Frederick A. Ehlert

Robotically assisted left ventricular epicardial lead implantation for biventricular pacing

OBJECTIVES Ventricular resynchronization might be achieved in a minimally invasive fashion using a robotically assisted, direct left ventricular (LV) epicardial approach. BACKGROUND Approximately 10% of patients undergoing biventricular pacemaker insertion have a failure of coronary sinus (CS) cannulation. Rescue therapy for these patients currently is limited to standard open surgical techniques. METHODS Ten patients with congestive heart failure (New York Heart Association class 3.4 +/- 0.5) and a widened QRS complex (184 +/- 31 ms) underwent robotic LV lead placement after failed CS cannulation. Mean patient age was 71 +/- 12 years, LV ejection fraction (EF) was 12 +/- 6%, and LV end-diastolic diameter was 7.1 +/- 1.3 cm. Three patients had previous cardiac surgery, and five patients had a prior device implanted. RESULTS Nineteen epicardial leads were successfully placed on the posterobasal surface of the LV. Intraoperative lead threshold was 1.0 +/- 0.5 V at 0.5 ms, R-wave was 18.6 +/- 8.6 mV, and impedance was 1,143 +/- 261 ohms at 0.5 V. Complications included an intraoperative LV injury and a postoperative pneumonia. Improvements in exercise tolerance (8 of 10 patients), EF (19 +/- 13%, p = 0.04), and QRS duration (152 +/- 21 ms, p = 0.006) have been noted at three to six months follow-up. Lead thresholds have remained unchanged (2.1 +/- 1.4 V at 0.5 ms, p = NS), and a significant drop in impedance (310 +/- 59 ohms, p < 0.001) has been measured. CONCLUSIONS Robotic LV lead placement is an effective and novel technique which can be used for ventricular resynchronization therapy in patients with no other minimally invasive options for biventricular pacing.

Radiofrequency catheter ablation of atrial flutter: Procedural success and long-term outcome

The objective of this study was to describe the procedural success and clinical recurrences after radiofrequency catheter ablation of atrial flutter. A deflectable catheter with a 4 or 5 mm tip was positioned in the posterior right atrium. Radiofrequency energy was delivered sequentially from the tricuspid annulus to the inferior vena cava. Catheter ablation during 18 sessions for 16 patients resulted in abrupt atrial flutter termination and noninducibility in all patients. Successful sites were near the os of the coronary sinus but had no distinguishing electrographic features. During a follow-up period of 8 +/- 5 months, 4 (25%) patients had recurrence of atrial flutter; 3 of 4 underwent successful repeat ablation. By actuarial analysis, 87% of patients remained in normal sinus rhythm 6 months after the initial procedure. The only distinguishing feature of those with recurrence compared with those whose sinus rhythm was maintained was the induction of nonclinical atrial arrhythmia (50% vs 0%, respectively; p < 0.05). One patient had resolution of presumed tachycardia-related cardiomyopathy. Catheter ablation by an anatomic approach was highly successful in terminating type 1 atrial flutter and was associated with good long-term response. This technique may represent a meaningful alternative for restoration and maintenance of normal sinus rhythm. However, further investigation is warranted to define its clinical role fully.

Follow-Up of Patients with Unexplained Syncope and Inducible Ventricular Tachyarrhythmias: Analysis of the AVID Registry and an AVID Substudy

Unexplained Syncope in AVID. Introduction: A prospective registry and substudy were conducted in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Study to clarify the prognosis and recurrent event rate, risk factors, and impact of implantable cardioverter defibrillator (ICD) therapy in patients with unexplained syncope, structural heart disease, and inducible ventricular tachyarrhythmias.

Cellular and Pathophysiological Mechanisms of Ventricular Arrhythmias in Acute Ischemia and Infarction

Ventricular arrhythmias in the setting of acute myocardial ischemia and infarction remain a serious health problem because of their sudden and unpredictable nature and their potentially grave results. Electrophysiological changes that may be responsible for these arrhythmias have been described in cardiac cells and in ischemic tissue. Experimental models have played a major role in elucidating the diversity of potential mechanisms for these arrhythmias. Increases in extracellular K+, the presence of toxic metabolites, and the accumulation of catecholamines in ischemic tissue all appear to have a role in arrhythmogenesis. The autonomic nervous system also appears to play a major role in these arrhythmias. With increased understanding of the pathophysiology underlying these arrhythmias, prevention can be enhanced and therapy can be better targeted.

Immediate and Short‐Term Reproducibility of the P Wave Signal‐Averaged Electrocardiogram

While abnormalities in the P wave SAECG have been associated with the occurrence of AF, its reproducibility has never been documented. The purpose of this study was to evaluate the immediate and short‐term reproducibility of measurements from the P wave SAECG. P wave SAECGs were obtained using well‐described techniques that utilize the QHS complex as the trigger and the P wave as template for averaging. In 28 subjects (8 controls, 11 with cardiac disease, 9 with prior AF), 3 P wave SAECGs were obtained: an initial study; an immediate reacquisition; and reacquisition after 4–5 days. Vector duration and RMS voltage of the terminal 20 ms of the P wave SAECG were measured and compared. The mean P wave duration was 152 ± 14 ms on initial SAECG, 152 ± 14 ms and 152 ± 15 ms at immediate and short‐term reacquisitions, respectively (both P = NS vs initial). The mean terminal BMS voltage was 6.4 ± 6.0 mcV on initial SAECG, 6.4 ± 5.9 mcV and 6.5 ± 5.8 meV at immediate and short‐term reacquisitions, respectively (both P = NS vs initial). Linear regression analysis showed high reproducibility for both P wave duration (r = 0.94 for immediate and r = 0.96 for short‐term reacquisition vs initial) but slightly less for terminal RMS voltage (r = 0.92 for immediate and r = 0.84 for short‐term reacquisition vs initial). In subgroup analysis, P wave duration measurements were highly reproducible in controls, in subjects with cardiac disease, and in those with a history of AF. P wave duration was also reproducible for both males and females, as well as for subjects age > 65 years (r = 0.96 and 0.89 for immediate and short‐term reacquisition, respectively). Terminal RMS voltage measurements were reproducible for controls, but less reproducible in other subgroups. In conclusion, P wave duration measurements on SAEGG are reproducible when evaluated at immediate and short‐term reacquisition regardless of age, sex, cardiac disease, or prior AF. Terminal RMS voltages were less reproducible, especially in patients with cardiac disease and/or prior AF. These findings may explain conflicting observations regarding the clinical utility of terminal P wave measurements.

The P wave signal-averaged ECG

The P wave signal-averaged electrocardiogram is designed to predict the development of atrial fibrillation. This review will discuss the methodology and summarize the published experience with the P wave signal-averaged electrocardiogram.

Risk Factors for the Development of Postoperative Atrial Fibrillation

Atrial fibrillation (AF) is a frequent event following cardiac surgery, occurring in up to 40% of patients [1-5]. The arrhythmia itself is often benign such that its occurrence is sometimes not labeled as a “complication” even so, postoperative AF is associated with an increased length of hospital stay following cardiac surgery. In addition, the sequellae of postoperative AF can be severe and even life-threatening including hemodynamic compromise and thromboemboli. As such, a thorough knowledge of the risk factors associated with the development of the arrhythmia is warranted. Furthermore, it is essential that this understanding include the underlying mechanisms by which these risk factors predispose, and to seek prevention and early treatment of postoperative AF.