Data from Nancy Guthrie's pacemaker might mean she was involved in some kind of struggle with her potential captors just before she was kidnapped, a top cardiologist has theorized.

The 84-year-old, who is the mother of Today show host Savannah Guthrie, is believed to have been abducted late Saturday night from her home in Tucson, Arizona. 

She had one last recorded heart rate spike around 2am Sunday, which was picked from her implanted medical device to her Apple watch and iPhone, police previously revealed. 

But now, that recorded data could mean much more, according to Dr. Jonathan Reiner, a leading heart doctor, said. 

'If a person was in a physical struggle, that might have created a rapid heartbeat over a certain threshold, the pacemaker would have detected that and potentially reported it,' Reiner, who was former Vice President Dick Cheney's physician, told CNN on Thursday. 

Authorities have been treating Guthrie's home as an active crime scene, as blood was found leading from the front of the house to the driveway. 

Authorities confirmed at a press conference on Thursday that the blood was Nancy's. Police said they are no closer to finding a suspect - but also told the public that no one has been ruled out. 

A doorbell camera she owned was also removed from its spot by the time investigators arrived on Sunday. They also found the Apple devices in her home. 

At least three media organizations have reported receiving purported ransom notes that they handed over to investigators. The sheriff's department said it was taking the notes and other tips seriously but has declined to comment further.   

At least one ransom note was sent to TMZ demanding millions in Bitcoin for her release, but it is currently unclear if the note is genuine.

FBI has said that they have made one arrest for an imposter ransom demand. 

Nancy lives in a $1 million home in the affluent Catalina Foothills neighborhood.

Her daughter is estimated to make around $8 million a year as one of the nation's most well-known talk show hosts. 

On Wednesday evening, Savannah and her siblings, Annie and Camron, released an emotional video statement on Instagram, sending direct messages to their mom and her abductor. 

'Mommy, if you are hearing this, you are a strong woman. You are God's precious daughter,' the journalist said. 

'Our mom is a kind, faithful, loyal, fiercely loving woman of goodness and light. She's funny, spunky and clever. She has grandchildren that adore her and crowd around her and cover her with kisses,' Guthrie added. 

She then spoke directly to her elderly mother's potential kidnappers, telling them that 'we are ready to talk' but wanted proof that they weren't potentially using fraudulent images of her.  

'We live in a world where voices and images are easily manipulated. We need to know, without a doubt, that she is alive and that you have her. We want to hear from you and we are ready to listen. Please, reach out to us,' she said through the tears.

Guthrie then directly addressed her mother.

'Mommy, if you are hearing this, you are a strong woman. You are God's precious daughter, Nancy,' she said.

'We believe and know that even in this valley, he is with you. Everyone is looking for you, mommy, everywhere. We will not rest, your children will not rest until we are together again.'

'We speak to you every moment and we pray without ceasing and we rejoice in advance for the day that we hold you in our arms again. We love you, mom,' the NBC star added.

Annie and Camron Guthrie then echoed their sister's words, adding: 'We love you, mom. Stay strong.'

Now, five days into her mysterious disappearance, NBC fears that a recent Today Show feature might have inadvertently placed Nancy in danger, the Daily Mail has learned. 

Just about three months back, Savannah returned to her hometown of Tucson for a nostalgic tour visiting where she grew up. 

The special segment, which aired on NBC's Today show in November, framed Tucson as the city where her 'soul is home', with a focus on family and community. 

Her mother, Nancy, made a rare on-air appearance during that episode. 

The search for Nancy has entered its fifth day.