Continuous Rhythm Research Articles

Evaluation of warning arrhythmias before paroxysmal ventricular tachycardia during acute myocardial infarction in man.

In order to determine the relationship of paroxysmal ventricular tachycardia (PVT) to any antecedent (premonitory) ventricular arrhythmias during the early phases of acute myocardial infarctions, 24-hour Holter monitoring was begun on 52 male patients an average of 12.6 hours after the onset of prolonged chest pain that was documented as acute infraction. Twenty-four patients had PVT and 28 did not. We analyzed in detail the incidence of frequency of premature ventricular complexes (PVCs), prematurity and pairing during the 10 minutes immediately preceding PVT from a continuous 10-minute rhythm strip. There was no positive correlation between PVT and the number or complexity of PVCs in the 10 minutes immediately before ventricular tachycardia. These findings suggest that there is no consistent pattern or frequency of ventricular arrhythmia that could be identified as premonitory for PVT during the immediate pre-PVT period, even during the acute phase of myocardial infarction in man.

Hypoxia Acclimation in Carp—How It Affects O2Uptake, Ventilation, and O2Extraction from Water

The O2 uptake (), gill ventilation () and O2 extraction from the ventilatory current were studied in carp acclimated to well-aerated water (oxygen partial pressure of inspired water > 120 mm Hg) or hypoxic water ( ≃ 30 mm Hg) for 4 wk or more. Gill ventilation was measured directly on unrestrained fish using an electromagnetic flow technique giving pulsatile stroke flows and breathing frequency. Exhaled water for analysis and calculation of O₂ extraction was obtained from a specially constructed mask allowing sampling of mixed, exhaled water. The technique results in higher values for O₂ extraction than typically reported for fish. The rates for the two acclimation groups showed higher values for the normoxia-acclimated fish correlating with a higher spontaneous activity level when compared at the conditions of acclimation. When both groups were compared in hypoxic water the converse prevailed. Thus the at water 10–30 mm Hg was 30%–40% higher in fish previously acclimated to hypoxic water. Normoxia-acclimated fish in high water have a periodic breathing which changes to a continuous rhythm in hypoxic water. In high averaged 195 ml·kg−1·min−1 rising to 1,122 ml·kg−1·min−1 in hypoxic water. Hypoxia-acclimated fish had similar values in high water but smaller ones in hypoxic water (799 ml·kg−1·min−1). Percentage O2 extraction was very high in both groups (~80), but notably hypoxia-acclimated fish extracted 85% in hypoxic water as opposed to 72% of normoxia-acclimated carp. The relative importance of ventilation and gill diffusion capacity in maintaining O2 transport in hypoxia and the importance of hypoxia-acclimation are discussed.

Periodic behavioral changes during hippocampal theta rhythm elicited by septal stimulation in rats

The influence of an electrical stimulation of the medial septum on the electroencephologram of the dorsal hippocampus and behavior was studied in freely moving rats. A short stimulation at 4–12 Hz frequency always induced orienting behavior (searching, rearing, sniffing, exploration) as soon as hippocampal rhythmic slow activity, or theta rhythm is elicited. An increase in stimulation intensity or in pulse duration led to an increased occurrence of theta rhythm and likewise, to an increase of orienting behavior. Both the theta rhythm and orienting behavior were dependent on the stimulation frequency. During long-lasting septal stimulation at 7 Hz, which elicited a continuous hippocampal theta rhythm, periodic behavioral changes were observed, consisting of orienting behavior alternating with grooming behavior (cleaning, washing, licking, scratching). These rhythmic periods lasted for 3–5 min. The significance of the rhythmic behavioral changes are discussed in relation to the activity of the cholinergic septohippocampal system and to rapid-eye-movement sleep and memory consolidation.

