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A comparative evaluation of externally supported polytetrafluoroethylene axillobifemoral and axillounifemoral bypass grafts.

PURPOSE: We analyzed a current 78-month experience with externally supported (ringed) polytetrafluoroethylene (PTFE) axillobifemoral (AxBF) and axillounifemoral (AxUF) bypass grafts to address the controversy about whether the addition of a femorofemoral limb to an axillofemoral bypass graft improves the patency results. METHODS: Between January 1988 and June 1994, 36 AxBF and 22 AxUF externally supported PTFE ringed bypass grafts were performed at our institution. The age of the patients in the AxBF group was 67 +/- 11 years and 69 +/- 11 years in the AxUF group. The male/female ratio was 22:13 (AxBF) and 8:9 (AxUF). In 71% of cases (29/36 AxBF, 12/22 AxUF), the operations were performed for aortoiliac atherosclerotic occlusive disease in patients with significant medical risk factors or a "hostile" abdomen. The remaining 29% were patients requiring revascularization during treatment of an infected aortic graft. Bypass patency was assessed in the follow-up period by clinical evaluation, color-flow duplex imaging, or segmental limb pressure measurements. RESULTS: There was no significant difference in the 30-day operative mortality rate for all AxBF bypasses (11%) and all AxUF bypasses (6%) (p = 0.89 by chi-squared testing). The primary and secondary patency rates for the whole group of bypasses were 80% and 89% at 3 years, respectively (SE < 0.1). Between the AxBF and AxUF groups, there were no significant differences in either primary patency (80% for each group) or secondary patency (91% in AxBFs vs 85% in AxUFs) (SE < 0.1) at 2 years (Wilcoxon rank sum test). CONCLUSIONS: These data show no differences in the patency of externally supported PTFE AxBF and AxUF bypass grafts up to 2 years after implantation.

Aged↗

[Closure of an atrial septum defect using an umbrella prosthesis].

About three and a half years after direct suture of a secundum atrial septal defect (ASD) the now 72-year-old patient developed heart failure with pulmonary congestion and pleural effusion which responded to medical treatment. The electrocardiogram showed atrial fibrillation with an irregular ventricular rate and right bundle branch block. Right heart catheterization established recurrence of the ASD with a left to right shunt of 60% (Qp/Qs = 2.5) and a pulmonary artery pressure of 45/12 mmHg. Because of the clinical state, the risk of re-operation and the suitable anatomy, non-operative percutaneous transvenous catheter closure of the defect with a double-umbrella device was indicated. Following this procedure the cardiomegaly regressed, while colour-Doppler echocardiography demonstrated a minimal residual left to right shunt. The pulmonary artery pressure had fallen to 32/13 mmHg. Three months later the patient was without symptoms and resumed her usual activity. The ECG now showed sinus rhythm, and there was no evidence of a shunt. Anticoagulation with acetyl salicylic acid (100 mg daily) was continued for 3 months.

Aged↗

Five-year clinical and echocardiographic evaluation of the Das AngelWings atrial septal occluder.

