Simultaneous recording of monophasic action potentials and contractile force from the human heart

Franz, Michael R.; M, Schöttler; Schäefer, Jochen; Seed, W. A.

doi:10.1007/bf01477733

Cited by 22 publications

(7 citation statements)

References 8 publications

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“…Slow changes in a.p.d., similar to those reported here, have been observed in many other cardiac tissues (Boyett & Jewell, 1980) including human ventricular muscle (Franz, Sch6ttler, Schaefer & Seed, 1980). Boyett & Jewell (1978), for example, showed that when cat ventricular muscle is rested the action potential becomes progressively longer over a time course lasting several hundred seconds; this is similar to the behaviour exhibited by dog Purkinje fibres, and it is therefore possible that rate-dependent changes in Na-K-pump activity influence the duration of the action potential in other tissues.…”

Section: Incomplete Recovery Of the Plateau Conductancessupporting

confidence: 85%

Changes in the electrical activity of dog cardiac Purkinje fibres at high heart rates.

Boyett¹,

Fedida²

1984

The Journal of Physiology

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SUMMARY1. Rate-dependent changes in the electrical activity of dog Purkinje fibres have been studied. At high rates of stimulation the rate of repolarization is greater, the action potential is shorter, the maximum diastolic potential is increased, the pace-maker potential is reduced in amplitude, and on cessation of rapid stimulation there can be a suppression of spontaneous activity.2. After an increase of the stimulus frequency there is an abrupt shortening of the action potential, which can be attributed to incomplete recovery of the plateau currents; this is followed by a progressive decline in action potential duration over the next several hundred seconds. The factor responsible for the slow changes in duration could also be responsible for the accompanying increase in maximum diastolic potential because this develops along a similar time course.3. These slow changes in electrical activity have been investigated with the phase-plane technique. They are the result of an increase in the net outward current over a wide range of potentials (a-10 to -90 mV) during the repolarization phase of the action potential.4. In voltage-clamp experiments background current has been observed to be strongly rate dependent: the background current during a test voltage-clamp pulse after a train of action potentials is more outward at higher stimulus frequencies. When the frequency is increased, background current slowly becomes more outward over several hundred seconds, and this change therefore occurs along the appropriate time course to explain the slow alteration in electrical activity under these conditions. 5. The extra outward background current at high rates is relatively independent of membrane potential in the range from -110 to -40 mV (more circumstantial evidence indicates that this range may extend to at least + 10 mV); this potential dependence is similar to that of the Na-K-pump current (Eisner & Lederer, 1980). 6. Strophanthidin and ouabain, agents known to block the Na-K pump, alter both the changes in background current and the slow rate-dependent changes in electrical activity.7. Although after an increase in rate there is a gradual change in background current that can be explained by an increase in electrogenic Na-K-pump activity, the initial effect of switching rate is to produce a change in current that is consistent Kline & Kupersmith (1982) using K-sensitive microelectrodes. The effect on electrical activity of these changes is discussed.8. The pace-maker current, If, is unchanged at different rates, and the decrease in the amplitude of the pace-maker potential at high frequencies is therefore the result of the increase in membrane conductance at diastolic potentials produced by the pump-induced hyperpolarization.

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Section: Incomplete Recovery Of the Plateau Conductancessupporting

confidence: 85%

Changes in the electrical activity of dog cardiac Purkinje fibres at high heart rates.

Boyett¹,

Fedida²

1984

The Journal of Physiology

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“…MAPS were recorded using a modification of a newly designed contact-electrode recording technique (13). The electrophysiological principle underlying this technique is described elsewhere (16).…”

Section: Methodsmentioning

confidence: 99%

Mechanical restitution of isolated perfused canine left ventricles

Burkhoff

Yue²,

Franz

et al. 1984

American Journal of Physiology-Heart and Circulatory Physiology

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We measured cardiac mechanical restitution curves, which describe the time course of recovery of ventricular contractile strength following a steady-state beat. In the first series of experiments, we studied left ventricles that beat isovolumically throughout the experiment, allowing use of dP/dtmax as a reliable index of contractile strength independent of the influence of changing ventricular pre- and afterload. The commencement of mechanical restitution was found to be associated with the onset of electrical diastole; thereafter, contractile strength rose monoexponentially to a plateau that was maintained for test pulse intervals as long as 15 s. The time constant of restitution (typically 245 ms) was independent of priming frequency and ventricular volume. These findings were interpreted in terms of a model of intracellular calcium fluxes within the myocardial cells. In a second series of experiments, we measured mechanical restitution curves from isolated ventricles that ejected against a simulated arterial impedance system. Under this condition, we did not observe the monoexponential time course of mechanical restitution as was measured under isovolumic conditions. The differences between the mechanical restitution curves measured under isovolumic and ejecting conditions were attributed to the influences of changing hemodynamic conditions on dP/dtmax that caused it to be an unreliable index of contractile strength.

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“…While a close relationship between action potential duration and the resulting contractile force was documented decades ago [25], the dependence of atrial cell shortening on the plateau potential is less well appreciated in the literature. In ventricular voltage clamped myocytes, cell shortening is paralleled by the bell-shaped current-voltage relationship of I CaL , with low contraction amplitude at positive potentials of N 40 mV [26,27].…”

Section: Modulation Of Atrial Contractility By the Shape Of The Atriamentioning

confidence: 99%

Blockade of atrial-specific K+-currents increases atrial but not ventricular contractility by enhancing reverse mode Na+/Ca2+-exchange

Schotten

Haan

Verheule

et al. 2007

Cardiovascular Research

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Simultaneous recording of monophasic action potentials and contractile force from the human heart

Cited by 22 publications

References 8 publications

Changes in the electrical activity of dog cardiac Purkinje fibres at high heart rates.

Changes in the electrical activity of dog cardiac Purkinje fibres at high heart rates.

Mechanical restitution of isolated perfused canine left ventricles

Blockade of atrial-specific K+-currents increases atrial but not ventricular contractility by enhancing reverse mode Na+/Ca2+-exchange

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