EKG-Veränderungen bei herzkranken Katzen - unter besonderer Berücksichtigeung des Kammerkomplexes -

ECG changes in cats with heart diseases – with special consideration of the ventricular complex In this study 331 cats were examined cardiologically, and the recorded electrocardiograms (ECG) were analyzed. Special attention was paid to the QRS complex. Cardiac and coinciding extracardial diseases were possible causes for the ECG changes. Overall, ECG changes occurred in 294 (88.8 %) of the 331 patients. The most frequent ECG changes in the patient population were changes in the ventricular complex. These were increased amplitudes of the R-wave (35.1 %), deep deflections of the S-wave (11.8 %), arrhythmias (37.8 %) and vector amplitudes ≥1.0 mV in the frontal plane (independent of the vector direction, 18.4%). Increases in the R-wave, using 0.8 mV as limit for increased amplitudes, up to 1,9 mV, were caused by left ventricular hypertrophy (Cardiomyopathies: n=103/286; congenital anomalies: n=9/25; other causes: 4/8). High amplitudes were frequently observed in animals with a coincidence of chronic renal insufficiency (n=28/75) or hyperthyroidism (n=15/28, p=0.0147). Predominantly negative QRS-deflections up to -1.5 mV, resulting from deep S-amplitudes, were caused by right ventricular hypertrophy. Congenital anomalies (n=8/12, p=0.0022) or a coincidence of feline asthma (n=9/24, p=0.0036) caused the deepest amplitudes, and were the most frequent causes (p <0.0001) for negative ventricular complexes, proportionally. Deviations of the QRS-vector in the frontal plane with high vector amplitudes ≥1,0 mV (independent of the vector direction) corresponded to left or right ventricular hypertrophy, and were registered ten times directed cranially and 51 times directed caudally (Cardiomyopathies: n=50/286, congenital anomalies: n=9/37, other causes: n=2/8). Another 56 animals had vectors located outside the standard range (0-160°), but with vector amplitudes <1,0 mV. Arrhythmias were mostly represented by premature beats with 28.1 % (Cardiomyopathies: n=82/286, congenital anomalies: n=9/37, other causes: 2/8). The next most common arrhythmias were tachycardiac arrhythmias with 12.7 % (Cardiomyopathies: n=35/286, congenital anomalies: n=3/37, other causes: 4/8): atrial fibrillation (n=28), missing P-waves (n=8) and ventricular tachycardias (n=6). Further deviations from the normal sinus rhythm were AV blockages (AV-Block 1.°: n=1; AV-Block 3.°: n=7) and excitation spread disturbances (RBBB: n=4; LBBB: n=6; Hemiblock: n=1 [Cardiomyopathies: n=16/286, congenital anomalies: n=3/37]). Additional ECG changes registered in the population were: P-wave increases (n=42), T-wave increases (n=31), prolonged QRS complexes (n=25), and extended QT intervals (n=8). The extent of the ECG changes were associated with the severity or the progression of the disease diagnosed and the clinical symptoms. Since aberrations from standard normal ECG patterns were not recorded in each single ECG, serial registration were essential for the identification of specific ECG changes. This is valid for arrhythmias especially. The ECG has significant clinical relevance for the identification of arrhythmias and, together with other examination methods, it is helpful in the diagnosis and prognosis. Further studies on reference values and individual as well as disease-related differences, such as feline asthma or chronic renal insufficiency, are recommended.