Key result
In isolated canine right ventricular trabeculae, higher calcium, higher temperature, and lower stimulation rates produced less homeometric autoregulation or more anti-homeometric autoregulation.
The study demonstrates that homeometric autoregulation in isolated canine cardiac muscle is dependent on stimulation rate, calcium levels, and temperature, reconciling conflicting previous reports.
Should not guide clinical practice; leaves open condition-dependent autoregulation mechanisms in intact myocardium.
Pressure-induced homeometric autoregulation (HAR) has been demonstrated by many investigators in the mammalian ventricle; In isolated cardiac muscle, however, several investigators have reported the opposite effect (anti-HAR); namely, that the first beat after a transition from isotonic to isometric contraction is the most forceful, with a decline over several beats to a steady state. In the present study we find that trabeculae from the canine right ventricle demonstrate either HAR or anti-HAR, depending on the rate of stimulation, the calcium level, and the temperature. Higher calcium, higher temperature, and lower rate of stimulation produce either less HAR or more anti-HAR. When only temperature and rate of stimulation are varied, in each muscle there is a unique rate for each temperature above which HAR occurs and below which anti-HAR occurs.
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Donald et al. (1976) studied this question. Rate of stimulation, calcium level, and temperature was evaluated on Homeometric autoregulation (HAR) vs anti-HAR. In isolated canine right ventricular trabeculae, higher calcium, higher temperature, and lower stimulation rates produced less homeometric autoregulation or more anti-homeometric autoregulation.
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