Conducting Systems of the Heart ILOs Flashcards
What is cardiac electrophysiology?
Cardiac electrophysiology is the study of the electrical processes that control heart muscle contraction, including the generation and propagation of action potentials.
What initiates the electrical impulse in the heart?
The electrical impulse is initiated by the sinoatrial (SA) node, located in the right atrium, which acts as the heart’s natural pacemaker.
What are the components of the cardiac conduction system?
The cardiac conduction system includes the SA node, AV node, bundle of His, right and left bundle branches, and Purkinje fibers.
How do Purkinje fibers function in cardiac conduction?
Purkinje fibers rapidly distribute the electrical impulse to the ventricles, ensuring synchronized ventricular contraction.
What is the role of the AV node in cardiac conduction?
The AV node slows down the electrical impulse before it passes to the ventricles, allowing time for the atria to contract and fully empty blood into the ventricles.
What is an action potential in cardiac cells?
An action potential is an electrical signal generated by the movement of ions (mainly sodium, potassium, and calcium) across the cardiac cell membrane, leading to depolarization and repolarization.
What is the principle of “re-entry” in cardiac electrophysiology?
Re-entry occurs when an electrical impulse re-circulates through a pathway, causing repeated stimulation of the heart muscle, which can lead to arrhythmias like atrial flutter and fibrillation.
How does re-entry lead to atrial flutter?
In atrial flutter, a re-entry circuit forms within the atria, causing a rapid and regular atrial contraction, often at rates around 250-350 beats per minute.
What ECG abnormality is commonly seen in atrial fibrillation?
The ECG shows an absence of P waves and an irregularly irregular rhythm due to disorganized atrial electrical activity.
What is the mechanism of atrial fibrillation (AF)?
Atrial fibrillation results from multiple re-entry circuits in the atria, leading to rapid, irregular, and uncoordinated atrial activity with loss of effective atrial contraction.
What happens in bundle branch block (BBB)?
A bundle branch block occurs when one of the bundle branches is blocked, delaying ventricular depolarization on the affected side, leading to a widened QRS complex on ECG.
How does dysfunction of the SA node affect the heart?
SA node dysfunction can lead to sinus bradycardia (slow heart rate), sinus arrest (no impulse generation), or sick sinus syndrome, resulting in erratic heart rhythms.
How does AV block manifest on an ECG?
In AV block, conduction from the atria to the ventricles is delayed or blocked, leading to prolonged PR intervals (first-degree), dropped beats (second-degree), or complete dissociation between P waves and QRS complexes (third-degree).
What is the role of the bundle of His in the conduction system?
The bundle of His transmits the electrical signal from the AV node to the bundle branches, ensuring the impulse reaches the ventricles.
What is Wolff-Parkinson-White (WPW) syndrome?
WPW is a condition where an accessory pathway (Bundle of Kent) allows electrical impulses to bypass the AV node, causing pre-excitation of the ventricles and potentially leading to re-entry tachycardias.
