An Assessment of the Relationship Between Regional Mechanical Myocardial Function and the Electrocardiogram

Abstract

It has previously been established that the left ventricle (LV) of the myocardium counter-rotates around its long axis on contraction. The apex and base rotate in opposite directions to create a wringing motion, resulting in LV twist. LV twist has been shown to vary with aerobic training status at rest. However the mechanisms that underpin this mechanical difference have yet been established, and the study of LV mechanics during exercise have seldom been explored. It has been previously suggested that neural activation could be responsible for this mechanical variation. In this study, LV twist mechanics and LV regional neural activity were assessed in 14 male university sports students (age: 20±1 years). Individuals firstly conducted a 2 max test, and were separated into two fitness groups post hoc by the median. Individuals were then examined at rest and during exercise (40% peak 2 power). At rest and during exercise, there were no significant differences in LV twist mechanics between fitness groups (P>0.05). However both basal and apical rotation, and basal and apical untwisting velocities were significantly higher from rest to exercise within both groups (P<0.05). There were no significant differences observed in neural activity at myocardial base and apex between fitness groups, or between rest and exercise (P>0.05). No significant correlations were found between myocardial mechanics and neural function in either group at rest or exercise (P>0.05). It was concluded that neural activity per se, is not an indicator of mechanical myocardial activity at base and apex, although there was some evidence to suggest a link may exist between cardiac mechanics and neural function. The findings suggest that the differences in LV mechanics could be caused by other underlying factors, one of these could be molecular adaptations