PubMed Health⌕ Search

Biomedical subjects

G Konishi

Publications and source records attributed to G Konishi.

At least 19 recordsLinked to original sources
PubMed1995

Bradycardia- and tachycardia-dependent termination of ventricular bigeminy: mechanism of ventricular extrasystoles with fixed coupling.

Fourteen men with intermittent ventricular bigeminy were selected for this study because coupling intervals of the extrasystoles were considerably long and usually fixed, and bradycardia-dependent (10 cases) and/or tachycardia-dependent (12 cases) termination of bigeminy occurred. In all cases, when the heart rate ranged between two certain values, ventricular bigeminy with fixed-coupled extrasystoles was sustained. In all cases showing bradycardia-dependent termination, bigeminy was suddenly terminated with no changes in coupling of the preceding extrasystoles when the heart rate was decreased below a certain lower value. In all cases showing tachycardia-dependent termination except one, when the heart rate increased beyond a certain higher value, coupling intervals gradually lengthened until bigeminy was terminated. These findings strongly suggest the possibility that, in a considerably large number of clinical cases, ventricular extrasystoles with fixed coupling are caused by longitudinal dissociation of conduction in the reentrant pathway of extrasystoles.

Adult↗
PubMed1995

Paroxysmal supraventricular tachycardia initiated by ventricular couplets in concealed ventricular trigeminy.

A case report of a man with ventricular concealed trigeminy in whom ventricular couplets initiating paroxysmal supraventricular tachycardia were occasionally seen is reported. This is the first report on concealed trigeminy with couplets. This strengthens the authors' previous suggestion that supernormal conduction may occur in the reentrant pathway of extrasystoles, as a mechanism of ventricular couplets.

Cardiac Complexes, Premature↗
PubMed1994

Differentiation between parasystole and extrasystoles. Influence of vagal stimulation on parasystolic impulse formation.

Recently, it has been shown that when a sinus impulse falls late in the parasystolic cycle, it usually hastens the next ectopic discharge. Thus, in many cases, the classic criteria for the diagnosis of parasystole (ie, varying coupling intervals and constant shortest interectopic intervals) cannot be used. To differentiate between parasystole and extrasystoles in such cases, the influence of vagal stimulation on parasystolic impulse formation was investigated in seven cases of "true" parasystole in which one or more "pure" ectopic cycles without any intervening nonectopic QRS complexes were found spontaneously. In all cases pure ectopic cycles were found during sinus arrest caused by vagal stimulation; namely, none of the cases showed extreme prolongation of the parasystolic cycle. These results strongly suggest that instead of the classic criteria, vagal stimulation causing temporary sinus arrest is the optimal method for differentiation between parasystole and extrasystoles in cases without spontaneous pure ectopic cycles.

Adult↗
PubMed1993

Female surgeons in the 1990s. Academic role models.

As part of a larger survey of the membership of the Association of Women Surgeons, data were collected to characterize the participation of women in academic surgery and surgical education. Of the 1500 members, 676 (45%) responded, and 318 of these respondents held a faculty appointment. Two hundred thirty-nine of the respondents' practices were based in a university or university-affiliated hospital. This sample was biased toward more academically motivated, upwardly mobile surgeons. Two hundred thirty-six of the respondents believed policies relating to tenure are unfair to women. Four hundred fifty-three respondents reported having role models at some point in their career, half of whom were men. However, only 204 still had access to role models or mentors at the time of the survey. Six hundred thirty respondents believed that female medical students need successful female surgeons as role models.

Adult↗
PubMed1992

Differentiation between parasystole and reentry in concealed bigeminy.

There are two different theories to explain the mechanism of concealed bigeminy: one is '2:1 concealed reentry'; the other is 'irregular parasystole.' Two exemplary cases of the even-number variant of concealed bigeminy are presented. In case 1, the mechanism can be explained by an irregular parasystole due to a modulated parasystole; however, findings during temporary sinus arrest caused by vagal stimulation indicate that this case is not governed by a parasystole, but by a 2:1 concealed reentry. In case 2, the mechanism can be explained by a 2:1 concealed reentry without parasystole; however, findings during temporary sinus arrest indicate that this case is governed by an irregular parasystole due to a type-I second-degree entrance block. Thus, in cases of concealed bigeminy without pure ectopic cycles, it does not seem easy to explain the mechanism of concealed bigeminy on the theory of a modulated parasystole.

Adult↗
PubMed1992

Mechanism of bradycardia-dependent appearance of manifest extrasystoles in concealed bigeminy. A theoretical model derived from the concepts of longitudinal dissociation and multilevel block in the reentrant pathway of extrasystoles.

A case of bradycardia-dependent appearance of manifest extrasystoles in concealed bigeminy is presented. To explain the mechanism of such bradycardia-dependent appearance, a theoretical model is derived from the concepts of "longitudinal dissociation" and "multilevel block" in the reentrant pathway of extrasystoles. In the theoretical model, functional longitudinal dissociation divides the reentrant pathway into dual pathways F and S. When manifest extrasystoles are not found for a long time, alternate sinus impulses pass through both pathways F and S, but become concealed extrasystoles because of insufficient conduction delay in the pathways. The other alternate sinus impulses are blocked in the pathways; in pathway F, the impulses are blocked at the entrance, while in pathway S, the impulses are blocked at a more distal level. When sinus cycles gradually lengthen, one of such alternate sinus impulses passes through the entrance of pathway F and, traveling very slowly, is blocked at a more distal level. The next sinus impulse is blocked at the entrance of pathway F; namely, 3:2 Wenckebach block occurs at the entrance of pathway F. Thus this sinus impulse enters only pathway S and passes through pathway S with enough conduction delay to become a manifest reentrant extrasystole.

