Solutions to ECG examples
1. Sinus rhythm with second degree AV block.
2. Sinus rhythm with advanced 2nd degree AV block: P-waves are again present without QRS complexes, all QRS complexes however have a P-wave that is uniformly
associated with it. This type of conduction defect will be from AV nodal disease, in dogs pacemakers are recommended.
3. 3rd degree AV block: no association between P-waves or QRS complexes can be seen. Heart rate is slow at around 40 BPM.
4. Hyperkalemia (sinus standstill) in a cat: The rate is slow at 110. P-waves cannot be seen and QRS complexes are wide and
bizarre and T-waves are tall and spiked.
5. 3rd degree AV block in a cat: Rate is around 110 BPM. P-waves and QRS complexes are not associated with each other. Unlike dogs,
in cats a pacemaker is only needed if clinical signs are noted. Usually also from old age fibrosis.
6. Sinus rhythm with left bundle branch block: it is important to not judge rhythms by shape of the waveforms. Here the QRS
is wide and bizarre, but the association between P-wave and QRS is constant, consistent with sinus rhythm.
7. Sinus rhythm with atrial premature contraction: Most complexes have a consistent P-wave to QRS relationship. One premature
complex is noted. Since it has the same morphology as the "normal beats" (deep S-wave likely from conduction defect) this
argues for a supraventricular origin (atrial premature beat).
8. Atrial fibrillation: Heart rate is >240 BPM. The R to R interval are very irregular. P-waves cannot be seen. This is consistent
with atrial fibrillation.
9. Sinus rhythm with paroxysmal ventricular tachycardia: In this ECG there are premature beats present. They differ from the
normal QRS complexes and are wide and bizarre, consistent with a ventricular origin.
10. Predominantly ventricular rhythm: Third complex from the right is a sinus beat. The other beats are all ventricular in
origin (sometimes P-waves are seen but they are not uniformly associated with a QRS). Heart rate is 240 BPM. Where the heart
rate is measured the complexes show R on T where the VPC starts before the VPC before the heart can completely repolarize.
This is of great concern, sudden death is possible.