Preserved Valve Function Research Articles

Global longitudinal strain is a surrogate marker for time constant of isovolumic relaxation in post-Fontan operation patients with single right ventricle and preserved ejection fraction.

The time constant of isovolumic relaxation is an established index of ventricular relaxation, a major component of diastolic function, even in a single right ventricle. However, the specific echocardiographic parameters for estimating diastolic dysfunction are insufficient for a single right ventricle. This study aimed to investigate the echocardiographic indices associated with time constant of isovolumic relaxation in post-Fontan operation patients with a single right ventricle. We included 39 patients with hypoplastic left heart syndrome after Fontan operation with an ejection fraction ≥45% and preserved valve function. First, the correlation between echocardiographic parameters and time constant of isovolumic relaxation was examined, and partial correlation coefficients were calculated using age and heart rate as covariates. Next, univariate regression analysis was performed using time constant of isovolumic relaxation as the objective variable and echocardiographic parameters as independent variables, followed by multivariate regression analysis incorporating parameters with p < 0.10. Among the echocardiographic parameters, global longitudinal strain correlated most strongly with time constant of isovolumic relaxation (r = 0.778, p < 0.001). This was consistent with the partial correlation coefficients (r = 0.707, p < 0.001). Using stepwise multivariate regression analysis, only global longitudinal strain was found to be an independent predictor of time constant of isovolumic relaxation (adjusted R2 = 0.551). Global longitudinal strain could be used as a surrogate marker of time constant of isovolumic relaxation, an invasive indicator of relaxation impairment, in post-Fontan operation patients with a single right ventricle, preserved ejection fraction, and valve function.

Implantation of the Melody transcatheter pulmonary valve PB1016 in patients with dysfunctional right ventricular outflow tract conduits.

This study describes procedural and 1-year outcomes of the 16 mm Melody PB1016 valve in patients with dysfunctional RVOT conduits. The Melody PB1016 is a standard Melody valve produced from a 16 mm bovine jugular vein and is intended for deployment up to 20 mm. This is a prospective, non-randomized, multicenter study of the procedural and short-term outcomes of Melody PB1016 TPV replacement within dysfunctional RVOT conduits. Data from eight centers were included in the analysis. During the study period, 39 patients underwent attempted Melody TPVR. Of the 39 patients, 30 underwent successful Melody TPVR. The majority of patients underwent placement of one or more stents prior to TPVR. There was a significant reduction in peak conduit pressure gradient following TPVR (38 mmHg vs. 11 mmHg, P < 0.001). There were three cases of confined conduit tears successfully treated with covered stents or the valve itself. Repeat catheterization was performed in one patient for early re-obstruction that was successfully treated with balloon valvuloplasty. At recent follow-up, there were no cases of more than mild valve regurgitation and the mean pulmonary valve gradient by echocardiogram remained reduced relative to pre-TPVR implant measurements (33.5 mmHg vs. 15.2 mmHg). There were no cases of valve stent fracture or endocarditis reported at the 1-year follow-up. Our analysis of TPVR with the PB1016 valve in RVOT conduits showed it to be safe and effective and can be performed in a wide range of conduit sizes with preserved valve function. ClinicalTrials.gov Identifier: NCT02347189.

Pharmacologic and Pharmacomechanical Thrombolysis for Acute Deep Vein Thrombosis: Focus on ATTRACT CME.

Systemically delivered pharmacologic thrombolysis for acute deep vein thrombosis long ago gave way to catheter delivery of plasminogen activators within the clot. This simple concept resulted in markedly improved efficacy and safety. In an effort to accelerate thrombus dissolution or extraction, mechanical methods were developed, but the initial techniques left substantial residual thrombus that required subsequent catheter-directed thrombolysis (CDT). It was soon observed that combined pharmacomechanical thrombolysis was more effective than either one alone. Randomized trials of catheter-based strategies for thrombus removal have documented objective benefit, including improved patency, preserved valve function, and reduced post-thrombotic syndrome. The largest randomized study is the ATTRACT trial published at the end of 2017. Although mild post-thrombotic syndrome (PTS) was no different between the pharmacomechanical catheter-directed thrombolysis (PCDT) and control groups, acute pain and swelling and moderate-to-severe PTS were reduced with PCDT. Additional analyses from this robust data set are forthcoming.