BACKGROUND: The late outcome of patients treated with atrial septal occluder devices remains incompletely defined. The purpose of this study was to assess the late outcome (range 4-7 years postprocedure) of patients in whom the Das AngelWings septal occluder device was implanted in the atrial septum. We report the clinical and echocardiographic outcome, at an average of 5 years following the procedure, of patients treated with the Das AngelWings device used to close either a secundum atrial septal defect (ASD) or a patent foramen ovale (PFO). METHODS: Thirty-two patients underwent successful percutaneous closure of an atrial septal closure, patent foramen ovale, or fenestration in the lateral tunnel of their Fontan with the Das AngelWings device between June 1995 and March 1998 at Duke University Medical Center. Two of the 32 patients were lost to follow-up. The remaining 30 patients were divided into 3 groups based on indication for device implantation. Group 1 consisted of 14 patients with a secundum ASD and predominantly left-to-right atrial shunting. Group 2 consisted of 8 patients who had a PFO and who suffered a thromboembolic event. Group 3 (compassionate use) consisted of 10 patients with multiple comorbid medical problems with predominantly right-to-left shunting at the atrial level causing hypoxemia. Eight of the patients in group 3 were severely ill at the time of device implantation. The 2 remaining patients in group 3 underwent AngelWings implantation for closure of right-to-left shunting through a Fontan fenestration. Mean follow-up was 59 months. RESULTS: There was no device embolization. No patient in the ASD or PFO/stroke group had a clinical complication. By radiographic examination, 2 of 27 patients had evidence of fracture of the nitinol framework at 2-year follow-up. Residual shunting was present in 44% at 24 hours, 20% at 1 year, and 18.8% at 2 years by use of Doppler color flow imaging and/or microcavitation echocardiographic studies. Mild mitral regurgitation caused by the AngelWings device occurred in 1 patient. One patient in the compassionate use group had a subsequent neurologic event. Five of the 10 patients in the compassionate use group died of comorbid illnesses in follow-up, none directly related to device complications. CONCLUSION: The late clinical outcome of secundum ASD and PFO/stroke patients in this study demonstrates that Das AngelWings closure of the atrial septum is effective and safe. These data are encouraging with respect to the expanding use of other percutaneously implanted ASD occlusion devices, although late clinical safety and efficacy data are needed for the specific devices being implanted.

Adolescent↗

Contrast-enhanced duplex scanning of crural arteries by means of continuous infusion of Levovist.

OBJECTIVES: To estimate the dosage needed for continuous infusion and to investigate whether continuous infusion of the ultrasound contrast-enhancing agent Levovist (SH U 508A) can improve duplex scanning of crural arteries in patients with peripheral arterial obstructive disease (PAOD) eligible for distal bypass graft surgery. DESIGN, PATIENTS, AND METHODS: The study design consisted of two parts. Part 1 investigated the color and spectral Doppler scan enhancement of three different Levovist dosages (200, 300, and 400 mg/mL) in one arterial segment of a patent lumen of a crural artery in seven patients with PAOD. Part 2 investigated the value of the optimum Levovist dosage in the assessment of 10 crural arteries in 10 consecutive patients with PAOD. Angiography was the reference standard. RESULTS: Part 1: Levovist significantly enhanced color and spectral Doppler scan as compared with baseline ultrasound scan, but no differences were found between the Levovist dosages. Thus, the lowest Levovist dosage sufficed for application in part 2, because of its infusion volume and prolonged enhancement time. Part 2: The agreement between contrast-enhanced duplex scanning and angiography was moderate (kappa = 0.50; 95% confidence interval [CI], 0.03-0.97). Five (50%) of 10 crural arteries that could not adequately be visualized with routine duplex scanning could be visualized with contrast-enhanced duplex scanning. CONCLUSION: Contrast-enhanced duplex scanning by means of continuous infusion of Levovist in patients with PAOD improves the ultrasound scan investigation of crural arteries in case routine duplex scanning is inconclusive and might reduce the need for angiography.

Aged↗

Prevalence and need for replacement of amalgam and composite restorations in Dutch adults.

In 1986, the first nationwide epidemiological survey of adult oral health and attitudes to oral health care was carried out in The Netherlands. One of the aims of this study was to evaluate the prevalence and the quality (in terms of need for replacement) of amalgam and composite restorations in the Dutch adult population. A group of 600 dentate individuals, 20-44 years of age, was examined. Stratified cluster sampling included as factors age, gender, socio-economic status, and area of residence. Two additional parameters were studied: frequency of visiting a dentist and type of health insurance. Oral examinations consisted of direct (mirror and explorer) and indirect (color slides and bite-wing radiographs) observations with use of well-defined criteria. On average, 13.4 restorations per individual were present, of which 23.3% were classified as unsatisfactory. A great difference in prevalence and quality data was found among several types of restorations. Test results (ANOVA) for effects of age, gender, socio-economic status, area of residence, frequency of visiting a dentist, and insurance on the prevalence of (un)satisfactory restorations resulted nearly always in significant effects of only age and frequency of visits to a dentist. There was a tendency (p less than 0.05) for the prevalence of (un)satisfactory restorations to be higher with increasing age.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Evaluation of Björk-Shiley prosthetic valves by real-time two-dimensional Doppler echocardiographic flow mapping.

