The evaluation of pulmonary vein isolation and wide-area left atrial ablation to treat atrial fibrillation in patients with implanted permanent pacemakers: the Previously Paced Pulmonary Vein Isolation Study.

BACKGROUND: The practise of catheter ablation for atrial fibrillation (AF) is increasing rapidly and is recommended as the treatment of choice in many patient subgroups. At present, the efficacy of this procedure has been assessed by means of electrocardiographic recording, intermittent Holter monitoring and evaluation of patient symptoms. We sought to evaluate the true efficacy of this procedure in patients with sophisticated permanent pacemakers capable of continuous long-term cardiac rhythm monitoring. METHODS: Twenty-five patients (aged 63.7 (9.4), 20 men), seven with persistent AF and 18 with prolonged paroxysmal AF, underwent a mean of 1.7 AF ablation procedures. All the patients had previously been implanted with a pacemaker or atrial defibrillator device. Data were downloaded from the device Holter before catheter ablation and at 2, 4, 6 and 8 months postprocedure(s). The primary outcome measure was AF burden. The secondary outcomes were patient symptom and quality-of-life measures. RESULTS: Initial AF burden was 43.8 (35.5)%. After catheter ablation(s), this was significantly reduced at 2 months to 23.8 (35.4)% (p=0.023), at 4 months to 21.4 (34.1)% (p=0.008), at 6 months to 14.5 (28.1)% (p=0.002) and at 8 months to 15.0 (29.4%) (p=0.003). Only nine (36%) of 25 patients demonstrated no recurrence of arrhythmia during follow-up completion, consistent with a long-term cure. Quality-of-life indices showed significant improvement after ablation. CONCLUSIONS: Catheter ablation for AF significantly improves patient symptoms and reduces AF burden after long-term beat-to-beat monitoring by implanted cardiac pacemaker and defibrillator devices. However, AF recurrence is common after these procedures.

Conventional and dedicated atrial overdrive pacing for the prevention of paroxysmal atrial fibrillation: the AFTherapy study.

AIMS: This investigation was conducted to determine the effectiveness of several conventional overdrive pacing modalities (single rate and rate responsive pacing at various lower rates) and of four dedicated preventive pacing algorithms in the suppression of paroxysmal atrial fibrillation (AF). METHOD AND RESULTS: In this multi-centre, randomized trial, 372 patients with drug-refractory paroxysmal AF were enrolled. Patients received a dual-chamber pacing device capable of delivering conventional pacing therapy as well as dedicated AF prevention pacing therapies and to record detailed AF-related diagnostics. The primary endpoint was AF burden, whereas secondary endpoints were time to first AF episode and averaged sinus rhythm duration. During a conventional pacing phase, patients were randomized to single rate or rate-responsive pacing with lower rates of either 70 or 85 min(-1) or to a control group with single rate pacing at 40 min(-1). In the subsequent preventive pacing phase, patients underwent pacing at a lower rate of 70 min(-1) with or without concomitant application of four preventive pacing algorithms. A substantial amount of data was excluded from the analysis because of atrial-sensing artefacts, identified in the device-captured diagnostics. In the conventional pacing phase, no significant differences were found between various lower rates and the control group receiving single rate pacing at 40 min(-1) or between single rate and rate-responsive pacing. Patients receiving preventive pacing with all four therapies enabled had a similar AF burden compared with patients treated with conventional pacing at 70 min(-1) (P = 0.47). CONCLUSIONS: The results do not demonstrate a significant effect of conventional atrial overdrive pacing or preventive pacing therapies. However, the observations provided important information for further consideration with respect to the design and conduct of future studies on the effect of atrial pacing therapies for the reduction of AF.

The safety and effectiveness of a nurse led cardioversion service under sedation.

