Biomedical subjects

G Bayet

Publications and source records attributed to G Bayet.

9 recordsLinked to original sources

PubMed2000

Elastic recoil of coronary stents: a comparative analysis.

Minimum elastic recoil (ER) has became an essential feature of new coronary stents when deployed in artheromatous lesions of various morphologies. The ER of coronary stent might be an important component of 6-month restenosis rate by minimizing the luminal loss. We evaluated the intrinsic ER of 23 coronary stents with a mechanical test bench. The amount of ER for one size of stent (3.0 mm) was quantified using a 3D optical contactless machine (Smartscope MVP, Rochester, NY). The stents were expanded on their own balloon for the precrimped stents; the uncrimped stents were expended using identical 3.0-mm balloons. Two types of measurements were done without exterior stress and with a 0.2-bar exterior stress, directly on the stent at the end of balloon expansion, immediately after balloon deflation, and then 30 min, 60 min, and 120 min after. ER ranged from 1.54%+/-0.81% (Bestent BES 15) to 16.51%+/-2.89% (Paragon stent) without stress (P<0.01) and from 2.35%+/-1.14% (Bestent BES 15) to 18.34%+/-2.41% (Cook GR2) under 0.2-bar pressure (P<0.0001). Furthermore, there was a significant reduction between the mean result of tubular stents (TS) and coil stents (CS). The results of in vitro mechanical tests may confirm strongly the interest of a minimum ER in the prevention of the 6-month restenosis.

Angioplasty, Balloon, Coronary↗

PubMed2000

Unprotected left main coronary artery stenting: immediate and medium-term outcomes of 140 elective procedures.

OBJECTIVES: We sought to evaluate immediate and late outcomes after stenting for left main coronary artery (LMCA) stenosis. BACKGROUND: Conventional percutaneous transluminal coronary angioplasty (PTCA), for which coronary artery bypass grafting (CABG) has been the gold standard therapy for years, has yielded poor results in unprotected LMCA lesions. The development of coronary stents, together with their dramatic patency improvement provided by new antiplatelet regimens and their validation against restenosis, warrants a reappraisal of angioplasty in LMCA stenosis. METHODS: From January 1993 to September 1998, 140 consecutive unselected patients with unprotected LMCA stenosis underwent elective stenting. Group I included 47 high-CABG-risk patients, and group II included 93 low-CABG-risk patients. Ticlopidine without aspirin was routinely started at least 72 h before the procedure and continued for one month. Patients were reevaluated monthly. A follow-up angiography was requested after six months. RESULTS: The procedure success rate was 100%. One-month mortality was 9% (4/47) in group I and 0% in group II. A follow-up angiography was obtained in 82% of cases, and target lesion revascularization was required in 17.4%. One-year actuarial survival was 89% in the first 29 group I patients and 97.5% in the first 63 group II patients. CONCLUSIONS: Stenting of unprotected LMCA stenosis provided excellent immediate results, particularly in good CABG candidates. Medium-term results were good, with a restenosis rate of 23%, similar to that seen after stenting at other coronary sites. Stenting deserves to be considered a safe and effective alternative to CABG in institutions performing large numbers of PTCAs.

Adult↗

PubMed1997

Coronary artery stenting without anticoagulation, aspirin, ultrasound guidance, or high balloon pressure: prospective study of 1,051 consecutive patients.

Between March 1994 and November 1995, 1,212 coronary stents were implanted in 1,051 consecutive patients at our institution with the following protocol: daily pre- and poststenting treatment with ticlopidine 500 mg without aspirin, implantation under angiographic guidance, without ultrasound, with semi-compliant balloons inflated at 10 bars. Stenting was indicated after failure of balloon angioplasty (bail-out, dissection, elastic recoil) in 27% of the patients and considered as elective (de novo, restenosis, chronic occlusion, saphenous vein grafts) in 73% of the cases. During the 30-day follow-up period, stent thrombosis occurred in 11 patients (1.0%) and vascular access-site complications in three patients (0.3%). Thirteen patients (1.1%) died, 10 from previous left ventricular failure, 3 (0.3%) from subacute thrombosis. Multivariate analysis revealed that the size of the last balloon used was associated with subacute stent thrombosis Thus, in nonselected patients, placement of coronary stents may be safely achieved without use of warfarin, post procedural heparin, high balloon pressure, or ultrasound guidance. Antiplatelet therapy with ticlopidine and angiographic guidance result in a stent thrombosis rate of 1% and a vascular complication rate of 0.3%.