We studied the value of two-dimensional Doppler echocardiographic color flow mapping for identifying normal transvalve flow profiles and valve malfunction in 20 patients with Björk-Shiley prosthetic valves. Seven patients had Björk-Shiley prosthetic valves in the aortic position alone, seven in the mitral position, and six had prosthetic valves in both the aortic and mitral positions. In 10 patients with normally functioning mitral valves, the ratios of the maximal major and minor Doppler-imaged orifice flow diameters to the valve ring diameters were 25 +/- 3% (mean +/- SD) and 24 +/- 3%, respectively, similar to values reported in in vitro studies. No mitral regurgitation was found in these patients by two-dimensional Doppler echocardiographic flow mapping or by spectral Doppler. Of the 10 clinically normal aortic Björk-Shiley valves, no valvular regurgitation was found by color flow mapping, whereas mild aortic regurgitation was found in two patients with the use of spectral Doppler. Malfunction of six valves was documented in five patients and was confirmed by cardiac catheterization and/or surgery. These included one case of focal fibrous ingrowth involving primarily the minor orifice of a mitral prosthetic valve, one case of mitral valve prosthetic thrombosis with decreased major and minor orifice flow diameters and valvular regurgitation, and four cases of paravalvular regurgitation involving prosthetic valves in the aortic position (three patients) and the mitral position (one patient). Two-dimensional Doppler echocardiographic flow mapping provides new observations that may aid in identifying Björk-Shiley prosthetic valve malfunction. By localizing precisely the site of prosthetic stenosis or regurgitation, it may also assist in defining the cause of valve malfunction.

Adolescent↗

Aortic root replacement with the freestyle stentless porcine aortic root bioprosthesis.

BACKGROUND: Stentless porcine prosthetic valves offer several advantages over traditional valves. Among these are superior hemodynamics, laminar flow patterns, lack of need for anticoagulation and perhaps improved durability. METHODS: One hundred and twelve patients were operated on from September 17, 1992 to April 13, 1998 as part of a multi-center worldwide investigation. All patients received a total aortic root replacement. Patients were evaluated postoperatively at discharge, 3 to 6 months, and yearly by clinical exam and color flow Doppler echocardiography. RESULTS: There were 4 deaths either in the hospital or within 30 days after surgery for an operative mortality of 3.6%. No patients experienced structural valve deterioration, non-structural valve deterioration, paravalvular leak, unacceptable hemodynamic performance, or postoperative endocarditis. The linearized rates for survival and thromboembolic complications at 5 years were 82.8% and 90.5% respectively. Excellent hemodynamic function is demonstrated by very low gradients, large EOA, and an exceedingly low incidence of any aortic regurgitation. CONCLUSIONS: The Medtronic Freestyle aortic root bioprosthesis can be used safely to replace the aortic root for aortic valve and aortic root pathology. Root replacement allows optimal hemodynamic performance with no significant aortic regurgitation. Early and intermediate results are encouraging, but further follow-up is needed to determine valve durability.

Adult↗

Carotid endarterectomy with bovine pericardium patch angioplasty: mid-term results.

