Evaluation of Accuracy and Safety of the Next-Generation Up to 180-Day Long-Term Implantable Eversense Continuous Glucose Monitoring System: The PROMISE Study

Background: Use of continuous glucose monitoring (CGM) systems is being rapidly adopted as standard of care for insulin-requiring patients with diabetes. The PROMISE study (NCT03808376) evaluated the accuracy and safety of the next-generation implantable Eversense CGM system for up to 180 days. Methods: This was a prospective multicenter study involving 181 subjects with diabetes at 8 USA sites. All subjects were inserted with a primary sensor. Ninety-six subjects had a second sensor, either an identical sensor or a modified sensor (sacrificial boronic acid [SBA]), inserted in their other arm (53 and 43 subjects, respectively). Accuracy was evaluated by comparing CGM to YSI 2300 glucose analyzer (Yellow Springs Instrument [YSI]) values during 10 clinic visits (day 1-180). Confirmed event detection rates, calibration stability, sensor survival, and serious adverse events (SAEs) were evaluated. Results: For primary sensors, the percent CGM readings within 20%/20% of YSI values was 92.9%; overall mean absolute relative difference (MARD) was 9.1%. The confirmed alert detection rate at 70 mg/dL was 93% and at 180 mg/dL was 99%. The median percentage of time for one calibration per day was 56%. Sixty-five percent of the primary sensors survived to 180 days. For the SBA sensors, the percent CGM readings within 20%/20% of YSI values was 93.9%; overall MARD was 8.5%. The confirmed alert detection rate at 70 mg/dL was 94% and at 180 mg/dL was 99%. The median percentage of time for one calibration per day was 63%. Ninety percent of the SBA sensors survived to 180 days. No device- or insertion/removal procedure-related SAEs were reported. Conclusion: These data show the next-generation Eversense CGM system had sustained accuracy and safety up to 180 days, with an improved calibration scheme and survival, using the primary or SBA sensors.

Clinical use of a 180-day implantable glucose sensor improves glycated haemoglobin and time in range in patients with type 1 diabetes

AIMS

This real-world study evaluated the changes in glycated haemoglobin (HbA1c) and continuous glucose monitoring (CGM) metrics associated with use of the implantable 180-day Eversense CGM System (Eversense) in patients with type 1 diabetes.

MATERIALS AND METHODS

This was a prospective, multicentre, observational study among adult participants aged ≥18 years with type 1 diabetes across seven diabetes-care centres in Italy who had Eversense inserted for the first time. HbA1c was measured at baseline and at 180 days. Changes in time in range [TIR (glucose 70-180 mg/dL)], time above range [TAR (glucose >180 mg/dL)], time below range [TBR (glucose <70 mg/dL)] and glycaemic variability were also assessed. Data were also analysed by previous CGM use and by mode of insulin delivery.

RESULTS

One-hundred patients were enrolled (mean age 36 ± 12 years, mean baseline HbA1c 7.4 ± 0.92% [57 ± 10 mmol/mol]). Fifty-six per cent of patients were users of the continuous subcutaneous insulin infusion pump and 45% were previous users of CGM. HbA1c significantly decreased in patients after 180 days of sensor wear (-0.43% ± 0.69%, 5 ± 8 mmol/mol, P < 0.0001). As expected, CGM-naïve patients achieved the greatest reduction in HbA1c (-0.74% ± 0.48%, 8 ± 5 mmol/mol). TIR significantly increased and TAR and mean daily sensor glucose significantly decreased while TBR did not change after 180 days of sensor wear.

CONCLUSIONS

Real-world clinical use of the Eversense CGM System for 180 days was associated with significant improvements in HbA1c and CGM metrics among adults with type 1 diabetes. The study is registered on clinicaltrials.gov (NCT04160156).

Longitudinal Analysis of Real-World Performance of an Implantable Continuous Glucose Sensor over Multiple Sensor Insertion and Removal Cycles

The Eversense® Continuous Glucose Monitoring (CGM) System, with the first long-term, implantable glucose sensor, has been commercially available in Europe and South Africa since 2016 for adults with diabetes. The performance of the sensor over multiple, sequential 90- or 180-day cycles from either real-world experience or clinical studies has not been previously published. The Eversense Data Management System (DMS) was used to evaluate the accuracy of General Data Protection Regulation (GDPR)-compliant sensor glucose (SG) values against self-monitoring of blood glucose (SMBG) from June 2016 through August 2019 among patients with at least four sensor cycles from European and South African health care practices. Mean SG and associated measures of variability, glucose management indicator (GMI), and percent and time in various hypoglycemic, euglycemic, and hyperglycemic ranges were calculated for the 24-h time period over each cycle. In addition, transmitter wear time was evaluated across each sensor wear cycle. Among the 945 users included in the analysis, the mean absolute relative difference (standard deviation [SD]) using 152,206, 174,645, 206,024, and 172,587 calibration matched pairs against SMBG was 11.9% (3.6%), 11.5% (4.0%), 11.8% (4.7%), and 11.5% (4.1%) during the first four sensor cycles, respectively. Mean values of the CGM metrics over the first sensor cycle were 156.5 mg/dL for SG, 54.7 mg/dL for SD, 0.35 for coefficient of variation, and 7.04% for GMI. Percent SG at different glycemic ranges was as follows: <54 mg/dL was 1.1% (16 min), <70 mg/dL was 4.6% (66 min), ≥70-180 mg/dL (time in range) was 64.5% (929 min), >180-250 mg/dL was 22.8% (328 min), and >250 mg/dL was 8.1% (117 min). The median transmitter wear time over the first cycle was 83.2%. CGM metrics and wear time were similar over the subsequent three cycles. This real-world evaluation of adult patients with diabetes using the Eversense CGM System in the home setting demonstrated that the implantable sensor provides consistent stable accuracy and CGM metrics over multiple, sequential sensor cycles with no indication of degradation of sensor performance.

