Physiologic VDD versus Nonphysiologic VVI Pacing in Canine 3rd‐Degree Atrioventricular Block

Abstract

Historically, ventricular demand, nonphysiologic (VVI) pacing has been the most commonly used modality to treat 3rd-degree atrioventricular (AV) block. The goal of this study was to determine the feasibility of using a commercial, single-lead, physiologic (VDD) pacemaker in dogs with 3rd-degree AV block. Furthermore, we hoped to characterize and identify differences in the radiographic, echocardiographic, neurohormonal, and quality of life consequences of physiologic versus nonphysiologic pacing. We evaluated 10 dogs during a 12-week crossover study. Acutely, rate-matched physiologic pacing reduced pulmonary capillary wedge pressure by 19% compared with nonphysiologic pacing. VDD pacing significantly reduced left atrial size normalized to body weight, left atrial-to-aortic root ratio, and left ventricular end-systolic dimension and increased fractional shortening, aortic Doppler velocity, cardiac output, and stroke volume compared with VVI pacing. Variable rate VDD pacing resulted in a significantly slower heart rate (HR) during echocardiography than fixed-rate (100 bpm) VVI pacing. AV synchronous pacing reduced circulating N-terminal proatrial natriuretic peptide (ANP), norepinephrine (NOR), and epinephrine (EPI) concentrations compared with asynchronous pacing. There were no significant differences in systemic blood pressure, thoracic radiographs, or owner-perceived quality of life. The median percentage of AV synchronous pacing during the VDD modality was 99.8% (range, 1.2 to 99.9%). This study confirms the potential to achieve physiologic pacing with a commercial, single-lead system in dogs. VDD pacing improved hemodynamics and neurohormonal profiles over asynchronous pacing although the long-term clinical benefits of these changes remain to be determined.

Indications for permanent pacing in dogs and cats

“…The prevalence of chronotropic incompetence in dogs with third-degree AVB is unknown. The potential for humans to develop sinus node disease after PM implantation is one argument against the utilization of a single lead physiologic PM [138]. In veterinary medicine, it has been described that dogs that present an atrial rate <70 beats per minute and a negative atropine response test (<25% increase of sinus rate 20e30 min post 0.04 mg/kg atropine SQ injection) [63] are excluded from consideration of single lead VDD PM implantation [110].…”

Dual Chamber Pacemaker Implantation in Dogs with Atrioventricular Block

“…In long‐term follow up studies the incidence of atrial fibrillation and pacemaker syndrome was significantly reduced 18 . In 1 study in dogs with AV block, VDD pacing was superior to VVI pacing as shown by an improvement in hemodynamic status and neurohormonal profiles 14 …”

“…The alternative is the implantation of a single lead with a floating arterial electrode and VDD programming. Using the latter system, AV synchrony can be achieved, but there is no pacing in the right atrium 14 . In humans, dual chamber sequential pacing compared with VVI single chamber pacing improved cardiac output, blood pressure, exercise tolerance, and increased quality of life 15–17 .…”

“…Implantation of a dual chamber pacemaker still is rarely described in veterinary medicine 4,10,14,19, 20 , a . In human patients, disadvantages of dual chamber systems include the time‐consuming implantation and programming procedure, increased cost, and potentially higher complication rates 21–23 .…”

Use of transcutaneous external pacing during transvenous pacemaker implantation in dogs

“…Sisson and others (1991), Oyama and others (2001), Wess and others (2006), Johnson and others (2007) and Hildebrandt and others (2009) used TTP in 10 per cent (four of 40), 46 per cent (69 of 154), 82 per cent (78 of 105), 50 per cent (52 of 104) and 24 per cent (eight of 33) of dogs that underwent PMI, respectively. There are also some reports on the use of TTP during PMI in single cases (Lombard and Buchanan 1976, Flanders and others 1999, Bulmer and others 2006, Saunders and others 2007). In addition, Darke and others (1989) attached temporary pacing leads to permanent pacing leads to perform external pacing.…”