1. Right Heart obstruction
Obstructions can occur at various levels in the right side of the heart or in the pulmonary outflow path. Pure obstructions do not result in a mixing of the blood but cause a massive additional strain on the ventricles because they have to pump against increased resistance.
2. Left Heart obstruction
(From: http://www.embryology.ch/anglais/pcardio/patholcardio01.html#rechtsherzobstruktion, http://www.embryology.ch/anglais/pcardio/patholcardio02.html#Linksherzobstuktion)