The given ellipse equation:
\[
4x^2 + 9y^2 - 16x + 54y + 61 = 0
\]
Rewriting in standard form:
\[
\frac{(x-2)^2}{4} + \frac{(y+3)^2}{9} = 1
\]
If tangents from a point \( P(h, k) \) to an ellipse are perpendicular, the locus satisfies:
\[
h^2 + k^2 - 6h + 4k = 0
\]
Thus, the correct answer is:
\[
x^2+y^2-6x+4y=0
\]