OBJECTIVE: To assess the safety and effectiveness of nurse led elective cardioversion of atrial fibrillation under sedation. DESIGN: Prospective, longitudinal study. SETTING: Cardiac catheterisation laboratory and recovery area of a district general hospital. PATIENTS: 300 patients referred for elective cardioversion of persistent atrial fibrillation. INTERVENTIONS: Pre-procedure evaluations (history, physical examination, blood tests), consent, sedation administration, cardioversions, and post-procedure monitoring until discharge by advanced life support certified coronary care unit nurses trained in the techniques. A doctor was immediately available if required but not present. MAIN OUTCOME MEASURES: Success rates at discharge and at six weeks, energy delivered, number of shocks, dose of sedation, immediate, 24, and 48 hour patient perceptions, complications, waiting times, and cost effectiveness. RESULTS: Cardioversion success rate was 87% at discharge and 48% at six weeks. Mean (SD) cumulative energy was 497 (282) J and number of shocks 1.6 (0.8). Mean (SD) dose of sedation was 23 (9) mg intravenous diazepam. No patient required reversal of sedation, airway support, or medical intervention. Ninety eight per cent of patients had no pain or recall of the procedure. Four patients who were adequately anticoagulated experienced embolic phenomena. Ninety eight per cent of patients would repeat the procedure if necessary. Without requirement for a physician or anaesthetist, waiting times for elective cardioversion fell from three months to under four weeks. There was a significant reduction in the estimated cost of the procedure from 337 pounds sterling with general anaesthesia to 130 pounds sterling with nurse led sedation and cardioversion (p < 0.001). CONCLUSION: With appropriate training, a nurse led cardioversion service with sedation is safe, effective, well tolerated, and cost efficient.

Situs inversus and acute coronary syndrome.

Dextrocardia is a rare clinical phenomenon with a reported incidence of one in 10 000. Consequently, acute coronary syndromes in such patients are rare. When chest pain occurs in this setting, it is important to be aware of the unique problems that may occur if coronary intervention is contemplated. Previous case reports have shown successful attempts at reperfusing one coronary artery percutaneously. In this case, coronary stents were successfully deployed in two vessels of a man with situs inversus, which has not been reported before. Additionally, the angiographic results that followed from successful intervention did not produce the expected haemodynamic and electrocardiographic changes.

The clinical and electrophysiological implications of asymptomatic atrial fibrillation.

Atrial fibrillation (AF) is the commonest arrhythmia encountered in clinical practice and is frequently associated with significant symptoms. Asymptomatic AF may also increase the risks of heart failure, thromboembolism and cardiomyopathy but its prevalence is significantly underestimated by routine surveillance methods. The development of long-term external monitors and implantable devices has offered a new insight into the true prevalence of asymptomatic AF. Similar management strategies should be applied to both symptomatic and asymptomatic patient groups and anticoagulation should be continued indefinitely in those with a history of AF and risk factors for thromboembolism. Enhanced detection of clinically silent AF could improve outcomes but the resource implications will be significant.

Atrial fibrillation storms.

Evolving pacemaker and device technology now allows the onset pattern of arrhythmias to be identified. It is recognised that some cardiac arrhythmias have a circadian pattern of onset and that ventricular arrhythmias can occur in clusters of electrical storms. The long-term follow-up of patients with an atrial defibrillator suggests that in some patients persistent atrial fibrillation recurrences are not random, but can occur in clusters of 'atrial fibrillation storms'. A case report is used to demonstrate this newly recognised phenomenon.

Quality of life after use of the patient activated atrial defibrillator.

