Page 81 - Rapid Review of ECG Interpretation in Small Animal Practice, 2nd Edition

Answer 20 ECG Cases

Answer 20
VetBooks.ir 1 ECGs 20a and 20b show atrial standstill.

2 • The heart rate in ECG 20a is 48 bpm and heart rate in ECG 20b is 75 bpm. In both ECGs, the
rhythm is regular.
• There is an absence of P waves. The QRS complexes in ECG 20a are wide, indicating they are
likely ventricular in origin. The slow rate and absence of normal sinus beats are consistent with a
ventricular escape rhythm. The QRS complexes in ECG 20b are narrow indicating they are likely
supraventricular in origin.
• The lack of P waves is most consistent with atrial standstill. Atrial standstill can be secondary to a
degenerative atrial myopathy or secondary to severe electrolyte abnormalities, such as hyperkalemia.
• The degenerative atrial myopathy is typified by loss of functional atrial myocytes and atrial fibrosis,
and atrial standstill is usually permanent. This condition was suspected in the case of ECG 20a.
• Hyperkalemia can be secondary to metabolic disease (i.e., diabetic ketoacidosis), endocrine
disease (i.e., hypoadrenocorticism), renal failure, or reperfusion injury that sometimes
accompanies feline aortic thromboembolism. In the case of ECG 20b, the dog had
+
hypoadrenocorticism and a serum K of 10 mmol/l (10 mEq/l). Correction of hyperkalemia
(e.g., diuresis, glucose, insulin, and so on) can restore normal sinus rhythm.

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