Real-World Safety of an Implantable Continuous Glucose Sensor Over Multiple Cycles of Use: A Post-Market Registry Study

Previously, the safety and accuracy of the Eversense continuous glucose monitoring (CGM) system were characterized in three pivotal trials among individuals with type 1 diabetes (T1D) and type 2 diabetes (T2D) with a single 90- or 180-day sensor insertion-removal cycle. The Post-Market Clinical Follow-up (PMCF) registry is a prospective study evaluating the long-term safety and performance of the Eversense CGM system over multiple sensor insertion-removal cycles among adults with T1D and T2D. All patients who had a sensor subcutaneously implanted across 534 participating centers in Europe and South Africa from June 2016 to August 2018 were enrolled. Adverse events (AEs) were recorded at each visit and patients were instructed to inform their clinic if they experienced any AEs between visits. AEs were adjudicated for relatedness to the device, procedure, or drug (dexamethasone acetate). The primary safety endpoint was the rate of related serious adverse events (SAEs) through four sensor insertion-removal cycles. The registry enrolled 3023 patients. As of last follow-up, 5417 sensors had been inserted with a total of 1260 patient-years (PYs) of follow-up: 969 patients had used the system for at least 6 months and 173 patients had used the system for at least 1 year. No related SAEs were reported. The most frequently reported related AEs were sensor location site infection (0.96%; 2.46 events per 100 PYs), inability to remove the sensor upon first attempt (0.76%; 1.90 events per 100 PYs), and adhesive patch location site irritation (0.66%; 1.59 events per 100 PYs). One nonserious allergic reaction to lidocaine was reported, which resolved with administration of an antihistamine. The full intended sensor life was achieved by 91% of 90-day sensors and 75% of 180-day sensors. The PMCF registry provides real-world evidence that the Eversense CGM system is safe over multiple cycles of use.

Real-World Data from the First U.S. Commercial Users of an Implantable Continuous Glucose Sensor

Background: The Eversense^® Continuous Glucose Monitoring (CGM) System, with the first 90-day implantable sensor, received FDA (Food and Drug Administration) approval in June 2018. No real-world experience has been published. Methods: Deidentified sensor glucose (SG) data from August 1, 2018 to May 11, 2019 in the Eversense Data Management System (DMS) were analyzed for the first 205 patients who reached a 90-day wear period on the Eversense CGM system. The mean SG, standard deviation (SD), median interquartile range, coefficient of variation (CV), glucose measurement index (GMI), and percent and time in minutes across glucose ranges were computed for the 24-h time period, the nighttime (00:00-06:00), and by 30-day wear periods. Sensor accuracy, sensor reinsertion rate, transmitter wear time, and safety data were assessed. Results: Of the 205 patients, 129 identified as type 1, 18 as type 2, and 58 were unreported. Fifty were CGM naive, 112 had prior CGM experience, and 43 were unreported. The mean SG was 161.8 mg/dL, SD was 57.4 mg/dL, CV was 0.35, and GMI was 7.18%. Percent SG at <54 mg/dL was 1.2% (18 min), <70 mg/dL was 4.1% (59.7 min), time in range (≥70-180 mg/dL) was 62.3% (897.7 min), >180-250 mg/dL was 21.9% (315.8 min), and >250 mg/dL was 11.6% (166.7 min). Nighttime values were similar. The glucometric values were similar over 30-day time periods of the sensor wear. The mean absolute relative difference (SD) using 27,708 calibration paired points against home blood glucose meters was 11.2% (11.3%). The sensor reinsertion rate was 78.5%. The median transmitter wear time was 83.6%. There were no related serious adverse events. Conclusion: The Eversense real-world data showed promising glycemic results, sensor accuracy, and safety. These data suggest that the Eversense CGM system is a valuable tool for diabetes management.

First assessment of the performance of an implantable continuous glucose monitoring system through 180 days in a primarily adolescent population with type 1 diabetes

AIM

To investigate the performance of the Eversense XL implantable continuous glucose monitoring (CGM) system through 180 days in a primarily adolescent population with type 1 diabetes (T1D).