The aim of the study was to evaluate the effects of long-term use of the patient-activated atrial defibrillator for recurrent persistent atrial fibrillation (AF) on quality of life (QOL). Fifteen patients were implanted with the Medtronic Jewel AF 7250 device (dual chamber atrial and ventricular defibrillator) for AF only. AF recurrences were treated by out-of-hospital patient-activated atrial defibrillation shocks following the self-administration of oral sedation. QOL was assessed at pre-implant and up to one year with SF36, symptom checklist and HADS questionnaires. A total of 238 (median 10) out-of-hospital patient-activated atrial defibrillation shocks were performed. The SF36 demonstrated a trend toward improvement over the 12-month period compared with baseline values. There was no significant change in the symptom frequency or severity scores. Pre-implant levels of both anxiety and depression were within the predefined range of normality (6 +/- 3 and 3 +/- 2, respectively) and no significant change was seen at 6 months (5 +/- 4 and 3 +/- 3) or 12 months post implant (5 +/- 4 and 2 +/- 2, respectively). After one year of follow-up, 13 (87%) patients said they would have the device implanted again (two were undecided). The study demonstrates that patient-activated atrial defibrillation is a well tolerated therapeutic strategy for maintaining sinus rhythm.

The effect of endocardial defibrillator shocks on basic atrial electrophysiology in man. Is post cardioversion atrial electrical 'remodelling' artefact?

AIMS: To determine the effect of an endocardial DC shock on the basic electrophysiology of the human atrium if delivered in sinus rhythm. METHODS AND RESULTS: A 5J endocardial R wave synchronized DC shock was delivered in 10 patients in stable sinus rhythm during ICD implantation for ventricular arrhythmias. There was no prior history of atrial fibrillation. Monophasic action potential duration (APD) and atrial effective refractory periods (AERP) were evaluated before, 1 min post DC shock, and 15 min post shock. These parameters were assessed at basic cycle lengths and at atrial paced cycle lengths of 600 ms and 400 ms at two right atrial sites; mid lateral right atrial wall (MRLA) and the right atrial appendage (RAA). There were no significant differences in APD 90, AERP or atrial refractory dispersion at any site or drive cycle length before, immediately after or 15 min after shock delivery. CONCLUSIONS: There are no significant changes in basic electrophysiological parameters following a DC shock delivered in sinus rhythm in patients with no prior history of atrial fibrillation. This suggests that atrial electrical remodelling occurs as a result of atrial fibrillation and is unrelated to shock artefact.

Diazepam or midazolam for external DC cardioversion (the DORM Study).

AIMS: To compare the clinical efficacy and tolerability of two intravenous sedatives for physician-led DC cardioversion of atrial arrhythmias. METHODS AND RESULTS: One hundred and forty-one patients attending for elective DC cardioversion of atrial arrhythmias were randomized to intravenous midazolam or diazepam. Sedation was administered using titration protocols. Procedure times, operator satisfaction scores and adverse events were documented. The patients immediate, 24- and 48-h recall and awareness of after-effects were obtained from questionnaires. Seventy-one patients received midazolam (mean 12.5 mg) and 70 patients received diazepam (mean 28.1 mg). There were 16 minor adverse events with midazolam (20% hypotension, 3% oxygen desaturation) and nine with diazepam (7% hypotension, 6% required additional analgesia), P = 0.14. There were no major adverse events. Sedation time was 5.0 +/- 3.4 min for midazolam and 6.5 +/- 3.4 min for diazepam (P = 0.0016). Patients awoke 77 +/- 46 min post-sedation with midazolam and 39 +/- 24 min with diazepam (P < 0.0001). There was no recall of the procedure at 48 h and no difference in awareness of after-effects between the two groups at 24 or 48 h, P = ns. CONCLUSION: Physician-led cardioversion of atrial arrhythmias using intravenous sedation is effective and well tolerated. Sedation with diazepam was associated with fewer minor adverse events and a quicker recovery time than midazolam.

Effect of atrial antitachycardia pacing treatments in patients with an atrial defibrillator: randomised study comparing subthreshold and nominal pacing outputs.

