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At least 163 records · Page 9Linked to original sources
PubMed1982

Relationship between conductivity and functional refractoriness of atrioventricular node in man.

Eighty-one consecutive patients representing a wide clinical spectrum were studied to assess the degree of limitation of the atrial extrastimulus technique for measurement of atrioventricular node refractoriness; and, to determine the relationship between conductivity and functional refractoriness of the atrioventricular node (AVN). Four patients developed sustained atrial fibrillation and a total of 277 basic cycle lengths (BCLs) were evaluated in the remaining 77. Four different patterns of AVN conduction were defined on the basis of plots of H1H2 versus A2A2 and discontinuity in the plot was observed for some of each of the three major patterns. No functional refractory period (FRP) of AVN could be determined in 10/77 patients (13%) and in 127/277 BCLs (46%). A mathematical formula relating measurements of conductivity (A2H2 interval) to FRP which was derived from the canine heart was applied to the data for those BCLs where FRP was known. Optimal agreement between measured and calculated FRP (y = x + 3, r = 0.97, n = 38) was obtained when subsets of data were selected according to an algorithm derived from repetetive computer analysis of the parent data base. The calculation is independent of patient variables (medication, impaired AVN conduction, pattern of AVN conduction). These results demonstrate that the atrial extrastimulus technique often will not permit measurement of AVN refractoriness in the human heart but conductivity and FRP are related in a fashion similar to that determined for the canine heart. This relationship permits calculation of FRP from measurements of conductivity. Calculation of FRP is recommended for brevity and greater yield of data.

Adolescent↗
PubMed1989

[Quantitative electron microscopic research on the structure of the myocytes in the atrioventricular node and perinodal myocardium of the rat interatrial septum].

A quantitative electron microscopical examination of specialized conducting myocytes of types II and III in the atrioventricular node and working myocytes in perinodal region was performed. The volume fractions of myofibrils, mitochondria, nuclei, sarcoplasmic reticulum, glycogen, atrial granules and "clear" cytoplasm were measured, in addition to the diameters of conducting and working myocytes. These data were compared with those for conducting myocytes of types I, II, and III from sinoatrial region and internodal tracts of the rat heart, and with evidence for atrioventricular node of other animals. Principles of an universal classification of conducting myocytes of the heart are discussed.

Animals↗
PubMed2006

Twin atrioventricular node associated with interruption of the inferior vena cava and atrioventricular nodal reentrant tachycardia.

We report the case of a patient exhibiting symptomatic junctional bigeminy associated with twin atrioventricular (AV) node and an anomaly in the inferior vena cava. The patient evidenced twin AV node and complete interruption of the inferior vena cava, with azygos continuation. The catheters for mapping of the AV junctional area and ablation were accessed via jugular and subclavian venous approaches, and azygos venous approach via the femoral vein. Twin AV node was diagnosed by (1) the existence of 2 discrete non-preexcited QRS morphologies of junctional bigeminy, (2) decremental anterograde and retrograde conduction, and (3) inducible AV nodal reentrant tachycardia. Atrioventricular nodal reentrant tachycardia and bigeminal rhythm were eliminated by ablation of the retrograde pathway. The postablation rhythm was a regular junctional rhythm, without tachycardia.

Adult↗
PubMed1983

An extra atrioventricular node in an anomalous heart of a calf.

An extra atrioventricular node in a double outlet ventricle with a quite normal inflow septum in a calf is described. The anomaly resembles the topography of the conducting system in the calf heart in the embryonic stages from 13.5 mm-90 mm.

Abnormalities, Multiple↗
PubMed1987

[Ultrastructure of the sinus and atrioventricular nodes in experimental myocardial infarct].

The ultrastructure of sinus and atrioventricular nodes was studied in white rats with experimental myocardial infarction. 24 hours after the induction of the disease mitochondrial enlargement characterized by the increase in their area, decrease in the number of cristae and the decline in the rate of mitochondrial energy effectiveness was detected. Different degrees of nuclear chromatin aggregation and membrane permeability for colloidal lanthanum were observed. Characteristic types of conduction cellular lesions were revealed in experimental myocardial infarction.

Animals↗
PubMed1977

Heart block, sudden death, and atrioventricular node mesothelioma.

