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Administration of pimobendan to dogs with preclinical myxomatous mitral valve disease (MMVD) with cardiomegaly (stage B2 mitral valve disease, Atkins et al., 2009) has been shown to extend the asymptomatic period by an average of 15 months, and dogs receiving the drug live significantly longer than those receiving a placebo (Boswood et al., 2016). The identification in general veterinary practice of patients with MMVD who could benefit from this medication relies heavily on the accurate identification of a heart murmur on a physical examination and identification of cardiomegaly, including left atriomegaly, on thoracic radiographs. Little is known about the ability of general practitioners to identify these patients accurately. To investigate this in more detail, practitioner record keeping in relation to cardiovascular parameters, practitioner accuracy in interpretation of cardiac murmurs (Chapter 1) and practitioner accuracy in identification of cardiomegaly and left atriomegaly on thoracic radiographs (Chapter 2) was assessed. To identify methods that might aid the detection of cardiovascular disease in general practice, the value of focused echocardiography was assessed. Record keeping by general veterinary practitioners for important cardiovascular parameters was markedly limited in standard. General practitioners, compared with a referral clinician consensus opinion, agreed substantially on murmur grade (K = 0.7), agreed perfectly on murmur timing (K = 1.0) and moderately on the site of maximum intensity of murmurs (K = 0.5). These findings would suggest that practitioners are able to accurately grade a heart murmur and therefore could potentially correctly select patients who would benefit from further investigation, confirming the cause of the murmur as MMVD and therefore potentially benefit from medication. However due to poor record keeping, the loss of information may prevent the identification of patients in early stages of heart disease or patients who might benefit from further cardiovascular investigation. When assessing thoracic radiographs for changes associated with MMVD (Chapter II), general practitioners were found to have a high level of accuracy in the detection of patients with marked generalised cardiomegaly (median number of images correctly identified was 100%) and patients with no left atrial enlargement (median number of images correctly identified was 80%) using subjective methods of assessment. However, their accuracy was lower in detection of those with mild changes (median number of images correctly identified with mild cardiomegaly and mild left atrial enlargement was 66.67%). Whilst practitioners were accurate in their ability to measure a vertebral heart score (VHS), the lack of a clear upper limit for VHS meant that VHS added no significant value in aiding correct diagnosis. Patients in stage B2 MMVD (Atkins et al., 2009) have mild changes on thoracic radiographs, therefore this research suggests that in general practice patients in the early stages of cardiac remodelling, and those who might benefit greatly from medication, may go undiagnosed. This highlights that radiographic examination may not be sufficiently reliable in the evaluation of mild cardiomegaly and emphasizes the need for echocardiography to assist in the detection of patients with B2 MMVD. The introduction of the novel tool of focused echocardiography (Chapter 3) significantly improved general practitioner’s ability to correctly identify cardiac anatomy on echocardiography, detect left atrial enlargement, detect reduced systolic function and detect pericardial effusion (p |
