title: Influence of preload and afterload on stroke volume response to low-dose dobutamine stress in patients with non-ischemic heart failure: a cardiac MR study.
abstract: BACKGROUND
  Lack of increase in left ventricular (LV) stroke volume (SV) during low-dose dobutamine stress (LDD) is attributed to exhausted cardiac contractile reserve in failing heart. However, the role of the afterload and preload in SV changes is underestimated. The aim of the study was to investigate the effects of LDD on preload reserve and afterload in patients with non-ischemic heart failure.
  
  
  METHODS
  58 patients (age 62 years) underwent LDD (up to 20μg/kg/min) using cardiac magnetic resonance.
  
  
  RESULTS
  LV-SV increased by 27% in 24 patients (p<0.001) (SV+), while decreased by 19% in 22 patients (p<0.001) (SV-). The LDD-to-rest reduction in preload, as defined by LV end-diastolic volume (EDV), was more pronounced in SV- than SV+ (24% and 8% respectively, p<0.05). The LLD-to-rest increase in systolic blood pressure to LV end systolic volume ratio, an index of LV contractility, was higher but not statistically different in SV+ in comparison to SV- (70% vs 48%, p=ns). Systemic vascular resistance during LDD tended to be higher in SV- (23%, p=ns), while it was significantly reduced in SV+ (9.5%, p<0.011), whereas arterial elastance (Ea) increased in SV- (30%, p<0.001) but decreased in SV+ (0.5%, p=0.04). At multivariable regression models LV-EF, LV-EDV and Ea significantly contributed to LV-SV changes in all patients. Also among SV+ and SV- LV-EDV and Ea revealed significant contribution to LV-SV change.
  
  
  CONCLUSIONS
  At similar contractile reserve response, the lack of LDD-induced increase in LV-SV, can be related to reduced preload reserve as well as to increased afterload.
authors.affiliation: CNR Institute of Clinical Physiology, Pisa, Italy. pingi@ifc.cnr.it
authors.forename: Alessandro
authors.initials: A
authors.lastname: Pingitore
authors.forename: Giovanni Donato
authors.initials: GD
authors.lastname: Aquaro
authors.forename: Valentina
authors.initials: V
authors.lastname: Lorenzoni
authors.forename: Maddalena
authors.initials: M
authors.lastname: Gallotta
authors.forename: Daniele
authors.initials: D
authors.lastname: De Marchi
authors.forename: Sabrina
authors.initials: S
authors.lastname: Molinaro
authors.forename: Valentina
authors.initials: V
authors.lastname: Cospite
authors.forename: Claudio
authors.initials: C
authors.lastname: Passino
authors.forename: Michele
authors.initials: M
authors.lastname: Emdin
authors.forename: Massimo
authors.initials: M
authors.lastname: Lombardi
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Lionetti
authors.forename: Antonio
authors.initials: A
authors.lastname: L'Abbate
mesh_terms: D000368:Aged; D004280:Dobutamine; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006333:Heart Failure / Q000175:diagnosis* / Q000503:physiopathology; D006801:Humans; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia; D013318:Stroke Volume / Q000502:physiology*
chemical_list: D004280:Dobutamine