The study, “Atypical Hemolytic Uremic Syndrome following Acute Type A Aortic Dissection,” was published in the journal Case Reports in Hematology.
Atypical hemolytic-uremic syndrome (aHUS), a type of thrombotic microangiopathy, is a disease that mainly affects the kidneys. This condition, which can occur at any age, causes abnormal blood clots to form in the small blood vessels of the kidneys, progressively damaging and impairing their function.
Aortic dissection occurs when there is an injury to the innermost layer of the aorta, the largest artery that supplies oxygenated blood to the rest of the body. The injury allows blood to flow between the layers of tissue forming its wall, gradually forcing them apart. There are two types of aortic dissection, type A and B, depending on which region of the aorta is damaged.
Acute type A aortic dissection (ATAAD) is the most common and dangerous subtype of aortic dissection in which the tear is located in the upper portion of the aorta where it leaves the heart. ATAAD is life-threatening and requires emergency surgical repair. Despite emergency surgery, statistics indicate that the early mortality rate is approximately 20%.
As both ATAAD and surgical treatment are highly invasive, bleeding can provoke anemia and thrombocytopenia (low platelet levels), while malperfusion (abnormal blood flow) or surgical stress can lead to acute kidney disease, which is associated with aHUS.
In the study, a group of physicians in Japan reported, for the first time, the case of a 61-year-old woman with ATAAD who developed aHUS.
The woman, who had a history of untreated hypertension (high blood pressure), was seen by a local physician for her sudden back pain.
She was diagnosed with ATAAD after undergoing an enhanced computed tomography scan. Echocardiography, another imaging technique that allows physicians to visualize the heart, revealed she had moderate aortic valve regurgitation, a condition in which the heart’s aortic valve doesn’t close tightly.
She was transferred to the hospital, where she underwent surgery to repair the aortic valve regurgitation.
On postoperative day one, the patient’s platelet count decreased from 116×103/µl to 28×103/µl, causing physicians to transfuse 20 units of platelet concentrate.
Her platelet count still had not risen the following day, and dropped even further to 8×103/µl three days after the surgery. Her renal (kidney) function also worsened. Researchers confirmed the presence of schistocytes (red blood cell fragments that can take on different shapes) in her blood smear.
“Immediate consultations with the hematology team yielded a diagnosis of thrombotic microangiopathy (TMA), and we initiated plasma exchange and hemodialysis,” the scientists wrote.
Despite the fact that the treatment increased her platelet counts, the woman’s renal function failed to improve, and schistocyte levels continued to rise.
Next, the researchers investigated the type of TMA the patient had, as treatments can vary. She was eventually diagnosed with aHUS on postoperative day 14 and immediately started on Soliris (eculizumab).
After treatment, her anemia and thrombocytopenia improved without the need for further Soliris or transfusion support. However, her renal function did not recover. Subsequently, the patient was transferred to another hospital for rehabilitation.
One year after surgery, she died of multi-organ failure. For this patient, multiple factors, including the disease itself and surgical stress, could have triggered the development of aHUS, the authors noted.
While some cases of aHUS have been reported following transplantation surgery, including heart transplantation, only two cases of aHUS to date have been reported after non-transplant cardiac surgery.
“It is important to consider aHUS when a patient clinically develops [signs that are indicative of TMA] following cardiovascular surgery,” the researchers said.
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