Authors: Edgar Antezana-Chavez, Tatiana Flores Herrera, Daniel Saavedra Rodriguez
Categories: Original Article, Electrophysiology evaluation, Pacemaker programming, Ventricular pacing burden
Source: Indian Pacing and Electrophysiology Journal
Appropriate programming of cardiovascular implantable electronic devices (CIED) is essential to ensure adequate function and avoid harmful effects. In underdeveloped countries, CIED monitoring and programming are often performed by physicians involved in their implantation. However, many of them often do not have sufficient training in CIED programming.
We aimed to assess the differences in pacemaker programming between electrophysiology (EP) specialists and other physicians.
We retrospectively reviewed changes in pacemaker programming performed by an EP specialist in patients who attended for pacemaker evaluation and reported previous follow-ups by a non-EP specialist.
Among 58 patients (26 males), 41 patients (71%) had programming errors and required setting modifications. The rate adaptative pacing function (R-mode) was incorrectly deactivated in 9 patients (15%) and improperly activated in 2 patients (3%). Unnecessary ventricular stimulation was detected in 23 patients (40%) with a pacing burden of 60% (32–95%). The lower rate limit was unnecessarily high in 12 patients (21%).
Atrial or ventricular pacing output was inappropriate in 15 patients (26%) and was consequently modified (4 patients unnecessarily high, 9 patients below requirements). The auto-adapted pacing output was switched off in 17 of 18 patients (16 due to physician's preference, and 1 due to algorithm inaccuracy). The programmed sensitivity was inaccurate in 2 patients (3%). In 2 patients (3%) switching from DDDR to VVIR mode was required.
We found a high prevalence of errors in pacemaker programming by non-EP specialists. An EP specialist should always be responsible for CIED follow-up.
Keywords: Pacemaker programming, Electrophysiology evaluation, Ventricular pacing burden
Cardiovascular implantable electronic devices (CIED) have become more frequent in recent years. They have proved to improve symptoms, quality of life, and survival. Improvements in the technology of CIEDs have increased their complexity, with numerous programmable functions and the capacity to store large amounts of diagnostic information related to device performance, arrhythmia burden, and other physiologic parameters. Given the increasing CIED indications and its complexity, managing these patients and their devices has led to a specific area of medical practice, electrophysiology (EP), with specialists trained in CIED implantation, programming, and assessment.
Appropriate CIED follow-up and programming are essential to ensure proper performance, optimize function and adjust errors. For instance, in recent years, it has been acknowledged and recommended to avoid the harmful effects of unnecessary ventricular stimulation [1,2]. Some CIED functions reduce battery life and should be deactivated when not required.
In developed countries, follow-up is mainly provided by trained physicians and/or allied health professionals according to expert consensus [3]. In underdeveloped countries, owing to a lack of qualified personnel, and financial support, it may be conducted by industry representatives alone or non-EP physicians. However, many cardiologists and surgeons are trained in CIEDs implantation but usually have insufficient training in its programming.
Bolivia is an underdeveloped country with a low number of EP specialists. As a result, CIED implantation and follow-up are frequently provided by non-EP specialists, mainly cardiologists, and cardiovascular surgeons. Given the fast progress in CIEDs technologies and algorithms, it is likely that many non-EP specialists make mistakes in CIED programming.
Hospital Belga is a tertiary medical center with referrals from several centers within Bolivia. In our cardiology department, all follow-up procedures after September 2021 are being conducted in the pacemaker clinic by an EP specialist trained in CIEDs programming. We aimed to evaluate the efficacy of pacemaker follow-up by EP and non-EP specialists. Changes in pacemaker programming during the initial evaluation of patients were assessed.
We retrospectively analyzed patients who attended our outpatient pacemaker clinic after September 2021. The included patients reported all previous follow-ups conducted by a non-EP specialist. Changes in pacemaker programming during the initial evaluation were assessed. Since left ventricular lead is usually implanted by EP specialists, patients receiving cardiac resynchronization therapy were excluded. Furthermore, implantable cardioverter defibrillators were excluded because of the complexity of settings and the increased need for individualization.
The research followed the Helsinki declaration on ethical conduct. The study was approved by the Institutional Ethics Committee which approved the retrospective data analysis. Informed consent was waived based on the anonymized retrospective nature of the study.
In our institution, a systematic approach to patient follow-up is used by an EP specialist supported by an allied health professional. A complete history of any CIED-related symptom or complaint is obtained. A visual examination of the implantation site is conducted. Pacing and sensing thresholds values, lead impedance, battery voltage and impedance, pacing percentage, lower rate limit (LRL), upper tracking limit (UTL) and/or upper sensor rate (USR), and atrioventricular (AV) interval are assessed during ECG monitoring.
