A new automode switch algorithm for supraventricular tachycardias

Reducing Ventricular Pacing in Sinus Node Dysfunction DDIR versus DDDR

BACKGROUND

The use of DDIR mode has been limited since the advent of mode switch in the DDDR mode. In patients with AV block, DDDR is necessary to maintain AV synchrony. However, DDIR mode may still be beneficial for patients with intact AV conduction. The aim of this study was to compare the incidence of ventricular pacing and atrial tachyarrhythmia in DDIR and DDDR with mode switch in a randomized, single-blind, crossover study, and discuss the utility of both modes.

METHODS AND RESULTS

Twenty-four patients (8 males) with bradycardia-tachycardia syndrome and no signs of AV block (mean age 70.1 +/- -9.1 years) were enrolled and randomized to DDIR or DDDR modes with the leads placed at the right atrial appendage and right ventricular apex. After 12 weeks, patients were switched to the opposite mode. During the study period, atrial high rate episodes and other pacemaker diagnostic data were collected. Significantly less ventricular pacing was observed in DDIR mode (DDIR versus DDDR; 48.9%, 76.5%, P = 0.0002) and atrial high rate episodes were significantly lower in DDIR mode (DDIR versus DDDR; 1.32, 1.85 per day, P < 0.05).

CONCLUSION

In patients with sinus node dysfunction and intact AV conduction, DDIR mode may have important implications for simplifying device programming, device longevity, and to avoid atrial tachyarrhythmia.

Is automatic mode switching effective for atrial arrhythmias occurring at different rates? A study of the efficacy of automatic mode and rate switching to simulated atrial arrhythmias by chest wall stimulation

Automatic mode switching (AMS) is a useful means to avoid rapid ventricular response during atrial fibrillation (AF), but AMS cannot occur if the detected atrial rate during AF is below the mode switching criteria. This may be the result of antiarrhythmic medications, or when the atrial events fall within the atrial blanking period, or if the atrial amplitudes during AF are too small to be sensed. We hypothesize that the addition of an automatic rate switching (ARS) algorithm may complement AMS response during AF with different detected atrial rates. We studied the Marathon DDDR pacemaker (Model 294-09, Intermedics Inc.) with the AMS and ARS algorithms that are independently programmable but can also operate in combination. AF sensed above the AMS rate (160 beats/min) will lead to VDIR pacing, whereas AF below AMS rate will be tracked at an interim rate as dictate by the ARS, at a ventricular response that is 20 beats/min above the sensor indicated rate. Atrial tachyarrhythmias were simulated by chest wall stimulation (CWS). CWS was applied to 33 patients (16 men, 17 women, mean age 69 +/- 11 years) with a Marathon DDDR pacemaker using an external pacer to simulate AF occurring at two rate levels: above the AMS rate (programmed at 160 beats/min) at 180 beats/min and below the AMS rate at 120 beats/min. The maximum, minimum, and mean ventricular rates during CWS in DDDR mode with AMS alone, ARS alone, and their combination were compared. During CWS at 120 beats/min, the AMS plus ARS setting showed a mean ventricular rate of 79 +/- 3 beats/min and 124 +/- 14 beats/min in the AMS setting alone (P < 0.01). With CWS at 180 beats/min, the mean ventricular rate in the AMS plus ARS setting compared to the AMS setting alone was not significantly different. However, the variation in ventricular pacing rate was 7 +/- 14 beats/min in the AMS plus ARS setting and 40 +/- 42 beats/min in the AMS setting (P < 0.05). In conclusion, AMS is effective for simulated atrial tachyarrhythmias sensed above the AMS rate. Combined AMS with ARS is useful to handle simulated atrial tachyarrhythmia at a slower rate and to avoid rate fluctuation during AMS. There is also a possibility that this can be applied to the naturally occurring atrial tachyarrhythmias.

Management of atrial tachyarrhythmias in patients with implantable devices

The incidence of atrial fibrillation in patients with conduction system disease is high and the management of patients with pacemakers and atrial fibrillation is discussed. The use of mode switch algorithms to avoid tracking of atrial arrhythmias is explained in detail and programming and evaluation of different mode switch algorithms is presented.

Mode switching for atrial tachyarrhythmias

Mode switching for atrial tachyarrhythmias is a concept that originated from use of DDI mode and was introduced in the early 1990s to prevent dual-chamber pacemakers from ventricular tracking of rapid atrial rates. This article describes the currently available systems and discusses the advantages and disadvantages of the technique. The results of a preliminary randomized controlled trial of 1 algorithm and plans for a second study are presented.

