Regional distribution of ECS in contractile and conductive elements of rat and rabbit heart

1992 ◽  
Vol 263 (1) ◽  
pp. H168-H176
Author(s):  
K. G. Lurie ◽  
J. Dutton ◽  
P. Wiegn
Keyword(s):  
Regional Differences ◽  
Regional Distribution ◽  
Rabbit Heart ◽  
Conduction System ◽  
Cardiac Conduction ◽  
Ventricular Muscle ◽  
Av Node ◽  
His Bundle ◽  
Ventricular Tissue ◽  
Left And Right

By adaptation of recently developed quantitative microanalytic techniques, the size of the extracellular space (ECS) was measured regionally in the rat and rabbit cardiac conductive and contractile tissues. When inulin and sucrose were measured as extracellular markers in rabbit heart, the ECS in the atrioventricular (AV) node was found to be, respectively, 2.4 and 2.2 times larger than that of adjacent ventricular muscle. By use of inulin, the ECS in the rabbit His bundle was found to be 1.8 times larger than the adjacent ventricular tissue. Similarly, when inulin was used in rat, the ECS of the AV node, His bundle, right bundle branch, and right atrium was found to be, respectively, 2.5, 1.9, 1.8, and 1.2 times larger than that of left and right ventricular muscle. Similarly, significant regional differences in ECS were also observed in rat heart with sucrose. By use of glucose as an ECS marker, these results also revealed a 2.5-2.9 times larger ECS in rat and rabbit AV node compared with contractile elements. In contrast, ATP content, measured as an intracellular marker, was the same in both AV nodal and ventricular muscle tissue from both rat and rabbit. These data demonstrate that there are significant regional variations in ECS within the cardiac conduction system. Collectively, the data obtained with all extracellular markers indicate that the size of the ECS of the conduction system is markedly larger than the adjacent contractile muscle.

Effect of disopyramide and disobutamide on conduction in perfused rabbit hearts

1981 ◽  
Vol 59 (11) ◽  
pp. 1192-1195
Author(s):  
Peter E. Dresel ◽  
Keith D. Cameron
Keyword(s):  
Antiarrhythmic Agent ◽  
Conduction System ◽  
Atrioventricular Conduction ◽  
Cardiac Conduction ◽  
Conduction Time ◽  
Related Effect ◽  
Av Node ◽  
His Bundle ◽  
Time Changes ◽  
His Bundle Recording

The effects of disopyramide (DP) and a new antiarrhythmic agent, disobutamide (DB) on cardiac conduction were studied using His bundle recording from modified rabbit Langendorff preparations electrically driven at 3 and 4 Hz. Both disopyramide (4–16 μg/mL) and disobutamide (1–30 μg/ml) slowed conduction throughout the atrioventricular conduction system, i.e., SA, AH, and HV intervals were increased in a dose-related manner. Conversion of the conduction time changes to percent changes indicates that disobutamide has a relatively equal effect on each part of the system whereas disopyramide exhibited significantly less effect on AV nodal conduction. Slowing of conduction in the AV node by DP was clearly related to rate. Changes in SA and HV intervals were rate related to a lesser degree. No such rate-related effect was evident with disobutamide. Block of atrial conduction occurred in two out of six hearts when the rate was increased at 8 μg/mL of DP and in three additional hearts at 16 μg/mL. This was interpreted to indicate a change in atrial excitability such that 2 × threshold currents no longer excited the tissues. This was not observed at any concentration of DB.

Electrophysiology and anatomy of embryonic rabbit hearts before and after septation

2005 ◽  
Vol 288 (1) ◽  
pp. H344-H351 ◽  
Author(s):  
F. Rothenberg ◽  
V. P. Nikolski ◽  
M. Watanabe ◽  
I. R. Efimov
Keyword(s):  
High Resolution ◽  
Optical Mapping ◽  
Immunohistochemical Analysis ◽  
Rabbit Heart ◽  
Conduction System ◽  
Cardiac Conduction ◽  
Adult Rabbit ◽  
Before And After ◽  
Ventricular Activation ◽  
Activation Sequence

