Virtual Cohorts and Synthetic Data in Dementia: An Illustration of Their Potential to Advance Research.

When attempting to answer questions of interest, scientists often encounter hurdles that may stem from limited access to existing adequate datasets as a consequence of poor data sharing practices, constraining administrative practices. Further, when attempting to integrate data, differences in existing datasets also impose challenges that limit opportunities for data integration. As a result, the pace of scientific advancements is suboptimal. Synthetic data and virtual cohorts generated using innovative computational techniques represent an opportunity to overcome some of these limitations and consequently, to advance scientific developments. In this paper, we demonstrate the use of virtual cohorts techniques to generate a synthetic dataset that mirrors a deeply phenotyped sample of preclinical dementia research participants.

Novel mitral repair device for the treatment of severe mitral regurgitation: preclinical ovine acute and chronic implantation model.

OBJECTIVE: A project is now underway to implement a novel percutaneous mitral repair system for severe mitral regurgitation (MR). The initial phase of the project consists of proof-of-concept by testing device characteristics using open surgical implantation. When surgical proof-of-concept of the intended percutaneous design is completed, a second phase of the project will consist of in vivo testing of the percutaneous transseptal system. The device is currently being designed to fold into a 17F catheter system and to unfold within the left atrium where attachment is accomplished using a reversible anchoring system. The purpose of this study was to show functionality of the device in elimination of MR using the open surgical method. METHODS: We have performed surgical prototype device implantation in 5 acute and 7 chronic sheep preparations. We created a P2-flail model of severe (4+) MR in the 12 sheep. Via a minimally invasive left thoracotomy incision and open repair on cardiopulmonary bypass, the device was implanted to determine efficacy of elimination of severe MR. Implantation was considered successful if 4+ regurgitation was converted to 1+ MR or lower. Left ventriculography and epicardial 2-dimensional/3-dimensional echocardiography were used to assess repair; serial 2-dimensional/3-dimensional transthoracic echocardiography was used to assess long-term mitral repair status. RESULTS: Twelve sheep had surgical creation of severe (4+) MR by cutting all chordae to the P2 scallop of the mitral valve; this preparation was tested and was found to produce 100% acute fatality without repair of the mitral valve. Five sheep had acute implantation of the device with elimination of regurgitation in 5/5 sheep. Seven sheep had chronic (1-7 month) implantation of the device. The device was tested in the chronic model for clinical status, residual regurgitation, thrombosis, and histopathology. All sheep had mitigation of MR and survived to the intended date of death. CONCLUSIONS: Proof-of-concept of a novel percutaneous mitral repair device has been completed using an ovine P2-flail severe MR model. The device has characteristics that will allow its use in posterior leaflet degenerative disease and functional/secondary MR. Open, minimally invasive, and robotic surgical implantation of the device can also be developed as an alternative to the percutaneous approach.

The variable functional effects of the pacing site in normal and scarred ventricles.

BACKGROUND: The pacing site has been shown to influence functional improvement with cardiac resynchronization therapy. We evaluated the effects of the pacing site on left ventricular (LV) function in an animal model. METHODS AND RESULTS: Equilibrium radionuclide angiography was acquired in sinus rhythm (NSR) and with ventricular pacing, from three pacing sites in seven normal and eight infarcted dogs. QRS duration, electrical activation pattern, wall motion, LV ejection fraction (EF), synchrony of ventricular contraction, and mean arterial pressure (MAP), were related to the pacing site and infarct size, during each of 120 episodes. Little changed during pacing in normals. In infarcted dogs, LV wall motion, and synchrony worsened, LVEF and MAP often fell. These changes related to altered activation patterns which were influenced by the pacing site but were not related to infarct size. CONCLUSIONS: Hemodynamic and functional LV changes after infarction were found to vary with the pacing site and associated conduction and synchrony.

Percutaneous left atrial appendage transcatheter occlusion (PLAATO system) to prevent stroke in high-risk patients with non-rheumatic atrial fibrillation: results from the international multi-center feasibility trials.

