The granddaughter of late evangelist Billy Graham is in hospital after suffering two back-to-back heart attacks over the weekend.

Rachel-Ruth Lotz was hospitalized on Saturday night after suffering the first heart attack. She then suffered a second heart attack on Sunday afternoon. 

Her mother, Anne Graham Lotz, daughter of Billy Graham, is asking for prayers. 

"Multiple times I have prayed Psalm 73:26 for people who were struggling with heart issues: My flesh and my heart may fail, but God is the strength of my heart and my portion forever," Lotz said on Facebook.

"I am now driving the stake of my faith down deep into this promise for my daughter, Rachel-Ruth." 

Lotz said she had been told by a doctor that Rachel-Ruth suffers from a rare condition called 'broken heart syndrome', which the Mayo Clinic describes as "a temporary heart condition that's often brought on by stressful situations and extreme emotions". According to Mayo, the causes of broken heart syndrome are "unclear". 

"I am urgently asking you to join my family in praying for Rachel-Ruth," Lotz said.

"Please pray for her heart to stabilize; for accurate diagnosis and treatment; for the doctor's supernatural wisdom; for peace and comfort for all of us."

She concluded by quoting Scripture. 

"The lead verse in today's Daily Light from Psalm 103 was very encouraging ... Bless the Lord, O my soul ... Who redeems your life from destruction, who crowns you with loving kindness and tender mercies." 

Rachel-Ruth is married with three children and serves on the board of directors for her mother's outreach AnGeL Ministries where she also chairs a weekly prayer team.

Lotz's brother, Franklin Graham, has asked his social media followers to pray for his niece. 

"Please join me in praying for my sister Anne Graham Lotz's daughter, Rachel-Ruth," he wrote.