What do you mean by Holter monitor has only one lead but the ECG have 12 leads. How does one lead pick up ischemic changes of the heart rythm. (F/up) previous question?

Lead, in EKG terms, refers to electrical viewpoint, not the physical number of electrical connections. E.g. the typical single lead Holter connects to two electrodes on the skin plus a third used as an electronic ground to improve signal to noise ratio given the tiny voltages being recorded. Holters are not designed to detect ischemia, only heart rhythm. 12 EKGs can detect signs of ischemia but miss most disease.
Holter. A holter monitor is primarily used to look for abnormal heart rhythyms, not so much to look for ischemia. Each ECG lead looks from a different angle a the heart while the Holter from only one angle.

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My heart structurally fine on echo, MRA, ECG, MRI, holter monitors. Is it unlikely my frequent PVCs will turn into Ventricular tachycardia/death?

Unlikely. With a normal heart based on all the studies you have had, PVCs are usually benign and not like to precipitate ventricular tachycardia. The caveat is that you are on diltiazem as well as amitriptyline both of which can affect the heart rhythm. Thus you should continue to have your EKG monitor. All the best to you! Read more...