LEFT VENTRICULAR STUCTURE AND FUNCTION IN PATIENTS WITH SICKLE CELL ANAEMIA

Abstract

Background: Cardiovascular system abnormalities are prominent features of sickle cell anaemia. Previous studies have been inconclusive on the diastolic and systolic function in sickle cell anaemia patients. There is limited literature on their left ventricular geomertric patterns in SCA subjects.. Objectives: To assess the left ventricular structure and functions in patients with sickle cell anaemia seen at the University College Hospital, Ibadan and to compare with controls of comparable age and sex. Materials and methods: One hundred and sixty-one subjects were recruited into the study. There were 90 SCA subjects in steady state and 71 controls. The groups were of comparable age and sex. They all had clinical evaluation and Echocardiographic examination, including M-mode, Doppler echocardiograpy and tissue Doppler imaging. Results: The mean age of SCA subjects was 26.10 years while the mean age for the control group was 25.95 years. The sickle cell anaemia subjects had smaller baseline clinical characteristics and also lower systolic and diastolic blood pressures. Twenty eight patients (29.83% had dyspnoea, None of the controls had dyspnoea. The SCA subjects had larger cardiac dimensions. There was no difference in the LV systolic load dependent indices and load independent indices between the two groups. There was diastolic dysfunction among the SCA subjects with a prevalence of 16.6% using TDI and 10% using transmitral flow indices. The E/E i which is a measure of of left ventricular filling pressure and myocardial stiffness was higher among the SCA subjects. The predominant abnormal LV geometric pattern in SCA subjects was eccentric LV hypertrophy.

xv Conclusion: This study has shown that there is normal systolic function in sickle cell anaemia patients. There is evidence of diastolic dysfunction among SCA subjects and they may have increased myocardial stiffness. The predominant abnormal LV geometric pattern in SCA subjects is eccentric LV hypertrophy. There is need for long term prospective longitudinal studies in among SCA subjects in Nigeria to determine the prognostic implication of diastolic dysfunction and abnormal LV geometry.

xvi

CHAPTER ONE

Introduction Sickle cell disease is the most important haematological disease that affects people of black African descent.

Sickle cell disease is a clinical condition characterised by qualitative or quantitative disorder of haemoglobin due to inheritance of haemoglobin S in addition with any other abnormal haemoglobin such as S (sickle cell anaemia), C (haemoglobin SC disease), beta thalassaemia (Haemoglobin S beta thalassaemia). Other rarer haemoglobinopathies include SD Punjab, SO Arab, S Lepore and SE disease. The sickle cell gene is known to be widespread, reaching its highest incidence in equatorial Africa and endemic malarial areas. The distribution is determined by the occurrence of the sickle cell mutation and its selection by falciparum malaria

Page 1 of 2

. There is a protective effect and a selective advantage to the heterozygote carrier of sickle cell against malaria 2,3 . Cardiovascular manifestations are prominent components of sickle cell haemoglobinopathy. Most patients show evidence of cardiac dysfunction which manifests principally as fatigue, dyspnoea on exertion, cardiac murmur, cardiomegaly, electrocardiographic 4-6 and echocardiographic abnormalities. 4,6-13

With better medical management, patients with SCA are living longer and what were previously uncommon sequelae are being recognised frequently including those affecting the cardiovascular system. Though SCA is a cause of chronic anaemia, its cardiovascular adaptation may vary in type and degree from other causes of anaemia. The chronicity of the

xvii anaemia, the microthrombi and tissue infarction, the characteristic oxygen undersaturation of arterial blood, the increased viscosity of the red blood cells, and rightward shift of the oxyhaemoglobin dissociation curve probably influence the response of the cardiovascular system in SCA.

Cardiac changes seen in SCA are more marked than other anaemias because of the long standing duration of the anaemia. The reduced oxygen carrying capacity due to anaemia increases demand on the heart with an increase in cardiac output. This increase is achieved in chronic anaemia predominantly by increased stroke volume. Echocardiographic studies of patients with SCA have demonstrated the presence of cardiac chamber enlargement in some patients and have presented evidence of increased left ventricular mass and interventricular septal width.

Studies have looked at ECG changes, left ventricular dimension as well as cardiovascular response to exercise in subjects with SCA. 4,6 Studies have also looked at their left ventricular systolic function in the steady state 4,6,10,11 . Many of these studies had reached different conclusions about LV function in subjects with SCA. There is paucity of studies on sickle cell anaemia patients combining the use of the traditional M-mode, 2D Doppler as well tissue Doppler imaging (TDI) to assess cardiac functions. The TDI can assess both diastolic and systolic functions together. This study therefore aims at assessing the left ventricular geometry and functions of Nigerians with sickle cell anaemia using the conventional M-mode, 2-D, Doppler as well as tissue Doppler imaging (TDI) for comprehensive evaluation.

xviii

Page 2 of 2