The Filipino legend dropped and stopped Matthysse in impressive fashion in Kuala Lumpur, Malaysia last month and is now an eleven-time world champion.
In the wake of the triumph, Pacquiao told media in his home country how he needed to checked out during a routine ECG.
“When we were ECG, it seemed like someone saw the ECG’s result in a problem, so the doctor just made sure that there was no problem, so I was undergoing an angiogram,” he explained.
“They looked, no problem. My teams did not know that I was undergoing surgery,” he added.
Conflicting reports have since led to confusion surrounding the 39 year-old’s condition, which Pacquiao has moved to clear up ahead of his next fight.
“Let me take this opportunity to clarify one thing; My heart is OK. My heart is healthy. I feel stronger and younger than ever,” Pacquiao told GMA News.
“My heart will continue to beat with love and compassion for our people. I will continue to honor God and our country with excellence and integrity – inside and outside the ring.”
Potential opponents for a first defense of his welterweight belt are emerging, whilst a move back down to super-lightweight has also been mentioned.
Facing old training partner Amir Khan or current lightweight king Vasyl Lomachenko at a catchweight seem to be the top choices for Pacquiao, who is firmly back in the mix at the top of the boxing tree.
Shooting back into the WBN P4P Top 10, Pacquiao still believes he has at least two more big fights in his locker, with Khan and Lomachenko both massive in their own right, whether in the US, Asia or the UK respectively.