Pacemaker systems as implantable cardiac rhythm monitors

Pacemaker diagnostics in atrial fibrillation: limited usefulness for therapy initiation in a pacemaker practice

AIM

We aimed to determine the practical value of pacemaker diagnostics for atrial fibrillation (AF) in an unselected general pacemaker practice, specifically workflow and initiation of anticoagulation or antiarrhythmic drug (AAD) therapy.

METHODS

We prospectively followed consecutive pacemaker interrogations over a period of 1 year to identify patients with AF (burden from 1% to 99%). We contacted referring physicians with AF details, and then determined whether the information resulted in therapeutic changes.

RESULTS

Of the 1,100 pacemakers interrogated, 728 were dual chamber (DDDs) with AF diagnostic capability. AF was recorded in 73 (10%) but seven had limited information, leaving 66 patients; of these, 42 (63%) patients were already anticoagulated and in five (7%) patients, anticoagulation had been stopped because of complications. Initial diagnosis of AF was made by the pacemaker in 17 patients (26% of 66; 2% of 728); four (6% of 66) patients were newly initiated on anticoagulation. Of the 66 patients, 17 patients were already on AADs; 49 (74%) had satisfactory rate control or had other issues; only two (3% of 66; 0.3% of 728) received new AADs.

CONCLUSIONS

Of 728 patients with DDD pacemakers, only 17 were newly discovered to have AF, and six (0.8%) had changes in medications based on the pacemaker data. Adding pacemaker-derived data to existing clinical information had little therapeutic impact, due to a combination of cumbersome workflow, and because AF was usually known to practitioners. Developments in automated monitoring systems may provide more accessible and therapeutically useful information.

The Effects of Ranolazine on Paroxysmal Atrial Fibrillation in Patients with Coronary Artery Disease: A Preliminary Observational Study

The impact of ranolazine, an anti-ishemic agent with antiarrhythmic properties, on paroxysmal atrial fibrillation (PAF) in patients with coronary artery disease (CAD) remains unclear. Pacing devices can be useful tools for disclosing even asymptomatic PAF. Purpose of this study is to assess the effect of ranolazine on atrial fibrillation (AF), in patients with CAD, PAF and a dual-chamber pacemaker. We studied 74 patients with CAD, PAF, and sick sinus syndrome or atrio-ventricular block, treated with pacemakers capable to detect PAF episodes. The total time in AF, AF burden, and the number of PAF episodes within the last 6 months before enrolment in the study, mean AF duration per episode, and the QTc interval were initially assessed. Subsequently, patients were randomized into additional treatment with ranolazine (375 mg twice daily) or placebo. Following six months of treatment, all parameters were reassessed and compared to those before treatment. Ranolazine was associated with shorter total AF duration (81.56±45.24 hours versus 68.71±34.84 hours, p=0.002), decreased AF burden (1.89±1.05% versus 1.59±0.81%, p=0.002), and shortened mean AF duration (1.15±0.41 hours versus 0.92±0.35 hours, p=0.01). In the placebo group no such differences were observed. In both groups, no significant differences in the number of PAF episodes and QTc duration were observed. We conclude that in patients with CAD and PAF, ranolazine reduces the total time in AF, AF burden, and mean AF duration. These findings may imply additional antiarrhythmic properties of ranolazine on atrial myocardium and might indicate the necessity of its use in ischemic patients with PAF.

MedMon: securing medical devices through wireless monitoring and anomaly detection

Rapid advances in personal healthcare systems based on implantable and wearable medical devices promise to greatly improve the quality of diagnosis and treatment for a range of medical conditions. However, the increasing programmability and wireless connectivity of medical devices also open up opportunities for malicious attackers. Unfortunately, implantable/wearable medical devices come with extreme size and power constraints, and unique usage models, making it infeasible to simply borrow conventional security solutions such as cryptography. We propose a general framework for securing medical devices based on wireless channel monitoring and anomaly detection. Our proposal is based on a medical security monitor (MedMon) that snoops on all the radio-frequency wireless communications to/from medical devices and uses multi-layered anomaly detection to identify potentially malicious transactions. Upon detection of a malicious transaction, MedMon takes appropriate response actions, which could range from passive (notifying the user) to active (jamming the packets so that they do not reach the medical device). A key benefit of MedMon is that it is applicable to existing medical devices that are in use by patients, with no hardware or software modifications to them. Consequently, it also leads to zero power overheads on these devices. We demonstrate the feasibility of our proposal by developing a prototype implementation for an insulin delivery system using off-the-shelf components (USRP software-defined radio). We evaluate its effectiveness under several attack scenarios. Our results show that MedMon can detect virtually all naive attacks and a large fraction of more sophisticated attacks, suggesting that it is an effective approach to enhancing the security of medical devices.

