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Related Concept Videos

Disturbances in Heart Rhythm01:28

Disturbances in Heart Rhythm

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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...
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Mechanism of Cardiac Arrhythmias01:28

Mechanism of Cardiac Arrhythmias

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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.
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Electrophysiology of Normal Cardiac Rhythm01:19

Electrophysiology of Normal Cardiac Rhythm

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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...
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Electrocardiogram01:29

Electrocardiogram

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An electrocardiogram (ECG or EKG) is a critical diagnostic tool that records the electrical signals produced by the heart during each heartbeat. This recording is achieved through electrodes placed strategically on the arms, legs, and chest. The electrocardiograph amplifies these signals and produces 12 distinct tracings, offering a comprehensive understanding of the heart's electrical activity.
Three major waveforms are present in a typical ECG recording: the P wave, the QRS complex, and...
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Electrocardiogram Fundamentals01:28

Electrocardiogram Fundamentals

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Introduction
An electrocardiogram (ECG) is a diagnostic tool for identifying cardiac conditions such as arrhythmias, conduction abnormalities, and myocardial ischemia.
Definition
An electrocardiogram (ECG) visualizes the heart's electrical activity by tracing the electrical movement associated with each heartbeat on a graph or monitor. As the heart beats, an electrical wave passes through it, correlating with the cardiac cycle events.
Parts of an ECG
An ECG utilizes electrodes on the skin...
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Correlation between ECG and Cardiac Cycle01:25

Correlation between ECG and Cardiac Cycle

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The electrical signals recorded on an electrocardiogram (ECG) occur before the mechanical processes of contraction and relaxation during the cardiac cycle.
A cardiac action potential originates in the SA node and spreads throughout the atria and the AV node in approximately 0.03 seconds. This results in the P wave in an ECG and triggers atrial contraction. The action potential is then briefly slowed at the AV node, allowing the atria to contract and fill the ventricles with blood before...
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Acute Electrical Synchronization Achieved With Dynamic Atrioventricular Delays During Biventricular and Left

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Dynamic atrioventricular delays and multisite pacing significantly improve cardiac resynchronization therapy (CRT) electrical synchrony. Combining both achieved the narrowest QRS duration, enhancing CRT effectiveness.

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Area of Science:

  • Cardiology
  • Electrophysiology
  • Medical Devices

Background:

  • Cardiac resynchronization therapy (CRT) effectiveness depends on optimal pacing timing and location.
  • Dynamic atrioventricular delays (SyncAV) and multisite left ventricular (LV) pacing (MultiPoint Pacing [MPP]) are advanced CRT features.
  • The combined impact of these technologies on electrical synchrony has not been fully elucidated.

Purpose of the Study:

  • To evaluate the acute electrical synchrony of various CRT pacing configurations.
  • To compare static versus dynamic atrioventricular delays (AVDs).
  • To assess single-site versus multisite LV pacing and the role of right ventricular (RV) pacing.

Main Methods:

  • Eighty-five CRT-indicated patients with left bundle branch block and intact AV conduction were studied.
  • Electrocardiographic QRS duration was measured during intrinsic conduction and various pacing modes (BiV, BiV-MPP, LVSS, LVMPP) with static and dynamic AVDs.
  • Acute changes in QRS duration were analyzed to assess electrical synchrony.

Main Results:

  • All evaluated CRT pacing modes significantly reduced QRS duration compared to intrinsic conduction (P < 0.01).
  • The addition of SyncAV further reduced QRS duration across all pacing configurations (P < 0.0001).
  • Multisite LV pacing (MPP) combined with SyncAV yielded the narrowest QRS duration, indicating superior electrical synchrony.

Conclusions:

  • Multisite LV pacing (MPP) coupled with dynamic AVDs (SyncAV) optimizes electrical synchrony in CRT patients.
  • This combination achieved the most significant reduction in QRS duration, suggesting enhanced CRT response.
  • Pacing from all available ventricular sites (RV + LV1 + LV2) with dynamic AVD timing maximizes electrical synchrony.