First of all, please peruse the drawing linked below. It's not good but it gives you the idea.

This is an ECG with two traces on the oscilloscope. The upper trace is an ordinary-looking ECG. The lower trace is a heart shape traced as in the image. The different parts of the ECG are scaled up and down as appropriate and an average of one cycle is shown on the high-persistence phosphor CRT at a time (probably out of date but there you go). I've considered Lissajous figures but want to keep it simple. On the other hand, if there's a way of producing a cardioid using ECG readings and an oscilloscope, that would be very interesting indeed, if also a complete mindfsck.

OK, one caveat: I'm a herbalist, not a cardiologist and i seldom get to read ECGs, though it occasionally comes up. When it does, i look things up in my nice shiny wipe-clean hospital cardiology book.

Therefore, any mistakes i make in the following are unlikely to result in me killing anyone by mistake.

A healthy heart produces a trace which looks like a heart: symmetrical, good aspect ratio, two upper semicircular humps separated by a curved valley along with a V- shaped lower half. There will be some variations between adults, children, resting, exercise and so on, physiologically.

Tachycardia produces a narrower heart-shape.

Bradycardia produces a wider heart-shape.

In atrial fibrillation, the start of the left heart hump, which happens to be an atrium, disappears, the heart-shape looks lopsided in the middle and it constantly shifts around. This can be seen easily because of the persistence of the phosphor.

Nodal rhythm: Starts in the middle of the left hump. Leftmost side completely absent.

First degree block: Heart stretched out to the left.

Second degree block: Middle of heart can vanish.

Wenkebach phenomenon: Heart stretches and shrinks in the middle.

Wolff-Parkinson-White &c: Left and part of right side narrow.

Conduction defects: Wide in the middle.

Flat-topped, no valley: Ventricular hypertrophy.

Sharp right-hand edge: hypokalaemia.

Right hump higher than left: hyperkalaemia.

Wide middle: hypercalcaemia.

Narrow middle: hypocalcaemia.

As i say, the normal-looking trace is still there at the bottom, allowing someone who is used to looking at them to diagnose as normal, but also, the heart-shaped trace makes differences easier to spot with less experience, and in at least one case actually gives a direct visual hint of what's going on.
-- nineteenthly, Nov 02 2011

Diagram http://imageshack.u...ges/24/heartax.png/
What i mean: waves labelled with letters as usual. [nineteenthly, Nov 02 2011]

Sort of like this? http://physics.tech...J_Card_84_2_161.pdf
Scroll down to figure 1. [mouseposture, Nov 02 2011]

Polarcardiography http://www.scienced...ii/0010480980900166
"Polar coordinates, rather than rectangular coordinates, are more appropriate to the study of the heart vector" [lurch, Nov 03 2011]

BMI is relatively easy to follow, though probably simplistic. I think what i suggest would be good, but if there's a way of sticking the whole lot together into a closed curve of some kind deviating from a cardioid, that would be better.
-- nineteenthly, Nov 02 2011


Although I doubt it has diagnostic merit, many simple waveforms will produce cardioid plots in polar coordinates. An old radar display with a heart on it would be a nifty, if useless, gadget. The rotation would have to match the heartbeat exactly, too, so it may end up simpler just to have two lightbulbs; 'alive' and 'dead'.
-- mitxela, Nov 02 2011


Simplest way might be:
1. let X be raw EKG
2. let Y be dX/dt. (easy circuit: two resistors, one capacitor, and an op-amp)
3. Plot Y vs. X. Either
a. A/D converter, computer, and some software
b. (recommended) get yourself an old storage oscilloscope -- the kind that'll take an external timebase signal.

Probably *would* be diagnostically useful, except that everybody's already invested so much time in learning to read conventional EKGs.

Edit: see <link>
-- mouseposture, Nov 02 2011


That's some fine work, [rolfingrodent]. Those (linked) phase planes actually closely resemble hearts (real hearts, not valentine hearts).
-- spidermother, Nov 03 2011


I thought [mitxela]'s comment on polar coordinates was interesting, so I googled it. I found it fascinating that there were so many mathematical descriptions of observed heart electrical activity which are actually done in polar coordinates - yet all of the graphics are put back into line traces, as [mouseposture] comments about investment.

I think that is the definition of "hidebound".
-- lurch, Nov 03 2011


This is QWERTY all over again. However, i can't see a reason why they shouldn't coexist.
-- nineteenthly, Nov 03 2011


It's disgusting that an organization is trying to sell a paper from the 80s for 27 dollars.
-- Voice, Nov 05 2011



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