TOPIC: Pulmonary Vascular Disease
      TYPE: Medical Student/Resident Case Reports
      INTRODUCTION: Patent foramen ovale (PFO) is a cardiac defect with a prevalence of 25-30%, which notably decreases with age. A study done in 2018 showed an increased incidence of PFO in patients with pulmonary hypertension (pHTN). It is suggested that the presence of PFO in these individuals is a reflection of dilated and dysfunctional right atrium and ventricles, leading to an increased right to left gradient, stretching open a communication between the two atria.
      CASE PRESENTATION: We present a 96 year old female with heart failure with preserved ejection fraction, chronic respiratory failure secondary to moderate persistent asthma, on 4L of O2 at baseline, recurrent venous thromboembolic disease on apixaban, severe untreated OSA, initially admitted for septic shock due to acute cholecystitis requiring percutaneous cholecystostomy and broad spectrum antibiotics. On admission she also had significant hypoxia with cyanosis requiring intubation. The level of hypoxia was discordant with the clinical picture, with chest x-ray only showing atelectasis. She was extubated to high flow nasal cannula five days later, however we faced challenges in weaning her oxygen requirements. She received systemic steroids, anticoagulation and diuresis without improvement. Subsequently, the patient underwent an echocardiogram that showed a pulmonary artery systolic pressure (PASP) of 79mmHg (previously 47 mmHg in a study done 8 months ago). Given the degree of hypoxia and associated increase in PASP, intracardiac shunting was suspected. A repeat TTE with bubble study confirmed the presence of a small PFO. We discussed surgical closure, however invasive measures were deferred given her advanced age. Instead, the patient was treated with short acting diltiazem every 6 hours and furosemide daily with the goal of reducing pulmonary pressures and R to L shunting of deoxygenated blood. Although diltiazem is associated with negative outcomes in patients with heart failure, there was no evidence of pulmonary vascular congestion, and the immediate benefit outweighed the risk. Many days after initiating our plan, her oxygen requirements suddenly dropped from 60L/min to 4L/min and we were able to discharge her successfully.
      DISCUSSION: It is postulated that sepsis can lead to pHTN from elevated pulmonary vascular resistance through various mechanisms. Opening of PFO in severe pHTN is a common occurrence - resulting in resistive hypoxemia. Although we lack definitive evidence without right heart catheterization, we were able to exclude other etiologies of hypoxia through trial and error, strengthening our theory that PFO was the main driver of the clinical presentation.
      CONCLUSIONS: To summarize, hypoxia due to intracardiac shunting is an important cause of hypoxia, not to be missed on our list of differential diagnoses, with timely identification and appropriate therapy being the key to positive outcomes.
      REFERENCE #1: Sharan L, Stackhouse K, Awerbach JD, Bashore TM, Krasuski RA. Effect of Patent Foramen Ovale in Patients With Pulmonary Hypertension. Am J Cardiol. 2018 Aug 1;122(3):505-510. doi: 10.1016/j.amjcard.2018.04.014. Epub 2018 May 1. PMID: 30201113.
      REFERENCE #2: William J. Sibbald, NigelA.M. Paterson, Ronald L. Holliday, Richard A. Anderson, Trevor R. Lobb, John H. Duff, Pulmonary Hypertension in Sepsis: Measurement by the Pulmonary Arterial Diastolic-Pulmonary Wedge Pressure Gradient and the Influence of Passive and Active Factors, Chest, Volume 73, Issue 5, 1978, Pages 583-591, ISSN 0012-3692,
      REFERENCE #3: Islam S, Masiakos P, Schnitzer JJ, Doody DP, Ryan DP. Diltiazem reduces pulmonary arterial pressures in recurrent pulmonary hypertension associated with pulmonary hypoplasia. J Pediatr Surg. 1999 May;34(5):712-4. doi: 10.1016/s0022-3468(99)90361-5. PMID: 10359169.
      DISCLOSURES: No relevant relationships by Maryam Ahmed, source=Web Response
      No relevant relationships by Robert McDonald, source=Web Response