Cement distribution, volume, and compliance in vertebroplasty: some answers from an anatomy-based nonlinear finite element study

STUDY DESIGN: The biomechanics of vertebral bodies augmented with real distributions of cement were investigated using nonlinear finite element (FE) analysis. OBJECTIVES: To compare stiffness, strength, and stress transfer of augmented versus nonaugmented osteoporotic vertebral bodies under compressive loading. Specifically, to examine how cement distribution, volume, and compliance affect these biomechanical variables. SUMMARY OF BACKGROUND DATA: Previous FE studies suggested that vertebroplasty might alter vertebral stress transfer, leading to adjacent vertebral failure. However, no FE study so far accounted for real cement distributions and bone damage accumulation. METHODS: Twelve vertebral bodies scanned with high-resolution pQCT and tested in compression were augmented with various volumes of cements and scanned again. Nonaugmented and augmented pQCT datasets were converted to FE models, with bone properties modeled with an elastic, plastic and damage constitutive law that was previously calibrated for the nonaugmented models. The cement-bone composite was modeled with a rule of mixture. The nonaugmented and augmented FE models were subjected to compression and their stiffness, strength, and stress map calculated for different cement compliances. RESULTS: Cement distribution dominated the stiffening and strengthening effects of augmentation. Models with cement connecting either the superior or inferior endplate (S/I fillings) were only up to 2 times stiffer than the nonaugmented models with minimal strengthening, whereas those with cement connecting both endplates (S + I fillings) were 1 to 8 times stiffer and 1 to 12 times stronger. Stress increases above and below the cement, which was higher for the S + I cases and was significantly reduced by increasing cement compliance. CONCLUSION: The developed FE approach, which accounts for real cement distributions and bone damage accumulation, provides a refined insight into the mechanics of augmented vertebral bodies. In particular, augmentation with compliant cement bridging both endplates would reduce stress transfer while providing sufficient strengthening.

Vertebroplasty: experimental characterization of polymethylmethacrylate bone cement spreading as a function of viscosity, bone porosity, and flow rate

STUDY DESIGN: This is an experimental study on an artificial vertebra model and human cadaveric spine. OBJECTIVE: Characterization of polymethylmethacrylate (PMMA) bone cement distribution in the vertebral body as a function of cement viscosity, bone porosity, and injection speed. Identification of relevant parameters for improved cement flow predictability and leak prevention in vertebroplasty. SUMMARY OF BACKGROUND DATA: Vertebroplasty is an efficient procedure to treat vertebral fractures and stabilize osteoporotic bone in the spine. Severe complications result from bone cement leakage into the spinal canal or the vascular system. Cement viscosity has been identified as an important parameter for leak prevention but the influence of bone structure and injection speed remain obscure. METHODS: An artificial vertebra model based on open porous aluminum foam was used to simulate bone of known porosity. Fifty-six vertebroplasties with 4 different starting viscosity levels and 2 different injection speeds were performed on artificial vertebrae of 3 different porosities. A validation on a human cadaveric spine was executed. The experiments were radiographically monitored and the shape of the cement clouds quantitatively described with the 2 indicators circularity and mean cement spreading distance. RESULTS: An increase in circularity and a decrease in mean cement spreading distance was observed with increasing viscosity, with the most striking change occurring between 50 and 100 Pas. Larger pores resulted in significantly reduced circularity and increased mean cement spreading distance whereas the effect of injection speed on the 2 indicators was not significant. CONCLUSION: Viscosity is the key factor for reducing the risk of PMMA cement leakage and it should be adapted to the degree of osteoporosis encountered in each patient. It may be advisable to opt for a higher starting viscosity but to inject the material at a faster rate.

