Delayed occurrence of restenosis in drug eluting stents: an evidence of delayed healing.

Drug eluting stents have made a significant impact on restenosis. However, there are concerns regarding delayed "catch-up" of restenosis. In this case report we present two such patients with delayed occurrence of restenosis after drug eluting stent implantation.

Sample size for collecting germplasms--a polyploid model with mixed mating system.

The present paper discusses a general expression for determining the minimum sample size (plants) for a given number of seeds or vice versa for capturing multiple allelic diversity. The model considers sampling from a large 2 k-ploid population under a broad range of mating systems. Numerous expressions/results developed for germplasm collection/regeneration for diploid populations by earlier workers can be directly deduced from our general expression by assigning appropriate values of the corresponding parameters. A seed factor which influences the plant sample size has also been isolated to aid the collectors in selecting the appropriate combination of number of plants and seeds per plant. When genotypic multiplicity of seeds is taken into consideration, a sample size of even less than 172 plants can conserve diversity of 20 alleles from 50,000 polymorphic loci with a very large probability of conservation (0.9999) in most of the cases.

Coronary stent implantation without lesion predilatation (direct stenting): our experience with this evolving technique.

BACKGROUND: Until recently, conventional intracoronary stent deployment required predilatation of the lesion with a balloon. However, "direct stenting" of the lesion without predilatation offers certain theoretical and practical advantages. We assessed the safety and feasibility of direct stenting in a select group of patients who were likely to benefit most from these advantages, namely, those with acute coronary syndromes. saphenous vein graft lesions, associated renal or left ventricular dysfunction and those requiring multivessel intervention. METHODS AND RESULTS: After direct stenting, intravascular ultrasound was used to assess the adequacy of stent expansion in 51 patients. One hundred and twenty patients with a total of 125 lesions (83.3% males, average age 54.6+/-12.4 years) were enrolled for direct stenting. Of these, 90% of patients had presented with acute coronary syndromes, 21.6% of patients had associated moderate-to-severe left ventricular systolic dysfunction, 6.7% of patients had associated renal dysfunction and 30.8% of patients required multivessel intervention. Angiographically visible thrombus was present in 35.2% of patients. The mean reference diameter of the lesion was 3.18+/-0.32 mm and mean percentage diameter stenosis was 76.4+/-11.2%. Almost all varieties of stents were used (8.8% bare and 91.2% mounted). Procedural success was achieved in 98.3% of patients (98.4% of lesions). In two cases, the lesion had to be predilated prior to stenting. On angiography, the need for postdilatation of the stent was apparent in 29 (23.6%) lesions. In contrast, on intravascular ultrasound evaluation done in 51 lesions after stent deployment, the need for postdilatation to optimize stent expansion was seen in 43 (84.3%) lesions. There was one instance of acute stent thrombosis and two instances of slow-flow phenomenon. There were no deaths, myocardial infarction or need for urgent bypass surgery. CONCLUSIONS: We conclude that direct stenting is feasible and safe in selected groups of patients. Optimization of stent expansion after direct stenting may often require aggressive postdilatation.

Coronary stent thrombosis: time course and clinical outcome.

The current clinical practice of stent implantation has changed over the last few years. We analysed the incidence and time course of stent thrombosis in patients undergoing successful coronary angioplasty and stenting over the last three years. All the patients were treated with aspirin and ticlopidine. A total of 13 patients experienced stent thrombosis. The mean age was 52+/-12 years; 12 were smokers and 10 had a recent history of myocardial infarction. None of these patients had received abciximab. The median time from stent implantation to stent thrombosis was 10 hours, with all the stent occlusions occurring within 18 hours of stent implantation procedure. All the patients underwent a repeat intervention at a median time of 30 minutes after the clinical suspicion of stent occlusion. On follow-up of 1 to 24 months, three patients developed reocclusion. In the present era of coronary angioplasty and stenting, when interventional procedures are not pre-planned and patients are treated with aspirin and ticlopidine or clopidogrel at the time of stent implantation, the incidence of stent thrombosis is low; it is seen mainly in patients with recent myocardial infarction, majority of them being smokers, and occurs within 18 hours in all the patients.

Elective stenting of extracranial carotid arteries.

