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A 12-lead ECG of a woman with Ebstein's anomaly: The ECG shows signs of right atrial enlargement, best seen in V1. Other P waves are broad and tall, these are termed "Himalayan" P waves. Also, a right bundle-branch block pattern and a first-degree atrioventricular block (prolonged PR-interval) due to intra-atrial conduction delay are seen.
Some studies have noted the incidence of TIC in adults with irregular heart rhythms to range from 8% to 34%. [5] Other studies of patients with atrial fibrillation and left ventricular dysfunction estimate that 25–50% of these study participants have some degree of TIC. [6] TIC has been reported in all age groups. [6]
The conduction system consists of specialized heart muscle cells, situated within the myocardium. [3] There is a skeleton of fibrous tissue that surrounds the conduction system which can be seen on an ECG. Dysfunction of the conduction system can cause irregular heart rhythms including rhythms that are too fast or too slow.
Sudden arrhythmic death syndrome (SADS) is a sudden unexpected death of adolescents and adults caused by a cardiac arrest. However, the exact cause of the cardiac arrest, and thus the exact cause of death, is unknown. These deaths occur mainly during sleep or at rest. [7] One type of conduction defect known as Brugada syndrome can be ...
The underlying anatomical causes of PSVT, specifically atrioventricular nodal reentry, involve the presence of two functionally distinct conduction pathways within the AV node and the formation of a reentrant circuit that sustains the tachycardia. [8] These pathways within the AV node are known as the fast pathway and the slow pathway. [9]
Common causes include ischemia (lack of blood flow and oxygen to the heart muscle) or progressive fibrosis (excessive scarring) of the heart. [9] It is also possible that a high degree block can result after cardiac surgery during which the surgeon was in close proximity to the electrical conduction system and accidentally injured it.
The electrocardiogram often shows sinus tachycardia or atrial fibrillation, ventricular arrhythmias, left atrial enlargement, and sometimes intraventricular conduction defects and low voltage. When left bundle-branch block (LBBB) is accompanied by right axis deviation (RAD), the rare combination is considered to be highly suggestive of dilated ...
Then, the electrical impulse pathologically passes back into the atria via the accessory pathway, causing atrial contraction, and returns to the AV node to complete the reentrant circuit (see figure). Once initiated, the cycle may continue causing the heart to beat faster than usual.