Real time acquisition using drawnow

I tried to read data from AD8232 ECG Module using HC-05 and plot the signal in real time. But when I try drawnow it give a sample rate of 40-60 Hz and with drawnow limitrate it gives some random data and the final results its nothing like the ecg from arduino ide even if i have 500 Hz sample rate. I then tried to pause for 0.001 s and the sample rate is good 160 Hz, the signal is ok, but its with 1 minute delay and its not stopping even when i press ctr+c.

The code implemented is below:

b = instrfind('Type', 'bluetooth', 'Name', 'Bluetooth-HC-05:1', 'Tag', '');
if isempty(b)
    b = Bluetooth('HC-05', 1);
else
    fclose(b);
    b = b(1);
end
fopen(b);
figure
h = animatedline;
ax = gca;
ax.YGrid = 'on';
i=1;
x = zeros();
stop = false;
startTime = datetime('now');
while ~stop
    x(1,i) = str2double(fscanf(b));
    t =  time2num((datetime('now') - startTime),'seconds');
    if isnan(x(1,i))
        x(1,i) = 0;
    end
    addpoints(h,t,x(1,i))
    ax.XLim = [t-3 t];
    i = i+1;
    drawnow limitrate
    pause(0.001)
end

Please is there a function beside pause to slow down the drawnow limitrate without delaying the acquisition?

Below is the acquisition with pause and without it.