Hypoxemic respiratory failure is a common reason for admission to the intensive care unit. The etiology has an extensive differential diagnosis.
18-year old female smoker with history of asthma presented to the emergency department with progressive dyspnea and chest pain for one week. Past medical history included polycythemia treated with serial phlebotomies. Also, episodic cyanosis often accompanied previous asthma exacerbations and physical exertion. Initial improvement of dyspnea and cyanosis were noted with an albuterol inhaler. Systems review included progressive wheezing, productive cough and three syncopal episodes in the past year. Neither edema, calf pain, nor hemoptysis were noted. Admission vital signs were: blood pressure,122/80 mmHg, heart rate,120 beats per minute, respiratory rate, 24 respirations per minute, temperature, 38.0C. Oxygen saturation of 74% on room air. The patient was placed on a non-rebreather mask with FIO2=1.0, which improved oxygenation to 92%. Physical exam revealed a petite female in minimal distress. Jugular venous pressure was 12cm H20. Cardiac exam disclosed an increased pulmonic component of the second heart sound, but no murmur. Bilateral expiratory wheezes were noted over the lungs, and digital clubbing was present. Desaturation to as low as 60% with minimal exertion occurred. Arterial blood gases showed a pH of 7.42, pCO2, 31 mmHg, PO2, 65 mmHg, with sPO2 of 90% on FIO2 of 1.0. Enlarged pulmonary arteries with no infiltrates were noted on chest radiography and electrocardiographic right ventricular strain was evident. Transthoracic echocardiogram (TTE) study indicated an estimated right ventricular systolic pressure=120 mmHg with no evidence of an intracardiac shunt. Computed tomography of the chest and extremeties to evaluate for pulmonary thromboembolism excluded vascular occlusion, but deep vein thrombosis was diagnosed. Upon further review, a patent ductus arteriosus (PDA) was found (image 1). On sagittal cuts, contrast was noted flowing from the pulmonary artery directly into the aorta with retrograde flow into the ascending aorta (image 2). The patient’s condition deteriorated rapidly despite aggressive treatment with bronchodilators, antibiotics, glucocorticoids and anticoagulation. A cardiac arrest occurred following intubation from which the patient could not be resuscitated.
The patient had severe pulmonary hypertension with Eisenmenger syndrome secondary to a large PDA. Increased pulmonary arterial pressure from progressive increases in pulmonary vascular resistance due to hypoxia most likely led to further reversal of blood flow across the PDA. PDA comprises 10% of congenital heart disease cases. Individuals with a small PDA may be asymptomatic; exercise intolerance may develop in older children. Notably, subjects with large undiagnoses PDAs such as in our patient seldom reach adulthood because of supervening endarteritis and sudden death from cardiac failure. Considering that a cardiac murmur may not be audible with a PDA once pulmonary vascular resistance is abnormally elevated, echocardiography plays a key diagnostic role in establishing the diagnosis. Transesophageal echocardiography has a higher sensitivity and a greater negative predictive value than TTE. Poor functional class, syncope, pulmonary hypertension, and lack of pulmonary vasodilatory response during right heart catheterization are associated with a poor outcomes.
Clinically occult congenital heart disease with Eisenmenger syndrome is an infrequent cause of hypoxemic respiratory failure. Of particular concern is when the cause is a large, previously undiagnosed PDA without an accompanying cardiac murmur. Our case demonstrates the need to consider this possibility, and confirms the high mortality observed when pulmonary hypertension supervenes in this condition.
Michael Plisco, None.