View source for Answer - Rhythm Puzzle may 2005

{{NHJ|
|mainauthor= '''T.A. Simmers, A.A.M. Wilde'''
|edition= 2005:5,195
}}
[[Image:Puzzle_2005_5_195_fig1.jpg|Figure 1|thumb]]

An otherwise healthy 66-year-old male was referred
with complaints of central chest pain. He was not
on any medication, and there were no risk factors for
coronary artery disease. Pain invariably occurred at rest
and subsided spontaneously within approximately 15
minutes. Physical examination, laboratory testing,
resting ECG and stress test were all within normal limits;
myocardial perfusion scintigraphy revealed no ischaemia.
During hospitalisation the patient experienced a
recurrence, at which time an ECG (figure 1) was taken.
En route to emergency coronary angiography the ECG
normalised and the symptoms resolved. Angiography
showed no significant coronary stenosis. 

* '''What is the most likely diagnosis?'''
* '''What diagnostic and/or therapeutic measures should be taken?'''