Promises and pitfalls of new devices for coronary artery disease

The management of enthusiasm: motives and expectations in cardiovascular medicine

Debates about appropriate action in medicine often turn on finding the right emotional orientation to new developments. In this article enthusiasm emerges as a key term in a professional 'vocabulary of motive' around innovation, complicating current sociological interest in expectations. The negative associations that adhere to this word among clinical researchers indicate awareness with the difficulty of managing hype and public hopes, but analysis of its use by cardiologists over the past two decades also reveals tension around more specific professional dangers, including 'credulity' and inappropriate activism. An emphasis on clinical trials offers one resolution, but additional narrative strategies can be identified when discussing when to start such trials here illustrated for stem cells for cardiac repair. In particular, while some suggest delaying trials until there is good knowledge of mechanism gained in the laboratory, others support early clinical research through gestures of therapeutic and epistemic modesty.

Frequency and predictors of major in-hospital ischemic complications after planned and unplanned new-device angioplasty from the New Approaches to Coronary Intervention (NACI) registry

The purpose of this study was to determine the frequency and predictors of major in-hospital ischemic complications after planned and unplanned procedures with new angioplasty devices from the New Approaches to Coronary Intervention (NACI) registry. The NACI registry is a multicenter, voluntary reporting of consecutive patients undergoing new-device angioplasty procedures using atherectomy catheters, stents, or lasers. This registry affords the opportunity to evaluate the performance of new angioplasty devices during elective and urgent circumstances. The study population consisted of 3,340 patients with 3,733 lesions (2,921 in native coronary arteries and 812 in saphenous vein grafts [SVGs], who were treated with new devices over a 3.5-year period and had their angiograms analyzed independently at a central angiographic core laboratory. Their in-hospital course and multivariate predictors of the complications in planned and unplanned procedures, further divided into native and SVG lesions, were evaluated. In 82.2% of native coronary artery lesions and 96.9% of SVG lesions, the procedure with a device had been planned due to unfavorable lesion characteristics for PTCA. In the remaining lesions, device use was unplanned, and was performed mainly to treat a suboptimal result (59-80.4%) after percutaneous transluminal coronary angioplasty (PTCA), and less frequently after important complications of PTCA including abrupt closure and PTCA failure. In native artery cohort, major in-hospital ischemic complications (death, Q-wave myocardial infarction [MI], or emergency coronary artery bypass surgery) occurred in 2.7% of the planned and 9.9% of the unplanned procedures (p < 0.001), whereas in SVG such complications occurred in 3.6% of the planned and 8.7% of unplanned procedures (p = 0.21). Multivariate analysis revealed several predictors of major ischemic complications from planned native coronary artery device use: post-MI angina (odds ratio = 2.83); severe concomitant noncardiac disease (odds ratio = 2.5); multivessel disease (odds ratio = 1.75); and de novo lesions (odds ratio = 2.3). Multivariate predictors of major complications in unplanned native coronary artery procedures included high surgical risk (odds ratio = 3.08), and tortuous lesion (odds ratio = 2.41). In SVG lesions, the independent predictors of major complications for planned procedures included age (odds ratio = 1.09), high surgical risk (odds ratio = 4.34), and thrombus (odds ratio = 2.62). In native and SVG lesions, rates of major complications of planned procedures was acceptable (2.7-3.67%), but unplanned use of a new device was associated with a significantly higher rate of in-hospital complications (approximately 9%). Multivariate predictors for major ischemic complications included both clinical and lesion characteristics, and differed for native versus SVG lesions, as well as for planned versus unplanned procedures.

Reliability of the quantitative angiographic measurements in the New Approaches to Coronary Intervention (NACI) registry: a comparison of clinical site and repeated angiographic core laboratory readings

