Excitation waves in two-dimensional media form various travelling wave patterns such as spiral and target waves. These waves can interact with heterogeneities in the tissue. Spiral waves can attach and form stable pinned waves in heterogeneous excitable media. These spirals can be unpinned by delivering a carefully timed electric stimulus, delivered very close to the core. We study the spiral wave unpinning when a wave is attached to two obstacles at the same time. We show that the unpinning window decreases as the distance between theobstacles increases, and beyond a critical distance, this window completely vanishes. Our study implies that the distribution of heterogeneities can play a critical role in developing the low-energy defibrillation methods.