Correlation of potential noninvasive biomarkers of extracellular matrix remodeling with postoperative heart failure - a preliminary study

Background: Postoperative heart failure (PHF) is a major factor that prolongs hospital stay and contributes to increased cost and morbidity after surgery. Clinical predictors of PHF have been identified but lack specificity and predictive accuracy; therefore, identifying the candidates at risk for PHF remains difficult, thus, necessitating further investigation. Since cardiac fibrosis in the elderly contributes to abnormal cardiac contractility, elevated markers of extracellular matrix turnover can be used to identify those at risk for PHF. Purpose: To identify biomarkers in those at risk for PHF. Methods: Serum biomarkers of collagen synthesis (C-terminal propeptide type 1 of procollagen [PICP] and N-terminal propeptide of type III procollagen [PIIINP]), collagen degradation (C-terminal telopeptide of collagen type 1 [CITP]), and extracellular matrix remodeling (matrix metalloprotease-1 [MMP-1] and tissue inhibitor of metalloproteases-1 [TIMP-1]) were determined by ELISA in preoperative blood samples collected from patients with no prior history of heart failure who were undergoing cardiac surgery and correlated to PHF. Results: Of 45 patients enrolled (mean age 69 ± 11 years, 77% male), 11 (24%, mean age 66 ± 10 years) developed PHF requiring additional inotropic support (dobutamine) and management for heart failure. Overall, there were no significant differences in baseline demographics and comorbidities between those who did or did not develop PHF. Ventricular function was preserved, with no significant differences in left ventricular ejection fraction (60 ± 11% vs. 50 ± 16%; P=0.11) or atrial and ventricular dimensions and function between the two groups. Mean PICP levels showed elevated trend in PHF (661 ± 375 ng/ ml vs. 609 ± 410 ng/ml in the non-PHF group; P=0.07); however, PIIINP levels were not significantly different between the two groups (134 ± 72 in PHF vs. 157 ± 73; P=0.47). However, levels of CITP were significantly lower in PHF patients (6 ± 3 ng/ml vs. 9 ± 7 ng/ml; P=0.03). The overall ratio of PICP/CITP was higher in patients with PHF (119 vs. 108; P=0.7). The MMP-1, MMP-2 and TIMP-1 levels were not significantly different between the two groups. Conclusion: The preliminary data obtained from 45 patients demonstrated a trend toward higher PICP levels indicative of collagen synthesis in those at risk for PHF but was not statistically significant. This is likely due to the small sample size and the heterogeneity of the patients, indicating a larger number of heterogeneous patients are needed to demonstrate the prognostic significance of serum biomarkers of extracellular matrix remodeling

A novel high throughput approach for quantification of cell density

Background: Current approach to cell counting using hemacytometer is limited by requirement for high cell concentration and is prone to error. In biological experiments using cells from human cardiac tissues with limited number of cells, this approach results in large variation in cell counts. Here, we demonstrate the utility of a novel approach using a 96-well microplate that accurately provides the density of cells as low as 15,000 cells/cm2, which fulfills an unmet need in experiments with limited cell availability. Purpose: To develop and test the accuracy of a high-throughput 96-well microplate assay in assessing the cell density in comparison to existing methods. Methods: NIH/3T3 fibroblasts were cultured and differentiated and grown to different cell density. Cell number obtained using hemacytometer was compared to the total fluorescence of propidium iodide, binding to the nuclei of cells permeabilized with Triton X-100 (0.25%), and assessed using multiplate reader. In addition, the total activity of lactate dehydrogenase, an intracellular enzyme, was used to assess the total volume of cytoplasm released from permeabilized cells. Furthermore, the ratio of live/ dead cells was determined by propidium iodide-positive cells and lactate dehydrogenase activity before and after permeabilization in each well of the 96-well plate. Results:There was a linear relationship between increasing intensity of propidium iodide fluorescence with the density of the cells in the 96-well microplate (ranging from 5,000 to 100,000 cells/cm2). Similarly, linear relationship was observed between the intensity of propidium iodide fluorescence and cellular lactate dehydrogenase activity in corresponding wells. At low cell density ( Conclusion: Proposed propidium iodide and lactate dehydrogenase assays are useful tools for quantification of cell number in high-throughput manner with greater accuracy at low cell density, higher reproducibility and overall time saving. This assay is especially useful in experiments using limited cell number such as cells isolated from the human heart

Frequent periodic leg movement during sleep is associated with left ventricular hypertrophy and adverse cardiovascular outcomes

