2838When your past catches up with you: Stress cardiomyopathy triggered by acute upper airway obstruction in the setting of an atrial septal defect and coronary arterio-luminal shunts

Abstract

Introduction: Stress cardiomyopathy is characterised by acute, reversible left ventricular (LV) systolic dysfunction in the absence of obstructive coronary disease. Its pathophysiology is not well understood, but it is precipitated by acute adrenergic stimuli, including emotional distress and exogenous catecholamines, and is more common in women. We report a case of stress cardiomyopathy induced by acute prolonged upper airway obstruction triggered by coughing, with exacerbation of the resulting hypoxia by right to left shunting from a previously undiagnosed atrial septal defect. A coexisting congenital coronary artery to LV fistulous anomaly may have worsened the insult by coronary artery steal. Case report: A 75-year-old female developed acute severe stridor and chest pain after a coughing fit terminated by a blow to the back of her chest from her husband. Her history included hypertension, and dyslipidaemia but no known cardiovascular or respiratory comorbidities. Examination at presentation was unremarkable. The initial ECG showed broad T wave inversion. High sensitivity troponin T was elevated. Chest xray revealed clear lung fields. Coronary angiography demonstrated non-obstructive disease, however contrast was noted to fill the LV following injection of both coronary arteries, consistent with arterio-luminal fistulous connections to the LV. Transthoracic echocardiography (TTE) showed moderate LV systolic impairment with apical ballooning, consistent with stress cardiomyopathy. Colour flow Doppler imaging demonstrated transmural flow in the apical and distal anterolateral wall, corresponding to the fistulae seen on angiography. Additionally there was an atrial septal defect (ASD) with a left-to-right shunt at rest. The patient made an excellent recovery with supportive therapy and was discharged after 4 days. Repeat TTE at 6 weeks showed complete recovery of LV function. Questions and problems: We propose four intersecting factors had a collective effect on this patient's acute asphyxia: Repeated negative thoracic pressure changes, severe hypoxia, sympathetic nervous system activation and pre-existing intracardiac shunts at an atrial and ventricular level. What are the haemodynamic effects of acute upper airway obstruction on LV function? What is the significance of the small resting interatrial shunt when acute negative intrathoracic pressure occurs? What is the significance of the arterio-luminal channels seen on angiography? Which was the greater myocardial stress - hypoxia, adrenergic storm or a combination of the two? Did gender play a role? Discussion: In this case, we propose a complex interplay of several mechanisms contributed to the hypoxia and LV dysfunction. The choking episode initially acted as both an emotional and physical trigger of stress cardiomyopathy. Apnoea-induced hypoxia and additional adrenergic stimulation of carotid body chemoreceptors were additive factors. Coughing and airway obstruction caused increased right and decreased left atrial pressures, reversing flow through the pre-existing interatrial shunt. Hypoxia contributed to microvascular dysfunction. The haemodynamic effects of repeated respiratory efforts against an obstructed upper airway (Muller manoeuvre) imposed an acute afterload on the LV. Finally, arterio-luminal shunting of blood from the coronary arteries directly to the LV may have contributed to coronary steal in the apex, exacerbating myocardial stunning. This case demonstrates the importance of understanding cardiac physiology, and how seemingly benign anatomical variants can become pathogenic under certain conditions. (Figure Presented).