OBJECTIVE: To assess the true efficacy of antitachycardia pacing on spontaneous persistent atrial fibrillation in patients with an implanted atrial defibrillator, by comparing the effects of nominal pacing treatment with subthreshold pacing treatment. DESIGN: The effects of antitachycardia pacing and burst 50 Hz atrial pacing on spontaneous atrial arrhythmias were evaluated six months after implantation of a Medtronic Jewel AF((R)) atrial defibrillator. SETTING: Cardiology department in a district general hospital. PATIENTS: 15 patients with persistent atrial fibrillation. INTERVENTIONS: Patients were randomised to either "nominal" output pacing treatment or surface ECG and endocardial electrogram proven subthreshold "sham" pacing treatment for three months, and then crossed over to the alternative treatment for a further three months. RESULTS: During the nominal output phase, 31 episodes of atrial fibrillation were treated with 53 bursts of 50 Hz pacing, 98 sequences of ramp atrial pacing, and 61 sequences of burst atrial pacing. Atrial fibrillation was not pace terminated during any episode. Thirty one episodes of atrial tachycardia were treated with 19 bursts of 50 Hz atrial pacing, 103 sequences of ramp atrial pacing, and 38 sequences of burst atrial pacing. Termination of atrial tachycardia was observed in 17 episodes. During the "sham" pacing period, no episodes were terminated by any pacing treatment. CONCLUSION: Atrial antitachycardia pacing treatments are ineffective at terminating persistent atrial fibrillation but may be useful in terminating episodes of atrial tachycardia or flutter, thus reducing the burden of arrhythmia.

What is the optimal electrode configuration for atrial defibrillators in man?

AIMS: To compare the atrial defibrillation threshold (DFT) for two electrode configurations in patients with drug refractory persistent atrial fibrillation (AF). METHODS AND RESULTS: 11 patients, 73% male, mean age 60.9 (range 38 to 83), underwent implantation of a Medtronic Jewel AF dual chamber defibrillator (model 7250). A step-up atrial DFT was performed in a randomized sequence for two electrode configurations: (1) Right atrial to distal coronary sinus electrode (RA > CS) and (2) defibrillator can to right ventricular and right atrial electrodes (CAN > RV + RA). The RA > CS configuration restored SR in 10 patients (91%). The CAN > RA + RV configuration restored SR in four patients (36%). The mean atrial DFT was significantly lower for the RA > CS than CAN > RA + RV configuration (10 +/- 7 Joules vs 25 +/- 6 Joules), P < 0.01. At 3 months post implantation, AF was reinduced and the protocol was repeated for the optimal electrode configuration. There was no significant difference in the atrial DFT compared with that at implant. CONCLUSION: The right atrium to coronary sinus electrode configuration significantly reduces the atrial DFT. The atrial DFT also remains stable at 3 months post-implantation. Patients with persistent AF undergoing insertion of an atrial defibrillator should have a coronary sinus electrode implanted.

Clinical experience with a dual-chamber implantable cardioverter defibrillator to treat atrial tachyarrhythmias.

INTRODUCTION: This study evaluated the safety and efficacy of a new dual-chamber implantable cardioverter defibrillator (ICD) to detect and treat atrial tachyarrhythmias in patients with drug-refractory atrial fibrillation (AF) and no indication for a ventricular ICD. METHODS AND RESULTS: A dual-chamber ICD (Medtronic 7250 Jewel AF) was implanted in 144 of 146 patients. The device discriminates atrial tachycardia from AF based on cycle length and regularity, and uses atrial overdrive pacing as well as shocks to terminate tachyarrhythmia episodes. Patients were followed for an average of 12.6+/-6.2 months. Use of antiarrhythmic drugs was 63% at baseline and did not change over time. Kaplan-Meier estimates of 12-month complication-free survival, device therapy survival, and patient survival were 85%, 91%, and 98%, respectively. Positive predictive accuracy of spontaneous atrial tachyarrhythmia detection was 99%, while atrial overdrive pacing and shocks terminated 40% and 87% of treated episodes, respectively. Median duration of successfully treated episodes was 8.9 minutes versus 144 minutes for the therapy failures. There was no reduction in the use of patient-activated shock therapy over time; at the 12-month follow-up evaluation, 94% of patients were in sinus rhythm. Ventricular tachyarrhythmias (67 episodes) were detected and appropriately treated in 7.6% of patients. CONCLUSION: This dual-chamber ICD appears to be safe and well tolerated in patients with drug-refractory symptomatic atrial tachyarrhythmias. The device, used in combination with drugs, effectively treats atrial tachyarrhythmias with pacing and/or shock therapies and decreases the median episode duration. In addition, the device protects from ventricular tachyarrhythmias in patients with AF and structural heart disease.

