Analysis of ryanodine receptor (RyR) and phosphorylated ryanodine receptor (p-RyR) levels in SR and AF pigs.

<p><b>a</b> Total RyR protein did not differ between animal groups. <b>b, c</b> PKA-phosphorylated RyR at Ser2808 was reduced, while CaMKII-phosphorylated RyR at Ser2814 was not affected by AF. <b>d</b> Relative p-RyR_Ser2808 but not p-RyR_Ser2814 content was diminished in atrial tissue obtained from n = 5 animals per group. Original Western blots and mean normalized optical density data are provided (*<i>P</i> < 0.05).</p

Expression of L-type Ca²⁺ channels (LTCC) and Na+-Ca²⁺ exchanger (NCX) 1 in AF animals and in SR controls.

<p><b>a, b</b> Regulatory LTCC α₂ subunit was significantly downregulated in AF animals, whereas the pore forming α_1c subunit was not affected. <b>c</b> AF lead to significant upregulation of the NCX1 transporter. Representative Western blots and mean (± SEM) optical density data normalized to GAPDH are displayed (n = 5 animals per group). *<i>P</i> < 0.05; ***<i>P</i> < 0.001.</p

AF-induced remodeling of Ca²⁺-calmodulin-dependent protein kinase II (CaMKII) δ and protein kinase A (PKA).

<p>Representative Western blots and mean optical density values normalized to glyceraldehyde 3-phosphate dehydrogenase (GAPDH) are displayed relative to sinus rhythm (SR) controls. <b>a,</b> Absolute expression levels of the reference protein, GAPDH, were note affected by AF. <b>b, c</b> Normalized protein expression of total CaMKIIδ and phosphorylated CaMKIIδ (Thr286) in AF animals compared to SR. <b>d</b> Relative CaMKIIδ autophosphorylation at Thr286 was not different between animal groups. <b>e, f</b> Protein levels of catalytic PKA Cα/β subunits (PKA_C) and of phosphorylated regulatory RIIα subunits (PKA_RII) in AF and SR animals. Mean values obtained from five animals per group are provided ± SEM; *<i>P</i> < 0.05.</p

Remodeling of Ca²⁺ handling proteins during atrial fibrillation and heart failure.

<p>Changes in protein expression are indicated by arrows (orange color). Solid black arrows indicate transport directions of Ca²⁺ or Na⁺ ions, respectively. Decreased levels of Ca²⁺-calmodulin-dependent protein kinase (CaMK) IIδ and protein kinase A (PKA) causes hypophosphorylation of phospholamban (PLN) and ryanodine receptor (RyR) 2, leading to reduced Ca²⁺ uptake into the sarcoplasmic reticulum through sarcoplasmic reticulum Ca²⁺-ATPase (Serca) 2a. Increased intracellular Ca²⁺ levels and upregulation of Na⁺-Ca²⁺ exchanger (NCX) 1 expression enhance electrogenic Na⁺-Ca²⁺ exchange. This mechanism is attenuated by reduced L-type calcium channel (LTCC) expression that limits systolic Ca²⁺ influx.</p

Alterations of sarcoplasmic reticulum Ca²⁺-ATPase (Serca) 2a and its regulator phospholamban (PLN) during AF.

<p>Total PLN (<b>a</b>) and PLN phosphorylated by CaMKII (Thr17; <b>b</b>) or PKA (Ser16; <b>c</b>) was downregulated in AF animals. <b>d</b> Phosphorylation levels relative to total PLN. <b>e</b> Serca2a protein analysis revealed a trend towards reduced protein expression associated with AF. Mean ± SEM optical density data normalized to GAPDH obtained from n = 5 Western blots per group are displayed. *<i>P</i> < 0.05; **<i>P</i> < 0.01.</p

Clinical findings in AF pigs subjected to atrial tachypacing.

<p><b>a</b> Representative ECG recordings at baseline and after atrial fibrillation (AF) induction by atrial burst pacing show sinus rhythm on day 0 and AF on day 7. <b>b</b> Mean heart rates assessed by daily ECG measurements from AF animals (n = 5). <b>c-f</b> Atrial effective refractory periods (AERP; <b>c</b>, <b>d</b>) and corrected sinus node recovery time (SNRT; <b>e</b>, <b>f</b>) at baseline and prior to euthanization at day 7 in AF pigs (n = 5). <b>g, h</b> Echocardiographic analysis of left ventricular ejection fraction (EF) and left atrial (LA) diameter. Data are given as mean ± SEM; *<i>P</i> < 0.05; **<i>P</i> < 0.01.</p

Odds ratios for variables of the model for classification between pAF and SR.

<p>(A) Odds ratios for the reduced logistic model with 12 variables ordered according to their magnitude. Odds ratios reflect the effects of binary variable changes, indicated by a ‘+’, or continuous variable changes by the indicated unit intervals, on the risk for the presence of pAF (error bars: 95% confidence intervals, shaded bars: echocardiographic variables). The most predictive variables can be recognized by small confidence intervals. (B) Odds ratios for the simplified logistic model that was reduced to the most predictive 4 variables as in panel A.</p

Reliable classification is possible between pAF and SR, and between cAF and SR.

<p>ROC curves are plotted for logistic models reduced to the most predictive variables for classification between pAF, cAF and SR groups after 100-fold cross-validation (areas: 95% confidence intervals). AUCs indicate reliable classification between pAF and SR (AUC = 0.80), and between cAF and SR (AUC = 0.93).</p

A Simple, Non-Invasive Score to Predict Paroxysmal Atrial Fibrillation

<div><p>Paroxysmal atrial fibrillation (pAF) is a major risk factor for stroke but remains often unobserved. To predict the presence of pAF, we developed model scores based on echocardiographic and other clinical parameters from routine cardiac assessment. The scores can be easily implemented to clinical practice and might improve the early detection of pAF. In total, 47 echocardiographic and other clinical parameters were collected from 1000 patients with sinus rhythm (SR; n = 728), pAF (n = 161) and cAF (n = 111). We developed logistic models for classifying between pAF and SR that were reduced to the most predictive parameters. To facilitate clinical implementation, linear scores were derived. To study the pathophysiological progression to cAF, we analogously developed models for cAF prediction. For classification between pAF and SR, amongst 12 selected model parameters, the most predictive variables were tissue Doppler imaging velocity during atrial contraction (TDI, A’), left atrial diameter, age and aortic root diameter. Models for classifying between pAF and SR or between cAF and SR showed areas under the ROC curves of 0.80 or 0.93, which resembles classifiers with high discriminative power. The novel risk scores were suitable to predict the presence of pAF based on variables readily available from routine cardiac assessment. Modelling helped to quantitatively characterize the pathophysiologic transition from SR via pAF to cAF. Applying the scores may improve the early detection of pAF and might be used as decision aid for initiating preventive interventions to reduce AF-associated complications.</p></div

Model coefficients and odds ratios for reduced logistic models.

<p>Model coefficients and odds ratios for reduced logistic models.</p