We evaluated the long-term effect of early angiotensin-converting enzyme (ACE) inhibition (enalapril maleate) as monotherapy to postpone or prevent congestive heart failure (CHF) in asymptomatic dogs with mitral regurgitation (MR) attributable to myxomatous valvular disease (MVD) in a prospective, randomized, double-blinded, placebo-controlled multicenter trial involving 14 centers in Scandinavia. Two hundred twenty-nine Cavalier King Charles (CKC) Spaniels with MR attributable to MVD but no signs of CHF were randomly allocated to treatment with enalapril 0.25-0.5 mg daily (n 116) or to placebo groups (n 113). Each dog was evaluated by physical examination, electrocardiography, and thoracic radiography at entry and every 12 months (30 days). The number of dogs developing heart failure was similar in the treatment and placebo groups (n 50 [43%] and n 48 [42%], respectively; P .99). The estimated means, adjusted for censored observations, for the period from initiation of therapy to heart failure were 1,150 50 days for dogs in the treatment group and 1,130 50 days for dogs in the placebo group (P .85). When absence or presence of cardiomegaly at the entrance of the trial was considered, there were still no differences between the treatment and placebo groups (P .98 and .51, respectively). Multivariate analysis showed that enalapril had no significant effect on the time from initiation of therapy to heart failure (P .86). Long-term treatment with enalapril in asymptomatic dogs with MVD and MR did not delay the onset of heart failure regardless of whether or not cardiomegaly was present at initiation of the study.

BackgroundEchocardiography is a cost‐efficient method to screen cats for presence of heart disease. Current reference intervals for feline cardiac dimensions do not account for body weight (BW).ObjectiveTo study the effect of BW on heart rate (HR), aortic (Ao), left atrial (LA) and ventricular (LV) linear dimensions in cats, and to calculate 95% prediction intervals for these variables in normal adult pure‐bred cats.Animals19 866 pure‐bred cats.MethodsClinical data from heart screens conducted between 1999 and 2014 were included. Associations between BW, HR, and cardiac dimensions were assessed using univariate linear models and allometric scaling, including all cats, and only those considered normal, respectively. Prediction intervals were created using 95% confidence intervals obtained from regression curves.ResultsAssociations between BW and echocardiographic dimensions were best described by allometric scaling, and all dimensions increased with increasing BW (all P<0.001). Strongest associations were found between BW and Ao, LV end diastolic, LA dimensions, and thickness of LV free wall. Weak linear associations were found between BW and HR and left atrial to aortic ratio (LA:Ao), for which HR decreased with increasing BW (P<0.001), and LA:Ao increased with increasing BW (P<0.001). Marginal differences were found for prediction formulas and prediction intervals when the dataset included all cats versus only those considered normal.Conclusions and Importance BW had a clinically relevant effect on echocardiographic dimensions in cats, and BW based 95% prediction intervals may help in screening cats for heart disease.

Observer variation in diagnosing mild mitral regurgitation in dogs by cardiac auscultation was assessed by having 6 veterinarians with different levels of experience examine 57 Cavalier King Charles Spaniels. Comparisons with color Doppler echocardiography and phonocardiography were made, and the effects of 2 physical maneuvers on the auscultatory findings were evaluated. Using mildly diseased dogs, interobserver agreement in diagnosing the presence or absence of left-sided murmurs ranged from 63% to 88%. The agreement with phonocardiography (range, 53-91%) increased with the amount of observer experience. The 2 most experienced observers could discern soft ejection murmurs from regurgitant murmurs and were able to diagnose 89% of the dogs with regurgitant jets larger than 30% of the left atrial area. In general, less experienced observers diagnosed most jets larger than 50%. In many dogs with small jets, no murmur was found by auscultation and phonocardiography. The audibility of mild regur-gitation was significantly reduced in dogs that were difficult to auscultate. Early systolic murmurs were typical of mild regurgitation, whereas holosystolic murmurs typified severe regurgitation. In a few dogs, late systolic murmurs alternated with holosystolic murmurs. Systolic clicks were found phonocardiographically in 18 dogs with mild to moderate regurgitation, but the audibility apparently was low. In many mildly affected dogs, physical maneuvers increased murmur intensity. Thus, some form of dynamic auscultation might facilitate the diagnosis of mild regurgitation. Auscultatory findings in mild regurgitation appear to depend on observer experience, circulatory status, and how difficult the dog is to auscultate.