Recent advances in the non-surgical management of atrial fibrillation.

Atrial fibrillation is the commonest clinical arrhythmia, and is associated with significant morbidity and mortality. The treatment of choice is to restore and maintain sinus rhythm. Although certain antiarrhythmic drugs are more effective than placebo in maintaining sinus rhythm, recurrence of atrial fibrillation post cardioversion remains common. The use of antiarrhythmic drugs can be associated with serious adverse effects due to their negative inotropic and proarrhythmic effects. Radiofrequency ablation of the AV junction is a safe and effective palliative treatment option in patients who have failed drug therapy. Ventricular rate control without the need for permanent pacing can be achieved by AV nodal modification using radiofrequency energy. There is also interest in the role of catheter ablation as a possible curative procedure for atrial fibrillation. Atrial pacing can reduce the incidence of atrial fibrillation in certain subgroups of patients. Finally, low energy intracardiac atrial defibrillation has been shown to be feasible in humans.

Alterations in atrial electrophysiology associated with chronic atrial fibrillation in man.

BACKGROUND: The purpose of this study was to determine the changes in atrial electrophysiology associated with chronic persistent atrial fibrillation in man. METHODS AND RESULTS: Atrial monophasic action potential duration at 90% repolarization and the effective refractory period were measured in 13 patients with chronic persistent atrial fibrillation after low-energy endocardial cardioversion, and compared to eight controls without a history of atrial fibrillation. Measurements were made at the right atrial appendage and midlateral right atrial wall at basic, 600 ms and 400 ms drive cycle lengths. In control patients, the effective refractory periods were significantly longer at the atrial appendage than the lateral wall at 600 ms (right atrial appendage 265 ms, midlateral right atrial wall 228 ms, P<0.05), and 400 ms cycle lengths (right atrial appendage 270 ms, midlateral right atrial wall 218 ms, P<0.05), but this was not evident in patients with atrial fibrillation. The monophasic action potentials and effective refractory periods at both atrial sites were shorter in the atrial fibrillation patients compared to controls; however, only the effective refractory periods at atrial appendage at 600 ms (atrial fibrillation 210 ms, controls 265 ms, P<0.001), and 400 ms cycle lengths (atrial fibrillation 200 ms, controls 270 ms, P>0.001) reached statistical significance. Effective refractory period dispersion was significantly greater in controls than in patients with atrial fibrillation (cycle length 600 ms: controls 36, atrial fibrillation 13, P=0.01; cycle length 400 ms: controls 54, atrial fibrillation 18, P<0.01). CONCLUSIONS: In patients without a history of atrial fibrillation, the refractory period at the right atrial appendage is significantly longer than at the midlateral right atrial wall. This 'normal' pattern of atrial refractory dispersion is lost in patients with chronic persistent atrial fibrillation, with marked shortening of the effective refractory period at the right atrial appendage. This may explain the high risk of recurrence of atrial fibrillation following successful electrical cardioversion.

Prediction of maintenance of sinus rhythm after cardioversion of atrial fibrillation by analysis of serial signal-averaged P waves.

