March 1, 1977Circulation Research
Length-dependent activation: its effect on the length-tension relation in cat ventricular muscle.
Population
Cat papillary muscles at 30 degrees C, bathed with Tyrode's solution containing 2.25 mM Ca2+
Design
Preclinical
Authors
Discussion
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Implication
Requires validation in intact hearts before clinical consideration; extends mechanistic insights on length-dependent coupling in animal models.
Key Points
- This study aims to explore how varying muscle length influences tension production in cat ventricular muscle.
- Examined cat papillary muscles in Tyrode's solution with 2.25 mM Ca2+ at 30 degrees C.
- Analyzed effects of stimulus frequency and paired stimulation on length-tension relation.
- Measured peak tension and rate of tension development across different muscle lengths.
- Pair pulse stimulation resulted in less decline in peak tension (DT) for muscle length changes compared to lower frequency stimulation.
- The steady state length-tension relation was steeper due to a delayed increase in DT after muscle stretch.
- Reduced calcium influx conditions prolonged the slow increase in DT and diminished its magnitude.
Structured PICO
P
Population
Cat papillary muscles at 30 degrees C, bathed with Tyrode's solution containing 2.25 mM Ca2+
I
Intervention
Various inotropic interventions (varying stimulus frequency, continual paired stimulation, stretching, reduction in bathing [Ca2+], verapamil)
O
Outcome
Shape of the steady state length-tension relation (peak tension developed [DT] and maximum rate of tension development [dT/dT])surrogate
The study demonstrates that the Frank-Starling relation (influence of muscle length on myocardial performance) is partly due to length-dependent activation of the contractile system via increased calcium influx.
Cite This Study
Lakatta et al. (1977) studied this question.