A new approach to planning in vitro and in vivo experiments for cardiovascular stents. (2) Planning of experiments

Copyright @ 2000 Pacini Editore SpAWithin our overall project to improve the design of stents in terms of reduced rates of re-stenosis, there are three main methods, namely computer simulation and in vitro and in vivo experiments. These methods are closely integrated using contemporary design procedures described below, especially to accommodate patient-to-patient variation. Clinical experience shows that a small variation has considerable effects on flow characteristics of stents and in engineering terms may be described as a ‘geometric risk factor’. The Robust Engineering Design procedure readily incorporates this factor which may thus become a component feature in our experimental planning. We envisage that this approach could be applied to other invasive implants with a view to enhancing their quality

756-1 Non Surgical Septum Reduction: A New Treatment for Hypertrophic Obstructive Cardiomyopathy (HOCM)

In patients with HOCM and marked intraventricular gradients resistant to conventional drug treatment with beta blockers and/or Verapamil surgical resection of the muscular septal bulge has been advocated. We have investigated a new catheter treatment in 5 patients with HOCM and significant LV ouflow tract gradients. All patients were in class 3 NYHA with angina and shortness of breath. Intraventricular gradients were measured with transeptally introduced Brockenbrough catheters in the LV inflow tract and arterial catheters in the aortic root. All patients were studied at rest, during the Valsalva manoeuvre, after nitrates and after Isoproterenol infusion. The measurements were repeated during balloon occlusion of the first major septal branch of the left anterior descending coronary artery. — In all patients the resting intraventricular gradient was reduced to less than 20mm/Hg and provocative testing (nitrates and post extrasystolic potentation) failed to create typical increments. The longest inflation time was 30 minutes. Three patients had Verapamil 0.5mg injected through the angioplasty balloon which resulted in a longer lasting gradient/reduction after deflation of the balloon.–After informed consent, 2 patient had 3–5ml of desiccated alcohol infused through the inflated balloon catheter in order to devitalise the offending myocardium. This resulted in a CK elevation up to 2,500 units and permanent abolition of the intraventricular gradient accompanied by marked clinical improvement.From these preliminary observations we conclude that non surgical septum ablation maybe a promising new technique for the treatment of HOCM. Further studies are warranted

Conversion of supraventricular arrhythmias to sinus rhythm using flecainide

We evaluated the efficacy of flecainide acetate (given intravenously to a maximal dose of2 mg kg−1 and then orally in a dose of 100 mg b.d. or 100 mg t.d.s.) in the conversion to sinus rhythm of 50 patients exhibiting supraventricular arrhythmias (39 with atrial fibrillation, 6 with atrial flutter, 4 with supraventricu tachycardia and onewith supraventricular tachycardia in association with the Wolff—Parkinson—White syndrome). Conversion was achieved in 36 patients (72%) (29 cases with atrial fibrillation, 4 cases with supraventricular tachycardia, 2 cases with atrial flutter and one case with Wolff—Parkinson-White syndrome), over a mean period of 7.4 ± 9 h. The patients in which conversion was achieved had arrhythmias which had been in existence for a shorter time (5.3 ± 9.8 days) than those in which conversion was not achieved (16.7 ± 26.2 days) (P<0.01). The mean dosage of flecainide used to achieve conversion was 2.5 ± 2.36 mg kg−1. Flecainide appears to be an effective agent for the conversion to sinus rhythm of atrial fibrillation and supraventricular tachycardias. Its efficacy in cases of atrial flutter has not yet been demonstrate

Prevention of coronary restenosis by stenting

Balloon angioplasty fails to provide acceptable long-term results for a significant proportion of patients. An intravascular mechanical support, developed with the aim of preventing restenosis and acute closure of diseased arteries after transluminal angioplasty, was implanted in 44 patients (39 male and five female), aged from 35 to 70 years (mean 56 years) with documented restenosis of native coronary artery (41 stents) and bypass grafts (12 stents). In the group of bypass graft patients there was no local restenosis and no major complication. In patients in whom stents were placed in native coronary arteries, the complication rate was higher (two patients died after coronary bypass surgery). One patient died suddenly at home. Except for one patient, in whom a new lesion developed proximally with extension into the stent, no case of restenosis could be observed. Despite the still relatively high complication rate, we feel that stenting may present a rational approach to the unresolved problem of restenosis after coronary angioplast

Conversion of supraventricular arrhythmias to sinus rhythm using flecainide

We evaluated the efficacy of flecainide acetate (given intravenously to a maximal dose of 2 mg kg-1 and then orally in a dose of 100 mg b.d. or 100 mg t.d.s.) in the conversion to sinus rhythm of 50 patients exhibiting supraventricular arrhythmias (39 with atrial fibrillation, 6 with atrial flutter, 4 with supraventricular tachycardia and one with supraventricular tachycardia in association with the Wolff-Parkinson-White syndrome). Conversion was achieved in 36 patients (72%) (29 cases with atrial fibrillation, 4 cases with supraventricular tachycardia, 2 cases with atrial flutter and one case with Wolff-Parkinson-White syndrome), over a mean period of 7.4 +/- 9 h. The patients in which conversion was achieved had arrhythmias which had been in existence for a shorter time (5.3 +/- 9.8 days) than those in which conversion was not achieved (16.7 +/- 26.2 days) (P less than 0.01). The mean dosage of flecainide used to achieve conversion was 2.5 +/- 2.36 mg kg-1. Flecainide appears to be an effective agent for the conversion to sinus rhythm of atrial fibrillation and supraventricular tachycardias. Its efficacy in cases of atrial flutter has not yet been demonstrated