from 0.29 +/- 0.22 to 1.84 +/- 0.20 mm by balloon (P less than 0.0001, respectively). However, it decreased to 1.34 +/- 0.42 for laser and 0.45 +/- 0.39 for balloon 60 minutes later (P less than 0.0001 vs immediately post). Both iliac arteries were visualized using angioscopy, which revealed thrombotic obstruction of 91% stenosis in the ballooned artery and 8% stenosis in the lased artery. Vasoreactivity of treated vessels was also investigated. Segments 3-mm long were obtained from either treated artery or control artery and examined for noradrenaline (10 -7 M) contraction. The segments were then mounted isometrically with 1 g tension in Krebs-bicarbonate buffer. Developed tension was 0.13 +/- 0.21 g for laser thermal and 2.33 +/- 0.4 g for its control (P less than 0.0001), and 0.15 +/- 0.16 g for balloon dilatation and 2.12 +/- 0.43 g for its control (P less than 0.0001). Neither acetylcholine at 10 -6 M or papaverine at 10 -4 M induced relaxation of treated segments. Histology showed slight thermal injury at thermally-treated sites without thrombus, and intimal and medial dissection with thrombus formation at balloon dilated site.

IN CONCLUSION

(1) neither a laser-thermal recanalized or a balloon dilated obstructed artery is vasoreactive to constrictive or relaxant agents; and (2) laser-thermal angioplasty results in less thrombogenicity than balloon angioplasty under moderate probe temperature.

The restenosis paradigm revisited: an alternative proposal for cellular mechanisms

Coronary restenosis is a reparative response to arterial injury during angioplasty, and remains a major clinical problem. The reasons for treatment failures likely stem from our incomplete understanding of the cellular mechanisms in restenotic neointimal formation. Restenosis is thought to result from migration and replication of medial smooth muscle cells to form an obstructive neointima, a concept neither observed nor demonstrated in humans. An alternative hypothesis for restenosis is based on observations in the porcine coronary injury model. In this model, there are three cellular stages in neointimal formation: thrombotic (stage I), cellular recruitment (stage II) and proliferative (stage III). The thrombotic stage occurs early and consists of platelets, fibrin and red blood cells accumulating at the vessel injury site. In the recruitment stage, the mural thrombus itself develops an endothelium, followed by a mononuclear leukocytic infiltrate beginning on the lumen side of the vessel. In the proliferative stage, a "cap" of actin-positive cells forms on the lumen surface and progressively thickens. These cells do not arise from media at the injury site. Extracellular matrix secretion and additional recruitment likely add to neointimal volume during this phase. Thrombus assumes a major role in restonosis by providing an absorbable matrix into which smooth muscle cells proliferate. Further studies are needed to validate or modify this hypothesis.

Dose-dependent smooth muscle cell proliferation induced by thermal injury with pulsed infrared lasers

BACKGROUND

Recently, laser-heated and radio frequency-heated balloon angioplasty techniques have been proposed as a means to treat or minimize dissection and elastic recoil but have been associated with a high rate of clinical restenosis. Similarly, pulsed laser angioplasty techniques proposed to minimize thermal injury while ablating obstructing atheroma have failed to reduce clinical restenosis. Because "hot balloon" and pulsed laser angioplasty create both mechanical and thermal injury, it has been difficult to discern the cause of the smooth muscle cell (SMC) proliferation resulting in restenosis and whether such magnitude of proliferation is predictable and dose related. This study was undertaken to explore these issues.

METHODS AND RESULTS

Localized thermal lesions accompanying efficient ablation were created with a pulsed Tm:YAG laser in nine rabbit aortas, which consistently led to a focal proliferation of SMC that filled the ablated region by 4 weeks. Transcutaneous Ho:YAG pulsed laser irradiation at multiple independent sites of 24 central rabbit ear arteries without ablation led to brief approximately 30 degrees C thermal transients and thermal damage to the artery wall resulting in significant neointimal proliferation by 3 weeks and a mean cross-sectional narrowing of 59 +/- 17% at a dose of 390 mJ/mm2. Acute and chronic responses to varying total energy deposition were studied by histology after the rabbits were killed at 2 hours to 4 weeks. Arterial segments midway between laser injuries were unaffected and served as internal controls. Neointimal proliferation at 3 weeks after laser injury exhibited a clear dose dependence. Mean cross-sectional narrowing increased from 34 +/- 10% to 85 +/- 15% as laser fluence increased from 240 mJ/cm2 to 640 mJ/cm2 (r = 0.84). Similarly, cross-sectional narrowing caused by SMC neointimal proliferation increased from 20 +/- 10% to 77 +/- 17% for a fixed surface irradiation as the depth of the most superficial arterial media decreased from 600 microns to 330 microns (r = 0.94).

CONCLUSIONS

Thermal injury to the arterial wall is a potent stimulus for SMC proliferation and may necessitate reduction in laser or thermal energy used for angioplasty. Moreover, a dose-response relation exists between the degree of thermal injury and SMC proliferative response. Hence, this technique could be used as a practical model of restenosis suitable for screening therapies for inhibition of SMC proliferation.

