1.
The Cardiac Pacemaker Clinic: Memories From a Bygone Era.
Mond, HG, Sloman, JG
Heart, lung & circulation. 2021;(2):216-224
Abstract
In 1963, soon after the first ventricular pacemakers were implanted at the Royal Melbourne Hospital, attempts were made to identify impending pacing failure, thus preventing sudden death in these very vulnerable patients. By 1970, patient numbers had increased, a formal regular pacemaker clinic was established, and guidelines and protocols developed. The clinic was staffed by a physician, a biomedical engineer and cardiac technicians. The unipolar, asynchronous, non-programmable pulse generators were powered by mercuric oxide/zinc batteries and implanted in the abdomen, using either transvenous or epimyocardial leads. Although, pulse generators were electively replaced at 3 years, most had already been replaced because of power source depletion, electronic failure or lead issues. Testing in all patients involved an electrocardiographic rhythm strip and electronic analysis of the stimulus artefact using a calibrated high-speed storage oscilloscope. Results were compared to previous studies and significant changes were interpreted as impending power source depletion. As a result of this testing, 97% of cases of impending power source depletion were detected prior to failure. These findings allowed testing each 4 months and for pulse generator life to be extended beyond three years. With ventricular triggered pulse generators, new testing procedures were designed. With time, visiting regional centres and clinical evaluation of new products became important functions of the clinic.
2.
Cardiac automaticity: basic concepts and clinical observations.
Vetulli, HM, Elizari, MV, Naccarelli, GV, Gonzalez, MD
Journal of interventional cardiac electrophysiology : an international journal of arrhythmias and pacing. 2018;(3):263-270
Abstract
PURPOSE The purpose of this report was to review the basic mechanisms underlying cardiac automaticity. Second, we describe our clinical observations related to the anatomical and functional characteristics of sinus automaticity. METHODS We first reviewed the main discoveries regarding the mechanisms responsible for cardiac automaticity. We then analyzed our clinical experience regarding the location of sinus automaticity in two unique populations: those with inappropriate sinus tachycardia and those with a dominant pacemaker located outside the crista terminalis region. RESULTS We studied 26 patients with inappropriate sinus tachycardia (age 34 ± 8 years; 21 females). Non-contact endocardial mapping (Ensite 3000, Endocardial Solutions) was performed in 19 patients and high-density contact mapping (Carto-3, Biosense Webster with PentaRay catheter) in 7 patients. The site of earliest atrial activation shifted after each RF application within and outside the crista terminalis region, indicating a wide distribution of atrial pacemaker sites. We also analyzed 11 patients with dominant pacemakers located outside the crista terminalis (age 27 ± 7 years; five females). In all patients, the rhythm was the dominant pacemaker both at rest and during exercise and located in the right atrial appendage in 6 patients, in the left atrial appendage in 4 patients, and in the mitral annulus in 1 patient. Following ablation, earliest atrial activation shifted to the region of the crista terminalis at a slower rate. CONCLUSIONS Membrane and sub-membrane mechanisms interact to generate cardiac automaticity. The present observations in patients with inappropriate sinus tachycardia and dominant pacemakers are consistent with a wide distribution of pacemaker sites within and outside the boundaries of the crista terminalis.
3.
Atrial fibrillation and congestive heart failure: risk factors, mechanisms, and treatment.
Heist, EK, Ruskin, JN
Progress in cardiovascular diseases. 2006;(4):256-69
Abstract
Atrial fibrillation (AF) and congestive heart failure (CHF) are commonly encountered together, and either condition predisposes to the other. Risk factors for AF and CHF include age, hypertension, valve disease, and myocardial infarction, as well as a variety of medical conditions and genetic variants. Congestive heart failure and AF share common mechanisms, including myocardial fibrosis and dysregulation of intracellular calcium and neuroendocrine function. Pharmacological treatments including beta-blockers, digoxin, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers can be useful in treating both of these conditions. Antiarrhythmic medications intended to achieve and maintain sinus rhythm may be beneficial in some patients with AF and CHF. Advances in pacemaker and defibrillator therapy, including cardiac resynchronization therapy, may also benefit patients with AF and CHF. Surgical and catheter-based ablation therapy can restore sinus rhythm in patients with AF, with proven benefit in patients with concommitant CHF. Investigational biologic therapy, including cell and gene based therapy, offers promise for the future of reversing the pathophysiological mechanisms that underlie AF and CHF.