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Assessment of Sarcoplasmic Reticulum Calcium Reserve and Intracellular Diastolic Calcium Removal in Isolated Ventricular Cardiomyocytes
Published on: September 18, 2017
New calculation of internal Ca(2+) recirculation fraction from alternans decay of postextrasystolic potentiation
1Department of Physiology II, Okayama University Medical School, Okayama, 700-8558 Japan. pepper@xa2.so-net.ne.jp
Insights
A new method accurately calculates the internal calcium (Ca2+) recirculation fraction (RF) in heartbeats without curve fitting. This approach improves reliability by avoiding sensitive decay constant calculations, offering a more stable assessment of cardiac function.
Area of Science:
- Cardiology
- Physiology
- Biophysics
Background:
- Previous methods for calculating internal calcium recirculation fraction (RF) relied on curve fitting the beat decay constant (tau(e)) from postextrasystolic potentiation (PESP) alternans decay.
- This fitting method is sensitive to noise in later postextrasystolic (PES) beats, leading to unreliable tau(e) values.
Purpose of the Study:
- To develop and validate a novel method for calculating RF that bypasses the need for tau(e) estimation.
- To enhance the reliability and reduce variability in RF measurements compared to existing curve-fitting techniques.
Main Methods:
- A new recurrence formula was derived to model PESP alternans decay directly from contractility data.
- This method calculates RF using the first four PES beats, eliminating the need for curve fitting or estimation of the beat decay constant.
- The new method was validated against the original fitting method using canine left ventricular preparations.
Main Results:
- The new method successfully calculated RF without requiring the beat decay constant (tau(e)).
- No significant difference was found in the mean RF values between the new method and the original fitting method.
- The new method demonstrated a significantly smaller variance in RF measurements, indicating improved reliability.
Conclusions:
- The novel recurrence formula provides a more reliable and robust method for calculating the internal calcium recirculation fraction (RF).
- This approach mitigates issues associated with noise sensitivity in previous curve-fitting techniques.
- The findings support the utility of this new method for accurate assessment of cardiac calcium handling and potentiation dynamics.
Abstract:
In our previous studies, we calculated the internal Ca(2+) recirculation fraction (RF) after obtaining the beat decay constant (tau(e)) of the monoexponential component in the postextrasystolic potentiation (PESP) of the alternans decay by curve fitting. However, this method sometimes suffers from the sensitive variation of tau(e) with small noises in the measured contractilities of the 5th and 6th postextrasystolic (PES) beats in the tail of the exponential component. We now succeeded in preventing this problem by a new method to calculate RF without obtaining tau(e). The equation for the calculation in the new method expresses an alternans decay of PESP as a recurrence formula of PESP. It can calculate RF directly from the contractilities of the 1st through the 4th PES beats without any fitting procedure. To evaluate the reliability of the new method, we calculated RF from the alternans decay of PESP of the left ventricle (LV) of the canine excised cross-circulated heart preparation by both the original fitting and the new method. Although there was no significant difference in the mean value of the obtained RF between these two methods, the variance of RF was smaller with the new method than with the original method. Thus the new method proved useful and more reliable than the original fitting method.