Mechanisms of cardiac pacemaking and conduction system (CPCS) development are difficult to study, in part because of the absence of models that are physiologically similar to humans in which we can label the entire CPCS. Investigations of the adult rabbit heart have provided insight into normal and abnormal cardiac conduction. The adult and the embryonic rabbit have an endogenous marker of the entire cardiac conduction system, neurofilament 160 (NF-160). Previous work suggested that ventricular septation correlates with critical phases in avian CPCS development, in contrast to the mouse CPCS. Combining high-resolution optical mapping with immunohistochemical analysis of the embryonic rabbit heart, we investigated the significance of ventricular septation in patterning the rabbit embryonic conduction system. We hypothesized that 1) completion of ventricular septation does not correlate with changes in the ventricular activation sequence in rabbit embryos and 2) CPCS anatomy determines the activation sequence of the embryonic heart. We found that preseptated ( days 11–13, n = 13) and postseptated (day 15, n = 5) hearts had similar “apex-to-base” ventricular excitation. PR intervals were not significantly different in either group. CPCS anatomy revealed continuity of the NF-160-positive tract connecting the presumptive sinoatrial node, atrioventricular (AV) junction, and ventricular conduction system. The presence of collagen in the AV junction coincided with the appearance of an AV interval. We conclude that the apex-to-base ventricular activation sequence in the rabbit embryo is present before completion of ventricular septation. CPCS anatomy reflects global cardiac activation as demonstrated by high-resolution optical mapping.

Rate-dependent AV nodal refractoriness: a new functional framework based on concurrent effects of basic and pretest cycle length

2009 ◽  
Vol 297 (6) ◽  
pp. H2136-H2143 ◽  
Author(s):  
Rafik Tadros ◽  
Jacques Billette
Keyword(s):  
Refractory Period ◽  
Cycle Length ◽  
Rabbit Heart ◽  
Combined Effects ◽  
Av Node ◽  
His Bundle ◽  
Rate Dependent ◽  
Supraventricular Tachyarrhythmias ◽  
Induced Changes ◽  
Fast Rates

The atrioventricular (AV) node filters atrial impulses. Underlying rate-dependent refractory properties are assessed with the effective (ERPN; longest nonconducted atrial cycle length) and functional (FRPN; shortest His bundle cycle) refractory period determined with premature protocols at different basic rates. Fast rates prolong ERPN and shorten FRPN, but these effects vary with subjects, age, and species. We propose that these opposite and variable effects reflect the net sum of concurrent cumulative and noncumulative effects associated with basic (BCL) and pretest cycle length (PTCL), respectively. To test this hypothesis, we assessed selective and combined effects of five BCL (S1S1) and six PTCL (S1S2) on ERPN, FRPN, and their subintervals (ERPN = A2H2 + H2A3 and FRPN = H2A3 + A3H3, where A is atrium and H is His bundle) with S1S2S3 protocols in six rabbit heart preparations. At control BCL, PTCL shortenings prolonged ERPN (113 ± 12 vs. 101 ± 14 ms, P < 0.01) as a net result of prolonged A2H2 and curtailed H2A3. At control PTCL, BCL shortenings increased ERPN (127 ± 20 vs. 101 ± 14 ms, P < 0.01) by prolonging A2H2. FRPN did not vary with BCL but decreased (163 ± 6 vs. 175 ± 10 ms, P < 0.01) with PTCL that curtailed H2A3. Equal BCL and PTCL shortenings as in standard protocols prolonged ERPN but left FRPN unchanged. Notably, ERPN and FRPN significantly correlated through their H2A3 subinterval. In conclusion, BCL and PTCL are both important determinants of AV nodal refractoriness and together account for rate-induced changes in ERPN and FRPN observed during standard premature protocols. ERPN and FRPN are related variables. Similar functional rules may govern nodal refractory behavior during supraventricular tachyarrhythmias.

scholarly journals Distinct circadian mechanisms govern cardiac rhythms and susceptibility to arrhythmia

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Edward A. Hayter ◽  
Sophie M. T. Wehrens ◽  
Hans P. A. Van Dongen ◽  
Alessandra Stangherlin ◽  
Shobhan Gaddameedhi ◽  
...  
Keyword(s):  
Time Of Day ◽  
Conduction System ◽  
Cardiac Conduction ◽  
Cardiac Conduction System ◽  
Daily Rhythms ◽  
Av Node ◽  
Node Activity ◽  
Circadian Control ◽  
Abrupt Shifts ◽  
The Brain

AbstractElectrical activity in the heart exhibits 24-hour rhythmicity, and potentially fatal arrhythmias are more likely to occur at specific times of day. Here, we demonstrate that circadian clocks within the brain and heart set daily rhythms in sinoatrial (SA) and atrioventricular (AV) node activity, and impose a time-of–day dependent susceptibility to ventricular arrhythmia. Critically, the balance of circadian inputs from the autonomic nervous system and cardiomyocyte clock to the SA and AV nodes differ, and this renders the cardiac conduction system sensitive to decoupling during abrupt shifts in behavioural routine and sleep-wake timing. Our findings reveal a functional segregation of circadian control across the heart’s conduction system and inherent susceptibility to arrhythmia.

