Diltiazem Inhibits Coronary Spasm via Inhibition of Cav1.2Phosphorylation and Protein Kinase C Activation in a Mouse Model of Coronary Spastic Angina.

Calcium antagonists are used for coronary spastic angina (CSA) treatment. We previously identified a phospholipase C (PLC) -δ1 gene variant that results in enhanced PLC activity in patients with CSA and developed a CSA animal model by generating vascular smooth muscle cell-specific human variant PLC-δ1 overexpression (PLC-TG) mice. In this study, we investigated the molecular mechanism of CSA using the PLC-TG mice and the inhibitory effect of a calcium antagonist, diltiazem hydrochloride (DL).We treated the PLC-TG and wild-type (WT) mice with oral DL or trichlormethiazide (TM) (control) for 2 weeks. Ergometrine injection-induced coronary spasm was observed on the electrocardiogram in all 5 PLC-TG mice treated with TM, but only in 1 of 5 PLC-TG mice treated with DL. Voltage-dependent calcium channel (Cav1.2) phosphorylation and protein kinase C (PKC) activity were enhanced in the aortas of PLC-TG mice treated with TM. DL treatment significantly inhibited Cav1.2 phosphorylation and PKC activity. Although total Cav1.2 expression was similar between WT and PLC-TG mice treated with TM, DL treatment significantly increased its expression in PLC-TG mice. Furthermore, its expression remained high after DL discontinuation. DL and PKC inhibitor suppressed intracellular calcium response to acetylcholine in cultured rat aortic smooth muscle cells transfected with variant PLC-δ1.These results indicate that enhanced PLC activity causes coronary spasm, presumably via enhanced Cav1.2 phosphorylation and PKC activity, both of which were inhibited by DL. Enhanced total Cav1.2 expression after DL discontinuation and high PKC activity may be an important mechanism underlying the calcium antagonist withdrawal syndrome.

Safety and Efficacy of Subcutaneous Cardioverter Defibrillator in Patients at High Risk of Sudden Cardiac Death　- Primary Japanese Experience.

BACKGROUND: The entirely subcutaneous implantable cardioverter defibrillator (S-ICD) was introduced as a new alternative to conventional transvenous ICD (TV-ICD) in Japan in February 2016, but its safety and efficacy are unclear.Methods and Results:A total of 60 patients (48 men, median age, 60 years; IQR, 44-67 years; primary prevention, n=24) underwent S-ICD implantation between February 2016 and August 2017. The device pocket was formed in the intermuscular space between the serratus anterior muscle and the latissimus dorsi muscle, and the parasternal S-ICD lead was placed according to pre-implant screening. Defibrillation test was performed in 56 patients (93%). Ventricular fibrillation (VF) was induced in 55 patients and terminated by a single 65-J shock in all patients. The median time to shock therapy was 13.4 s (IQR, 12.1-14.9 s) and the median post-shock impedance of the S-ICD lead was 64 Ω (IQR, 58-77 Ω). There were no operation-related complications or subsequent infectious complications. During follow-up (median, 275 days; IQR, 107-421 days), 1 patient (1.7%) had appropriate shock for VF with successful termination, whereas 5 patients (8.3%) had inappropriate shock due to oversensing of myopotential (n=3) or T-wave (n=1), and detection of supraventricular tachycardia (n=1). CONCLUSIONS: S-ICD is a safe and effective alternative to conventional TV-ICD. The long-term safety and efficacy of the S-ICD need further investigation.

Modified sympathetic nerve regulation in AKAP5-null mice.

Genetic analyses have revealed an important association between A-kinase anchoring proteins (AKAPs) and the intracellular calcium modulating system. AKAP5, also known as AKAP79/150, is an anchoring protein between PKA and voltage-dependent calcium channels, ryanodine receptor-2, phospholamban and other molecules. The aim of the present study was to elucidate the physiological importance of AKAP5 in the creation of cardiac rhythm using AKAP5-null mice. ECG analysis showed a normal sinus rhythm and a decreased responsiveness to isoproterenol in AKAP5-null mice compared with wild-type mice. Analysis of heart rate variability revealed that the R-R interval was unstable in AKAP5-null mutants and that the low-frequency components had decreased, indicating that the tonus of the sympathetic nervous system was affected. Furthermore, the atrium of the AKAP5-null mice showed a decreased positive inotropic response to isoproterenol, indicating the involvement of AKAP5 in a PKA-dependent pathway. Thus, our present study revealed that AKAP5 plays a significant role in the regulation of sympathetic nerve activities.