MATERIALS AND METHODS

This prospective, single-centre, single-arm, 180-day study evaluated the effectiveness and safety of the implantable CGM system in Canadian adolescent and adult subjects with T1D. Accuracy measures included mean absolute relative difference (MARD), 15/15% agreement between CGM glucose and blood glucose measured by Yellow Springs Instruments and surveillance error grid analysis. Adolescent subjects received one sensor in the upper arm and adult subjects received one sensor in each upper arm. In-clinic CGM system accuracy studies were performed every 30 days. The safety assessment included the incidence of adverse events related to either device or the insertion/removal procedure through 180 days.

RESULTS

Thirty-six subjects (30 adolescent/6 adult, 13 female/23 male, mean age 17 ± 9.2 years, mean body mass index 22 ± 4 kg/m² ) received the CGM system. Overall MARD was 9.4% (95% CI: 8.6%-10.5%). CGM system agreement at 15/15% (N = 7163) through 60, 120 and 180 days was 82.9% (95% CI: 78.4%-86.1%), 83.6% (95% CI: 80.4%-85.7%) and 83.4% (95% CI: 79.7%-85.5%), respectively. Surveillance error grid analysis showed 98.4% of paired values in clinically acceptable error zones A and B. No insertion/removal or device-related serious adverse events were reported.

CONCLUSION

The Eversense XL CGM system is safe and accurate through 180 days in a primarily adolescent population of subjects with T1D.

A Prospective Multicenter Evaluation of the Accuracy and Safety of an Implanted Continuous Glucose Sensor: The PRECISION Study

Background: A prior study (PRECISE II) demonstrated that an implantable continuous glucose monitoring (CGM) system (Eversense^® CGM System) provided accurate glucose readings through the 90-day sensor life with a favorable safety profile in participants with type 1 or type 2 diabetes (T1D, T2D). This study was performed to further characterize the accuracy of the system. Methods: PRECISION was a prospective multicenter study that evaluated the accuracy and safety of Eversense among adults with T1D or T2D through 90 days (NCT02647905). Accuracy measures included percentage system agreement and mean absolute relative difference (MARD) between Eversense and Yellow Springs Instrument reference measurements from 40 to 400 mg/dL. The primary safety endpoint was incidence of device-related or sensor insertion/removal procedure-related serious adverse events (SAEs) through 90 days. An updated glucose calculation algorithm was also applied to the sensor data from the PRECISE II study to evaluate consistency of accuracy results. Results: Thirty-five participants received the CGM system. Eighty-five percent of CGM values were within 15/15% of reference and the MARD value against reference was 9.6% (95% confidence interval [CI]: 8.9-10.4). All sensors were functional through day 90. No device- or procedure-related SAEs occurred. Application of the updated algorithm to PRECISE II sensor data resulted in 87% of readings within 15/15% of reference and an MARD value against reference of 8.5% (95% CI: 8.0%-9.1%). Conclusions: PRECISION corroborated prior accuracy and safety findings of the Eversense CGM System through the 90-day sensor life. The updated algorithm improved accuracy of measurements in PRECISE II.

Two-Year Outcomes of Vagal Nerve Blocking (vBloc) for the Treatment of Obesity in the ReCharge Trial

Background

The ReCharge Trial demonstrated that a vagal blocking device (vBloc) is a safe and effective treatment for moderate to severe obesity. This report summarizes 24-month outcomes.

Methods

Participants with body mass index (BMI) 40 to 45 kg/m², or 35 to 40 kg/m² with at least one comorbid condition were randomized to either vBloc therapy or sham intervention for 12 months. After 12 months, participants randomized to vBloc continued open-label vBloc therapy and are the focus of this report. Weight loss, adverse events, comorbid risk factors, and quality of life (QOL) will be assessed for 5 years.

Results

At 24 months, 123 (76 %) vBloc participants remained in the trial. Participants who presented at 24 months (n = 103) had a mean excess weight loss (EWL) of 21 % (8 % total weight loss [TWL]); 58 % of participants had ≥5 % TWL and 34 % had ≥10 % TWL. Among the subset of participants with abnormal preoperative values, significant improvements were observed in mean LDL (−16 mg/dL) and HDL cholesterol (+4 mg/dL), triglycerides (−46 mg/dL), HbA1c (−0.3 %), and systolic (−11 mmHg) and diastolic blood pressures (−10 mmHg). QOL measures were significantly improved. Heartburn/dyspepsia and implant site pain were the most frequently reported adverse events. The primary related serious adverse event rate was 4.3 %.

Conclusions

vBloc therapy continues to result in medically meaningful weight loss with a favorable safety profile through 2 years.

Trial Registration

https://clinicaltrials.gov/ct2/show/NCT01327976

Intermittent Vagal Nerve Block for Improvements in Obesity, Cardiovascular Risk Factors, and Glycemic Control in Patients with Type 2 Diabetes Mellitus: 2-Year Results of the VBLOC DM2 Study

BACKGROUND

One-year results of the VBLOC DM2 study found that intermittent vagal blocking (VBLOC therapy) was safe among subjects with obesity and type 2 diabetes mellitus (T2DM) and led to significant weight loss and improvements in glycemic parameters and cardiovascular risk factors. Longer-term data are needed to determine whether the results are sustained.

