Human induced pluripotent stem cells (hiPSCs) offer a unique opportunity for disease modeling. However, it is not invariably successful to recapitulate the disease phenotype because of the immaturity ...of hiPSC-derived cardiomyocytes (hiPSC-CMs). The purpose of this study was to establish and analyze iPSC-based model of catecholaminergic polymorphic ventricular tachycardia (CPVT), which is characterized by adrenergically mediated lethal arrhythmias, more precisely using electrical pacing that could promote the development of new pharmacotherapies.
We generated hiPSCs from a 37-year-old CPVT patient and differentiated them into cardiomyocytes. Under spontaneous beating conditions, no significant difference was found in the timing irregularity of spontaneous Ca2+ transients between control- and CPVT-hiPSC-CMs. Using Ca2+ imaging at 1 Hz electrical field stimulation, isoproterenol induced an abnormal diastolic Ca2+ increase more frequently in CPVT- than in control-hiPSC-CMs (control 12% vs. CPVT 43%, p<0.05). Action potential recordings of spontaneous beating hiPSC-CMs revealed no significant difference in the frequency of delayed afterdepolarizations (DADs) between control and CPVT cells. After isoproterenol application with pacing at 1 Hz, 87.5% of CPVT-hiPSC-CMs developed DADs, compared to 30% of control-hiPSC-CMs (p<0.05). Pre-incubation with 10 μM S107, which stabilizes the closed state of the ryanodine receptor 2, significantly decreased the percentage of CPVT-hiPSC-CMs presenting DADs to 25% (p<0.05).
We recapitulated the electrophysiological features of CPVT-derived hiPSC-CMs using electrical pacing. The development of DADs in the presence of isoproterenol was significantly suppressed by S107. Our model provides a promising platform to study disease mechanisms and screen drugs.
Mutations in
(
), which encodes lamin A and C, typically cause age-dependent cardiac phenotypes, including dilated cardiomyopathy, cardiac conduction disturbance, atrial fibrillation, and malignant ...ventricular arrhythmias. Although the type of
mutations have been reported to be associated with susceptibility to malignant ventricular arrhythmias, the gene-based risk stratification for cardiac complications remains unexplored.
The multicenter cohort included 77
mutation carriers from 45 families; cardiac disorders were retrospectively analyzed. The mean age of patients when they underwent genetic testing was 45±17, and they were followed for a median 49 months. Of the 77 carriers, 71 (92%) were phenotypically affected and showed cardiac conduction disturbance (81%), low left ventricular ejection fraction (<50%; 45%), atrial arrhythmias (58%), and malignant ventricular arrhythmias (26%). During the follow-up period, 9 (12%) died, either from end-stage heart failure (n=7) or suddenly (n=2). Genetic analysis showed truncation mutations in 58 patients from 31 families and missense mutations in 19 patients from 14 families. The onset of cardiac disorders indicated that subjects with truncation mutations had an earlier occurrence of cardiac conduction disturbance and low left ventricular ejection fraction, than those with missense mutations. In addition, the truncation mutation was found to be a risk factor for the early onset of cardiac conduction disturbance and the occurrence of atrial arrhythmias and low left ventricular ejection fraction, as estimated using multivariable analyses.
The truncation mutations were associated with manifestation of cardiac phenotypes in
-related cardiomyopathy, suggesting that genetic analysis might be useful for diagnosis and risk stratification.
Background:TheSCN5Agene encodes the α subunit of the cardiac voltage-gated sodium channel, NaV1.5. The missense mutation, D1275N, has been associated with a range of unusual phenotypes associated ...with reduced NaV1.5 function, including cardiac conduction disease and dilated cardiomyopathy. Curiously, the reported biophysical properties ofSCN5A-D1275N channels vary with experimental system.Methods and Results:First, using a human embryonic kidney (HEK) 293 cell-based heterologous expression system, theSCN5A-D1275N channels showed similar maximum sodium conductance but a significantly depolarizing shift of activation gate (+10 mV) compared to wild type. Second, we generated human-induced pluripotent stem cells (hiPSCs) from a 24-year-old female who carried heterozygousSCN5A-D1275N and analyzed the differentiated cardiomyocytes (CMs). AlthoughSCN5Atranscript levels were equivalent between D1275N and control hiPSC-CMs, both the total amount of NaV1.5 and the membrane fractions were reduced approximately half in the D1275N cells, which were rescued by the proteasome inhibitor MG132 treatment. Electrophysiological assays revealed that maximum sodium conductance was reduced to approximately half of that in control hiPSC-CMs in the D1275N cells, and maximum upstroke velocity of action potential was lower in D1275N, which was consistent with the reduced protein level of NaV1.5.Conclusions:This study successfully demonstrated diminished sodium currents resulting from lower NaV1.5 protein levels, which is dependent on proteasomal degradation, using a hiPSC-based model forSCN5A-D1275N-related sodium channelopathy.
