David Schwartzman

Left Heart Pacing Lead Implantation Using Subxiphoid Videopericardioscopy

Introduction: Recent clinical data support the utility of left heart pacing. The transvenous approach for left heart pacing lead implantation is imperfect. A direct epicardial approach may have advantages, but heretofore its utility has been limited because of the requirement for thoracotomy. We sought to examine the feasibility of a method for epicardial lead implantation that did not require thoracotomy.

Common left pulmonary vein: A consistent source of arrhythmogenic atrial ectopy

Introduction: The discovery of a consistent relationship between atrial anatomy and electrophysiology would have practical value and may provide insight into arrhythmia mechanism. We previously observed that anatomically common left pulmonary veins were a disproportionate source of atrial ectopy that was associated with the initiation of atrial fibrillation (“arrhythmogenic”). This report details our efforts to characterize and quantify this observation.

Changes in local wall thickness correlate with pathologic lesion size following radiofrequency catheter ablation: an intracardiac echocardiographic imaging study.

Introduction: High‐resolution intracardiac echocardiographic (ICE) imaging can accurately assess wall thickness during radiofrequency (RF) catheter ablation procedures. This study investigated the correlation of changes in wall thickness at the ablation site with pathologic lesion size. Methods and Results: ICE image‐guided 31 RF applications (30–50 W, up to 120 sec) were performed in five anesthetized closed chest swine (n = 5, body weight 35–60 kg). Twenty‐four lesions were delivered in the right and left atria with standard RF; seven lesions were delivered in the left ventricle (LV) with irrigated (30–40 ml/min) RF. Wall thickness and tissue echo density measured by ICE imaging (preand 1‐minute post‐RF delivery) with increased focal echo density following RF deployment in the atria (4.5 ± 1.5 vs 2.3 ± 1.0 mm pre‐RF) and the LV (9.8 ± 2.3 vs 6.8 ± 2.2 mm pre‐RF; P < 0.01). The observed changes in wall thickness (ΔWT) following ablation in the LV were greater than in the atria (3.0 ± 1.4 vs 2.2 ± 1.2 mm; P < 0.05). A significant correlation between ΔWT and lesion depth (ventricular: r = 0.85, P < 0.05; atrial: r = 0.82, P < 0.01) was demonstrated at all ablation sites. Local wall thickness measured post‐RF also significantly correlated with lesion depth (r = 0.89, P < 0.01), especially with that of transmural lesions (r = 0.95, n = 23, P < 0.001) at atrial and LV sites. Conclusion: Therapeutic RF ablation results in mural swelling and increased echo density. These changes can be detected by ICE imaging and correlate with pathologic lesion size. ICE imaging may be useful in online quantification of lesion size, especially for transmural lesions during clinical catheter ablation procedures.

Predicting Hyperresponse Among Pacemaker-Dependent Nonischemic Cardiomyopathy Patients Upgraded to Cardiac Resynchronization

Resynchronizing Pacemaker‐Dependent Patients. Introduction: Right ventricular (RV) pacing engenders left ventricular (LV) dyssynchrony and may diminish LV systolic function, promote adverse cardiac remodeling, and foster heart failure (HF). This process may be reversible in some pacemaker‐dependent patients upgraded to cardiac resynchronization therapy (CRT). We examined the clinical characteristics of pacemaker‐dependent patients who exhibit hyperresponse (i.e., normalization of LV function) with CRT upgrade.

SERIAL DEFIBRILLATION LEAD IMPEDANCE IN PATIENTS WITH EPICARDIAL AND NONTHORACOTOMY LEAD SYSTEMS

Lead Impedance in ICDs. Introduction: The stability of implantable cardiac defibrillation lead impedance subsequent to implantation has not been reported and may have important clinical implications. The objective was to characterize the incidence and degree of impedance changes occurring after implantation of defibrillation lead systems.

Feasibility of Myxomatous Mitral Valve Repair Using Direct Leaflet and Chordal Radiofrequency Ablation

OBJECTIVE Minimally invasive repair of mitral valve prolapse (MVP) causing severe mitral regurgitation (MR) should reduce MR and have chronic durability. Our ex vivo, acute in vivo, and chronic in vivo studies suggest that direct application of radiofrequency ablation (RFA) to mitral leaflets and chordae can effect these repair goals to decrease MR. METHODS A total of seven canines were studied to assess the effects of RFA on mitral valve structure and function. RFA was applied ex vivo (n = 1), acutely in vivo using a right lateral thoracotomy and cardiopulmonary bypass (n = 3), and chronically in vivo using percutaneous access to the heart (n = 3). RFA was applied to the mitral valve and its associated chordae. Mitral valve structure and function (in vivo preparations) were then assessed. RESULTS Ex vivo application of RFA resulted in qualitative reduction in mitral leaflet surface area and chordal length. Acute in vivo application of RFA to canines found to have MVP causing severe MR demonstrated a 43.7-60.7% statistically significant (P = 0.039) reduction in postablation MR. Chronic, in vivo, percutaneous application of RFA was found to be feasible and the engendered alterations durable. CONCLUSION These data suggest that myxomatous mitral valve repair using radiofrequency energy delivered via catheter is feasible.

Determinants of first-shock success for atrial implantable cardioverter defibrillators

Atrial Defibrillation. Introduction: The aim of this study was to identify determinants of first‐shock success for defibrillation of spontaneous atrial fibrillation (AF) in ambulatory patients with an atrial implantable cardioverter defibrillator (ICD). The determinants of first‐shock success in ambulatory patients with atrial ICDs are unknown.

Insights into the Electrophysiology of Ventricular Tachycardia Gained by the Catheter Ablation Experience:.: "Learning While Burning"

VT Catheter Ablation. The success of catheter ablation has significantly improved the treatment of patients with cardiac arrhythmias and has established electrophysiology as an increasingly interventional subspecialty. Some members of the electrophysiology community have expressed concern that this success has been purchased at the cost of undermining what had been our primary concern: understanding the anatomic and physiologic basis of arrhythmia syndromes. In many laboratories, endpoints such as case load and primary success have eclipsed physiologic investigation. Despite these trends, however, catheter ablation is not inherently at odds with investigation and education. On the contrary, because the lesions delivered with current techniques are much more discrete than the effects of antiarrhythmic agents or surgical ablation, catheter ablation can be used as a research tool directed toward a more precise understanding of arrhythmia substrates. Conscious attempts at “learning while burning” have already provided important and unique information about arrhythmia pathogenesis.

Electrocardiographic Events Preceding Onset of Atrial Fibrillation: Insights Gained Using an Implantable Loop Recorder

Introduction: Previous reports demonstrate that individual patients may have distinctive electrocardiographic patterns preceding atrial fibrillation (AF) onset. However, these observations are based on single recordings, and are thus limited by their “snapshot” derivation; it is unclear whether patterns observed on these recordings are consistent over time. We hypothesized that the use of an implantable loop recorder (ILR) would be feasible for serial, long‐term characterization of electrocardiographic events preceding AF onset.

Nocturnal Peak in Atrial Tachyarrhythmia Occurrence as a Function of Arrhythmia Burden

Nocturnal Initiation of Atrial Tachyarrhythmias.