A temporal window of vulnerability for development of atrial fibrillation with advancing heart failure.

AIMS: Heart failure (HF) is associated with development of AF and life-threatening ventricular tachycardia and fibrillation (VT/VF). Vulnerability to development of AF and VT/VF at different stages of HF and the underlying pathophysiological mechanisms are poorly defined. The present study was designed to determine the time-course of development of electrical and structural remodelling of the atria and ventricles, and their contribution to induction of AF and VT/VF in a canine model of HF. METHODS AND RESULTS: Dogs were ventricular tachypaced (VTP) for 2-3 weeks or 5-6 weeks ('early' and 'late' HF, respectively). Electrophysiological studies were performed in isolated atrial and ventricular preparations and correlated with cardiac dimensions and haemodynamic parameters recorded in vivo. Vulnerability to programmed electrical stimulation-induced AF was greater in early vs. late stages of HF (78% vs. 38%). In contrast, VT/VF was inducible in late but not in early stages of HF (38% vs. 0%). The temporal distinction in atrial and ventricular arrhythmia susceptibility was associated with a much more rapid development of electrical and structural remodelling in atria. Vulnerability to AF developed following moderate electro-structural remodelling and waned with further progression to severe remodelling, which averted rapid atrial activation. CONCLUSIONS: A temporal window of vulnerability for AF appears relatively early during development of VTP-induced HF in dogs, whereas VT/VF vulnerability is observed at more advanced stages of HF. These findings, if confirmed in humans, may have clinical implications with regard to prognosis and approach to therapy of patients with HF.

Multicenter evaluation of plasma N-terminal probrain natriuretic peptide (NT-pro BNP) as a biochemical screening test for asymptomatic (occult) cardiomyopathy in cats.

BACKGROUND: B-type natriuretic peptide concentrations reliably distinguish between cardiac and respiratory causes of dyspnea, but its utility to detect asymptomatic cats with occult cardiomyopathy (OCM) is unresolved. HYPOTHESIS/OBJECTIVES: Determine whether plasma N terminal probrain natriuretic peptide (NT-proBNP) concentration can discriminate asymptomatic cats with OCM from normal cats, and whether NT-proBNP concentration correlates with clinical, biochemical, and echocardiographic parameters. ANIMALS: One hundred and fourteen normal, healthy cats; 113 OCM cats. METHODS: Prospective, multicenter, case-controlled study. NT-proBNP was prospectively measured and cardiac status was determined from history, physical examination, and M-mode/2D/Doppler echocardiography. Optimal cut-off values were derived using receiver operating characteristic (ROC) curve analysis. RESULTS: NT-proBNP was higher (median, interquartile range [25th and 75th percentiles]) in (1) OCM (186 pmol/L; 79, 478 pmol/L) versus normal (24 pmol/L; 24, 32 pmol/L) (P < .001); and (2) hypertrophic obstructive cardiomyopathy (396 pmol/L; 205, 685 pmol/L) versus hypertrophic cardiomyopathy (112 pmol/L; 48, 318 pmol/L) (P < .001). In OCM, NT-proBNP correlated (1) positively with LVPWd (ρ = 0.23; P = .01), LA/Ao ratio (ρ = 0.31; P < .001), LVs (ρ = 0.33; P < .001), and troponin-I (ρ = 0.64; P < .001), and (2) negatively with %FS (ρ = -0.27; P = .004). Area under ROC curve was 0.92; >46 pmol/L cut-off distinguished normal from OCM (91.2% specificity, 85.8% sensitivity); >99 pmol/L cut-off was 100% specific, 70.8% sensitive. CONCLUSIONS AND CLINICAL IMPORTANCE: Plasma NT-proBNP concentration reliably discriminated normal from OCM cats, and was associated with several echocardiographic markers of disease severity. Further studies are needed to assess test performance in unselected, general feline populations, and evaluate relationships between NT-proBNP concentrations and disease progression.

Use of transesophageal echocardiography for visualization of the patent ductus arteriosus during transcatheter coil embolization.

Transesophageal echocardiography (TEE) enhances our ability to see the patent ductus arteriosus in the dog. The improved visualization may potentially improve our ability to perform transcatheter coil embolization in patients that are more likely to have a successful outcome. This report uses still and video images to detail the specifics of coil embolization as performed with the assistance of TEE and compares the images with those of angiography, surgery and postmortem examination.