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Full-Text Articles in Medicine and Health Sciences
Introduction, Charles L. Baird Jr.
Introduction, Charles L. Baird Jr.
MCV/Q, Medical College of Virginia Quarterly
This issue of the Medical College of Virginia Quarterly is devoted to the publication of the proceedings of the Cardiac Arrhythmias Symposium held at the Cavalier Hotel in Virginia Beach, Virginia from June 8-10, 1972. The reason for such emphasis upon the field of cardiac arrhythmias is primarily due to the fact that there has been an awakened interest in recent years in the problem of sudden death. It is now being appreciated that a significant number of deaths attributed to cardiovascular disease are due to cardiac arrhythmias, a potentially correctable disorder.
Introduction To The Phasic Effects Of The Vagus On Sinoatrial And Atrioventricular Nodes, Gordon Moe
Introduction To The Phasic Effects Of The Vagus On Sinoatrial And Atrioventricular Nodes, Gordon Moe
MCV/Q, Medical College of Virginia Quarterly
I want to emphasize that the vagus has effects upon both the sinus node and the A-V node. It slows sinus discharge, and it depresses, delays, or blocks atrioventricular transmission. It is also known that under certain conditions that discharge of vagal fibers to the heart may be phasic. From the physiological standpoint, it ought to be phasic, particularly at slow heart rates. The reason it should be phasic is that when the systolic pulse wave arrives at the baroreceptor regions of the aorta and of the carotid sinuses, it elicits a discharge of afferent fibers in those regions which …
Electrophysiology Of Concealed Conduction, E. Neil Moore
Electrophysiology Of Concealed Conduction, E. Neil Moore
MCV/Q, Medical College of Virginia Quarterly
Several figures are presented here to demonstrate the different mechanisms of concealed conduction in which microelectrodes were used to record from the A-V node and His-Purkinje system together with simultaneously recorded atrial and ventricular electrograms. Of course, in a standard ECG, one would not be able to determine what was occurring within the specialized A-V conduction system, since only the information provided by the atrial and ventricular electrograms (P wave and QRS complex) would be available for interpretation.
Clinical Significance Of Exit Block, Irany M. De Azevedo, Yoshio Watanabe, Leonard S. Dreifus
Clinical Significance Of Exit Block, Irany M. De Azevedo, Yoshio Watanabe, Leonard S. Dreifus
MCV/Q, Medical College of Virginia Quarterly
Clinical features of exit block were shown and its probable electrophysiological mechanisms discussed. Based on recent electrophysiological studies, it is emphasized that exit block is a result of depressed conduction surrounding the ectopic pacemaker.
Ventricular Tachyarrhythmias, Borys Surawicz
Ventricular Tachyarrhythmias, Borys Surawicz
MCV/Q, Medical College of Virginia Quarterly
The mechanisms of ventricular tachyarrhythmias fall into two broad categories of increased automaticity and reentry. It is usually difficult to differentiate clinically between the two mechanisms; however, I plan to discuss certain approaches that may be helpful in this regard.
Workshop Presided By William A. Dickinson, Jr., William A. Dickinson Jr.
Workshop Presided By William A. Dickinson, Jr., William A. Dickinson Jr.
MCV/Q, Medical College of Virginia Quarterly
Workshop presided by William A. Dickinson, Jr. Transcript of three cases that were discussed.
The Gouaux-Ashman Phenomenon: His Bundle Recordings, Benjamin J. Scherlag
The Gouaux-Ashman Phenomenon: His Bundle Recordings, Benjamin J. Scherlag
MCV/Q, Medical College of Virginia Quarterly
In conclusion, it is important to state the use of His bundle-electrocardiography in differentiating supraventricular beats with aberration from ventricular beats requires a critical approach to the interpretations of deflections appearing in the P-R segment. The use of quantitative rather than qualitative tests is essential when only the His bundle recording is used as opposed to the simultaneously recorded activity from the proximal bundle branches. In some cases, His bundle pacing may be helpful in reproducing spontaneously occurring aberrant patterns.