Quality of life in patients with complete heart block and paroxysmal atrial tachyarrhythmias: a comparison of permanent DDIR versus DDDR pacing with mode switch to DDIR

A prospective double-blind randomized crossover study was done in 15 patients with complete heart block and intermittent ATs. The pacemaker was randomly programmed to dual chamber inhibited rate responsive pacing (DDIR) and to DDDR with mode switch, for 1 month each. An event recorder was given to the patients and after each period, a QOL questionnaire was obtained. Based on telemetric data, all but two patients had AT during follow-up. The duration and frequency of these episodes were not related to mode settings. AV synchrony was better preserved in DDDR (P < 0.05). Most symptom-related event recordings during DDIR showed loss of AV synchrony; DDDR with mode switch caused symptoms due to tracking of ST. Overall the QOL score was not different between the modes. Fewer somatic complaints were noted during DDDR pacing than during baseline. DDIR stimulation showed no difference. Twelve patients preferred the period of DDDR pacing; one experienced severe symptoms during DDIR. In conclusion, patients with paroxysmal AT, DDDR with mode switch, and DDIR had no influence on the occurrence, nor on the duration of AT episodes. AV synchrony was better preserved in DDDR, which was also associated with fewer somatic complaints compared to the baseline. In DDDR, symptoms were observed when ST was tracked. QOL was comparable, although more patients preferred DDDR.

Mode switching in dual chamber pacemakers: effect of onset criteria on arrhythmia-related symptoms

AIMS

Various mode-switching algorithms are available with different tachyarrhythmia detection criteria to be satisfied to initiate mode-switching. This study evaluated three different mode-switching algorithms in patients with paroxysmal atrial fibrillation.

METHODS AND RESULTS

Seventeen patients completed the study. Three mode-switching algorithms were downloaded as software into the pacemaker, each for 1 month in a single-blind, randomized sequence. The criteria to initiate mode-switching were: mean atrial rate ('standard'), '4-of-7' or '1-of-1' atrial intervals to exceed the atrial detection rate. Symptoms for each were measured using the Symptom Checklist Frequency and Severity index. The median number of mode-switch episodes increased from 20 for 'standard' to 39 for '4-of-7' (P=0.029 vs 'standard') and 103 for '1-of-1' (P=0.0012 vs 'standard') onset criteria. Median duration of episodes decreased from 2.5 min with 'standard' to 1.4 min with '4-of-7' and 0.4 min with '1-of-1' onset criteria. Frequency of symptoms was lower using '4-of-7' (18.2 +/- 12.0 vs 23 +/- 12.0, P=0.08) or '1-of-1' (20.4 +/- 12.4 vs 23 +/- 12.0, P=0.07) than 'standard' onset criteria. Severity of arrhythmia tended to be less with either '4-of-7' (16 +/- 10.4 vs 19.1 +/- 19.4, P=0.12) or '1-of-1' (17.5 +/- 10.3 vs 19.1 +/- 9.4, P=0.18) than with 'standard' onset criteria.

CONCLUSIONS

The more sensitive onset criteria for detection of atrial tachyarrhythmias were associated with lower frequency and severity of symptoms.

Atrioventricular nodal ablation and implantation of mode switching dual chamber pacemakers: effective treatment for drug refractory paroxysmal atrial fibrillation

OBJECTIVE

To assess the effect of atrioventricular node ablation and implantation of a dual chamber, mode switching pacemaker on quality of life, exercise capacity, and left ventricular systolic function in patients with drug refractory paroxysmal atrial fibrillation.

PATIENTS

18 consecutive patients with drug refractory paroxysmal atrial fibrillation.

METHODS

Quality of life was assessed before and after the procedure using the psychological general wellbeing index (PGWB), the McMaster health index (MHI), and a visual analogue scale for cardiac symptoms. Nine of the patients also underwent symptom limited exercise tests and echocardiography to assess left ventricular systolic function.

RESULTS

The procedure allowed a reduction in antiarrhythmic drug treatment (p < 0.01). PGWB and symptom scores improved (p < 0.01) but the MHI score did not change. Left ventricular systolic function and exercise capacity were unchanged.

CONCLUSIONS

Atrioventricular node ablation and implantation of a DDDR/MS pacemaker is effective treatment for refractory paroxysmal atrial fibrillation, producing improved quality of life while allowing a reduction in drug burden. The popularity of the treatment is justified, but further studies are needed to determine optimum timing of intervention.

Assessment of atrioventricular junction ablation and DDDR mode-switching pacemaker versus pharmacological treatment in patients with severely symptomatic paroxysmal atrial fibrillation: a randomized controlled study

BACKGROUND

The purpose of the study was to evaluate the effect of AV junction ablation and pacemaker implantation on quality of life and specific symptoms in patients with paroxysmal atrial fibrillation (AF) not controlled by drugs.

