1. What does it mean?
쫄깃하다 usually describes food with a pleasantly springy chew. Figuratively, especially in 심장이 쫄깃하다, it describes being kept in tense suspense by a close contest or an uncertain outcome.
Also written or said as jjolgithada
2. The nuance
A noodle review probably uses the literal food sense. A comment about the last minute of a match usually means the tension has you on edge, not that your heart physically changes texture.
3. Examples
“마지막 문제 정답을 기다리는 동안 심장이 쫄깃했어.”
Waiting for the answer to the last question was nerve-racking.
“결승전이 한 점 차로 끝나서 끝까지 쫄깃하더라.”
The final ended by one point and kept me on edge right to the end.
Sources
References support the meaning and usage. Example sentences are written for NoCapWiki.