Need help calculating BPM from ECG

NEED HELP IMMEDIATELY please. THANK YOU!!!

I performed the Valsalva maneuver and I have to show the changes it causes in heart rate.

I have filtered the raw ECG signal and found the R peaks but Im having trouble calculating Heart Rate BPM. I have put my code at the bottom. Please help me identify what I did wrong and what changes must be made.

%% Finding heart rate

clear;clc;

load('Mydata.mat');

rawdata = b1;%loading data from Labscribe File

ecgraw = rawdata(:,4);%extracting Filtered ECG Data

timeraw = rawdata(:,1);%extracting time points

figure(1)

plot(timeraw,ecgraw)

xlim([5 84])

%Implementing Filters

%low-pass filter

Wn = 0.5; %Wn=cuttoff frequency, high cutoff frequency of 5 Hz

n=300; %order of filter

lowpass = fir1(n,Wn,'low'); %implementing a 300th order FIR low pass filter

filterlowpass = filtfilt(lowpass,1,ecgraw);

%high-pass filter

Wn = 0.0067; %Wn=cuttoff frequency, low cutoff frequency of 0.67 Hz

n=300;

highpass = fir1(n,Wn,'high'); %implementing a 300th order FIR high pass filter

filterhighpass = filtfilt(highpass,1,filterlowpass);

figure(2) %plotting filtered ECG signal

plot(timeraw,filterhighpass);

xlim([5 84]);

xlabel('Time (secs)');ylabel('ECG (mV)');

title('Filtered ECG Signal');

figure(3) %plotting filtered ECG signal

plot(timeraw,filterhighpass);

xlim([5 84]);

xlabel('Time (secs)');ylabel('ECG (mV)');

title('Filtered ECG Signal');

hold on

[ecgpeaks,time] = findpeaks(filterhighpass,timeraw,'MinPeakProminence',0.14,'MinPeakDistance',0.3);

%identifying the R wave peaks of the QRS complex, MinPeakHeight and

%MinPeakDistance can be changed to identify clear peaks

%plot heart rate as a function of time

plot(time,ecgpeaks,'r*');

xlabel('Time (secs)');ylabel('ECG (mV)');

title('Peaks of Filtered ECG Signal');

xlim([5 84])

hold off

%% ( This is where the probelm starts )

%

totalnumberofpeaks = numel(ecgpeaks) %count the total number of peaks found within the signal

peaknumber = [1:1:totalnumberofpeaks]'; %create a column vector of the peak numbers going from 1 to the total number of peaks. Create row vector then transpose

timeinsecs = time; %convert time into seconds

HeartrateBPM = (peaknumber./timeinsecs).*60; %calculate heart rate in bpm, where heart rate = (number of peaks at a given time/given time)x60

figure(4) %plot heart rate as a function of time

plot(timeinsecs,HeartrateBPM);

xlabel('Time (secs)');ylabel('HR (bpm)');

title('Heart Rate');

[Scott MacKenzie]

It might help if you also post Mydata.mat.

[Usama Zia]

sure this the Mydata.mat

Answer 1

[Pavan Guntha]

Hi Usama,

I understand that the issue is related to the Heart rate computation in BPM. As per the code attached, the 'HeartrateBPM' computes the heart rate by considering all the R-peaks occured until current time. So, the instantaneous effect of R-peaks on the heart rate isn't captured. For calculating instantaneous heart rate you could have a look at the following code snippet:

totalnumberofpeaks = numel(ecgpeaks)    %count the total number of peaks found within the signal
peaknumber = [1:1:totalnumberofpeaks]'; %create a column vector of the peak numbers going from 1 to the total number of peaks. Create row vector then transpose
timeinsecs = [time(1); diff(time)];     %calculating time difference b/w consecutive peaks in seconds
HeartrateBPM = 60./time_new;            %calculating instantaneous heart rate (in BPM)

You could look at the documentation of diff function for more details.

Hope this helps!