METHODS

VBLOC DM2 is a prospective, observational study of 28 subjects with T2DM and body mass index (BMI) between 30 and 40 kg/m(2) to assess mid-term safety and weight loss and improvements in glycemic parameters, and other cardiovascular risk factors with VBLOC therapy. Continuous outcome variables are reported using mixed models.

RESULTS

At 24 months, the mean percentage of excess weight loss was 22% (95% CI, 15 to 28, p < 0.0001) or 7.0% total body weight loss (95% CI, 5.0 to 9.0, p < 0.0001). Hemoglobin A1c decreased by 0.6 percentage points (95% CI, 0.2 to 1.0, p = 0.0026) on average from 7.8% at baseline. Fasting plasma glucose declined by 15 mg/dL (95% CI, 0 to 29, p = 0.0564) on average from 151 mg/dL at baseline. Among subjects who were hypertensive at baseline, systolic blood pressure declined 10 mmHg (95% CI, 2 to 19, p = 0.02), diastolic blood pressure declined by 6 mmHg (95% CI, 0 to 12, p = 0.0423), and mean arterial pressure declined 7 mmHg (95% CI, 2 to 13, p = 0.014). Waist circumference was significantly reduced by 7 cm (95% CI, 4 to 10, p < 0.0001) from a baseline of 120 cm. The most common adverse events were mild or moderate heartburn, implant site pain, and constipation.

CONCLUSIONS

Improvements in obesity and glycemic control were largely sustained after 2 years of treatment with VBLOC therapy with a well-tolerated risk profile.

Sustained Weight Loss with Vagal Nerve Blockade but Not with Sham: 18-Month Results of the ReCharge Trial

BACKGROUND/OBJECTIVES

Vagal block therapy (vBloc) is effective for moderate to severe obesity at one year.

SUBJECTS/METHODS

The ReCharge trial is a double-blind, randomized controlled clinical trial of 239 participants with body mass index (BMI) of 40 to 45 kg/m or 35 to 40 kg/m with one or more obesity-related conditions. Interventions were implantation of either vBloc or Sham devices and weight management counseling. Mixed models assessed percent excess weight loss (%EWL) and total weight loss (%TWL) in intent-to-treat analyses. At 18 months, 142 (88%) vBloc and 64 (83%) Sham patients remained enrolled in the study.

RESULTS

18-month weight loss was 23% EWL (8.8% TWL) for vBloc and 10% EWL (3.8% TWL) for Sham (P < 0.0001). vBloc patients largely maintained 12-month weight loss of 26% EWL (9.7% TWL). Sham regained over 40% of the 17% EWL (6.4% TWL) by 18 months. Most weight regain preceded unblinding. Common adverse events of vBloc through 18 months were heartburn/dyspepsia and abdominal pain; 98% of events were reported as mild or moderate and 79% had resolved.

CONCLUSIONS

Weight loss with vBloc was sustained through 18 months, while Sham regained weight between 12 and 18 months. vBloc is effective with a low rate of serious complications.

Effect of reversible intermittent intra-abdominal vagal nerve blockade on morbid obesity: the ReCharge randomized clinical trial

IMPORTANCE

Although conventional bariatric surgery results in weight loss, it does so with potential short-term and long-term morbidity.

OBJECTIVE

To evaluate the effectiveness and safety of intermittent, reversible vagal nerve blockade therapy for obesity treatment.

DESIGN, SETTING, AND PARTICIPANTS

A randomized, double-blind, sham-controlled clinical trial involving 239 participants who had a body mass index of 40 to 45 or 35 to 40 and 1 or more obesity-related condition was conducted at 10 sites in the United States and Australia between May and December 2011. The 12-month blinded portion of the 5-year study was completed in January 2013.

INTERVENTIONS

One hundred sixty-two patients received an active vagal nerve block device and 77 received a sham device. All participants received weight management education.

MAIN OUTCOMES AND MEASURES

The coprimary efficacy objectives were to determine whether the vagal nerve block was superior in mean percentage excess weight loss to sham by a 10-point margin with at least 55% of patients in the vagal block group achieving a 20% loss and 45% achieving a 25% loss. The primary safety objective was to determine whether the rate of serious adverse events related to device, procedure, or therapy in the vagal block group was less than 15%.

RESULTS

In the intent-to-treat analysis, the vagal nerve block group had a mean 24.4% excess weight loss (9.2% of their initial body weight loss) vs 15.9% excess weight loss (6.0% initial body weight loss) in the sham group. The mean difference in the percentage of the excess weight loss between groups was 8.5 percentage points (95% CI, 3.1-13.9), which did not meet the 10-point target (P = .71), although weight loss was statistically greater in the vagal nerve block group (P = .002 for treatment difference in a post hoc analysis). At 12 months, 52% of patients in the vagal nerve block group achieved 20% or more excess weight loss and 38% achieved 25% or more excess weight loss vs 32% in the sham group who achieved 20% or more loss and 23% who achieved 25% or more loss. The device, procedure, or therapy-related serious adverse event rate in the vagal nerve block group was 3.7% (95% CI, 1.4%-7.9%), significantly lower than the 15% goal. The adverse events more frequent in the vagal nerve block group were heartburn or dyspepsia and abdominal pain attributed to therapy; all were reported as mild or moderate in severity.