OBJECTIVES: These studies were conducted to evaluate the feasibility of percutaneous left atrial appendage (LAA) occlusion using the PLAATO system (ev3 Inc., Plymouth, Minnesota). BACKGROUND: Patients with atrial fibrillation (AF) have a five-fold increased risk for stroke. Other studies have shown that more than 90% of atrial thrombi in patients with non-rheumatic AF originate in the LAA. Transvenous closure of the LAA is a new approach in preventing embolism in these patients. METHODS: Within two prospective, multi-center trials, LAA occlusion was attempted in 111 patients (age 71 +/- 9 years). All patients had a contraindication for anticoagulation therapy and at least one additional risk factor for stroke. The primary end point was incidence of major adverse events (MAEs), a composite of stroke, cardiac or neurological death, myocardial infarction, and requirement for procedure-related cardiovascular surgery within the first month. RESULTS: Implantation was successful in 108 of 111 patients (97.3%, 95% confidence interval [CI] 92.3% to 99.4%) who underwent 113 procedures. One patient (0.9%, 95% CI 0.02% to 4.9%) experienced two MAEs within the first 30 days: need for cardiovascular surgery and in-hospital neurological death. Three other patients underwent in-hospital pericardiocentesis due to a hemopericardium. Average follow-up was 9.8 months. Two patients experienced stroke. No migration or mobile thrombus was noted on transesophageal echocardiogram at one and six months after device implantation. CONCLUSIONS: Closing the LAA using the PLAATO system is feasible and can be performed at acceptable risk. It may become an alternative in patients with AF and a contraindication for lifelong anticoagulation treatment.

An endovascular approach to cardioembolic stroke prevention in atrial fibrillation patients.

This report is of a 62-year-old woman presenting with a 3-year history of chronic atrial fibrillation (AF) and unable to tolerate chronic warfarin therapy due to bleeding episodes and unstable INR values. Additional high risk factors for stroke are a history of congestive heart failure and previous embolic stroke. Percutaneous left atrial appendage transcatheter occlusion (PLAATO ) was performed to seal the LAA. A transesophageal echocardiography (TEE) at the 1- and 6-month follow-up showed no device migration and no new thrombus related to the implant. The patient has been doing well on postprocedure aspirin with no embolic events.

Percutaneous left atrial appendage occlusion (PLAATO) for preventing cardioembolism: first experience in canine model.

BACKGROUND: Atrial fibrillation is associated with a high risk for cardioembolic stroke. The left atrial appendage (LAA) is the source of the vast majority of these thromboemboli. A novel implanted device for percutaneous LAA transcatheter occlusion (PLAATO) has been designed to seal the LAA. The purpose of this study was to test the feasibility and safety of transcatheter LAA occlusion in dogs. METHODS AND RESULTS: A PLAATO implant was delivered to the LAA through a 12F transseptal catheter in 25 dogs. The PLAATO device was repositioned until occlusion was seen, or it was recaptured and replaced with a different size. LAA sealing was confirmed by intracardiac echocardiography and contrast fluoroscopy. Follow-up was performed 2 days to 6 months after implantation. After imaging assessment, dogs were euthanized and LAA was examined for device healing, migration, perforation, and any thrombosis, both grossly and histologically. The LAA was occluded in all cases. No mobile thrombi associated with the implantation were seen. Healing on the atrial-facing surface was 90% at 1 month and was complete by 3 months, which was confirmed by gross and histological examination. Light microscopic examination of brain, kidney, and spleen showed no evidence of emboli or infarct. CONCLUSIONS: Transcatheter LAA occlusion is simple and feasible. At the follow-up study, the device remained in the LAA, with benign healing and no evidence of new thrombus or damage to surrounding structures. This new strategy may provide an alternative treatment for patients with nonvalvular atrial fibrillation who are less than optimal candidates for warfarin.

Percutaneous left atrial appendage transcatheter occlusion to prevent stroke in high-risk patients with atrial fibrillation: early clinical experience.

BACKGROUND: Thromboembolism due to atrial fibrillation (AF) is a frequent cause of stroke. More than 90% of thrombi in AF form in the left atrial appendage (LAA). Obliteration of the appendage may prevent embolic complications. METHODS AND RESULTS: We evaluated the feasibility and safety of implanting a novel device for percutaneous left atrial appendage transcatheter occlusion (PLAATO). LAA occlusion using the PLAATO system was attempted in 15 patients with chronic AF at high risk for stroke, who are poor candidates for long-term warfarin therapy. The implant consists of a self-expanding nitinol cage covered with a polymeric membrane (ePTFE). The LAA was successfully occluded in 15/15 patients (100%). Angiography and transesophageal echocardiography (TEE) during the procedure showed that the device was well-seated in all patients and that there was no evidence of perforation, device embolization, or interference with surrounding structures. In 1 patient, the first procedure was complicated by a hemopericardium, which occurred during LAA access. A second attempt 30 days later was successful with no untoward sequela. No other complications occurred. At 1-month follow-up, chest fluoroscopy and TEE revealed continued stable implant position with smooth atrial-facing surface and no evidence of thrombus. CONCLUSIONS: Thus, transcatheter closure of the LAA is feasible in humans. This novel implant technology may be appropriate for patients with AF who are not suitable candidates for anticoagulation therapy. Further trials are needed to show the long-term safety and its efficacy in reducing stroke.