The AV interval was programmed by default unless a complaint or disorder was identified in patients with permanent AV block. On the other hand, in patients with confirmed AV conduction, sinus node disease (SND), or intermittent AV block, algorithms to minimize ventricular pacing were activated. In the absence of an algorithm to minimize ventricular stimulation, the AV interval was prolonged to decrease unnecessary pacing. The necessity of a rate adaptative pacing function (R-mode) or hysteresis was established based on the physician's evaluation without the need for the patient to present symptoms.
Stored arrhythmia episodes were reviewed, and the pacemaker was programmed accordingly. Changes in episode recording parameters to obtain additional information were excluded from this report. Disabling the auto-adaptive pacing output was not considered a programming error unless the algorithm inaccuracy was ascertained.
Continuous variables are expressed as the median and interquartile range (IQR), and categorical data are expressed as numbers (percentage). Statistical analysis was performed using Statistix 7.1 software (Analytical Software, Tallahassee, Florida).
Between October 2021 and May 2022, 58 patients (26 males) previously followed by a non-EP specialist attended our outpatient pacemaker clinic. The median age was 73 (IQR) (66–78) years old. 38 patients (65%) had a dual-chamber pacemaker, and 20 patients (35%) had a single-chamber pacemaker. Indications for pacemaker implantation SND in 17 patients (29%), AV conduction disturbance in 20 patients (34%), atrial fibrillation (AF) with slow ventricular response in 19 patients (33%), and the association of SND and AV conduction disturbance in 2 patients (3%) (Table 1).
Following device examination, 80 programming errors were identified and appropriately modified in 41 patients (71%) (Table 2). The rate adaptative pacing function (R-mode) should have been enabled in 9 pacemaker-dependent patients (15%). Of these, 7 patients had SND, and 2 had AF. In these patients, atrial and ventricular pacing burden was 73% and 95% respectively. On the other hand, the R-mode was needlessly activated in 2 patients (3%). One patient had AF with an adequate ventricular response with the LRL fixed at 70 bpm and a ventricular pacing burden of 32%. The other patient had sinus rhythm and an atrial pacing burden of 24% with manifest chronotropic response during pacemaker evaluation.
Unnecessary ventricular stimulation was detected in 23 patients (40%) with a ventricular pacing burden of 60% (32–95%). 8 patients (35%) had AF with an adequate ventricular response, therefore, the LRL was reduced, and/or hysteresis was activated. In 15 patients (65%) with sinus rhythm (3 intermittent AV block, 12 SND without concomitant AV conduction disturbance), any algorithm to reduce ventricular pacing was activated or the AV interval was extended to allow for intrinsic AV conduction.
The LRL was unnecessarily fixed at 70 bpm and was reduced in 12 patients (21%) (11 patients without SND with AV conduction disorders, 1 patient in AF with adequate ventricular response).
In 15 patients (26%), the atrial and/or ventricular pacing output was inappropriate. Among them, the pacing output was excessively high in 6 patients with pacing thresholds below 1 V. On the contrary, 9 patients had a low pacing output. 8 patients had a pacing threshold > 1.5 V with a pacing output < twice the threshold value. A patient had an atrial stimulation threshold of 0.5 V with a pacing output set at 0.5V. Switching between bipolar and unipolar pacing configurations was required to achieve a lower pacing threshold in 3 patients (20%). A single patient experienced syncopal episodes due to low ventricular pacing output.
The automatic pacing threshold and auto-adaptive pacing output were functioning before evaluation in 18 patients (31%). They were turned off in 16 patients according to the physician's preference and due to algorithm inaccuracy in 1 patient. The inaccuracy of the automatic pacing threshold was found in a patient with AF complete AV block with a Zephyr™ SR pacemaker. In this patient, the most recent auto-pacing threshold was 0.75 V; however, the pacing threshold measured multiple times during assessment was 1.25V.
Two patients (3%) showed an inadequate sensing value. A patient with AF and a single-chamber device exhibited a high ventricular pacing burden due to undersensing. A patient with a dual-chamber pacemaker had atrial oversensing because of a minimum sensing value despite a P wave detection of 2.0 mV.
For a 31-year-old patient, the USR had to be raised above the default setting, due to the patient's age and exercise intolerance. A 20-year-old patient with sinus rhythm and complete AV block presented with a single-chamber device with R-mode off. It was decided to activate the R-mode and perform a subsequent upgrade owing to exercise symptoms.
In 2 patients (3%) with dual-chamber pacemakers, switching to VVIR was required. A patient with atrial lead dislodgement subsequently underwent surgery. A patient with the development of permanent AF for the preceding 3 years.
In the population with programming errors, only 5 patients (12%) were symptomatic. A patient suffered from syncopal episodes due to ventricular low-pacing output. 3 patients had exercise intolerance, a 31-year-old patient with SND with a low USR, a 62-year-old patient with AF and high pacing burden with a disabled R-mode, and a 20-year-old patient with SND and exercise intolerance with a unicameral pacemaker set at 60 bpm with disabled R-mode. A patient with atrial flutter presented palpitations because the automatic mode switch algorithm was programmed DDI at 110 bpm.