scholarly journals His bundle pacing: a new look at the method

2020 ◽  
Vol 25 ◽  
pp. 4002
Author(s):  
N. A. Prikhodko ◽  
T. A. Lyubimtseva ◽  
S. V. Gureev ◽  
V. K. Lebedeva ◽  
D. S. Lebedev
Keyword(s):  
Biventricular Pacing ◽  
Conduction System ◽  
Cardiac Conduction ◽  
Lead Extraction ◽  
Clinical Anatomy ◽  
His Bundle ◽  
His Bundle Pacing ◽  
Conduction Disorders ◽  
Patients With Heart Failure ◽  
Further Development

His bundle pacing (HBP) implements physiological impulse propagation along the cardiac conduction system and can serve as an analogue of both right ventricular and biventricular pacing. This review highlights clinical anatomy issues related to HBP; the technique of lead implantation in the His position is considered. We also describe the electrophysiological basis of HBP, possibilities of lead extraction, indications for implantation, and prospects for further development of the technique. HBP is a promising direction in cardiology, which in the future may fundamentally change the algorithms for managing patients with heart failure and conduction disorders.

scholarly journals Measurement of cAMP in the cardiac conduction system of rats.

1995 ◽  
Vol 43 (6) ◽  
pp. 601-605 ◽  
Author(s):  
A Sugiyama ◽  
S McKnite ◽  
P Wiegn ◽  
K G Lurie
Keyword(s):  
Atrioventricular Node ◽  
Conduction System ◽  
Cardiac Conduction ◽  
Cardiac Conduction System ◽  
Camp Production ◽  
Adrenergic Stimulation ◽  
Beta Adrenergic ◽  
His Bundle ◽  
Freeze Dried ◽  
Camp Levels

To characterize differences in regional cAMP production in the cardiac conduction system, 18 rats were anesthetized with pentobarbital (65 mg/kg IP) and randomized into a control (n = 9) and a stimulated group (n = 9). The stimulated group received aminophylline (20 mg/kg SC) and isoproterenol (16 micrograms/kg SC). The concentration of cAMP in freeze-dried, micro dissected pieces (1-3 micrograms) of cardiac tissue was measured using a new microanalytical method. The cAMP contents in right atrium, atrioventricular node, His bundle, and left ventricle (fmol/microgram dry weight, mean +/- SE) were 38.9 +/- 2.5, 39.0 +/- 4.3, 46.4 +/- 6.1, and 41.4 +/- 3.3 in controls and 72.9 +/- 6.7, 86.1 +/- 2.9, 115.0 +/- 11.5, and 79.5 +/- 7.3 in the stimulated group, respectively. Basal cAMP levels were similar throughout the heart, whereas isoproterenol increased cAMP levels in all regions (p < 0.01). Furthermore, cAMP levels in His bundle, after isoproterenol, were higher than in any other region (p < 0.05). These results demonstrate that: (a) cAMP can be measured in discrete portions of the cardiac conduction system; (b) there are significant regional differences of beta-adrenergic control in the cardiac conduction system; and (c) cAMP production after beta-adrenergic stimulation was lower than expected in the AV nodal region, based on previously described beta-adrenoceptor density measurements.

P6020His bundle pacing in patients with abnormal versus intact atrioventricular conduction: from the IMAGE-HBP Study

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
J A Y Koneru ◽  
G O P I Dandamudi ◽  
F A I Z Subzposh ◽  
R K S Shepard ◽  
G K Kalahasty ◽  
...  
Keyword(s):  
Statistical Tests ◽  
Adverse Outcomes ◽  
Cardiac Conduction ◽  
Electrical Performance ◽  
Av Node ◽  
Bundle Branch Block ◽  
Right Ventricular Pacing ◽  
His Bundle ◽  
Av Conduction ◽  
Qrs Duration