To assess the agreement of clinical site and angiographic core laboratory readings obtained in the New Approaches to Coronary Intervention (NACI) registry, we reviewed the angiographic results obtained in 787 lesions assessed both by the sites and the core laboratory, including 135 lesions analyzed twice (> or =2 months apart) by the angiographic core laboratory. Although moderate agreement was demonstrated between the clinical site and angiographic core laboratory for qualitative lesion morphology such as lesion calcium (kappa [kappa] = 0.42), only fair agreement was found between site and core laboratory estimation of lesion ulceration (kappa = 0.33); thrombus (kappa = 0.30); and eccentricity (kappa = 0.27); with poor agreement for angulation (kappa = 0.16); and proximal vessel tortuosity (kappa = 0.03). Agreement for qualitative morphology was better for repeated core laboratory readings of lesion eccentricity (kappa = 0.75); angulation (kappa = 0.72); thrombus (kappa = 0.68); proximal vessel tortuosity (kappa = 0.66); and calcification (kappa = 0.64). Quantitative angiographic measurements correlated moderately between the clinical site using the digital caliper method and the core laboratory using the automated edge-detection method, including preprocedural percentage diameter stenosis (intraclass correlation [R] = 0.50) and postprocedural percentage diameter stenosis (R = 0.63). Repeated core laboratory readings had almost perfect agreement, with R ranging from 0.88 for postprocedural percentage diameter stenosis to 0.93 for reference vessel diameter and pre- and postprocedural minimal lumen diameters. Repeated angiographic core laboratory readings provided highly consistent quantitative and qualitative morphologic results in the NACI registry, but the core laboratory readings varied substantially from those obtained at the clinical site. More standardized angiographic analytic criteria and core laboratory feedback to investigators may improve agreement between the clinical sites and the angiographic core laboratory in subsequent studies.

Stents wrapped in autologous vein: an experimental study

OBJECTIVES

A new type of coated stent, consisting of a conventional stent covered by an autologous vein graft, was developed at our institution.

BACKGROUND

Coated stents are under investigation to address stenting limitations. However, experimental implantation of coated stents covered by autologous tissue has not been reported.

METHODS

An autologous vein graft was removed and carefully prepared. Subsequently, a Palmaz stent was covered by the vein graft both internally and externally. Twenty-seven stents were implanted in the normal iliac arteries of 27 pigs weighing 18 to 33 kg. In 15 of the pigs, 15 noncoated Palmaz stents were implanted in the contralateral artery; these animals served as the control group. The animals were followed up angiographically for a period ranging from 7 days to 6 months. At the time of death, the stented segments were removed, and histomorphometric analysis was performed.

RESULTS

Autologous vein graft-coated stent preparation and implantation was feasible and uncomplicated. In both stents, angiographic follow-up revealed the absence of thrombosis, except for two cases of subacute thrombosis in the control group. The thickness of the intimal layer was greater in the coated stents and seems to be due to the existence of the internal vein layer ([mean +/- SD] 0.57 +/- 0.12 vs. 0.27 +/- 0.13 mm, p = 0.001). The arterial media of the coated stent segments was thinner than that in the control group (0.14 +/- 0.03 vs. 0.18 +/- 0.01 mm, p = 0.02).

CONCLUSIONS

The autologous vein graft-coated stent seems to be nonthrombogenic, and only minimal hyperplasia was observed in the pigs. Further studies are needed to explore the efficacy of this technique in humans.

Dislocation of the rotating cutter during directional coronary atherectomy: a note of caution

Directional coronary atherectomy (DCA) has received increased attention, especially as a bail-out procedure after failed balloon angioplasty. However, this technique may also be burdened by severe pitfalls. We report a patient with a balloon-resistant left coronary artery lesion subsequently treated with DCA. Despite its over-the-wire guidance, as the rotating cutter was advanced, it deviated from its intra-housing course and intruded into the vascular wall. Dislocation of the rotating blade was due to pressure from hard plaque tissue. After having carefully pulled back the complete catheter system, a severe spasm of the left main stem occurred, which was reversed by intracoronary nitroglycerine. The final angiography showed a left coronary artery without significant, residual stenosis. The case report underscores that DCA passes must be performed under continuous fluoroscopic control, especially for balloon-resistant lesions because of the unpredictability of DCA-imminent complication.

