Cerebral venous thrombosis (CVT) due to vaccine-induced immune thrombotic thrombocytopenia (VITT) might have an in-hospital mortality rate of up to 50% but new thrombotic and bleeding events and deaths are rare after the acute phase, research shows.

International registry data on 60 patients who survived the acute phase of CVT after COVID-19 vaccination has shown only two patients (3%) died during follow-up – one due to a new intracerebral haemorrhage and one of unknown causes.

“No other relapses or bleeding events were reported. No new venous or arterial thrombotic events were reported in any patient,” the study said.

“Hospital readmission occurred in 9/54 (17%) cases, 4 of which were for a planned cranioplasty following decompressive hemicraniectomy.”

The study, published in Stroke [link here], said functional independence was achieved by 88% of patients at follow-up and 53% had returned to work or school.

And given the median follow-up was only five months, there was potential for even further recovery.

The study authors, including Clinical Associate Professor Tim Kleinig, Dr Alvin Chew, Dr Carlos Garcia-Esperon, Associate Professor Karl Ng, Dr Miriam Wronski, Dr Alvaro Cerera, Dr Jim Burrow and Dr Sophia Chatterton from Australia, said the high proportion of patients who were functionally independent at follow-up was comparable to that of patients after CVT not related to VITT.

“The low number of adverse outcomes in surviving CVT-VITT patients may be explained by the fact that anti-PF4 (platelet factor 4) antibodies, which cause VITT, are transient. With the disappearance of the anti-PF4 antibodies, the triggering factor for VITT may have resolved,” they said.

The study also found that where D-dimer levels were available in the registry data, they declined from >4 mg/L in the acute phase to ≤0.5 mg/L at follow-up in most (70%) patients.

Meanwhile, in a related article using data from the international CVT registry, mortality was lower in patients treated according to VITT recommendations compared to those not treated according to recommendations (32% v 52%; OR 0.43).

“Patients who were treated with immunomodulation had a lower risk of death than patients who were not treated with immunomodulation (19/65 [29%] vs 24/34 [70%], adjusted OR = 0.19, 95% CI = 0.06–0.58),” the study said.

“All patients who were not treated with any anticoagulation died (13/13, 100%).”

Patients who received platelet transfusion (regardless of whether they received surgery or not) did not have a higher risk of death (17/27 [63%] vs 26/72 [36%], adjusted OR = 2.19, 95% CI = 0.74–6.54).

“Astonishingly, platelet transfusion was not associated with higher mortality. On the one hand, patients who received platelet transfusion more often presented with coma and ICH and were treated with hemicraniectomy, reflecting more severe disease. On the other hand, platelet transfusion might have aggravated VITT reflected by an increased rate of worsening or new ICH and new VTE during admission.”

The study, published in Annals of Neurology [link here], said adherence to VITT recommendations fortunately improved over time.

“Within only approximately 1 month of the publication date of the recommendations, three quarters of patients with VITT-CVT received the adapted treatment. At the same time mortality started declining, which is in line with recently published findings.”

“Among patients who did not fulfill one recommendation criterium (24/55, 44%), this was due to administration of heparins or withholding anticoagulation (16/24, 67%), lack of immunomodulation (6/24, 25%), and platelet transfusion without surgery indication (2/24, 8%). In 25 of 55 (45%) cases, 2 criteria were not fulfilled, and in 6 of 55 (11%) cases all 3 criteria were not fulfilled,” it said.

The study reiterated that despite decreasing mortality rates with the implementation of VITT-CVT recommendations, the mortality remains much higher with VITT-CVT than in CVT unrelated to vaccination (29% v 3.9%).