CONCLUSION AND RELEVANCE

Among patients with morbid obesity, the use of vagal nerve block therapy compared with a sham control device did not meet either of the prespecified coprimary efficacy objectives, although weight loss in the vagal block group was statistically greater than in the sham device group. The treatment was well tolerated, having met the primary safety objective.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01327976.

Effects of high-frequency alternating current on axonal conduction through the vagus nerve

High-frequency alternating current (HFAC) is known to disrupt axonal conduction in peripheral nerves, and HFAC has much potential as a therapeutic approach for a number of pathological conditions. Many previous studies have utilized motor output as a bioassay of effects of HFAC on conduction through medium- to large-diameter motor axons. However, little is known about the effectiveness of HFAC on smaller, more slowly conducting nerve fibres. The present study tested whether HFAC influences axonal conduction through sub-diaphragmatic levels of the rat vagus nerve, which consists almost entirely of small calibre axons. Using an isolated nerve preparation, we tested the effects of HFAC on electrically evoked compound action potentials (CAPs). We found that delivery of charge-balanced HFAC at 5000 Hz for 1 min was effective in producing reversible blockade of axonal conduction. Both Aδ and C components of the vagus CAP were attenuated, and the degree of blockade as well as time to recovery was proportional to the amount of HFAC current delivered. The Aδ waves were more sensitive than C waves to HFAC blockade, but they required more time to recover.

Intra-abdominal vagal blocking (VBLOC therapy): clinical results with a new implantable medical device

BACKGROUND

A new medical device uses high-frequency electrical algorithms to create intermittent vagal blocking (VBLOC therapy). The aim is to assess the effects of vagal blocking on excess weight loss (EWL), safety, dietary intake, and vagal function.

METHODS

An open-label, 3-center study was conducted in obese subjects (body mass index [BMI] 35-50 kg/m(2)). Electrodes were implanted laparoscopically on both vagi near the esophagogastric junction to provide electrical block. Patients were followed for 6 months for body weight, safety, electrocardiogram, dietary intake, satiation, satiety, and plasma pancreatic polypeptide (PP) response to sham feeding. To specifically assess device effects alone, no diet or exercise programs were instituted.

RESULTS

Thirty-one patients (mean BMI, 41.2 +/- 1.4 kg/m(2)) received the device. Mean EWL at 4 and 12 weeks and 6 months after implant was 7.5%, 11.6%, and 14.2%, respectively (all P < .001); 25% of patients lost >25% EWL at 6 months (maximum, 36.8%). There were no deaths or device-related serious adverse events (AEs). Calorie intake decreased by >30% at 4 and 12 weeks and 6 months (all P <or= .01), with earlier satiation (P < .001) and reduced hunger (P = .005). After 12 weeks, plasma PP responses were suppressed (20 +/- 7 vs 42 +/- 19 pg/mL). Average percent EWL in patients with PP response <25 pg/mL was double that with PP response >25 pg/mL (P = .02). Three patients had serious AEs that required brief hospitalization, 1 each for lower respiratory tract, subcutaneous implant site seroma, and Clostridium difficile diarrhea.

CONCLUSIONS

Intermittent, intra-abdominal vagal blocking is associated with significant EWL and a desirable safety profile.

Description and evaluation of a ventriculo-coronary artery bypass device that provides bi-directional coronary flow

OBJECTIVE

The objective of this study was to assess acute patency of a new myocardial revascularization device that connects the left ventricular cavity to a coronary artery (termed ventriculo-coronary artery bypass, VCAB) thereby providing proximal and distal blood flow from the site of the anastomosis.

METHODS

A device made of expanded polytetrafluoroethylene and low density polyethylene was implanted from the base of the left ventricle to the mid left anterior descending coronary artery (LAD) in 11 juvenile domestic pigs using a beating heart approach. Flow rates were measured in the distal LAD before and after implant using ultrasonic flow techniques, and patency was assessed at explant at either 2 or 4 weeks post-implantation. Myocardial perfusion using positron emission tomography (PET) was assessed in a separate set of pigs (n=2) revascularized by VCAB 2 weeks post-implant.

RESULTS

Net forward flow distal to the implanted device was 73 +/- 15% of native LAD flow. PET demonstrated that the target myocardium was perfused at 85% of that seen in the remote, control myocardium. Device patency rate was 80% (4/5) at 2 weeks in one set of pigs and 83% (5/6) at 4 weeks in a second set of pigs. Histologic analysis showed formation of neointima along the extraventricular segment of the device.

