Ventriculo-vascular interactions in patients with β thalassaemia major

Abstract

Objectives: To determine potential interactions between the heart and arterial system in patients with β thalassaemia major. Design and patients: Vascular compliance, systemic vascular resistance, and left ventricular (LV) contractility was determined in 34 asymptomatic thalassaemia patients at 2-4 hours after blood transfusion and also in 34 age and sex matched controls using a non-invasive device. The results were compared between groups and inter-relationships between LV contractility and indices of vascular load were explored. Setting: Tertiary paediatric cardiac centre. Results: When compared with controls, patients had greater systemic vascular resistance (1633 (259) v 1377 (276) dynes/s/cm5, p < 0.001) and effective arterial elastance (Ea (1.86 (0.25) v 1.65 (0.29) mm Hg/ml, p = 0.001), an index of combined pulsatile and static vascular load. On the other hand, their systolic blood pressure (104 (9) v 112 (13) mm Hg, p = 0.006), pulse pressure (45 (9) v 57 (10) mm Hg, p < 0.001), adjusted systemic vascular compliance (1.21 (0.09) v 1.37 (0.14), p < 0.001), adjusted brachial artery distensibility (21 (0.29) v 7.95 (0.29)%/mm Hg, p < 0.001) and LV+dP/dt (1059 (183) v 1239 (237) mm Hg/s, p = 0.001) were significantly lower. Significant determinants of LV contractility, as reflected by LV+dP/dt, were age (standardised β = -0.24, p = 0.003), body mass index (standardised β = -0.34, p = 0.004), systolic blood pressure (standardised β = 0.90, p < 0.001), and effective Ea(standardised β = -0.50, p < 0.001) (model R2 = 0.69). No significant correlation existed between serum ferritin concentration and any of the cardiac or vascular indices. Conclusion: An unfavourable ventriculo-vascular interaction, as characterised by impaired cardiac contractility and increased static and pulsatile vascular load, occurs in patients with β thalassaemia major.