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A sinoatrial block (also spelled sinuatrial block) [1] is a disorder in the normal rhythm of the heart, known as a heart block, that is initiated in the sinoatrial node.The initial action impulse in a heart is usually formed in the sinoatrial node (SA node) and carried through the atria, down the internodal atrial pathways to the atrioventricular node (AV) node. [2]
The term normal sinus rhythm (NSR) is sometimes used to denote a specific type of sinus rhythm where all other measurements on the ECG also fall within designated normal limits, giving rise to the characteristic appearance of the ECG when the electrical conduction system of the heart is functioning normally; however, other sinus rhythms can be ...
Electrocardiography is the process of producing an electrocardiogram (ECG or EKG [a]), a recording of the heart's electrical activity through repeated cardiac cycles. [4] It is an electrogram of the heart which is a graph of voltage versus time of the electrical activity of the heart [ 5 ] using electrodes placed on the skin.
Sinus bradycardia is a sinus rhythm with a reduced rate of electrical discharge from the sinoatrial node, resulting in a bradycardia, a heart rate that is lower than the normal range (60–100 beats per minute for adult humans). [1] [2]
Bifascicular block is a combination of right bundle branch block and either left anterior fascicular block or left posterior fascicular block. Conduction to the ventricle would therefore be via the remaining fascicle. The ECG will show typical features of RBBB plus either left or right axis deviation. [7] [8]
By contrast, an AV block occurs in the AV node and delays ventricular depolarization. The term "Wenckebach block" is also used for some heart blocks, and can refer to a second degree type I block in either the SA node or the AV node, however the ECG features of the two are quite distinctly different.
The P wave is a summation wave generated by the depolarization front as it transits the atria. Normally the right atrium depolarizes slightly earlier than left atrium since the depolarization wave originates in the sinoatrial node, in the high right atrium and then travels to and through the left atrium.
Under normal conditions, the heart's sinoatrial node (SA node) determines the rate by which the organ beats – in other words, it is the heart's "pacemaker". The electrical activity of sinus rhythm originates in the sinoatrial node and depolarizes the atria.