Multicenter Experience Evaluating Transcatheter Pulmonary Valve Replacement in Bovine Jugular Vein (Contegra) Right Ventricle to Pulmonary Artery Conduits.

Follow-up of transcatheter pulmonary valve replacement (TPVR) with the Melody valve has demonstrated good short-term and long-term outcomes, but there are no published studies focused on valve performance in the Contegra bovine jugular vein conduit. This is a retrospective, multicenter study of the short- and intermediate-term outcomes of Melody TPVR within the Contegra conduit in the right ventricle to pulmonary artery position. Data from 13 centers were included in the analysis. During the study period, 136 patients underwent 139 catheterizations for attempted Melody TPVR with a median follow-up of 3 years (1 day to 9.1 years). Of the 136 patients, 117 underwent successful Melody TPVR. Two patients underwent a second Melody TPVR. The majority of patients underwent placement of ≥1 stents before transcatheter pulmonary valve implantation. There was a significant reduction in peak conduit pressure gradient acutely after transcatheter pulmonary valve implantation (39 versus 10 mm Hg; P<0.001). At most recent follow-up, the maximum pulmonary valve gradient by echocardiogram remained significantly reduced relative to prevalve implant measurements (65.9 versus 27.3 mm Hg; P<0.001). The incidence of Melody transcatheter pulmonary valve stent fracture (3.4%) and infectious endocarditis (4.3%) were both low. Serious adverse events occurred in 3 patients. Melody TPVR in Contegra conduits is safe and effective and can be performed in a wide range of conduit sizes with preserved valve function and low incidence of stent fracture and endocarditis.

Transcatheter Pulmonary Valve Replacement With the Edwards Sapien System: The Toronto Experience.

This study sought to review the outcomes for the Sapien and Sapien XT valves (Edwards Lifesciences, Irvine, California) for percutaneous pulmonary valve implantation (PPVI). PPVI has emerged as a viable alternative to surgery in patients with right ventricular (RV) outflow tract dysfunction. Limited data are available for the Sapien and Sapien XT valves in this setting. Retrospective analysis was performed for all patients to have undergone PPVI using the Edwards Sapien system at a large quaternary center. Twenty-five patients (70% male, mean age 34 ± 8.9 years) were identified. Primary underlying diagnosis was tetralogy of Fallot (n = 15), Ross procedure (n = 5), and other (n = 5). RV outflow tract characteristics included: biological valve (n = 16) and homograft (n = 9). Technical success was 96%. One patient required elective surgical pulmonary valve replacement for a high residual gradient. Pre-stenting was performed in all cases (52% covered stents). Valve sizes were 23 mm (n = 8), 26 mm (n = 15), and 29 mm (n = 2). Procedural hemodynamics revealed a decrease in the mean RV-to-systemic pressure ratio from 0.64 to 0.36 (p < 0.001) and RV-to-pulmonary artery (PA) gradient from 39 to 9 mm Hg (p < 0.001). No patient had clinically significant pulmonary regurgitation (PR). At a mean follow-up of 3.5 ± 2.1 years (range 0.3 to 7.2 years), there were no deaths. One patient required reintervention (no PR evident immediately post-procedure but severe valvular PR at 1 year requiring a valve-in-valve procedure). There were no episodes of endocarditis and no stent fractures. There was preserved valve function during follow-up with no change in RV-to-PA gradient nor PR severity. The Edwards Sapien system is a viable and durable option for PPVI in this single-center study.

Perivalvular extension of native mitral valve infective endocarditis with annular fistula and preserved valve function.

