Randomized Controlled Study of an Absorbable Vena Cava Filter in a Porcine Model.

PURPOSE: To compare the safety and efficacy of an absorbable inferior vena cava (IVC) filter and a benchmark IVC filter in a porcine model. MATERIALS AND METHODS: A randomized controlled Good Laboratory Practice study was performed in Domestic Yorkshire cross swine. Sixteen swine were implanted with an absorbable IVC filter (test device; Adient Medical, Pearland, Texas); 8 were implanted with a benchmark metal IVC filter (control device; Cook Medical, Bloomington, Indiana). All animals underwent rotational digital subtraction pulmonary angiography and cavography (anteroposterior and lateral) before filter deployment and 5 and 32 weeks after deployment. Terminal procedures and necropsy were performed at 32 weeks. The IVC, heart, lungs, liver, and kidneys were harvested at necropsy. The reported randomized controlled GLP animal study was conducted at Synchrony Labs, Durham, North Carolina. RESULTS: One animal died early in the test cohort of a recurring hemorrhage at the femoral access site resulting from a filter placement complication. All other animals remained clinically healthy throughout the study. No pulmonary embolism was detected at the 5- and 32-week follow-up visits. The absorbable filter subjects experienced less caval wall perforation (0% vs 100%) and thrombosis (0% vs 75%). The control device routinely perforated the IVC and occasionally produced collateral trauma to adjacent tissues (psoas muscle and aorta). The veins implanted with the absorbable filter were macroscopically indistinguishable from normal adjacent veins at 32 weeks except for the presence of radiopaque markers. Nontarget tissues showed no device-related changes. CONCLUSIONS: Implantation of the absorbable IVC filter in swine proved safe with no pulmonary emboli detected. There was complete to near-complete resorption of the filter polymer by 32 weeks with restoration of the normal appearance and structure of the IVC.

Implantable intravascular defibrillator: evaluation of defibrillation waveforms with inferior vena cava electrode system.

BACKGROUND: A percutaneously placed, totally intravascular defibrillator has been developed that shocks via a right ventricular (RV) single-coil and titanium electrodes in the superior vena cava (SVC) and the inferior vena cava (IVC). This study evaluated the defibrillation threshold (DFT) with this electrode configuration to determine the effect of different biphasic waveform tilts and second-phase durations as well as the contribution of the IVC electrode. METHODS: Eight Bluetick hounds (wt = 30-40 kg) were anesthetized and the RV coil (first-phase anode) was placed in the RV apex. The intravascular defibrillator (PICD®, Model no. IIDM-G, InnerPulse Inc., Research Triangle Park, NC, USA) was positioned such that the titanium electrodes were in the SVC and IVC . Ventricular fibrillation was electrically induced and a Bayesian up-down technique was employed to determine DFT with two configurations: RV to SVC + IVC and RV to SVC. Three waveform tilts (65%, 50%, and 42%) and two second-phase durations (equal to the first phase [balanced] and truncated at 3 ms [unbalanced]) were randomly tested. The source capacitance of the defibrillator was 120 µF for all waveforms. RESULTS: DFT with the IVC electrode was significantly lower than without the IVC electrode for all waveforms tested (527 ± 9.3 V [standard error], 14.5 J vs 591 ± 7.4 V, 18.5 J, P < 0.001). Neither waveform tilt nor second-phase duration significantly changed the DFT. CONCLUSION: In canines, a totally intravascular implantable defibrillator with electrodes in the RV apex, SVC, and IVC had a DFT similar to that of standard nonthoracotomy lead systems. No significant effect was noted with changes in tilt or with balanced or unbalanced waveforms.

Novel intravascular defibrillator: defibrillation thresholds of intravascular cardioverter-defibrillator compared to conventional implantable cardioverter-defibrillator in a canine model.

BACKGROUND: An intravascular, percutaneously placed implantable defibrillator (InnerPulse percutaneous intravascular cardioverter-defibrillator [PICD]) with a right ventricular (RV) single-coil lead and titanium electrodes in the superior vena cava (SVC) and the inferior vena cava (IVC) has been developed. OBJECTIVE: The purpose of this study was to compare defibrillation thresholds (DFTs) of the PICD to those of a conventional implantable cardioverter-defibrillator (ICD) in canines. METHODS: Eight Bluetick hounds were randomized to initial placement of either a PICD or a conventional ICD. For PICD DFTs, a single-coil RV defibrillator lead was placed in the RV apex, and the device was positioned in the venous vasculature with electrodes in the SVC and IVC. With the conventional ICD, an RV lead was placed in the RV apex and an SVC coil was appropriately positioned. The ICD active can (AC) was implanted in a subcutaneous pocket formed in the left anterior chest wall and connected to the lead system. DFT was determined by a three-reversal, step up-down method to estimate the 80% success level. Two configurations were tested for the conventional ICD (#1: RV to SVC+AC; #2: RV to AC). A single configuration (RV to SVC+IVC) was evaluated for the PICD. RESULTS: Mean PICD DFT was 14.8 ± 1.53 (SE) J. Conventional #1 configuration demonstrated mean DFT of 20.2 ± 2.45 J and #2 of 27.5 ± 1.95 J. The PICD had a significantly lower DFT than the better conventional ICD configuration (#1; mean difference 5.4 ± 2.1 J, P <.05, paired t-test, N = 8). CONCLUSION: The new intravascular defibrillator had a significantly lower DFT than the conventional ICD in this canine model.

Preliminary observations using optical coherence tomography to assess neointimal coverage of a metal stent in a porcine model.

BACKGROUND: Concerns surrounding late stent thrombosis have prompted the development of novel imaging techniques to assess neointimal coverage. Recent clinical studies have evaluated optical coherence tomography (OCT) to evaluate neointimal coverage, but pathologic correlation in an animal model is lacking. We assessed the hypothesis that OCT could accurately assess early neointimal coverage in a porcine model. METHODS: OCT imaging of bare metal stents in each coronary artery was performed at implantation (n=6), Day 4 (n=3), and Day 20 (n=3), and images were evaluated at three cross-sections per stented segment. Neointimal strut coverage was categorized by OCT as covered or uncovered, and neointimal thickness was determined (Day 20). Pathological correlation was obtained using scanning electron microscopy (SEM) to assess strut coverage (Day 4) and histomorphometry to quantify neointimal thickness (Day 20). RESULTS: At Day 4, OCT imaging detected 28 (26%) of 109 uncovered struts, and the ratio of uncovered/total strut area by SEM was 31%. All imaging modalities showed complete coverage at Day 20. Mean (+/-SE) neointimal thickness at Day 20 was 109+/-6 microm by OCT (n=116 struts) and 93+/-5 microm by pathology (n=68). Mean neointimal thickness on a segment-by-segment basis determined by OCT correlated with mean histomorphometric analysis (Reviewer 1: r=.74, P=.092 and Reviewer 2: r=0.60, P=.212). CONCLUSIONS: Day 4 represents an important time point for the assessment of early neointimal coverage in the porcine model. OCT imaging accurately assesses the extent and thickness of early neointimal coverage with good pathologic correlation. OCT represents a promising imaging modality for the in vivo assessment of neointimal coverage.