Noninvasive assessment of a bioconductive patch for treating atrial fibrillation with magnetic resonance imaging

Electrical and structural remodeling disrupt atrial electrical conduction, leading to atrial fibrillation (AF). Epicardially delivered conductive biomaterial patches can effectively transmit electrical signals and potentially diminish AF. However, given the progressive nature of AF development, continuous and noninvasive monitoring is essential for assessing the therapeutic efficacy of these patches over time. In this study, superparamagnetic iron oxide nanoparticles (SPIO NPs) are synthesized and used to label a bio-conductive patch made of poly-3-amino-4-methoxybenzoic acid (PAMB) conjugated to gelatin (PAMBG-NP). Incorporating SPIO NPs does not alter the mechanical, electrical, or biocompatible properties of PAMBG. PAMBG-NP restores conduction velocity, suppresses rotor generation, and prevents re-entry currents, thereby relieving AF burden in an in vitro pacing model. In vivo, a bell-shaped PAMBG-NP patch is applied to the right and left atria of KCNE1 knockout mice. Compared to its Gelatin-NP counterpart, PAMBG-NP significantly reduces AF duration and enhances post-AF recovery over a 60-day period. Furthermore, magnetic resonance imaging indicates that PAMBG-NP degrades more slowly than Gelatin-NP, along with having a reduced incidence of AF in PAMBG-NP-treated animals. Therefore, incorporating SPIO NPs into PAMBG enables real-time, in vivo monitoring, potentially facilitating the noninvasive evaluation of its therapeutic efficacy.

Age- and sex-based normal reference ranges of the cardiac time intervals: the Copenhagen City Heart Study

BACKGROUND

Color tissue Doppler imaging (TDI) M-mode can be used to measure the cardiac time intervals including the isovolumic contraction time (IVCT), the left ventricular ejection time (LVET), the isovolumic relaxation time (IVRT), and the combination of all the cardiac time intervals in the myocardial performance index (MPI) defined as [(IVCT + IVRT)/LVET]. The aim of this study was to establish normal age- and sex-based reference ranges for the cardiac time intervals.

METHODS AND RESULTS

A total of 1969 participants free of cardiovascular diseases and risk factors from the general population with limited age range underwent an echocardiographic examination including TDI. The median age was 46 years (25th-75th percentile: 33-58 years), and 61.5% were females. In the entire study population, the IVCT was observed to be 40 ± 10 ms [95% prediction interval (PI) 20-59 ms], the LVET 292 ± 23 ms (95% PI 248-336 ms), the IVRT 96 ± 19 ms (95% PI 59-134 ms) and MPI 0.47 ± 0.09 (95% PI 0.29-0.65). All the cardiac time intervals differed significantly between females and males. With increasing age, the IVCT increased in females, but not in males. The LVET did not change with age in both sexes, while the IVRT increased in both sexes with increasing age. Furthermore, we developed regression equations relating the heart rate to the cardiac time intervals and age- and sex-based normal reference ranges corrected for heart rate.

CONCLUSION

In this study, we established normal age- and sex-based reference ranges for the cardiac time intervals. These normal reference ranges differed significantly with sex.

Echocardiographic Parameters Associated With Cardiorespiratory Fitness and Physical Activity in Childhood Acute Lymphoblastic Leukemia Survivors

BACKGROUND

Children's exposure to chemotherapeutic agents causes several long-term adverse effects but physical activity has been evidenced to be an effective strategy to improve cardiac function. This cross-sectional study aimed to explore the association between physical activity levels, cardiorespiratory fitness, and cardiac parameters measured by echocardiography.

METHODS

Participants were 216n childhood acute lymphoblastic leukemia survivors who underwent a maximal cardiopulmonary exercise test and self-reported their daily minutes of moderate to vigorous physical activity. They underwent a complete transthoracic echocardiographic assessment. Systolic and diastolic function analysis and strain images analysis were performed. The associations were studied through the preventive fraction (examined with univariate crude and adjusted logistic regression models) of regular physical activity (≥150 min·wk-1) and adequate cardiorespiratory fitness levels (above the median ≥ 32.0 mL·kg-1·min-1) on cardiac parameters.

RESULTS

Crude analysis shows that regular physical activity was associated with a significant preventive fraction in mitral E/A ratio (56%; P = .013), while adjusted analyses highlighted a nonsignificant reduction of 74% to 37% in the prevalence of cardiac parameters associated with physical activity. Similar associations of adequate cardiorespiratory fitness on cardiac parameters were observed. Adjusted analyses revealed a nonsignificant reduction of 7% to 86% in the prevalence of cardiac parameters associated with cardiorespiratory fitness.

CONCLUSION

This study reports that regular physical activity and adequate cardiorespiratory fitness were associated with a higher preventive fraction. Thus, engaging in physical activity prevents childhood acute lymphoblastic leukemia survivors' cardiac dysfunctions. These findings are novel and clinically relevant in pediatric cardiooncology and provide additional evidence to strengthen the benefits of exercise as long-term care in childhood cancer survivors.

Changes in cardiac time intervals over a decade and the risk of incident heart failure: The Copenhagen City heart study

BACKGROUND

The cardiac time intervals include the isovolumic contraction time (IVCT), the left ventricular ejection time (LVET), the isovolumic relaxation time (IVRT) and the combination of all the cardiac time intervals in the myocardial performance index (MPI) (defined as [(IVCT+IVRT)/LVET)]. Whether the cardiac time intervals change over time and which clinical factors that accelerate these changes is not well-established. Additionally, whether these changes are associated with subsequent heart failure (HF), remains unknown.

METHODS

We investigated participants from the general population (n = 1064) who had an echocardiographic examination including color tissue Doppler imaging performed in both the 4th and 5th Copenhagen City Heart Study. The examinations were performed 10.5 years apart.

RESULTS

The IVCT, LVET, IVRT and MPI increased significantly over time. None of the investigated clinical factors were associated with increase in IVCT. Systolic blood pressure (standardized β= - 0.09) and male sex (standardized β= - 0.08) were associated with an accelerated decrease in LVET. Age (standardized β=0.26), male sex (standardized β=0.06), diastolic blood pressure (standardized β=0.08), and smoking (standardized β=0.08) were associated with an increase in IVRT, while HbA1c (standardized β= - 0.06) was associated with a decrease in IVRT. Increasing IVRT over a decade was associated with an increased risk of subsequent HF in participants aged <65 years (per 10 ms increase: HR 1.33; 95%CI (1.02-1.72), p = 0.034).

CONCLUSION

The cardiac time increased significantly over time. Several clinical factors accelerated these changes. An increase in IVRT was associated with an increased risk of subsequent HF in participants aged <65 years.