C J Leeds | PubMed Health

PubMed1977

Fluoroscope-generated electromagnetic interference in an external demand pacemaker: report of a case.

Electromagnetic interference presented as inhibition and resetting of the demand circuitry of a ventricular-inhibited temporary external pacemaker in a 70-year-old man undergoing surgical implantation of a permanent bipolar pacemaker generator and lead. The arrhythmia was found to be due to oversensing of waveforms modulated to simulate myocardial potentials emitted by a faulty fluoroscopy unit used in the vicinity of external temporary transvenous pacing equipment. The documentation of this disruption of pacemaker rhythm reinforces the need for continuous monitoring of patients treated with external demand pacemakers and for the careful maintenance of all electrical equipment.

Aged↗

PubMed1976

Characteristics and coexistence of two forms of ventricular echo phenomena.

During the scanning of paced basic ventricular cycle lengths (V1V1) with extrastimulus method (V2) two forms of ventricular echo phenomena (Ve) were recognized. The Ve resulting from A-V nodal re-entry (VeAVN) occurred in 12 of 45 patients, from re-entry in the His-Purkinje system (Ve-HPS) in 20 of 45 patients, and simultaneous dual re-entry (Ve-AVN and Ve-HPS) occurred in five of 45 patients. The Ve-AVN (1) appeared at longer V1V2 intervals, (2) was dependent on retrograde A-V nodal conduction delay, (3) had normal QRS complexes and H-V intervals, and (4) did not occur when V2 blocked in the A-V node. (5) Ve-AVN had aberrant QRS complexes when preceded by Ve-HPS. The Ve-HPS (1) appeared at shorter V1V2 intervals, (2) was dependent upon retrograde conduction delay in the HPS, (3) its QRS morphology and axis orientation resembled V2, i.e., left bundle branch block pattern, when right ventricular apex was the site of stimulation, (4) persisted when V2 blocked in the A-V node and was abolished when V2 blocked below the bundle of His, and (5) rarely occurred in patients with pre-existing right bundle branch block. It is concluded that (1) at least two forms of Ve can result from induced premature ventricular beats, (2) Ve-HPS is more common than Ve-AVN in the presence of normal QRS complexes, and (3) coexistence of Ve-AVN and Ve-HPS can give rise to complex ECG pattern mimicking multiple multifocal premature ventricular beats.

Arrhythmias, Cardiac↗