No abstract

BackgroundEarly recognition of left‐sided congestive heart failure (CHF) in dogs with degenerative mitral valve disease (DMVD) is important because it influences medical therapy, timing of follow‐up, and outcome.HypothesisPulmonary vein diameter‐to‐pulmonary artery diameter ratio (PV/PA) measured by echocardiography can predict CHF.AnimalsNinety‐eight client‐owned dogs, 37 controls, and 61 dogs with DMVD.MethodsProspective clinical cohort study. History, physical examination and Doppler‐echocardiography were performed. Dogs were classified as International Small Animal Cardiac Health Council class I, II or III. Congestive heart failure was identified in a subset of 56 dogs based on radiographic findings. The PV/PA was measured in bidimensional (2D) and M‐mode by 2 investigators blinded to the radiologists’ conclusions.ResultsInterobserver coefficients of variation for PV/PA acquisition and measurement were <10%. The PV/PA in control dogs was approximately 1 and increased with class of heart failure. The presence of CHF could be best predicted by measuring PV/PA in 2D echocardiography (cut‐off, 1.7; area under the curve, 0.98; CI, 0.97–0.98; P < .001) with a sensitivity of 96% and a specificity of 91%.Conclusion and clinical importanceThe PV/PA is a simple and reproducible echocardiographic variable that increases with class of heart failure and may help discriminate dogs in CHF from asymptomatic dogs with DMVD. Additional studies are required to determine whether PV/PA might provide additional information in the integrated interpretation of Doppler‐echocardiographic indices of left ventricular filling pressures and could be used for rapid assessment of CHF in dogs in a critical care setting.

Entee. Respiratory-related heart rate variability in progressive experimental heart failure. Am J Physiol Heart Circ Physiol 289: H1729 -H1735, 2005. First published May 27, 2005; doi:10.1152/ajpheart.01129.2004.-Heart failure is associated with autonomic imbalance, and this can be evaluated by a spectral analysis of heart rate variability. However, the time course of low-frequency (LF) and high-frequency (HF) heart rate variability changes, and their functional correlates during progression of the disease are not exactly known. Progressive heart failure was induced in 16 beagle dogs over a 7-wk period by rapid ventricular pacing. Spectral analysis of heart rate variability and respiration, echocardiography, hemodynamic measurements, plasma atrial natriuretic factor, and norepinephrine was obtained at baseline and every week, 30 min after pacing interruption. Progressive heart failure increased heart rate (from 91 Ϯ 4 to 136 Ϯ 5 beats/min; P Ͻ 0.001) and decreased absolute and normalized (percentage of total power) HF variability from week 1 and 2, respectively (P Ͻ 0.01). Absolute LF variability did not change during the study until it disappeared in two dogs at week 7 (P Ͻ 0.05). Normalized LF variability increased in moderate heart failure (P Ͻ 0.01), leading to an increased LF-to-HF ratio (P Ͻ 0.05), but decreased in severe heart failure (P Ͻ 0.044; week 7 vs. week 5). Stepwise regression analysis revealed that among heart rate variables, absolute HF variability was closely associated with wedge pressure, right atrial and pulmonary arterial pressure, left ventricular ejection fraction and volume, ratio of maximal velocity of early (E) and atrial (A) mitral flow waves, left atrial diameter, plasma norepinephrine, and atrial natriuretic peptide (0.45 Ͻ r Ͻ 0.65, all P Ͻ 0.001). In tachycardia-induced heart failure, absolute HF heart rate variability is a more reliable indicator of cardiac dysfunction and neurohumoral activation than LF heart rate variability. autonomic nervous system; tachycardiomyopathy HEART FAILURE is associated with an autonomic imbalance consisting of an increase in sympathetic drive (25) and a reduction of parasympathetic activity (5). In these patients, efferent sympathetic nerve traffic has been shown to be increased in proportion to functional impairment (16), norepinephrine plasma levels are associated with an increased risk of death (7), and ␤-blocker therapy improves survival (8). Thus autonomic imbalance with prominent sympathetic activation plays an important role in heart failure pathophysiology.Cardiac autonomic imbalance can be evaluated by the spectral analysis of R-R interval (RRI) variability (35). In normal humans and in dogs, RRI variability occurs predominantly at low frequency (LF, between 0.04 and 0.15 Hz) and at high frequency (HF, between 0.15 and 1.0 Hz) (29). LF oscillations are present in both sympathetic and vagal outflows (24, 30). However, within physiological conditions, sympathetic activation is associated with an increase in LF when expressed in normalized u...

No abstract