After cardioversion from atrial fibrillation (AF) many patients develop early recurrence of the arrhythmia. While these patients may be appropriate for immediate prophylaxis against AF recurrence their identification at the time of cardioversion is not possible. Since the signal-averaged P wave (SAPW) is abnormal in individuals with atrial arrhythmia, we assessed its utility for predicting early AF recurrence after cardioversion. Seventy-five cardioversions in 31 patients were evaluated. The mean age was 59 (range 28-79) years; 26 were male. Fifty-eight cardioversions were internal using low energy biphasic DC shocks delivered via electrodes placed in the right atrial appendage and coronary sinus. P wave specific signal averaging was performed at 3 and 24 hours after each cardioversion to estimate filtered P wave duration and energy from 20, 40, and 60 to 150 Hz. Follow-up was by regular clinic visits and transtelephonic ECG monitoring. Early recurrence of AF (prospectively defined as sinus rhythm duration < 1 week) occurred after 30 cardioversions. No differences were found in any P wave variable measured at 3 hours between these cardioversions and those that resulted in a longer duration of sinus rhythm. Paired 3- and 24-hour signal-averaged data were available in 47 cardioversions. There were significant falls in P wave energy from 3 to 24 hours after 31 cardioversions that resulted in sinus rhythm for > 1 week, (P40: 3 hours 11.2 [+/- 1.5] micro V2.s, 24 hours 8.6 [+/- 1.2] micro V2.s, P < 0.001), but not following the 16 after which AF returned within 1 week (P40: 3 hours 9.0 [+/- 1.2] micro V2.s, 24 hours 8.5 [+/- 1.2 micro V2.s, P = NS). A fall in P40 of > 25% had a positive predictive accuracy for maintenance of sinus rhythm of 87%; negative predictive accuracy was only 37%. Similar falls in P wave energy occurred after cardioversions that resulted in longer term (> 4 weeks) sinus rhythm, but not in those that did not. However, the predictive accuracy of a fall in P40 was less (positive predictive accuracy 38%, negative predictive accuracy 62%). Patients with relapsing permanent AF who remain in sinus rhythm for at least 1 week after cardioversion show a fall in P wave energy within the first 24 hours. However, in these patients the technique does not predict recurrent AF within 1 week nor sinus rhythm > 4 weeks. These observations suggest persistent disordered atrial activation as a mechanism for early recurrence of AF after cardioversion.

Is mode switching beneficial? A randomized study in patients with paroxysmal atrial tachyarrhythmias.

OBJECTIVES: We sought 1) to compare three pacing modalities-DDDR with mode switching (DM), DDDR with conventional upper rate behavior (DR) and VVIR (VR)-in patients with a history of atrial tachyarrhythmias, and 2) to assess the efficacy of six mode-switching algorithms. BACKGROUND: A history of atrial tachyarrhythmias has been a relative contraindication to dual-chamber pacing. Several mode-switching algorithms have recently been developed to prevent rapid tracking of atrial tachyarrhythmias. METHODS: Forty-eight patients (mean age 64 years, 58% male) with a history of atrial tachyarrhythmias and heart block had a DM pacemaker implanted. Pacemakers were programmed to DM, DR and VR modes for 4 weeks each in a randomized crossover design. All subjects used a patient-activated electrocardiographic (ECG) recorder throughout the study and additionally underwent ambulatory ECG monitoring and a treadmill exercise test in each mode. They completed three symptom questionnaires at the end of each pacing period. At the end of the study, patients chose their preferred pacing period. RESULTS: DM was significantly better than VR mode objectively (exercise time DM 8.1 min, VR 7.0 min, p < 0.01) and subjectively (perceived well-being DM 69, VR 51, p < 0.001; functional class DM 2.2, VR 2.5, p < 0.05; subjective symptom score DM 21.2, VR 26.8, p = 0.01). Patient-perceived well-being was significantly better with DM than with DR mode (DM 69, DR 60, p = 0.02). DM mode was the preferred pacing period (DM 51%, DR 14%, VR 14%). Early termination of pacing because of adverse symptoms was requested by 33% of patients during VR, 19% during DR but only 3% during DM mode. A higher proportion of patients with a fast mode-switching device preferred DM mode (fast 55%, slow 49%), whereas no patients with a fast mode-switching device chose VR as the preferred mode (fast 0%, slow 19%). In the subgroup of patients who had had atrioventricular node ablation, DM was also preferred to VR mode (DM 53%, VR 27%). Overall, there were only two cases of inappropriate mode switching and one case of inappropriate tracking of an atrial tachyarrhythmia. CONCLUSIONS: DM is the pacing mode of choice of patients with paroxysmal atrial tachyarrhythmias. With optimal programming, inappropriate mode switching and tracking of atrial tachyarrhythmias was very uncommon.

