Modulation of Healthy Pig Coronary Arteries by Self-Expanding Stents

Objectives: To evaluate the expansion ratio of a self-expanding stem over time, and the chronic effect of stent pressure on the vessel wall . Methods: Self-expanding stents, developed by Medtronic Inc. (Minneapolis, MN, USA) and the Rouen group (Letac, Cribier, France), were implanted in 21 normal pig coronary arteries. Animals were sacrificed after recatheterization at 1 day (group I, n = 4), I week (group 2, n = 3), 3 weeks (group 3, n = 5), or 8 weeks (group 4, n = 4). Histological morphometry of the vessel medial and neointimal layers was performed. Changes were related to the, stent diameter and. its force on the vessel wall . Results: The stent expansion ratio gradually increased from 73% to 93% after 8 weeks, which implicates that radial force decreased concomitantly from 0.10 N to 0.03 N. Media compression under the rods ranged from 4l%-66% immediately after stent implantation. The mean compression was unrelated to stent expansion and remained nearly the same (40%-50%) during follow-up. Individual media rod compression ranged from 5%-95%. The neointimal layer on top of the rods increased until the third week after stent implant (neointimal thickness 211 ± 108 μm). The layer significantly decreased at 8 weeks (neointimal thickness 65 ± 9 μm). The cross-sectional neointimal area increased gradually only at the end of the stent during the 8-week follow-up . Conclusions: The self-expanding stent implanted in normal pig coronary arteries reached a gradual relaxation state 8 weeks after implantation due to the persistent radial force. This radial force induces medial wall compression, which was only positively related to the thickness of the neointimal layer at 3 weeks after implant . (J Interven Cardiol 1996;9:45–52)     

Decreased insulin secretory capacity and normal pancreatic B-cell glucose sensitivity in non-obese patients with NIDDM

We investigated the dose-response characteristics of glucose-induced insulin release and the influence of hyperglycaemia on arginine-induced insulin secretion in eight non-obese subjects with NIDDM and in eight non-diabetic volunteers. Plasma C-peptide levels, achieved during 60 min hyperglycaemic clamps with and without the infusion of a primed continuous infusion of arginine (infusion rate 15 mg kg-1 min-1) during the last 30 min, were analysed with a modified Michaelis-Menten equation. The insulin secretory capacity (Vmax) for glucose-stimulated insulin release showed a trend towards a negative correlation with the fasting blood glucose in the NIDDM subjects (r = 0.68, P = 0.6); it was lower than the Vmax of non-diabetic controls (2.2 +/- 0.2 vs 4.2 +/- 0.4 nmol l-1 respectively; P less than 0.001). The ED50 (half maximal stimulating blood glucose concentration) of the second-phase glucose-stimulated insulin release (determined from the plasma C-peptide levels at 60 min) was not significantly different from the ED50 of the controls (11.9 +/- 0.8 vs 13.3 +/- 1.9 mmol l-1 respectively; P greater than 0.2). Combined glucose-arginine stimulation significantly increased insulin release. The Vmax for both phases were significantly lower in NIDDM patients than in controls (2.3 +/- 0.2 vs 5.0 +/- 0.9 and 3.8 +/- 0.5 vs 8.5 +/- 0.9 nmol l-1 respectively; P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Computed Tomography During Experimental Balloon Dilatation For Calcific Aortic Stenosis. A Look into the Mechanism of Valvuloplasty

Thin-slice contiguous computed tomographic scanning was performed in four postmortem hearts with calcific aortic valve stenosis (mean weight: 583 ± 78 g; mean age: 65 ± 10 years) before, during, and after balloon valvuloplasty. Balloons of increasing diameter (15–19 mm single balloons, and 3 × 12-mm trefoil-shaped balloon) were positioned across the aortic valve and manually inflated to pressures of 3 to 4 atmospheres. During inflation of the 3 × 12-mm balloon a larger residual orifice, potentially free for blood passage, was observed in the two cases with bicuspid valves and in one case with a fused tricuspid valve, while the reverse was noted in one case with a tricuspid valve without fusion. In most cases valvular orifice enlargement only occurred with larger diameter balloons. After valvuloplasty aortic valve area increased from 0.72 (range 0.20–0.95) cm² to 2.36 (range 0.95–3.14) cm². The smallest orifice enlargement after dilatation occurred in case 1, where valvular calcified deposits had the largest volume and the highest computed tomographic attenuation value. In each patient macroscopic changes (fracture of nodular calcifications, commissural splitting, tearing of the central raphe) were noted. No calcium dislodgement or aortic ring damage was observed. In autopsy specimens computed tomography provided accurate evaluation of aortic valve morphology, extent of valve calcification, balloon-leaflet relationship during inflation, and effects of the dilatation on valve leaflets and commissures. Advances in computed tomographic cardiovascular imaging may achieve similar results in the clinical setting, and allow a more rational, individualized approach to the valvuloplasty procedure. (J Interven Cardiol 1988:1:2)     

Pleomorphic adenoma of the vulva: a review illustrated by a clinical case

The pleomorphic adenoma of the vulva is an extremely scarce diagnosis. This form of neoplasm is more frequently observed in other topographic sites of the human body. Treatment modalities largely derive from experiences with the pleomorphic adenoma located in these other sites. As a result of similarity with other tumors and scarcity of the neoplasm, the diagnosis of pleomorphic adenoma of the vulva is easily missed in daily routine practice. Recurrences of this neoplasm are frequently observed with an estimated incidence of malignant transformation of 25%. Addressing this previously mentioned issue, an extensive surgical excision and long-term follow-up is advocated. This report is illustrated by the case of a 66-year-old woman who was admitted to our hospital with a pleomorphic adenoma of the vulva, diagnosed by pathologic assessments following surgical excision. As a result of the rarity of this diagnosis, characteristics and treatment of extravulvar in addition to vulvar localizations of the pleomorphic adenoma are reviewed.     

Upper Limit Ventricular Stimulation in Respiratory Rate Responsive Pacing due to Electrocautery

Transient programmed upper limit stimulation (150 bpm) was observed during repetitively utilized electrocautery in the beginning of an open-heart surgical procedure in a patient with a minute ventilation rate responsive ventricular pacemaker. This tachycardia caused severe hemodynamic deterioration, and was also initiated by internal heart massage and manual ventilation. Considering the recommendations of the manufacturer, this series of serious events could have been prevented, when reprogramming to the inhibited mode had been executed in anticipation of the operation.