Adult↗

PubMed1994

[Pilot study of the efficacy of ticlopidine in early patency of coronary endoprostheses].

Subacute thrombosis of coronary stents is the main complication of this technique. The authors studied the outcome of 387 patients and 400 coronary arteries who underwent implantation of 427 stents between December 1989 and February 1994 and followed up one month after the procedure: all patients receive 500 mg of ticlopidine daily from three days before angioplasty throughout the hospital period and continued for at least one month. Anticoagulation with heparin was undertaken by the intravenous route after implantation and relayed with subcutaneous heparin for one week until control coronary angiography performed in the first 300 patients. At one month, 96.9% of patients were free of clinical coronary events. The following major complications were observed: 5 deaths (1.3%), 5 Q wave myocardial infarctions (1.3%); no emergency bypass surgery. The peripheral vascular complication rate was 3.6%. Univariate analysis three risk factors of subacute thrombosis: age (p = 0.0058), arterial diameter of less than 3 mm (p < 0.01) and implantation for occlusive dissection (p = 0.03). Multivariate analysis showed two independent risk factors: age (p = 0.001) and arterial diameter of less than 3 mm (p = 0.01). This pilot study shows a particularly low subacute thrombosis rate in unselected indications with an acceptable level of vascular complications.

Adult↗

PubMed1993

[Torsades de pointes].

Torsades de pointes are defined and characterised by specific, polymorphic but organised ventricular activation on the surface electrocardiogram. They constitute episodes of rapid tachycardia which are usually short lasting and terminate spontaneously. However, they may recur and persist, leading to syncope or sudden death. They occur typically in cases with abnormalities of ventricular repolarisation with prolongation of the QTU interval and variable deformations of the TU waves. The basal abnormalities may be modest or intermittent. A bigeminy with a long coupling interval and alternating long and short cycles often precede the burst of arrhythmia. Abnormalities of ventricular repolarisation and torsades de pointes may be the result of congenital syndromes (catecholamine-dependent torsades) or acquired factors (pause-dependent torsades) such as paroxysmal bradycardia, drugs which prolong the repolarisation and potassium and magnesium deficiencies. The electrophysiological mechanisms comprise reentry and after depolarisation induced activity genetic factors causing abnormalities of the G-proteins, potassium currents or adrenergic receptors may also play a role. Emergency treatment consists of intravenous magnesium salts, sometimes of betablockers or verapamil for maintenance therapy. The association of a potassium-sparing drug may be useful. Cardiac pacing may be necessary. Left sympathetic denervation or implantation of an automatic defibrillator are exceptional therapeutic options in refractory congenital torsades de pointes.

Death, Sudden, Cardiac↗

PubMed1992

[Quantitative thallium myocardial tomoscintigraphy. Value of intravenous infusion of dipyridamole after negative submaximal exercise test].

Patients with suspected coronary artery disease are sometimes unable to exercise adequately (85% of age calculated maximal heart rate) to validate their ergometric stress test. Some groups suggest performing dipyridamole scintigraphy from the outset but then the information provided by exercise stress testing is lost. The aim of this study was to compare scintigraphies performed after exercise alone and after exercise combined with dipyridamole using a method of quantification. Thirteen patients with ischaemic heart disease without necrosis (coronary lesions greater than 75% luminal narrowing in: 7 right coronary, 10 left anterior descending, 3 left circumflex arteries and 1 left main coronary artery with 50% luminal narrowing) underwent exercise stress testing followed by Thallium imaging. One week later, the same exercise stress test was performed followed by an intravenous injection of dipyridamole and Thallium scintigraphy. The circumference of the radioactivity was traced and the surface of each segment calculated in three different short axis views, subdivided into 4 segments (anterior, lateral, inferior and septal walls). Any segment vascularised by a stenosed coronary artery was considered to be underperfused (105 segments). The ratios of the surfaces of underperfused/normal segments were compared using the two study protocols. Segments of the same wall in the 3 short axis views were grouped in the same myocardial zone. Thirty five myocardial zones were thus obtained: 25 zones were more underperfused after combining exercise and dipyridamole than after simple exercise stress (p = 0.014). The average increase in underperfusion after the combined exercise-dipyridamole was 12.4% compared with 5.5% after exercise alone (p = 0.03). Secondary effects were minimal.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Disease↗

