An elevated tricuspid regurgitant jet velocity (TRV) has been associated with hemolysis and increased mortality in sickle cell disease (SCD). An elevated TRV is also associated with decreased exercise capacity as measured with the six minute walk distance (6MWD). Vascular complications including pulmonary arterial hypertension (PAH) and thrombosis have been reported to occur at an increased rate following splenectomy in various disorders, including chronic hemolytic anemias or those associated with ineffective erythropoiesis, such as thalassemia. The risk of elevated TRV, already high in patients with thalassemia (33%), is significantly increased with splenectomy (unadjusted O.R 5.3, 95% CI 2.1-13.5). We wanted to evaluate the independent association of splenectomy with TRV in a cohort of patients with homozygous SS disease (HbSS).
We performed a retrospective cross sectional analysis of the association between splenectomy and an elevated TRV. 41 splenectomized HbSS patients were identified within the 482 HbSS patients ≥12 years of age from the multi-centered Walk-PHASTT study of pulmonary hypertension; this study incorporated a cardiovascular phenotype, including echocardiogram and 6-minute walk distance (6MWD) as part of the observational phase of the study. This sample size achieved > 99% power to detect a 15% difference in TRV in the 2 groups at a significance level of 0.05 using a 2 sided two sample t-test. Other parameters compared between groups included 6MWD, age, blood pressure, body surface area, urine albumin, blood urea nitrogen, ferritin, creatinine, white blood cell count, platelet count, hematocrit, hemoglobin, bilirubin, lactate dehydrogenase, aspartate aminotransferase, absolute reticulocyte count (ARC), absolute neutrophil count and hydroxyurea use. Continuous variables were analyzed with linear regression and 2-sided t-tests and categorical variables were analyzed with Chi-square test. Multivariable linear regression models were constructed using variables significantly associated with TRV in bivariate analyses.
There were no significant differences in mean± SD TRV (2.62± 0.42 vs 2.62± 0.43, p=0.99) or 6MWD (446± 84 vs 440± 97, p=0.74) between the 2 groups. A history of splenectomy was associated with significantly higher ARC, hemoglobin and hematocrit. When adjusted for hemoglobin and ARC an association of TRV with splenectomy was still not observed (p=0.82).
Surgical asplenia is not associated with higher TRV compared with presumed auto-infarction of the spleen in a large cohort of adult patients with HbSS. Platelet and WBC counts were also not higher in the splenectomized patients, making it less likely that the thrombotic risk is greater in splenectomized patients compared to the high baseline risk in HbSS patients. The overall greater risk of elevated TRV with asplenia in HbSS cannot be addressed here, because most patients are functionally asplenic even absent surgical resection. However, these results suggest that, distinct from thalassemia, surgical asplenia does seem to not confer additional risk for elevated TRV in HbSS, an important consideration when weighing the risks and benefits of splenectomy.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.