Aortic stenosis (AS), a late complication of thoracic radiation therapy for chest lesions, is often coincident with porcelain aorta or hostile thorax. We herein report a 59-year-old man with a ...history of mediastinal Hodgkin lymphoma treated with radiation therapy but later presenting with heart failure caused by severe AS. Severe calcification in the mediastinum and around the ascending aorta made it difficult to perform surgical aortic valve replacement. The patient therefore underwent transcatheter aortic valve implantation (TAVI). It is important to recognize radiation-induced AS early, now that TAVI is a well-established treatment required by increasing numbers of successfully treated cancer patients.
•Tricuspid regurgitation (TR) was seen in 35% of patients with chronic atrial fibrillation (AF).•No difference exists in right atrial parameters before TR develops.•Right ventricular dysfunction was ...related to development of TR among chronic AF patients.
Chronic atrial fibrillation (AF) can cause significant tricuspid regurgitation (TR), which may result from tricuspid annulus and right atrial enlargement. However, the impact of right ventricular (RV) function on TR development remains unclear.
We retrospectively examined 175 consecutive patients with lone chronic AF (duration >1 year) without left ventricular dysfunction. TR severity was graded by the jet area and vena contracta, and moderate or severe TR were defined as significant TR. Patients were classified as significant TR (TR group) or without (NTR group) for comparison of clinical factors and transthoracic echocardiographic (TTE) parameters. To explore factors associated with TR development, we also compared previous TTE parameters among patients in TR group who showed no prior significant TR TR-preTR(−) and those in NTR group NTR-preTR(−).
The mean age was 78 years (61% men). Significant TR was observed in 61 patients (35%). Compared with NTR group, the TR group was older, and had longer AF duration and larger right-sided cardiac parameters on index TTE. At previous TTE, the TR-preTR(−) group showed a larger basal RV dimension index (26.8 vs. 22.4mm/m2), reduced RV free wall longitudinal strain (RVLS-FW) (−18.96 vs. −23.23), and lower tricuspid annular diameter change during a cardiac cycle (8.8% vs. 14.1%) than NTR-preTR(−) group.
Significant TR was observed in 35% of patients with chronic AF. These patients showed enlarged RV, reduced RVLS-FW, and low tricuspid annular diameter changes before significant TR develops. RV dysfunction may be associated with TR development in chronic AF.
Long-QT syndrome (LQTS) is an inherited arrhythmia characterized by prolonged ventricular repolarization and malignant tachyarrhythmias. LQT1, LQT2, and LQT3 are caused by mutations in KCNQ1 (LQT1), ...KCNH2 (LQT2), and SCN5A (LQT3), which account for approximately 90% of genotyped LQTS patients. Most cardiac events in LQT1 patients occur during exercise, whereas patients with LQT3 tend to have arrhythmic events during rest or asleep.
The study aimed to identify a genetic mutation in a Japanese man who presented with sinus node dysfunction and prolonged QT interval on exercise and epinephrine stress tests, as well as to clarify the electrophysiological properties of mutant channels.
LQTS-related genes were screened in this patient. Electrophysiological functional assays were conducted with a heterologous expression system.
We identified a heterozygous missense SCN5A mutation, V2016M, which changes the last amino acid of the cardiac sodium channel. Electrophysiological analyses revealed that the mutant channels exhibited a loss-of-function feature, decreased peak sodium current densities (wild type 175.2 ± 17.6 pA/pF; V2016M 97.2 ± 16.0 pA/pF; P < .01). In addition, the mutant channels showed gain-of-function features: increased late sodium currents by protein kinase A activation (wild type 0.07 ± 0.01%; V2016M 0.17 ± 0.03%; P < .05) and impaired inactivation of sodium channels by protein kinase A or C activation.
