Objective
To identify a unifying cardiac pathophysiology that explains the cardiac pathology in SCD.
Background
Cardiopulmonary complications, the leading cause of adult mortality in sickle cell disease (SCD), are associated with heart chamber dilation, diastolic dysfunction, elevated tricuspid regurgitant jet velocity (TRV) and pulmonary hypertension (PH). However, no unifying cardiac pathophysiology has been identified to explain these findings.
Methods
In a two-part study, we first examined SCD patients who underwent screening echocardiography during steady state at our institution. We then conducted a meta-analysis of cardiac studies in SCD.
Results
In the 134 SCD patients studied (median age 11 years), a significant enlargement of the left atrial volume was present (z-score 3.1, P=0.002), shortening fraction (SF) was normal (37.6 ± 4.7%), and lateral and septal ratios of mitral velocity to early diastolic velocity of the mitral annulus (E/e′) were severely abnormal in 8% and 14% of patients, respectively, indicating impaired diastolic function. Both TRV and lateral E/e′ correlated with enlarged left atrial volume in SCD (P=0.003 and P=0.006, respectively). Meta-analysis of 68 studies confirmed significant left atrial diameter enlargement in SCD patients compared to controls, evidence of diastolic dysfunction and enlarged left ventricular end-diastolic dimension with normal SF. The majority of patients with catheter-confirmed PH had mild pulmonary venous hypertension consistent with restrictive cardiac physiology.
Conclusions
Patients with SCD have a unique cardiomyopathy with restrictive physiology that is superimposed on hyperdynamic physiology, and is characterized by diastolic dysfunction, left atrial dilation and normal systolic function. This results in mild, secondary, pulmonary venous hypertension and elevated TRV. Sudden death is common in other forms of restrictive cardiomyopathy. Our finding of this unique restrictive cardiomyopathy may explain the increased mortality and sudden death seen in patients with SCD with mildly elevated TRV.