The objective of this study was to assess the efficacy of bovine pericardium (BP) as a patch material in carotid endarterectomy (CEA) in terms of peri- and postoperative complications and the incidence of recurrent stenosis. During a 4-year period, 148 CEAs were performed in 138 consecutive patients. The study group included elective, emergency, and combined with cardiac operation CEAs in both symptomatic and asymptomatic carotid artery disease patients. Patch angioplasty using the BP followed the standard CEA in all patients. Postoperative follow-up included clinical examination and periodical color duplex scans at 3, 6, and 12 months and yearly thereafter. Surgical outcome was evaluated by the operation-related parameters, early and late mortality and morbidity rates, and the incidence of recurrent stenosis. All CEAs were performed without any unfavorable event. In the early postoperative period, there were no deaths and the morbidity consisted of transient cranial nerve paresis (4.7%) in seven patients and two ipsilateral strokes (1.4%). During the follow-up period, three patients (2%) developed significant carotid restenosis, though they remain asymptomatic, while there were no deaths related to the CEA. Patch angioplasty of the carotid artery using BP showed unwittingly early and mid-term surgical outcome. Our results demonstrate the BP to be a suitable patch material for routine use in carotid surgery.

Adult↗

[Comparative, clinical and echocardiographic study of the Bex and De Vega annuloplasties].

A retrospective study of 27 cases compared the long term clinical and echocardiographic results of tricuspid valve annuloplasty by the Bex (15 patients) and the De Vega (12 patients) techniques. All patients were in NYHA Classes III or IV before surgery. There was associated mitral valve disease in 24 cases and mixed mitral and aortic valve disease in 3 patients requiring valve replacement. The follow-up period ranged from 3 to 106 months (average 48 +/- 4 months). All patients underwent clinical and color Doppler echocardiographic evaluation. There was symptomatic improvement after surgery as all patients recovered to NYHA Classes I or II. An echocardiographic classification was adopted to assess residual tricuspid regurgitation. The leak was judged to be significant when the surface area of the jet was greater than 5 cm2. Two thirds of patients (17/27) had no significant residual tricuspid regurgitation with the Bex or de Vega techniques of tricuspid annuloplasty according to this criterion. However, significant residual tricuspid regurgitation was observed in 37% of patients (10/27) even though they were all clinically improved. A comparison of the echocardiographic parameters including the severity of residual tricuspid regurgitation, the left and right atrial dimensions, the right ventricular dimensions and tricuspid valve pressure gradients did not show any significant long term difference between the Bex and the De Vega tricuspid annuloplasties.

Echocardiography, Doppler↗

Effect of polymethylmethacrylate particles on mature bone in the optical bone chamber.

Reaction of mature bone and its vasculature to 3.33 +/- 0.19 microm polymethylmethacrylate (PMMA) particles at a concentration of 2.5 x 10(8)/cc was measured using optical bone chamber implant intravital microscopy. Twelve adult female New Zealand White rabbits were divided into six receiving Healon alone (controls) and six receiving Healon plus PMMA. The particles were introduced to the bone chamber compartment after removing its overlying optical element, which was immediately reinstalled. Reaction was monitored weekly over a 6-week period using video and photographic imaging. Bone was labeled before treatment with oxytetracycline and after treatment with alizarin complexone. Perfusing blood was labeled with fluorescein isothiocyanate dextran-70 kDa (FITC-D70). Parameters measured were net bone resorption, from black and white images, bone turnover, from color images, vascularity, and average vessel caliber. Neither bone turnover nor vessel caliber were significantly affected at the p < or = 0.050 level over time. In contrast, bone resorption was significantly greater and vascularity significantly less in the presence of PMMA. It was inferred that any differences in bone turnover were masked by resorption of new bone. It was concluded that the lack of a PMMA effect on average vessel caliber meant that the vascularity effects were not due to angiogenesis, but to vessel recruitment (or its opposite), an effect more consistent with inflammation than repair. The lack of vascularity increase in PMMA-treated compartments also suggested that increased resorption was a local phenomenon, because blood supply had not increased to provide the extra osteoclasts required for observed net bone loss.

Animals↗

Duplex and color Doppler sonography of hemodialysis arteriovenous fistulas and grafts.

