The word(s) "heart" appears 213 time(s) in 195 verse(s) in Quran in Abdullah Yusuf Ali translation.

(151) And We had firmly established them in a (prosperity and) power which We have not given to you (ye Quraish!) and We had endowed them with (faculties of) hearing, seeing, heart and intellect: but of no profit to them were their (faculties of) hearing, sight, and heart and intellect, when they went on rejecting the Signs of Allah; and they were (completely) encircled by that which they used to mock at!

(152) And among them are men who listen to thee, but in the end, when they go out from thee, they say to those who have received Knowledge, "What is it he said just then?" Such are men whose hearts Allah has sealed, and who follow their own lusts.

(153) Those who believe say, "Why is not a sura sent down (for us)?" But when a sura of basic or categorical meaning is revealed, and fighting is mentioned therein, thou wilt see those in whose hearts is a disease looking at thee with a look of one in swoon at the approach of death. But more fitting for them-

(154) Do they not then earnestly seek to understand the Qur'an, or are their hearts locked up by them?

(155) Or do those in whose hearts is a disease, think that Allah will not bring to light all their rancour?

(156) Be not weary and faint-hearted, crying for peace, when ye should be uppermost: for Allah is with you, and will never put you in loss for your (good) deeds.

(157) It is He Who sent down tranquillity into the hearts of the Believers, that they may add faith to their faith;- for to Allah belong the Forces of the heavens and the earth; and Allah is Full of Knowledge and Wisdom;-

(158) The desert Arabs who lagged behind will say to thee: "We were engaged in (looking after) our flocks and herds, and our families: do thou then ask forgiveness for us." They say with their tongues what is not in their hearts. Say: "Who then has any power at all (to intervene) on your behalf with Allah, if His Will is to give you some loss or to give you some profit? But Allah is well acquainted with all that ye do.

(159) "Nay, ye thought that the Messenger and the Believers would never return to their families; this seemed pleasing in your hearts, and ye conceived an evil thought, for ye are a people lost (in wickedness)."

(160) Allah's Good Pleasure was on the Believers when they swore Fealty to thee under the Tree: He knew what was in their hearts, and He sent down Tranquillity to them; and He rewarded them with a speedy Victory;