We identified an SCN5A mutation in a patient with sinus node dysfunction and epinephrine-induced QT prolongation, which was an atypical phenotype for LQT3. The electrophysiological properties of the mutant channels might be associated with the overlapping clinical features of the patient.
Background
Catheter ablation (CA) for atrial fibrillation (AF) is widely performed. However, the indication for CA in patients with asymptomatic persistent AF is still controversial.
Methods
Among ...259 consecutive patients who were hospitalized for initial CA of AF, a total of 45 patients who had asymptomatic persistent AF were retrospectively analyzed. Quality of life (QOL) before and 1 year after CA was evaluated, and changes in the cardiac function over 5 years after CA were also examined. QOL was assessed using the AF QOL questionnaire (AFQLQ) developed by the Japanese Heart Rhythm Society. In addition, cardiac function was assessed by measuring the plasma B‐type natriuretic peptide (BNP) level, left ventricular ejection fraction (LVEF), left atrial diameter (LAD) with transthoracic echocardiogram, and left atrial (LA) volume with computed tomography (CT).
Results
The AFQLQ significantly improved after CA in terms of “symptom frequency” and “activity limits and mental anxiety.” The plasma BNP level, LVEF, and LAD significantly improved in the first 3 months after the first CA, with no significant changes thereafter (from 149.0 pg/dL 95% confidence intervals {CI}, 114.5‐183.5 pg/dL to 49.8 pg/dL 95% CI, 26.5‐70.1, P < .0001; from 60.8% 95% CI, 58.1%–63.6% to 65.0% 95% CI, 62.6‐67.4, P = .001; and from 41.3 mm 95% CI, 39.7‐42.9 to 36.8 95% CI, 34.5‐39.1 mm, P < .0001, respectively). LA volume revealed LA reverse remodeling after CA.
Conclusion
Improvement in the QOL and cardiac function after CA of asymptomatic persistent AF was revealed. Asymptomatic persistent AF should be appropriately treated by CA.
Before and after catheter ablation (CA) for asymptomatic persistent atrial fibrillation, quality of life (QOL) was assessed using the AF QOL questionnaire (AFQLQ), and cardiac function was assessed by measuring the plasma B‐type natriuretic peptide (BNP) level, left ventricular ejection fraction (LVEF), and left atrial diameter (LAD) with transthoracic echocardiogram and left atrial (LA) volume with computed tomography (CT). Improvement in QOL and cardiac function after CA for asymptomatic persistent AF was revealed.
The management of idiopathic dilated cardiomyopathy (DCM) is well established. However, a subset of patients do not have recovery from or have recurrences of left ventricular (LV) dysfunction despite ...receiving optimal medical therapy. There are limited long-term follow-up data about LV function and the predictive value of iodine-123-metaiodobenzylguanidine (
123
I-MIBG) scintigraphy, especially among the Japanese population. We retrospectively investigated 81 consecutive patients with DCM (mean LV ejection fraction (EF) 28 ± 7.5%) who had undergone
123
I-MIBG scintigraphy before starting β-blockers. According to chronological changes in LVEF, study patients were classified into three subgroups: sustained recovery group, recurrence group, and non-recovery group. The outcome measure was cardiac death. Mean age was 59 ± 11 years and median follow-up was 11.5 (5.8–15.0) years. Thirty-six patients had recovery, 11 had recurrences, and 34 did not have recovery. The sustained recovery group had the best cardiac death-free survival, followed by the recurrence and non-recovery groups. Prolonged time to initial recovery was associated with recurrence of LV dysfunction. Large LV end-diastolic diameter and reduced heart to mediastinum ratio were associated with poor prognosis. In conclusion, with β-blocker therapy, 14% of patients showed recurrences of LV dysfunction. Thus, careful follow-up is needed, keeping in mind the possibility of recurrence, even if LVEF once improved, especially in patients whose time to initial recovery was long.
