Measurement of the maximum rate of rise of the cardiac action potentialV max

1984 ◽  
Vol 22 (3) ◽  
pp. 275-276 ◽  
Author(s):  
R. M. McGillivray ◽  
R. W. Wald
Keyword(s):  
Maximum Rate ◽  
Cardiac Action ◽  
Maximum Rate Of Rise

Developmental changes in cardiac contractility in fetal and postnatal sheep: in vitro and in vivo

1984 ◽  
Vol 247 (3) ◽  
pp. H371-H379 ◽  
Author(s):  
P. A. Anderson ◽  
K. L. Glick ◽  
A. Manring ◽  
C. Crenshaw
Keyword(s):  
Maximum Rate ◽  
Diastolic Pressure ◽  
Systolic Pressure ◽  
Left Ventricular ◽  
Developmental Changes ◽  
Common Mechanism ◽  
Postextrasystolic Potentiation ◽  
Maximum Rate Of Rise

Developmental changes in contractility were sought in the fetal and postnatal sheep heart by using postextrasystolic potentiation and force, pressure, and wall-motion measures. Two different preparations were used, isolated myocardium and the chronically instrumented lamb. In the isolated muscle, the following increased significantly with age: force of contraction, the maximum rate of rise of force, and postextrasystolic potentiation. In the intact heart prior to birth [period of study, 20 +/- 4 (SD) days] heart rate (HR) fell significantly, and the following increased significantly: postextrasystolic potentiation [measured with the maximum rate of rise of left ventricular (LV) pressure (Pmax)], LV peak systolic pressure (LVP), end-diastolic dimension (EDD), end-systolic dimension (ESD), and aortic diastolic pressure. After birth, LVP, Pmax, HR, LVEDP, EDD, and ESD increased and postextrasystolic potentiation fell. The latter fall was not found in vitro and probably demonstrates a transient change in contractility, related to hormonal or neural stimulation. Over the subsequent postnatal days (6-122 days), HR fell while potentiation, EDD, and ESD increased significantly. Both in vitro and in vivo, the overall increase in postextrasystolic potentiation demonstrates a similar long-term change in contractility. The similarity of this change to that induced by mild hypertrophy suggests that development and mild hypertrophy alter myocardial contractility through a common mechanism.

Use of Magnetic Links to Measure the Maximum Rate-of-Rise of Lightning Currents

2007 ◽  
Vol 22 (4) ◽  
pp. 2445-2449 ◽  
Author(s):  
Wang Ju-feng ◽  
Qi Chong ◽  
Liang Xiao-bing ◽  
Che Yi-ying ◽  
Fan Li-li ◽  
...  
Keyword(s):  
Maximum Rate ◽  
Maximum Rate Of Rise

Development of a Rate Adaptive Pacemaker Based on the Maximum Rate-of-Rise of Right Ventricular Pressure (RV dP/dtmax)

1992 ◽  
Vol 15 (2) ◽  
pp. 219-234 ◽  
Author(s):  
TOM BENNETT ◽  
ARJUN SHARMA ◽  
RICHARD SUTTON ◽  
A. JOHN CAMM ◽  
MARK ERICKSON ◽  
...  
Keyword(s):  
Right Ventricular ◽  
Maximum Rate ◽  
Ventricular Pressure ◽  
Rate Adaptive ◽  
Maximum Rate Of Rise

The dependence of the maximum rate of rise of the action potential upstroke on membrane properties

1981 ◽  
Vol 214 (1194) ◽  
pp. 85-98 ◽  
Keyword(s):  
Action Potential ◽  
Maximum Rate ◽  
Sodium Current ◽  
Membrane Properties ◽  
Fractional Change ◽  
Sodium Conductance ◽  
Excitable Membranes ◽  
Real Relation ◽  
Voltage Clamping ◽  
Maximum Rate Of Rise

The maximum rate of rise of the action potential ( V̇ max ) is often used to study the maximum sodium conductance ( Ḡ Na ) of excitable membranes, by assuming that V̇ max is proportional to Ḡ Na . However, the real relation between V̇ max and Ḡ Na is uncertain. We use simple analytical descriptions of the membrane currents to investigate this relation. If (1) the sodium conductance is much greater than the non-sodium conductance of the membrane, (2) the sodium current is activated extremely quickly, and (3) the sodium current is inactivated extremely slowly, then V̇ max will indeed be proportional to Ḡ Na . However, if conditions (1) or (3) are not satisfied, the V̇ max – Ḡ Na relation will be non-proportional, such that a certain fractional change of Ḡ Na produces a larger fractional change of V̇ max . If condition (2) is not satisfied the V̇ max – Ḡ Na relation is distorted in the opposite direction, such that a certain fractional change of Ḡ Na produces a smaller fractional change of V̇ max . Measurements of V̇ max are usually performed in preparations where voltage clamping cannot be used to study Ḡ Na directly. However, voltage clamping is necessary to verify that conditions (1)–(3) are satisfied. The results of studies using V̇ max alone as a measure of Ḡ Na should be assessed with caution.

Effects of Divalent Cations on Spike Generation in the Longitudinal Somatic Muscle of the Earthworm

1970 ◽  
Vol 52 (1) ◽  
pp. 79-94
Author(s):  
Y. ITO ◽  
H. KURIYAMA ◽  
N. TASHIRO
Keyword(s):  
Membrane Potential ◽  
Maximum Rate ◽  
Calcium Concentration ◽  
Divalent Cations ◽  
Input Resistance ◽  
Ringer Solution ◽  
Membrane Potentials ◽  
Free Solution ◽  
Spike Generation ◽  
Maximum Rate Of Rise

Effects of various divalent cations on the spike-generation mechanism in the longitudinal muscle of the earthworm, Pheretima communissima, under sodium-free conditions were observed. 1. In the sodium-free solution the membrane was hyperpolarized from -35 mV. to -55 mV. and the input resistance of the membrane increased from 32 MΩ to 52 MΩ. The spike amplitude was greater in sodium-free solution than in Ringer solution. 2. The amplitude of the spike elicited by intracellular depolarizing currents in sodium-free solution was proportional to the external calcium concentration. The slope of the overshoot potential against tenfold change of the calcium concentration was 26 mV. Similar results could be observed with strontium. 3. The threshold membrane potentials for spike generation varied under various concentrations of calcium. Strontium had nearly the same effect as calcium on the threshold membrane potential. 4. The maximum rates of rise of the spike under various damped membrane potentials were measured in sodium-free solution. The maximum rates of rise of the spike showed sigmoidal curve against the changes of the membrane potential. The half-value of the inactivation curve was estimated to be -32 mV. 5. It was concluded that the spike was elicited by the inward movement of calcium ions, presumably not only in sodium-free solution but also in normal Ringer solution. 6. Strontium and barium ions also carried current during the active state of the membrane. 7. Barium, however, inhibited the potassium conductance of the membrane during the resting and active states, i.e. depolarized the membrane, increased the input resistance of the membrane and prolonged the falling phase of the spike. 8. Magnesium of itself could not elicit the spike in sodium-free solution but prevented spike generation by elevating the threshold membrane potential in the presence of calcium. In the presence of 10 mM Mg, the overshoot potentials recorded in the various concentrations of calcium were not affected, but the maximum rate of rise of the spike was reduced. 9. Cobalt and manganese elevated the threshold membrane potential without changing the resting membrane potential and prevented spike generation. Cobalt was more effective than manganese in preventing spike generations. Cobalt and manganese reduced the amplitude of the overshoot potential and the maximum rate of rise of the spike.

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