Case 31: Diagnosis & Conclusions

Case Published: April 2019

Case 31 Index

Diagnosis: Bilateral & Saddle Pulmonary Embolism due to HeRO graft and Intra-Atrial Thrombus Formation

Case Summary: Well done! In summary, this is an ESKD patient with multiple failed upper extremity vascular accesses in the past, who presents with hyperventilation and ultimately acute hypoxic respiratory failure and hypotension without clear evidence of volume overload or acute infection. Her blood gas is consistent with a pure respiratory alkalosis (for a refresher on solving acid-base problems, visit pLACO). This presentation should raise high suspicion for primary pulmonary process such as pulmonary embolism, but this can also occur in cases of early sepsis, panic attacks, head trauma and early salicylate poisoning (though we don’t have an anion gap metabolic acidosis here).

Based on history and physical, a panic attack or anxiety seems less likely. She has no fever or leukocytosis, making infection and sepsis less likely las well. She has not had any head trauma prior to presentation. The patient’s drug screen was negative. Together, these data bring pulmonary embolism to the top of our differential.

Notice that the point-of-care ultrasound (POCUS) image of the inferior vena cava (IVC)  shows a dilated vessel with less than 50% change on respiration. However lung ultrasound, which is highly sensitive for pulmonary edema, is negative. If B-lines were present, we would think pulmonary edema. There is no evidence of pneumothorax. Small pleural effusions can occur as a result of pulmonary emboli, as seen on the chest x-ray. It is possible that IVC caliber and  the response to intra-thoracic pressure (respiratory variation) are being impacted by an acute thromboembolic event which can raise pulmonary arterial pressure. In addition, the patient had undergone dialysis the day prior to presentation with an unremarkable basic metabolic panel – making volume overload from lack of or inadequate dialysis less likely.

To confirm our diagnosis, the next step would be to proceed with computed tomography (CT) pulmonary angiogram and transthoracic echocardiogram.  These studies confirm bilateral and saddle pulmonary embolism (PE),  right ventricular (RV) strain and evidence of an acute thrombus at the tip of the HeRO graft.

As noted in the physical examination, the patient has had multiple failed AV accesses in both upper extremities. It appears that in the past, she had a HeRO graft placed on the right but this failed – most likely due to thrombosis. The graft was abandoned but left in place and she now has a catheter in the right femoral region.

Let’s review… 
What’s a HeRO graft? (click!)
HeRO (Hemodialysis Reliable Outflow) Graft is a fully subcutaneous device implanted by a surgeon that provides continuous blood flow directly from an artery into the central venous system. With improved survival of dialysis patients, physicians will encounter patients who have exhausted upper arm access options due to poor vasculature and central vein stenosis. Catheter dependence makes them prone to bacteremia, and increased mortality. The HeRO consists of two elements, a graft (like an AVG) which connects with the arterial inflow and a venous outflow component which terminates in the right atrium, bypassing central vein stenosis. The graft and venous outflow are connected by a titanium connector.  Image Reference

Unfortunately, HeRO grafts (the venous outflow component) are also prone to thrombosis and it appears this patient had to abandon her graft for the same reason. The PTFE component of the HeRO graft is incorporated into the tissue, similar to the standard AVG. The venous outflow component should be removed if the HeRO is abandoned, as this creates a source for thromboembolism. This pulmonary embolism should be treated like any other  – preferably with lytic therapy or interventions. Once the patient is stable, the venous outflow component should be removed.

Case 31 Index
Case 31 Introduction
Case 31 Physical Exam
Case 31 Diagnostic Testing