Percutaneous transluminal angioplasty and stent placement in acute vessel occlusion: evaluation of new methods for interventional stroke treatment

BACKGROUND AND PURPOSE: The major goal of acute ischemic stroke treatment is fast and sufficient recanalization. Percutaneous transluminal balloon angioplasty (PTA) and/or placement of a stent might achieve both by compressing the thrombus at the occlusion site. This study assesses the feasibility, recanalization rate, and complications of the 2 techniques in an animal model. MATERIALS AND METHODS: Thirty cranial vessels of 7 swine were occluded by injection of radiopaque thrombi. Fifteen vessel occlusions were treated by PTA alone and 15, by placement of a stent and postdilation. Recanalization was documented immediately after treatment and after 1, 2, and 3 hours. Thromboembolic events and dissections were documented. RESULTS: PTA was significantly faster to perform (mean, 16.6 minutes versus 33.0 minutes for stent placement; P < .001), but the mean recanalization rate after 1 hour was significantly better after stent placement compared with PTA alone (67.5% versus 14.6%, P < .001). Due to the self-expanding force of the stent, vessel diameter further increased with time, whereas the recanalization result after PTA was prone to reocclusion. Besides thromboembolic events related to the passing maneuvers at the occlusion site, no thrombus fragmentation and embolization occurred during balloon inflation or stent deployment. Flow to side branches could also be restored at the occlusion site because it was possible to direct thrombus compression. CONCLUSIONS: Stent placement and postdilation proved to be much more efficient in terms of acute and short-term vessel recanalization compared with PTA alone.

Survival and cardiac remodeling benefits in patients undergoing late percutaneous coronary intervention of the infarct-related artery: evidence from a meta-analysis of randomized controlled trials

Our purpose was to perform a systematic review and meta-analysis of randomized trials comparing percutaneous coronary intervention (PCI) of the infarct-related artery (IRA) with medical therapy in patients randomized >12 h after acute myocardial infarction (AMI).

Endothelin-1 and acute myocardial infarction: a no-reflow mediator after successful percutaneous myocardial revascularization

AIMS: No-reflow after a primary percutaneous coronary intervention (PCI) is associated with a high incidence of left ventricular (LV) failure and a poor prognosis. Endothelin-1 (ET-1) is a potent endothelium-derived vasoconstrictor peptide and an important modulator of neutrophil function. Elevated systemic ET-1 levels have recently been reported to predict a poor prognosis in patients with acute myocardial infarction (AMI) treated by primary PCI. We aimed to investigate the relationship between systemic ET-1 plasma levels and no-reflow in a group of AMI patients treated by primary PCI. METHODS AND RESULTS: A group of 51 patients (age 59+/-9.9 years, 44 males) with a first AMI, undergoing successful primary or rescue PCI, were included in the study. Angiographic no-reflow was defined as coronary TIMI flow grade < or =2 or TIMI flow 3 with a final myocardial blush grade < or =2. Blood samples were obtained from all patients on admission for ET-1 levels measurement. No reflow was observed in 31 patients (61%). Variables associated with no-reflow at univariate analysis included culprit lesion of the left anterior coronary descending artery (LAD) (67 vs. 29%, P=0.006) and ET-1 plasma levels (3.95+/-0.7 vs. 3.3+/-0.8 pg/mL, P=0.004). At multivariable logistic regression analysis, ET-1 was the only significant predictor of no-reflow (P=0.03) together with LAD as the culprit vessel (P=0.04). CONCLUSION: ET-1 plasma levels predict angiographic no-reflow after successful primary or rescue PCI. These findings suggest that ET-1 antagonists might be beneficial in the management of no-reflow.

Percutaneous PFO closure with Amplatzer PFO occluder: predictors of residual shunts at 6 months follow-up