The Pharmacology And Clinical Use Of Lidocaine And Procainamide, J. Thomas Bigger Jr., Elsa-Grace V. Giardina
The Pharmacology And Clinical Use Of Lidocaine And Procainamide, J. Thomas Bigger Jr., Elsa-Grace V. Giardina
MCV/Q, Medical College of Virginia Quarterly
Both procainamide and lidocaine are useful for acutely treating cardiac arrhythmias, and procainamide can be useful in chronic antiarrhythmic regimens. Successful management of cardiac arrhythmias requires knowledge of: 1) the mechanism and natural history of the arrhythmia, 2) the physiologic state of the patient, and 3) the cardiac effects, pharmacodynamics, and general pharmacology of the antiarrhythmic drugs.
Recent Studies In The Pre-Excitation Syndrome, E. Neil Moore
Recent Studies In The Pre-Excitation Syndrome, E. Neil Moore
MCV/Q, Medical College of Virginia Quarterly
The Wolff-Parkinson-White syndrome has held an unusual fascination for cardiologists ever since its original description in 1930. Over 60 different theories have been postulated to describe the mechanism of pre-excitation. The recent development of epicardial mapping techniques to define the sequence of ventricular activation, and the introduction of His bundle electrocardiography have provided valuable procedures for studying pre-excitation. This presentation will discuss some of the insights into the mechanism of pre-excitation that have been derived from these two electrophysiological procedures.
Conducting Pathways Of The Human Heart, Fergus O'M. Shiel, Fabio Gutierrez
Conducting Pathways Of The Human Heart, Fergus O'M. Shiel, Fabio Gutierrez
MCV/Q, Medical College of Virginia Quarterly
For over a century the cardiac beat has been experimentally observed and analyzed. To a surprising degree the relevancy of the early researches persists, and the views of the 19th century investigators though modified, have not been eclipsed by time. It may, therefore, be appropriate to preface this clinicopharmacological seminar on arrhythmias by a brief review of the cardiac conducting pathways whose existence is generally accepted today and to retrace the concepts which led to their discovery.
The Critical Use Of The His Bundle Electrogram, Benjamin J. Scherlag
The Critical Use Of The His Bundle Electrogram, Benjamin J. Scherlag
MCV/Q, Medical College of Virginia Quarterly
The technique for electrode catheter recording of consistent and stable His bundle activity presently used in the clinical laboratory was initially developed as an investigational tool. In the clinical laboratory, the His bundle electrogram, in conjunction with the surface electrocardiogram--a technique that has been termed His bundle-electrocardiography by Castellano--has provided a more accurate means of localizing the site of conduction abnormality in patients with various forms of heart block. In addition, this technique has been utilized to study various physiological and pharmacological interventions, arrhythmias, and the Wolff-Parkinson-White syndrome.
Pharmacology Of Antiarrhythmics: Quinidine, Beta-Blockers, Diphenylhydantoin, Bretylium, Albert J. Wasserman, Jack D. Proctor
Pharmacology Of Antiarrhythmics: Quinidine, Beta-Blockers, Diphenylhydantoin, Bretylium, Albert J. Wasserman, Jack D. Proctor
MCV/Q, Medical College of Virginia Quarterly
The electrophysiologic effects of the antiarrhythmic drugs, presented elsewhere in this symposium, form only one of the bases for the selection of a therapeutic agent in any given clinical situation. The final choice depends on the following factors: 1. The specific arrhythmia; 2. Underlying heart disease, if any; 3. The degree of compromise of the circulation, if any; 4. The etiology of the arrhythmia; 5. The efficacy of the drug for that arrhythmia; 6. The toxicity of the drug, especially in the given patient with possible alterations in volume of distribution, biotransformation, and excretion; 7. The electrophysiologic effects of the …
Neural Effects On Cardiac Rate And Rhythm, H. Page Mauck Jr.
Neural Effects On Cardiac Rate And Rhythm, H. Page Mauck Jr.
