Amplitude and Direction of Atrial Depolarization Using a Multipolar Floating Catheter: Principles for a Single Lead VDD Pacing

VDD stimulation using a single catheter for atrial sensing and ventricular sensing and pacing has become a reality. In order to compare the quality of the cavitary atrial electrogram (AEG) and to determine the intraatrial P wave direction and conduction time (CT), we compared, in an acute study, three different types of atrial electrode systems using four different leads, in 53 patients in sinus rhythm. The three electrode systems were: (1) one experimental system with quadripolar orthogonal electrodes using the Goldreyer concept; (2) one experimental system with quadripolar whole ring electrodes; (3) two systems with diagonally oriented half-ring electrodes, one experimental quadripolar and one bipolar CCS commercial (Polysafe A-Track lead). For the experimental systems, the four electrodes forming two independent bipolar pairs were situated on the intraatrial floating portion of a single lead and one supplemental electrode was distally positioned in the right ventricular apex. Bipolar AEGs were recorded at the high and at the low levels of the right atrium. For the CCS lead, the single bipolar AEG was recorded at the high level of the right atrium only. The highest AEG amplitude and the highest values for ventricular far-field rejection were provided by both diagonally oriented half-ring electrodes at the high atrial level and by the whole ring electrodes at the low atrial level. For both atrial levels, the orthogonal electrode system provided the smallest AEG amplitudes, the highest ventricular electrogram amplitudes, and therefore, the smallest values for ventricular far-field rejection.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bidirectional Bundle Branch Reentry Tachycardia Associated with Ebstein's Anomaly: Cured by Extensive Cryoablation of the Right Bundle Branch

A 30-year-old woman with Ebstein's anomaly presented with a sustained, wide QRS complex tachycardia exhibiting a left bundle branch block morphology. Serial electrophysiological studies revealed right and left bundle branch reentry tachycardias refractory to many conventional antiarrhyfhmic drugs, Radiofrequency and direct current catheter ablation of the right bundle branch failed to control the tachycardias. The patient subsequently underwent extensive endocardial cryoablation to the right bundle branch resulting in cure of her arrhythmia.     

ATTITUDES TOWARD SUICIDE AND SUICIDAL RISK AMONG YOUNGER AND OLDER PERSONS

Despite a burgeoning literature on some aspects of elder suicide, little is known about the specific attitudes that older people hold about suicide. The present study examined attitudes toward suicide and suicidal risk among 96 younger and 79 older adults. Participants completed the Suicide Opinion Questionnaire and the Suicide Risk Scale. Regarding suicidal risk, younger adults scored significantly higher than older adults. Regarding attitudes, older adults scored significantly higher than younger adults on 7 of 15 subscales, indicating that for older adults, suicide was more acceptable, more strongly related to a lack of religious conviction, more lethal, more normal, more irreversible or permanent, more strongly related to demographics, and more strongly related to individual aspects. An implication is that older adults hold both adaptive and maladaptive attitudes about suicide that may be useful in providing a social and cultural context to the study, prevention, and treatment of elder suicide.     

Cardiac Resynchronization Therapy Relieves Intractable Angina Due to Exercise‐Induced Left Bundle Branch Block Without Left Ventricular Systolic Dysfunction: A Detailed Case Study

Exercise‐induced left bundle branch block is rare and can be demonstrated with exercise testing. When the heart rate reaches a certain threshold, the QRS widens into left bundle branch block. This paper describes a patient with exercise‐induced left bundle branch block related angina and dyspnea, who responded to cardiac resynchronization therapy. We documented the potential benefits of cardiac resynchronization therapy with a left ventricular rapid pacing study prior to its implantation. Although exercise‐induced left bundle branch block is not a current indication for cardiac resynchronization therapy in patients such as ours, it could be considered when conventional drug therapy fails.     

Intermittent Capture of the Left Bundle With Permanent His Bundle Pacing: Mechanistic Insights and Implications for an Emerging Field

We present a case of a patient with elevated His lead capture thresholds and intermittent recruitment of the left bundle. The patient underwent a noninvasive electrophysiology study and was determined to have a left bundle branch block due to postrepolarization refractoriness. The nature of bundle branch block can have important implications for optimal patient selection and device programming in the emerging field of His bundle pacing.     

Phosphine gas poisoning

Phostoxin is a fumigant used in rural areas. We report a case of phostoxin ingestion which resulted in the release of lethal phosphine gas. The patient developed a profound metabolic acidosis and cardiovascular depression and died. During treatment and after death, he continued to emit the noxious gas which was dangerous to staff, and resulted in evacuation of the emergency department. Such events tend to be associated with myth and hysteria and the lack of ready access to reliable information. They represent a unique challenge to the emergency physician.     

External Non-invasive Cardiac Pacing: A Comparative Hemodynamic Study of Two Techniques with Conventional Endocardial Pacing

Out-of-hospital therapy for cardiac arrest due to bradyarrhythmias or asystole is pharmacologic and the outcome is uniformly dismal. Optimal therapy for the latter disturbances may be artificial cardiac pacing, but conventional invasive pacing techniques are not employed or are of limited value in the out-of-hospital and emergency department setting. This investigation compared the hemodynamic effects of two techniques of non-invasive external pacing: 1) transcutaneous transthoracic pacing (TTP) and 2) tongue-to-epigastrium pacing (TEP), with conventional transvenous right ventricular endocardial pacing (RVEP) in a closed-chest, chronic heart block canine model. All techniques significantly increased (p less than .001) cardiac output (CO). However, CO and mean arterial pressure (MAP) measured during external pacing with either non-invasive technique were significantly greater than that during RVEP (p less than .001). TEP produced vigorous skeletal muscle stimulation and, in the canine model, it produced contraction resulting in impaired ventilation, hypoxemia, and a decrease in systemic vascular resistance. TTP in this model resulted in improved MAP and CO when compared with control and RVEP values and did not affect arterial or mixed venous blood gas values. Thus, this study demonstrates that noninvasive TTP is comparable to RVEP in its hemodynamic effects. TTP may offer definitive non-invasive therapy for a subset of victims of out-of-hospital cardiac arrest.