Perivalvular extension is a rare but severe complication mainly of aortic and prosthetic valve infective endocarditis (IE). In mitral IE, the extension is usually located posteriorly or laterally to the annulus. This case enlightens the value of multimodality imaging in this context. A 23-year-old male with no medical history presented an inaugural acute …

Abstract 13643: Impact of Aortic Valve Repair and Valve-sparing Procedures on the Mitral Annular Geometry Assessed by 3-dimensional Transesophageal Echocardiography

Background: Annular non-planarity, the "saddle-shape" of the mitral valve (MV) annulus, plays a role in minimizing leaflet stress and preserving valve function. Aortic valve (AV) repair/sparing procedures are increasingly used to treat aortic regurgitation (AR). The impact of these procedures on MV geometry and function is unknown. Methods: 2D and 3D transesophageal echocardiography (TEE) of the MV was acquired pre-operatively and immediately after surgery in 30 patients with severe AR and/or aortic root dilatation (Group 1 (n=10): bicuspid AV undergoing AV repair and valve-sparing root replacement with AV reimplantation; Group 2 (n=10): tricuspid AV undergoing AV repair and AV reimplantation; Group 3 (n=10): isolated AV cusp repair) and in 10 controls (Group 4). MV morphology was assessed by dedicated quantification software (fig. 1). Results: Comorbidities were similar in all groups. Groups 1, 2 and 3 had increased LV end-diastolic volumes compared to group 4 (214±90, 193±56, 180±55 vs. 86± 28ml for groups 1, 2, 3 and 4, respectively; p&lt;0.001); LVEF was similar (59.5 ± 6.2%). The baseline dimensions of the ventriculo-aortic junction and sinuses of Valsalva were larger in groups 1 and 2 vs. groups 3 and 4 (p&lt;0.0001). AV and MV parameters are summarized (table). Pre-operative MV parameters did not differ from those of normal subjects. The annular height and annular height to commissural width ratio (AHCWR) significantly decreased after surgery in groups 1 and 2, as did the tenting area. Significant changes in the coaptation depth and mitro-aortic angle were only found in group 1. Conclusions: AV repair/sparing procedures alter the MV geometry, including the non-planarity of the annulus and the depth of coaptation of the leaflets, especially among patients with a bicuspid AV undergoing AV reimplantation. These alterations could have long-term implications on MV function.

IMPACT OF AORTIC VALVE REPAIR AND VALVE-SPARING PROCEDURES ON THE MITRAL ANNULAR GEOMETRY ASSESSED BY 3-DIMENSIONAL TRANSESOPHAGEAL ECHOCARDIOGRAPHY

Background: Annular non-planarity, the saddle-shape of the mitral valve (MV) annulus, plays a role in minimizing leaflet stress and preserving valve function. Aortic valve (AV) repair/sparing procedures are increasingly used to treat aortic regurgitation (AR). The impact of these procedures on MV geometry and function is unknown. Methods: 2D and 3D transesophageal echocardiography (TEE) of the MV was acquired pre-operatively and immediately after surgery in 30 patients with severe AR and/or aortic root dilatation (Group 1 (n=10): bicuspid AV undergoing AV repair and valve-sparing root replacement with AV reimplantation; Group 2 (n=10): tricuspid AV undergoing AV repair and AV reimplantation; Group 3 (n=10): isolated AV cusp repair) and in 10 controls (Group 4). MV morphology was assessed by dedicated quantification software (fig. 1). Results: Comorbidities were similar in all groups. Groups 1, 2 and 3 had increased LV end-diastolic volumes compared to group 4 (214±90, 193±56, 180±55 vs. 86± 28ml for groups 1, 2, 3 and 4, respectively; p<0.001); LVEF was similar (59.5 ± 6.2%). The baseline dimensions of the ventriculo-aortic junction and sinuses of Valsalva were larger in groups 1 and 2 vs. groups 3 and 4 (p<0.0001). AV and MV parameters are summarized (table). Pre-operative MV parameters did not differ from those of normal subjects. The annular height and annular height to commissural width ratio (AHCWR) significantly decreased after surgery in groups 1 and 2, as did the tenting area. Significant changes in the coaptation depth and mitro-aortic angle were only found in group 1. Conclusions: AV repair/sparing procedures alter the MV geometry, including the non-planarity of the annulus and the depth of coaptation of the leaflets, especially among patients with a bicuspid AV undergoing AV reimplantation. These alterations could have long-term implications on MV function.

