Cardiovascular autonomic reflex function in sickle cell anaemia patients.

AIMS AND OBJECTIVES

Cardiovascular autonomic dysfunction (CAD) has been documented as part of neurological complications in sickle cell anaemia (SCA). There is little information on CAD from sub-Saharan Africa with 25-40% prevalence rate of sickle cell trait. This study therefore assessed cardiovascular autonomic reflex function in a group of Nigerians with SCA.

SUBJECTS AND METHODS

Forty SCA and 44 controls (Hemoglobin AA) were studied. They were assessed using 6 non-invasive cardiovascular autonomic reflex (CAR) tests. Parasympathetic functions were assessed with heart rate variability (HRV) to deep breathing, Valsalva maneuver and lying-to-standing test while sympathetic blood pressure regulation was assessed by systolic and diastolic blood pressure responses to lying-to-standing position and isotonic handgrip test.

RESULTS

Mean haemoglobin (Hb) concentration of SCA patients and controls were 8.4 +/- 2.4 g/dl and 13.1 +/- 0.9 g/dl, respectively. Baseline heart rate was significantly faster in the SCA patients (84 +/- 12 beats/minute) than in controls (76 +/- 11 beats/minute) [P < 0.05]. Eleven SCA compared to 2 controls had abnormal responses to deep breathing test (P = 0.003); 15 SCA and 6 controls had impaired Valsalva ratio (P = 0.01); 8 SCA and 4 controls had abnormal responses lying-to-standing test (P = 0.2). Although, more SCA patients compared to controls had abnormal responses to sympathetic mediated blood pressure tests the difference was insignificant (P > 0.05). Overall 21 (53%) SCA patients compared to 4 control subjects (9%) fulfilled the criteria for cardiovascular autonomic neuropathy (presence of e"3 CAR tests) with p < 0.05.

CONCLUSION

CAN occur in Nigerians with SCA with relative preservation of the sympathetic blood pressure reflex control compared to parasympathetic heart rate regulation. Increase baseline heart rate associated with SCA in the presence of chronic anaemia could result in myocardial hypertrophy and dilatation. This is likely to be predispose sicklers to hypoxia-related arrhythmia.