Myxomatous mitral valve disease (MMVD) is the most common heart disease in dogs. It is characterized by chronic progressive degenerative lesions of the mitral valve. The valve leaflets become thickened and prolapse into the left atrium resulting in mitral regurgitation (MR). MMVD is most prevalent in small to medium sized dog breeds, Cavalier King Charles Spaniels (CKCS) in particular. The onset of MMVD is highly age dependent, and at the age of 10 years, nearly all CKCS are affected. The incidence of a similar disease in humans-mitral valve prolapse-is 1-5%. By defining CKCSs with an early onset of MMVD as cases and old dogs with no or mild signs of MMVD as controls, we conducted a genome-wide association study (GWAS) to identify loci associated with development of MMVD. We have identified a 1.58 Mb region on CFA13 (P(genome) = 4.0 × 10(-5)) and a 1.68 Mb region on CFA14 (P(genome) = 7.9 × 10(-4)) associated with development of MMVD. This confirms the power of using the dog as a model to uncover potential candidate regions involved in the molecular mechanisms behind complex traits.

We evaluated the long-term effect of early angiotensin-converting enzyme (ACE) inhibition (enalapril maleate) as monotherapy to postpone or prevent congestive heart failure (CHF) in asymptomatic dogs with mitral regurgitation (MR) attributable to myxomatous valvular disease (MVD) in a prospective, randomized, double-blinded, placebo-controlled multicenter trial involving 14 centers in Scandinavia. Two hundred twenty-nine Cavalier King Charles (CKC) Spaniels with MR attributable to MVD but no signs of CHF were randomly allocated to treatment with enalapril 0.25-0.5 mg daily (n ϭ 116) or to placebo groups (n ϭ 113). Each dog was evaluated by physical examination, electrocardiography, and thoracic radiography at entry and every 12 months (Ϯ30 days). The number of dogs developing heart failure was similar in the treatment and placebo groups (n ϭ 50 [43%] and n ϭ 48 [42%], respectively; P ϭ .99). The estimated means, adjusted for censored observations, for the period from initiation of therapy to heart failure were 1,150 Ϯ 50 days for dogs in the treatment group and 1,130 Ϯ 50 days for dogs in the placebo group (P ϭ .85). When absence or presence of cardiomegaly at the entrance of the trial was considered, there were still no differences between the treatment and placebo groups (P ϭ .98 and .51, respectively). Multivariate analysis showed that enalapril had no significant effect on the time from initiation of therapy to heart failure (P ϭ .86). Long-term treatment with enalapril in asymptomatic dogs with MVD and MR did not delay the onset of heart failure regardless of whether or not cardiomegaly was present at initiation of the study.

Background: Autonomic modulation of heart rhythm is thought to influence the pathophysiology of myxomatous mitral valve disease (MMVD).Hypotheses: (1) Holter-derived variables reflecting autonomic modulation of heart rhythm change with MMVD severity in Cavalier King Charles Spaniels (CKCS); (2) Holter-derived variables can identify MMVD severity in CKCS; and (3) Holter-derived variables in CKCS in congestive heart failure (CHF) secondary to MMVD differ from those in dogs of other breeds in CHF.Animals: Ninety privately owned dogs: 70 CKCS with variable MMVD severity and 20 non-CKCS in CHF secondary to MMVD.Methods: Dogs were prospectively recruited and divided into 5 MMVD severity groups based on history, breed, and physical and echocardiographic examination findings. Holter-derived variables included heart rate variability (HRV), heart rate (HR), and arrhythmia evaluated from 24-hour Holter recordings.Results: In CKCS, 18 of 26 HRV (all P < .0002) and 3 of 9 arrhythmia (all P < .0004) variables decreased with increasing MMVD, whereas minimum and mean HR (all P < .0001) increased with increasing MMVD severity. An arrhythmia variable representing sinus arrhythmia ("premature normals") (P < .0001) and the HRV variable triangular index (TI) (P < .0001) could distinguish CKCS with moderate or severe mitral regurgitation from CKCS in CHF in specific intervals. Among dogs in CHF, Holter-derived variables did not differ among breeds.Conclusions and Clinical Importance: In CKCS, Holter-derived variables changed with MMVD severity. "Premature normals" and TI showed diagnostic potential. Breed differences were not seen among dogs in CHF secondary to MMVD.

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