CONCLUSIONS

This study demonstrates the promise of perfusing ischemic myocardium using a VCAB approach with a device that provides blood flow both proximal and distal to the anastomosis. Patency of the transmyocardial device was encouraging at 2 and 4 weeks and warrants further investigation.

Ventriculocoronary artery bypass results using a mesh-tipped device in a porcine model

BACKGROUND

In this report we describe the in vivo evaluation of a device and ventriculocoronary artery bypass procedure that creates a permanent transmyocardial channel between the left ventricle and a coronary artery.

METHODS

The transmyocardial device, an L-shaped titanium tube with a meshed distal tip and an exterior polyester cuff, was implanted from the base of the left ventricle to the proximal left anterior descending coronary artery in 11 healthy juvenile domestic pigs using a beating-heart approach. Flow rates were measured at implant. Patency was assessed at explant for surviving animals at 2 (n = 3) and 4 weeks (n = 4).

RESULTS

Flow through the transmyocardial device after implantation was 74% of base line. Forward flow occurred during systole. Luminal patency was 100% at 2 weeks and 75% at 4 weeks. Histologic analysis showed little to no intimal proliferation at the coronary interface.

CONCLUSIONS

This short-duration study shows promise for perfusing ischemic myocardium with systolic flow. The transmyocardial titanium conduit and treated coronary artery patency was good at 2 and 4 weeks and warrants further studies.

Ventriculocoronary artery bypass (VCAB), a novel approach to myocardial revascularization

BACKGROUND

The long-term patency rate of saphenous vein grafts for myocardial revascularization is poor (50% at 10 years). Half of the patent grafts develop severe atherosclerosis. In this paper, we report on an implantation technique and an in vivo evaluation of a device that creates a ventriculocoronary artery bypass (VCAB), a permanent transmyocardial channel between the left ventricle and a coronary artery.

METHODS

An L-shaped titanium tube with an exterior polyester cuff was implanted from the base of the left ventricle to the proximal left anterior descending coronary artery in 11 juvenile domestic pigs using a beating heart approach. Flow rates were measured at implantation. Patency was assessed when explanted at 2 weeks.

RESULTS

The flow rate through the device after implantation was 76% of baseline. Forward flow occurred during systole. The patency rate was 91% at 2 weeks. Histologic analysis showed the formation of an organizing tissue at the coronary interface.

CONCLUSIONS

These preliminary studies show the promise of perfusing ischemic myocardium with systolic flow. Patency of the transmyocardial titanium conduit was excellent at 2 weeks and warrants longer duration studies.

Human serum albumin and fibrinogen interactions with an adsorbed RGD-containing peptide

The modification of polyethylene terephthalate (PET) and polytetrafluoroethylene (PTFE) with an arginine-glycine-aspartic acid cell adhesion peptide, RGD peptide (PepTite Adhesive Coating; Telios Pharmaceuticals, San Diego, CA) has been previously investigated. Initial animal studies showed this RGD peptide to accelerate healing and assist in the formation of an endothelial cell lining of the lumenal side of PET and PTFE fabrics in a cardiovascular application. It is of interest to determine how this RGD peptide is able to influence cellular events through intervening layers of plasma proteins that spontaneously adsorb upon implantation. This study examined the interaction of predeposited RGD-containing peptide with human serum albumin (HSA) or fibrinogen that was characterized using multiple attenuated internal reflection infrared (MAIR-IR) spectroscopy, ellipsometry, and contact angle analysis. It was determined that fibrinogen-containing films consistently exhibited more mass than films of the RGD peptide, HSA, or HSA adsorbed onto RGD peptide-containing films. MAIR-IR spectra of RGD peptide films before and after HSA adsorption were similar in absorption and intensity; however, ellipsometry indicated HSA introduction had created thicker, less dense films. Fibrinogen, on the other hand, when adsorbed onto RGD peptide films provided increased relative mass in a more compact arrangement. Contact angle analyses of each of the dried films showed their surface energies to remain high, but the polar components of RGD peptide films were reduced after either serum protein adsorption. These phenomena may be related to the minimal thrombus accumulation that was noted during the initial animal studies, that promoted subsequent healing.

Silver modification of polyethylene terephthalate textiles for antimicrobial protection

The safety and in vitro effectiveness of applying silver to polyethylene terephthalate fabric mechanical heart valve (MHV) sewing cuffs for the prevention of prosthetic valve endocarditis (PVE) were evaluated. PVE is an infrequent but grave complication of cardiac surgery associated with mortality rates potentially exceeding 50%. A poor response to antibiotic therapy is partly responsible for the high mortality rates. Silver is a well known antimicrobial agent with broad effectiveness. Preliminary in vitro microbial challenge studies of the coated fabric using the New York State 63 bacteriostatic test and Dow Corning Shake Flask test showed a > or = 97% reduction for most organisms tested. Sheep mitral valve replacement studies suggest comparable tissue ingrowth of uncoated and coated fabric with a more organized, thinner pannus formed on silver coated fabric. Low levels of silver were present in the serum at all time periods. These results indicate MHVs with silver coated cuffs may provide additional protection against PVE.

