Two Toronto law firms have launched a Canada-wide class-action lawsuit against the manufacturers of implantable defibrillators that can fail with little or no warning because of potentially defective batteries. About 8,000 Canadians were implanted with the cardiac defibrillators with the brand names Fortify, Fortify Assura, Fortify Assura MP, Unify, Unify Assura, or Unify Quadra, …