Long Postpacing Interval After Entrainment of Tachycardia Including a Slow Conduction Zone Within the Circuit.

BACKGROUNDS: Postpacing interval (PPI) measured after entrainment pacing describes the distance between pacing site and reentrant circuit. However, the influential features to PPI remain to be elucidated. METHODS AND RESULTS: This study included 22 cases with slow/fast atrioventricular (AV) nodal reentrant tachycardia (AVNRT), 14 orthodromic AV reciprocating tachycardia (AVRT) using an accessary pathway, 22 typical atrial flutter (AFL), and 18 other macroreentrant atrial tachycardia (atypical AFL). Rapid pacing at a pacing cycle length (PCL) 5% shorter than tachycardia cycle length (TCL) was done from a site on or close to the reentry circuit. Pacing sites included the coronary sinus ostium in AVNRT, earliest atrial activation site in AVRT, and cavotricuspid isthmus in typical AFL. In atypical AFL, tachycardia circuit was determined on the basis of CARTO mapping, and then the pacing site was. TCL was significantly longer in AVNRT and AVRT than in typical AFL and atypical AFL (both P < 0.05). PCL minus TCL value was similar among the 4 groups. PPI minus TCL value (milliseconds) was significantly longer in AVNRT (median, 40 [IQR, 29-60.8]) and AVRT (34 [20-47]) than in typical AFL (0 [0-4]) and atypical AFL (3.5 [0-8]) (both P < 0.05). Furthermore, PPI minus TCL was prolonged with shortening of PCL in AVNRT and AVRT (both P < 0.05), whereas it was unchanged in typical AFL (P = 0.50). CONCLUSION: PPI after concealed entrainment is prolonged compared with TCL when the reentry circuit involves a slow conduction zone with a decremental conduction property such as the AV node.

Olmesartan Inhibits Cardiac Hypertrophy in Mice Overexpressing Renin Independently of Blood Pressure: Its Beneficial Effects on ACE2/Ang(1-7)/Mas Axis and NADPH Oxidase Expression.

Enhanced renin-angiotensin activity causes hypertension and cardiac hypertrophy. The angiotensin (Ang)-converting enzyme (ACE)2/Ang(1-7)/Mas axis pathway functions against Ang II type 1 receptor (AT1R) signaling. We investigated whether olmesartan (Olm), an AT1R blocker, inhibits cardiac hypertrophy independently of blood pressure, and evaluated the potential mechanisms. The 3- to 4-month-old male mice overexpressing renin in the liver (Ren-Tg) were given Olm (5 mg/kg/d) and hydralazine (Hyd) (3.5 mg/kg/d) orally for 2 months. Systolic blood pressure was higher in the Ren-Tg mice than in wild-type littermates. Olm and Hyd treatments lowered systolic blood pressure to the same degree. However, cardiac hypertrophy, evaluated by echocardiography, heart weight, cross-sectional area of cardiomyocytes, and gene expression, was inhibited by only Olm treatment, but not by Hyd. Olm treatment reversed decreased gene expressions of ACE2 and Mas receptor of Ren-Tg mice and inhibited enhanced NADPH oxidase (Nox)4 expression and reactive oxygen species, whereas Hyd treatment had no influence on them. These findings indicate that Olm treatment inhibits cardiac hypertrophy independently of blood pressure, not only through its original AT1R blockade but partly through enhancement of ACE2/Ang(1-7)/Mas axis and suppression of Nox4 expression.

NF-κB-dependent increase in tissue factor expression is responsible for hypoxic podocyte injury.