OBJECTIVE: The objective of this study was to assess predictors of residual shunts after percutaneous patent foramen ovale (PFO) closure with Amplatzer PFO occluder (AGA Medical Corporation, Golden Valley, MN, USA). METHODS: All percutaneous PFO closures, using Amplatzer PFO occluder performed at a tertiary center between May 2002 and August 2006, were reviewed. Follow-up, including saline contrast transesophageal echocardiography, was performed in all patients 6 months after the intervention. PATIENTS: A total of 135 procedures were performed. Mean age of the patients was 51 years. The indication for PFO closure was an ischemic cerebrovascular event in 92%, paradoxical systemic embolism in 4%, and a diving accident in 4%. Recurrent events prior to PFO closure were noted in 34%. A concomitant atrial septal aneurysm was present in 61%. RESULTS: At 6 months follow-up, a residual shunt was detected in 26 patients (19%). Residual shunts were more common in patients with an atrial septal aneurysm (27 vs. 8%, P= .01) and in patients treated with a 35-mm compared with a 25-mm device (39 vs. 15%, P= .01). A concomitant atrial septal aneurysm remained independently associated with residual shunts when controlled for body mass index, gender, age, atrial dimensions, and presence of a Chiari network (odds ratio 4.1, 95% confidence intervals 1.1-15.0). CONCLUSION: The presence of atrial septal aneurysms in patients undergoing percutaneous PFO closure with an Amplatzer PFO occluder significantly increases the rate of residual shunts at 6 months follow-up, even if 35-mm devices are used.

Late results after percutaneous closure of patent foramen ovale for secondary prevention of paradoxical embolism using the amplatzer PFO occluder without intraprocedural echocardiography: effect of device size

OBJECTIVES: We sought to assess the safety and clinical efficacy of patent foramen ovale (PFO) closure under fluoroscopic guidance only, without intraprocedural echocardiography. BACKGROUND: Percutaneous PFO closure has been shown to be safe and feasible using several devices. It is generally performed using simultaneously fluoroscopic and transesophageal or intracardiac echocardiographic guidance. Transesophageal echocardiography requires sedation or general anesthesia and intubation to avoid aspiration. Intracardiac echocardiography is costly and has inherent risks. Both lengthen the procedure. The Amplatzer PFO Occluder (AGA Medical Corporation, Golden Valley, Minnesota) can be safely implanted without echocardiographic guidance. METHODS: A total of 620 patients (51 +/- 12 years; 66% male) underwent PFO closure using the Amplatzer PFO Occluder for secondary prevention of presumed paradoxical embolism. Based on size and mobility of the PFO and the interatrial septum, an 18-mm device was used in 50 patients, a 25-mm device in 492, and a 35-mm device in 78. RESULTS: All procedures were successful, with 5 procedural complications (0.8%): 4 arteriovenous fistulae requiring elective surgical correction, and 1 transient ischemic attack. Contrast transesophageal echocardiography at 6 months showed complete closure in 91% of patients, whereas a minimal, moderate, or large residual shunt persisted in 6%, 2%, and 1%, respectively. During a mean follow-up period of 3.0 +/- 1.9 years (median: 2.6 years; total patient-years: 1,871), 5 ischemic strokes, 8 transient ischemic attacks, and no peripheral emboli were reported. Freedom from recurrent ischemic stroke, transient ischemic attack, or peripheral embolism was 99% at 1 year, 99% at 2 years, and 97% at 5 years. CONCLUSIONS: The Amplatzer PFO Occluder affords excellent safety and long-term clinical efficacy of percutaneous PFO closure without intraprocedural echocardiography.

Percutaneous closure of a postinfarction ventricular septal defect and an iatrogenic left ventricular free-wall perforation using two Amplatzer muscular VSD occluders

A 83-year-old woman underwent percutaneous closure of postinfarction ventricular septal defect following anteroseptal myocardial infarction and percutaneous coronary intervention with stent implantation of the left anterior descending coronary artery. Postinfarction percutaneous ventricular septal defect closure was initially complicated by an iatrogenic left ventricular free-wall perforation. Both defects were closed using two Amplatzer muscular VSD occluders during the same session.

Successful percutaneous coronary intervention after implantation of a CoreValve percutaneous aortic valve

BACKGROUND: The association between aortic valve disease and coronary atherosclerosis is common. In the recent era of percutaneous aortic valve replacement (PAVR), there is little experience with coronary artery intervention after valve implantation. CASE REPORT: To our knowledge, this is the first case of successful percutaneous coronary intervention after implantation of a CoreValve percutaneous aortic valve. We report a case of a 79-year-old female patient who underwent successful coronary artery intervention few months after a CoreValve's percutaneous implantation for severe aortic valve stenosis. Verifying the position of the used wires (crossing from inside the self expanding frame) is of utmost importance before proceeding to coronary intervention. In this case, crossing the aortic valve, coronary angiography, and multivessel stenting were successfully performed. CONCLUSION: Percutaneous coronary intervention in patients with previous CoreValve is feasible and safe.