Observational versus randomized medical device testing before and after market approval--the atherectomy-versus-angioplasty controversy

Percutaneous transluminal coronary angioplasty was developed in the late 1970s as a nonsurgical alternative for revascularization of atherosclerotic coronary arteries. It gained widespread acceptance without a controlled trial. Introduced in 1986, directional coronary atherectomy was the first of other recently developed coronary devices that sought to improve on the results of angioplasty. It was approved in 1990 by the Food and Drug Administration (FDA) on the basis of observational data. Its use expanded rapidly, reaching over 35,000 procedures in 1992, accounting for more than 10% of all interventions. After premarket approval, two major randomized trials tested the hypothesis that atherectomy would be superior to angioplasty. Their results raised a cautionary flag and stood in contrast to projections made from prior observational data. It is concluded that randomized controlled trials validate claims of relative efficacy and safety of competing medical technologies, a lesson reflected in recent changes in policy at the FDA.

Resection of guide catheter fragments during coronary atherectomy in aorto-ostial lesions: a note of caution

Angioplasty of coronary aorto-ostial lesions is considered to be troublesome with decreased acute and long-term results and high complication rates. We report a patient with an ostial right coronary artery lesion which was treated after failed PTCA with directional atherectomy as a rescue intervention. After a favorable angiographic and clinical outcome, plastic material was found in the AtheroCath's housing due to resection of the tip of the guide catheter.

Clinical and angiographic outcome after directional coronary atherectomy. A qualitative and quantitative analysis using coronary arteriography and intravascular ultrasound

To assess clinical and angiographic outcome after directional coronary atherectomy, the clinical course of 306 patients undergoing this procedure was reviewed. Directional atherectomy was successful in 290 (94.8%) procedures; complications developed in 8 (2.6%) patients. After atherectomy, percent diameter stenosis was reduced from 71 +/- 14 to 14 +/- 14% (p < 0.001) and minimal lumen diameter was increased from 0.87 +/- 0.42 to 2.55 +/- 0.57 mm (p < 0.001). In 128 (42%) patients, adjunct balloon angioplasty was performed to treat either complications or a residual stenosis > 30%. Intravascular ultrasound was also performed in 57 patients after directional atherectomy and demonstrated that a significant amount of residual plaque mass remained in lesions with a calcium arc > or = 90 degrees (17 +/- 5 mm2 vs 12 +/- 5 mm2 in lesions without calcium; p = 0.007). During the 11 +/- 6 month follow-up period, 69 (28.3%) patients developed recurrent clinical events (death, 5; Q wave myocardial infarction, 8; coronary bypass surgery, 31; coronary angioplasty, 36). Using a proportional hazards model, independent predictors of late clinical events included diabetes mellitus (relative risk [RR] = 1.95; p < 0.05), unstable angina (RR = 2.78; p < 0.005) and a prior history of restenosis (RR = 2.21; p < 0.01). We conclude that directional atherectomy is associated with high procedural success rates and infrequent complications in selected lesions subsets, although the degree of plaque resection may be limited if extensive calcium is present. Late clinical events develop in some (28%) patients after directional atherectomy, related to certain preprocedural clinical risk factors.

Implantation and recovery of temporary metallic stents in canine coronary arteries

OBJECTIVES

The purpose of this study was to test the feasibility of implanting and retrieving a heat-activated recoverable temporary stent and to determine its effect on the angiographic, gross and histologic appearance of a normal coronary artery wall.

BACKGROUND

Permanent coronary stenting is associated with a significant incidence of thrombosis, bleeding and vascular complications. These may be avoided by temporarily stenting for a period of hours to several days.

METHODS

Seventy-eight stents constructed from the shape-memory nickel-titanium alloy nitinol were deployed by balloon expansion in the coronary arteries of 28 dogs and left in place for up to 6 months. Thirty minutes to 1 week after implantation, 70 stents were recovered by flushing the coronary arteries with 3 to 5 ml of 75 degrees C lactated Ringer solution, with collapse of the stent over a recovery catheter and subsequent withdrawal.

RESULTS

All stents were successfully recovered and removed percutaneously. Mean vessel diameter after stenting was 12 +/- 6% (p < 0.05) greater than baseline diameter. Mean vessel diameter after stent removal remained enlarged (6 +/- 3%, p < 0.05). No angiographic or gross evidence of thrombosis, dissection, embolization, migration or spasm was associated with implantation or recovery. Microscopic examination revealed minor intimal injury in 40 segments (51%). Microscopic focal medial necrosis was associated with mural platelet-fibrin thrombus in 23 stented segments (29%) and media was interrupted in 7 (9%).

