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Abstract A breeding program with the aim of reducing the prevalence of mitral regurgitation (MR) caused by myxomatous mitral valve disease (MMVD) in Cavalier King Charles Spaniels (CKCS) is currently ongoing in Sweden. In this investigation 353 CKCS were selected as a sample of the population and 150 were examined by auscultation for heart murmurs when they reached the age of six years in 2007 and 2009. The aim with this investigation was to study the prevalence of heart murmurs in six-year-old CKCS and to estimate if prevalence has decreased since the breeding program was introduced 2001. The effect of the breeding program was evaluated by comparing the prevalence of heart murmurs in the two groups. In 2007, the prevalence of heart murmurs was 52% (50% for females and 54% for males) and in 2009, the prevalence was 55% (44% for females and 67% for males). No significant difference was found in the prevalence of heart murmurs between 2007 and 2009 (P = 0.8). For all six-year-old CKCS, the prevalence of heart murmur was 53% (females 46% and males 61%), which is higher than previous Swedish investigations.

Background: Training of Standardbred race horses aims to improve cardiovascular and metabolic functions but studies on the effects of different training strategies from breaking till racing are lacking. Sixteen horses with the goal to race as 3-year-olds were studied from breaking (1-year-olds) to December as 3-year-olds. Horses were allocated to either a control (C) or reduced (R) training program from 2 years of age. The aim was to evaluate the effect of reducing the distance of high intensity exercise by 30% with respect to velocity at lactate concentration 4 mmol/l (VLa4), blood lactate and cardiovascular response. All training sessions were documented and heart rate (HR) was recorded. A standardized exercise test of 1,600 m was performed 10 times and a VLa4 test was performed five times. Results: C horses initially exercised for a longer time with a HR >180 beats per minute compared to R horses (P < 0.05) but after 6-9 months, time with HR >180 bpm decreased in C and were similar in the two groups (P > 0.05). Over the 2-year period, recovery HR after the 1,600 m-test decreased in both groups but was within 2 months lower in C than in R (P < 0.05). C horses also had lower resting HR as 3-year-olds (P < 0.01) than R horses. In C, post exercise hematocrit was higher than in R (P < 0.05). There was a tendency (P < 0.1) towards a larger aortic diameter in C as 3-year-olds (C: 1.75 ± 0.05, R: 1.70 ± 0.05 cm/100 kg BW). Left ventricle diameter and blood volume (in December as 2-year-olds) did not differ between groups. There were no differences between groups in post exercise blood lactate concentration or in VLa4. Both groups were equally successful in reaching the goal of participation in races. Conclusions: Horses subjected to a reduced distance of high intensity training from the age of 2 showed an attenuated heart rate response, but were able to maintain the same VLa4 and race participation as horses subjected to longer training distances. [ABSTRACT FROM AUTHOR]

