Intramural conduction system gradients and electrogram regularity during ventricular fibrillation.

Introduction: The His-Purkinje system has been shown to harbor triggers for ventricular fibrillation (VF) initiation. However, the substrate responsible for VF maintenance remains elusive. We hypothesized that standard, electrode-based, point-to-point mapping would yield meaningful insight into site-specific patterns and organization which may shed light on the critical substrate for maintenance of VF.

Feasibility of directional percutaneous epicardial ablation with a partially insulated catheter.

Purpose: To demonstrate the feasibility of directional percutaneous epicardial ablation using a partially insulated catheter.

Methods: Partially insulated catheter prototypes were tested in 12 (6 canine, 6 porcine) animal studies in two centers. Prototypes had interspersed windows to enable visualization of epicardial structures with ultrasound.

Evaluation of a Unique Defibrillation Unit with Dual-Vector Biphasic Waveform Capabilities: Towards a Miniaturized Defibrillator.

Background: Automated external defibrillators can provide life-saving therapies to treat ventricular fibrillation. We developed a prototype unit that can deliver a unique shock waveform produced by four independent capacitors that is delivered through two shock vectors, with the rationale of providing more robust shock pathways during emergent defibrillation. We describe the initial testing and feasibility of this unique defibrillation unit, features of which may enable downsizing of current defibrillator devices.

Percutaneous Epicardial Pacing using a Novel Insulated Multi-electrode Lead.

Introduction: Epicardial cardiac resynchronization therapy (CRT) permits unrestricted electrode positioning. However, this requires surgical placement of device leads and the risk of unwanted phrenic nerve stimulation. We hypothesized that shielded electrodes can capture myocardium without extracardiac stimulation.

Novel Techniques in Epilepsy Management: Venous Pacing and Capture of Electrical Activity in the Primate Cortex.

Objective: Pharmacotherapy for epilepsy is limited with 30% of patients refractory to this approach of suppressing seizures. Current surgical options are invasive and carry significant morbidities including infection, bleeding, and the potential for deleterious neurocognitive effects. As a result, there is a burgeoning need for innovation to develop safer and efficacious interventions.

Blood Pressure Responses to Endovascular Stimulation: A Potential Therapy for Autonomic Disorders With Vasodilatation.

Background: We have previously shown that sympathetic ganglia stimulation via the renal vein rapidly increases blood pressure. This study further investigated the optimal target sites and effective energy levels for stimulation of the renal vasculatures and nearby sympathetic ganglia for rapid increase in blood pressure.

Methods: The pre-study protocol for endovascular stimulations included 2 minutes of stimulation (1-150 V and 10 pulses per second) and at least 2 minutes of rest during poststimulation.

Effects of stepwise denervation of the stellate ganglion: Novel insights from an acute canine study.

Background: The stellate ganglion (SG) is important for cardiac autonomic control. SG modification is an option for treating refractory ventricular tachyarrhythmias. The optimal extent of left- and right-sided SG denervation necessary for antiarrhythmic effect, however, remains to be learned.

Novel Percutaneous Epicardial Autonomic Modulation in the Canine for Atrial Fibrillation: Results of an Efficacy and Safety Study.

Background: Endocardial ablation of atrial ganglionated plexi (GP) has been described for treatment of atrial fibrillation (AF). Our objective in this study was to develop percutaneous epicardial GP ablation in a canine model using novel energy sources and catheters.

Methods: Phase 1: The efficacy of several modalities to ablate the GP was tested in an open chest canine model (n = 10).

Direct Pulmonary Vein Ablation With Stenosis Prevention Therapy.

Introduction: The dominant location of electrical triggers for initiating atrial fibrillation (AF) originates from the muscle sleeves inside pulmonary veins (PVs). Currently, radiofrequency ablation (RFA) is performed outside of the PVs to isolate, rather than directly ablate these tissues, due to the risk of intraluminal PV stenosis.