CONCLUSIONS

This study demonstrates the feasibility of a new method of temporary stenting that uses the thermoelastic properties of nitinol to permit reliable recovery of the stent in normal canine coronary arteries.

Indications for routine heart-catheterization after CABG and PTCA

Routine heart-catheterization after Coronary Artery Bypass Graft surgery (CABG) or Percutaneous Transluminal Coronary Angioplasty (PTCA) has been advocated to determine the change in bypass graft or dilated coronary artery and native coronary artery status, the effective disease remaining after CABG or PTCA and the relation between progression of disease, left ventricular function and symptomatology. Results of angiographic follow-up data after CABG and PTCA are presented and the practical implications are discussed. The reliability of symptoms, invasive and non-invasive test for the detection of ischemia are considered. Finally, recommendations are made for the indication of routine heart-catheterization after CABG and PTCA.

The dynamics of innovation in minimally invasive therapy

The emergence of minimally invasive therapy (MIT), which provides alternatives to major open-surgery procedures, is affecting all aspects of medical care delivery. In the present environment of resource and cost constraint in health services, an uncommon consensus among patients, physicians, providers, and payers has evolved regarding the rapid acceptance of this area of medical intervention, an acceptance that, in turn, is stimulating further innovation. This paper discusses the dynamics of medical innovation and analyzes these forces in the context of three minimally invasive therapies: percutaneous transluminal coronary angioplasty, extracorporeal shock wave lithotripsy, and laparoscopic cholecystectomy. The different experiences of the United States and Europe are used to illustrate how scientific, medical, economic, and regulatory factors affect both the rate and direction of technological change in minimally invasive therapy.

Coronary stenting: single institution experience with the initial 100 cases using the Palmaz-Schatz stent

We studied 100 patients who had coronary implantation of Palmaz-Schatz stents in our institution from November 1989 until March 1991. A total of 126 standard and 6 short stents were implanted. The patients' mean age was 58 +/- 5 years, and 97 were males. The indications were lesions with high risk of restenosis (29 patients), restenosis (27 patients), suboptimal result of angioplasty (24 patients), dissection (16 patients), and recanalized chronic total occlusion (6 patients). In 17 patients a brachial cut-down approach was used. Stents were correctly placed in 98 patients. Stent related complications occurred in 9 patients: major ischemic complications in 7 patients (acute myocardial infarction in 2 patients, emergency bypass surgery in 3 patients and emergency angioplasty in 2 patients); in 3 of these patients there was a subacute closure of the stent and in 2 patients there were delivery problems. Vascular complications at the site of arterial puncture occurred in 3 patients (some patients had more than one complication). A learning curve was observed. There was a decrease in the complication rate with the higher number of patients treated: 28% for the first 50 patients and 6% for the last 50 patients. Clinical follow-up was available in all patients. Of the 92 patients eligible for follow-up (7 +/- 2 months), 69 patients were asymptomatic and 23 had recurrence of angina: 19 patients for stent restenosis and 4 patients for coronary artery disease progression. Follow-up angiogram was done in 79/92 (86%) patients: 21 had restenosis (27%).(ABSTRACT TRUNCATED AT 250 WORDS)

