Low Mortality In Sickle Cell Patient Cohort with Elevated Tricuspid Regurgitant Jet Flow Velocity

Abstract 1641

Elevated tricuspid regurgitant jet flow velocity (TRV) occurs in approximately 30% of adults with sickle cell disease (SCD) and is reported to be an independent risk factor for early death with a mortality rate as high as 40% after 4 years. We previously presented the results on a cohort of 85 consecutive ambulatory sickle cell patients that were prospectively screened for elevated TRV (2.5 m/sec) using trans-thoracic echocardiography. We aimed to determine the mortality rate in relation to TRV and associated factors in a well characterized cohort of sickle cell disease patients in the Netherlands.

Follow up consisted of regular outpatient visits including laboratory testing and repeated echocardiography every 2 years. Baseline hemoglobin (Hb), lactate dehydrogenase (LDH), brain natriuretic peptide (BNP), N-terminal pro brain natriuretic peptide (NT-proBNP), asymmetric dimethylarginine (ADMA) and arginine plasma levels were related to outcome, as were baseline pulmonary function tests and coagulation studies.

The prevalence of elevated TRV in the cohort at baseline was 30% (41% in HbSS/HbS⁰-thalassemia patients and 13% in HbSC/HbS⁺-thalassemia patients). Median (IQR) follow-up for the whole group was 53 months (50-57). No patients were lost to follow-up. Four patients (3 HbSS and 1 HbSβ⁰-thalassemia) died during follow-up. Two of these patients had an elevated TRV at baseline while the other two initially had immeasurable TRV, resulting in a death rate for patients with an elevated TRV of 8% and a ratio for early death in of 2.3 (95 percent confidence interval, 0.3 to 16.6; p=0.40) However, the two patients with immeasurable TRV at baseline had an elevated TRV (2.55 m/sec and 2.92 m/sec) on repeated echocardiography two years later. Median age of the patients who died was 48 (34-58) years compared to 29 (21-44) years of those who survived (p=0.18). Baseline plasma levels (medians (IQR)) of Hb and LDH in the deceased were 4.7 (4.3-5.0) mmol/L and 676 (575-801) U/L compared to 5.4 (4.8-6.0) and 410 (341-629) in the survivors (p=0.075 and p=0.049) respectively. Baseline median NT-proBNP plasma levels in the deceased were 278 (131-686) pg/mL and 520 (154-3957) pg/mL compared to 45 (26-94) and 91 (52-150) in the survivors (p=0.007 and p=0.03) respectively. Pulmonary function testing, coagulation studies and plasma levels of ADMA and arginine were not associated with mortality in this cohort.

Conceding the relative young age of our cohort, we conclude that the mortality in sickle cell patients with elevated TRV values was far lower as compared to the published literature. Although an elevated TRV could still be an important risk factor for early death, mortality may in fact be much lower than previously reported which is in line with more recent observations by other groups. With respect to biomarkers, we confirmed that NT-pro BNP and BNP levels were significantly higher in patients who died, with a trend toward a higher rate of hemolysis as well.