Dynamic dyssynchrony and impaired contractile reserve of the left ventricle in beta-thalassaemia major: an exercise echocardiographic study

PLoS One. 2012;7(9):e45265. doi: 10.1371/journal.pone.0045265. Epub 2012 Sep 18.

Abstract

Background: Performance of the left ventricle during exercise stress in thalassaemia patients is uncertain. We aimed to explore the phenomenon of dynamic dyssynchrony and assess contractile reserve in patients with beta-thalassaemia major and determine their relationships with myocardial iron load.

Methods and results: Thirty-two thalassaemia patients (16 males), aged 26.8 ± 6.9 years, without heart failure and 17 healthy controls were studied. Their left ventricular (LV) volumes, ejection fraction, systolic dyssynchrony index (SDI), and myocardial acceleration during isovolumic LV contraction (IVA) were determined at rest and during submaximal bicycle exercise testing using 3-dimensional and tissue Doppler echocardiography. Myocardial iron load as assessed by T2* cardiac magnetic resonance in patients were further related to indices of LV dyssynchrony and contractile reserve. At rest, patients had significantly greater LV SDI (p<0.001) but similar IVA (p = 0.22) compared with controls. With exercise stress, the prevalence of mechanical dyssynchrony (SDI>4.6%, control+2SD) increased from baseline 25% to 84% in patients. Δ SDI(exercise-baseline) correlated with exercise-baseline differences in LV ejection fraction (p<0.001) and stroke volume (p = 0.006). Compared with controls, patients had significantly less exercise-induced increase in LV ejection fraction, cardiac index, and IVA (interaction, all p<0.05) and had impaired contractile reserve as reflected by the gentler IVA-heart rate slope (p = 0.018). Cardiac T2* in patients correlated with baseline LV SDI (r = -0.44, p = 0.011) and IVA-heart rate slope (r = 0.36, p = 0.044).

Conclusions: Resting LV dyssynchrony is associated with myocardial iron load. Exercise stress further unveils LV dynamic dyssynchrony and impaired contractile reserve in patients with beta-thalassaemia major.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Case-Control Studies
  • Echocardiography, Doppler
  • Exercise Test
  • Female
  • Heart Ventricles / diagnostic imaging
  • Heart Ventricles / pathology
  • Heart Ventricles / physiopathology*
  • Humans
  • Iron / analysis
  • Magnetic Resonance Imaging
  • Male
  • Myocardial Contraction
  • Myocardium / chemistry
  • Myocardium / pathology*
  • Stroke Volume
  • Ventricular Dysfunction, Left / complications
  • Ventricular Dysfunction, Left / diagnostic imaging
  • Ventricular Dysfunction, Left / pathology
  • Ventricular Dysfunction, Left / physiopathology*
  • beta-Thalassemia / complications
  • beta-Thalassemia / diagnostic imaging
  • beta-Thalassemia / pathology
  • beta-Thalassemia / physiopathology*

Substances

  • Iron

Grant support

This study was supported by the Research Grants Council of the Hong Kong Special Administrative Region, China (Project no. HKU763309M) and Children’s Thalassaemia Foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.