View source for Where do the extras come from

{{NHJ|
|mainauthor= '''A.A.M. Wilde, R.B.A. van den Brink'''
|edition= 2005:2,67
}}
[[Image:Puzzle_2005_2_67_fig1.jpg|Figure 1|thumb]]
A 64-year-old man had an inferior myocardial infarction ten years ago. Lately he has been having palpitations with occasional dizziness. He sought the attention of his cardiologist. Physical examination revealed no particular abnormalities with the exception 
of a laterally displaced ictus cordis. His 12-lead ECG, shown in figure 1, was in sinus rhythm with some extrasystoles. The electrical axis is vertical and the Q waves and abnormal ST-T segments in the inferior leads are compatible with an old inferior myocardial infarction. An echocardiogram revealed reduced left ventricular function with extended inferior wall
akinesia. The left ventricular ejection fraction was estimated to be 30%. 

The questions to address are: '''what is the meaning of the extrasystoles, where do they come from and should further investigations be performed?'''

[[Puzzle 2005_2_67 - Answer|Answer]]