Temporary cardiac pacing is commonly performed in bradycardic dogs immediately prior to permanent pacemaker implantation. This maintains adequate cardiac output under general anaesthesia. Transvenous temporary pacing (TVTP) starts before anaesthetic induction and requires fluoroscopy. Transthoracic temporary pacing (TTTP), after anaesthetic induction, does not need fluoroscopy, is less invasive, and is technically simpler but may be less reliable in larger dogs.

Although well described in dogs, there are no published studies comparing TVTP and TTTP directly. We hypothesised that TTTP decreases procedure and fluoroscopy times compared with TVTP, but also increases risk of failure to capture in larger dogs. Our aim was to analyse surgical and anaesthesia records of pacemaker procedures in dogs and compare the success and complication rates associated with both temporary pacing methods.

Records of patients fitted with a pacemaker in a single referral institution between December 2012 and June 2019 were retrospectively reviewed. Data collected included demographics, type of bradyarrhythmia, method of temporary pacing employed, duration of implantation procedure (pre-medication to switching off anaesthetic vaporiser), fluoroscopy times, temporary pacing events (failure to capture, iatrogenic tachyarrhythmia), anaesthetic events (spontaneous arrhythmias, cardiac arrest, hypotension, hypothermia, hypercapnia, hypocapnia, excessive muscle twitching), intra- and post-operative complications, and morbidity and mortality.

A total of 60 dogs were included for analysis. One third of these had TTTP (n=20, 33.66%) compared to two thirds with TVTP (n=40, 66.33%; p=0.013) and the TTTP dogs were lighter (TTTP 9.2 kg [6.38–12.02]; TVTP 26 kg [17.1–34.9]; p<0.001). However, temporary pacing events were similar for both groups (TTTP, 5/20 [25%]; TVTP, 8/40 [20%]; p=0.65).

Although TTTP decreased premedication to induction time (TTTP 65 min [43.5–86.5]; TVTP 105 min [86.5–123.5]; p<0.001) and the total procedure duration (TTTP 200 min [161–239]; TVTP 235 min [203.5–266.5]; p=0.015), it did not decrease fluoroscopy time (TTTP, 269.5 min [117.5–421.5]; TVTP, 295 min [157–433]; p=0.302) and was associated with an increased rate of anaesthetic events (TTTP, 15/19 [78.9%]; TVTP, 17/35 [48.6%]; p=0.03).

Both forms of temporary pacing are reliable. Compared to TVTP, TTTP reduces the time it takes to implant a pacemaker in a dog. This is mainly because it reduces the delay between pre-medication and anaesthetic induction rather than the duration of fluoroscopy. However, this advantage is offset by increased risk of anaesthetic events. Importantly, though, in this retrospective study, the potential influence of bodyweight cannot be discounted.

Disclosures

No disclosures to report.