In the present study, we sought to find the differences in pacemaker programming between EP and non-EP specialists. The main finding of our research is the need to adjust pacemaker settings in 71% of our population when followed up by an EP specialist.
The detrimental effects of RV pacing have been acknowledged and proved in many clinical trials and it is recommended to avoid them as much as possible. A high RV pacing burden increases the risk of death and HF hospitalization [[4], [5], [6], [7]]. Furthermore, an increased incidence of AF has also been described in patients with inadequate AV intervals [8,9]. These deleterious effects resulted in the development of many algorithms designed to minimize ventricular pacing. It is recommended that they are activated in the absence of excessive prolonged AV conduction [1].
In our population, 40% of patients had unnecessary ventricular pacing, with a ventricular pacing burden of 60%. Previous reports have described an increased incidence of pacing-induced cardiomyopathy with RV pacing burden > 20% [10,11]. Consequently, the risk of pacing-induced cardiomyopathy was significantly increased in our population. However, Left Ventricular (LV) Ejection Fraction and LV dimensions before pacemaker interrogation were unavailable for several patients and are therefore not analyzed in this report.
It was necessary to activate R-mode in 15% of patients with high pacing burden. It is well known that in patients suffering from chronotropic incompetence, a deactivated R-mode may cause symptoms, particularly during exercise. In our population, the need for the R-mode was assessed without a graded exercise test, mainly judging the rate histograms and pacing burden during pacemaker evaluation. Usually, chronotropic incompetence is not easy to diagnose as patients often experience minimal symptoms; hence, rate histograms may help establish the need for the R-mode.
On the other hand, an unnecessarily activated R-mode leads to unnecessary pacing and reduces battery longevity. In our population, 2 patients were required to turn off R-mode. Incorrectly active or inactive R-mode is detrimental not only to battery life but also to patient activity.
Another frequent error found in this report is an inadequate pacing output. There were 6 patients with a needless high-pacing output, which reduced the longevity of the pacemaker. However, patients at risk are those with a pacing safety margin < 1. This has been noticed in 15% of our population, and one patient experienced multiple syncopal episodes owing to a 1 safety margin. This inaccuracy might threaten the lives of patients who rely on pacing. Even when most of our population is asymptomatic, it is undesirable to keep patients at risk.
The auto-adapted pacing output has been deactivated for most patients, reflecting the physician's preference and not an incorrect setting. This algorithm measures the stimulation threshold and automatically updates the pacing output to maximize the device's longevity. This algorithm is widely used and has proven to be useful and safe; however, there are occasional reports of pacing failure owing to erroneous measures [12,13]. The algorithm was considered inaccurate in one patient with AF and complete AV block. There was a difference between the ventricular auto-capture threshold (0.75 V) and the manual threshold values (1.25 V), however, no loss of capture was detected. This discrepancy was considered unsafe; hence the algorithm was switched off. Despite normal circadian variations described for the pacing threshold [14], it is unlikely that the auto-capture algorithm exposes patients to any risk since it provides a backup high-voltage pulse in case of loss of capture [15].
Sensing errors were also discovered. The atrial minimum sensing value was set for a patient, leading to oversensing. If such an error appears in the ventricle, it might be life-threatening.
Finally, despite the high number of setting errors found during pacemaker evaluation, only 12% of patients with programming errors were symptomatic. The absence of symptoms at the time of assessment, however, does not rule out the possibility of future symptoms. Furthermore, many patients may experience an improvement in their overall condition even if they have not previously reported symptoms.
There are some limitations to our study. It was performed at a single center with a small number of patients, although it is unusual for patients to switch physicians during CIED follow-up. Given that only one physician is in charge of pacemaker follow-up, it is likely that many adjustments were based on his preference rather than the patient's needs. Nevertheless, many of the adjustments described are in concordance with the guidelines and recommendations on pacemakers programming. Prior patient follow-up was defined as provided by a non-EP specialist based on the patient's statement. It is possible that in certain patients, the physician remained in the background, allowing an industry representative to assess the CIED on his own. An increased prevalence of CIED programming errors is reported when CIED follow-up is performed entirely by manufacturers’ representatives alone [16]. Finally, the findings may reflect defects of local non-EP physicians and cannot be extrapolated to other places, particularly, many cardiologists have great experience in CIED programing.
In conclusion, patients with pacemakers followed by a non-EP specialist showed an extremely high prevalence of inappropriate programming when assessed by an EP specialist. The relevance of this finding indicates the need to leave CIED follow-up in the hands of EP specialists or non-EP specialists with proper training in CIED programming. Additionally, this shows the need to prepare pacemaker technicians who can also provide CIED monitoring by the guidelines.
None.
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.