Abstract Background Frequent right ventricular pacing causes ventricular dyssynchrony and adverse outcomes. His bundle pacing (HBP) offers a physiological alternative. HBP electrical performance characteristics with cardiac conduction system abnormalities are not well established. Purpose To compare HBP implant procedure related parameters in patients with abnormal atrioventricular (AV) conduction versus those with intact AV conduction. Methods Patients prospectively enrolled in the IMAGE-HBP study undergoing implant attempt with a SelectSecure 3830 lead placed at the putative His-bundle location were included in the analysis. Patients were divided into groups based on AV conduction status. Implant characteristics and electrical performance of the pacemaker were tabulated and compared between the two groups with formal statistical tests. Results Among 60 patients (age 74.7 years old and 60% male), 29 patients (48%) had abnormal AV conduction at or below the AV node (18 with AV block of which 5 also had bundle branch block (BBB), 6 with SND and BBB, and 5 with AV node ablation). The remaining 31 patients (52%) had intact AV conduction. Procedure times were not significantly different between the groups (P=0.26). Selective HBP was achieved in 20.7% of abnormal AV conduction patients and 45.2% of intact AV conduction patients (P=0.06); the remaining patients had non-selective HBP. There were no differences detected in pacing characteristics at implant and paced QRS durations by AV conduction status. Patient with intact AV conduction (N=31) Patients with abnormal AV conduction at or below AV node (N=29) Procedure time in minutes (mean ± SD, Median, IQR) 99±38; 87 [43, 180] 108±32; 108 [65, 182] Fluoroscopy time in minutes (mean ± SD, Median, IQR) 15±12; 11 [3, 50] 16±9; 13 [4, 36] Number of fixation attempts 3.0±2.2 2.2±2.0 sHBP PCT N=14 N=6 V at 0.5ms 1.8±0.9 1.7±1.2 V at 1.0ms 1.6±1.2 1.2±0.8 nsHBP PCT N=17 N=22 V at 0.5ms 2.2±1.9 1.7±1.3 V at 1.0ms 1.5±1.1 1.3±1.1 His signal recorded, number 30 (96.8%) 28 (96.6%) H-QRS interval, ms 46±7 48±13 His Injury of Current, N (%) 23 (74.2%) 18 (62.1%) Baseline Intrinsic QRS, ms 96±16 107±22 Paced QRS duration, ms (from HBP at 1.0ms) 119±23 121±19 Conclusions Selective and non-selective HBP are achievable in bradycardic patients with abnormal and intact AV conduction, including those with BBB. There were no major differences in HBP implant parameters between patients with abnormal AV conduction and those with intact AV conduction.

scholarly journals The Emerging Role of Cardiac Conduction System Pacing as a Treatment for Heart Failure

2020 ◽  
Vol 17 (5) ◽  
pp. 288-298
Author(s):  
Nadine Ali ◽  
Mathew Shun Shin ◽  
Zachary Whinnett
Keyword(s):  
Heart Failure ◽  
Cardiac Function ◽  
Left Bundle Branch Block ◽  
Conduction System ◽  
Cardiac Conduction ◽  
Bundle Branch Block ◽  
His Bundle ◽  
His Bundle Pacing ◽  
Patients With Heart Failure ◽  
Ventricular Activation

Abstract Purpose of Review The aim of cardiac resynchronization therapy (CRT) is to improve cardiac function by delivering more physiological cardiac activation to patients with heart failure and conduction abnormalities. Biventricular pacing (BVP) is the most commonly used method for delivering CRT; it has been shown in large randomized controlled trials to significantly improve morbidity and mortality in patients with heart failure. However, BVP delivers only modest reductions in ventricular activation time and is only beneficial in patients with prolonged QRS duration. In this review, we explore conduction system pacing as a method for delivering more effective ventricular resynchronization and to extend pacing therapy for heart failure to patients without left bundle branch block (LBBB). Recent Findings The aim of conduction system pacing is to provide physiological ventricular activation by directly stimulating the conduction system. Current modalities include His bundle and left conduction system pacing. His bundle pacing is the most established method; it has the potential to correct left bundle branch block and deliver more effective ventricular resynchronization than BVP. This translates into greater acute haemodynamic improvements and observational data suggests that His-CRT results in improvements in cardiac function and symptoms. AV-optimized His bundle pacing is being investigated in patients with heart failure and long PR interval without LBBB, to see if this improves exercise capacity. More recently, a technique for pacing the left bundle branch has been developed. Early studies show potential advantages including low and stable capture thresholds. Summary Conduction system pacing can deliver more effective ventricular resynchronization than BVP, which has the potential to deliver greater improvements in cardiac function. It may also provide the opportunity to extend pacing therapy for heart failure to patients who do not have LBBB. Further data is required from randomized trials to assess these promising pacing techniques.

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