Failure of Atrial Capture during DDIR Pacing in a Patient with Sinus Node Disease and Preserved Atrioventricular Conduction: What Is the Mechanism?

Abstract

cardiac pacing, sick sinus syndrome, repetitive nonreentrant VA synchrony, rate-responsive pacing Case PresentationA 66-year-old man underwent implantation of a model 5826, Zephyr TM XL DR pacemaker (St. Jude Medical, Sylmar, CA, USA) for management of sinus node dysfunction associated with paroxysmal atrial fibrillation (AF). Models 1999 and 2088TC active-fixation leads (St. Jude) were implanted in the right atrial appendage and right ventricular mid septum, respectively. Since the sinus rate was 36 beats per minute (bpm) with frequent sinus arrests and episodes of AF, the pacemaker was programmed in DDIR mode with a backup rate of 60 pulses per minute (ppm), maximum sensor-driven rate limit at 120 ppm, and a 300-ms paced atrioventricular (AV) interval. The postventricular atrial refractory periods (PVARP) and postventricular atrial blanking period were set at 275 and 140 ms, respectively. The rate response was programmed "ON," with an auto (+2) response slope, and reaction and recovery times set to fast and medium, respectively. The rate-responsive AV delay was programmed "OFF," the rate-responsive PVARP "LOW," and shortest PVARP at 170 ms. Far-field R-wave oversensing was prevented by the postventricular atrial blanking period setting. The atrial high-rate episodes (AHRE) function was activated to detect atrial rates >170 bpm. Since the P-wave sensing and atrial capture threshold were 2.4-2.7 mV and 0.75 V/0.4 ms, respectively, the atrial sensitivity and pulse amplitude were set at 0.2 mV and 2.5 V/0.4 ms, respectively. Oral bepridil, 150 mg t.i.d., was administered for the prevention of paroxysmal AF.The intracardiac electrograms (iEGM) of recorded AHRE were reviewed 1 week after pacemaker implantation. The recording in Figure 1 shows that while the patient was climbing up and downstairs the sensor-driven atrial pacing (AP) rate increased to 80 ppm. The ventriculoatrial (VA) interval after ventricular pacing (VP) was 220 ms, and the atrial electrogram induced by VA conduction was sensed within the PVARP. Sensor-driven, rate-adaptive DDIR pacing occurred 200 ms after the retrograde P wave was sensed. However, the atrium was not captured, because of persistent refractoriness. Following this ineffective atrial paced event, VP occurred at the programmed AV interval of 300 ms. This lasted for 1 minute 36 seconds, while the patient continued to climb up and downstairs. Pacemaker interrogation revealed normal pacing and sensing thresholds and lead impedances. What is the mechanism of the noncaptured AP and continuous VP in this patient with sinus node dysfunction? DiscussionRepetitive, nonreentrant VA synchrony (RNR-VAS) is not a rare phenomenon with dual-chamber pacemakers. 1,2 Most previously described cases of RNRVAS, which accelerate the pacing rate, have been associated with sensor-driven DDDR pacing. 1,2 This form of VA synchrony is associated with programmed long AV intervals and relatively high atrial rates during DDD or DDDR pacing. We have recently reported a case of RNRVAS, recorded as AHRE in the pacemak...

Atrial Pacing Site and Atrioventricular Conduction in Patients Paced for Sinus Node Disease

“…However, an increase in atrial pacing rate with a fixed programmed AV interval lengthens the intrinsic AV conduction time and increases the rate of ventricular paced events. Longer programmed AV intervals caused by a higher atrial pacing rate may occasionally cause pacemaker syndrome or pacemaker‐induced tachyarrhythmias . While in this study, the Ap‐Vs interval increased gradually as the atrial pacing rate increased in both study groups, the As‐Vs interval associated with RAA pacing was significantly and consistently longer than that associated with LRAS pacing.…”

“…However, a prolonged PR interval may cause manifestations similar to those observed in the pacemaker syndrome, such as fatigue, palpitation, shortness of breath, orthopnea, and near syncope, even in absence of high degree AV block . Furthermore, very long PR intervals associated with pacing algorithms to limit ventricular pacing may worsen the clinical outcomes, despite successful limitation of ventricular pacing . Sweeney et al .…”

“…They hypothesized that an excessive prolongation of the PR interval by atrial pacing adversely influences the cardiac mechanics (AV dyssynchronization) compared with sinus rhythm at any heart rates, particularly in patients presenting with a low LV ejection fraction. In addition, an excessively prolonged AV delay may cause the pacemaker syndrome or pacemaker‐induced tachyarrhythmias …”

“…17 Furthermore, very long PR intervals associated with pacing algorithms to limit ventricular pacing may worsen the clinical outcomes, despite successful limitation of ventricular pacing. [18][19][20][21][22][23][24] Sweeney et al reported that DDD-paced ICD recipients with a >230 milliseconds PR interval and Managed Ventricular Pacing TM algorithm (Medtronic Inc.) experienced a 2.8-fold higher risk of death and hospitalization for management of heart failure than back-up VVI-paced patients (at 40 ppm) with a long PR interval. 18 They hypothesized that an excessive prolongation of the PR interval by atrial pacing adversely influences the cardiac mechanics (AV dyssynchronization) compared with sinus rhythm at any heart rates, particularly in patients presenting with a low LV ejection fraction.…”

“…In addition, an excessively prolonged AV delay may cause the pacemaker syndrome 19 or pacemaker-induced tachyarrhythmias. [20][21][22][23][24]…”