BACKGROUND: Fibrin deposition within glomeruli is commonly seen in kidney biopsy specimens, suggesting enhanced coagulant activity. Tissue factor (TF) is a coagulation factor which is also related to various biological effects, and TF is upregulated by hypoxia in cancer cells. Recently, hypoxic podocyte injury has been proposed, therefore, we investigated TF expression in hypoxia. METHODS: Conditionally immortalized human podocytes were differentiated and treated under hypoxic or normoxic conditions. mRNA expressions of TF and tissue factor pathway inhibitor (TFPI) were analyzed by quantitative RT-PCR. Protein levels of TF and TFPI were tested by enzyme-linked immunosorbent assay. We employed small interfering RNA (siRNA) to temporary knockdown early growth response protein 1 (Egr-1), hypoxia-inducible factor-1α (HIF-1α) and TF. The expression of CD2-associated protein (CD2AP) mRNA and phalloidin staining was examined to assess podocyte injury. RESULTS: Hypoxia increased mRNA expression of TF (6 h: 2.3 ± 0.05 fold, p < 0.001, 24 h: 5.6 ± 2.4 fold, p < 0.05) and suppressed TFPI (6 h: 0.54 ± 0.04 fold, p < 0.05, 24 h: 0.24 ± 0.06 fold, p < 0.001) compared with normoxia. Similarly, protein levels of TF were increased and TFPI were decreased. Egr-1 siRNA did not change TF mRNA expression. Pyrrolidine dithiocarbamate (PDTC), a nuclear factor kappa B (NF-κB) inhibitor, significantly reduced hypoxia induced TF expression, and HIF-1α knockdown further increased TF. Hypoxia resulted in decreased CD2AP and actin reorganization in podocytes, and these changes were attenuated by TF siRNA. CONCLUSION: Hypoxia increased the expression of TF in human podocytes NF-κB dependently. TF may have a critical role in the hypoxic podocyte injury.

Public awareness of palliative care for heart failure in Japan: A cross-sectional study.

BACKGROUND: Palliative care (PC) benefits cancer patients and those with heart failure (HF), improving quality of life and symptom burden. Despite guidelines recommending the integration of PC into HF care, its use remains inadequate, partly due to insufficient public awareness. This study aimed to assess the public awareness of PC for HF in Japan and identify factors associated with awareness. METHODS: A cross-sectional online survey was conducted from March 6-13, 2023, using a panel operated by Intage Inc. (Tokyo, Japan), which has a pool of 3.78 million potential Japanese respondents. The survey included 51,790 participants, matched for sex, age, and region of residence. Participants were asked about their awareness of PC eligibility for HF, along with demographic information, history of hospitalization for sudden illness, outpatient visits, and health status in the previous 2 years. The χ2 test and Cramer's V were used to analyze associations between awareness and variables, and multivariate logistic regression was used to estimate awareness predictors. RESULTS: In total, 91 % of participants were unaware of PC eligibility for HF. Age group, healthcare professional occupation, and history of hospitalization for acute myocardial infarction, acute HF, acute pulmonary embolism, and ruptured aortic aneurysm had weak to moderate associations with awareness. Multivariate analysis revealed that a history of hospitalization for sudden cardiovascular illness and being a healthcare professional were positively related to awareness, while age, female sex, and being married were associated with lower odds of awareness. CONCLUSION: The low public awareness of PC for HF in Japan underscores the importance of increasing awareness of the eligibility of PC for HF, as well as cancer, to integrate PC into HF practice as basic care.

Comparing cryoballoon and contact-force guided radiofrequency ablation in pulmonary vein isolation for atrial fibrillation in patients with hypertrophic cardiomyopathy.

BACKGROUND: Pulmonary vein isolation (PVI) employing cryoballoon (CB) or contact force-guided radiofrequency (CF-RF) catheter ablation has been established as an effective strategy for managing atrial fibrillation (AF). However, its efficacy in hypertrophic cardiomyopathy (HCM) remains to be further explored. METHODS: This retrospective study analyzed 60 consecutive AF patients with HCM (average age 67 ± 10 years; 41 men) who were consecutively admitted to our hospital from January 2014 to December 2022 and underwent initial PVI. RESULTS: The patients were treated with CB (26 patients) or CF-RF (34 patients). Successful PVI was achieved in both groups without significant complications. In the CF-RF group, additional ablations were performed on the cavotricuspid isthmus (14.7% of patients) and the anterior line (2.9%). The CB group benefited from reduced procedural times (93 ± 31 vs. 165 ± 60 min, p < 0.05) and decreased saline irrigation requirements (77.5 ± 31.4 vs. 870 ± 281.9 mL, p < 0.0001). Using a contrast medium was exclusive to the CB group (33.8 ± 4.2 mL). In a 12-month follow-up, the atrial tachyarrhythmia recurrence-free rates in the CB and CF-RF groups were comparable (77% and 76%, respectively; p = 0.63 according to the log-rank test). Notably, pulmonary vein reconnection was prevalent in most (7 out of 8) patients requiring a secondary ablation procedure. CONCLUSION: PVI is feasible as a strategy for AF in patients with HCM employing either CB or CF-RF techniques. While the recurrence-free rates were comparable in both groups, differences were noted in procedure duration, saline usage, and the need for a contrast medium.

