Systems and methods for performing electrophysiology (EP) signal processing

1. A computer implemented method for filtering noise of an input signal, comprising:

accessing, by at least one processor, the input signal having a first harmonic frequency and having the noise;

calculating, by the at least one processor, a slope of the input signal;

determining, by the at least one processor, a presence of a quiet period based on the slope of the input signal being below a threshold value;

during the quiet period, storing, by the at least one processor, samples of the noise of the input signal in a buffer;

subtracting, by the at least one processor, the samples from a single cycle of the noise in the buffer from the input signal to create a filtered signal, wherein the subtracting removes the first harmonic frequency and a second harmonic frequency from the input signal and avoids introducing transient responses in the filtered signal; and

repeating, by the at least one processor, the calculating, determining, storing, and subtracting to refine the filtered signal.

2. The computer implemented method of claim 1 , wherein the storing further comprises:

averaging, by the at least one processor, a sample of the input signal with a corresponding sample of the noise of the input signal in the buffer to create an average sample; and

replacing, by the at least one processor, the corresponding sample of the noise of the input signal in the buffer with the average sample.

3. The computer implemented method of claim 2 , further comprising:

repeating, by the at least one processor, the calculating, determining, storing, and subtracting until the average sample peaks at a line frequency.

4. The computer implemented method of claim 1 , wherein the first harmonic frequency is 60 hertz and the second harmonic frequency is 120 hertz or 180 hertz.

5. The computer implemented method of claim 1 , wherein a frequency of the noise of the input signal is substantially constant.

6. The computer implemented method of claim 5 , wherein a size of the buffer is based on the frequency of the noise of the input signal.

7. A non-transitory computer-readable medium having instructions stored thereon that, when executed by at least one computing device, cause the at least one computing device to perform operations comprising:

accessing an input signal having a first harmonic frequency and having noise;

calculating a slope of the input signal;

determining a presence of a quiet period based on the slope of the input signal being below a threshold value;

during the quiet period, storing samples of the noise of the input signal in a buffer;

subtracting the samples from a single cycle of the noise in the buffer from the input signal to create a filtered signal, wherein the subtracting removes the first harmonic frequency and a second harmonic frequency from the input signal and avoids introducing transient responses in the filtered signal; and

repeating the calculating, determining, storing, and subtracting to refine the filtered signal.

8. The non-transitory computer-readable medium of claim 7 , wherein the storing further comprises:

averaging a sample of the input signal with a corresponding sample of the noise of the input signal in the buffer to create an average sample; and

replacing the corresponding sample of the noise of the input signal in the buffer with the average sample.

9. The non-transitory computer-readable medium of claim 8 , wherein the operations further comprise:

repeating the calculating, determining, storing, and subtracting until the average sample peaks at a line frequency.

10. The non-transitory computer-readable medium of claim 7 , wherein the first harmonic frequency is 60 hertz and the second harmonic frequency is 120 hertz or 180 hertz.

11. The non-transitory computer-readable medium of claim 7 , wherein a frequency of the noise of the input signal is substantially constant.

12. The non-transitory computer-readable medium of claim 11 , wherein a size of the buffer is based on the frequency of the noise of the input signal.

13. A system, comprising:

a memory comprising a buffer; and

at least one processor coupled to the memory and configured to:

access an input signal having a first harmonic frequency and having noise;

calculate a slope of the input signal;

determine a presence of a quiet period based on the slope of the input signal being below a threshold value;

during the quiet period, store samples of the noise of the input signal in the buffer;

subtract the samples from a single cycle of the noise in the memory from the input signal to create a filtered signal, wherein the subtracting removes the first harmonic frequency and a second harmonic frequency from the input signal and avoids introducing transient responses in the filtered signal; and

repeat the calculating, determining, storing, and subtracting to refine the filtered signal.

14. The system of claim 13 , wherein to store, the at least one processor is further configured to:

average a sample of the input signal with a corresponding sample of the noise of the input signal in the buffer to create an average sample; and

replace the corresponding sample of the noise of the input signal in the buffer with the average sample.

15. The system of claim 14 , wherein the at least one processor is further configured to:

repeat the calculating, determining, storing, and subtracting until the average sample peaks at a line frequency.

16. The system of claim 13 , wherein the first harmonic frequency is 60 hertz and the second harmonic frequency is 120 hertz or 180 hertz.

17. The system of claim 13 , wherein a frequency of the noise of the input signal is substantially constant.

18. The system of claim 17 , wherein a size of the buffer is based on the frequency of the noise of the input signal.

19. The system of claim 13 , wherein the at least one processor is a digital signal processor (DSP).

20. The system of claim 13 , wherein the input signal is a cardiac signal.