Surgically constructed Brescia-Cimino arteriovenous fistulas and synthetic loop grafts are common means of vascular access for hemodialysis. Although angiography has been the traditional method of imaging these vascular systems, duplex and color Doppler sonography offer a noninvasive method of evaluating dysfunctional hemodialysis access. In normally functioning fistulas, waveforms of flow in the supply arteries and throughout the graft are monophasic, with peak systolic velocities of 100-400 cm/sec and end-diastolic velocities of 60-200 cm/sec. The draining veins have arterial pulsations with peak velocities of 30-100 cm/sec. Arterial and venous stenoses, graft thrombosis (occlusive and nonocclusive), infection, aneurysm and pseudoaneurysm formation, and arterial steal are relatively common abnormalities that can threaten or destroy graft function and can be diagnosed sonographically. Although abnormal hemodynamics in access fistulas are usually detected during hemodialysis, sonographic evaluation at the time of initial dysfunction may reveal an underlying correctable abnormality, and specific therapy may be instituted before the condition progresses. In addition, use of sonography may obviate an invasive angiographic examination if no significant hemodynamic problem is present.

Arteriovenous Shunt, Surgical↗

Transesophageal echocardiographic recognition of subaortic complications in aortic valve endocarditis. Clinical and surgical implications.

BACKGROUND: Secondary involvement of the mitral-aortic intervalvular fibrosa and the anterior mitral leaflet (subaortic structures) can occur in patients with aortic valve endocarditis. The secondary involvement of these structures occurs as a result of direct extension of the infection from the aortic valve or as a result of an infected aortic regurgitant jet striking the ventricular surfaces of the mitral-aortic intervalvular fibrosa and the anterior mitral leaflet. The abscess of mitral-aortic intervalvular fibrosa can expand to form an aneurysm. Subsequently, this mitral-aortic intervalvular fibrosa aneurysm can develop a perforation and communicate with the left atrium, resulting in the systolic regurgitation of blood from the left ventricular outflow tract into the left atrium. Secondary infection can also occur on the ventricular surface of the anterior mitral leaflet and result in the formation of an aneurysm or perforation of anterior mitral leaflet. METHODS AND RESULTS: This study examines the utility of transesophageal echocardiography in the detection of these subaortic complications in 55 consecutive patients with aortic valve endocarditis. A total of 24 patients (44%) had involvement of subaortic structures, including four with an abscess in the mitral-aortic intervalvular fibrosa, four with mitral-aortic intervalvular fibrosa aneurysm, seven with perforation of the mitral-aortic intervalvular fibrosa with communication into the left atrium, two with an aneurysm of the anterior mitral leaflet, and seven with perforation of the anterior mitral leaflet. The transesophageal echocardiographic findings were confirmed at surgery in 20 patients and at necropsy in two. By comparison, transthoracic echocardiography visualized these lesions in five of 24 patients (21%), including none of four with mitral-aortic intervalvular fibrosa abscesses, two of four with mitral-aortic intervalvular fibrosa aneurysms, one of seven with mitral-aortic intervalvular fibrosa perforations, one of two with anterior mitral leaflet aneurysms, and one of seven anterior mitral leaflet perforations. Eccentric mitral regurgitation-type systolic jets were noted in eight additional patients by transthoracic color flow imaging, and this finding suggested the possibility of these unusual subaortic complications. If these patients are included, then transthoracic echocardiography suggested the presence of these subaortic complications in 13 of 24 patients (54%). CONCLUSIONS: The results indicate that 1) involvement of the subaortic structures in patients with aortic valve endocarditis may be more common than previously recognized, 2) patients with aortic valve endocarditis and eccentric jets of mitral regurgitation on transthoracic echocardiography should undergo further evaluation by transesophageal echocardiography to exclude these unusual complications, 3) precise recognition of these complications is of value in the optimal medical and surgical management of these patients, and 4) these complications may be responsible for unexplained congestive heart failure and hemodynamic deterioration in some patients with aortic valve endocarditis.

Abscess↗

Endovascular stent-graft treatment of traumatic arterial lesions.

