The elective use of the seven-cell NIR stent in coronary arteries < 2.75 mm in diameter: clinical and angiographic results at 6-month follow-up.

The outcome of interventional procedures has been improved by the use of coronary stents in vessels > 3.0 mm in diameter. We report a single-center prospective study of elective coronary stenting in 39 consecutive patients with de novo lesions and reference diameters < 2.75 mm. Seven-cell NIR stents were deployed with standard antiplatelet therapy, but without routine use of IIb/IIIa inhibitors or intravascular ultrasound. There was one case of acute stent thrombosis, but no cases of subacute thrombosis. The binary restenosis rate was 27.8% (10/36 lesions) and the target lesion revascularization rate was 19.4%. Symptoms improved markedly as judged by Canadian Cardiovascular Society and questionnaire scores and the use of antianginal therapy. This pilot study suggests that the elective use of coronary stents in vessels < 2.75 mm in diameter is safe with acceptable long-term results. A randomized trial comparing outcomes after stents and balloon angioplasty in small vessels is required.

In vitro validation of the luminal measurement of a novel catheter based moulding technique.

OBJECTIVE: To investigate a modified angioplasty balloon catheter, which uses a novel balloon polymer to produce luminal moulds. DESIGN: The catheter was tested in polyurethane phantoms of diameter 1.5 to 4.0 mm. Inflations were to 1.4 atmospheres for 20 seconds at 37 degrees C. The moulds were viewed by reinflating the balloon to 0. 34 atmospheres and quantified using macrophotography and caliper measurement. RESULTS: Evidence of systematic error was found with lumen diameters

First clinical experience with a new flexible low profile metallic stent and delivery system.

We report the first clinical use of a new, flexible, low profile, balloon-expandable metallic stent and delivery system (ACS Multi-Link). The stent, designed in an effort to overcome the shortcoming of existing stents, has a low metal mass, superior scaffolding properties and favourable rheological characteristics. It also allows side branch access and is delivered via an innovative stent catheter. Ten stents were used to treat 10 patients with threatened abrupt closure after balloon angioplasty. All were successfully deployed, with a satisfactory angiographic result in nine. The patient with an unsatisfactory angiographic result proceeded to uneventful coronary bypass surgery. There were no other procedural or in-hospital complications. One patient developed restenosis and one had an intra-cerebral bleed following a fall. This new stent thus appears safe and effective when used to treat threatened abrupt closure. Due to its favourable characteristics, it may be well suited for reduction of restenosis. A multi-centre European registry (WEST) for primary implantation in 100 consecutive patients has now been completed.

Aspirin does not affect the flow cytometric detection of fibrinogen binding to, or release of alpha-granules or lysosomes from, human platelets.

1. Aspirin inhibits the conversion of arachidonic acid to thromboxane A2 which reinforces the effects of weak agonists such as ADP in platelets. 2. In this study the effect of aspirin (300 mg/day) on platelet agonist response was measured by whole blood flow cytometry of unfixed blood samples from normal subjects (n = 10), an assay that investigates aggregation-independent changes in the platelet. 3. Fibrinogen binding to unstimulated platelets or to platelets stimulated with ADP or thrombin was unaffected by aspirin. 4. Under the conditions of this assay, platelets undergo a partial degranulation of alpha-granules and lysosomes (evidenced by expression of P-selectin and CD63, respectively) in response to ADP, and full degranulation in response to thrombin. P-selectin expression was paralleled by release of beta-thromboglobulin. None of these events was affected by aspirin. 5. Thromboxane formation was totally prevented by the aspirin treatment, as shown by Born aggregometry in which the platelet aggregatory response to arachidonic acid was abolished and secondary aggregation by ADP was inhibited. 6. The flow cytometric assay can therefore be used to investigate platelets in patients, regardless of aspirin therapy. 7. These findings suggest that platelet fibrinogen binding and the release of platelet alpha-granule and lysosomal contents, in response to stimulation with physiological agonists, can continue in patients despite aspirin therapy. This may help to explain why aspirin is only partially effective in preventing thrombotic events.

Self expanding stents for the management of aorto-ostial stenoses in saphenous vein bypass grafts.