Lesion morphology and coronary angioplasty: current experience and analysis

From July 1, 1990 to February 28, 1991, 533 consecutive patients with 764 target vessels and 1,000 lesions underwent coronary angioplasty. Procedural success was achieved in 92.3%, untoward (major cardiac) events occurred in 3% (0.8% myocardial infarction, 1.3% emergency coronary bypass grafting and 0.9% both; there were no deaths). An unsuccessful uncomplicated outcome occurred in 4.7%. Lesion analysis using a modified American College of Cardiology/American Heart Association classification system showed that 8% were type A, 47.5% were type B and 44.5% were type C (36% of type B and 11% of type C were occlusions). Angioplasty success was achieved in 99% of type A, 92% of type B and 90% of type C lesions (A vs. B, p less than 0.05; B vs. C, p = NS; A vs. C, p less than 0.01). Untoward events occurred in 1.2% of type A, 1.9% of type B and 2% of type C lesions (p = NS). An unsuccessful uncomplicated outcome occurred in 0% of type A, 6% of type B and 7% of type C lesions (A vs. B, p less than 0.05; B vs. C, p = NS; A vs. C, p less than 0.05). Among the unsuccessful uncomplicated outcome group, occlusion occurred in 49%: 38% of type B and 59% of type C lesions. With B1 and B2 subtypes, success was obtained in 95% and 89.5% and untoward events occurred in 1.5% and 2.3% and an unsuccessful uncomplicated outcome in 3.7% and 8%, respectively. C1 and C2 subtyping showed success in 91% and 86%, untoward events in 1.3% and 6% and an unsuccessful uncomplicated outcome in 7.5% and 8.5%, respectively. Among the 764 vessels, success was obtained in 89.5% and untoward events occurred in 2.5% and an unsuccessful uncomplicated outcome in 8%. Assessment of lesion-vessel combinations showed a less favorable outcome with type C lesions and combinations of A-B, B-C and multiple (more than three lesions) type B and C vessels. Statistical analysis of morphologic factors associated with angioplasty success included absence of (old) occlusion (p less than 0.0001) and unprotected bifurcation lesion (p less than 0.001), decreasing lesion length (p less than 0.003) and no thrombus (p less than 0.03). The only significant factor associated with untoward events was the presence of thrombus (p less than 0.003). Predictors of an unsuccessful uncomplicated outcome included old occlusion (p less than 0.0001) and increasing lesion length (greater than 20 mm) (p less than 0.001), unprotected bifurcation lesion (p less than 0.05) and thrombus (p less than 0.03).

Postangioplasty restenosis rate between segments of the major coronary arteries

Conflicting data have been published regarding the rate of postangioplasty restenosis observed in diverse segments of the coronary tree. However, these studies may be criticized for their biased selection of patients, methods of analysis, and definitions of restenosis. In the present study, 1,353 patients underwent a successful coronary dilatation of greater than or equal to 1 site. In all, 1,234 patients (91%) had a follow-up angiogram after 6 months, or earlier when indicated by symptoms. All films were processed and analyzed at the thoraxcenter core laboratory with the coronary angiography analysis system (automated contour detection). Restenosis was considered present if the diameter stenosis at follow-up was greater than 50%. No differences in restenosis rates were observed between coronary segments using this categorical definition. A continuous approach was also used; absolute changes in minimal luminal diameter adjusted for vessel size were used in order to allow comparison between vessels of different sizes (relative loss). No significant differences were observed between the coronary segments with this continuous approach. These results suggest that restenosis is a ubiquitous phenomenon without any predilection for a particular site in the coronary tree.

Interventional cardiology techniques for coronary artery disease

This review updates and extends observations made in this journal in March 1988. The focus then was on percutaneous transluminal coronary angioplasty and the clinical results of its practical application. A concern was expressed that science lagged in solving the major problems of rethrombosis and restenosis. The NHLBI Bypass Angioplasty Revascularization Investigation (BARI) study was still in the planning phase. In 1991, the scene has changed. Interventional cardiology now embraces a multitude of different catheter devices--angioplasty, atherectomy, laser, stents. Basic scientists are increasingly involved in addressing the restenosis issue. Our national heart meetings are increasingly oriented towards molecular biology approaches to solving the remaining problems. The BARI trial has nearly completed patient entry, and we eagerly await its results. The cardiologist and surgeon are faced with increasingly complex decisions with respect to interventional technologies, involving not only whether to use them, but which ones.

Advances in coronary interventional techniques

The practice of catheter interventional techniques for coronary artery disease is just 14 years old. Many approaches are being applied, including balloon and rotational angioplasty devices, atherectomy catheters, lasers, and stents. Considerable efforts are being made developing, marketing and comparing these technologies. Restenosis is demanding more attention amongst clinical and basic scientists. The pathophysiology of this frequent and irksome complication is still poorly understood. A number of trials are comparing strategies of PTCA against medicine and surgery. In the United States, the Bypass Angioplasty Revascularization Investigation (BARI) of PTCA versus surgery for patients with multivessel disease has nearly completed patient entry; the preliminary results are eagerly awaited. Patients in nearly all countries are benefiting from these new technologies. Their development and evaluation has been most active in North America, Europe and Japan but many of them are being clinically applied in nearly all countries. Their cost and complexity present special challenges for funding, training and evaluation.