Platypnea-orthodeoxia syndrome in the right lateral decubitus position: a case report

Abstract Background Platypnea-orthodeoxia syndrome is a rare syndrome characterized by dyspnea and hypoxia when the patient is sitting or standing. Here we report a case of platypnea-orthodeoxia syndrome caused by a right hemidiaphragmatic elevation with giant liver cyst that triggered a right-to-left shunt through the patent foramen ovale. This case report is the first presentation of a case secondary to hemidiaphragmatic elevation with giant liver cyst. In addition to this, a malposition of the pacemaker lead could be associated with platypnea-orthodeoxia syndrome in this case. Case presentation A 91-year-old Japanese woman presented to our hospital with hypoxia of unknown origin. Severe hypoxia and cyanosis were observed only in the right lateral decubitus position. A chest X-ray and computed tomography scan revealed right hemidiaphragmatic elevation, which was probably compressing the right atrium. A transesophageal echocardiogram showed a compressed right atrium and shunt blood flow in both directions: from the left to the right atrium and vice versa. The shunt flow was exacerbated by postural changes from the left to the right lateral decubitus. A transesophageal echocardiogram also confirmed compression of the right atrium due to giant liver cyst and a malposition of the pacemaker lead abnormally placed in the left atrium through patent foramen ovale. We concluded that the cause of hypoxia was platypnea-orthodeoxia syndrome with right-to-left interatrial shunt through patent foramen ovale. Surgical closure of patent foramen ovale was not performed due to the age of our patient, surgical difficulties, and failure to obtain informed consent. For these reasons she was discharged after receiving medical advice about her posture. Conclusions Platypnea-orthodeoxia syndrome is rare and difficult to diagnose. The present case suggests that hypoxia due to postural changes should be considered a differential diagnosis of platypnea-orthodeoxia syndrome

Monosynaptic excitatory connection from the rostral ventrolateral medulla to sympathetic preganglionic neurons revealed by simultaneous recordings

To directly investigate whether a monosynaptic connection exists between neurons in the rostral ventrolateral medulla (RVLM) and sympathetic preganglionic neurons (SPNs), we used simultaneous extracellular recordings of RVLM neurons and whole-cell patch-clamp recordings of SPNs at the Th2 level and analyzed them by spike-triggered averaging. We averaged 200 sweeps of membrane potentials in SPN triggered by the spikes in the RVLM neuron. No clear postsynaptic potentials were detected in the averaged wave of SPNs before angiotensin II (Ang II) superfusion, whereas during superfusion with Ang II (6 micromol/L) on the medulla oblongata side alone excitatory postsynaptic potentials (EPSPs) were clearly found in the SPN of 3 out of 10 pairs at 40 +/- 1 ms after the averaged triggering spike in the RVLM neuron. We consider them to be monosynaptic EPSPs, because 1) the averaged EPSPs exhibited a sharp rise time, 2) the onset latency of the averaged EPSPs in the SPNs after the trigger spike in the RVLM was the same as the latency of the antidromic action potentials in the RVLM neurons in response to electrical stimulation of the SPNs, and 3) the amplitude of the averaged EPSPs was over 2 mV. In summary, combining simultaneous recording and spike-triggered averaging allowed us to demonstrate a monosynaptic excitatory connection between a single RVLM neuron and a single SPN in the thoracic spinal cord. Such connections provide the basis for the maintenance of sympathetic tone and the integrative reflex that relays through the RVLM. The results explain the mechanism by which Ang II in the RVLM area increases peripheral sympathetic activity and blood pressure.10 page(s