OBJECTIVE: To assess the early and follow up results of implantation of a self expanding stent in aorto-ostial stenoses of vein grafts. DESIGN: Prospective, non-randomised, observational study. SETTING: Tertiary referral centre for cardiac diseases. PATIENTS: Nineteen patients with ostial stenoses of saphenous vein grafts. MAIN OUTCOME MEASURES AND RESULTS: Stents were successfully deployed in all 19 patients with satisfactory angiographic results. In one patient this required two attempts. There were no deaths and no major procedural complications related to ostial stenting. Before discharge two (11%) patients had thrombosis of the ostial stent; one patient had a Q wave myocardial infarction. Femoral artery bleeding occurred in three (16%) patients. Angiographic follow up was performed in 18 patients at a mean of seven months. Restenosis within the ostial stent was detected in three (16%) patients. Twelve (63%) patients had an improved functional status at a mean follow up of nine months. One patient died suddenly at three months. Three (16%) patients required additional revascularisation procedures because of symptoms caused by restenosis within the ostial stent during follow up. CONCLUSIONS: Intracoronary stenting is an attractive treatment for the management of patients with vein graft ostial stenoses.

Removal of a dental post from the bronchus by interventional cardiovascular techniques.

Foreign bodies lodged in the bronchial tree are normally retrieved by bronchoscopy, but if this fails then thoracotomy is necessary. The case history is presented of a patient who had inhaled a dental post which could not be retrieved either by flexible or rigid bronchoscopy. Using biplane screening and intravascular retrieval devices introduced via an endotracheal tube, the dental post was removed successfully without the need for thoracotomy.

Temporary stent as a bail-out device during percutaneous transluminal coronary angioplasty: preliminary clinical experience.

OBJECTIVE: To evaluate the safety and efficacy of a prototype temporary stent (RX Flow Support Catheter, Advanced Cardiovascular Systems) in maintaining coronary perfusion and improving vessel patency in the event of acutely compromised flow complicating percutaneous transluminal coronary angioplasty. DESIGN: Prospective clinical study as part of a multicentre trial. SETTING: Regional cardiac centre catheterisation laboratory. PATIENTS: Eight patients undergoing routine percutaneous transluminal balloon coronary angioplasty in whom coronary artery dissection resulted in impaired coronary artery flow with angina or electrocardiographic ST segment shift, needing bail-out treatment at the time of the procedure. RESULTS: The RX Flow Support Catheter was successfully used and improved coronary flow in all cases, with a reduction in luminal stenosis and resolution of symptoms. The temporary stent was expanded for an average of 85 (range 30-209) minutes. In six patients it was used as a bridge to further treatment (permanent stent in four and coronary artery surgery in two) and two patients did not need further treatment. CONCLUSION: The temporary stent was safe and effective in the acute management of coronary dissection. The main advantages are its ease and speed of use, and successful restoration of coronary flow both to the distal artery and to affected side branches pending definitive treatment.

Self-expanding stents for emergency treatment of acute vessel closure following coronary angioplasty: immediate and long-term results.

Intracoronary stents may be used to treat acute coronary occlusion following balloon angioplasty. We report the immediate and long-term results of emergency implantation of the self-expanding stent (Wallstent) in 39 patients with acute vessel closure. Stents were successfully deployed in 38 patients (97%). Procedural complications occurred in 14 patients (36%); one patient died, two required emergency coronary artery bypass graft surgery, nine sustained myocardial infarcts (one Q wave), and two had acute stent thrombosis successfully treated by intracoronary thrombolysis and repeat angioplasty. Four patients (10%) had femoral artery bleeding, two required surgery. Angiographic follow-up was performed after 6 months in all 34 eligible patients, or earlier for symptoms. Two patients died prior to follow-up angiography. The stented segment was widely patent in 27 of the 34 patients (79%); restenosis within the stent was detected in 4 (12%) and thrombotic stent occlusion occurred in three (9%). Twenty-six of the 39 patients (67%) were free from major cardiac events and symptoms at 1 year. These results suggest that the self-expanding stent provides an attractive alternative to emergency surgery for the treatment of acute coronary occlusion following coronary angioplasty.

Profound platelet degranulation is an important side effect of some types of contrast media used in interventional cardiology.

