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LEFT ATRIAL ENLARGEMENT (LAE) IN DOGS

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  2. LEFT ATRIAL ENLARGEMENT (LAE) IN DOGS
  3. URINARY TRACT INFECTIONS IN DOGS RECEIVING CICLOSPORIN

Many dogs with cardiac disease show enlargement of the left atria and this is often associated with the development of left sided congestive heart failure. Cardiac enlargement is assessed using electrocardiography, radiography and/or echocardiography, with the latter two commonly used to assess specifically for atrial enlargement. Electrocardiography, particularly a prolonged P wave may indicate increased atrial mass, although such a finding may also indicate atrial conduction disorders which therefore make P wave duration an unreliable index of LAE. Savarino and others recently reported on their investigation into the usefulness of P wave duration in the determination of LAE in dogs (Diagnostic performance of P wave duration in the identification of left atrial enlargement in dogs (2012). Journal of Small Animal Practice 53: 267–272). They compared ECG assessment with echocardiography, with the aim of quantifying its diagnostic performance.

For 156 dogs of mixed breed and sex included in the study electrocardiographic data including the duration of the P wave measured in lead II was compared to left atrial dimensions measured in echocardiograms and represented as a ratio between the left atrium and aortic dimensions (LA/Ao). The population comprised 58 healthy dogs, 45 with mitral valve disease, 28 with tricuspid valve dysplasia, 13 with pulmonic stenosis and 87 ‘other’ cardiac diseases. Normal left atrial dimensions were recorded in 106 dogs, whilst 50 had LAE, of which 16 had mild, 11 moderate and 23 severe LAE.

Differences in P wave duration were evident between groups, with dogs with normal left atrial dimensions or mild LAE showing shorter P wave durations than dogs with severe LAE. Bodyweight and age were positively associated with P wave duration, that is, there was an increase in P wave duration as weight was gained and the dog aged. The significance of this increase in P wave duration with increased age and body weight was not discussed in detail by the authors and the observation agrees with previous studies. The data also indicated that mean P wave durations of 20, 30, 40 and 50 milliseconds were associated with sensitivities of 100, 85, 68 and 40% and specificities of 0, 16, 64 and 93%, respectively, with LAE. Thus, the longer the P wave duration the more false negative cases are identified, whilst with shorter P wave durations a low specificity suggests a higher false positive rate.

Changes in the left atrium may be associated with extended left atrial depolarization, which can manifest as an increase in the P wave duration on the ECG. The authors describe an association between P wave duration and LA/Ao by echocardiography, but their ability to predict LAE by using the P wave duration was poor. The authors conclude that P wave duration on its own did not reliably detect LAE which is similar to man where P wave changes, including duration, axis and morphology, are also unreliable in demonstrating atrial enlargement, when compared to a gold standard assessment method.

URINARY TRACT INFECTIONS IN DOGS RECEIVING CICLOSPORIN

  1. Top of page
  2. LEFT ATRIAL ENLARGEMENT (LAE) IN DOGS
  3. URINARY TRACT INFECTIONS IN DOGS RECEIVING CICLOSPORIN

Ciclosporin A (CsA), an immunomodulatory drug indicated in the management of some inflammatory skin disorders, is associated with various adverse effects including vomiting, diarrhoea and urinary tract infections. It is often used with glucocorticoids, which are also recognised to increase the risk of UTI, and it suggested that the frequency of UTI may be increased when both are used. Peterson and others have recently reported on their study to determine the frequency of UTI in dogs receiving CsA with or without concurrent glucocorticoid therapy (Frequency of urinary tract infection in dogs with inflammatory skin disorders treated with ciclosporin alone or in combination with glucocorticoid therapy: a retrospective study (2012). Veterinary Dermatology 23: 201). The study included 87 dogs with inflammatory skin disorders receiving CsA (16 dogs also received glucocorticoids) and 59 control dogs with similar conditions that had not received glucocorticoids or ciclosporin for six months.

In the group of dogs receiving CsA a total of 273 urine samples were cultured with 26 dogs having at least one positive culture; 34 urine cultures were positive for one organism, six for two organisms, and two for three organisms, and seven species of bacteria were isolated. For all the treated dogs 15% of samples were positive compared to 3% of samples from control dogs. Within the treated population 25% of samples from dogs receiving CsA and glucocorticoids were culture positive compared to 13% of samples from dogs receiving CsA only. These differences were not statistically significant.

Urinalysis was performed on 253 occasions with 29 samples showing bacteraemia, four of which were culture negative and 15 negative for bacteraemia but which were culture positive. The authors looked at sensitivity and specificity data for various urine parameters and reported that the sensitivity and specificity for predicting a UTI were 64.1 and 98.1% for bacteraemia, 74.4 and 70.9% for pyuria, and 56.4 and 65.3% for urine specific gravity. These results suggest that the sensitivity of bacteraemia as a reliable indicator of UTI was only 64.1% (15 false negative samples), that dogs receiving CsA therapy require urine culture for assessment of a UTI. As the false positive rate is low, indicated by the high specificity of 98.1%, if bacteraemia is present in the dog a UTI should be assumed to be present in which case antibacterials can be started earlier, and cultures may not be necessary other than to guide antibacterial selection.

The authors concluded that there was an ‘increased risk for UTI in dogs on at least five months of CsA therapy with or without glucocorticoids compared with control dogs’ and that ‘30% of dogs receiving CsA with or without glucocorticoids had positive urine bacterial cultures during the study period in the absence of clinical signs of UTI’. They suggest ‘that routine urine cultures and urinalysis for bacteraemia should be part of the monitoring for dogs on these medications’.