Microwave thermal balloon angioplasty in the normal rabbit

The feasibility of utilizing microwave energy for thermal angioplasty was evaluated in 28 normal New Zealand white rabbits. Angioplasty catheters were inserted via bilateral femoral arteriotomy and balloon angioplasty was performed on the external iliac arteries. There were three variables in the microwave angioplasty procedure: peak temperature, energy duration, and peak balloon pressure. At 1 week after the angioplasty, animals were put to death and the iliac arteries were removed after perfusion fixation. Histologic analysis was performed. Injuries to the medial and intimal proliferation were evaluated using an index based on the circumferential extent and depth of abnormality. There was no relationship noted between intimal proliferation or medial injury and energy duration of peak balloon pressure. There was a direct relationship between peak temperature and medial injury. Furthermore, there was an inverse relationship between medial injury and intimal proliferation. The axial extent of change induced by microwave energy was 1.6 cm. Microwave thermal energy delivery through a balloon angioplasty catheter is feasible and can be performed conveniently.

Mechanical right coronary artery shortening and vessel wall invagination: a fourth cause of iatrogenic coronary obstruction during coronary angioplasty. A case report and review of the literature

Coronary spasm, dissection, and localized thrombosis are recognized sources of iatrogenic obstruction during coronary angioplasty. A fourth important cause is reported, namely, guidewire-induced mechanical straightening and shortening of tortuous right coronary artery resulting in the invagination of redundant vascular tissue. Reversal is achieved with guidewire retraction. Recognition of this entity is crucial to avoid unnecessary and potentially harmful intervention.

Pulsed laser and thermal ablation of atherosclerotic plaque: morphometrically defined surface thrombogenicity in studies using an annular perfusion chamber

Although clinical trials using laser and thermal angioplasty devices have been underway, the effects of pulsed laser and thermal ablation of atherosclerotic plaque on surface thrombogenicity are poorly understood. This study examined the changes in platelet adherence and thrombus formation on freshly harvested atherosclerotic aorta segments from Watanabe-heritable hyperlipidemic rabbits after ablation by two pulsed laser sources (308-nm xenon chloride excimer and 2,940-nm erbium:yttrium-aluminum-garnet [YAG] lasers) and a prototype catalytic hot-tip catheter. Specimens were placed in a modified Baumgartner annular chamber and perfused with citrated whole human blood, followed by quantitative morphometric analysis to determine the percent surface coverage by adherent platelets and thrombi in the treated and contiguous control areas. Pulsed excimer laser ablation of plaque did not change platelet adherence or thrombus formation in the treated versus control zones. However, photothermal plaque ablation with a pulsed erbium:YAG laser resulted in a 67% reduction in platelet adherence, compared with levels in control areas (from 16.7 +/- 2.2% to 5.5 +/- 1.8%; p less than 0.005). Similarly, after plaque ablation using a catalytic thermal angioplasty device, there was a 74% reduction in platelet adherence (from 29.2 +/- 5.1% to 7.7 +/- 1.6%; p less than 0.005) and a virtual absence of platelet thrombi (from 8.6 +/- 2.3% to 0.03 +/- 0.03%; p less than 0.005). This reduced surface thrombogenicity after plaque ablation with either an erbium:YAG laser or a catalytic hot-tip catheter suggests that thermal modifications in the arterial surface ultrastructure or thermal denaturation of surface proteins, or both, may be responsible for reduced platelet adherence. These in vitro findings indicate that controlled thermal plaque ablation by catheter-based techniques may elicit endovascular responses that can reduce early thrombus formation during angioplasty procedures.

Novel coronary interventional devices: an update

Interventional cardiologists today are overwhelmed by a hugh array of new high technology investigatory devices at their disposal for the treatment of coronary arterial obstructive disease. These include the various atherectomy and laser devices, developed and introduced into clinical practice with the promise and intent of solving the limitations of conventional balloon angioplasty, namely those of acute closure and restenosis. But as more experience and data are obtained from the application of these devices, it is becoming clear that the latter have generally not been able to accomplish what they were intended to do. Although the immediate success rates have been uniformly high, acute closure has persisted and restenosis remains unabated. Nevertheless, some of these new devices have shown some fairly encouraging results in specific clinical circumstances. The targeted use of these instruments may prove to be a step in the right direction. This article reviews the current state of the art and the potential utility of certain of these devices.

Effectiveness of decremental diameter balloon catheters (tapered balloon)

Natural tapering of coronary arteries from larger proximal to smaller distal diameters often creates a dilemma for optimal balloon sizing during percutaneous transluminal coronary angioplasty (PTCA). To demonstrate the need for new dilating catheters suitable for tapered coronary anatomy, 100 consecutive coronary arteries were measured by videodensitometry, 1 cm proximal and distal to the stenosis. In 23 arteries there was a 1 mm or greater taper and 19 arteries showed a 0.5 to 0.99 mm taper. Only 50 arteries showed a nearly uniform diameter at the site of the stenosis, and 8 arteries demonstrated reverse taper, i.e., distal was greater than proximal diameter. To avoid balloon size mismatch with significant tapering, decremental diameter balloon catheters were developed. Series I tapers from 3.5 to 3.0 mm and series II from 3.0 to 2.5 mm over a balloon length of 25 mm. Tapered balloons were used in 80 patients with 94 tapered coronary arteries. Before PTCA, proximal, stenotic and distal mean diameters measured 3.6, 1.1 and 2.6 mm, respectively; after PTCA, proximal, stenotic and distal diameters measured 3.6, 2.8 and 2.5 mm, respectively, thus maintaining the natural tapering after effective dilatation. Only 2 arteries (2.1%) showed significant dissection, with no abrupt occlusions, and none requiring bypass surgery. In summary, decremental diameter balloon catheters provide optimal dilation in tapered arterial segments with few complications and offer a new approach to balloon sizing.