PubMed1989

[Evaluation of pulmonary arterial hypertension by Doppler echocardiography in chronic respiratory insufficiency].

The usefulness of doppler-echocardiography for the assessment of pulmonary arterial hypertension in patients with chronic respiratory failure was evaluated in 24 consecutive patients with chronic obstructive lung disease. Seventeen of these 24 patients (71 p. 100) who had tricuspid valve regurgitation analysable by the continuous wave doppler technique were selected as study group; they included 15 men and 2 women aged from 33 to 78 years (mean 63 years). The highest maximum velocity value (method A) or the maximum velocity value averaged on several cycles (method B) of the tricuspid regurgitation jet was used to calculate the right ventriculo-atrial pressure gradient, using Bernouilli's equation. Right atrial pressure was determined by three methods: haemodynamic measurement, clinical evaluation or attribution of an arbitrary 10 mmHg value. The pulsed doppler study of the pulmonary ejection flow included measurement of the acceleration time and calculation of the acceleration time/ejection time ratio. The usual echocardiographic parameters were measured. Catheterization was performed 2.5 days on average after the doppler study. Correlations between doppler examination and catheterization to evaluate the right ventricular systolic pressure were significant (p less than 0.001) and better with method B than with method A. Depending on the method employed to evaluate the right atrial pressure, the correlation coefficients obtained with method B were: 0.93 (haemodynamic measurement), 0.91 (clinical evaluation) and 0.88 (arbitrary value of 10 mmHg). The right ventricular systolic pressure evaluated by doppler ultrasound using method B and by clinical evaluation of the right atrial pressure was 47 +/- 12 mmHg (22 to 70 mmHg), as against 51 +/- 13 mmHg (28 to 74 mmHg) measured by catheterization.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1989

[Value of the calibration of coronary angioplasty balloons].

A total of 197 polyethylene balloons of 2 to 4 mm diameter were inflated to 1 to 10 atmospheres to determine the variations of size with respect to pressure of inflation. A linear relationship was observed between diameter and pressure of inflation. The slope of this relationship represents the compliance. Balloons of the same diameter have almost identical compliances. The compliance of the balloon increases with size. The specified diameters are obtained with pressures of less than 6 atmospheres. However, the variations of size of a given balloon are important. This study shows that attention should be paid to the calibration of balloon catheters before angioplasty to avoid the risks of over-dilatation. New balloons made of therephtalane polyethylene are much less compliant and do not present this type of problem.

Angioplasty, Balloon, Coronary↗

PubMed1988

[Acquired systemo-pulmonary fistula after pleurectomy responsible for a continuous thoracic murmur].

Systemo-pulmonary fistulae are rare. The case of a 27 year-old man, hospitalized for exploration of a continuous thoracic murmur, is reported. A right pleurectomy had been performed 2 years previously because of a recurrent spontaneous pneumothorax, and no murmur was present at that time. Angiography showed a systemo-pulmonary fistula with the right internal mammary artery and branches of the right axillary artery as afferent vessels, and the right pulmonary arteries and veins as efferent vessels. Blood gases measurements demonstrated a left-right shunt. The acquired nature of the fistula was suspected because of the history of right pleurectomy and the acquired nature of the murmur. There was no indication for surgery because of the complexity of the fistula and the absence of symptoms.

Adult↗