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RE: [RC] Question for RC. - heidi

"Thumps" is the common term for a condition more specifically known as Synchronous Diaphragmatic Flutter, or SDF. 
 
Anatomically, the phrenic nerve (which serves the diaphragm) runs right across the heart.  Nerves are normally "insulated" by a myelin sheath--a sheath of living cells that contain an insulating substance called myelin.  Every time the heart beats, there is an electrical discharge as electrolytes travel in and out of the heart muscle cells triggering the cells to contract.  Normally, because of the myelin sheath, this has no effect whatsoever on the phrenic nerve.
 
However, when certain e-lytes are way out of whack (usually calcium and/or magnesium), the cells containing the myelin become unable to fend off the electrical impulse that triggers the heart to beat, as e-lytes begin to leak through the sheath.  When that happens, each heartbeat triggers an electrical impulse on the phrenic nerve as well, causing the diaphragm to contract. 
 
This can range in severity from a very mild tic with each heartbeat to a great huge contraction.  It is seen in the flank--the flank looks like it is "pulsing" and if you put a stethoscope on the horse and listen to the heart, you will find that the "pulsing" of the flank is in rythm with the heartbeat.  More severe cases are what inspired the name of "thumping"--because that is exactly what it looks like when you stand back and watch the flank "thump."
 
Heidi



Good Morning Ride Camp!!!!
It's time to teach an old dog a new trick........What are "thumps"?  How do you treat them and what causes them?  I've never heard of them before until I read about them here?  Thanking one and all for your education on this subject.
Patty Israelson
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