I think you'll want to actually instantiate your sub items so you can assign the Text property. There may be a better solution but this works...
Code:
 Dim item1 As New ListViewItem("lstItem")
        For i As Integer = 1 To 5
            Dim si As New ListViewItem.ListViewSubItem()
            si.Text = "Qty" & i
            item1.SubItems.Add(si)
        Next
        ListView1.Items.Add(item1)