Feline Medicine Q&A 01

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A lead II ECG is shown. The paper speed is 25 mm/second and amplitude is set so that 1 cm is equivalent to 1 mV.

Question	Answer		Article
What is the heart rate?	The easiest way to assess heart rate on an ECG is to count the number of complexes present in 6 seconds and then multiply this number by 10 to obtain a heart rate in beats per minute. In this question, only a short trace is included which means that this technique cannot be used. Since the heart rhythm is regular, the heart rate can be calculated by measuring the distance between the QRS complexes. If the paper speed is 25 mm/second, there will be 1500 mm/minute, thus the heart rate is 1500 ÷ distance between two complexes. Using the formula in this case, the heart rate is estimated to be 100 beats per minute.		Link to Article
Is the heart rate regular?	Yes, the heart rate is very regular.		Link to Article
Describe the complexes present.	There are no visible P waves and the QRS complexes are wider than they should be (around 0.06 seconds; normal QRS duration is <0.04 seconds). It is also important to check the traces from other leads for presence of P waves.		Link to Article
What is your assessment of this ECG?	This is an example of atrial standstill with an escape rhythm. Failure of atrial activity (which can be confirmed on echocardiography) may be present because of hyperkalaemia (e.g. hypoadrenocorticism, diabetes mellitus ketoacidosis, lower urinary tract obstruction), toxicity (e.g. digoxin), or severe cardiac disease. Escape rhythms are characterized by their slow rate and wide QRS complexes and they occur when the normal pacemaker tissue fails to discharge for a prolonged period. Ventricular escape rhythms originating in the tissues closest to the atrioventricular node (junctional escape complexes) appear most like normal QRS complexes, as in this example.		Link to Article