It could be a flow murmur, which could be innocent or a leaky valve murmur
. An ECHO will help detect leaky
valves. Flow murmurs can occur with conditions like anemia, which can also cause tachycardia. If it a leaky valve murmur, there could be different clinical outcomes. If this is mild, it may not need any therapy now. As you have been investigated, discuss all the possibilities with your doctor and clear your doubts.
Hope this helped and do keep us posted.