Tell tale heart

Dr.Joshua was a young and famous neuro surgeon with hundreds of brain surgeries to his credit. One day he  was sitting in his study deeply immersed in thoughts. If one needed hundreds of Newtons, Curies and Einsteins in the world,all that is required is to tailor-make such brilliant brains; that is,identify the persons with very high IQs and culture their brain cells in the laboratory. Of course this is not going to be simple. But Dr.Joshua wanted to go ahead with his pet plan.

After sweating it out, the surgeon succeeded. The best brain had been developed surpassing his expectations. As no one dared to take a chance with the new brain, Dr.Joshua himself offered to undergo a brain transplant. It was a big success. The entire world was electrified. No wonder Dr.Joshua was identified to be very brilliant with the highest IQ. Several countries vied with one another to offer him citizenship. He was to be conferred the Nobel Prize in a weeks time.   

Three days passed. The next morning Dr.Joshua was found dead in his bed.The reason was the failure of the heart.

Was it that the best of the brains could not read the failing heart or the heart was beyond intelligence?