When Bhisma and the others on the side of Duryodhana blew their respective conchshells, there was no heart-breaking on the part of the Pandavas. Such occurrences are not mentioned, but in this particular verse it is mentioned that the hearts of the sons of Dhrtarastra were shattered by the sounds vibrated by the Pandavas' party. This is due to the Pandavas and their confidence in Lord Krsna. One who takes shelter of the Supreme Lord has nothing to fear, even in the midst of the greatest calamity.