Methods: In 4 chronic canine experiments, we performed direct PV muscle sleeve RFA ± postablation drug-coated balloon (DCB) treatment with paclitaxel/everolimus.

Percutaneous ligation of the left atrial appendage results in atrial electrical substrate modification.

Debulking of electrically active atrial tissue may reduce the mass of fibrillating tissue during atrial fibrillation, eliminate triggers, and promote maintenance of normal sinus rhythm (NSR). We investigated whether left atrial appendage (LAA) ligation results in modification of atrial electrical substrate. Healthy male mongrel dogs (N = 20) underwent percutaneous epicardial LAA ligation.

Novel balloon catheter device with pacing, ablating, electroporation, and drug-eluting capabilities for atrial fibrillation treatment--preliminary efficacy and safety studies in a canine model.

Pulmonary vein isolation is an established therapeutic procedure for symptomatic atrial fibrillation (AF). This approach involves ablation of atrial tissue just outside the pulmonary veins. However, patient outcomes are limited because of a high rate of arrhythmia recurrence.

Transvenous stimulation of the renal sympathetic nerves increases systemic blood pressure: a potential new treatment option for neurocardiogenic syncope.

Background: Neurocardiogenic syncope (NCS) is a common and sometimes debilitating disorder, with no consistently effective treatment. NCS is due to a combination of bradycardia and vasodilation leading to syncope. Although pacemaker devices have been tried in treating the bradycardic aspect of NCS, no device-based therapy exists to treat the coexistent vasodilation that occurs.

Advances in radiofrequency ablation of the cerebral cortex in primates using the venous system: Improvements for treating epilepsy with catheter ablation technology.

Background: Pharmacology frequently fails for the treatment of epilepsy. Although surgical techniques are effective, these procedures are highly invasive. We describe feasibility and efficacy of minimally invasive mapping and ablation for the treatment of epilepsy.

Compatibility of electroanatomical mapping systems with a concurrent percutaneous axial flow ventricular assist device.

Background: Hemodynamic instability hinders activation and entrainment mapping during ventricular tachycardia ablation. The Impella 2.5 microaxial flow device (MFD; Abiomed Inc.

The off-pump implantation of an apicoaortic valved graft is safe and has no negative impact on coronary flow and hemodynamics.

Objective: : To determine the hemodynamic effect of an off-pump apicoaortic valved graft (AAVG) implantation, we performed a quantitative coronary flow analysis in a swine model of severe aortic stenosis.

Methods: : In 10 swine, cardiac output, coronary flow, right common carotid artery flow, and internal mammary artery flow were measured along with left and right ventricular pressures and aortic and pulmonary artery pressures. A novel AAVG was implanted off-pump on the left ventricular (LV) apex using a specially designed implantation tool and anastomosed to the descending thoracic aorta.

Use of the aortoatrial continuity as means of providing left ventricular assist support without entering the ventricle: a feasibility study.

Background: Left ventricular assist devices (LVADs) are increasingly used to treat patients with refractory heart failure. Current-generation LVADs have major limitations, including the need for open chest surgery, limiting their widespread use. We hypothesized that the aortoatrial continuity could be used as a unique anatomic vantage point for entirely percutaneous LVAD placement.

The impact of competitive flow on distal coronary flow and on graft flow during coronary artery bypass surgery.

To determine the impact of left anterior descending-competitive flow (LAD-CF) on distal coronary flow (LAD-DF) and on left internal mammary artery-graft flow (LIMA-GF), we performed a quantitative blood-flow analysis in a swine model of a LIMA-to-LAD coronary artery bypass graft (CABG). In six swine, a LIMA-to-LAD CABG was performed. LAD blood-flow was measured bilaterally to the LIMA-to-LAD anastomosis, in the LIMA and in the pulmonary artery (cardiac output, CO) along with the LIMA pulsatility index (LIMA-PI) and the left ventricular pressure (LVP).