OBJECTIVES: In symptomatic and asymptomatic patients with significant carotid artery stenosis, surgical endarterectomy has been shown to be beneficial when compared with medical management. Carotid stenting is evolving as an alternative technique for treating such patients. This prospective study was designed to assess the feasibility and safety of carotid angioplasty and stenting. METHODS: Fourteen patients (15 carotid arteries) with significant carotid artery stenosis were enrolled. These patients were in the age range 46 to 84 years (mean 60.9 +/- 7 years) and there were 12 males (86%). All of these patients were symptomatic with either TIA (n = 8) or stroke (n = 6). Wallstents were used in all the cases to stent the carotid arteries. One patient underwent bilateral carotid artery stenting. RESULTS: Carotid angioplasty and stenting was successful in 13 out of 14 (92.8%) patients and 14 out of 15 (93.3%) carotid arteries, with reduction in mean (+/- SD) stenosis from 86 +/- 6% to 3 +/- 3%. There was one episode of minor stroke, no major stroke or death during the initial hospitalization. Another patient had a minor stroke with patent ipsilateral carotid artery (on repeat angiography) during the first 30 days after the procedure. This patient was also found to have asymptomatic thrombus formation in the contralateral carotid stent which resolved with intravenous anticoagulation. During a mean follow up of 6 +/- 2 months there has been no recurrence of symptoms. CONCLUSIONS: Based upon our limited experience we believe that percutaneous carotid angioplasty with stenting is feasible with low periprocedural complication rate.

A general model for sample size determination for collecting germplasm.

The paper develops a general model for determining the minimum sample size for collecting germplasm for genetic conservation with an overall objective of retaining at least one copy of each allele with preassigned probability. It considers sampling from a large heterogeneous 2k-ploid population under a broad range of mating systems leading to a general formula applicable to a fairly large number of populations. It is found that the sample size decreases as ploidy levels increase, but increases with the increase in inbreeding. Under exclusive selfing the sample size is the same, irrespective of the ploidy level, when other parameters are held constant. Minimum sample sizes obtained for diploids by this general formula agree with those already reported by earlier workers. The model confirms the conservative characteristics of genetic variability of polysomic inheritance under chromosomal segregation.

Outcomes of primary stenting for acute myocardial infarction.

Primary coronary stenting is being increasingly used in patients undergoing primary coronary angioplasty for acute myocardial infarction. In this prospective study we analysed our experience of direct angioplasty in 76 patients with acute myocardial infarction of whom 65 received intracoronary stents using high pressure deployment (> or = 12 atm) with adjunctive aspirin and ticlopidine therapy but without coumadin. All patients underwent pre-discharge angiography. Stent implantation was successful in all patients. Stent thrombosis was not seen in any patient. However, TIMI grade 3 flow was obtained in only 58 (89.2%) patients with evidence of slow-flow present in the remaining seven patients. Pre-discharge angiograms showed no-stent thrombosis but five out of the seven (71%) patients with slow-flow phenomenon persisted to have slow-flow. These patients had lower left ventricular ejection fraction as compared to patients with TIMI 3 flow at pre-discharge angiography (27.5 +/- 10.2% vs 42.1 +/- 15.2%; p < 0.001) and a high mortality (2 out of 7) within 30 days. Primary stenting is safe and feasible in the majority of patients with good short-term outcome. But persistent slow-flow phenomenon with adverse clinical outcome is seen in a small but significant number of patients.

Acute haemodynamic effects of nicorandil in patients with chronic severe regurgitant valvular lesions.

The haemodynamic effects of nicorandil, a new balanced vasodilator exhibiting nitrate-like as well as potassium-channel opening activity in patients with chronic severe valvular lesions have not been reported. We studied the acute effect of nicorandil on haemodynamics in 12 stable patients (6 males, 6 females; mean age 23.5 +/- 4.6 years) with chronic severe valvular regurgitation (8 mitral, 4 aortic). All patients were studied in resting, supine and fasting states. All cardioactive drugs were withdrawn five days prior to the study. Intra-arterial line was placed and thermodilution catheter was positioned in the pulmonary artery. Haemodynamic parameters recorded at baseline and at 30, 60, 90 and 120 minutes following a single oral dose of 20 mg nicorandil revealed no significant change in the heart rate while systemic pressures showed a small decline (p < 0.05). There was significant reduction in systolic, diastolic and mean pulmonary artery pressures (p < 0.001). The mean cardiac index increased from 3.16 L/min/m2 at baseline to 3.77 L/min/m2 at 60 minutes. Both the pulmonary and systemic vascular resistance indices reduced significantly, the peak fall being 18 percent and 29 percent, respectively. Maximal changes were observed at 60 to 90 minutes following administration of nicorandil. No adverse effect of nicorandil occurred during the study. We conclude that nicorandil has a favourable acute haemodynamic effect in patients with chronic severe valve regurgitation. Its long-term use in valvular lesions should be explored further.