Leo Schamroth

ANNULAR SUBVALVULAR LEFT VENTRICULAR ANEURYSMS IN THE SOUTH AFRICAN BANTU.

The clinical, radiologic, morbid anatomic, and histologic features of six cases of annular subvalvular left ventricular aneurysms occurring in African subjects are described. The problems of surgical repair are emphasized and the possibilities of antemortem diagnosis discussed.

Intermittent Ventricular Parasystole with Observations on Its Relationship to Extrasystolic Bigeminy

Abstract 1. 1. Two cases of intermittent parasystole are described in which there is alternate extrasystolic and parasystolic impulse formation from the same focus; transitions between the two rhythms are repeatedly observed. 2. 2. It seems that intermittence results when the parasystolic focus is subjected to the enhancing effect of the sinus discharge whereby the automatic beat is prematurely precipitated, thus becoming a forced beat. 3. 3. This phenomenon can be explained on the basis of a property of automatic centers; namely, that their resting potentials exhibit a gradual upward “slope” of depolarization. With critical timing, the terminal part of the “slope” (i.e. its near threshold level) may encounter the enhancing effect of the preceding sinus beat and thus be precipitated prematurely. 4. 4. It is suggested that the form of extrasystolic bigeminal rhythm described may constitute a link between parasystolic and extrasystolic rhythm.

The localization of bypass tracts in the Wolff-Parkinson-White syndrome from the surface electrocardiogram.

The bypass tracts of the WFW syndrome may be situated anywhere along the AV ring. Accurate localization of such tracts has in the past been largely effected by electrophysiologic studies, particularly epicardial mapping. During recent years, however, criteria for localization of the bypass tracts from the conventional 12-lead ECG have become increasingly apparent. The preceding presentation constitutes a review and state of the art governing these rapidly developing diagnostic principles.

The clinical use of intravenous verapamil

The mechanisms of action and clinical application of verapamil--a calcium ion antagonist--are reviewed. Verapamil is effective and has important application in the treatment of coronary artery spasm, hypertensive crises, and supraventricular tachyarrhythmias.

Supernormal phase of atrioventricular conduction: Association with second degree ventricular-ectopic block∗

Abstract An electrocardiogram revealing the supernormal phase of atrioventricular conduction is described. The phenomenon is manifested as a small period of A-V conductivity during complete A-V block. The presence of ectopic-ventricular escape intervals following conducted sinus impulses enables calculations that revealed the presence of second degree entrance (V-E) block into a ventricular escape focus.

Modulated ventricular parasystole as a mechanism for concealed bigeminy

Concealed extrasystolic ventricular bigeminy reflects a distributional pattern of ventricular extrasystoles where intervening sinus beats are always in odd numbers. This has been explained on bigeminal rhythm associated with exit block. This presentation reflects a modification of this concept in that the distributional pattern may be explained on the basis of complex concealed modulation of ventricular parasystole, the concealment being due to impulses falling within the refractory period rather than suffering true exit block.

Electrocardiographic Effects of Eyeball Compression

Abstract The electrocardiographic effects of eyeball compression were studied in 148 subjects comprising (1) 102 patients with cardiac disease; (2) 18 patients with noncardiac disease; (3) 28 nurses as normal controls. The principal changes elicited by this maneuver were a general depressive effect on cardiac rhythm and the precipitation of ectopic rhythms (coupled ectopic beats, A-V dissociation, auricular and ventricular tachycardia, and intermittent parasystole). The incidence of the precipitation of ectopic rhythms was significantly greater in those patients receiving digitalis. The possible role of vagal action in the ectopic arrhythmias is discussed.

The effect of pregnancy on the frontal plane QRS axis

The electrical axis of the heart is an important parameter in electrocardiographic assessment. Slight degrees of left axis deviation have been attributed to a horizontal heart position resulting from the mechanical effects of abdominal distension, such as the physiological event of pregnancy. This study was undertaken to establish the validity of this concept.

Supernormal modulation of ventricular parasystole: The triphasic phase-response curve

Modulation of ventricular parasystole by sinus beats has been shown both in vitro and in vivo to result in a classic biphasic phase-response curve. The first clinical presentation of 3 cases of supernormal modulation of ventricular parasystole resulting in a triphasic phase response curve is reported. Supernormal modulation reflects an unexpected early enhancement expedition of the ectopic ventricular impulses. An alternative explantation for the triphasic phase-response curve is the discharge and resetting of the parasystolic focus by critically timed sinus impulses.

Intermittent venticular bigeminy as an expression of modulated parasystole

posterior chest diameter. Chest width and body weight correlate with transthoracic resistance and may explain the higher pacing thresholds in these patients.6 In general, we easily determined the appearance of pacing capture by simultaneous observation of the oscilloscope and palpation of the femoral pulse. Difficulty arose when the patient’s intrinsic heart rate was similar to the maximal pacing rate of the device. This problem could have been avoided if a pacing rate higher than 90 beats/min had been available. In summary, prophylactic external pacing may provide a safe, effective alternative to prophylactic transvenous pacing in patients who are considered to be at risk of bradycardia after cardioversion of atria1 tachyarrhythmias. Acknowledgment: We thank Maureen Adams and Belinda Anderson for assistance in the preparation of this manuscript. References