BACKGROUND: Optical mapping of cytosolic calcium transients in intact mammalian hearts is now possible using long-wavelength [Ca(2+)](i) indicators. We propose that beat-to-beat [Ca(2+)](i) transient alternans during ischemia may lead to spatial and temporal heterogeneity of calcium-activated membrane currents. METHODS AND RESULTS: To test this hypothesis, isolated rabbit hearts were loaded with the fluorescent [Ca(2+)](i) indicator, rhod-2 AM, and imaged at 300 frames/sec during blood-perfused ischemic trials. High-quality [Ca(2+)](i) transients were recorded in each of 8 hearts.[Ca(2+)](i) transient alternans was never present in control records but occurred in each of the hearts during ischemia, with onset after 2 to 4 minutes. Alternans was confined to circumscribed regions of the heart surface 5 to 15 mm across. Multiple regions of alternans were found in most hearts, and regions that were out of phase with one another were found in 6 hearts. Quantitative maps of alternans were constructed by calculating an alternans ratio. This ratio behaved as a continuous variable that reached a maximum value in the center of the regions with alternans. CONCLUSIONS: These results demonstrate marked spatial heterogeneity of the [Ca(2+)](i) transient during the early phase of ischemia, which could produce electrical instability and arrhythmias in large mammalian hearts.
BACKGROUND: Optical mapping of cytosolic calcium transients in intact mammalian hearts is now possible using long-wavelength [Ca(2+)](i) indicators. We propose that beat-to-beat [Ca(2+)](i) transient alternans during ischemia may lead to spatial and temporal heterogeneity of calcium-activated membrane currents. METHODS AND RESULTS: To test this hypothesis, isolated rabbit hearts were loaded with the fluorescent [Ca(2+)](i) indicator, rhod-2 AM, and imaged at 300 frames/sec during blood-perfused ischemic trials. High-quality [Ca(2+)](i) transients were recorded in each of 8 hearts.[Ca(2+)](i) transient alternans was never present in control records but occurred in each of the hearts during ischemia, with onset after 2 to 4 minutes. Alternans was confined to circumscribed regions of the heart surface 5 to 15 mm across. Multiple regions of alternans were found in most hearts, and regions that were out of phase with one another were found in 6 hearts. Quantitative maps of alternans were constructed by calculating an alternans ratio. This ratio behaved as a continuous variable that reached a maximum value in the center of the regions with alternans. CONCLUSIONS: These results demonstrate marked spatial heterogeneity of the [Ca(2+)](i) transient during the early phase of ischemia, which could produce electrical instability and arrhythmias in large mammalian hearts.
Authors: Lothar A Blatter; Jens Kockskämper; Katherine A Sheehan; Aleksey V Zima; Jörg Hüser; Stephen L Lipsius Journal: J Physiol Date: 2003-01-01 Impact factor: 5.182
Authors: Jong J Kim; Jan Němec; Rita Papp; Robert Strongin; Jonathan J Abramson; Guy Salama Journal: Am J Physiol Heart Circ Physiol Date: 2013-01-11 Impact factor: 4.733