Occipital 3-4/s-Rhythms in Childhood EEG

Report of follow-up studies in 65 children with occipital slow rhythms in the EEG (287 records). Two types of occipital rhythms can be differentiated: Paroxysmal bursts of 3--4/s-rhythms with high amplitude (I) accentuated by closing eyes and continuous usually regular occipital 3--4/s-rhythms (II). Type I is identical with the sinusoidal occipital 3/s-rhythms, which are observed especially frequently in childhood epilepsies. It could be demonstrated by follow-up studies, that the phenomenon usually disappears at latest during puberty. --The second type may also disappear during puberty or may even persist until the adult age. This persisting type is identical with what is quoted as "Grundrhythmusvariante" in the German literature. The continuous occipital rhythms could be demonstrated at earliest at age 3. The rhythms change their shape, amplitude, frequency and localisation during growth: In children prior to age 10 the rhythms show more often occipital accentuation in monopolar leads (against ear as reference); the amplitudes are higher on average; the frequency is often less than 4/s, and alpha groups preceding the rhythms after closing the eyes are less pronounced than in older children. Subharmonic waves are frequent. In the same manner as in adults a mostly right sided lateralisation can be seen. Genetic factors may be involved in the development of the occipital rhythms, although a simple mendelian transmission could not be confirmed. The EEG phenomenon is correlated with symptoms of psychic and vegetative lability. There is no correlation to epilepsy. The high incidence of anamnestic risk factors suggests that exogenous factors are at least contributing to the development of the rhythms. The continuous occipital 3--4/s-rhythms must be understood as the symptom of a disturbed development of central pacemaker systems. It can lead to persisting abnormalities or only occur transitorily in certain stages of the brain maturation.

The optic nerve mediates the circadian pigment migration in the median eyes of the scorpion

1. 1. The peripheral visual pathway from the median eyes of the scorpion Androctonus australis was interrupted at different points and the effect on the circadian rhythm of median-eye sensitivity was examined. 2. 2. Any interruption of the visual pathway distal to the supraesophageal ganglion abolishes the circadian sensitivity rhythm in the median eyes. This rhythm is thus controlled by efferents in the optic nerve (very probably via the neurosecretory axons) rather than by way of the hemolymph. 3. 3. Following transection of the optic nerve, the sensitivity of the median eyes proceeds rapidly to the daytime state. This condition is associated with movement of the screening pigment into the distal ends of the visual cells. 4. 4. The oscillator system controlling the circadian pigment migration in the median eye cannot be located in the eye itself, but must lie in the CNS, proximal to the first optic ganglion. The oscillator itself need not be connected to both median eyes in order to function normally, as revealed by the continued rhythm in the contralateral eye following unilateral optic nerve section.

Simultaneous but separate intermittent and continuous ventricular parasystole

A 19 year old female with end-stage biventricular congestive cardiomyopathy and digitalis toxicity demonstrated double ventricular parasystole with separate but simultaneous intermittent and continuous parasystolic rhythms. The intermittent parasystolic focus, left ventricular in origin, showed failure of entrance block when conducted beats followed its ectopic beats at a critical compensatory interval. Each new parasystolic series was coupled to this interrupting conducted beat at an interval equaling the parasystolic cycle length. Even numbers of conducted beats intervened between ectopic beats during intermittency and odd numbers during uninterrupted parasystole. The mechanism of intermittency was explained by a concealed ventricular tachycardia with 3 3n1 exit block with the demonstration of occasional 3 3n2 Wenckebach exit block within a parasystolic interectopic interval. A second continuous parasystolic rhythm, right ventricular in origin, occurred at a later time without altering the first intermittent parasystolic rhythm. A 4% parallel and proportionate lengthening of both the sinus node and intermittent parasystolic cycle lengths was shown at an even later time.

New observations on the effects of atropine on the sinoatrial and atrioventricular nodes in man

Previous observations of slowing of the heart rate after administration of atropine in doses smaller than 0.4 mg and recent reports of development of rhythm disorders in patients with acute myocardial infarction given atropine prompted us to evaluate systematically the effects of various doses of atropine (0.1 to 0.8 mg) on the response of the sinoatrial (S-A) and atrioventricular (A-V) nodes in healthy volunteers. The response of the S-A node to atropine was characteristically bimodal, slowing at smaller doses and accelerating at larger doses. In contrast, the A-V node showed acceleration of conduction in response to all doses of atropine used. A hypothesis based on current understanding of the electrophysiologic parameters governing impulse formation and impulse conduction is advanced to explain the apparent paradox in the S-A and A-V nodal responses to small doses of atropine. The results suggest the need for caution and continuous rhythm monitoring when giving atropine to patients with acute myocardial infarction.

