QT instability, an indicator of augmented arrhythmogenesis, increases with the progression of myxomatous mitral valve disease in dogs.

OBJECTIVES: To investigate QT instability in dogs with myxomatous mitral valve disease (MMVD) and to determine if this is associated with arrhythmogenesis. ANIMALS: One hundred sixty-seven MMVD dogs that met the study criteria were included. METHODS: Echocardiographic and electrocardiographic data were gathered. Fifty consecutive QT intervals were recorded for each dog. Both heart rate-corrected and uncorrected QT intervals were used to calculate average QT (QTa), QT variance (QTv), total instability (TI), short-term instability (STI), and long-term instability (LTI). Sensitivity and specificity of QTa, QTv, TI, STI, and LTI in identifying arrhythmias and cardiac remodeling were calculated. Patient follow-ups were obtained for analyses of disease progression and survival. RESULTS: An increase related to progression was documented for all the studied indices. QTa and STI best identified dilated hearts and arrhythmias, respectively. Dogs with QTa >272 ms and STI >8 ms were 15% more likely to develop ventricular arrhythmias (likelihood ratios of 2.31 [P = 0.0008] and 2.09 [P = 0.0049], respectively). A QTa >258 ms discriminated American College of Veterinary Internal Medicine stage B1 from stages B2/C disease with a sensitivity of 63% and specificity of 61%. Dogs in American College of Veterinary Internal Medicine stage C of MMVD have higher STI and 3.34 times increased risk of developing arrhythmias when values more than 8 ms are reached. All indices except LTI and QTv showed prognostic value, with increases relating to all-cause mortality. CONCLUSION: Analyses of QT intervals demonstrated changes in STI, LTI, and TI. Increased QT prolongation and instability are significantly related to mortality and may be useful in determining prognosis of MMVD patients.

Evaluation of echocardiographic variables of morphometry and function in horses submitted to minimally invasive partial pericardiotomy / [Avaliação de variáveis ecocardiográficas morfométricas e funcionais em cavalos submetidos à pericardiotomia parcial minimamente invasiva]

This study aimed to evaluate the impact of minimally invasive partial pericardiotomy on echocardiographic variables of morphometry and function in healthy horses. Minimally invasive pericardiotomy was performed in six healthy horses. Echocardiographic evaluation was executed in different moments: prior to the surgical procedure (M0); 24 hours post procedure (M1); 72 hours post procedure (M2) and 28 days post procedure (M3). The following variables were measured: Right ventricular internal diameter in diastole and systole (RVd and RVs), interventricular septum thickness in diastole and systole (IVSd and IVSs), left ventricular internal diameter in diastole and systole (LVd and LVs), left ventricular free wall thickness in diastole and systole (LVFWd and LVFWs), aortic root diameter (Ao) and left atrial diameter (LA). From this data, the following variables were calculated: fractional shortening (FS%), fractional thickening of the interventricular septum (IVS%), fractional thickening of the left ventricular free wall (LVFW%) and the relationship between left atrial and aortic diameters (LA/Ao). After 28 days, a new thoracoscopy was performed for inspection of the thoracic cavity. In M1 and M2 ECO evaluations, a statistically significant change in LVFW and a decrease in RVd, LVd, LVFWs, LA, LVs, FS% and IVS was documented. Pericardiotomy is a promising technique in horses, with minor postoperative complication. The variations in the echocardiographic parameters were transient and did not cause hemodynamic damage to the animals.(AU)

O objetivo do presente estudo foi avaliar o impacto da pericardiotomia parcial minimamente invasiva sobre as variáveis ecocardiográficas morfométricas e funcionais em cavalos, visto que não há nenhum trabalho que tenha avaliado o impacto da pericardiotomia na espécie equina. Foram utilizados seis cavalos hígidos, nos quais se realizou pericardiotomia minimamente invasiva. Em todos eles, foi efetuado exame ecocardiográfico em diferentes momentos: previamente ao procedimento cirúrgico (M0); 24 horas após (M1); 72 horas após (M2) e 28 dias após (M3). Foram mensurados: diâmetro interno do ventrículo direito (VDd e VDs), espessura do septo interventricular (SIVd e SIVs), diâmetro interno do ventrículo esquerdo (VEd e VEs), espessura da parede livre do ventrículo esquerdo (PLVEd e PLVEs), diâmetro interno da aorta (Ao) e diâmetro atrial esquerdo (AE). Foram calculadas as variáveis fração de encurtamento (FEC%), espessamento fracional do septo interventricular (SIV%), espessamento fracional da parede livre do ventrículo esquerdo (PLVE%) e relação entre diâmetro do átrio esquerdo e diâmetro aórtico (AE/Ao). Após 28 dias, realizou-se nova toracoscopia para inspeção da cavidade torácica. Nas avaliações do ECO no M1 e no M2, houve alteração estatisticamente significativa no PLVE em diástole (28±5,5 e 31,7±2, respectivamente) e diminuição dos parâmetros VDd,(30,1±11,6 e 31,7± 10,7) VEd (113,3±21 e 121,7±13,7), PLVEs (42±8,2 e 43,9±2,8), AE (78,5±6,1 e 82,7±4,7), VEs (74,1±16 e 71,5±9,3), FEC (34,4±10,2 e 41,2±5,7) e SIV (27,1±8,7 e 42,3±27,9). A técnica de pericardiotomia empregada mostrou-se promissora em equinos. As variações dos parâmetros ecocardiográficos foram transitórias, não causando prejuízos hemodinâmicos aos animais.(AU)