Biocompatibility of silver-modified polyester for antimicrobial protection of prosthetic valves

BACKGROUND AND AIMS OF THE STUDY

The biocompatibility of a silver-coated polyethylene terephthlate (PET, polyester) fabric for the inhibition of prosthetic valve endocarditis (PVE) associated with mechanical heart valves (MHVs) was assessed. The infrequency of PVE is outweighed by mortality rates commonly exceeding 50%. These high mortality rates have been attributed to the poor effect of antibiotic therapy on colonized valves and infected myocardial tissue. Silver has been used as an antimicrobial for centuries due to its general effectiveness and relative lack of toxicity. Our previous work has shown PET polyester fabric coated with metallic silver by an ion beam-assisted deposition (IBAD) process to: (i) be effective in vitro in the inhibition of microbial attachment and colonization; (ii) be tightly adherent and low leaching; and (iii) promote tissue ingrowth and the organization of tissue pannus in a short-duration (five weeks) sheep mitral mechanical heart valve model.

METHODS

This paper addresses additional biocompatibility assessment consisting of a cell compatibility assay in which serum extracts of silver-coated fabric were exposed to fibroblasts for 48 hours, after which cell viability and function were measured. The amount of silver in the extract was measured using elemental analysis techniques.

RESULTS

No signs of toxicity were seen in the cells until the extract concentration reached 1200 p.p.m. Ten-week duration mechanical valve replacement studies in sheep with uncoated or coated polyester sewing cuffs showed comparable tissue ingrowth and mature pannus with a suggestion of a thinner pannus on the silver-coated fabric. Additional antimicrobial testing confirmed the effectiveness of this coating in inhibiting colonization of polyester fabric.

CONCLUSIONS

These current results, together with the earlier data, suggest that IBAD silver coating on polyester facilitates healing and may provide protection against PVE.

Platelet interaction with pyrolytic carbon heart-valve leaflets

Although the newest generation of mechanical heart-valve prosthetics constructed either partially or wholly of lowtemperature isotropic pyrolytic carbon (LTIC) have significantly reduced thromboembolic complications compared with early-generation mechanical valves (e.g., Starr-Edwards), thromboembolism remains an important clinical complication. In the present study, high-resolution, lowvoltage scanning electron microscopy (HR-LV-SEM) was used to examine the structure and platelet interaction properties of LTIC valve leaflets manufactured by both Carbo Medics, Inc. and by St. Jude Medical, Inc. Valve leaflets from both manufacturers, prepared and polished exactly as used in clinical heart valves, had similar surface energetics and elemental composition. Examination with LV-SEM revealed a rough and complex three-dimensional surface structure with nanometer- to micron-size features. In vitro adhesion of human platelets on the LTIC materials and Formvar were evaluated in the presence of 1 mg/mL albumin. Platelet-surface activation, as evaluated by shape change, spread area, and deposition, was extremely extensive on the LTIC materials compared with the Formvar positive control material. LTIC-adherent platelets were extremely thin, and closely followed the rough LTIC contours, greatly limiting their visibility with conventional SEM. These observations demonstrate that LTIC surfaces can extensively activate platelets even in the presence of albumin, thereby suggesting that platelet interactions with pyrolytic carbon may have a significant role in mechanical-valve thromboembolism.

Platelets are deposited early post-operatively on the leaflet of a mechanical heart valve in sheep without post-operative anticoagulants or antiplatelet agents. A scanning electron microscopic observation of the pyrolytic carbon surface in a mechanical heart valve

Pyrolytic carbon has been used for mechanical heart valves as a thromboresistant, wear resistant, and fatigue resistant material. Thrombosis and thromboembolism, however, remain major mechanical heart valve associated complications and may frequently occur during the early post-operative period. In depth morphologic studies on blood-pyrolytic carbon surface interactions are limited. The purpose of this study was to evaluate the blood compatibility of the pyrolytic carbon surface of St. Jude Medical mechanical heart valves that were implanted in the mitral position of sheep without the administration of post-operative anticoagulants or antiplatelet agents for 2, 4, and 6 weeks. Almost the entire leaflet and orifice ring surfaces were observed by scanning electron microscopy. Although the surfaces appeared clean macroscopically, when observed by electron microscopy, the surface were mottled, mainly by solitary platelets and aggregations. There were only a few leukocytes or red blood cells observed. No fibrin clots were observed on the leaflets. The density of platelet deposition was higher in the vicinity of the pivots and near the edges of the leaflets. The sizes of the platelet aggregations decreased with longer duration. The outer surfaces of the pivot guards were covered by various amounts of deposition composed of platelet aggregations and thrombi. Thus, the administration of antiplatelet agents is recommended during the early post-operative period after mechanical heart valve implantation.