Landiolol, an intravenous ß1-selective blocker, is useful for dissociating a fusion of atrial activation via accessory pathway and atrioventricular node.

Introduction: During ventricular pacing, a fusion of atrial activation may occur owing to the simultaneous retrograde conduction of the atrioventricular (AV) node and accessory pathway (AP), potentially leading to an inaccurate mapping of the atrial AP insertion site. Objective: We tested the hypothesis that landiolol, an ultra-short-acting intravenous ß1-blocker, could dissociate a fusion of atrial activation. Methods: We conducted a prospective before-and-after study to investigate the effect of landiolol on retrograde conduction via the AV node and AP. We enrolled 21 consecutive patients with orthodromic AV reciprocating tachycardia who underwent electrophysiological studies at our hospital between January 1, 2018, and August 31, 2020. Results: Six patients exhibited a fusion of atrial activation. After landiolol administration (10 µg/kg/min), the effective refractory period was unchanged in AP (280 [240-290] ms vs. 280 [245-295] ms, p = .91), whereas that of the AV node was prolonged (275 [215-380] ms vs. 332 [278-445] ms, p = .03). The Wenckebach pacing rate via retrograde AV node decreased after landiolol administration (180 [140-200] beats per minute [bpm] vs. 140 [120-180] bpm, p = .02). Thus, landiolol decreased the minimum ventricular pacing rate required to dissociate a fusion of atrial activation (180 [160-200] bpm vs. 140 [128-155] bpm, p = .007). Radiofrequency catheter ablation under landiolol administration successfully eliminated AP in all patients during ventricular pacing without complications or recurrence. Conclusion: Landiolol inhibited the AV node without affecting the AP and helped dissociate a fusion of atrial activation at a lower ventricular pacing rate.

Contrast injection into the right atrial appendage apex using an external irrigation catheter for focal atrial tachycardia ablation.

Focal atrial tachycardias (ATs) originating from the right atrial appendage (RAA) apex are refractory to catheter ablation and can cause tachycardia-induced cardiomyopathy. After unsuccessful catheter ablation of these ATs, their elimination sometimes requires atrial appendectomy for treatment of tachycardia-induced cardiomyopathy. This case demonstrates that contrast injection into the RAA apex using an external irrigation catheter can facilitate mapping of such ATs and may provide safe and effective ablation of their sources even in the RAA tip.

Characterization of the PRAETORIAN score in Japanese patients undergoing subcutaneous implantable cardioverter-defibrillator implantation.

BACKGROUND: The PRAETORIAN score was developed to evaluate the implant position and predict defibrillation success in patients implanted with a subcutaneous implantable cardioverter-defibrillator (S-ICD). However, usefulness of the PRAETORIAN score for Japanese patients is unknown. METHODS: We evaluated usefulness of this score, which was determined by width of sub-coil fat, sub-generator fat, and anterior positioning of the S-ICD generator by post-operative chest X-ray, in consecutive 100 Japanese S-ICD implanted patients [78 men, median age 59 (IQR 46.5-67.0) years, median body mass index (BMI) 24.2 (21.3-27.2) kg/m2]. RESULTS: The median PRAETORIAN score was 30 (30-45) and 93 patients were classified as a low risk of conversion failure. The remaining seven were at an intermediate risk. Almost all patients were classified as an optimal pulse-generator position in the second and third steps of the PRAETORIAN score. The only difference observed was in the width of sub-coil fat in the first step. To further evaluate its significance, patients were divided into the Thicker group (sub-coil fat >1 coil width, n = 19) and the Thinner group (sub-coil fat ≤1 coil width, n = 81). BMI and post-shock impedance were both higher in the Thicker group than in the Thinner group [27.1 (25.6-31.6) versus 23.1 (20.9-25.7) kg/m2, p < 0.001, and 75 (68-88) versus 63 (55-74) Ω, p = 0.003, respectively]. During the median follow-up periods of 888 (523-1418) days, 7 patients experienced appropriate shock therapy for spontaneous ventricular tachyarrhythmias, who were all at a low risk. No conversion failure was observed. Inappropriate shock (IAS) occurred in 11 patients, and there was no difference in IAS rate between the Thicker group (n = 2) and the Thinner group (n = 9) (p = 0.747 by log-rank test). CONCLUSIONS: Most Japanese patients were classified as at low risk of conversion failure. The PRAETORIAN score may be useful for the evaluation of conversion failure in Japanese S-ICD implanted patients.