Role of coexisting contralateral primary venous disease in development of post-thrombotic syndrome following catheter-based treatment of iliofemoral deep venous thrombosis.

It has been reported that early clot removal benefits patients with iliofemoral deep venous thrombosis (DVT) by removing obstruction and preserving valve function. However, a substantial number of patients who had successful clot removal develop post-thrombotic syndrome (PTS). Residual thrombus and rethrombosis play a part in this phenomenon, but the role of coexisting primary chronic venous disease (PCVD) in these patients has not been studied. All patients who underwent catheter-based techniques of thrombus removal for symptomatic acute iliofemoral DVT during a 5-year period compose the study group. These patients were assessed for PTS by the Villalta scale, the Venous Clinical Severity Score (VCSS), and the Venous Insufficiency Epidemiological and Economic Study on Quality of Life (VEINES-QOL) questionnaire. The presence of coexisting PCVD was determined by clinical and duplex ultrasound findings in the contralateral leg at the time of the initial DVT diagnosis. Patients who had coexisting PCVD were compared with those without PCVD. Forty patients (40 limbs) were included in the study group. At initial diagnosis, 15 patients (38%) had coexisting symptomatic primary valve reflux in the unaffected limb. After thrombolysis, 9 of 40 limbs (22%) had complete lysis, 29 (73%) had ≥ 50% to 99% lysis, and 2 (5%) had <50% lysis. The mean percentage of lysis in patients with or without PCVD was similar (78% vs 86%; P = .13). Patients without coexisting PCVD had significantly better Villalta score and VCSS compared with those with coexisting PCVD (Villalta score, 2.52 vs 3.27, P = .014; VCSS, 2.96 vs 3.29, P = .005). Forty-five percent of patients (18 of 40) developed PTS. Patients who developed PTS had less clot lysis than those without PTS. This was true for patients with coexisting PCVD (60% vs 85%; P = .025) and in patients without PCVD (75% vs 89%; P = .013). There was no significant difference in the VEINES-QOL score between those with or without PCVD (79.5 vs 80.5; P = .9). Patients who had reflux in the treated limb after lysis had a five times greater chance for development of PTS compared with those who retained normal valve function during follow-up (odds ratio, 5.3; 95% confidence interval, 1.6-17.045). However, in patients with normal veins in the contralateral leg, the chance of development of PTS was 1.5 times higher if reflux was present in the treated limb (odds ratio, 1.49; 95% confidence interval, 0.043-10.253). Coexisting PCVD is a contributing factor to development of PTS after treatment of iliofemoral DVT with thrombus removal techniques.

Iliofemoral deep vein thrombosis: Percutaneous endovascular treatment options

Venous thromboembolism is defined as an acute venous thrombotic event that targets two disease entities: deep vein thrombosis (DVT), pulmonary embolism, or both. The most common site of DVT origin is in the lower extremities, with 50% of patients exhibiting no symptoms. Although anticoagulation is the gold standard for DVT, early clot removal, especially of proximal iliofemoral DVT, is felt to reduce the incidence of postthrombotic syndrome (PTS) by preserving valve function. Up to one-half of all patients with an iliofemoral DVT treated only with anticoagulation subsequently develop long-term complications, including PTS. Beside anticoagulation, DVT treatment options may include pharmaceutical and/or mechanical therapies. Mechanical therapies consist of either endovascular percutaneous catheter-directed (PCD) interventions or open operative thrombectomy. There are several different PCD procedures available, consisting of catheter-directed thrombolysis, mechanical thrombectomy, combination pharmacomechanical devices, and postthrombus extraction (angioplasty and/or stenting). Endovascular therapies in the management of acute iliofemoral DVT are evolving with a variety of devices available to treat this disease entity. The purpose of this article is to provide an overview of the PCD therapies used when treating patients experiencing an acute iliofemoral DVT along with associated nursing considerations. Off-label device use is not included.

Anatomic and functional outcomes of pharmacomechanical and catheter-directed thrombolysis of iliofemoral deep venous thrombosis.

