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Platypnoea-orthodeoxia syndrome, an underdiagnosed cause of hypoxaemia: four cases and the possible underlying mechanisms.

Nassif M, Lu H, Konings TC, Bouma BJ, Vonk Noordegraaf A, Straver B, Blom NA, Clur SA, Backx AP, Groenink M, Boekholdt SM, Koolbergen DR, Hazekamp MG, Mulder BJ, de Winter RJ - Neth Heart J (2015)

Bottom Line: Cardiac platypnoea-orthodeoxia syndrome (POS) is a position-dependent condition of dyspnoea and hypoxaemia due to right-to-left shunting.It often remains unrecognised in clinical practice, possibly because of its complex underlying pathophysiology.We present four consecutive patients with POS and patent foramen ovale (PFO) who underwent a successful percutaneous PFO closure, describe the mechanism of their POS and provide a review of the literature.

View Article: PubMed Central - PubMed

Affiliation: Department of Cardiology, Cardiac Catheterization Laboratory, Academic Medical Center-University of Amsterdam, PO Box 22660, 1100 DD, Amsterdam, The Netherlands. r.j.dewinter@amc.uva.nl.

ABSTRACT
Cardiac platypnoea-orthodeoxia syndrome (POS) is a position-dependent condition of dyspnoea and hypoxaemia due to right-to-left shunting. It often remains unrecognised in clinical practice, possibly because of its complex underlying pathophysiology. We present four consecutive patients with POS and patent foramen ovale (PFO) who underwent a successful percutaneous PFO closure, describe the mechanism of their POS and provide a review of the literature.

No MeSH data available.


Related in: MedlinePlus

A physiological model of the pulmonary vasculature in the upright position in a normal lung (a) versus a lung post-pneumonectomy (b). Due to gravitation, in the upright position blood flow in the apex of the lung is physiologically prevented since alveolar pressure exceeds the pulmonary arteriolar pressure (pulmonary zone I phenomenon). A high pulmonary vascular resistance in the post-pneumonectomy situation causes an increase in right ventricular afterload. When right ventricular output reduces in the upright position, this afterload cannot be compensated. Consequently, pulmonary arteriolar pressure drops even more, causing a larger pulmonary zone I. I pulmonary zone I with restricted blood flow, II zone II with normal blood flow, III zone III with maximum blood flow; Palv alveolar pressure, Part arteriolar pressure, Pven venous pressure
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Fig2: A physiological model of the pulmonary vasculature in the upright position in a normal lung (a) versus a lung post-pneumonectomy (b). Due to gravitation, in the upright position blood flow in the apex of the lung is physiologically prevented since alveolar pressure exceeds the pulmonary arteriolar pressure (pulmonary zone I phenomenon). A high pulmonary vascular resistance in the post-pneumonectomy situation causes an increase in right ventricular afterload. When right ventricular output reduces in the upright position, this afterload cannot be compensated. Consequently, pulmonary arteriolar pressure drops even more, causing a larger pulmonary zone I. I pulmonary zone I with restricted blood flow, II zone II with normal blood flow, III zone III with maximum blood flow; Palv alveolar pressure, Part arteriolar pressure, Pven venous pressure

Mentions: Case 1, 2 and 4 had undergone pulmonary resection, in one patient this was left-sided and in two patients right-sided, after which they started developing dyspnoea. According to the first explanation, after pneumonectomy the right ventricular afterload increases and compliance decreases due to the reduced pulmonary vascular bed (Fig. 1a1, b1, d1) and the subsequent increase in pulmonary vascular resistance. Right ventricular afterload is also increased by post-pneumonectomy fluid overload in the operated hemithorax [7, 8]. These haemodynamic changes cause a right-to-left shunt due to a transient pressure gradient since right atrial pressure increases. An upright position reduces right ventricular preload and cardiac output. Orthodeoxia might consequently develop due to an increase in the alveolar dead space known as ‘pulmonary zone I’ (Fig. 2), in which the pressure in alveoli exceeds the orthostatic decrease in pulmonary arteriolar pressures, causing an additional ventilation-perfusion mismatch [8]. Though not reported in our cases, a different cause of dyspnoea after lung surgery can be phrenic nerve injury, particularly after right-sided pneumonectomy [9, 10]. The elevated right hemidiaphragm causes right ventricular compression and subsequent outflow impairment, which in turn causes a transient pressure gradient resulting in the right-to-left shunt. In these particular cases, plication of the diaphragm is preferred over PFO closure to remove the underlying cause [9]. Figure 3 summarises the haemodynamic explanation in a schematic view.Fig. 2


Platypnoea-orthodeoxia syndrome, an underdiagnosed cause of hypoxaemia: four cases and the possible underlying mechanisms.

