Page 145 - Rapid Review of ECG Interpretation in Small Animal Practice, 2nd Edition

Answer 60 New Holter Monitoring ECG Cases

Answer 60
VetBooks.ir 1 The 2-hour mean HR is 167 bpm, which is elevated and indicates poor control of the ventricular rate

secondary to atrial fibrillation. There are frequent VPCs and two runs of VT, which suggest a high risk
for sudden death. The goal is to reduce the 24-hour mean heart rate to 125 bpm or lower.
2 Inappetence is a common side effect of digoxin in dogs. Serum digoxin levels at 6–8 hours post-pill
are routinely performed 1 week after starting the treatment. Dobermans are particularly sensitive
and can experience gastrointestinal side effects even at low serum levels. Digoxin can also induce
ventricular arrhythmias, and for these reasons, digoxin was discontinued. Diltiazem, while useful for
atrial fibrillation, does not suppress ventricular arrhythmias and an additional antiarrhythmic was
prescribed. Because of the poor contractility associated with advanced DCM in this case, sotalol was
not used. Instead, amiodarone therapy was initiated (10 mg/kg BID for 1-week loading dose followed
by maintenance dose of 6.5 mg/kg BID), and a repeat Holter recording was acquired 4 weeks later. The
24 h mean HR was reduced (albeit still above the desired 125 bpm) and the ventricular ectopy and VT
was deemed adequately controlled. (See also Chapter 5, Fig. 5.8.)

Time Treatment 24 h mean VPC/24 h Runs of Total ventricular
HR VT/24 h percentage ectopy
+1 week Diltiazem XR: 3.8 mg/kg BID 167 17,903 2 7.6%
Digoxin: 0.004 mg/kg BID
+4 weeks Diltiazem XR: 3.8 mg/kg BID 138 1,901 0 1.0%
Amiodarone: 6.5 mg/kg BID

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