Myocardial disease is the most prevalent category of acquired cardiac diseases in cats. As a result of ventricular diastolic or systolic dysfunction, elevated left atrial pressure and left atrial enlargement (LAE) frequently precede left-sided congestive heart failure (CHF). In addition, left atrial function may decline with progressive myocardial disease in affected cats. The left atrium may enlarge in various directions, although is conventionally measured on echocardiography in one-dimension using a short-axis right parasternal view indexed to aortic diameter (LA:Ao). The maximal diameter from a right parasternal long-axis view has also been utilized as an assessment of LA size. Two-dimensional (2D) measurements and volume calculations have replaced one-dimensional linear measurements for chamber quantification in humans and canine echocardiographic exams. The aims of this retrospective study were to compare LA size by conventional 1-dimensional linear measurements to calculated 2D LA volumes (LAV) and compare minimal and maximal values. Our hypothesis was that LAV would provide superior sensitivity (Se) and specificity (Sp) for identifying cats with CHF from those without CHF.
Medical records were reviewed for cats with complete echocardiographic exams performed at the Oregon State University Veterinary Teaching Hospital (OSU-VTH) between January 2008 and July 2017. Cats were categorized into three groups: healthy cats (H group) with a normal echocardiogram and clinical diagnosis; cardiomyopathic cats (CM group) with an echocardiogram consistent with primary cardiomyopathy without clinical or radiographic evidence of CHF; and CHF cats (CHF group) with an echocardiogram consistent with primary cardiomyopathy and with clinical or radiographic evidence of CHF. Hyperthyroid and hypertensive cats were excluded. Seven measurements of LA size were made on each included cat: 1) Minimal LA:Ao (LA:Aom) and 2) Maximal LA:Ao (LA:AoM) according to the Hansson’s method; 3) Minimal LAV and 4) Maximal LAV from the right parasternal long-axis view (LAVmRLA and LAVMRLA); 5) Minimal LAV and 6) Maximal LAV from the left apical view (LAVmLAP and LAVMLAP); and 7) maximal left atrial diameter (LAD) from the right parasternal long-axis view. Volumes were calculated using the monoplane modified Simpson’s method of discs (MOD). Volume measurements were also indexed to body weight (kg). Minimal measurements were made just after the P wave and maximum measurements made just after the T wave on simultaneously recorded ECG. Receiver operator curves were used to assess area under the curve (AUC) and optimal cut-offs with associated Se and Sp to distinguish groups<./p>
A total of 162 cats were included in the study and classified as healthy (n=56), CM (n=62) and CHF (n=44). Healthy cats were younger than both the CM and CHF groups (p < 0.0001) and the groups did not differ in body weight. LAV measurements from the RLA and LAP views were statistically different (p = 0.0005). The LA:Aom and LAVmLAP resulted in the largest AUCs to distinguish CM from CHF cats (AUC = 0.839 and AUC = 0.824, respectively). Indexing LAV to body weight did not increase the AUC for any volume measurement. All seven measurements had poor AUC results to distinguish H and CM cats. The LA:Aom value with the optimal sensitivity and specificity to distinguish CM and CHF cats was 1.635 (Se 84% and Sp 75%). The LAVmLAP raw and indexed values with optimal sensitivity and specificity to distinguish CM and CHF cats were 1.46 mL (Se 73% and Sp 75%) and 0.3 mL/kg (Se 81% and Sp 73%).
Results of this study indicate that LA volumes were not superior to linear measurements of LA size in distinguishing CM and CHF cats. Interestingly, the minimal LA size and volume resulted in a higher AUC than each corresponding maximum measurement. This is in contrast to the currently recommended time point to measure the LA:Ao. Minimum LA size or volume may be a better discriminatory factor as atrial contractile function declines with worsening myocardial disease and the development of CHF.
Small Animal Internal Medicine Intern
Oregon State University
Dr. Laetitia Duler obtained her veterinary degree from the Toulouse School of Veterinary Medicine in Southern France. Upon graduation she completed a small animal rotating internship followed by an internal medicine specialty internship at Oregon State University. Dr. Duler’s clinical and research interests include multimodality imaging and cardiovascular impacts of systemic diseases. Dr. Duler will be starting an emergency and critical care internship at UC Davis in July 2018, with the long-term goal of becoming a board-certified veterinary cardiologist.
Friday, June 15
2:15 PM – 2:30 PM
Friday, June 15
2:30 PM – 2:45 PM
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