Twenty-nine cases of post-traumatic false aneurysms and arteriovenous fistulas (AVF), with a mean follow-up of 24 months (1-65 months), are presented here. Diagnosis was established by color duplex and arteriogram. The time between injury and treatment varied between 3 days and 61 months. Endovascular treatment was accomplished using a covered Palmaz stent [vein, polytetrafluoroethylene (PTFE), or polyester], Corvita endoluminal graft, or a Wallgraft. Complimentary treatment of a branch injury was performed using a detachable balloon in one patient. The initial result was favorable for all patients. One case of asymptomatic stenosis of an iliac stent graft and three occlusions of the stent (one subclavian, one axillary, and one internal carotid) were registered during the follow-up period, and no clinical manifestations of the occlusions were reported. Endovascular treatment of post-traumatic false aneurysms and AVF appears to be a promising alternative for treatment of these lesions. Less pain and disability as well as rapid recovery time and lower cost after endovascular treatment compare favorably to the standard surgical technique.

Adult↗

Natural history of early aortic paraprosthetic regurgitation: a five-year follow-up.

OBJECTIVES: To assess the incidence and natural course of paravalvular leaks detected early after aortic valve replacement. BACKGROUND: Although the use of echocardiography has simplified the postoperative assessment of patients with aortic valve replacement, there are no data regarding the natural history of early detected paravalvular aortic leaks. METHODS: Eighty-four consecutive patients with aortic valve replacement were prospectively followed clinically every 6 months and by echocardiography early (11 +/- 7 days), at midterm (27 +/- 3 months), and late (63 +/- 4 months) after aortic valve replacement. The competence of artificial valves was assessed by Doppler color flow mapping. RESULTS: Paraprosthetic leaks were detected in 40 (47.6%) aortic prostheses during the early study; the majority (90%) were small. All leaks remained unchanged during the follow-up period. Left ventricular dimensions and function did not differ between patients with or without paravalvular leak during the follow-up. Left ventricular fractional shortening, however, increased during the intermediate study in both subgroups, indicating improved left ventricular function overall. Three patients had severe paravalvular regurgitation suddenly develop from late infective endocarditis, and 1 patient had a degenerative tissue valve failure 4 years after implantation. CONCLUSIONS: Paraprosthetic aortic leaks detected early after surgery, in the absence of valve infection, are common, are usually small, and have a benign course. However, the development of new, usually severe, regurgitation should raise the suspicion of prosthetic valve endocarditis or bioprosthetic valve failure.

Adult↗

Differential effects on portal and effective hepatic blood flow. A comparison between transjugular intrahepatic portasystemic shunt and small-diameter H-graft portacaval shunt.

OBJECTIVE: This study was undertaken to determine the effects of transjugular intrahepatic portasystemic shunt (TIPS) and small-diameter prosthetic H-graft portacaval shunt (HGPCS) on portal and effective hepatic blood flow. SUMMARY BACKGROUND DATA: Mortality after TIPS is higher than after HGPCS for bleeding varices. This higher mortality is because of hepatic failure, possibly a result of excessive diminution of hepatic blood flow. METHODS: Forty patients randomized prospectively to undergo TIPS or HGPCS had effective hepatic blood flow determined 1 day preshunt and 5 days postshunt using low-dose galactose clearance. Portal blood flow was determined using color-flow Doppler ultrasound. RESULTS: Treatment groups were similar in age, gender, and Child's class. Each procedure significantly reduced portal pressures and portasystemic pressure gradients. Portal flow after TIPS increased (21 mL/second +/- 11.9 to 31 mL/second +/- 16.9, p < 0.05), whereas it remained unchanged after HGPCS (26 mL/second +/- 27.7 to 14 mL/second +/- 41.1, p = n.s.). Effective hepatic blood flow was diminished significantly after TIPS (1684 mL/minute +/- 2161 to 676 mL/minute +/- 451, p < 0.05) and was unaffected by HGPCS (1901 mL/ minute +/- 1818 to 1662 mL/minute +/- 1035, p = n.s.). CONCLUSIONS: Both TIPS and HGPCS achieved significant reductions in portal vein pressure gradients. Portal flow increased after TIPS, although most portal flow was diverted through the shunt. Effective hepatic flow is reduced significantly after TIPS but well preserved after HGPCS. Hepatic decompensation and mortality after TIPS may be because, at least in part, of reductions in nutrient hepatic flow.

