The prevalence of the third and fourth heart sounds in clinically healthy Holstein cattle

Three hundred clinically healthy Holstein cattle from 12 dairy farms in Shiraz area were chosen randomly for population to be studied. About 10 minutes after restraining the animals in a stock, the cardiac area was auscultated by two clinicians independently and systematically by a Littman type stethoscope without consulting with each other and then both clinicians listened the heart sounds simultaneously using a sensor stethoscope (Mediron stethoscopes AS, Norway) focusing on the transient heart sounds and cardiac murmurs according to criteria have been presented [4,5]. Before auscultation both sides of cardiac area was palpated for the detection of apex beat. Then stethoscope was placed on the area of the thorax in which apex beat was most clear and attention was focused on the first and second heart sounds and then the stethoscope was moved to the mitral, aortic, pulmonary and tricuspid valves area. The right side of the cardiac area was also auscultated. The age, hear rate and clinical signs of heart disease such as jugular distention and pulsation, edema and thrill were taken into consideration. Animals with the signs of heart diseases were not included in this study.The results of this study showed that the third heart sound was audible in 8.7% of animals and 29.3% demonstrated the fourth heart sound (Table 1). The prevalence of the fourth heart sound was significantly higher in cattle older than 48 months. None of the calves younger than twelve months had the third heart sound. Both sounds were more prevalent in older ages. There was a reverse correlation between the heart rate and the 4th heart sound. The higher the heart rate the less chance was to hear the 4th heart sounds. The percentage of audible fourth heart sound in the heart rate of higher and lower than 100 BPM was 10.3% and 36% respectively, which was statistically significant (F = 18,5, df = 1, P = 0.000).'It has been mentioned that the 3rd heart sound can be heard when heart rate increases [6,2].