123
I-MIBG scintigraphy provides clinicians with additional prognostic information.
The changes in cardiac function that occur after pericardiocentesis are unclear. An understanding of the effect of pericardiocentesis on right ventricular (RV) and left ventricular (LV) function is ...clinically important. This study was performed to assess RV and LV function with echocardiography before and after pericardiocentesis. In total, 19 consecutive patients who underwent pericardiocentesis for more than moderate pericardial effusion were prospectively enrolled from August 2015 to October 2017. Comprehensive transthoracic echocardiography was performed before, immediately after (within 3 h), and 1 day after pericardiocentesis to investigate the changes in RV and LV function. The mean age of all patients was 72.6 ± 12.2 years. No pericardiocentesis-related complications occurred during the procedure, but one patient died of right heart failure 8 h after pericardiocentesis. After pericardiocentesis, RV inflow and outflow diameters increased (
p
< 0.05 versus values before pericardiocentesis), and the parameters of RV function (tricuspid annular plane systolic excursion, tricuspid lateral annular systolic velocity, fractional area change, and RV free wall longitudinal strain) significantly decreased (
p
< 0.001 versus values before pericardiocentesis). These abnormal values or RV dysfunction remained 1 day after pericardiocentesis (
p
> 0.05 versus values immediately after pericardiocentesis). Conversely, no parameters of LV function changed after pericardiocentesis. Of 19 patients, 13 patients showed RV dysfunction immediately after pericardiocentesis and 6 patients did not. RV free wall longitudinal strain before pericardiocentesis in patients with post-procedural RV dysfunction was reduced compared to those without post-procedural RV dysfunction ( − 18.9 ± 3.6 versus − 28.4 ± 6.3%;
p
= 0.005). The area under the curve values for prediction of post-procedural RV dysfunction was 0.910 for RV free wall longitudinal strain. The occurrence of RV dysfunction after pericardiocentesis should be given more attention, and pre-procedural RV free wall longitudinal strain may be a predictor of post-procedural RV dysfunction.
Long QT syndrome type 3 (LQT3) is caused by gain-of-function mutations in the
gene, which encodes the α subunit of the cardiac voltage-gated sodium channel. LQT3 patients present bradycardia and ...lethal arrhythmias during rest or sleep. Further, the efficacy of β-blockers, the drug used for their treatment, is uncertain. Recently, a large multicenter LQT3 cohort study demonstrated that β-blocker therapy reduced the risk of life-threatening cardiac events in female patients; however, the detailed mechanism of action remains unclear.
This study aimed to establish LQT3-human induced pluripotent stem cells (hiPSCs) and to investigate the effect of propranolol in this model.
An hiPSCs cell line was established from peripheral blood mononuclear cells of a boy with LQT3 carrying the
-N1774D mutation. He had suffered from repetitive torsades de pointes (TdPs) with QT prolongation since birth (QTc 680 ms), which were effectively treated with propranolol, as it suppressed lethal arrhythmias. Furthermore, hiPSCs were differentiated into cardiomyocytes (CMs), on which electrophysiological functional assays were performed using the patch-clamp method.
N1774D-hiPSC-CMs exhibited significantly prolonged action potential durations (APDs) in comparison to those of the control cells (N1774D: 440 ± 37 ms vs. control: 272 ± 22 ms; at 1 Hz pacing;
< 0.01). Furthermore, N1774D-hiPSC-CMs presented gain-of-function features: a hyperpolarized shift of steady-state activation and increased late sodium current compared to those of the control cells. 5 μM propranolol shortened APDs and inhibited late sodium current in N1774D-hiPSC-CMs, but did not significantly affect in the control cells. In addition, even in the presence of intrapipette guanosine diphosphate βs (GDPβs), an inhibitor of G proteins, propranolol reduced late sodium current in N1774D cells. Therefore, these results suggested a unique inhibitory effect of propranolol on late sodium current unrelated to β-adrenergic receptor block in N1774D-hiPSC-CMs.
We successfully recapitulated the clinical phenotype of LQT3 using patient-derived hiPSC-CMs and determined that the mechanism, by which propranolol inhibited the late sodium current, was independent of β-adrenergic receptor signaling pathway.
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