Nassif M, Lu H, Konings TC, Bouma BJ, Vonk Noordegraaf A, Straver B, Blom NA, Clur SA, Backx AP, Groenink M, Boekholdt SM, Koolbergen DR, Hazekamp MG, Mulder BJ, de Winter RJ - Neth Heart J (2015)

A physiological model of the pulmonary vasculature in the upright position in a normal lung (a) versus a lung post-pneumonectomy (b). Due to gravitation, in the upright position blood flow in the apex of the lung is physiologically prevented since alveolar pressure exceeds the pulmonary arteriolar pressure (pulmonary zone I phenomenon). A high pulmonary vascular resistance in the post-pneumonectomy situation causes an increase in right ventricular afterload. When right ventricular output reduces in the upright position, this afterload cannot be compensated. Consequently, pulmonary arteriolar pressure drops even more, causing a larger pulmonary zone I. I pulmonary zone I with restricted blood flow, II zone II with normal blood flow, III zone III with maximum blood flow; Palv alveolar pressure, Part arteriolar pressure, Pven venous pressure
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4608923&req=5

Fig2: A physiological model of the pulmonary vasculature in the upright position in a normal lung (a) versus a lung post-pneumonectomy (b). Due to gravitation, in the upright position blood flow in the apex of the lung is physiologically prevented since alveolar pressure exceeds the pulmonary arteriolar pressure (pulmonary zone I phenomenon). A high pulmonary vascular resistance in the post-pneumonectomy situation causes an increase in right ventricular afterload. When right ventricular output reduces in the upright position, this afterload cannot be compensated. Consequently, pulmonary arteriolar pressure drops even more, causing a larger pulmonary zone I. I pulmonary zone I with restricted blood flow, II zone II with normal blood flow, III zone III with maximum blood flow; Palv alveolar pressure, Part arteriolar pressure, Pven venous pressure
Mentions: Case 1, 2 and 4 had undergone pulmonary resection, in one patient this was left-sided and in two patients right-sided, after which they started developing dyspnoea. According to the first explanation, after pneumonectomy the right ventricular afterload increases and compliance decreases due to the reduced pulmonary vascular bed (Fig. 1a1, b1, d1) and the subsequent increase in pulmonary vascular resistance. Right ventricular afterload is also increased by post-pneumonectomy fluid overload in the operated hemithorax [7, 8]. These haemodynamic changes cause a right-to-left shunt due to a transient pressure gradient since right atrial pressure increases. An upright position reduces right ventricular preload and cardiac output. Orthodeoxia might consequently develop due to an increase in the alveolar dead space known as ‘pulmonary zone I’ (Fig. 2), in which the pressure in alveoli exceeds the orthostatic decrease in pulmonary arteriolar pressures, causing an additional ventilation-perfusion mismatch [8]. Though not reported in our cases, a different cause of dyspnoea after lung surgery can be phrenic nerve injury, particularly after right-sided pneumonectomy [9, 10]. The elevated right hemidiaphragm causes right ventricular compression and subsequent outflow impairment, which in turn causes a transient pressure gradient resulting in the right-to-left shunt. In these particular cases, plication of the diaphragm is preferred over PFO closure to remove the underlying cause [9]. Figure 3 summarises the haemodynamic explanation in a schematic view.Fig. 2

Bottom Line: Cardiac platypnoea-orthodeoxia syndrome (POS) is a position-dependent condition of dyspnoea and hypoxaemia due to right-to-left shunting.It often remains unrecognised in clinical practice, possibly because of its complex underlying pathophysiology.We present four consecutive patients with POS and patent foramen ovale (PFO) who underwent a successful percutaneous PFO closure, describe the mechanism of their POS and provide a review of the literature.

View Article: PubMed Central - PubMed

Affiliation: Department of Cardiology, Cardiac Catheterization Laboratory, Academic Medical Center-University of Amsterdam, PO Box 22660, 1100 DD, Amsterdam, The Netherlands. r.j.dewinter@amc.uva.nl.

ABSTRACT
Cardiac platypnoea-orthodeoxia syndrome (POS) is a position-dependent condition of dyspnoea and hypoxaemia due to right-to-left shunting. It often remains unrecognised in clinical practice, possibly because of its complex underlying pathophysiology. We present four consecutive patients with POS and patent foramen ovale (PFO) who underwent a successful percutaneous PFO closure, describe the mechanism of their POS and provide a review of the literature.

No MeSH data available.


Related in: MedlinePlus