Aged↗

Transvasal closure of interatrial defects using the Babic double-umbrella occluder system.

The purpose of the study was to assess the feasibility and safety of closure of atrial septal defects and patent foramen ovale by means of a new interventional technique. Transvasal closure of ostium secundum atrial septal defect and patent foramen ovale was performed in 18 patients using an occluder system for atrial septal defects. Two patients had undergone unsuccessful direct surgical closure years before. Implantation and follow-up were controlled using radiographic views both with and without contrast injection, transthoracic and multiplane transesophageal echocardiographic imaging, color Doppler sonography, and computed tomography. The defect was closed in 16 patients using 19 procedures. Removal of the devices through the sheath was indicated in 4 patients because of placement failure. Intraprocedural complications were ventricular fibrillation in one patient and fixation of the device in Chiari's network in an additional one. During 7-26 months follow-up occluder damage was seen in two patients and perforation of the left atrium in one patient. Thickening on the occluder surface was observed in two patients. There was no death. The system for closure of atrial septal defect is feasible and safe in patients with defects < or = 27 mm in diameter. Long-term observation of outcome is limited yet.

Adult↗

Microleakage at the abutment-implant interface of osseointegrated implants: a comparative study.

Microleakage can occur at the abutment-implant (A-I) interface in osseointegrated implants and may cause malodor and inflammation of peri-implant tissues. The degree of microleakage at the A-I interface of 5 implant systems was comparatively assessed at varying closing torques. Using colored tracing probes driven by a 2-atm pressure system, the interface microleakage of Brånemark, Sulzer Calcitek, 3i, ITI, and Steri-Oss implants was determined spectrophotometrically. Microleakage through the A-I interface occurred in all systems, with variability between systems, samples, and closing torques. As closing torque increased from 10 Ncm to 20 Ncm to manufacturers' recommended closing torques, microleakage decreased significantly (P < .005) for all systems. Analysis of variance showed significant interaction between closing torques and the time course of microleakage, and between systems and the time course of microleakage (P < .001). The results indicate that fluids and small molecules are capable of passing through the interface of all the A-I assemblies studied. Presumably in an in situ situation, fluids containing bacterial byproducts and nutrients required for bacterial growth may pass through the interface gap, contributing in part to clinically observed malodor and peri-implantitis.

Analysis of Variance↗

The effect of small-diameter H-graft portacaval shunts on portal blood flow.

BACKGROUND: Small-diameter prosthetic H-graft portacaval shunts have been shown to promote preservation of total hepatic blood flow relative to large-diameter H-graft shunts. Nonetheless, specific changes in portal hemodynamics occurring with small-diameter H-graft shunting are unknown. This study was undertaken to evaluate changes in portal flow that occur with these shunts. METHODS: Portal vein and inferior vena cava (IVC) blood flow were determined intraoperatively in 36 consecutive adults before and after prosthetic H-graft portacaval shunting using color-flow Doppler ultrasound. Postshunt measurements were made immediately cephalad and caudad to the shunt. Comparisons were undertaken using a paired Student's t-test with 95% confidence. RESULTS: Portal pressures decreased in all (P < 0.001), but never to normal. Postshunt portal flow cephalad and caudad to the shunt were not different from preshunt flow (P = 0.09, P = 0.28, respectively), although they were different from each other (P = 0.004). Postshunt IVC flow cephalad to the shunt was greater than caudad IVC flow (P = 0.004) and greater than preshunt IVC flow (P < 0.001), reflecting high flow through the shunt into the IVC. CONCLUSIONS: Small-diameter prosthetic H-graft portacaval shunts divert a significant amount of blood from the portal vein and significantly decrease portal pressures. The decreases in portal pressures with shunting are significant whereas changes in portal blood flow into the liver are not. These findings help explain the low incidence of variceal rebleeding and hepatic dysfunction after these shunts.

Blood Vessel Prosthesis↗