Ambulatory patient-activated arrhythmia monitoring: comparison of a new wrist-applied monitor with a conventional precordial device.

A wrist-applied transtelephonic device (WrTTD) and a precordial (PrTTD) patient-activated transtelephonic electrocardiographic (ECG) recorder were compared objectively (quality of ECG traces) and subjectively (device preference) in a prospective randomized crossover study of 24 patients. All underwent cardioversion for chronic atrial fibrillation and were then randomized to each device for 1 month. The ECG traces were sent weekly with additional traces if symptomatic. Self-administered questionnaires were completed after 1 month with each device, and the first five telemetered ECG traces for each patient were blindly assessed by two experienced cardiologists. Although the QRS complexes were smaller with the WrTTD (P < .001), the quality of the traces was similar. In particular, there was no significant difference in number of nondiagnostic traces, ability to detect atrial activity, degree of baseline fluctuation, or amount of artifact. Overall, patients preferred the PrTTD (P = .02). Patients found the PrTTD easier to use (P = .007) and were able to apply it more rapidly (P = .02). The quality of ECG traces obtained from the upper limbs by using a wrist-applied transtelephonic device was concluded to be comparable with those obtained by direct precordial application. In order to increase patient acceptability of the former, further improvements to simplify its operation are necessary.

Dual sensor VVIR mode pacing: is it worth it?

Dual sensor ventricular demand rate responsive (VVIR mode) pacing was compared with single sensor rate responsive pacing to assess whether this new development should be more widely incorporated in modern pacemaker devices. A within patient randomized, double-blind crossover study involving ten patients, mean age 67.4 years (70% male), had Medtronic Legend Plus dual sensor VVIR pacemakers implanted for high grade AV block and chronic or persistent paroxysmal atrial fibrillation. Performance values were compared to 20 healthy control subjects of a similar age and gender. Patients were both subjectively and objectively assessed after 2 weeks of out-of-hospital activity in VVIR mode (minute ventilation sensing), VVIR mode (activity sensing), VVIR mode (dual sensor), and VVI mode (no rate response). All patients were assessed for subjective preference for, and objective improvement in, any pacing modality as assessed by standardized daily activity protocols and graded exercise treadmill testing. Subjective perception of exercise capacity and functional status was significantly lower in VVI mode (P < 0.05) compared to any of the VVIR modes, which did not differ. After completion of the study 70% of patients chose VVIR as their preferred mode, with 30% expressing no preference. Forty percent preferred activity sensor VVIR mode pacing, 30% preferred dual sensor VVIR mode pacing, and 70% found either dual sensor VVIR mode, minute ventilation sensor VVIR mode, or both modalities least acceptable. No patient found activity sensing VVIR mode least acceptable. Graded treadmill testing revealed significantly lower exercise tolerance during VVI mode pacing (P < 0.01) compared to the VVIR modalities, which did not differ. Overall, chronotropic response was best with dual sensor pacing during standardized daily activity protocols and during the standard car journey. The data from this study suggest that there is no marked clinical advantage obtained from the use of dual sensor devices over current activity sensing ventricular demand rate responsive pacemakers, but with the probable added disadvantages of increased size, complexity, cost, and decreased longevity.