Prognostic Significance of Left Atrial Systolic Dysfunction in Cats with Hypertrophic Cardiomyopathy
V. Simons; J.R. Payne; D. Connolly; V. Luis Fuentes
Department of Veterinary Clinical Sciences, The Royal Veterinary College, North Mymms, Hatfield, Hertfordshire, UK
Introduction
Hypertrophic cardiomyopathy (HCM) is a common primary myocardial disease characterised by idiopathic left ventricular hypertrophy and a variable prognosis. We hypothesised that among cats with idiopathic HCM, those with left atrial (LA) systolic dysfunction would have shorter survival times than those with normal LA systolic function.
Materials and Methods
Patient records from 2004 to 2009 were reviewed for all cats diagnosed with HCM by the Cardiology Service of the Royal Veterinary College Queen Mother Hospital for Animals (QMHA). Cats were excluded if an underlying cause of the left ventricular hypertrophy was identified or for inadequate quality of echocardiographic images. Survival times were obtained by reviewing QMHA clinical records and contacting referring practices or owners by phone or questionnaires. Survival was calculated as time from the echocardiographic examination to the date of cardiac death or date last reported alive, and non-cardiac deaths or cats still alive were right-censored. A control group of 21 cats without cardiac disease was used to establish normal reference intervals. The standard measure of LA size was the 2D ratio of LA to aortic diameter in short axis (LA/Ao). Echocardiographic measures of LA systolic function included M-mode LA fractional shortening (%FSLA) using anatomic M-mode from a 2D right parasternal short axis view and 2D LA emptying fraction (%EFLA) from single-plane maximal and minimal LA volumes from a 2D right parasternal long axis view. Data were analysed as quartiles using Kaplan-Meier and Log Rank analyses.
Results
The control value for mean %FSLA was 27.2 ± 4.77%, and mean %EFLA was 64.5 ± 7.75%. Among the 244 cats with HCM meeting the inclusion criteria, LA/Ao was negatively associated and %FSLA and %EFLA were positively associated with survival (p < 0.0001). Median survival was 213 days for cats in the lowest %EFLA quartile (< 27%) versus 2153 days in the upper %EFLA quartile (> 61.9%).
Conclusions
LA systolic function has important prognostic significance and should be included in the echocardiographic assessment of cats with HCM.