A 71-year-old woman with a history of hypertension and induced deep vein thrombosis presented with sudden diaphoresis and dizziness that began while sitting.
She had also had intense, aching pain in the middle of her left arm with transient cyanosis of her left fingers and associated numbness, but no chest pain, palpitations or shortness of breath.
The entire episode had lasted 20 minutes and her symptoms had subsided by the time the EMS arrived. His vital signs on arrival were stable with a heart rate of 80 bpm, respiratory rate of 20 bpm, blood pressure of 120/89 mm Hg, oxygen saturation of 99% on room air, and temperature of 36.5°C. His examination was notable only for a non-palpable left radial pulse seen on Doppler. Her fingers were pink and well imbued with untouched sensation.
The electrocardiogram and chest radiograph were unremarkable. Her initial lab results showed an elevated troponin of 0.23 ng/mL; his B-type natriuretic peptide was normal at 12 pg/mL. A bedside echocardiogram showed a dilated right ventricle with hypokinesia consistent with McConnell’s sign.
What additional imaging would you order and what diagnosis could explain these results?
Find a case discussion on the next page.
Diagnosis: Thromboembolism secondary to PFO
A patent foramen ovale (PFO) is an atrial septal defect that persists for more than a year with a potential complication of a right-to-left shunt resulting in a paradoxical embolism. PFOs occur in 15% to 35% of adults based on cadaver studies (Mayo ClinProc. 1984;59:17), although the risk of paradoxical arterial embolism is less than 2%. (Process [Bayl Univ Med Cent]. 2019;32:256; https://bit.ly/3Pg6pVc.) Cerebrovascular events account for most paradoxical emboli, but acute limb ischemia is much less common. (J Am Coll Cardiol. 2014;64:403; https://bit.ly/3PmryNv.)
The presence of concomitant venous thrombosis, systemic embolism, and intracardiac communication with a right-to-left shunt mechanism, as in pulmonary embolism, strongly suggests paradoxical embolisms. (J Vasc Bras. 2021;20:e20210074; https://bit.ly/3PmOqwv.) A review of the recent literature revealed that acute limb ischemia due to paradoxical emboli occurs mainly on the left side (82%) and often affects the lower limbs (72%). Several limbs were affected in 27.5% of the analyzed cases. A DVT was noted in 71% of cases and a concomitant pulmonary embolism in 82% of cases. (Anne Vasc Surg. 2020;66:668.e5.)
Careful clinical examination remains the primary means of diagnosing this rare condition. A pulseless limb or asymmetrical pulses in a limb, especially when accompanied by pain, poikilothermia, or paresthesia, should prompt consideration of acute limb ischemia. First-line imaging in acute limb ischemia is often duplex ultrasound based on cost-effectiveness, lack of radiation exposure, and turnaround time when accessible, although the digital angiography by subtraction remains the reference.
Approximately 61% of cases of acute upper limb ischemia can be attributed to embolic phenomena, 60% of which are associated with atrial fibrillation, so an echocardiogram should be pursued to determine the etiology of thromboembolism. (J Thromb Haemost. 2013;11:836; https://bit.ly/3zjxj8Y.) The recommended initial test is transthoracic echocardiography, which may reveal a PFO with a right-to-left shunt augmented by the Valsalva maneuver. (Biomed Res Int. 2020;2020:1513409; https://bit.ly/3ziv0mM.)
Venous thromboembolism should be ruled out once a PFO is identified in acute limb ischemia. Computed tomography pulmonary angiography remains the standard of care when evaluating a pulmonary embolism. (Cardiovascular diagnosis. 2018;8:225; https://bit.ly/3cfFc6o.) Compression ultrasound has become the preliminary imaging modality of choice. (Eur J Radiol. 1990;11:131.)
No standard treatment exists given the paucity of data on PFO-mediated acute limb ischemia. Anticoagulation was immediately initiated in 61% of cases, while 88% received embolectomy, fibrinolysis, or both in a review of the literature on acute limb ischemia triggered by paradoxical embolisms. PFO closure was also achieved in 49% of these cases. (J Vasc Bras. 2021;20:e20210074; https://bit.ly/3PmOqwv.) PFO repair is best studied in patients with cryptogenic stroke, but the factors involved in determining whether to intervene are similar and include comorbidities, bleeding risk, and anatomy. (Interval Cardiol. 2020;15:e15; https://bit.ly/3OjmiJh.)
McConnell’s sign appeared on our patient’s bedside echocardiogram, so she underwent CT pulmonary angiography which revealed a large saddle embolism concurrent with left axillary artery occlusion and right heart strain. She was admitted to intensive care and received catheter-directed lysis of her pulmonary embolism. A subsequent bubble echocardiogram confirmed a previously unknown PFO. She underwent a vascular duplex of her upper and lower extremities which showed no flow into the left axillary, brachial or radial arteries, with minimal flow into the left ulnar artery via the collaterals.
The patient had normal flow in her right upper extremity arteries. Her right femoral vein harbored a non-occlusive, chronic-appearing, wall-adherent DVT with acute, totally occlusive DVT of the popliteal, peroneal, and posterior tibial veins. She was switched from systemic heparin to apixaban prior to discharge. Discussions between vascular medicine and interventional cardiology determined that she was at too high risk for PFO closure, and indefinite anticoagulation was recommended.
Aortic dissection was a significant possibility on the differential. However, we were able to identify secondary signs of right heart strain using early bedside ultrasound, which greatly helped guide our subsequent decision-making and imaging modality.
Clockwise from top left:Dr Foois a critical care fellow at Brigham and Women’s Hospital in Boston and completed her residency in emergency medicine at the University of Virginia School of Medicine, whereDr MutterandDr Sandeare associate professors of emergency medicine.