METHODS AND RESULTS

We performed a multicenter, randomized, 6-month evaluation of the clinical effects of AV junction ablation and DDDR mode-switching pacemaker (Abl+Pm) versus pharmacological treatment in 43 patients with intolerable, recurrent paroxysmal AF of three or more episodes in the previous 6 months not controlled with three or more antiarrhythmic drugs. Before completion of the study, 3 patients in the drug group withdrew because of the severity of their symptoms and 1 patient assigned to the Abl+Pm group in whom the ablation procedure failed. At the end of the 6 months, the 21 patients of the Abl+Pm group who completed the study showed, in comparison with the 18 of the drug group, lower scores in the Living with Heart Failure Questionnaire (-51%, P=.0006), palpitations (-71%, P=.0000), effort dyspnea (-36%, P=.04), exercise intolerance score (-46%, P=.001), and easy fatigue (-51%, P=.02). The scores for rest dyspnea, chest discomfort, and NYHA functional classification were also lower (-56%, -50%, and -17%, respectively) in the Abl+Pm group, although not significantly. At the end of the study, palpitations were no longer present in 81% of the Abl+Pm group and in 11% of the drug group (P=.0000). AF was documented in 31 of 122 visits (25%) in the Abl+Pm group and in 9 of 107 examinations (8%) in the drug group (P=.0005); chronic AF developed in 5 (24%) and 0 (0%) in the two groups, respectively (P=.04).

CONCLUSIONS

In patients with paroxysmal AF not controlled by pharmacological therapy, Abl+Pm treatment is highly effective and superior to drug therapy in controlling symptoms and improving quality of life. The discontinuation of drug therapy exposes patients to further recurrences of paroxysmal AF and the risk of developing permanent AF.

Failure of automatic mode switching: recognition and management

Dual chamber pacing is desirable to optimize AV synchrony and to potentially decrease the incidence of supraventricular tachyarrhythmias. Patients with alternating periods of both supraventricular tachyarrhythmias and bradycardia pose a difficult challenge when standard dual chamber pacemakers are implanted. The automatic mode switching mode algorithm was introduced to prevent tracking of paroxysmal supraventricular tachyarrhythmias and avoid the adverse hemodynamic and symptomatic consequences of a rapid ventricular response. In some cases, failure to mode switch may take place when the atrial signal during tachycardia is of insufficient amplitude to be sensed. Failure to mode switch may also occur when the atrial signal periodically occurs in the atrial blanking period(s). In this article, we describe failure to mode switch in seven patients with paroxysmal supraventricular tachyarrhythmias after a Telectronics Meta DDDR 1254 device was implanted. Each patient had paroxysmal atrial flutter and/or atrial fibrillation and presented with either repetitive episodes of oscillation between atrial tracking and mode switching to a nonatrial tracking pacing mode or complete failure to mode switch. Six of seven patients were taking antiarrhythmic drugs that resulted in slowing of the atrial cycle length. Pacemaker reprogramming was required in each case to restore reliable mode switching during subsequent recurrences of the atrial tachyarrhythmias. We conclude that careful pacemaker programming of patients with paroxysmal atrial flutter and the Telectronics Meta DDDR 1254 is necessary when patients are taking an antiarrhythmic drug that slows atrial cycle length.

Evaluation of a new sensor-based algorithm to protect against atrial arrhythmias

The SmarTracking (ST) algorithm (Marathon 294-09, Intermedics Inc.) uses the sensor-calculated rate (SCR) to define a "variation band" for the intrinsic sinus rate. If the sinus rate exceeds the upper limit of the band, the ventricular pacing rate is limited by the ST rate (STR) and Wenckebach behavior is observed. The present study was aimed at evaluating the behavior of the ST mechanism in patients with healthy sinus node, during exercise and at rest.

METHODS

Twenty-one patients (15 men; mean age 67.8 +/- 9.7 years) with normal sinus function were studied. Heart rate was recorded via the rate profile of the implanted pacemaker (Relay 294-03, Intermedics Inc.), and STR and SCR were obtained via a previously calibrated strap-on pacemaker. A 15-minute protocol was used during which subjects alternated periods of walking with periods of rest.

RESULTS

The relative difference between the average STR and the average sinus rate (DST) was calculated for each phase of the protocol as well as the maximum number of patients showing inappropriate Wenckebach behavior (#W). At nominal settings, DST was always positive and did not fall below 20%. #W was maximum at rest (5) and during heavy exercise (3). By increasing the STR at rest to 95 ppm and the maximum pacing rate to 150 ppm, the #W was reduced to zero for all types of activity except during very fast walk where #W was 1.