Accelerated healing of cardiovascular textiles promoted by an RGD peptide

Polytetrafluoroethylene (PTFE) and polyethylene terephthalate (Dacron polyester) fabrics are used extensively in cardiovascular devices, e.g. heart valve sewing cuffs and vascular prostheses. While devices containing these fabrics are generally successful, it is recognized that fabrics cause complications prior to tissue ingrowth due to their thrombogenic nature. A surface active synthetic peptide, called PepTite Coating (PepTite), which was modeled after the cell attachment domain of human fibronectin has been marketed as a biocompatible coating. This peptide stimulates cell attachment through the arginine-glycine-aspartic acid (RGD) sequence. Modification of medical implants with PepTite has been shown to promote ingrowth of surrounding cells into the material leading to better tissue integration, reduced inflammation and reduced fibrotic encapsulation. In this study, polyester and PTFE textiles were modified with PepTite. The effectiveness of this coating in enhancing wound healing was investigated in a simple vascular and cardiac valve model. Our results indicate that the RGD-containing peptide, PepTite, promoted the formation of an endothelial-like cell layer on both polyester and PTFE vascular patches in the dog model. PepTite was also found to promote the formation of a significantly thinner neointima (pannus) on polyester as compared to that on its uncoated control. These results were corroborated in the cardiac valve model in which a greater amount of thin pannus and less thrombus were seen on coated polyester sewing cuffs than on control uncoated cuffs. This research shows the promising tissue response to RGD coated textiles and the potential role of this peptide in material passivation via accelerated healing.

Comparative biophysical study of adsorbed calf serum, fetal bovine serum and mussel adhesive protein films

Varying concentrations of different sera and adhesive agents are routinely used to increase cellular attachment to substrata. The surface-chemical effects of some of these surface-altering materials have been examined using ellipsometry, contact angle analysis and multiple-attenuated internal reflection infrared (MAIR-IR) spectroscopy. Specifically, 15% fetal bovine serum (FBS), Ham's F-12 (containing 10% FBS + 1% penicillin/streptomycin), 10% calf serum and mussel adhesive protein (MAP) were allowed to adsorb on to similar and different surfaces and then compared. Each of these preparations is capable of altering the surface-chemical properties of substrata with varying resultant surface energies. It is therefore important to characterize serum in the proper concentrations on the substrata under consideration in order to understand the interfacial effects.

Neovascularization of surface demineralized dentin

Uneventful healing of the wound site created by periodontal reconstructive surgery is crucial for the long term survival of the dentition. Wound healing has been shown to be initiated and mediated by matrix components and polypeptide growth factors. Neovascularization (or angiogenesis) is one of the most important events in the healing process of a wound site. Any increase in the degree and/or rate of neovascularization could result in more rapid or complete healing. Previously, we have shown that basic fibroblast growth factor (bFGF) selectively enhances periodontal ligament cell migration and proliferation. In addition, we have shown that FGF stimulates human umbilical vein endothelial cell migration and proliferation. In this study we examined whether human umbilical vein endothelial cells could be influenced to form capillary-like structures in a type I collagen stroma and on dentin surfaces in response to fibroblast growth factor (FGF). We observed tubule-like structures formed from a monolayer of endothelial cells within a type I collagen sponge in response to a gradient of FGF. Furthermore, we observed tubule-like structures formed from self-association of individual endothelial cells on partially demineralized dentin surfaces in response to FGF. Proliferation of human endothelial cells on dentin was dose dependent and maximally stimulated at a concentration of 10 ng/ml FGF. These data indicate that FGF can induce endothelial cell migration, proliferation and tubule formation on dentin.

Repopulation of dentin surfaces by periodontal ligament cells and endothelial cells. Effect of basic fibroblast growth factor

The regeneration of connective tissue attachment is a major goal of clinical periodontics. Recent investigations on biochemically mediated periodontal regeneration have attempted to define the various biological response modifiers which may provide a mechanism for periodontal regeneration. Fibronectin and endothelial cell growth factor have been shown to selectively enhance periodontal ligament (PDL) cell adhesion, migration, and proliferation. In addition, dentin preconditioned with tetracycline HCl (TTC) or citric acid (CA) supports PDL cell adhesion, presumably by exposing collagen fibers. We have now extended these studies to include basic fibroblast growth factor (b-FGF) as a potential meditor of periodontal regeneration. Using AFSCM (assays for specific cell migration), b-FGF in concentrations as low as 10 ng per dentin block significantly stimulated PDL cell chemotaxis, while the antibody against b-FGF inhibited both the chemotactic and proliferative characteristics of the mitogen. We also found that 5 ng and above of b-FGF per dentin block significantly stimulated human endothelial cell migration and proliferation. Using 125I-b-FGF, we demonstrated that the factor binds to native dentin. This binding was increased when the dentin blocks were preconditioned by TTC or CA and reduced when the dentin was subsequently treated with collagenase. 125I-b-FGF also bound with moderate affinity to a type I collagen affinity column whereas the binding to a hydroxylapatite affinity column was negligible. The combination of FN and b-FGF was a marginally more potent chemo-attractant than b-FGF alone for PDL cells.(ABSTRACT TRUNCATED AT 250 WORDS)