Background: In human medicine, right ventricular (RV) functional parameters represent a tool for risk stratification in patients with congestive heart failure caused by left heart disease. Little is known about RV alterations in dogs with left-sided cardiac disorders. Objectives: To assess RV and left ventricular (LV) function in dogs with myxomatous mitral valve disease (MMVD) with or without pulmonary hypertension (PH). Animals: One-hundred and fourteen dogs: 28 healthy controls and 86 dogs with MMVD at different stages. Methods: Prospective observational study. Animals were classified as healthy or having MMVD at different stages of severity and according to presence or absence of PH. Twenty-eight morphological, echo-Doppler, and tissue Doppler imaging (TDI) variables were measured and comparison among groups and correlations between LV and RV parameters were studied. Results: No differences were found among groups regarding RV echo-Doppler and TDI variables. Sixteen significant correlations were found between RV TDI and left heart echocardiographic variables. Dogs with PH had significantly higher transmitral E wave peak velocity and higher E/eʹ ratio of septal (sMV) and lateral (pMV) mitral annulus. These 2 variables were found to predict presence of PH with a sensitivity of 84 and 72%, and a specificity of 71 and 80% at cut-off values of 10 and 9.33 for sMV E/eʹ and pMV E/eʹ, respectively. Conclusions and clinical importance: No association between variables of RV function and different MMVD stage and severity of PH could be detected. Some relationships were found between echocardiographic variables of right and left ventricular function.

Background: Supraventricular tachycardias (SVTs), despite having various anatomical substrates and pathophysiological mechanisms, frequently show similar electrocardiographic presentations. Objectives: To locate and characterize atrial deflections (ADs) on 12-lead electrocardiograms in dogs with sustained rapid SVT and assess the utility of different electrocardiographic variables in differentiating types of tachycardia. Animals: Ninety-two dogs with orthodromic atrioventricular reciprocating tachycardia, 17 with atrial flutter, 33 with focal atrial tachycardia recorded and confirmed by electrophysiological study, and 40 dogs with sinus tachycardia. Methods: Atrial deflection position on the 12-lead surface electrocardiogram was assessed according to the sequence of intracardiac activation. Its features were evaluated together with the relationship between AD and QRS complex interval (AD-R) and QRS complex and AD interval (R-AD). Results: Orthodromic atrioventricular reciprocating tachycardia was characterized by an AD-AD interval of 213 ± 30 ms, mean electrical axis (MEA) of AD of −90 (−90/−78)°, R-AD interval of 75 (65-80) ms, and R-AD/AD-R of 0.54 (0.45-0.64). Atrial flutter was characterized by an AD-AD interval of 199 ± 57 ms, MEA of 76° (72/81), R-AD of 120 (72-144) ms, and R-AD/AD-R of 0.81 (0.63-1.13). Focal atrial tachycardia was characterized by an AD-AD interval of 270 ± 38 ms, MEA of 49 (−72/76)°, R-AD of 160 (120-200) ms, and R-AD/AD-R of 1.45 (0.92-1.67). Sinus tachycardia was characterized by an AD-AD interval of 292 ± 31 ms, MEA of 66° (52/73), R-AD of 215 (192-222) ms, and R-AD/AD-R of 2.68 (2.25-3.08). Conclusions and Clinical Importance: Analyzing AD on 12-lead electrocardiogram is helpful in differentiating the most common SVTs in dogs.

Objective: To evaluate the accuracy of recordings of atrial and ventricular depolarizations in 9-lead ECG of cats, with V1 placed at the right first intercostal space at the costochondral junction and V2 and V4 at the fifth or the sixth intercostal space (adjacent to the sternum and at the costochondral junction), and to assess the effect of age-related cardiac positional changes on ECG parameters. Methods: 60 healthy client-owned cats were planned to be enrolled from January 1, 2024, through December 31, 2024. Each cat underwent physical examination, thoracic radiography, 9-lead ECG, and echocardiography. Cats were age-grouped (< 5, 5 to 10, and > 10 years). The radiographic heart-sternum angle (HSA) in right lateral view was measured and correlated with ECG findings. Results: The V1 location enabled recording of negative P waves and QRS complexes with R/S ≤ 1, with significant intergroup differences (0.68 ms [IQR, 0.42], 0.37 ms [IQR, 0.32 ms], and 0.48 ms [IQR, 0.65 ms]; P = .04). In V2 and V4 in both sites, P waves were predominantly positive, and QRS complexes showed R/S > 1, with minimal intergroup differences. Aging was associated with a significant HSA reduction ( r = −0.72) but did not affect any clinically relevant ECG variables. Conclusions: This 9-lead system, with V1, V2, and V4 positioned as in dogs, enabled accurate P waves and QRS recording in cats. Aging reduced HSA without major effects on wave morphology. Clinical Relevance: This system will support detailed arrhythmias analysis in feline patients.

Idiopathic pericarditis (IP) and pericardial mesothelioma (PM) are causes of pericardial effusion in dogs. Pericardiectomy can be a definitive treatment in the case of idiopathic pericardial effusion or a short-term intervention for mesothelioma. The aim of the present study was to investigate which histopathologic parameters are correlated with clinical outcomes in a cohort of dogs that underwent pericardiectomy. The histopathological findings of 22 IPs and 5 PMs were compared with clinical and survival data and the immunohistochemical characterization of immune cells (CD3, CD79α, Iba1). In IP, the mesothelium was lost in 20 cases, reactive in 9, atypical in 3, and mesothelial papillary hyperplasia (MPH) was observed in 4 cases. Numerous macrophages were found in both IPs and PMs especially at the superficial layer of the pericardium. T lymphocytes were observed in mild to moderate numbers and were more numerous than B lymphocytes in both IPs and PMs. MPH was correlated with the quantity of lymphoplasmacytic infiltrate in the superficial layer, inversely related to the thickness of the pericardium, and associated with a longer overall survival. Pericardial fibrosis was present in 19 out of 22 IPs and in all mesotheliomas and was correlated with increased time from initial presentation and pericardiectomy and lymphoplasmacytic infiltrate in the deep zone. Pericardial thickness was correlated with the amount of lymphoplasmacytic and macrophagic infiltrate in the deep zone. Mesothelioma was associated with an increased number of pericardiocentesis procedures before pericardiectomy and with the presence of macrophages in the superficial pericardial layer, edema, fibrin, and hemorrhage. Disease-free interval and overall survival were significantly shorter in patients with mesothelioma compared with IP.