CONCLUSION

In general, there was no competition observed between the STR and the intrinsic rhythm. In some cases, the STR at rest and the maximum pacing rate had to be reprogrammed for optimal performance.

Mode switch despite undersensing of atrial fibrillation in DDD pacing

Mode switching algorithms are commonly used to protect the ventricles against high rates induced by atrial tachycardia. In the case of atrial fibrillation (AF), the response of these algorithms depends on the quality of atrial sensing. The Chorum 7234 DDDR pacemaker uses a new mode switching algorithm, based on a statistical analysis of the atrial rhythm. It includes two criteria of diagnosis: "high" if more than 28 of 32 cycles are abnormally accelerated; and "low" if more than 36 of 64 cycles are abnormally accelerated.

METHODS

From a taped database of electrophysiological studies, episodes of AF lasting more than 2 minutes were selected. A tape recorder replayed the atrial signals into an external Chorum device. Each episode was replayed eight times with a programmed atrial sensitivity increasing from 0.4-2.0 mV. For each criterion of diagnosis and each programmed sensitivity, the percentage of atrial sensing, the time to switching, and the mean ventricular rate were measured. Ten episodes of AF from 10 patients (9 men and 1 woman; ages 62 +/- 16 years) were included: 1.95 +/- 0.97 mV and 196 +/- 64 ms. The sensitivity of the algorithm to diagnose atrial tachycardia reached 100%, for an atrial sensitivity set between 0.4 and 1.0 mV. The mean percentages of atrial sensed events were 74% +/- 18% and 46% +/- 9% for the "high" and "low" criteria, respectively. The mean diagnostic times were 28 +/- 26 seconds and 68 +/- 27 seconds, respectively. Sensing of < 23% of AF events resulted in failure to diagnose the arrhythmias by both algorithms. In the event of diagnostic failure, the mean ventricular pacing rate was 79 +/- 9 ppm.

CONCLUSION

Up to an atrial sensitivity of 1 mV, 100% of AF episodes were diagnosed. The Chorum mode switching algorithms are 100% reliable if > 45% of the AF waves are sensed. In the event of switching failure, the ventricle is protected by an average rate remaining below 80 ppm.

Reliability of a new algorithm for automatic mode switching from DDDR to DDIR pacing mode in sinus node disease patients with chronotropic incompetence and recurrent paroxysmal atrial fibrillation

To evaluate the safety and efficacy of a new algorithm for automatic mode switching (AMS) from DDD-DDDR to DDIR, 26 patients, 16 females and 10 males, mean age 73 +/- 6 years of age, affected by sinus node disease, chronotropic incompetence, and recurrent paroxysmal atrial fibrillation (PAF) received the Medtronic Thera DR pacemaker. The device continuously calculates, in ms, the running average of the intrinsic atrial rate (MAR) and compares the current atrial interval (CAI) with the stored MAR. When the CAI is greater than the MAR it increases by 8 ms, and when the CAI is less than the MAR, it decreases by 23 ms. When MAR < or = 330 ms (182 beats/min), tachycardia is detected and AMS is activated. All patients had clinical evaluation, 12-lead ECG, Holter monitoring, and exercise testing after implantation and every 3 months for 1 year. The results were compared with the data stored in the pacemaker memory: AMS episodes number; the histogram of the last 14 episodes; and atrial electrogram recording. Twenty-two Holter recordings in 13 patients showed PAF and in all of them AMS occurred simultaneously. AMS lasted between 10 seconds and 20 hours, and MAR ranged from 195-400 beats/min. No episode of PAF and no AMS were recorded in 39 Holter recordings in 22 patients. Appropriate AMS was confirmed in five patients by stored atrial electrogram and in nine by 12-lead ECG and pacemaker event markers. Mean atrial sensing was 2.13 +/- 1.04 mV during PAF and 3.18 +/- 1.46 mV during sinus rhythm. No PAF episode and no AMS were recorded during exercise testing. In conclusion, this new algorithm was very reliable, sensitive, and specific.

Implantation of a subcutaneous lead array in combination with a transvenous defibrillation electrode via a single infraclavicular incision

Occasional patients have excessive defibrillation energy requirements despite appropriate transvenous defibrillation lead position and modification of defibrillation waveform and configuration. Preliminary data suggest that use of subcutaneous defibrillation electrode arrays with nonthoracotomy systems is associated with a substantial reduction in defibrillation threshold. The current operative approach to subcutaneous lead array implantation involves the use of a separate left chest incision. We present two cases in which implantation of a subcutaneous lead array in combination with a transvenous defibrillation electrode was performed via a single infraclavicular incision and associated with a reduction in defibrillation threshold. Such an approach simplifies implantation and avoids the potential morbidity of the additional incision required of a left lateral chest approach.