Page 143 - Rapid Review of ECG Interpretation in Small Animal Practice, 2nd Edition

Answer 59 New Holter Monitoring ECG Cases

Answer 59
VetBooks.ir 1 The clinical signs at presentation suggested a high risk of sudden death and prompted the start of

antiarrhythmic therapy. Thus, Holter data prior to start of sotalol are not available for comparison and
whether or not sotalol reduced the baseline number of VPCs is uncertain; however, the total number of
VPCs while receiving sotalol is relatively high.
2 The initial dose of sotalol is at the lower end of the dose range (1.5–2.5 mg/kg q 12 h), and the dose
was increased to 2.2 mg/kg q 12 h. A repeat Holter 1 week later revealed a decrease in number of
VPCs of >98% as compared with the previous recording.

Time Treatment VPC/24 h Runs of VT/24 h Ventricular ectopic beats as
percentage of total number of
beats/24 h
+1 week Sotalol 1.5 mg/kg BID 6,415 33 6.2%
+2 weeks Sotalol 2.2 mg/kg BID 84 0 <0.1%

3 Control of arrhythmias can change over time as the underlying disease progresses. Repeat Holter
recordings at 6–12-month intervals are often considered, depending on the severity and complexity of
the initial arrhythmias or recurrence of clinical signs. Consider the follow-up Holter results obtained
6 months later, which showed apparent loss of efficacy of the sotalol.

Time Treatment VPC/24 h Runs of VT/24 h Ventricular ectopic beats as
percentage of total number of
beats/24 h
+6 months Sotalol 2.2 mg/kg BID 23,102 425 21.0%

Inadequate arrhythmic suppression with sotalol might benefit from the addition of mexiletine and, in this
case, resulted in marked reduction of VPCs, although there were still 18 runs of VT.

Time Treatment VPC/24 h Runs of VT/24 h Ventricular ectopic beats as
percentage of total number of
beats/24 h
+7 months Sotalol 2.2 mg/kg BID 302 18 <1.0%
plus
Mexiletine 5.5 mg/kg

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