Subnormal Effective Forward Cardiac Index in Congenital Heart Disease with Right Ventricular Loading: Assessment by Magnetic Resonance Imaging

  • Dr Boris Lowe, McGill University Adult Unit for Congenital Heart Disease Excellence (MAUDE Unit) , Montreal, Canada
  • Dr Ariane Marelli, McGill University Adult Unit for Congenital Heart Disease Excellence (MAUDE Unit) , Montreal, Canada
  • Dr Luc Jutras, McGill University Adult Unit for Congenital Heart Disease Excellence (MAUDE Unit) , Montreal, Canada
  • Dr Natalie Bottega, McGill University Adult Unit for Congenital Heart Disease Excellence (MAUDE Unit) , Montreal, Canada
  • Dr Giuseppe Martucci, McGill University Adult Unit for Congenital Heart Disease Excellence (MAUDE Unit) , Montreal, Canada
  • Dr Judith Therrien, McGill University Adult Unit for Congenital Heart Disease Excellence (MAUDE Unit) , Montreal, Canada

    • Objective: We sought to assess the determinant variables of a low cardiac index among ambulatory patients with congenital heart disease (CHD) and haemodynamic loading of the right ventricle (RV).

    Methods: One hundred consecutive patients (mean age 32±14 years, 48% female) aged >18 years with CHD referred for magnetic resonance imaging to assess the RV were included. Effective forward cardiac index (CIeff, subnormal defined as <2.6 l/min/m2) was derived from ventricular volumetric and great arterial phase-encoded velocity mapping, calculated by [end-diastolic volume (EDV) – end-systolic volume (ESV)) – valvular regurgitant volume] x heart rate (HR) / body surface area.

    Results: More than one quarter of the study population had a low LVCIeff. Prior reparative surgery, beta-adrenergic receptor antagonist medication, RV pressure and volume loading conditions were similar between patients with low and normal CIeff. Almost half of the patients with subnormal CIeff were asymptomatic. Patients with subnormal LVCIeff were characterised by smaller indexed LVEDV, smaller RV forward stroke volume and larger total (tricuspid and pulmonic) RV regurgitant volume (table). Valvular regurgitation even of modest severity appears to be an integral contributor to low forward stroke volumes ejected from a RV already haemodynamically stressed by CHD. Smaller indexed LV cavity volumes may reflect consequential LV preload deprivation.

    Conclusions: Low cardiac forward flow is not uncommon among ambulatory patients with CHD and is not identified by symptomatic status, RV cavity volumes and ejection fraction. Assessment for valvular regurgitation of any severity is requisite when evaluating effective cardiac function.