The Spaniard was close to joining Serie A side Cagliari earlier this month as a free agent having played the past two years at Watford.
However, Cagliari abandoned the signing of the 37-year-old after medical examinations revealed a heart problem.
"I can confirm that Manuel Almunia failed a medical due to a heart condition," Cagliari spokesman Alessandro Steri told Press Association Sport.
"Further tests done have revealed he is suffering from an apical hypertrophic cardiomyopathy (HCM)."
HCM is a genetic heart disorder that can cause sudden death.
Almunia began his playing career at home club Osasuna in 1999
He joined Arsenal in 2004 from Celta Vigo, leaving in 2012
Source : PA