Non sustained vt<30sec more concern in patients with left ventricular impaired function compared to normal lv function normal heart ejection fraction?

Yes, but concern: NS Ventricular tachycardia has a higher degree of concern in patients with impaired ejection fraction. However, the larger concern is that having runs of nonsustained VT are not particularly common in the normal population, so even in patients with normal EF, would still be concerned about ischemic heart disease in patients who are having runs of NS VT.