Rate response failure
63-year-old man with ischemic cardiomyopathy, EF of 54%, narrow QRS with inferior sequelae, on beta blocker therapy; implantation of an Adapta dual-chamber pacemaker for sinus bradycardia; interrogation of the pacemaker 6 months after implantation; notion of exertional dyspnea.
- programming in AAIÛDDD mode without rate response;
- minimum rate at 60 beats/minute and maximal tracking rate at 130 beats/minute; the rate response is not programmed although the maximum rate responsive frequency corresponds to the rate response in the event of mode switching due to atrial arrhythmia (fallback in DDIR mode);
- MVP mode functions properly with almost 100% of spontaneous ventricles;
- long-term atrial histogram showing an absence of rate response and a chronotropic incompetence in this active patient; the atrial rate remains between 60 and 70 beats/minute throughout the follow-up;
- long-term ventricular histogram which also shows this rate limitation; the ventricles are spontaneous.
This first page of the initial interrogation allows an almost complete evaluation of the important elements of patient follow-up:
- there are no signs of battery wear and the residual longevity is estimated at more than 7 years;
- the functioning of the 2 leads is satisfactory (proper pacing and sensing impedances) despite a slightly high ventricular pacing threshold;
- the pacemaker is programmed in AAIÛDDD mode; the rate responsive frequency corresponds to the automatic rate response during a mode switching;
- the «Pacing (% of total)» section allows the analysis of the conduction state of the patient as a percentage of the total elapsed time since the last interrogation during which the device has paced or sensed during the collection period. The percentages are calculated from the daily counts of AS-VS, AS-VP, AP-VS and AP-VP event sequences. The percentages of ventricular sensing approach the 100% mark, indicating a good functioning of the MVP mode and its usefulness;
- the atrial and ventricular histograms indicate the percentage of time spent by the device in pacing and sensing mode in the different rate ranges and allow the diagnosis of chronotropic incompetence. There are 16 rate ranges on this pacemaker, each 10 beats per minute. Rates below 40 beats per minute are included in the "< 40" bracket and rates above 180 beats/minute are included in the "> 180" bracket. In this active patient, there are very few variations in rate which is constantly maintained around the minimum rate. During exertion, the increase in physiological rate contributes to the increase in cardiac output; the dyspnea of this patient may be multifactorial but could be partly explained by the inadequacy between metabolic requirements imposed by the current exercise and absence of change in rate.
In this patient, this chronotropic incompetence must be corrected by the programming of the rate response and the AAIRÛDDDR pacing mode.