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Related Concept Videos

Cardiac Action Potential01:30

Cardiac Action Potential

Cardiac action potentials are essential for proper heart function, enabling the rhythmic contractions needed for adequate blood circulation. Nodal cells and Purkinje fibers, specialized for electrical conduction, generate these action potentials.
The cardiac action potential process involves a series of phases characterized by the movement of ions across the cardiac cell membranes, leading to the depolarization and repolarization of the cardiac myocytes.
Ionic Basis of Cardiac Action Potentials
Correlation between ECG and Cardiac Cycle01:25

Correlation between ECG and Cardiac Cycle

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...
Disturbances in Heart Rhythm01:29

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...
ECG Interpretation of Arrhythmias II: Atrial, Junctional and Ventricular Arrhythmias01:25

ECG Interpretation of Arrhythmias II: Atrial, Junctional and Ventricular Arrhythmias

Arrhythmia is a condition characterized by an irregular heart rhythm, with ECG changes that differ based on its origin and nature. The types of arrhythmias discussed below include atrial, junctional, and ventricular arrhythmias.Atrial ArrhythmiasPremature Atrial Complexes (PACs): PACs are early atrial beats caused by stress, caffeine, alcohol, electrolyte imbalances, hypoxia, hyperthyroidism, or certain medications (e.g., bronchodilators and decongestants). The ECG shows early P waves with an...
Dysrhythmias III: Characteristics of Dysrhythmias01:29

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.
Mechanism of Cardiac Arrhythmias01:28

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.

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Myocardial performance is reduced immediately prior to ventricular ectopy.

Poul Erik Bloch Thomsen1, Thomas Fritz Hansen, Christian Jons

  • 1Cardiology Department P, Gentofte University Hospital, Copenhagen, Denmark. pebt@geh.regionh.dk

Heart Rhythm
|August 30, 2011
PubMed
Summary

Ventricular premature beats (VPBs) are preceded by impaired conduction and reduced myocardial performance in sinus beats. This suggests a shared electrical mechanism underlying VPBs and contractile dysfunction in various heart conditions.

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Area of Science:

  • Cardiology
  • Electrophysiology
  • Echocardiography

Background:

  • Previous studies indicated conduction impairment and block in sinus beats preceding ventricular premature beats (VPBs).
  • VPBs often originate from the ventricular outflow tracts.

Purpose of the Study:

  • To investigate if impaired impulse conduction preceding VPBs affects the contractile performance of sinus beats.
  • To utilize Tissue Doppler echocardiography to assess these changes.

Main Methods:

  • Twenty-three patients with VPBs underwent Tissue Doppler echocardiography at 150 Hz.
  • Patients had diverse cardiac conditions including dilated cardiomyopathy and ischemic heart disease.
  • VPB origin was analyzed, and 11 patients received radiofrequency ablation.

Main Results:

  • A statistically significant decrease in myocardial performance was observed in the sinus beat immediately preceding a VPB.
  • Ejection time and peak systolic velocity were significantly shortened (P <.001).
  • Systolic shortening (end-systolic displacement) also showed a significant reduction (P <.001).

Conclusions:

  • Ventricular ectopy is associated with a significant decline in myocardial performance in the preceding sinus beat.
  • This finding suggests a common underlying electrical mechanism, such as localized conduction block, in patients with VPBs.
  • The results were observed across a variety of heart conditions, highlighting a potential unifying pathophysiology.