Percutaneous coronary revascularization in patients with formerly "refractory angina pectoris in end-stage coronary artery disease" - not "end-stage" after all

BACKGROUND: Patients with refractory angina pectoris in end-stage coronary artery disease represent a severe condition with a higher reduction of life-expectancy and quality of life as compared to patients with stable coronary artery disease. It was the purpose of this study to invasively re-evaluate highly symptomatic patients with formerly diagnosed refractory angina pectoris in end-stage coronary artery disease for feasible options of myocardial revascularization. METHODS: Thirty-four patients formerly characterized as having end stage coronary artery disease with refractory angina pectoris were retrospectively followed for coronary interventions. RESULTS: Of those 34 patients 21 (61.8%) were eventually revascularized with percutaneous interventional revascularization (PCI). Due to complex coronary morphology (angulation, chronic total occlusion) PCI demanded an above-average amount of time (66 +/- 42 minutes, range 25-206 minutes) and materials (contrast media 247 +/- 209 ml, range 50-750 ml; PCI guiding wires 2.0 +/- 1.4, range 1-6 wires). Of PCI patients 7 (33.3%) showed a new lesion as a sign of progression of atherosclerosis. Clinical success rate with a reduction to angina class II or lower was 71.4% at 30 days. Surgery was performed in a total of8 (23.5%) patients with a clinical success rate of 62.5%. Based on an intention-to-treat 2 patients of originally 8 (25%) demonstrated clinical success. Mortality during follow-up (1-18 months) was 4.8% in patients who underwent PCI, 25% in patients treated surgically and 25% in those only treated medically. CONCLUSION: The majority of patients with end-stage coronary artery disease can be treated effectively with conventional invasive treatment modalities. Therefore even though it is challenging and demanding PCI should be considered as a first choice before experimental interventions are considered.

Surgical versus percutaneous revascularization of coronary artery disease in diabetic patients

Morbidity and mortality related to coronary artery disease (CAD) remain a great challenge in patients with diabetes mellitus. Revascularization of CAD is an important therapeutic intervention owing to its impact on both symptoms and prognosis. The optimal revascularization strategy continues to evolve due to the advent of new technologies and improved peri-procedural outcome with both percutaneous coronary interventions and coronary artery bypass grafting. Although clinical outcome following coronary artery bypass is worse in diabetic as opposed to non-diabetic patients, surgical revascularization tends to be associated with better outcome in stable patients with multivessel disease and reduced left ventricular function. The advent of drug-eluting stents has challenged the supremacy of coronary artery bypass grafting and has become a valuable alternative to surgery. The safety and efficacy of drug-eluting stents in the treatment of patients with diabetes and multivessel disease is currently under investigation in several ongoing randomized controlled trials. Percutaneous coronary intervention is the therapy of choice in patients with acute coronary syndromes, particularly ST-elevation myocardial infarction. The focus of this review is to present the current evidence, define the role of percutaneous and surgical revascularization in the treatment of diabetic patients with CAD, and propose a tailored approach for clinical decision-making.

Percutaneous left ventricular assist devices during cardiogenic shock and high-risk percutaneous coronary interventions

Left ventricular assist devices were developed to support the function of a failing left ventricle. Owing to recent technological improvements, ventricular assist devices can be placed by percutaneous implantation techniques, which offer the advantage of fast implantation in the setting of acute left ventricular failure. This article reviews the growing evidence supporting the clinical use of left ventricular assist devices. Specifically, we discuss the use of left ventricular assist devices in patients with cardiogenic shock, in patients with acute ST-elevation myocardial infarction without shock, and during high-risk percutaneous coronary interventions.