How can I apply DWT, Threshold method, then iDWT for ECG signal?

Hi Everyone, I have ECG signal and I want to apply: 1- dwt 2- threshold method 3- idwt for ECG signal de-nosing. But I faced some problem with second and third stage (threshold and idwt) my question is how can I solve that. My code is

S=load('data.mat');   % ECG Signal 
y1=S.sig209;
nsig = awgn(y1,15);   % Generate White Gaussian Noise with SNR=15
sig1=y1+nsig;         % add noise to orignal Signal
OPsig=wden(sig1,'rigrsure','s','sln',6,'sym7');  %1-D de-noising
[AA,DD] = dwt(OPsig,'sym7');  % Applay DWT 
%%%Apply Threshold method
Sigma = median(abs(nsig))/0.6745;   % Equation Donoho and Johnstone (1994)
thresh = Sigma*sqrt(2*log(length(OPsig)));
Csig = idwt(AA,DD,'sym7');
subplot(3,1,1),plot(y1,'k'), axis([1 2000 -1  1]), grid on 
title('Orignal Signal') 
ylabel('Amplitude')
xlabel('Signal duration')
subplot(3,1,2),plot(sig1,'r'), axis([1 2000 -2 2]) , grid on 
title('Orignal Signal with white Gaussian noise')
ylabel('Amplitude')
xlabel('Signal duration')
OSNR=snr(y1,Csig-y1);
subplot(3,1,3),plot(Csig), axis([1 2000 -1 1]),title(['Optimal De-noising Signal','  ; OUTPUT SNR= ',num2str(OSNR)]) , grid on 
ylabel('Amplitude')
xlabel('Signal duration')