Digital filter not removing noise at specific frequency Matlab
As mentioned in my comment, the filter returned by iirnotch is useless. From your filter coefficients you can see that the filter is only marginally stable due to two poles on the unit circle at DC and at Nyquist. Furthermore, even though the filter has a notch, it also attenuates all other frequencies quite strongly (apart from DC and Nyquist). The reason for that behavior is the extremely large bandwidth in your specification.

The figure below shows the magnitude responses of the filter you designed (top) and of a notch filter with a bandwidth BW = w0/35 (bottom) (note that the extremely large values very close to DC and Nyquist due to the poles are not shown in the top figure):



In any case, the bottom figure is what a notch filter should look like. If you tried that filter and it didn't do what you expected it to do, then the reason might be that your estimation of the noise frequency is wrong. Could it be that you got it wrong by a factor of $2$ (i.e., it would be a 60Hz hum)? [Also, doesn't the file name ecg58... suggest a disturbance at $2\cdot 29=58$Hz?]

So there might be several problems in your approach, but one is definitely the design of the notch filter, and if I may guess I would say that the other is the estimation of the noise frequency.