Pacing and clinical electrophysiology : PACE
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Pacing Clin Electrophysiol · May 1988
Comparative StudyComparison of unipolar and bipolar active fixation atrial pacing leads.
The purpose of this investigation was to compare the acute pacing and sensing characteristics of a new bipolar active fixation atrial pacing lead with those of a unipolar atrial lead of similar design. Pacing threshold voltage and current, lead impedance, and atrial electrogram amplitude and slew rate were measured at the time of surgery in 28 consecutive patients undergoing DDD pacing system implantation. Eleven patients received a Medtronic 6957J-58 unipolar active fixation atrial lead and 17 patients were given a Medtronic 4016-58 bipolar lead. ⋯ The atrial electrogram exceeded 5 mV in 10 of 17 patients with the bipolar lead but zero of 11 with the unipolar lead. There was no significant difference in the mean slew rate of the leads (1.09 V/s bipolar versus 0.73 V/s unipolar; p = 0.18). Over a follow-up period of up to 10 months, all patients remained in either the DDD or DDI modes with no episodes of atrial sensing or pacing failure.(ABSTRACT TRUNCATED AT 250 WORDS)
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Pacing Clin Electrophysiol · Apr 1988
Comparative StudyComparison of the effects of right atrial, right ventricular apex and atrioventricular sequential pacing on myocardial oxygen consumption and cardiac efficiency: a laboratory investigation.
As the impact of cardiac pacing on myocardial energetics has not yet been established, this laboratory investigation was undertaken to evaluate the effects of right atrial (AP), right ventricular apex (VP) and atrioventricular sequential pacing (AVP) on cardiac energetics in a closed-chest model. Ninety-two pacing interventions were performed in ten anesthetized mongrel dogs with normal loading conditions and contractile states. The energetic effects of pacing were assessed in terms of myocardial oxygen consumption (MVO2), its hemodynamic determinants and cardiac efficiency. ⋯ AP has beneficial effects on cardiac energetics because it improves the relationship between mechanical performance of the heart and its energy requirements. AVP results in a higher efficiency than VP due to superior hemodynamics, despite MVO2 levels comparable to those of VP. The mechanism of energy waste with right ventricular apex pacing is probably related to an asynchronous contraction in the ventricular myocardium due to a nonphysiological spread of excitation.
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Pacing Clin Electrophysiol · Nov 1987
Letter Case ReportsPermanent pacemaker failure caused by wire fracture.
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To determine which cardiac chambers are stimulated during external cardiac pacing we performed external pacing in eight normal volunteers while recording the esophageal electrogram. All subjects demonstrated evidence of pacing, which was ventricular in each case. The atrium was frequently activated retrogradely during pacing. We conclude that external cardiac pacing selectively stimulates the ventricle and is thus not of value for noninvasive atrial pacing studies.