Pharmacomechanical thrombolysis (PMT) and catheter-directed thrombolysis (CDT) are commonly used for the treatment of iliofemoral deep venous thrombosis (DVT). The purpose of this study was to examine the short- and long-term venous patency and venous valvular function as well as clinical outcomes of patients treated for iliofemoral DVT by PMT and CDT. A retrospective review of all patients with symptomatic DVT treated between 2006 and 2011 with PMT or CDT was performed. All patients were treated by local tissue plasminogen activator delivered with PMT or CDT. Patients were divided into two groups on the basis of initial treatment modality: patients treated by PMT alone (group 1), and those who underwent PMT and CDT or CDT alone (group 2). Group comorbidities, initial presenting symptoms, and Clinical, Etiologic, Anatomic, and Pathologic (CEAP) classification scores were compared. Postprocedural duplex ultrasound was used to assess valve function and treated vein patency rates. At all visits, Villalta and CEAP scores were recorded and compared. Group demographic and procedural results were analyzed by Fisher exact test for dichotomous variables and Kruskal-Wallis equality-of-populations rank test for the ordinal and continuous data. Kaplan-Meier survival estimates were used to assess preserved valve function as well as primary and secondary patency rates. There were 79 patients with 102 limbs treated for extensive iliofemoral DVT (median age, 51.5years; range, 16.6-83.8years). There were 18 patients in group 1 and 61 patients in group 2 (PMT+ CDT [n= 54] or CDT alone [n= 7]). There were no differences in demographics or comorbidities between groups aside from malignant disease, which was more common in group 1 (35.3% vs 11.5%; P=.03). A total of 102 limbs were analyzed, 24 in group 1 and 78 in group 2. Patients in group 1 had a shorter symptom duration compared with group 2 (7days vs 16days; P=.011). The median number of procedures in group 1 was lower than in group 2 (P< .001). At last clinical follow-up, there was no significant difference between the Villalta and CEAP scores or the rate of clinical improvement in symptoms between groups. By Kaplan-Meier analysis, there was no difference in primary patency, secondary patency, and treated valve function at 48months. This study suggests that PMT as a stand-alone therapy is as effective as CDT with or without PMT in preserving valve function and preventing postthrombotic syndrome. Long-term physiologic and functional outcomes are comparable between the modalities, with preserved venous valve function in the majority of patients.

Inflow thrombosis does not adversely affect thrombolysis outcomes of symptomatic iliofemoral deep vein thrombosis

The presence of popliteal or tibial vein clot is thought to adversely affect thrombolysis for iliofemoral deep vein thrombosis (DVT). We examined the effect of inflow thrombosis on functional and anatomic outcomes. Data for 44 patients treated for symptomatic iliofemoral DVT between 2006 and 2009 were retrospectively reviewed. All patients were treated by pharmacomechanical thrombectomy with local lytic therapy. Catheter-directed lysis and vena cava filters were used sparingly. Univariate and multivariate logistic regression analyses were used. The independent variable used in the logistic regression model was symptom relief. Forty-four patients (mean age, 52.1 ± 15.8 years) presented with symptoms averaging 13.4 ± 9.9 days in duration. Twenty (45.4%) had symptoms for >14 days. Seventeen patients were treated in one session, but 27 patients required lytic infusion for residual thrombus. Iliac stenting was required in 49% of limbs. Successful lysis (>50%) was achieved in 91% of patients, and symptom resolution or improvement in 91%. All patients became ambulatory, with no or minimal limitation. No major systemic bleeding complications occurred. Freedom from DVT recurrence and reintervention was 84% at 24 months by life-table analysis. Preoperative ultrasound imaging showed 89% had popliteal and tibial clots. A thrombosed popliteal vein was accessed for treatment and was corroborated by venographic findings. One patient required simultaneous tibial lysis. At a mean follow up of 8.7 ± 6.3 months, 41 patients (93%) had no symptom recurrence, 82% had preserved valve function and no reflux on duplex imaging, with a mean CEAP class of 1.4 and Villalta score of 3.3. Inflow thrombus had no adverse effect on symptom relief, treatment duration, patency, CEAP class, or valve reflux. Interestingly, 90% of patients with initial popliteal thrombus had a patent popliteal vein on postlysis ultrasound imaging, and the presence of tibial thrombus on presentation was predictive of symptom relief with thrombolysis (odds ratio, 13.03; 95% confidence interval, 1.02-165.58; P = .048). Inflow thrombosis is common and does not preclude successful thrombolysis of iliofemoral DVT. Valve function is preserved on midterm follow-up, with maintained CEAP class and symptom relief.