BACKGROUND: Thrombotic complications occurring during coronary angiography and percutaneous transluminal coronary angioplasty (PTCA) are relatively frequent and can be influenced by the type of radiographic contrast media used. Low osmolar contrast media (LOCM), both ionic and nonionic, have been considered to be safer than the older high osmolar contrast media (HOCM), causing less haemodynamic and symptomatic side effects. Recently, however, nonionic LOCM have been associated with an increased incidence of thrombotic events, including coronary occlusion and stroke. METHODS AND RESULTS: The effects of commonly used contrast media on platelets in native blood were investigated using immunolabeling and flow cytometry to detect platelet activation in vitro. A nonionic LOCM (Omnipaque) caused profound platelet degranulation in nearly 80% of platelets compared with 2 to 3% of platelets in the control. Conversely, an ionic HOCM (Urografin) caused only 25% degranulation, whereas an ionic LOCM (Hexabrix) caused no platelet activation and, furthermore, it inhibited the effects of thrombin on platelets. Platelet degranulation, quantified by immunolabeling, was paralleled by release of beta-thromboglobulin and platelet factor 4 from platelet alpha-granules. Blood from patients anticoagulated with heparin and pretreated with standard-dose aspirin in preparation for PTCA showed the same pattern of contrast media-induced platelet activation as normal subjects. CONCLUSIONS: These results suggest that the type of contrast media used during invasive imaging of the vasculature could have a significant effect on platelets. Platelet degranulation within a PTCA-damaged vessel would be increased by a nonionic contrast medium, releasing procoagulant molecules and platelet-derived growth factors into the damaged vessel lumen, which might contribute to acute thrombosis and the initiation of the restenosis process.

Percutaneous transluminal coronary angioplasty in chronic coronary artery occlusion.

OBJECTIVES: This study was conducted to determine the procedural success rate, complication rate and long-term outcome of percutaneous transluminal coronary angioplasty in chronically occluded coronary arteries. BACKGROUND: Coronary angioplasty of chronically occluded vessels has a lower success rate than has angioplasty of nonoccluded vessels, but it is frequently considered safe because the target vessel is already occluded. The purpose of this study was to determine the reliability of these assumptions at our institution, with the objectives stated above. METHODS: We identified from the angioplasty data base at our institution 100 consecutive coronary angioplasty procedures performed between 1987 and 1991 for chronic total occlusion, defined as complete occlusion (Thrombolysis in Myocardial Infarction [TIMI] grades 0 and 1 flow) for > or = 3 months. The records of the 95 patients who underwent these procedures were reviewed to determine procedural outcome and medium-term results. RESULTS: Procedural success was obtained in 47 occluded vessels (47%). Significantly fewer successes were obtained in the right coronary artery (26.8%) than in either the left anterior descending (57.1%) or the left circumflex (45%) coronary artery (p < 0.05). A procedural failure without serious adverse consequences occurred in 45 procedures (45%), but in eight patients (right coronary artery in five, left anterior descending artery in three) attempted recanalization was complicated by extensive coronary dissection with acute myocardial ischemia, and one of these patients died. There were no emergency operations, but elective coronary artery bypass surgery was undertaken in 26 patients (in 3 after extensive dissection, in 7 after an apparently good result and in 16 in whom the procedure failed). At 12 months after the procedure, 64.1% of those with a procedural success were event free compared with 32.6% of those whose procedure was both unsuccessful and uncomplicated (p < 0.025) and 25% of those in whom it was unsuccessful and complicated by coronary dissection (p < 0.025). CONCLUSIONS: In this series of recanalization of chronically occluded coronary arteries, there was a low procedural success rate, particularly for the right coronary artery. However, when procedural success was obtained, the long-term outlook was good. The overall risk of coronary dissection was comparable to the risk in nonoccluded vessels but was particularly high in the right coronary artery (13%).

Percutaneous coronary intervention for diffuse coronary artery disease.

Patients with diffuse coronary artery disease present a significant management problem. It has been proposed that diffuse coronary disease is unsuitable for balloon angioplasty and surgical treatment is not ideal either. We review the evidence that coronary balloon angioplasty is not a suitable treatment for diffuse coronary disease and examine the role of alternative interventional techniques. New techniques including long angioplasty balloon catheters and atherectomy devices have shown promise. If this is confirmed by prospective randomized trials then coronary angioplasty may yet prove an attractive treatment for diffuse coronary disease.

Femoral arterial hemostasis using a collagen plug after coronary artery stent implantation.

We have investigated the safety and efficacy of sealing the femoral arterial puncture site using purified bovine collagen in the catheter laboratory immediately after coronary stent implantation. Ten consecutive patients, mean age 64.6 years, pretreated with heparin, aspirin, and dextran underwent the insertion of a collagen plug immediately after coronary stent implantation. The mean activated clotting time was 512 seconds (range 320-999). Femoral arterial hemostasis was achieved before leaving the catheterization laboratory in nine of ten patients. Seven of these patients received additional mild groin compression with an air cushion compression device after hemostasis was successful. One of ten patients had persistent bleeding after delivery of the collagen plug and later required blood transfusion. The collagen plug may be a useful adjunct to obtaining hemostasis following coronary stent implantation, but further trials are required to test its reliability in fully anticoagulated patients.

