I got a urine sample from Rusty at home once. I emptied the litter and put
on a fresh clean litter box liner. Rusty still used his box without the
litter. I emptied the urine into a vial and took it to the vet. They asked
me several times how I got the
sample before running tests on it.
Of course if Rusty pooped in the box, this won't work. You can try to
confine
Sammy to a room with her own litter box.

Winnie

Unfortunately, this is hard to explain without pictures.

**** basic but technical description of EKG follows; may be skipped ***

An EKG is an electrical record of successive heartbeats. In humans, it's
measured concurrently from 12 real and computed points, but since there
isn't room for all the electrodes on a cat, feline EKGs have fewer views.

OK. Start with the word "isoelectric".  That means straight horizontal
line with no electrical activity at the moment.  In an EKG, there are
three major peaks, one of which has several components. Much of the
analysis involves timing between the peaks, and then changes to the
normal shape.

When the heart's normal pacemaker fires, there's a brief bump in the
isoelectric line. This is called the P wave, and shows the electrical
impulse starting.  Heart rate, in a normal patient, is based on the time
between successive P waves. There are many abnormalities where the heart
can skip a beat, and if there is no P wave, that shows the problem is
likely to be in the main pacemaker part of the heart, the sinoatrial
(SA) node.  Hearts also have backup pacemakers.  I have a problem called
Sick Sinus Syndrome, where the P signal doesn't always happen,
especially when I'm asleep. For that reason, I have a surgically
implanted pacemaker. Without it, my heart has been known to stop for as
long as 10 seconds. It's electronic pacemaker time whenever the heart
stops for more than 3 seconds.

The big wave is called the QRS complex.  That's a little misleading, as
in a normal EKG, you go from P to R. Q is present only in certain
abnormalities.  The big peak is the R wave on the rising side and the S
wave on the falling side. This complex shows the large lower chambers of
the heart, the ventricles, contracting and releasing.

If there is no QRS complex following a P wave, this is one of the many
types of heart block, where the signal from the SA node is not being
conducted to where it's needed.

Normally, the S wave returns to isoelectric, and, a little later, you'd
see a T wave, which shows the recharging of the ventricles. If you draw
a line between S and T, you have the ST segment.  When the ST segment is
above or below the line, there is a problem of blood supply to the
ventricles: inadequate flow (angina or myocardial ischemia) or actual
dead tissue ("heart attack" or myocardial infarction).

In atrial disease, you may see a very short time between P waves,
sometimes even too fast for the ventricles to keep up. This will also
make the EKG much harder to read, as you may get random P waves
superimposed on QRS or T waves.

*** a little less technical

If the QRS signal has a high amplitude, it may indicate the heart has
enlarged, causing a larger signal.