# Right-dominant arrhythmogenic cardiomyopathy complicated by platypnea-orthodeoxia syndrome: a novel mechanism of patent foramen Ovale-mediated hypoxaemia: a case report

## TL;DR

A patient with right-dominant arrhythmogenic cardiomyopathy developed platypnea-orthodeoxia syndrome due to a patent foramen ovale, which was successfully treated with PFO closure.

## Contribution

This is the first documented case linking right-dominant ACM with POS via PFO shunting.

## Key findings

- PFO closure resolved hypoxaemia in a patient with right-dominant ACM and POS.
- Right heart dysfunction in ACM may create pressure gradients favoring right-to-left shunting through PFO in upright positions.

## Abstract

Platypnea-orthodeoxia syndrome (POS) is a rare but treatable cause of positional hypoxaemia, typically associated with intracardiac shunting. We present the first documented case of POS secondary to patent foramen ovale (PFO) in a patient with right-dominant arrhythmogenic cardiomyopathy (ACM).

A 48-year-old male with right-dominant ACM developed progressive dyspnoea and upright hypoxaemia. Workup examinations revealed atrial flutter and PFO with right-to-left shunting. PFO occlusion resolved hypoxaemia, with sustained improvement at 3-year follow-up despite progressive RV dysfunction.

This case represents a rare form of POS attributable to the coexistence of PFO and right-dominant ACM. The pathophysiological mechanism underlying POS in this case might be parallel to that observed in right ventricular myocardial infarction or ischaemia in which elevated right-sided intracardiac pressures due to impaired RV output secondary to right heart dysfunction equals or surpasses left heart pressure which created a pressure gradient favourable for right-to-left shunting (RLS) through the PFO in upright position. Based on comprehensive clinical evaluation, PFO closure was ultimately performed.

This case highlights right-dominant ACM as a novel predisposing factor for POS via PFO shunting. The pathophysiological mechanism underlying POS in this case might be parallel to that observed in right ventricular myocardial infarction or ischaemia. PFO closure may be curative for right-dominant ACM-related hypoxaemia and POS.

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