Identification of Ventricular Tachycardia Using Intracavitary Ventricular Electrograms: Analysis of Time and Frequency Domain Patterns

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74961/1/j.1540-8159.1988.tb06279.x.pd

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Ventricular-triggered pacemakers: clinical experience.

It is now generally agreed that the presence of symptoms is an indication for long-term pacing of patients with complete heart block, and that this treatment lowers the mortality considerably (Char-dack et al., 1966; Sowton, 1967a). An appreciable proportion of paced patients has intermittent atrioventricular conduction so that if a fixed rate pacemaker is implanted there is competition be-tween natural and artificial pacemakers. This frequently produces palpitation, sometimes causes large swings in blood pressure, and very occasionally results in dangerous ventricular arrhythmias due to stimulation within the vulnerable period (Tavel and Fisch, 1964). Competition can be avoided in several ways, one of which is the use of demand pacemakers which do not stimulate the heart unless a fixed period without spontaneous activity occurs (Parsonnet et al., 1966; Sowton, 1967b). An alternative approach, due to Neville (Neville et al., 1966), is for the pacemaker to be triggered by spon-taneous ventricular potentials and then to deliver an impulse to the ventricle immediately. This im-pulse falls ineffectively within the absolute refrac-tory period and so cannot cause a competing rhythm, nor stimulate during the vulnerable period. So long as sinus rhythm persists the pacemaker follows the ventricular rate exactly; if a spontaneous ectopic beat occurs this, too, will trigger the pacemaker so that the stimulus falls harmlessly during the refrac-tory period. If complete heart block returns, so that no spontaneous QRS complex arises during a preset time interval, the pacemaker begins to stimu-late the ventricle at a fixed rate. The time interval is directly related to the fixed pacing rate, and pacemakers of this type provide a limit below which the ventricular rate cannot fall. If conducted or ectopic beats return the pacemaker will again be immediately triggered at the spontaneous rate. The use of atrial-triggered pacemakers, whic