Severe aortic regurgitation due to endocarditis in a horse

A 4-year-old Belgian Warmblood mare was presented because of fever, exercise intolerance, a loud diastolic cardiac murmur and a remarkable bounding pulsation that was palpable all over the body. This bounding pulsation appeared simultaneous with the cardiac contractions. Cardiac ultrasound revealed a vegetation on the aortic valve with severe aortic regurgitation and a second vegetation at the sinus of Valsalva. A reverse flow in the common carotid artery was present during diastole. Left heart catheterization showed left ventricular and aortic pressure curves characteristic of a rather acute development of the lesion. The strong bounding pulsation was caused by severe aortic regurgitation that resulted in a very wide pulse pressure with the occurrence of "Watson's water hammer pulse". Due to the grave prognosis, treatment was not attempted. Necropsy confirmed aortic valve endocarditis

Quantification of left ventricular longitudinal strain, strain rate, velocity and displacement in healthy horses by 2-dimensional speckle tracking

Background: The quantification of equine left ventricular (LV) function is generally limited to short-axis M-mode measurements. However, LV deformation is 3-dimensional (3D) and consists of longitudinal shortening, circumferential shortening, and radial thickening. In human medicine, longitudinal motion is the best marker of subtle myocardial dysfunction. Objectives: To evaluate the feasibility and reliability of 2-dimensional speckle tracking (2DST) for quantifying equine LV longitudinal function. Animals: Ten healthy untrained trotter horses; 9.6 +/- 4.4 years; 509 +/- 58 kg. Methods : Prospective study. Repeated echocardiographic examinations were performed by 2 observers from a modified 4-chamber view. Global, segmental, and averaged peak values and timing of longitudinal strain (SL), strain rate (SrL), velocity (VL), and displacement (DL) were measured in 4 LV wall segments. The inter- and intraobserver within- and between-day variability was assessed by calculating the coefficients of variation for repeated measurements. Results: 2DST analysis was feasible in each exam. The variability of peak systolic values and peak timing was low to moderate, whereas peak diastolic values showed a higher variability. Significant segmental differences were demonstrated. DL and VL presented a prominent base-to-midwall gradient. SL and SrL values were similar in all segments except the basal septal segment, which showed a significantly lower peak SL occurring about 60 ms later compared with the other segments. Conclusions and Clinical Importance 2DST is a reliable technique for measuring systolic LV longitudinal motion in healthy horses. This study provides preliminary reference values, which can be used when evaluating the technique in a clinical setting

The use of cardiac biomarkers in veterinary medicine: the equine perspective

In human medicine, cardiac biomarkers, such as natriuretic peptides and troponins, are routinely used for the diagnosis, prognosis and monitoring of heart diseases. Similarly, these biomarkers are determined in small animals to differentiate non-cardiac from cardiac diseases. Knowledge about these biomarkers in horses is limited and requires further investigation. The first equine studies about atrial natriuretic peptide (ANP) and N-terminal ANP (NT-proANP) are promising, and show a clear correlation with atrial dimension size. Equine brain natriuretic peptides assays are still unavailable. The troponins, in particular troponin I, have been more extensively studied in horses, and their use for the diagnosis of myocardial damage has been fully demonstrated. They have replaced the less specific lactate dehydrogenase and creatine kinase isoenzymes, which makes the use of the last mentioned no longer legitimate. A final possible equine biomarker is aldosterone. Reference values in horses have been established. However, in only one study, a correlation between aldosterone and cardiac disease has been reported

Electrocardiography in horses, part 1: how to make a good recording

Upon auscultation, cardiac dysrhythmias can be suspected, but electrocardiography is the ultimate diagnostic tool. Electrocardiogram (ECG) recording used to be reserved to specialized centers, but nowadays relatively cheap and small recorders are available to the practitioner in the field. ECGs can therefore be recorded ambulatory and during prolonged periods at rest or even during exercise. The know-how of a good quality recording is mandatory for a correct diagnosis. The basic equipment consists of electrodes, a recorder and a way to display the trace. Self-adhesive electrodes should be used, and positioned along the mean electrical axis of the heart. Small recording devices offer the advantage of allowing recordings during exercise. As the electrical impulse spreads through the heart, the ECG trace shows successively a P wave, a QRS complex and a T wave. T-a waves are not always clearly visible in horses. The positioning of the electrodes may differ for ambulatory, exercise or long-term resting recordings. However, as long as the electrodes are positioned along the mean electrical axis, their exact position is not of crucial importance

Electrocardiography in horses, part 2: how to read the equine ECG

The equine practitioner is faced with a wide variety of dysrhythmias, of which some are physiological. The recording of an exercise electrocardiogram (ECG) can help distinguish between physiological and pathological dysrhythmias, underlining the importance of exercise recordings. The evaluation of an ECG recording should be performed in a highly methodical manner in order to avoid errors. Each P wave should be followed by a QRS complex, and each QRS complex should be preceded by a P wave. The classification of dysrhythmias according to their origin helps to understand the associated changes on the ECG. In this respect, sinoatrial nodal (SA nodal), atrial myocardial, atrioventricular nodal (AV nodal) and ventricular myocardial dysrhythmias can be distinguished. Artefacts on the ECG can lead to misinterpretations. Recording an ECG of good quality is a prerequisite to prevent misinterpretations, but artefacts are almost impossible to avoid when recording during exercise. Changes in P or T waves during exercise also often lead to misinterpretations, however they have no clinical significance

Ventricular response during lungeing exercise in horses with lone atrial fibrillation

Reasons for performing the study Atrial fibrillation (AF) is the most important dysrhythmia affecting performance in horses and has been associated with incoordination, collapse and sudden death. Limited information is available on ventricular response during exercise in horses with lone AF. Objectives To investigate ventricular response in horses with lone AF during a standardised lungeing exercise test. Methods A modified base-apex electrocardiogram was recorded at rest and during a standardised lungeing exercise test from 43 horses diagnosed with lone AF. During the test horses walked for 7min, trotted for 10min, cantered for 4min, galloped for 1min and recovered for 7min. Results Individual average heart rate during walk ranged from 42 to 175beats/min, during trot from 89 to 207 beats/min, during canter from 141 to 269 beats/min, and during gallop from 191 to 311 beats/min. Individual beat-to-beat maximal heart rate ranged from 248 to 492 beats/min. Ventricular premature depolarisations were present in 81% of the horses: at rest (16%), during exercise (69%), and during recovery (2%). In 33% of the horses, broad QRS complexes with R-on-T morphology were found. Conclusions Exercising horses with lone AF frequently develop disproportionate tachycardia. In addition, QRS broadening and even R-on-T morphology is frequently found. QRS broadening may originate from ventricular ectopic foci or from aberrant intraventricular conduction, for example due to bundle branch block. This might explain the high number of complexes currently classified as ventricular premature depolarisations. Potential relevance Prevalence of QRS broadening and especially R-on-T was very high in horses with AF and was found at low levels of exercise. These dysrhythmias are considered risk factors for the development of ventricular tachycardia and fibrillation and they might explain signs of weakness, collapse or sudden death that have been reported in horses with AF