Determination of heart rhytm disturbances with holter ECG and investigation of relation between different stages of myxomatous mitral valve disease and heart rhytm disturbances in dogs

Myxomatous mitral valve disease (MMVD) is the most common acquired heart disease in dogs that causes congestive heart failure. Arrhythmias are common findings in dogs with MMVD, and the incidence and severity of these arrhythmias are known to be higher in animals with clinical disease. Holter electrocardiography (Holter ECG) is a method that has been frequently used in human medicine and in recent years in veterinary medicine to detect the frequency and incidence of cardiac arrhythmias. This diagnostic method is much more sensitive and reliable than the standard ECG method in detecting serious, life-threatening arrhythmias. Moreover, in addition to echocardiography, electrocardiographic measurements and various ventricular repolarization markers are thought to be useful in the diagnostic and prognostic evaluation of MMVD. Our prospective thesis study aimed to contribute to the diagnostic and prognostic methodology of the disease. For this purpose, rhytym disorders that develop in dogs with preclinical and clinical MMVD and cannot be detected by Standard ECG and electrocardiographic markers that can be analyzed with Holter ECG has been determined and their distribution, change and relationship with the progression of the disease has been investigated. Moreover, the very first Holter ECG application at Istanbul University Cerrahpaşa Faculty of Veterinary Medicine, Department of Internal Medicine has been carried through. For this purpose, B1 level (n=9), B2 level (n=8), C level (n=8), D level (n=8) and Healthy (n=8) dogs according to the ACVIM classification were included in our study. Hemogram, biochemical blood parameters, thorax radiographs, echocardiography, NT-ProBNP and cTnI values, Standard ECG data and different periods of Holter ECG recordings of all dogs were evaluated. Additionally, the relationship between the MINE scoring system that used for MMVD severity classification and electrocardiographic parameters was evaluated for the first time. In our study, highest diagnostic success among the parameters in terms of cardiac remodeling and congestive heart failure was Tpte value, which is the interval between T wave peak and T wave end, measured on the II. amd aVF derivation. Predictive percentages of Tpte II and Tpte aVF for cardiac remodeling were 78,1% and 73,8% in the Standard ECG (p<0,01 ve p=0,01), 74,4% and 76,3% in the Holter ECG sleep period (p<0.01), 71,2% and 72,3% in the wakefullness period (p<0.05), 76,5% and 74% in the exercise period (p<0,01 ve p=0,01), respectively. The prediction percentages for congestive heart failure were 92,1% and 89,9% in the Standard ECG (p<0.01), 82,8% and 84,9% in the Holter ECG sleep period (p<0.01), 85,4% and 87,4% in the wakefullness period (p<0.01), 85,5% and 87,3% in the exercise period (p<0.01), respectively. In our study, no rhythm disturbance was detected with both Standard and Holter ECG in the healthy group. While no arrhythmia was detected with the Standard ECG in the B1 group, supraventricular arrhythmia was detected in 44% of the cases with the Holter ECG. Arrhytmia incidence rates were 25% in Standard ECG and 50% in Holter ECG for group B2, 25% in Standard ECG and 87.5% in Holter ECG for group C, 75% in Standard ECG and 100% in Holter ECG for group D. In conclusion; ventricular repolarization markers Tpte was found to be superior in predicting cardiac remodeling and congestive heart failure in MMVD disease compared to repolarization markers such as QT duration and QTc, which are affected by heart rate. We believe that ventricular repolarization markers, and especially the Tpte II and Tpte aVF can be used in clinical practice for diagnostic and prognostic evaluation and to determine the risk of cardiac remodeling and congestive heart failure in patients with MMVD.