Clinical thresholds of endocardial cardiac stimulation: A long-term study

Furman, Seymour; Hurzeler, Philip; Parker, Bryan

doi:10.1016/0022-4804(75)90074-8

Cited by 59 publications

(16 citation statements)

References 3 publications

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“…In the model of a spherical electrode, the previous equation is written: I chronic = 4 r (ro + Imin acute 4 TT (18) That is, R = Imin chronic Imin acute (19) The same applies to voltage.…”

Section: Thickness Of Fibrosismentioning

confidence: 98%

Electrode‐Heart Interface: Definition of the Ideal Electrode

Ripart

Mugica

1983

Pacing Clinical Electrophis

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In dual-chamber pacing in order to maintain the advantages of small pulse generator size and volume, and increased longevity, it becomes necessary to reduce pulse generator output. This may be accomplished by optimizing the electrode-heart interface. New electrode designs may reduce polarization losses; perhaps even newer materials should be considered. The results of accumulated data must be applicable to long-term pacing.

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“…In the model of a spherical electrode, the previous equation is written: I chronic = 4 r (ro + Imin acute 4 TT (18) That is, R = Imin chronic Imin acute (19) The same applies to voltage.…”

Section: Thickness Of Fibrosismentioning

confidence: 98%

Electrode‐Heart Interface: Definition of the Ideal Electrode

Ripart

Mugica

1983

Pacing Clinical Electrophis

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“…As current density determines excitation threshold (Furman et al, 1975) Strewth-intemal curves bipolar and cathodal refractory periods equal up to 8 mA of stimulus current the minimum desirable ratio of anodal to cathodal surface area was calculated to be between 1-6 and 4-2. Another way of avoiding the problem of shorter bipolar refractory periods is to move the anode away from the ventricle (Preston, 1974), but this solution may cause problems related to the position of the indifferent terminal.…”

Section: Design Of Safer Pacemaker Systemsmentioning

confidence: 99%

Comparison of cathodal, anodal, and bipolar strength-interval curves with temporary and permanent pacing electrodes.

Mehra¹,

Furman²

1979

Heart

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suMMARY Acute animal experiments indicate that ventricular vulnerability to fibrillation or multiple premature contractions is greater during bipolar or anodal stimulation than with unipolar cathodal (with electrodes of equal cathodal and anodal surface area) because the anodal and bipolar absolute refractory periods are shorter, enabling easier excitation in the vulnerable period. To compare the relative safety of stimulation with various commercial electrodes, strength-interval curves were determined in patients during the initial period after electrode implantation (acute studies) and after a few years of pacing (chronic studies). In 9 of 10 acute studies in patients with permanent bipolar electrodes (anode surface area 4-4 times cathode) and in 9 of 10 chronic studies in patients with bipolar electrodes, the unipolar cathodal and bipolar refractory periods were equal. However, in 7 of 12 patients with temporary bipolar electrodes (equal anodal and cathodal surface areas) and in 2 out of 20 acute and chronic studies in patients with permanent bipolar electrodes, the bipolar refractory periods were significantly shorter than cathodal because of anodal stimulation at the proximal electrode. Under appropriate physiological conditions and competitive pacing, these patients would be more vulnerable to arrhythmias with bipolar stimulation than with unipolar cathodal. To decrease that risk, the anodal surface area should be 5 to 7 times the cathodal, or the anode should be removed from the ventricle, especially for temporary pacing in circumstances of high vulnerability to arrhythmias.

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“…This relationship between cathodal, anodal, and bipolar refractory periods can, however, alter when the surface areas of the anode and cathode are dissimilar since it is the current density that primarily determines excitation threshold. 11 It has been suggested that the two foci of excitation, which occur when the bipolar stimulus is above the unipolar cathodal and anodal thresholds, also may facilitate ventricular arrhythmias because of interaction between the two wavefronts. 9 Our results with low energy stimulation do not support such a contention.…”

mentioning

confidence: 99%

Vulnerability of the mildly ischemic ventricle to cathodal, anodal, and bipolar stimulation.

Mehra¹,

Furman²,

Crump³

1977

Circulation Research

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SUMMARY We studied the difference between myocardial vulnerability to arrhythmias caused by cathodal, anodal, and bipolar stimulation in 29 dogs with partial right coronary artery ocdusion. We used 2-msec duration stimuli of up to 8 mA to determine the ventricular vulnerable periods, their relationship to the refractory periods, and the fibrillation or multiple response thresholds for unipolar anodal and cathodal stimulation after two premature ventricular contractions. The vulnerable period for arrhythmias began at the end of the respective refractory periods and terminated at a specific time within the cardiac cycle. Within this period the arrhythmia and excitation thresholds were equal. Because shorter refractory periods were obtained with anodal stimulation than cathodal, the vulnerable periods for anodal stimulation were longer. This indicated that the vulnerable periods for bipolar stimulation also would be longer than for unipolar cathodal stimulation since bipolar and anodal refractory periods are equal when the cathode and anode are of similar surface area. Results from seven of the experiments showed that a dual focus of excitation, which can only occur with bipolar stimulation, did not make the ventricle more vulnerable to arrhythmias than did unifocal stimulation. These results indicate that the difference between the arrhythmia vulnerability to unipolar cathodal, anodal, and bipolar stimulation is dependent on the relationship between their excitability characteristics, i.e., their strength-interval curves.THE EXISTENCE of a brief period in the ventricular cycle during which electrical stimulation can induce arrhythmias such as ventricular fibrillation was demonstrated in animals by Wiggers and Wegria, 1 and often has been verified. -3The extensive clinical use of cardiac stimulation has made the circumstances under which such electrical stimulation may cause an arrhythmia of importance. Although most investigations indicate that the minimum energy required to precipitate ventricular fibrillation in the normal myocardium exceeds that delivered by a clinical cardiac pacemaker, there have been clinical reports of ventricular fibrillation and tachycardia associated with a pacemaker stimulus falling in the "vulnerable period" of the cardiac cycle. This suggests the presence of pathophysiological and pharmacological factors that lower the threshold to arrhythmias such as myocardial ischemia, sympathetic activity, and premature ventricular beats. 4~6Aside from these factors, the effects of electrode and stimulus characteristics on myocardial vulnerability are not yet well understood.A recent analysis of cases of ventricular fibrillation and tachycardia attributed to pacemaker stimuli found that most such arrhythmias arose in patients undergoing bipolar rather than unipolar cathodal stimulation. 7 In our own review of the literature, 8 we found 26 cases in which the initiation of ventricular fibrillation or tachycardia (defined as at least a run of 3 premature ventricular contractions) was illustrated. In ...

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Clinical thresholds of endocardial cardiac stimulation: A long-term study

Cited by 59 publications

References 3 publications

Electrode‐Heart Interface: Definition of the Ideal Electrode

Electrode‐Heart Interface: Definition of the Ideal Electrode

Comparison of cathodal, anodal, and bipolar strength-interval curves with temporary and permanent pacing electrodes.

Vulnerability of the mildly ischemic ventricle to cathodal, anodal, and bipolar stimulation.

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