"A GATED HEART POOL SCAN (GHPS) is a test used to determine how well the heart is pumping."
https://www.swslhd.health.nsw.gov.au/Liverpool/PET\content/p...


Gated Heart Pool Scan (GHPS) is actually the more common expression:
2.000 Google hits
https://www.google.com/search?rlz=1C1CHBF_deDE846DE846&biw=1...


Gated Heart Pool Study (GHPS)
87 Google hits
https://www.google.com/search?rlz=1C1CHBF_deDE846DE846&biw=1...


Gated Heart Pool Study (a.k.a. MUGA or GHPS)
(5th element in the list on the website)
https://www.exactradiology.com.au/services/nuclear-medicine/


"[First line, top of website:] The MUGA measures how well your heart is functioning as a pump. [... one of the last lines, bottom of website:] In Australia, this test may be called a GHPS, or Gated Heart Pool Scan."
http://www.chfpatients.com/tests/muga.htm


"[The] MUGA scan ('multiple-gated acquisition' = gated blood pool study) [enables to] watch [...] the beating of the heart. This allows us to assess how well the heart is working as a pump."
http://www.dgft.nhs.uk/wp-content/uploads/2015/04/MUGA-scan-...


"Le test MUGA, aussi appelé Ventriculographie isotopique, est un examen d’imagerie cardiaque qui fournit des données détaillées sur le débit sanguin cardiaque et la fonction de pompage du cœur."
https://www.ottawaheart.ca/fr/examen-intervention/test-muga


VENTRICULOGRAPHIE ISOTOPIQUE (une mesure de la capacité de pompage du cœur). Il s’agit d’un examen effectué pour évaluer la contraction du muscle cardiaque et mesurer sa capacité à pomper le sang."
http://icardio.ca/fr/articles/examens/ventriculographie-isot...

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Note added at 2 hrs (2019-05-18 09:30:00 GMT)
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So, the two mentioned tests in brackets, in your quoted sentence, "(..., multigated acquisition scan (MUGA), or gated heart pool study (GHPS))", are actually one and the same test. It really means "MUGA or GHPS", or "MUGA/GHPS". It doesn't mean "two different tests: MUGA and GHPS". A patient can only undergo one heart-pumping test: the MUGA/GHPS.