I solved it by doing this:
1- Created two vars to store the selected x and it’s value.
2- Created a function for the mouseover event in “seriesGroups” like this:
onChartMouseOver = function (evt) { lastElementIndex = evt.elementIndex; lastElementValue = evt.elementValue; },
3- Created a function for the click event of the whole component (which is triggered when the user clicks in any part of the chart, so it requires validation). From there I used the lastElementIndex and lastElementValue previously updated with the last mouseover event.
Hope it helps you.