Bradycardia↗
PubMed1990

Mechanism of ventricular extrasystoles with fixed coupling. A theoretical model derived from the concept of longitudinal dissociation in the reentrant pathway of extrasystoles.

An electrocardiogram taken from a 29-year-old man with old myocardial infarction is presented as an exemplary case of ventricular extrasystoles with fixed coupling. To explain the mechanism of ventricular extrasystoles with fixed coupling, a theoretical model is derived from the concept of longitudinal dissociation in the reentrant pathway. In the model, functional longitudinal dissociation divides the reentrant pathway into dual pathways F and S. When a sinus impulse is blocked in pathway F and passes only through pathway S, it becomes a manifest reentrant extrasystole because of marked conduction delay in pathway S. When the sinus rate does not exceed a certain value, such an impulse always becomes a manifest extrasystole with fixed coupling. Part of the impulse passing through pathway S enters pathway. F retrogradely. In some cases, thereafter, it reenters pathway S and initiates ventricular reentrant tachycardia. When, on the other hand, a sinus impulse passes through both of pathways F and S, it becomes a concealed reentrant extrasystole because of insufficient conduction delay in the pathways.

Adult↗
PubMed1990

Intermittent ventricular bigeminy as an expression of two-level Wenckebach periodicity in the reentrant pathway of extrasystoles.

A patient with intermittent ventricular bigeminy is reported in whom the presence of two-level Wenckebach periodicity in the reentrant pathway of extra-systoles is suggested. When sinus arrest was caused by vagal stimulation, no ectopic QRS complex occurred. This indicated that ventricular bigeminy was not parasystolic bigeminy but ordinary extrasystolic bigeminy. Observations of the electrocardiogram suggested that Wenckebach block occurred at two different levels in the reentrant pathway of ventricular extrasystoles. When extrasystoles were noninterpolated, Wenckebach block occurred at the distal level of the pathway and caused termination of ventricular bigeminy. On the other hand, when extrasystoles were interpolated, Wenckebach block occurred at the proximal level of the pathway. This is the first report to suggest the presence of two-level Wenckebach periodicity in a reentrant pathway of extrasystoles.

Adult↗
PubMed1990

Protection of the ventricular parasystolic focus due to interference of sinus and parasystolic impulses in the ventricular-ectopic junction.

A 50-year-old man with intermittent ventricular parasystolic bigeminy is reported in whom the parasystolic focus was protected from late intervening sinus impulses. This is the first report to suggest the presence of protection due to interference in parasystolic bigeminy. The findings in this case suggest that when a sinus impulse falls in a late period of the parasystolic cycle, it travells so slowly along the ventricular-ectopic junction that it is unable to reach the parasystolic focus before the spontaneous occurrence of the next parasystolic impulse; as a result, the sinus impulse interferes with the next parasystolic impulse in the ventricular-ectopic junction. Thus it is suggested that the parasystolic focus is protected from the sinus impulse because of the interference and not because of an entrance block. This reinforces the concept of a second-degree entrance block as a mechanism of parasystole.

Arrhythmias, Cardiac↗
PubMed1990

'Stereovectorcardiogram' made by stereolithography.

A method for making directly a single solid vectorcardiogram is reported. A solid vectorcardiogram was made by employing an apparatus for production of three-dimensional objects by stereolithography. Stereolithography is a computer-aided manufacturing technique that is practiced in conjunction with computer-aided design and engineering. To design the solid vectorcardiogram, voltages in the X, Y and Z axes obtained according to the Frank lead are memorized in the computer-aided design system. By use of the stereolithography apparatus, the designed solid vectorcardiogram is formed in a vat filled with liquid plastic. In the vat, the plastic changes rapidly from liquid to solid in the presence of ultraviolet light so that a solid vectorcardiogram made of solid plastic may be formed.

Equipment Design↗
PubMed1990

Mechanism of intermittent preexcitation in the Wolff-Parkinson-White syndrome. The concept of electronically mediated conduction across an inexcitable gap.

A man with intermittent preexcitation in the Wolff-Parkinson-White syndrome is reported. Once a sinus impulse was blocked in the accessory pathway, the block (ie, loss of preexcitation) was continued for a while until a PP interval reached or exceeded a critical period inducing sudden reappearance of preexcitation. This critical period was considerably longer than the effective refractory period of the accessory pathway. These findings are explained by the use of the concept of electronically mediated conduction across an inexcitable gap in the accessory pathway. It seems that when loss of protection was maintained, the sinus impulse was blocked at the site proximal to the gap, but the impulse passing through the atrioventricular node always reached retrogradely the site distal to the gap, and therefore, the next sinus impulse was blocked again.

Adult↗