Related Experiment Video

Updated: Aug 15, 2026

High-frequency High-resolution Echocardiography: First Evidence on Non-invasive Repeated Measure of Myocardial Strain, Contractility, and Mitral Regurgitation in the Ischemia-reperfused Murine Heart

High-frequency High-resolution Echocardiography: First Evidence on Non-invasive Repeated Measure of Myocardial Strain, Contractility, and Mitral Regurgitation in the Ischemia-reperfused Murine Heart

Published on: July 9, 2010

Effects of abrupt changes in cycle length on refractoriness of the His-Purkinje system in man

S Denker, M Shenasa, C J Gilbert

|January 1, 1983

Insights

Abrupt changes in atrial cycle length significantly impact the His-Purkinje system

Area of Science:

Electrophysiology
Cardiac Conduction
Arrhythmia Mechanisms

Background:

Atrial fibrillation frequently involves abrupt changes in atrial cycle length.
The impact of these cycle length variations on the His-Purkinje system (HPS) during aberrant ventricular conduction (VAb) is not well understood.

Purpose of the Study:

To investigate the effects of abrupt changes in atrial cycle length on the relative refractory period (RRP) of the His-Purkinje system (HPS).
To determine how these changes influence the occurrence of aberrant ventricular conduction (VAb).

Main Methods:

Evaluated the RRP of the HPS in 12 patients with VAb during sinus rhythm.
Used three methods: constant atrial cycle length (method I), abrupt changes in cycle length (method IIA: longer preceding cycles, method IIB: shorter preceding cycles), and a constant cycle length derived from method II (method III).

Main Results:

Method IIA (longer preceding cycles) shortened the RRP-HPS in 8/12 patients, despite a longer preceding HH interval.
Method IIB (shorter preceding cycles) prolonged the RRP-HPS in 10/12 patients, and VAb occurred only in this condition in 2 patients.
Method III confirmed that abrupt cycle length changes, not just the final cycle length, influenced HPS refractoriness and VAb.

Conclusions:

Abrupt alterations in atrial cycle length unpredictably modify His-Purkinje system functional properties.
These findings suggest that dynamic changes in atrial rhythm play a crucial role in the development of aberrant ventricular conduction during atrial fibrillation.

Read full analysis

Abstract:

Abrupt changes in cycle length (CL) occur frequently in the clinical setting of atrial fibrillation. However, the effects of such changes on the His-Purkinje system (HPS) have not previously been considered during aberrant ventricular conduction (VAb). In 12 patients who manifested VAb with atrial premature stimulation (A2) during sinus rhythm, the relative refractory period (RRP) of the HPS was evaluated during a constant atrial CL (method I) and during abrupt changes in the CL (method II), wherein the A2 was coupled to an atrial CL (last A1A1) comparable to method I. This last A1A1 during method II was preceded by a series of constant atrial CLs 100-200 msec longer (method IIA) in 11 of 12 patients, or 109-300 msec shorter (method IIB) in all 12 patients. Although abrupt changes in the atrial CL using method IIA resulted in a longer HH interval (by 0-30 msec; mean 13.2 +/- 9.2 msec) preceding the A2, the RRP-HPS was 5-20 msec shorter (mean 9.3 +/- 5.3 msec) compared with method I in eight patients. The effect of abrupt changes was further evaluated in nine patients using method III, with a constant atrial CL, with a duration equal to the last H1H1 interval of method IIA. The VAb that occurred with method III was not manifested with method IIA in seven of nine patients, and in two patients the RRP-HPS was the same or less. Conversely, method IIB resulted in a shorter HH interval (by 0.110 msec; mean 28.9 +/- 21.1 msec) preceding A2, but in 10 patients, RRP-HPS was 5-40 msec longer (mean 20.7 +/- 10.5 msec) than that of method I and in two, VAb was only manifested using method IIB. Further scanning with method III, derived from the HH interval immediately preceding A2 of method IIB, was performed in seven patients and compared with method IIB. Prolongation in the RRP-HPS was shown using the latter method. The results indicate that abrupt changes in CL influence the functional behavior of the HPS in a manner not anticipated. Such changes may have important implications in determining the occurrence of VAb during atrial fibrillation.

