AUTHOR AND EDITOR INFORMATION

Section 1 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Background

Crosstalk is defined as the inappropriate detection of a pacemaker-generated event in one channel by the sensing amplifier of the other channel that causes inhibition of the second channel's output. This is a complication of dual-chamber pacemakers.

Far-field sensing is a generic term used to refer to the oversensing of any electrical event that is not meant to be sensed. Oversensing in this case refers to the unintended detection by the pacemaker of any electrical complex including myopotential sensing, pacemaker lead fractures, and electromagnetic interference from appliances such as MRIs or microwave ovens.

Pacemakers are designed to recognize electrical activity at a preprogrammed amplitude, measured in millivolts, at which any electrical event will be sensed. The dual-chamber pacemaker equipped with a unipolar atrial lead will have a larger pacing spike than those with a bipolar lead; therefore, they will have more crosstalk events. At present, most dual-mode, dual-pacing, dual-sensing (DDD) pacemakers have 2 functions designed to prevent measures against crosstalk.

• The ventricular blanking (refractory) period (10-60 milliseconds [ms]) coincides with the atrial stimulus. This prevents inhibition of ventricular channel output from atrial spike detection.
• An additional backup system present in some pacemakers is known as ventricular safety pacing (VSP). During a VSP interval, any electrical stimulus received by the ventricular channel triggers a ventricular stimulus at the end of the VSP period. This occurs at a fixed interval, which is shorter than the preset atrioventricular (AV) delay (usually 90-120 ms).

Pathophysiology

Crosstalk depends on the amplitude of the atrial electrical stimulus and the sensitivity of the ventricular channel. This occurs only in dual pacemakers that are programmed for synchronous AV pacing. The atrial pacing spike is sensed by the ventricular channel as a ventricular event and causes inhibition of the ventricular pacing. This results in loss of left ventricular output, and in the case of a pacer-dependent patient, in syncope or asystole. In patients with intrinsic AV conduction, crosstalk inhibition of ventricular pacing output rarely causes severe symptoms.

Frequency

United States

In 166 clinical trials, only 106 patients with the same model pacemaker (Medtronic model 7006 DDD), were found to have a crosstalk rate of 1 per 59 (0.8%) at 110 beats per minute (bpm). At 130 bpm, the rate was 1 per 33 (3%), and no crosstalk was found at higher rates. Crosstalk inhibition is less common with bipolar atrial pacing than with unipolar atrial pacing. Crosstalk is a rare complication with the current DDD pacemakers.

CLINICAL

Section 3 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

History

Patients can present with dizziness, lightheadedness, palpitations, fatigue, shortness of breath, and near-syncope or syncope due to crosstalk. The patient pacemaker card should be reviewed in order to identify the manufacturer and to proceed with interrogation. Relevant pacemaker information includes the indication for the placement, date of placement, chamber type (single- or dual-chamber pacemaker), lead type (unipolar or bipolar), and current pacemaker programming.

Physical

The vital signs should be reviewed for signs of bradycardia, hypotension, and tachypnea. The lower heart rates for pacing are at 50-60 bpm and the high are generally at 100-140 bpm. In crosstalk, where there is inappropriate pacemaker inhibition, the rate will be below 50-60 bpm. The patient may have signs of congestive heart failure with elevated jugular venous pressure, crackles in the lung fields, a third heart sound, and peripheral edema.

DIFFERENTIALS

Section 4 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

WORKUP

Section 5 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Imaging Studies

• All patients with a possible pacemaker problem should have a chest radiograph with posteroanterior and lateral views in order to evaluate the lead positions. When a history is not available, the characteristic opaque markers of the pacemaker can help to identify the manufacturer and model number, whether it has a single or dual chamber, and whether the leads are unipolar or bipolar.

Other Tests

• A 12-lead ECG and a 30-second rhythm strip should be obtained quickly, because these can identify the atrium-paced spikes and the lack of ventricle-paced beats.
• The pacemaker should be interrogated by a cardiologist or pacemaker clinic personnel. Trained medical personnel can apply a magnet to a pacer in order to revert the device to the asynchronous mode and inhibit the sensing function. This practice ensures expedient ventricular pacing.

TREATMENT

Section 6 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Medical Care

Changing the refractory period and/or ventricular sensitivity is one approach to restoring proper function to a pacemaker that has developed crosstalk. A change in atrial output or pulse width may alleviate the malfunction, as well. Reprogramming atrial pacing to the bipolar mode, if possible, may alleviate the problem. Any changes in pacemaker settings should be made by a qualified individual.

• In symptomatic bradycardia or asystole, a magnet placed over the pulse generator should elicit asynchronous pacing, acutely restoring cardiac output until the proper pacemaker programmer and trained personnel are available.
• If these maneuvers do not restore hemodynamic stability, the advanced cardiac life support (ACLS) guidelines should be followed as indicated. This includes placement of an external or internal pacemaker, as required. The external pacemaker pads should be placed at least 10 cm from the internal pacemaker.

Consultations

A cardiologist consultant is necessary in any suspected pacemaker malfunction.

FOLLOW-UP

Section 7 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Further Inpatient Care

• A patient should be admitted only if a consultant is not available to reprogram the pacemaker. If the pacemaker has been interrogated and reprogrammed appropriately, then the patient can be sent home from the clinic, office, or emergency department.

MISCELLANEOUS

Section 8 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• Failure to quickly obtain a 12-lead ECG and a 30-second rhythm strip
• Failure to obtain chest radiographs with posteroanterior and lateral views in order to evaluate lead positions
• Failure to have the pacemaker interrogated by a cardiologist or trained pacemaker consultant
• Failure to admit a patient if a trained pacemaker consultant is not available to reprogram the pacemaker

REFERENCES

Section 9 of 9

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

• Combs WJ, Reynolds DW, Sharma AD. Cross-talk in bipolar pacemakers. Pacing Clin Electrophysiol. Oct 1989;12(10):1613-21. [Medline].
• Kersschot IE, Ortmanns P, Goethals MA. Atrial pacing bigeminy: a manifestation of crosstalk. Pacing Clin Electrophysiol. May 1985;8(3 Pt 1):402-7. [Medline].
• Sweesy MW, Batey RL, Forney RC. Crosstalk during bipolar pacing. Pacing Clin Electrophysiol. Nov 1988;11(11 Pt 1):1512-6. [Medline].
• Xie B, Thakur RK, Shah CP. Permanent cardiac pacing. Emerg Med Clin North Am. May 1998;16(2):419-62. [Medline].

Article Last Updated: Nov 1, 2005