A 68-year-old male complains to his family physician that when he tests his blood pressure using a ...

A 68-year-old male complains to his family physician that when he tests his blood pressure using a machine at his pharmacy, his heart rate is nearly always very low.
 
  At other times, he feels that his heart is racing, and it also seems to pause at times. The man has also had occasionally light-headedness and a recent syncopal episode. What is this client's most likely diagnosis and the phenomenon underlying it?
  A)
  Sick sinus syndrome as a result of a disease of his sinus node and atrial or junctional arrhythmias
  B)
  Ventricular arrhythmia as a result of alternating vagal and sympathetic stimulation
  C)
  Torsade de pointes as a result of disease of the bundle of His
  D)
  Premature atrial contractions that vacillate between tachycardic and bradycardic episodes as a consequence of an infectious process