Incidence and predictors of asymptomatic atrial fibrillation in patients older than 70 years with complete atrioventricular block and dual chamber pacemaker implantation

AIM

To evaluate predictors of asymptomatic atrial fibrillation in patients older than 70 years with complete atrioventricular (AV) block, normal left ventricular systolic function, and implanted dual chamber (DDD) pacemaker.

METHODS

Hundred and eighty six patients with complete AV block were admitted over one year to the Sisters of Mercy University Hospital. The study recruited patients older than 70 years, with no history of atrial fibrillation, heart failure, or reduced left ventricular systolic function. All the patients were implanted with the same pacemaker. Out of 103 patients who were eligible for the study, 81 (78%) were evaluated. Among those 81 (78%) were evaluated. Eighty one (78%) patients were evaluated. Follow-up time ranged from 12 to 33 months (average ±standard deviation 23 ± 5 months). Primary end-point was asymptomatic atrial fibrillation occurrence recorded by the pacemaker. Atrial fibrillation occurrence was defined as atrial high rate episodes (AHRE) lasting >5 minutes. Binary logistic regression was used to identify the predictors of development of asymptomatic atrial fibrillation. Results. The 81 patients were stratified into two groups depending on the presence of AHRE lasting >5 minutes (group 1 had AHRE>5 minutes and group 2 AHRE<5 minutes). AHRE lasting >5 minutes were detected in 49 (60%) patients after 3 months and in 53 (65%) patients after 18 moths. After 3 months, only hypertension (odds ratio [OR], 17.63; P = 0.020) was identified as a predictor of asymptomatic atrial fibrillation. After 18 months, hypertension (OR, 14.0; P = 0.036), P wave duration >100 ms in 12 lead ECG (OR, 16.5; P = 0.001), and intracardial atrial electrogram signal amplitude >4 mV (OR, 4.27; P = 0.045) were identified as predictors of atrial fibrillation.

CONCLUSION

In our study population, hypertension was the most robust and constant predictor of asymptomatic atrial fibrillation after 3 months, while P wave duration >100 ms in 12-lead ECG and intracardial atrial signal amplitude were predictors after 18 months.

The role of pacemakers in the management of patients with atrial fibrillation

Pacemakers have an important role in the major strategies for the management of atrial fibrillation, rate control and rhythm control. Of all the current non-pharmacologic therapies for atrial fibrillation, the use of pacemakers impacts the largest number of patients. Pacemakers are used to facilitate medical management of atrial fibrillation with rate control agents and anti-arrhythmic drugs. Atrioventricular junction ablation in conjunction with pacemaker implantation can be an effective therapy for controlling a rapid ventricular rate during atrial fibrillation. The minimization of right ventricular apical pacing in patients with paroxysmal atrial fibrillation is an important objective. Cardiac resynchronization therapy devices are likely to be beneficial in select patients with chronic atrial fibrillation.

Long-term risk of recurrent atrial fibrillation as documented by an implantable monitoring device

OBJECTIVES

The present study determined the incidence and time course of atrial fibrillation (AF) recurrences in patients with a history of AF and fitted with an implantable monitoring device.

BACKGROUND

The long-term risk of undetected recurrence of AF in patients receiving stable antiarrhythmic therapy remains uncertain.

METHODS

In 110 patients with a class I indication for physiologic pacing and a history of AF, a pacemaker with dedicated functions for AF detection and electrogram storage was implanted, and antiarrhythmic drug treatment was optimized. Patients were regularly followed up with evaluation of AF-related symptoms, a resting electrocardiogram (ECG), and interrogation of device memory. The incidence of AF recurrences lasting >48 h in asymptomatic patients presenting in sinus rhythm (SR) at the respective follow-up visit constituted the primary end point of this prospective study.

RESULTS

During 19 +/- 11 months, 678 follow-up visits were performed. Atrial fibrillation was documented in 51 patients (46%) by ECG recording and in 97 patients (88%) by a review of stored electrograms (p < 0.0001). Device interrogation revealed AF recurrences lasting >48 h in 50 patients, 19 of whom (38%) were completely asymptomatic and in SR at subsequent follow-up. In 11 (16%) of 67 patients with device-confirmed freedom from AF for > or =3 months, AF lasting >48 h recurred subsequently.

CONCLUSIONS

This prospective study demonstrates a high incidence of recurrent AF despite optimized antiarrhythmic therapy. Of particular note, AF relapses >48 h remained totally asymptomatic in a significant proportion of patients. Freedom from AF for > or =3 months did not preclude subsequent long-lasting AF recurrence.