The dissection of the heart especially since the prime minister was undergoing a second bypass was listed by one of the surgeons as among the most complicated part of the operation at All India Institute of Medical Sciences on Saturday.

On being asked which was the most complicated part of the operation, Dr Pradyot Kumar Rath, one of the cardiac surgeons from Asian Heart Insitute, Mumbai [Images], said, "It is always the dissection of the heart. Because it was the second time bypass right from the opening of the sternum (bone which protects the heart from injuries) to opening the heart from chest tissues."

Dr Rath said since the surgery was a redo one it carried higher risk besides beating heart surgery was also a challenge. Redo are done when the grafts placed in the previous bypass surgery get obstructed and fresh grafts are placed to smoothen the blood flow.

"We had to maintain the blood sugar level by administering the insulin. Besides we have to ensure that heart does not get injured during the opening up of chest and then the grafting," he told PTI while explaining the precautions taken by surgeons during the operation of the prime minister, who is also a diabetic.

During the operation, surgeons ensured that there was no bleeding which always remains a risk during a repeat bypass surgery. They had planned four grafts initially but found that one more blood vessel needed a graft, so finally five grafts were placed on Dr Singh.

Rath, who passed out of Beherampur Medical College, has been with  Dr Ramakant Panda, head of surgery team, for the last 14 years and specialises in beating heart coronary artery bypass surgery. So far, he has performed more than 1,000 bypass surgeries.

The surgery on a serving prime minister came as a recognition of his talent, he said. "I felt very honoured when I was informed about the surgery," he said.

Asked if there was any pressure on the doctors, Rath said "...there was certain amount of pressure definitely but you know if you have to be on top, you have to perform well under pressure like Sachin and Yuvraj."

"It's like playing a Test match in a different atmosphere. Some tension is always there but all patients are different. If one comes under pressure one cannot perform well...you have to treat him as any other patient and do the thing," he said.

Singh was brought to AIIMS after the complaints of chest pain. The angiography performed last Wednesday revealed multiple blockages and collapse of stents which were placed in 2004 to dilate the vessels and ensure smooth blood supply to heart muscles.