We report a case of mesothelioma of the atrioventricular node with congenital complete heart block and sudden death in a 15-year-old girl. This benign tumor probably represents a hamartoma derived from mesothelium with a constant anatomic location and uniform association with heart block. The clinical course of such patients, however, has been variable. The tumor has been associated with sudden, unexpected death in infancy or adolescence, but has more often been discovered as an incidental finding at autopsy in a middle-aged or elderly patient.

Adolescent↗
PubMed1979

Multilevel block in the atrioventricular node during atrial tachycardia and flutter alternating with Wenckebach phenomenon.

The electrocardiograms of 100 patients with rapid and regular PP intervals during atrial arrhythmias (because of atrial tachycardia or flutter, or pacing) were examined for periods of irregular atrioventricular conduction. This irregular conduction corresponds to an alternating Wenckebach phenomenon, of a type that can be determined from simple rules. The different types of conduction encountered in different patients and the changes seen in the same patient suggest that the atrioventricular node functions physiologically with 3 levels of sequential block. The different prevalence of the 2 types of alternating Wenckebach block may reflect functional differences at the level of the atrioventricular node.

Atrial Flutter↗
PubMed1998

New findings on the origin of the blood supply to the atrioventricular node. Clinical and surgical significance.

The anatomy of the heart's conduction system and of its blood supply have been research topics for many years. However, several proposals have never been demonstrated. In this paper, we describe 2 vascular conduits that have never before been objectively shown to supply the conduction system. Twenty human hearts from subjects aged between 15 and 65 years--with and without coronary disease--were dissected after anterograde and retrograde injection with latex butaclor E-650 by means of a technique developed by the authors. In 40% of these hearts, Kugel's artery was found to supply the atrioventricular node. The right descending superior artery supplied the atrioventricular node in 70% of the hearts dissected. These findings may be of major significance both in clinical cardiology and in cardiovascular surgery.

Adolescent↗
PubMed1978

Dissociation of the atrioventricular node in acute inferior wall myocardial infarction. 1. Transverse dissociation (alternate Wenckebach periods).

Two cases of alternate Wenckebach periods developing during the acute phase of inferior wall myocardial infarction are presented. In both cases, syncope occurred and severe bradyarrhythmia was recorded on the day of admission. Electrophysiologic study performed in one patient and a narrow QRS complex in the other patient during the alternate Wenckebach periods confirmed the atrioventricular node as the level of block. Transverse dissociation of the atrioventricular node with two (or more) levels of block is the most acceptable explanation for this phenomenon. We suggest that alternate Wenckebach periods occurring during the acute phase of inferior wall myocardial infarction is a severe bradyarrhythmia, and prophylactic temporary pacing is recommended.

Acute Disease↗
PubMed1989

[Congenital atrioventricular block and maternal lupus erythematosus. Histologic discovery of tumor of the atrioventricular node].

A case of congenital atrioventricular block in a newborn whose mother presented with systemic lupus erythematosus (SLE) is reported. Despite intensive care the child died a few hours after birth. Serial sections of the heart could be examined. Histology provided information on the appearance and distribution of the lesions. In particular, the sinus node was small for the child's age, and its supplying artery was found to have a hyperplastic media with adventitial sclerosis; the interatrial and interventricular septa showed subendocardial fibrosis invading the adjacent myocardium. Owing to the scarcity of systematic histopathological examinations, such lesions have seldom been described. In addition, a tumour of the atrioventricular node, known as mesothelioma or hemolymphangioma, was discovered. This case is exceptional in that histopathological findings similar to those described in SLE, though rarely as numerous, were associated with a very rare tumour never hitherto described in such a young patient. The relationship between the two categories of lesions is discussed.

Adult↗
PubMed1994

Radiofrequency ablation therapy in atypical or multiple atrioventricular node reentry tachycardias.