MCV/Q, Medical College of Virginia Quarterly
The importance of autonomic discharge emanating from high neural regions rostral to the medulla oblongata on heart rhythm was first recognized in the classical studies by Schiff and Danilewsky during the late nineteenth century. Only in the last two decades, however, has a precise description of these neural effects on heart rhythm become possible. Crucial to these more recent advances have been improvements in technology which have permitted application of discrete electrical stimuli to various regions of the brain as well as continuous monitoring of heart rate and arterial pressure. These studies, reported here, represent a portion of a broader …
Mechanisms Of Supraventricular Tachycardia, Benjamin J. Scherlag, Ralph Lazzara
Mechanisms Of Supraventricular Tachycardia, Benjamin J. Scherlag, Ralph Lazzara
MCV/Q, Medical College of Virginia Quarterly
In summary, we have found a close association between the stress of A-V nodal conduction and the occurrence of atrial dispersion or aberration. We could not explain atrial dispersion on the basis of incomplete recovery of atrial activity, slowing of atrial conduction, or the occurrence of atrial fusion. We postulate that the phenomenon of dispersion of atrial activation is related to the functional dissociation within the A-V node seen during situations which stress A-V conduction. This phenomenon may represent a mechanism whereby a second area of "turnaround" other than the A-V node is involved in reentry atrial tachyarrhythmias. Indeed, such …
Microelectrode And His Bundle Studies On Type I And Ii Second Degree A-V Block, E. Neil Moore, Joseph F. Spear
Microelectrode And His Bundle Studies On Type I And Ii Second Degree A-V Block, E. Neil Moore, Joseph F. Spear
MCV/Q, Medical College of Virginia Quarterly
Mobitz classified second degree A-V block into two categories. Mobitz type I, or Wenckebach block, is characterized by a gradual prolongation of the P-R interval preceding the dropped ventricular beat. In Mobitz type II block, the dropped beat occurs without preceding prolongation of the P-R interval. Bundle branch block usually is present in patients with Mobitz type II block. The importance of distinguishing between these two types of A-V block lies in the usual irreversibility and higher mortality of patients with type II A-V block, as contrasted with type I or Wenckebach block. Also, Mobitz type II block frequently progresses …
Reentry, Gordon Moe
Reentry, Gordon Moe
MCV/Q, Medical College of Virginia Quarterly
There are two ways in which impulses can be generated: one is by the spontaneous discharge of a pacemaker cell in either the normal site or a subsidiary site, and the other is by reentry. The concept of reentry is a very old one postulated by clinical cardiologists many years before its demonstration.
Mechanisms Of A-V Block, Leonard S. Dreifus, Joseph Mcmenamin, Demetris Kimbiris
Mechanisms Of A-V Block, Leonard S. Dreifus, Joseph Mcmenamin, Demetris Kimbiris
MCV/Q, Medical College of Virginia Quarterly
Determination of the varieties of A-V block is predicated on the precise identification of the site(s) of conduction delay as prognosis, and therapy must follow on this basis. Further electrophysiologic and pharmacologic studies will undoubtedly reveal other mechanisms on the nature of A-V transmission.
The Evolution Of Sinoatrial Node Function In Man, J. Thomas Bigger, Harold C. Strauss
The Evolution Of Sinoatrial Node Function In Man, J. Thomas Bigger, Harold C. Strauss
MCV/Q, Medical College of Virginia Quarterly
The function of the sinoatrial node is complex. In nearly all hearts, this small bit of tissue is responsible for spontaneously generating the impulse which will be distributed to the remainder of the heart, maintaining coordinated electrical and mechanical function. In recent years, it has become clear that S-A node dysfunction is not rare, can cause disabling symptoms, and often presents difficult management problems. The challenges presented by the "Sick Sinus Syndromes" have increased our desire to know more about normal S-A node function and about function in disease states.
Some Mechanisms Of Supraventricular Tachycardia, Gordon Moe
Some Mechanisms Of Supraventricular Tachycardia, Gordon Moe
MCV/Q, Medical College of Virginia Quarterly
Reciprocal rhythm was proposed about 30 years ago by Barker, Wilson, and Johnston as a probable mechanism for the explanation of supraventricular tachycardia. They proposed, on the basis of approximately 100 clinical records at the University of Michigan Hospital, that reentry through the A-V node, better known as reciprocal tachycardia, would account for approximately 40% of their cases. They also postulated that reentry through the S-A node might account for another 40%, and that 20% were probably due to ectopic foci. Ectopic focal activity is demonstrable in the laboratory, and it probably happens in man. Reentry or reciprocal activity through …