Parasystole due to re-entry as the possible mechanism of ventricular parasystole with second-degree entrance block.

BACKGROUND: In 1974, Kinoshita reported a case of 'irregular parasystole' due to type I second-degree entrance block. Since then, many cases of such 'irregular' parasystole have been reported by us. To explain the mechanism of 'irregular' parasystole, two theories have been suggested, namely, 'electrotonic modulation' by Jalife and Moe, and 'type I second-degree entrance block' by us. On the contrary, in 1960, Kinoshita et al. reported a case of concealed bigeminy for the first time. The electrocardiographic findings in concealed bigeminy have suggested that there are dual re-entrant pathways with markedly long effective refractory periods in the re-entrant pathway. We have suggested that parasystole may be caused by re-entry in such re-entrant pathways. In this article, attempts are made to explain the mechanism of all the electrocardiographic findings in our cases of parasystole by 'parasystole due to re-entry'. METHODS: Using 24 studies on parasystole and 21 studies on concealed extrasystoles that we have reported over 50 years, as well as three exemplary cases in this article, attempts are made to explain all electrocardiographic findings in parasystole by 'parasystole due to re-entry'. CONCLUSIONS: The electrocardiographic findings in our previous clinical cases of parasystole and concealed extrasystoles, as well as exemplary cases and diagrams in the present article, strongly suggest 'parasystole due to re-entry' as the mechanism of ventricular parasystole with second-degree entrance block.

Atrial parasystole in left ventricular noncompaction: a morphofunctional study by echocardiography and magnetic resonance imaging.

Isolated left ventricular noncompaction is a recently recognized age-independent cardiac genetic disorder caused by heterogeneous defects in endo-myocardial morphogenesis. Transthoracic echocardiography and cardiac magnetic resonance are the most reliable techniques to make a diagnosis of the disease, noninvasively. Arrhythmic atrial and ventricular disorders have been reported in 20-50% of these patients. The morphological and functional findings are described in a young woman in whom the exclusive clinical sign of isolated ventricular noncompaction was an atrial parasystole.

Apparent disappearance of ventricular parasystole due to a marked difference between the long form and the short form of the ectopic cycles.

Electrocardiograms were taken from a 44-year-old man with irregular ventricular parasystole in whom pure parasystolic cycles without any intervening nonectopic QRS complexes were found. When a sinus impulse fell late in the parasystolic cycle, it hastened occurrence of the next parasystolic discharge. This suggested that type I second degree entrance block occurred in the re-entrant pathway containing the parasystolic focus. When a sinus impulse fell early in the parasystolic cycle, it delayed occurrence of the next parasystolic discharge. This suggested that electrotonic modulation occurred in the parasystolic focus. As a result, the difference in length between the short form and the long form of the parasystolic cycle became markedly great. When the length of two adjacent sinus cycles ranged between the short and the long parasystolic cycle, manifest parasystolic QRS complexes disappeared for a long time. In true ventricular parasystole with pure ectopic cycles, such long disappearance has never been reported before.

His-bundle parasystole masquerading as exercise-induced 2:1 atrioventricular block.

We describe a case of symptomatic pseudo-AV block due to His-bundle parasystole masquerading as exercise-induced 2:1 AV block. Electrophysiologic study revealed the presence of His-bundle parasystole, and the fluctuation of parasystolic cycle length could be explained by the concept of modulated parasystole. Modulated parasystole is a possible explanation for maintenance of stable 2:1 AV conduction at an atrial rate of specific range during exercise.

Asymptomatic temporary atrioventricular dissociation complicating meningococcal meningitis.

We present a case of a young man with meningococcal meningitis and various asymptomatic temporary ECG abnormalities, including sinus bradycardia, atrioventricular dissociation and non specific ST-T changes.

[The clinical efficacy of verapamil in ventricular extrasystolic arrhythmia and parasystole]. / Klinicheskaia éffektivnost' verapamila pri zheludochkovoi ékstrasistolicheskoi aritmii i parasistolii.

An arrhythmogenic mechanism has been investigated pharmacologically by acute drug tests (ADT) and alternate block of slow calcium channels and fast sodium channels of the cellular membranes. ADT with verapamil reduced extrasystoles by 60% in 44% of patients demonstrating the predominance of calcium-dependent arrhythmogenesis. An antiarrhythmic efficacy of fast sodium channels blockers was ascertained in 33% of the patients. ADT with rhythmilen and verapamil produced a satisfactory antiarrhythmic effect in 18% of the examinees. These patients seem to have parallel activation of both fast sodium and slow calcium channels. They received courses of both drugs. It is stated that a pharmacological analysis of extrasystolic arrhythmia allows inference on pathogenesis of myocytic electrolyte disturbances which serves the basis for adequate corrective therapy.