BACKGROUND: Sleep disturbance caused by obstructive sleep apnea is recognized as a contributing factor to adverse cardiovascular outcomes. However, the effect of restless legs syndrome, another common cause of fragmented sleep, on cardiac structure, function, and long-term outcomes is not known. The aim of this study was to assess the effect of frequent leg movement during sleep on cardiac structure and outcomes in patients with restless legs syndrome. METHODS: In our retrospective study, patients with restless legs syndrome referred for polysomnography were divided into those with frequent (periodic movement index \u3e 35/hour) and infrequent (≤ 35/hour) leg movement during sleep. Long-term outcomes were determined using Kaplan-Meier and logistic regression models. RESULTS: Of 584 patients, 47% had a periodic movement index \u3e 35/hour. Despite similarly preserved left ventricular ejection fraction, the group with periodic movement index \u3e 35/hour had significantly higher left ventricular mass and mass index, reflective of left ventricular hypertrophy (LVH). There were no significant baseline differences in the proportion of patients with hypertension, diabetes, hyperlipidemia, prior myocardial infarction, stroke or heart failure, or the use of antihypertensive medications between the groups. Patients with frequent periodic movement index were older, predominantly male, and had more prevalent coronary artery disease and atrial fibrillation. However, on multivariate analysis, periodic movement index \u3e 35/hour remained the strongest predictor of LVH (odds ratio, 2.45; 95% confidence interval, 1.67-3.59; P \u3c .001). Advanced age, female sex, and apnea-hypopnea index were other predictors of LVH. Patients with periodic movement index \u3e 35/hour had significantly higher rates of heart failure and mortality over median 33-month follow-up. CONCLUSIONS: Frequent periodic leg movement during sleep is an independent predictor of severe LVH and is associated with increased cardiovascular morbidity and mortality

Circulating biomarkers predictive of postoperative atrial fibrillation

Postoperative atrial fibrillation (PoAF), a common complication of cardiac surgery, contributes significantly to morbidity, mortality, and increasing health care costs. Despite advances in surgical and medical management, the overall incidence of PoAF has not changed significantly, partly due to the limited understanding of mechanisms underlying acute surgery-related factors, such as myocardial injury, inflammation, sympathetic activation, and oxidative stress, which play an important role in the initiation of PoAF, while a preexisting atrial substrate appears to be more important in the maintenance of this dysrhythmia. Thus, in a majority of patients, PoAF becomes a manifestation of an underlying arrhythmogenic substrate that is unmasked following acute surgical stress. As such, the ability to identify which patients have this proarrhythmic substrate and are, therefore, at high risk for developing AF postoperatively, is important for the improved selection for prophylactic interventions, closer monitoring for complications, and establishing the probability of AF in the long term. This review highlights the role of the underlying substrate in promoting PoAF, proposed mechanisms, and the potential role of serum biomarkers to identify patients at risk for PoAF

Frequent periodic leg movement during sleep is an unrecognized risk factor for progression of atrial fibrillation.

Sleep apnea has been recognized as a factor predisposing to atrial fibrillation recurrence and progression. The effect of other sleep-disturbing conditions on atrial fibrillation progression is not known. We sought to determine whether frequent periodic leg movement during sleep is a risk factor for progression of atrial fibrillation. In this retrospective study, patients with atrial fibrillation and a clinical suspicion of restless legs syndrome who were referred for polysomnography were divided into two groups based on severity of periodic leg movement during sleep: frequent (periodic movement index >35/h) and infrequent (≤35/h). Progression of atrial fibrillation to persistent or permanent forms between the two groups was compared using Wilcoxon rank-sum test, chi-square tests and logistic regression analysis. Of 373 patients with atrial fibrillation (77% paroxysmal, 23% persistent), 108 (29%) progressed to persistent or permanent atrial fibrillation during follow-up (median, 33 months; interquartile range, 16-50). Compared to patients with infrequent periodic leg movement during sleep (n=168), patients with frequent periodic leg movement during sleep (n=205) had a higher rate of atrial fibrillation progression (23% vs. 34%; p=0.01). Patients with frequent periodic leg movement during sleep were older and predominantly male; however, there were no significant differences at baseline in clinical factors that promote atrial fibrillation progression between both groups. On multivariate analysis, independent predictors of atrial fibrillation progression were persistent atrial fibrillation at baseline, female gender, hypertension and frequent periodic leg movement during sleep. In patients with frequent periodic leg movement during sleep, dopaminergic therapy for control of leg movements in patients with restless legs syndrome reduced risk of atrial fibrillation progression. Frequent leg movement during sleep in patients with restless legs syndrome is associated with progression of atrial fibrillation to persistent and permanent forms