Rate Responsive Pacemakers: A Rapid Assessment Protocol

Abstract

Rate responsive (RR) pacemakers are commonly implanted with nominal conservative factory-set responsiveness, which is usually accepted because established exercise protocols are time-consuming. We aimed for efficient assessment of RR pacemaker settings. We tested exercise heart rates in controls and paced patients using a brief exercise test that approximates real-life levels of exertion. The test used a nonmotorized treadmill: 30 seconds walking at patient-determined speed followed by 15 seconds brisk exertion. Subjects totaled 110: 26 with RR pacemakers; 22 with non-RR pacers; 27 "sick" nonpaced control patients; and 35 healthy controls. Heart rate (HR) was measured prior to exercise, after 30 seconds of casual walk, after 15 seconds of brisk walk, and 1 minute into recovery. Testing required <5 minutes from set-up to recovery. The 26 RR pacer patients had a mean HR at rest = 74 +/- 10 beats per minute (bpm), walk = 87 +/- 14, and brisk = 94 +/- 18 (increase 27%). Non-RR pacer patients (n = 22): rest = 73 +/- 12 bpm, walk = 88 +/- 14, and brisk = 94 +/- 17 (increase 24.3%, P = 0.60 vs RR patients). "Sick" controls (n = 27): rest = 78 +/- 14 bpm, walk = 102 +/- 17, and brisk = 117 +/- 18 (increase 51.9%, P< 0.001 vs RR pts). For the healthy controls, HRs were at rest 83+/11 bpm, walk = 104 +/- 12, and brisk = 117 +/- 13 (P< 0.001 compared to both paced groups; P = NS vs sick controls). Nominal RR settings may be suboptimal for many patients. The nonmotorized treadmill test allows quick and inexpensive assessment of RR programming, with the potential for efficient RR optimization.