Thrombolysis for Lower-Extremity Deep Vein Thrombosis

Elimination of the embolic potential of existing thrombus, restoration of unobstructed flow, prevention of further thrombosis, and preservation of venous valve function are the ideal goals of therapy for acute deep vein thrombosis (DVT). Meeting these goals will not only prevent pulmonary embolus, but will also minimize long-term sequelae of venous hypertension and development of postthrombotic syndrome (PTS). Treatment strategies aimed at eliminating or reducing risk of PTS should focus on preserving valvular function and eliminating risk of continued venous obstruction after acute DVT. Thrombolytic agents are an attractive form of early therapy because they have the ability to eliminate obstructive thrombus in the deep veins, and should therefore help provide protection against PTS. Perceived benefits of early and rapid recanalization in preserving valve function have been the basis for lytic therapy to treat acute DVT. Data from the National Venous Registry and subsequent reports on the role of catheter-directed thrombolysis for treatment of acute lower-extremity DVT indicate that the technique is safe and effective in select patients. More recently, implementation of percutaneous mechanical devices designed to quickly remove acute thrombus has had a significant impact on time and cost of catheter-directed thrombolysis procedure. Although the long-term benefits of this form of therapy are not yet completely known, the Venous Registry can serve as a guide to the judicious selection of patients who will most benefit from this aggressive form of therapy.

TCT-492: Preserved valve function: 12 months echographic follow up post TAVI

TCT-492: Preserved valve function: 12 months echographic follow up post TAVI

The quantitative benefit of isolated, segmental, pharmacomechanical thrombolysis (ISPMT) for iliofemoral venous thrombosis

Early thrombus removal in patients with iliofemoral deep venous thrombosis (IFDVT) reduces postthrombotic morbidity. Preserving valve function and relieving venous obstruction prevents deterioration of quality of life and loss of economic potential. The preferred method for treating IFDVT is catheter-directed thrombolysis (CDT). Recently, isolated segmental pharmacomechanical thrombolysis (ISPMT) has emerged as a treatment option for patients with extensive IFDVT. The purpose of our study is to determine whether there are advantages to using ISPMT as the primary treatment for patients with iliofemoral IFDVT and, if so, to quantify those advantages relative to CDT. Forty-three patients with IFDVT were treated with percutaneous CDT between May 2003 and June 2007. Twenty-one patients (27 limbs) were treated with CDT and 22 patients (25 limbs) were treated with ISPMT +/- CDT. Demographics, extent of thrombus, procedural details, and thrombus resolution were recorded. Treatment time (55.4 vs 23.4 hours; P < .0001) and dose of rt-PA (59.3 vs 33.4 mg; P = .0009) were decreased and overall lytic success (60% vs 80%; P = .0016) increased with ISPMT. Adjunctive venoplasty and stenting, complications, hospital length-of-stay (LOS), and intensive care unit LOS were similar between groups. ISPMT offers more effective thrombus removal in less time and with a reduced dose of thrombolytic agent. However, decreased treatment time did not translate into decreased hospital or ICU stay. Longer-term follow-up is required to determine whether improved thrombus resolution translates to better functional outcome and reduced postthrombotic morbidity.

