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Premature Atrial Contraction example one



This strip shows normal sinus rhythm, with one early beat.  It is not a sinus beat
like all the others: look at the P-wave.  It is shaped differently.   What we see
here is another atrial focus originating a beat before the SA node fires.  This is
called a premature atrial contraction, or PAC.   This beat may also be called a
supraventricular premature beat, or SVPB.  Notice that the R-R interval
following the PAC is the same as all the other R-R intervals, excepting the one
leading to the PAC itself.  Along with the rest of the heart, the sinuatrial node
was depolarized by this PAC, and then has resumed its normal functioning,
re-starting the previous pattern of sinus bradycardia.