Yonathan F. Melman

Mutation in the S3 segment of KCNQ1 results in familial lone atrial fibrillation.

BACKGROUND Mutations in several ion channel genes have been reported to cause rare cases of familial atrial fibrillation (AF). OBJECTIVE The purpose of this study was to determine the genetic basis for AF in a family with autosomal dominant AF. METHODS Family members were evaluated by 12-lead ECG, echocardiogram, signal-averaged P-wave analysis, and laboratory studies. Fourteen family members in AF-324 were studied. Six individuals had AF, with a mean age at onset of 32 years (range 16-59 years). RESULTS Compared with unaffected family members, those with AF had a longer mean QRS duration (100 vs 86 ms, P = .015) but no difference in the corrected QT interval (423 +/- 15 ms vs 421 +/- 21 ms). The known loci for AF and other cardiovascular diseases were evaluated. Evidence of linkage was obtained with marker D11S4088 located within KCNQ1, and a highly conserved serine in the third transmembrane region was found to be mutated to a proline (S209P). Compared to the wild-type channel, the S209P mutant activates more rapidly, deactivates more slowly, and has a hyperpolarizing shift in the voltage activation curve. A fraction of the mutant channels are constitutively open at all voltages, resulting in a net increase in I(Ks) current. CONCLUSION We identified a family with lone AF due to a mutation in the highly conserved S3 domain of KCNQ1, a region of the channel not previously implicated in the pathogenesis of AF.

Circulating MicroRNA-30d Is Associated With Response to Cardiac Resynchronization Therapy in Heart Failure and Regulates Cardiomyocyte Apoptosis A Translational Pilot Study

Background— Biomarkers that predict response to cardiac resynchronization therapy (CRT) in heart failure patients with dyssynchrony (HFDYS) would be clinically important. Circulating extracellular microRNAs (miRNAs) have emerged as novel biomarkers that may also play important functional roles, but their relevance as markers for CRT response has not been examined. Methods and Results— Comprehensive miRNA polymerase chain reaction arrays were used to assess baseline levels of 766 plasma miRNAs in patients undergoing clinically indicated CRT in an initial discovery set (n=12) with and without subsequent echocardiographic improvement at 6 months after CRT. Validation of candidate miRNAs in 61 additional patients confirmed that baseline plasma miR-30d was associated with CRT response (defined as an increase in left ventricular ejection fraction ≥10%). MiR-30d was enriched in coronary sinus blood and increased in late-contracting myocardium in a canine model of HFDYS, indicating cardiac origin with maximal expression in areas of high mechanical stress. We examined the functional effects of miR-30d in cultured cardiomyocytes and determined that miR-30d is expressed in cardiomyocytes and released in vesicles in response to mechanical stress. Overexpression of miR-30d in cultured cardiomyocytes led to cardiomyocyte growth and protected against apoptosis by targeting the mitogen-associated kinase 4, a downstream effector of tumor necrosis factor. In HFDYS patients, miR-30d plasma levels inversely correlated with high-sensitivity troponin T, a marker of myocardial necrosis. Conclusions— Baseline plasma miR-30d level is associated with response to CRT in HFDYS in this translational pilot study. MiR-30d increase in cardiomyocytes correlates with areas of increased wall stress in HFDYS and is protective against deleterious tumor necrosis factor signaling.

MicroRNAs in Heart Failure Is the Picture Becoming Less miRky

With 550 000 new cases diagnosed annually and

Functional Interactions between KCNE1 C-Terminus and the KCNQ1 Channel

37 billion spent per year,1 heart failure (HF) with reduced ejection fraction is one of the largest contributors to disease burden and healthcare expenditure in the United States. Despite significant progress in the treatment of HF2,3 with medications, the prognosis of HF remains dismal, with a mortality rate of 42% at 5 years after diagnosis. Therefore, understanding the underlying molecular pathways in the transition from established cardiovascular disease to HF may spur the development of novel biomarkers and therapeutic targets. The heart responds to stressors such as hypoxia (in myocardial infarction [MI]), increased wall stress (in valvular heart disease), and neurohormonal/metabolic stress (in diabetes mellitus and hypertension) by cardiomyocyte hypertrophy and fibrosis. Although initially compensatory for increased wall stress or myocyte loss, the molecular pathways that underlie pathological hypertrophy are ultimately maladaptive, recapitulating further hypertrophy, contractile dysfunction, apoptosis, and fibrosis. The progression to HF is associated with a characteristic cascade of altered intracellular signaling and gene expression, representing a final common pathway to ultimate decompensation. The various signaling pathways that underlie pathological hypertrophy and the progression to HF have been the subject of intense investigation and are summarized in multiple review publications.4–9. More recently, considerable attention has been paid to microRNAs (miRNAs), a novel biological control mechanism with the ability to regulate entire molecular networks by complex feedback and feed-forward mechanisms. Several reviews have summarized recent findings implicating miRNAs in cardiac development and disease.10,11 In the past few years, the discovery of circulating miRNAs has led to their investigation as biomarkers and mediators of cell–cell communication. This review focuses on recent developments detailing the role of miRNAs in the pathogenesis of HF, their potential role as biomarkers, and their use as …

Isolation, Culture, and Functional Characterization of Adult Mouse Cardiomyoctyes