Electrophysiologic study and radiofrequency ablation therapy were performed in 23 patients with atypical (8 patients) or multiple (15) atrioventricular node reentry tachycardias. Dual pathways with anterograde fast and slow pathway conductions were demonstrated in 16 patients. Studies on retrograde conduction revealed the presence of three different pathways, including fast (15 patients), intermediate (17), and slow (16). The radiofrequency current was applied to the inferior aspect, one-third anterior two-thirds posterior between the His bundle and the ostium of the coronary sinus, of Koch's triangle along the tricuspid annulus in all patients. Application of the current resulted in selective ablation or modification of both retrograde intermediate and slow pathway conductions in 20 patients. In two patients retrograde fast pathway conduction was also modified. Complete atrioventricular block occurred in the remaining patient. Sixteen patients had no induction of tachycardia or echo, 4 had induction of a single echo, and 2 had induction of the slow-fast form tachycardia; one of those 2 patients underwent a second trial and was successful. A median application of 2 was delivered at a power of 25 +/- 5 W and a duration of 18 +/- 4 sec. The total fluoroscopic time was 25 +/- 21 minutes. The anterograde fast pathway conduction was unaffected; the shortest atrial paced cycle length that sustained 1:1 fast pathway conduction was 329 +/- 65 msec and 330 +/- 68 msec before and after ablation, respectively. A follow-up electrophysiologic study was performed in 16 patients 60 +/- 15 days after ablation. Eleven had no induction of tachycardia or echo, and five had induction of < 3 echoes. This study demonstrated that radiofrequency ablation with the inferior approach is effective and safe in atypical or multiple atrioventricular node reentry tachycardias. It resulted in ablation of the slow pathway and retrograde intermediate pathway conduction with preserved atrioventricular conduction.

Adult↗
PubMed1977

The development of innervation in the rat atrioventricular node.

The problem of development of the innervation of the rat atrioventricular node has been investigated by electron microscopy. Nerve bundles appear in relation to the node as early as the second postnatal day and vesiculated axons are seen throughout the entire node by the fourth day. Intimate contacts between nodal cells, axons and terminal varicosities are frequently observed. Use of the 5-hydroxydopamine tracer technique has enabled the identification of both cholinergic and adrenergic axons. It is concluded that the node has a dual innervation although cholinergic endings far outnumber those classified as adrenergic on the sixth postnatal day. These results are quite different to earlier findings made at the light microscope level and the discrepancies are discussed with respect to the histochemical techniques used. The suggestion that nodal differentiation is induced by nerves is considered in relation to the differences in cholinesterase activity exhibited by nodal cells during normal development and following neonatal sympathectomy.

Adrenergic Fibers↗
PubMed1976

Effect of changes in inputs to atrioventricular node on AV conduction.

The effect of different inputs into the atrioventricular node (AVN) on orthograde impulse transmission was studied. In rabbit AVN preparations, two stimulating electrodes were placed posteriorly in the crista terminalis (P) and anteriorly in the interatrial septum (A). Electric stimuli were given individually (P,A) or simultaneously (P + A). Premature stimulation, when properly timed (e.g. 70-100 msec at the basic cycle length of 400 msec) achieved AV conduction only in P + A but not in either P or A. Action potentials (APs) in AVN in this situation revealed an incomplete depolarization in P and A, but became a fullsized AP in P + A. This might be explained by summation. The site of simmation appeared to be in the upper node, because APs distal to the middle node as well as APs in the His bundle behaved in an "all or none" fashion. Time intervals between the stimulus artifact and the His bundle AP upstroke (S-H) were shorter in P + A was enhanced with the decrease of the S-H difference between P and A suggested an accelerated conduction by summation in AVN. A hyperpolarizing current flowing through the suction electrodes which were attached in the vicinity of AVN caused different amounts of S-H shortening between P and A input. The above data support the view that AVN has a summating property engendered by the slow inactivation of ionic channel on which the upstroke of AP depends and by the limited number and sites of atrial inputs which might connect with some preferential paths within the AVN.

Action Potentials↗
PubMed1984

The role of the phase relation between the atrial excitatory waves in determining the functional refractory properties of the atrioventricular node.

Through programme stimulation of the two basic inputs of the atrioventricular node (AVN)--crista terminalis and interatrial septum--different spatial and temporal relations between the excitatory waves passing from the atrium into the node were modelled in intact rabbit heart preparation. The essential role of the spatial-temporal organization for the determination of the refractory properties is demonstrated. The functional refractory curves depend not only on the basic rhythm, but also on the direction of the atrial excitation front. It is shown that interaction of the input waves is possible in intact preparation as well. At optimum phase regimes combined stimulation of the two inputs leads to prolongation or shortening of the initial H1H2 interval. The qualitative characteristic of the observed effects is very varied. It is defined predominantly by the stimulation programme, but it does not depend on which of the two inputs the basic rhythm is applied. The view is expressed that in order to obtain a more accurate characterization of the AVN-conduction, it is necessary to consider the interaction of the atrial excitatory waves arriving at the posterior and anterior inputs of AVN and the reflection of this interaction on its refractory properties.