More Related Videos

Real-Time Proxy-Control of Re-Parameterized Peripheral Signals using a Close-Loop Interface

Real-Time Proxy-Control of Re-Parameterized Peripheral Signals using a Close-Loop Interface

Published on: May 8, 2021

In Silico Clinical Trials for Cardiovascular Disease

In Silico Clinical Trials for Cardiovascular Disease

Published on: May 27, 2022

Related Concept Videos

The Cardiac Cycle

The Cardiac Cycle

The heart beats rhythmically in a sequence called the cardiac cycle—a rapid coordination of contraction (systole) and relaxation (diastole).
The Process
Electrical signals—sent from the sinoatrial (SA) node in the right atrial wall to the atrioventricular (AV) node between the right atrium and right ventricle—cause both atria to simultaneously contract. When the signal reaches the AV node, it pauses for approximately a tenth of a second, allowing the atria to contract and empty blood into the...

Doppler Effect - I

Doppler Effect - I

The Doppler effect and Doppler shift were named after the Austrian physicist and mathematician Christian Johann Doppler in 1842, who conducted experiments with both moving sources and moving observers. Consider an observer standing on a street corner, observing an ambulance with a siren sound passing by at a constant speed. The observer experiences two characteristic changes in the sound of the siren. Initially, the sound increases in loudness as the ambulance approaches and decreases in...

Electrophysiology of Normal Cardiac Rhythm

Electrophysiology of Normal Cardiac Rhythm

The normal cardiac rhythm is a synchronized electrical activity that facilitates the regular and coordinated contraction of the heart muscle. This process is essential for efficient blood circulation throughout the body. The fundamental elements involved in establishing and maintaining this rhythm include the unique electrical properties of cardiac muscle cells, the sinoatrial (SA) node's pacemaker function, the specialized conducting system, and the ionic mechanisms underlying each phase of...

Mechanism of Cardiac Arrhythmias

Mechanism of Cardiac Arrhythmias

Arrhythmias are irregular heart rhythms occurring when the heart's electrical impulses become abnormal. These disturbances can lead to various symptoms, depending on their severity and the underlying cause. Some common factors contributing to arrhythmias include hypoxia, ischemia, electrolyte imbalances, excessive catecholamine exposure, drug toxicity, and muscle overstretching. Arrhythmias can be classified into two main types based on the rate and site of origin of abnormal heart rhythms.

Disturbances in Heart Rhythm

Disturbances in Heart Rhythm

Arrhythmia or dysrhythmia refers to an abnormal heart rhythm caused by a defect in the heart's conduction system. It can cause the heart to beat irregularly, too quickly, or too slowly, leading to symptoms like chest pain, shortness of breath, and fainting. Factors such as stress, caffeine, alcohol, nicotine, cocaine, certain drugs, congenital defects, diseases, and electrolyte abnormalities can trigger arrhythmias.
Arrhythmias are categorized by their speed, rhythm, and origin. A slow heart...

Dysrhythmias III: Characteristics of Dysrhythmias

Dysrhythmias III: Characteristics of Dysrhythmias

Dysrhythmias, also known as arrhythmias, are irregular heart rhythms that result from abnormal electrical activity in the heart, affecting its ability to circulate blood efficiently. Tachyarrhythmias, a subset of dysrhythmias, are characterized by abnormally fast heart rates exceeding 100 beats per minute. Here are some types of tachyarrhythmias with their distinct ECG features:Sinus Tachycardia:Sinus tachycardia presents a regular heart rhythm with an increased rate of 101-180 beats per minute.

Articles linked to this work by shared authors, journal, and citation graph.

EDTA sample contamination is common and often undetected, putting patients at unnecessary risk of harm.

International journal of clinical practice·2009

Common supraventricular tachycardias: mechanisms and management.

AACN clinical issues·2001

Pharmacokinetic interaction between ondansetron and cyclophosphamide during high-dose chemotherapy for breast cancer.

Cancer chemotherapy and pharmacology·1998

Cost of managing anemia with and without prophylactic epoetin alfa therapy in breast cancer patients receiving combination chemotherapy.

American journal of health-system pharmacy : AJHP : official journal of the American Society of Health-System Pharmacists·1998

Reduced mortality following bone marrow transplantation for breast cancer with the addition of peripheral blood progenitor cells is due to a marked reduction in veno-occlusive disease of the liver.

Bone marrow transplantation·1998

Recoverin inhibits the phosphorylation of dark-adapted rhodopsin more than it does that of bleached rhodopsin: a possible mechanism through which rhodopsin kinase is prevented from participation in a side reaction.

The Biochemical journal·1997

See all related articles