The KCNE1 gene product (minK protein) associates with the cardiac KvLQT1 potassium channel (encoded by KCNQ1) to create the cardiac slowly activating delayed rectifier, IKs. Mutations throughout both genes are linked to the hereditary cardiac arrhythmias in the Long QT Syndrome (LQTS). KCNE1 exerts its specific regulation of KCNQ1 activation via interactions between membrane-spanning segments of the two proteins. Less detailed attention has been focused on the role of the KCNE1 C-terminus in regulating channel behavior. We analyzed the effects of an LQT5 point mutation (D76N) and the truncation of the entire C-terminus (Δ70) on channel regulation, assembly and interaction. Both mutations significantly shifted voltage dependence of activation in the depolarizing direction and decreased IKs current density. They also accelerated rates of channel deactivation but notably, did not affect activation kinetics. Truncation of the C-terminus reduced the apparent affinity of KCNE1 for KCNQ1, resulting in impaired channel formation and presentation of KCNQ1/KCNE1 complexes to the surface. Complete saturation of KCNQ1 channels with KCNE1-Δ70 could be achieved by relative over-expression of the KCNE subunit. Rate-dependent facilitation of K+ conductance, a key property of IKs that enables action potential shortening at higher heart rates, was defective for both KCNE1 C-terminal mutations, and may contribute to the clinical phenotype of arrhythmias triggered by heart rate elevations during exercise in LQTS mutations. These results support several roles for KCNE1 C-terminus interaction with KCNQ1: regulation of channel assembly, open-state destabilization, and kinetics of channel deactivation.

Intracardiac echocardiography and fluoroscopy guided percutaneous left ventricular pseudoaneurysm closure

The use of primary cardiomyocytes (CMs) in culture has provided a powerful complement to murine models of heart disease in advancing our understanding of heart disease. In particular, the ability to study ion homeostasis, ion channel function, cellular excitability and excitation-contraction coupling and their alterations in diseased conditions and by disease-causing mutations have led to significant insights into cardiac diseases. Furthermore, the lack of an adequate immortalized cell line to mimic adult CMs, and the limitations of neonatal CMs (which lack many of the structural and functional biomechanics characteristic of adult CMs) in culture have hampered our understanding of the complex interplay between signaling pathways, ion channels and contractile properties in the adult heart strengthening the importance of studying adult isolated cardiomyocytes. Here, we present methods for the isolation, culture, manipulation of gene expression by adenoviral-expressed proteins, and subsequent functional analysis of cardiomyocytes from the adult mouse. The use of these techniques will help to develop mechanistic insight into signaling pathways that regulate cellular excitability, Ca(2+) dynamics and contractility and provide a much more physiologically relevant characterization of cardiovascular disease.

Visualization of the left atrial appendage from the coronary sinus by intracardiac echocardiography.

Left ventricular (LV) pseudoaneurysm is a rare complication after myocardial infarction and cardiac surgery. Standard treatment remains surgical correction; however, percutaneous closure has been attempted in high risk surgical patients. We report a case of three dimensional echocardiography and cardiac CT defined LV pseudoaneurysm which was closed percutaneously using intracardiac echocardiography (ICE) and fluoroscopy guidance. Appropriate planning and guidance proved essential to the procedure with an excellent outcome. Percutaneous closure of LV pseudoaneurysms is safe and feasible in high risk surgical patients and with appropriate imaging modalities may be an alternative to surgical correction.

Response to Letter Regarding Article, “Circulating MicroRNA-30d Is Associated With Response to Cardiac Resynchronization Therapy in Heart Failure and Regulates Cardiomyocyte Apoptosis: A Translational Pilot Study”

1547-5271/

A 54-year-old woman with a single coronary artery and watershed ischemia treated with nitrates.

-see front matter B 2014 Heart Rhythm Society. All rights reserved. PLSVC to the right superior pulmonary vein. She underwent electrophysiology study and ablation of an atypical right atrial flutter. The pre-procedure cardiac magnetic resonance imaging demonstrated shunt from the PLSVC into the right superior pulmonary vein with a Qp/Qs ratio of 1.5:1 (Figure 1A, white arrow). Electroanatomic mapping confirmed the presence of a PLSVC (Figure 1B). In order to exclude left atrial appendage (LAA) thrombus and to examine the presence of a right to left shunt, we took advantage of the coronary sinus system with its anatomical proximity to the LAA (Figures 1C and 1D). The intracardiac ultrasound catheter was advanced via the coronary sinus into the great cardiac vein (Figures 1C and 1D, yellow star). This

Circulating MicroRNA-30d Is Associated With Response to Cardiac Resynchronization Therapy in Heart Failure and Regulates Cardiomyocyte Apoptosis

We thank Sardu and colleagues for their comments. Our report demonstrates that baseline levels of microRNA-30d (miR-30d) are correlated with response to cardiac resynchronization therapy and that miR-30d was dynamically regulated by mechanical stress.1 Moreover, miR-30d appeared to be an adaptive response and was cardioprotective against tumor necrosis factor-α–mediated apoptosis. Similar to our study, Marfella et al2 noted differential expression of several plasma miRNAs in cardiac resynchronization therapy responders versus nonresponders 1 year after cardiac resynchronization therapy. The lack of significant overlap between the sets of extracellular miRNAs reflects some of the ongoing issues in extracellular RNA research. The first issue is differences in patient populations and small sample sizes. The second is variances in methodology. Several groups, including …