The reason to not lift any heavy weights with BAV is because there usually is a spike in blood pressure. High blood pressure has to be under control because BAC is actually a vessel tissue disorder that is vulnerable to high blood pressure. It is OK to lift lighter weights with more reps.
The following information may give you some insight from a study. The objective of the study was to observe the influence of breathing technique on arterial blood pressure (BP) generated during heavy, dynamic weight lifting. BP was recorded in 10 male athletes by radial artery catheterization. Each subject then performed double-leg press sets at 85% and 100% of maximum. Each exercise was performed twice, once with closed glottis Valsalva, and then with slow exhalation during concentric contraction. The mean BP at 100% maximum with Valsalva was 311/284. The highest pressure recorded in an individual was 370/360. With slow exhalation, the mean BP was 198/175 when the same 100% maximum was lifted (p<.005). A reduced pressor response was also noted at 85% maximal lifting with slow exhalation. Arterial hypertension produced during heavy weight lifting with Valsalva is extreme and may be dramatically reduced when the exercise is performed with an open glottis (without Valsalva). It is concluded that heavy resistance exercise is safer when performed while the subject breathes with an open glottis