Evaluation of left ventricular systolic function in pediatric sickle cell anemia patients using the end-systolic wall stress-velocity of circumferential fiber shortening relationship

OBJECTIVES The aim of this work was to evaluate myocardial contractility using the end-systolic wall stress (ESSm)-velocity of circumferential fiber shortening (VCFc) relationship in sickle cell anemia (SCA) patients compared with a similar age group of African-American (AA) control patients. BACKGROUND Abnormalities of myocardial function have been documented in SCA patients using load-dependent echocardiographic indexes. Whether the systolic dysfunction results from impaired myocardial contractility or altered loading conditions is unknown because controlled studies using a load-independent measure of contractility have not been performed. METHODS Fifty healthy AA patients and 57 SCA patients age 3 months to 18 years were studied. Simultaneous indirect arterial pulse tracing, phonocardiogram, electrocardiogram, and M-mode tracing of the left ventricular (LV) short-axis were recorded. The LV dimensions, corrected ejection time (ETc), percent fractional shortening (%FS), VCFc, and ESSm were determined. The ESSm-VCFc relationship was calculated and compared between groups. Duration and severity of anemia and effects of exchange transfusion on the ESSm-VCFc relationship were determined. RESULTS The SCA patients had increased LV dimensions in systole and diastole, and increased indexed LV mass. Load-dependent measurements of LV function (ETc, %FS, and VCFc) were lower in SCA patients, and afterload, as measured by ESSm, was increased. The ESSm-VCFc relationship demonstrated reduced contractility in SCA patients compared with control subjects. Degree and duration of anemia along with exchange transfusions did not impact contractility. CONCLUSIONS Sickle cell anemia patients have significant LV dilatation and increased LV mass due to abnormal loading conditions. Contractility, measured by the ESSm-VCFc index, is lower in SCA patients and was not negatively impacted by severity or duration of anemia, or exchange transfusions. The underlying mechanism explaining these findings requires further investigation.