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==The Normal ST segment== | ==The Normal ST segment== | ||
[[Image:changing_ST.png|thumb|ST changes occur when the endocardial and epicardial actionpotentials cesse to counterbalance each other | [[Image:changing_ST.png|thumb|ST changes occur when the endocardial and epicardial actionpotentials cesse to counterbalance each other]] | ||
The ''ST segment'' represents the ventricular repolarisation. Repolarisation follows upon contraction and depolarisation. During repolarisation the cardiomyocytes elongate and prepare for the next heartbeat. This process takes much more time than the depolarisation. Repolarisation is not passive elongation by stretch, it is an active process during which energy is consumed. On the ECG, the repolarisation phase starts at the junction, or ''j point'', and continues until the ''T wave''. The ST segment is normally at or near the baseline. | The ''ST segment'' represents the ventricular repolarisation. Repolarisation follows upon contraction and depolarisation. During repolarisation the cardiomyocytes elongate and prepare for the next heartbeat. This process takes much more time than the depolarisation. Repolarisation is not passive elongation by stretch, it is an active process during which energy is consumed. On the ECG, the repolarisation phase starts at the junction, or ''j point'', and continues until the ''T wave''. The ST segment is normally at or near the baseline. | ||