The respiratory pressure changes in the trachea were recorded in five normal experimental standardbred horses (trotters) at rest and during standardized exercise produced by trotting on a treadmill at different speeds. For recording of the intratracheal pressure, a teflon catheter supplied with devices to prevent kinking was inserted into the trachea by a special technique. The catheter was connected to a pressure transducer placed on the horse's neck. The signals from the transducer were recorded with an ink jet writer. The studies of the intratracheal pressure were carried out both with the horses in the intact state and - in two horses - after crushing the recurrent laryngeal nerve. On investigation of the horses in the intact state, it was found that two of them displayed an 'anomaly' in the respiratory pressure course that has not been described previously in the trotting horse. After crushing the recurrent laryngeal nerve, the intratracheal pressure course at the high work loads showed a radical change. The most obvious alterations were a prolongation of the inspiratory phase, an increase in the inspiratory negative pressure and a tendency towards formation of a plateau on the pressure curve during inspiration. The evaluation of the pressure recordings included measuring of the area on the recording paper that was delimited by the zero line and the inspiratory pressure graph. This variable, which is supposed to be influenced by the three above-mentioned factors, increased with the work load to a much greater extent in the horses that had been subjected to crushing of the recurrent laryngeal nerve than in the same horses in the intact stale and in the controls. The authors propose a method for calculating an approximate 'comparison factor' for the mean resistance in the upper airways during the inspiratory phase, based on the recordings of the intratracheal pressure. Zusammenfassung Untersuchungen über den intratrachealen Druck beim arbeitenden Pferd Bei fünf normalen Versuchspferden (Traber) wurden die atmungsbedingten Druckveränderungen in der Trachea während der Ruhe und während eines standardisierten Trabs verschiedener Geschwindigkeit auf einem Laufband registriert. Für die Registrierung des intratrachealen Drucks wurde ein Teflon-Katheter mit einer Vorrichtung, die das Abknicken verhinderte, mit einer speziellen Technik in die Trachea eingeführt. Der Katheter wurde mit einem am Hals des Pferdes plazierten Druckwandler verbunden. Die Wandlersignale wurden mit einem Tinten-Düsen-Schreiber registriert. Der intratracheale Druck wurde bei gesunden Pferden und bei zwei Pferden nach Quetschung des Nervus recurrens laryngealis untersucht. Bei den Untersuchungen an den gesunden Pferden wurde bei zwei Tieren eine 'Anomalie' im Druckverlauf während der Atmung festgestellt, die bisher bei Trabern noch nicht beschrieben worden war. Nach Quetschung des Nervus recurrens laryngealis zeigte der Verlauf des intratrachealen Drucks bei starker Arbeit ausgeprägte Veränderungen. Die auffälligsten Veränderungen waren eine Verlängerung der Inspirationsphase, eine Zunahme des inspiratorischen negativen Drucks und eine Tendenz zur Plateaubildung im Verlauf der Druckkurve während der Inspiration. Die Auswertung der Druckaufzeichnungen schloß die Bestimmung der Fläche auf dem Registrierpapier ein, die durch die Null-Linie und die während der Inspiration registrierte Druckkurve begrenzt wurde. Diese wahrscheinlich durch die drei oben erwähnten Faktoren beeinflußte Größe nahm bei den Pferden nach Quetschung des Nervus recurrens laryngealis mit zunehmender Arbeitsleistung sehr viel stärker zu als bei den Pferden im unversehrten Zustand und den Kontrolltieren. Die Autoren schlagen, von den Aufzeichnungen des intratrachealen Drucks ausgehend, eine Methode zur Berechnung eines 'Vergleichsfaktors' zur Beurteilung des mittleren Strömungswiderstandes der oberen Luftwege während der Inspirationsphase vor. [ABSTRACT FROM AUTHOR]

Objective--To investigate whether time-frequency and complexity analyses of heart murmurs can be used to differentiate physiologic murmurs from murmurs caused by aortic stenosis (AS) in Boxers. Animals--27 Boxers with murmurs. Procedures--Dogs were evaluated via auscultation and echocardiography. Analyses of time-frequency properties (TFPs; ie, maximal murmur frequency and duration of murmur frequency > 200 Hz) and correlation dimension (T2) of murmurs were performed on phonocardiographic sound data. Time-frequency property and T2 analyses of low-intensity murmurs in 16 dogs without AS were performed at 7 weeks and 12 months of age. Additionally, TFP and T2 analyses were performed on data obtained from 11 adult AS-affected dogs with murmurs. Results--In dogs with low-intensity murmurs, TFP or T2 values at 7 weeks and 12 months did not differ significantly. For differentiation of physiologic murmurs from murmurs caused by mild AS, duration of murmur frequency > 200 Hz was useful and the combination assessment of duration of frequency > 200 Hz and T2 of the murmur had a sensitivity of 94% and a specificity of 82%. Maximal murmur frequency did not differentiate dogs with AS from those without AS. Conclusions and Clinical Relevance--Results suggested that assessment of the duration of murmur frequency > 200 Hz can be used to distinguish physiologic heart murmurs from murmurs caused by mild AS in Boxers. Combination of this analysis with T2 analysis may be a useful complementary method for diagnostic assessment of cardiovascular function in dogs. [ABSTRACT FROM AUTHOR]

Two-dimensional (2-D) echocardiographic measurement of the left atrium (LA) has the potential to be more accurate than the standard M-mode method, because the LA body can be measured. We evaluated a 2-D method for measuring LA and aorta (AO) in a right parasternal short-axis view and compared it to the M-mode method. An index for LA size (LA/AO) was calculated in 166 cavalier King Charles spaniels, 56 normal and 110 dogs with mitral regurgitation (MR) of varying degrees secondary to chronic valvular disease. In normal dogs, the AO-2-D and LA/AO-2-D did not correlate to body weight (BW) or BW2; whereas, all M-mode values and the LA-2-D were significantly (p < .05) related to both BW parameters. In normal dogs, there was no difference between M-mode and 2-D indices. For all dogs (normal and dogs with MR) there was an 11% bias between the M-mode and 2-D index with the LA/AO-2-D being higher than the LA/AO-M. The association between the mean and the difference of the indices demonstrated a quadratic relationship. Dogs with a mean LA/AO of 2.0-2.5 showed the largest difference between the two indices. Small values for the 2-D coefficients of variation for respiration and stage of diastole were found; 3.4 and 3.1%, respectively. The 2-D index is more sensitive to LA enlargement than the M-mode index.