Unless an ecg signal is different than any other signal for some reason, the help on imdilate should have explained it. But anyway, try this:
% Make some random data.
ecg = rand(100,1);
% Dilate it.
filtered_ecg = imdilate(ecg, ones(3,1), 'same');
% Plot the signals.
subplot(2,1,1);
plot(ecg, 'b-', 'LineWidth', 2);
grid on;
title('Original ecg signal', 'FontSize', 30);
subplot(2,1,2);
plot(filtered_ecg, 'b-', 'LineWidth', 2);
grid on;
title('Dilated ecg signal', 'FontSize', 30);
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]); % Maximize figure.
set(gcf,'name','Demo by ImageAnalyst','numbertitle','off')
Nothing tricky or unusual at all. Since this is just the standard call to imdilate like you'd do for any signal (and probably just what you tried already), you'll have to explain why it's not appropriate for ecg signal. Or maybe dilation is just not really what you want to do???