Concealed Extrasystolic Ventricular Bigeminy with Interpolation

The first reported case of concealed extrasystolic ventricular bigeminy with interpolation is described. This arrhythmia is characterized by the presence of both interpolated ventricular extrasystolic beats and a presumed persistent and continuous bigeminal ectopic rhythm with exit block. The distributional pattern of sinus conducted beats in the present case conforms to a formula defining this unusual disorder of rhythm, while the appearance of manifest ectopic beats follows the rule of bigeminy.

Effects of glutamate on spontaneous electrical activity in the embryonic chick cerebrum

In the developing chick embryo, the spontaneous hyperstriatal bioelectric activity has been recorded, quantitatively evaluated, and compared with the activity resulting from injections of sodium l-glutamate. At 15–16 days of incubation, an electrical pattern could be elicited by this substance which mimics the pattern normally appearing later in ontogeny. The most prominent feature of this response is a succession of stereotyped biphasic potentials of high amplitude, gradually increasing in frequency until they approximate a continuous rhythm which, in fact, closely resembles the slow waves seen during sleep after hatching. The cerebral glutamate concentration associated with this precocious electrical pattern approaches the level found normally at 18–19 days of incubation, viz., when the slow potentials attain their mature rhythmic appearance. Moreover, since the rise in the level of this amino acid during normal ontogeny also closely parallels the electrophysiological changes, it is concluded that glutamate might, in fact, be involved in regulating the timecourse of functional brain development in this species.

The electrocorticogram in the chronic cerveau isolé cat

1. 1. The ECoG of cerveau isolé preparations was studied in 16 high mesencephalic, chronic cats which survived for an average of 48 days. Relationships were sought between ECoG and the level of behavioral arousal and with the electrical activity at the brain-stem caudal to the transection. 2. 2. In the acute stage, two ECoG patterns could be distinguished: spindle bursts or discontinuous slow waves; and continuous, high voltage slow activity. In chronicity, this pre-collicular forebrain exhibited low voltage, fast desynchronized rhythms (ECD) which lasted for several hours and which were similar to the ECD patterns of an intact cat. 3. 3. Periods (mean duration 60 ± 4 min) of high voltage, continuous slow synchronized rhythms (ECS) alternated with ECD in the chronic preparation. These cyclical lapses exhibited electrocortical synchronization; i.e., sleep period (ECSP), which closely resembled the ECoG of slow sleep in the normal cat. 4. 4. Since both ECD and ECS persisted following visual and olfactory deafferentation of the cerveau isolé, both patterns probably have an autochthonous origin in the structures of the rostral forebrain. 5. 5. Olfactory stimulation desynchronized the ECoG according to the stage of the ECSP during which stimulation was presented. Maximal desynchronization was observed during the onset stage of the ECSP. 6. 6. The EEG patterns of the cerveau isolé showed no systematic relationship with the level of arousal of the animal, nor with the electrical activity in the brain-stem. However, the effect of nociceptive and proprioceptive stimulation revealed the possibility of an extraneural pathway which affected the ECoG of the isolated cerebrum. 7. 7. The possibility of the existence in the forebrain of the cat of an autochthonous tonic, mechanism capable of independently evoking a cyclic alternation between wakefulness and slow sleep is discussed.

Various mechanisms in reciprocal rhythm

Three cases which exhibit the rare phenomenon of reciprocal rhythm are analyzed and described in detail. Extraordinarily rare and partially unknown features were encountered. These consisted of tachycardia due to continuous reciprocal rhythm, of tachycardia caused by interpolated reciprocal beats with and without eliciting auricular contraction, of the occurrence of reciprocal rhythm in sinus rhythm and in A-V nodal rhythm with first-degree A-V block, of discharge of the nodal pacemaker by blocked reciprocal beats, and of allorhythmia due to the effect of reciprocal beats on sequential beats. In addition, a hitherto unreported disturbance of conduction is described; namely, the occurrence of a disturbance in the course of the reciprocal pathway which results in late discharge of the A-V nodal pacemaker. A short tracing of another patient, taken during a Blalock-Taussig operation, is shown which demonstrates pseudoreciprocal and reciprocal rhythm. The literature is reviewed, and diagrams illustrating the mechanism involved in various types of reciprocal beating, as encountered both in the literature and in our own cases, are shown and discussed in detail.