Double ventricular pacing in a patient with a "DDD" universal pacemaker

Ventricular cross stimulation in a dual chamber pacing system: phenomenon analysis

Seven cases of ventricular cross stimulation from a group of 23 patients implanted with DDD devices are presented. In two patients the phenomenon was observed at the moment of DDD programming at nominal values, and in five other patients it was reproduced by increasing the atrial output voltage up to ten volts. In all 23 patients cross stimulation disappeared permanently within 24 hours after implantation. From the onset of cross stimulation to its end, atrial and ventricular threshold voltages were unchanged, while the atrial and ventricular impedances significantly decreased. These results suggest that an important role in the phenomenon occurs by impedance variation at the interface between the pulse generator and body tissue.

A case of cross stimulation

Cross stimulation in a dual chamber pacing system, in which the atrial stimulus intermittently captured the right ventricle, occurred immediately after pacemaker implantation in a 71-year-old man. It was prevented temporarily by reducing the pacing rate so that P wave synchronous ventricular (VDD) pacing resulted and by reducing the output of the atrial circuit from 5 to 4 volts. Cross stimulation disappeared spontaneously 14 days after surgery.

DDD pacing: clinical considerations

DDD pacemakers offer a physiologic form of pacing for selected patients by incorporating atrioventricular synchrony over a wide range of atrial rates. Selection of a patient for DDD pacing necessitates a thorough knowledge of the individual functions of the DDD pacemaker, the limitations of DDD pacing, and the patient's own electrical and physiologic needs. Continuing developments in cardiac pacing include further reduction of the possibility of pacemaker-mediated tachycardia, increased matching to metabolic needs, and advancement of telemetric technology and electrophysiologic testing.

Atrial lead dislodgement with a DDD pacemaker

A 48-year-old man with previous aortic valve surgery and aortic root repair had a DDD pacemaker inserted (using transvenous leads) for the treatment of complete heart block. An atrial J active fixation electrode was used. Four weeks following implantation the patient returned with an unusual electrocardiographic rhythm demonstrating two separate QRS morphologies. Both PA and lateral chest x-ray failed to demonstrate a change in lead position. The MARKER CHANNEL of the DDD pulse generator confirmed that the alternating QRS morphologies were due to atrial lead dislodgement. Although uncommon, displacement of atrial active fixation leads may occur and lead to unusual electrocardiographic rhythms. Use of a MARKER CHANNEL may aid in the diagnosis.

Unusual presentation of DDD pacemaker system malfunction

A DDD pacemaker utilizing an atrial J electrode was implanted in a patient whose right atrial appendage had been removed 7 years prior during aortic valve replacement. Alternating QRS morphologies produced by pacemaker stimulus artifacts occurred as a consequence of atrial lead dislodgement. The screw-in atrial electrode has superior stability in patients with right atrial appendage removal; stability of the atrial J electrode cannot be obtained in such cases.

Automatic scanning extrastimulus pacemaker to treat ventricular tachycardia

Many investigators have reported the use of various permanent pacemaking modes in the long-term management of patients with recurrent ventricular tachycardia. The three general types of antitachycardic pacemakers are: (1) underdrive; (2) burst; and (3) scanning pacemakers. Such devices have been activated externally or have had automatic activation. Each antitachycardic pacemaking modality has known technical and physiologic limitations. A serious limitation of dual-demand underdrive pacemakers is that they are usually successful only for tachycardias with a rate below 160 bpm because a random stimulus is needed for conversion. Therefore, this modality is seldom useful in patients with symptomatic sustained ventricular tachycardia in which rates are generally greater than 160 bpm and/or hemodynamic compromise occurs rapidly. Although others have reported the successful use of burst pacemakers in the control of ventricular tachycardia, this technique may cause acceleration of ventricular tachycardia and induction of ventricular fibrillation. Programmable automatic scanning pacemakers have been used successfully to treat paroxysmal supraventricular tachycardia and have been used recently in combination with antiarrhythmic agents to control ventricular tachycardia. This report outlines the use of an automatic scanning pacemaker alone for the treatment of symptomatic ventricular tachycardia in a patient who was unable to tolerate conventional antiarrhythmic medications.

Data storage and retrieval by implantable pacemakers for diagnostic purposes

The functions of many of today's dual-chamber pacemakers are performed using custom microprocessors that are similar to those used in mainframe computers. The data storage and transmission capabilities of these microprocessor-controlled pacemakers can be used to record, process, and transmit information regarding the patient, pacemaker, or patient/pacemaker interaction. The limitations of such data processing systems depend upon (1) quantity and quality of incoming information, (2) software routines for data collection, and (3) the amount of available random access memory (RAM). Data obtained can be useful in patient management and follow-up, particularly in the areas of optimization of programming, monitoring of disease progression, assessment of pharmacologic therapy, and pacemaker troubleshooting. Anticipated advances in data collection capabilities will allow increasingly sophisticated analysis that will complement, and may in some cases, supplant the Holter monitor recording in evaluating some aspects of rhythm and/or pacemaker behavior in selected patients.