<prompt> Which of the following is untrue regarding sick sinus syndrome:Occurs most commonly in elderlyCoronary disease is a common causeECG manifestations are often intermittentMost symptomatic patients will require permanent pacing.  <response>: Coronary disease is a common cause Sick sinus syndrome is usually caused by idiopathic fibrosis of the sinus node. - Coronary disease is an uncommon cause. - Pharmacologic therapy for sick sinus syndrome has been difficult but recent studies have indicated that oral theophylline may be effective especially when sinus bradycardia is the major manifestation. 