![]() ![]() The similarity of this rhythm to marked sinus arrhythmia. SA Wenckebach with a ladder diagram to show the progressive conduction delay between SA node and the atria. The PP interval following the pause is greater than the PP interval just before the pauseĭifferential Diagnosis: sinus arrhythmia without SA block.The pause duration is less than the two preceding PP intervals.PP intervals gradually shorten until a pause occurs (i.e., the blocked sinus impulse fails to reach the atria).This declining increment results in the following findings: Impulse gets smaller until conduction failure finally occurs. The rules are the result of decremental conduction where the increment in conduction delay for each subsequent The following 3 rules represent the classic rules of Wenckebach, which were originally described for ![]() Furthermore, the differentiation is electrocardiographically interesting but not clinically important. There are two types, although because of sinus arrhythmia they may be hard toĭifferentiate. Sino-Atrial Exit Block (SA Block):Ģnd Degree SA Block: this is the only degree of SA block that can be recognized on the surface ECG (i.e., intermittent conductionįailure between the sinus node and the right atrium). This section considers conductionĭisorders in the anatomical sequence that defines the cardiac conduction system so lets begin. The term exit block is used to identify conduction delay orįailure immediately distal to a pacemaker site. In Type I block there is decremental conduction which means that conduction velocity progressively slows down In addition, 2nd degree heart block occurs in two varieties: Type I (Wenckebach) and Disorders of conduction may manifest as slowed conduction (1st degree), intermittent conduction failure (2nd degree), orĬomplete conduction failure (3rd degree). Sino-atrial connections, the AV junction, the bundle branches and their fascicles, and ending in the distal ventricular Purkinjeįibers. Heart block can occur anywhere in the specialized conduction system beginning with the This section considers all the important disorders of impulse conduction that may occur within the cardiac conduction system Type I (Wenckebach) 2nd Degree AV Block.
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