Animals↗
PubMed1999

Characteristics of a transient outward current (sensitive to 4-aminopyridine) in Ca2+-tolerant myocytes isolated from the rabbit atrioventricular node.

A transient outward current (Ito) has been observed in the atrioventricular node (AVN), but its characteristics in Ca-tolerant AVN myocytes have not been investigated previously. In this study, Ito was measured from Ca-tolerant rabbit AVN myocytes at 37 degrees C, using the whole-cell patch-clamp technique. With interfering currents inhibited, 500-ms voltage-clamp pulses applied from -80 mV elicited Ito at potentials positive to -30 mV, which increased in magnitude with test potential amplitude. This current was completely blocked by external application of 5 mM 4-aminopyridine (4-AP). During a command pulse, Ito activated rapidly then inactivated with a bi-exponential time-course. Fast and slow time constants of current inactivation (tauf and taus, respectively) showed voltage dependence. At 0 mV, tauf was 14.5+/-2.7 ms and taus was 112.8+/-21. 2 ms, whilst at +60 mV tauf was 6.7+/-1.1 ms and taus was 63.7+/-9.2 ms (n=25). The steady-state inactivation relationship showed half-maximal inactivation at -33.8 mV (n=8). Re-activation of Ito after an inactivating pre-pulse showed a bi-exponential time-course of recovery: tau1 was 196+/-70 ms, and tau2 was 2707+/-1010 ms (n=6, at -80 mV). Repetitive application of voltage-clamp test pulses showed that Ito inactivation accumulated on repetitive stimulation, but reached a steady state rapidly for a given pulse frequency (0. 2-1.0 Hz). AVN Ito was sensitive to the class 1 anti-arrhythmic flecainide (EC50 for peak current of 24 microM), which showed selectivity for the rapidly inactivating current component. Quinidine also inhibited Ito in a dose-dependent fashion, but did not affect the current time-course. Under voltage-clamp conditions, a simulated diastolic depolarisation from -70 to -45 mV did not significantly reduce Ito amplitude, and under current-clamp conditions 4-AP inhibited spontaneous action potentials. Although this is consistent with a significant role for Ito in shaping AVN activity, under the conditions of this study 4-AP also partially blocked the "rapid" delayed rectifier current, IKr, and so the effects of 4-AP on action potentials could not be attributed exclusively to its effects on Ito.

4-Aminopyridine↗
PubMed1997

Atrioventricular node reentry: physiology and radiofrequency ablation.

Atrioventricular (AV) node reentry has been recognized as a clinical arrhythmia for many years. Earlier basic investigations identified a dual AV conduction system, and atrial echo beats occurred when the refractory period of the slow conduction pathway was shorter than the fast pathway. Subsequent studies in humans confirmed the concept of dual AV node physiology and AV node reentry. Slow-fast AV node reentry (anterograde conduction over the slow pathway and retrograde conduction over the fast pathway) occurs most frequently. The fast-slow and intermediate varieties are much less common. A high (> 95%) cure rate occurs with radiofrequency catheter ablation with experienced electrophysiologists. Most electrophysiologists prefer the posterior approach, which results in absence or very poor conduction over the slow AV node pathway: the PR interval is minimally changed. This approach is highly successful for all three forms of AV node reentry and associated with a 1%-2% incidence of heart block in most experienced laboratories.

Animals↗
PubMed2001

[An original method of demolition of re-entry tachycardia of atrioventricular node].

In 75 patients with reentry tachycardia of atrioventricular node the dotted applications were performed on the ishtmus of coronal sinus level, right from the tricuspid valve ring deep to the atrium. The ratio of amplitudes of atrial and ventricular commissures was in limits of 1:10-11:10. After each application the possibility of tachycardia occurrence was tested. It took one procedure to perform to climinate tachycardia in all the patients. The applications quantity had constituted 5.5 +/- 3.8 at average. Roentgenexposition time had constituted--(10.2 +/- 3.8) min. The atrioventricular conduction disorder was not observed. Recurrency of arrhythmia was not noted in 5 months--4 years follow-up.

Adrenergic beta-Agonists↗