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Patient
Same patient as previous tracing: 75-year-old man with paroxysmal AF; referred for diagnosis of bradycardia (pulse measurement by his attending physician) and discussion regarding possible pacemaker implantation;
Trace
The ECG pattern is virtually identical to that of the previous tracing with blocked premature atrial complexes and a trigeminy; at the beginning of the tracing, there is a premature atrial complex followed by a broad QRS (left bundle branch block-type conduction aberration);
Exergue
Conduction aberration following a premature atrial complex is more likely to occur with more pronounced prematurity of the extrasystole and with longer preceding cycle which leads to an extension of the refractory period of the blocked branch. On a same tracing, different aberration levels (complete, incomplete or fascicular block) can be observed depending on the degree of prematurity.
A premature complex with narrow QRS virtually eliminates the diagnosis of premature ventricular complex (certain premature ventricular complexes originating from the septum may have a QRS < 120 ms).