Blood flow and skeletal muscle in patients with heart failure.

The factors that contribute to the symptoms of breathlessness and fatigue, and that limit exercise capacity in patients with chronic heart failure are poorly understood. Recent evidence suggests that the major mechanism is not related to central hemodynamics but to a reduction of skeletal muscle mass and diminished blood flow to skeletal muscle on exercise.

Direct measurement of skeletal muscle fatigue in patients with chronic heart failure.

Skeletal muscle function was measured as force production and fatigue in both the quadriceps (a large locomotive muscle) and adductor pollicis (a small intrinsic hand muscle) in five healthy volunteers, five patients with mild chronic heart failure, and five patients with severe chronic heart failure. The quadriceps of patients with chronic heart failure had a reduced muscle cross sectional area, a reduced maximum isometric force production, and an increased tendency to fatigue. Isometric force production and fatigue of the adductor pollicis, however, were not significantly different between the three groups under control conditions. But during circulatory occlusion fatigue in the adductor pollicis increased more in the patients with severe chronic heart failure. These differing findings in quadriceps and adductor pollicis suggest that skeletal muscle atrophy and reduced isometric force production are not a necessary consequence of chronic heart failure per se, because they were only present in the large locomotive muscle. The normal values for muscle fatigue observed in adductor pollicis in patients with chronic heart failure imply that skeletal muscle blood flow must increase normally during muscle activation when only a small muscle mass is used. These results are not compatible with the concept of a generalised impairment of normal vasodilatation within active skeletal muscle. In contrast, activation of a large muscle, such as quadriceps, results in the rapid onset of fatigue in patients with severe chronic heart failure. This fatigue may be related to the inability of the cardiovascular system to provide the required blood flow for the activation of a large muscle mass. The finding of a relatively greater increase in fatigue of adductor pollicis during circulatory occlusion in patients with severe chronic heart failure supports the hypnosis of an intrinsic abnormality of skeletal muscle in these patients.

Mechanism of the increased ventilatory response to exercise in patients with chronic heart failure.

Minute ventilation, respiratory rate, and metabolic gas exchange were measured continuously during maximal symptom limited treadmill exercise in 30 patients with stable chronic heart failure. The ventilatory response to exercise was assessed by calculation of the slope of the relation between minute ventilation and rate of carbon dioxide production. There was a close correlation between the severity of heart failure, determined as the maximal rate of oxygen consumption, and the ventilatory response to exercise. Reanalysis of the data after correction for ventilation of anatomical dead space did not significantly weaken the correlation but reduced the slope of the relation by approximately one third. These results show that the increased ventilatory response to exercise in patients with chronic heart failure is largely caused by mechanisms other than increased ventilation of anatomical dead space. This finding supports the concept that a significant pulmonary ventilation/perfusion mismatch develops in patients with chronic heart failure and suggests that the magnitude of this abnormality is directly related to the severity of chronic heart failure.

Regional blood flow, muscle strength and skeletal muscle histology in severe congestive heart failure.

Regional blood flow to exercising skeletal muscle is reduced in patients who have undergone treatment for severe congestive heart failure, and is a key factor determining the limitation of exercise capacity. Recent studies have shown that the histology, contractile function and biochemistry of skeletal muscle are also abnormal. The mechanisms for both the reduced blood flow and the intrinsic abnormality of skeletal muscle are unknown. The interpretation of experimental data is complicated by different etiologies of heart failure, drug treatment, exercise protocols, the limitations of methods for the measurement of blood flow and metabolism in intact humans, and by the selection of particular groups of muscles for study that may not reflect changes in other muscles in the body.

Causes of symptoms in chronic congestive heart failure and implications for treatment.

The most common symptoms of patients with heart failure are shortness of breath and fatigue. The causes of these symptoms may be different in various entities encompassed by the general term heart failure, such as acute pulmonary edema, circulatory collapse and chronic heart failure. In patients with acute heart failure, shortness of breath is closely related to left atrial pressure. In patients with chronic heart failure, optimally treated with diuretics, the body fluid compartments are usually of normal size. Recent work strongly suggests that, in such patients, central hemodynamic abnormalities are not the sole determinants of symptoms. Impaired vasodilation and altered metabolism in skeletal muscle, circulating metabolites and pulmonary ventilation-perfusion mismatch with consequent increased physiologic dead space may all contribute to the genesis of symptoms. Consequently, it may be possible to alleviate symptoms by treatments that are not aimed directly at improving central hemodynamics. Whether such an approach could also modify prognosis is unknown.