In a 28-year old womanstarting at the second pregnancy for a period of 7 years progressive dyspnoea on exertion andcyanosiswasrecorded.Theauthors diagnosed severe fixed pulmonary hypertension originally diagnosed as primary. On perfusion scintigraphy with 99mTc-MAA diffuse non-hemogeneous perfusion at a subsegmental level was proved as well as a haemodynamically significant right-to-left shunt. The scintigraphic sign of a right-to-left shunt is evidence of 99mTc-MAA accumulation in the brain, adrenal cortex, myocardium, thyroid gland. The magnitude of the right-to-left shunt on orientational quantification based on the distribution of the radiopharmaceutical substance between brain and lungs accounted for more than 50% of the cardiac minute volume. According to the postmortemfinding thromboembolic disease was involved with secondary pulmonary hypertension and foramen ovale pervium. The right-to-left shunt was the possible cause why the patient with severe pulmonary hypertension did not develop dextrolateral failure.

        Key words: pulmonary perfusion scintigraphy with 99mTc-MAA – right-to-left shunt – pulmonary hypertension