Porcine hearts are commonly used in cardiovascular research to simulate the size and the functional properties of the human heart. However, some important aspects, such as the differences between the electrophysiological properties of the left (LV) and right ventricle (RV) have not been characterised.Introduction
The purpose of this study was to investigate and compare electrophysiological properties of the porcine LV and RV at the multicellular level, using myocardial slices.Methods
Vibratome-cut myocardial slices (350 μm thick) were prepared from the sub-epicardial and mid-myocardial regions of the LV and RV of pig hearts.Methods
Slices were electrophysiologically assessed during electrical stimulation using a multi-electrode array (MEA) system. Extracellular field potentials, recorded from 60 MEA microelectrodes, were processed to measure field potential duration (FPD) — an index of action potential duration — and conduction velocity (CV). Frequency-dependent changes of FPD were assessed by pacing slices at 0.5, 1 and 2 Hz. To assess the effect of the direction of propagation on FPD and measure longitudinal and transverse CV, slices were paced at 1 Hz within or perpendicular to fiber orientation.Results
FPD was significantly shorter in slices from the RV versus slices from the LV when stimulated at 0.5 and 1 Hz, but was similar at 2 Hz (0.5 Hz: 295 ± 15 ms in RV, 354 ± 12 ms in LV, n=5, p < 0.05; 1 Hz: 273 ± 13 ms in RV, 341 ± 7 ms in LV, n=5, p < 0.05; 2Hz: 230 ± 11 ms in RV, 267 ± 15 ms in LV, n=5, p > 0.05). All slices displayed rate dependence of FPD, with FPD prolongation at lower stimulation frequency in both RV and LV slices (ANOVA, p < 0.05 and p < 0.01, respectively). FPD/pacing cycle length relationship was steeper in LV than RV (mean lengthening: 88 ± 3 ms in LV, 66 ± 4 ms in RV, n=4, p < 0.001).Results
FPD was independent from the direction of propagation in both RV and LV slices (RV: 266 ± 32 ms & 273 ± 26 ms, LV: 344 ± 18 ms & 359 ± 24 ms, during longitudinal and transversal pacing respectively).Results
Average CV was 37 ± 5 cm/s in RV (n=4) and 24 ± 4 cm/s in LV slices (n=4). Longitudinal CV was faster than transversal CV in RV and LV slices (RV: 74 ± 9 & 19 ± 3 cm/s; LV: 46 ± 14 & 14 ± 1 cm/s).Conclusions
We report significant electrophysiological differences between RV and LV in the pig heart, similar to that previously reported for the dog and human heart. These differences should be taken into consideration when assessing electrical remodelling and the effect of pharmacological drugs in porcine models of ischaemia and heart failure.