Rate-responsive pacing

Bonnet J-L, Geroux L, Cazeau S. Evaluation of a dual sensor rate responsive pacing system based on a new concept PACE 1998 21 2198-2203. 

Rosenqvist M, Aren C, Kristensson BE, Nordlander R, Schuller H. Atrial rate-responsive pacing in sinus node disease. Eur Heart J. 1990 11 537-542. 

Hedman A, Nordlander R. QT sensing rate responsive pacing compared to fixed rate ventricular inhibited pacing a controlled clinical study. Pacing Clin Electrophysiol. 1989 12 374-385. 

SuUce N, Chambers J, Dritsas A, Sowton E. A randomized double-blind crossover comparison of four rate-responsive pacing modes. J Am Coll Cardiol. 1991 17 696-706. 

The incidence of permanent pacemaker implantation varies between 6% and 23% (Melton et al. 1999) using the biatrial technique. If necessary a rate-responsive pacing system should be implanted as chronotropic incompetence is the rule. With the use of the bicaval anastomosis technique, the incidence of permanent pacemaker implantation diminished to less than 5%. 

Category Chamber(s) paced Chamber(s) Response to Rate Multisite pacing... 

The fourth letter in the code reflects the ability of the device to provide a rate response. For example, a DDDR device is one that is programmed to pace and sense in both chambers and is capable of sensor-driven rate variability. The fifth letter is used to indicate the device s ability to do multisite pacing. 

Rate-adaptive pacing was developed to provide a heart rate response to meet the metabolic needs of the patient with chronotropic incompetence. For the patient in sinus rhythm, DDDR pacing provides an adequate heart rate with atrial pacing at rates that may exceed the maximal sinus rates. For the patient in chronic atrial fibrillation, VVIR pacing provides an adequate heart rate response with ventricular pacing. 

Rate-adaptive pacing relies on the performance of sensors to provide input to the pacemaker regarding the appropriate heart rate for the activity. An algorithm then converts the sensor data to a specific heart rate response. Currently available sensor systems are so-called open loop because an external algorithm must be apphed to the sensor data to determine an appropriate heart rate. A closed-loop system would internally regulate the heart rate response based on the sensor data without requiring adjustment of an external algorithm. 

Mehta D, Lau C-P, ward DE, et al. Comparative evaluation of chronotropic responses of QT sensing and activity sensing rate responsive pacemakers. PACE 1988 11 1405-1412. 

Antonelli D, Freedberg NA, Rosenfeld T. Transiliac vein approach to a rate-responsive permanent pacemaker implantation. PACE 1993 16 1637. 

Nonetheless, even the longest programmable AV delays are sometimes not adequate at preventing ventricular pacing especially if the rate-responsive function is activated. 

The potential benefit of a rate-drop response pacemaker was evaluated by Ammirati et al. in the SYDIT trial (96). They studied a total of 20 patients over a 17 4 month follow-up period and found that the rate drop pacing algorithm was better than rate hysteresis. Ammirati et al. (97) later reported... 

Fig. 19.22 A patient was exercised in an effort to set-up the rate modulated features of his pacemaker as he was identified as having chronotropic incompetence complicating his marked sinus node dysfunction. Rather than using a formal exercise lab, he was taken for a walk in the Clinic corridor and then the Prediction Model of his Trilogy DR -I- pulse generator was accessed. The period between the two heavy vertical lines represents this exercise. The dotted lines represent the chaotic activity of his atrium during the walk. The sensor had been disengaged (passive) and the thin solid line shows the heart rate response that would have occurred if the sensor were controlling the paced rate at the displayed programmed parameters.

The phenomenon of transitioning from atrial synchronous ventricular pacing to atrio-ventricular sensing due to upper rate limit violation is sometimes called "pre-empted Wenckebach" upper rate response. Pre-empted Wenckebach becomes troublesome in the patient with a biventricular ICD because of the possibility of ventricular double counting. 

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