Mortality in patients with paravalvular abscess diagnosed by transesophageal echocardiography

Background Paravalvular abscess is a complication of endocarditis that may lead to persistent infection, conduction abnormalities, fistula formation, worsening congestive heart failure, and death. Methods Between 1991 and 2001, paravalvular abscess was identified on transesophageal echocardiography in 24 patients who subsequently underwent surgical treatment. Echocardiographic findings were reviewed for location of abscess, presence of a valvular prosthesis, valvular function, and presence of vegetations. Information gathered included the time interval between transesophageal echocardiography diagnosis and operation, inhospital mortality, and microbiologic data. Results Of 24 patients, 9 died, for a mortality of 38%. Of the patients who died, the average survival after operation was 43 days, with a range of 1 to 238 days. Of the 14 patients with significant valvular or paravalvular regurgitation, 8 died (57%). However, of the 10 patients with mild or no regurgitation, only 1 died (10%). This difference was statistically significant ( P = .02). Conclusion Patients without preserved valve function (those with moderate or severe regurgitation) have a significantly worse outcome (57% mortality) than do those with normal valvular function (10% mortality).

Catheter-directed thrombolysis for lower extremity deep vein thrombosis

The elimination of the embolic potential of existing thrombus, the restoration of unobstructed flow, the prevention of further thrombosis, and the preservation of venous valve function are the ideal goals of therapy for acute deep vein thrombosis (DVT). Meeting these goals will not only prevent pulmonary embolism but will also minimize the long-term sequelae of venous hypertension and the development of postthrombotic syndrome (PTS). Treatment strategies aimed at eliminating or reducing the risk of PTS should focus on preserving valvular function and eliminating the risk of continued venous obstruction after acute DVT. Thrombolytic agents are an attractive form of early therapy because they have the ability to eliminate obstructive thrombus in the deep veins and should therefore help provide protection against PTS. The perceived benefits of early and rapid recanalization in preserving valve function has been the basis for the use of lytic therapy to treat acute DVT.

Thrombolytic Therapy for Lower Extremity Deep Vein Thrombosis and the North American Venous Registry

The ideal goals of therapy for acute deep vein thrombosis (DVT) is the elimination of the embolic potential of existing thrombus, restoration of unobstructed flow, prevention of further thrombosis, and preservation of venous valve function. Meeting these goals will not only prevent pulmonary embolism (PE) but will also minimize the long-term sequelae of venous hypertension and the development of the post-thrombotic syndrome (PTS). Treatment strategies aimed at eliminating or reducing the risk of PTS should focus on preserving valvular function and eliminating the risk of continued venous obstruction following acute DVT. Thrombolytic drugs are an attractive form of early therapy because they have the ability to eliminate obstructive thrombus in the deep veins and should therefore help provide protection against PTS. The perceived benefits of early and rapid recanalization in preserving valve function have been the basis for the use of thrombolytic therapy to treat acute DVT.

A Novel Technique in a Sheep Model for Evaluating Prosthetic Heart Valve Performance

There have been many various animal studies to evaluate the structural integrity and antithrombogenicity of prosthetic heart valves. We were interested in developing a novel sheep model to study the thrombogenicity of mechanical heart valves placed into the systemic circulation but without the need for cardiac bypass. Also, we wanted to minimize the risk of paraplegia from complete thoracic aortic clamping. Six sheep underwent left lateral thoracotomy for placement of a mechanical heart valve in parallel with the descending thoracic aorta. A valved conduit with a dacron tube graft sutured to the back end was fashioned. Employing partial aortic occlusion with a side-biting clamp, the proximal and distal ends were anastomosed in an end-to-side fashion. Once flow was confirmed through the graft, the native aorta was occulded with umbilical tape. The sheep received no postoperative anticoagulation. The median operative time and estimated blood loss (EBL) was 170 min and 250 cc, respectively. Patency of the valved conduits was confirmed during the initial procedure, and there was no incidence of paraplegia postoperatively. Two animals expired shortly after extubation and at necropsy the valved conduits were patent with preserved valve function. The four survivors were sacrificed a median of 37 days postoperatively. Prior to euthanasia, the valved conduits were evaluated in situ with ultrasound. In all cases, the valves had clot formation at the hinges, which prevented active movement of the leaflets. This novel in vivo technique provides an alternative in testing the thrombogenicity of prosthetic heart valves without cardiac bypass or the risk of paraplegia in an animal that is extremely sensitive to complete aortic cross-clamp.