Was the 6 minute episode of atrial tachycardia (at) significant enough to cause a blood clot? (note: i have a history of vte due to antiphospolipid syndrome). is at dangerous for pregnancy? what is the best treatment option for at for pregnant women?

There is no risk of blood clot in atrial tachycardia even you have history of VTE and APL syndrome. Focal atrial tachycardia is generally well tolerated by the mother and the fetus. With incessant atrial tachycardia, radiofrequency catheter ablation may need to be considered. To terminate a symptomatic episode, adenosine IV should be used. This arrhythmia will terminate shortly after delivery.

With history of VTE and antiphospholipid syndrome you should already be on anticoagulants (warfarin) which would also protect against atrial clots.