A novel screening test for inappropriate shocks due to myopotentials from the subcutaneous implantable cardioverter-defibrillator.

BACKGROUND: The subcutaneous implantable cardioverter-defibrillator (S-ICD) is effective in preventing sudden cardiac death. Compared with transvenous ICDs, S-ICDs have a lower rate of inappropriate shocks (IASs) for supraventricular arrhythmias, but such shocks for T-wave oversensing (TWO) and extracardiac myopotentials are more common. No screening tests to identify patients at risk for IAS due to myopotential interference (MPI) currently are available. OBJECTIVE: The purpose of this study was to assess the efficacy of a tube exercise test (TET) developed to detect MPI post S-ICD implantation. METHODS: TET includes 3 different maneuvers using an exercise tube. S-ICD electrograms were recorded to assess MPI while patients performed each of the maneuvers. RESULTS: TET was performed in 43 patients, and MPI was observed in 12 patients (28%). In 10 of the 12 TET-positive patients, the positive vector corresponded with a vector that did not show TWO on standard S-ICD preoperative screening. During median follow-up of 672 days (interquartile range 465-805 days), 3 patients (7%) experienced IAS due to MPI. Importantly, the vector at the time of IAS in all 3 patients passed standard preoperative screening for TWO but was positive with TET. Sensitivity and specificity of TET were 100% and 78%, respectively, and positive and negative predictive values were 25% and 100%, respectively. CONCLUSION: Postimplant screening for MPI identified patients at increased risk for IAS. TET may be helpful for guiding optimal programming to prevent IAS.

Enhanced transient receptor potential channel-mediated Ca2+ influx in the cells with phospholipase C-δ1 overexpression: its possible role in coronary artery spasm.

We reported that coronary spasm was induced in the transgenic mice with the increased phospholipase C (PLC)-δ1 activity. We investigated the effect of enhanced PLC-δ1 on Ca2+ influx and its underlying mechanisms. We used human embryonic kidney (HEK)-293 and coronary arteries smooth muscle cells (CASMC). Intracellular free Ca2+ concentration ([Ca2+ ]i ; nm) was measured by fura-2, and Ca2+ influx was evaluated by the increase in [Ca2+ ]i after addition of extracellular Ca2+ . Acetylcholine (ACh) was used to induce Ca2+ influx. ACh-induced peak Ca2+ influx was 19 ± 3 in control HEK-293 cells and 71 ± 8 in the cells with PLC-δ1 overexpression (P < 0.05 between two groups). Nifedipine partially suppressed this Ca2+ influx, whereas either 2-APB or knockdown of classical transient receptor potential channel 6 (TRPC6) blocked this Ca2+ influx. In the human CASMC, ACh-induced peak Ca2+ influx was 29 ± 6 in the control and was increased to 45 ± 16 by PLC-δ1 overexpression (P < 0.05). Like HEK-293 cells, pretreatment with nifedipine partially suppressed Ca2+ influx, whereas either 2-APB or knockdown of TRPC6 blocked it. ACh-induced Ca2+ influx was enhanced by PLC-δ1 overexpression, and was blocked partially by nifedipine and completely by 2-APB. TRPC-mediated Ca2+ influx may be related to the enhanced Ca2+ influx in PLC-δ1 overexpression.

Safety and efficacy of contemporary catheter ablation for atrial fibrillation patients with a history of cardioembolic stroke in the era of direct oral anticoagulants.

BACKGROUND: The safety and efficacy of the contemporary atrial fibrillation (AF) ablation in patients with a recent or previous history of cardioembolic stroke (CS) or transient ischemic attack (TIA) remain to be established. METHODS: A total of 447 patients who underwent first-ever contact force (CF)-guided AF ablation with circumferential pulmonary vein isolation were included. Of these, 17 had CS or TIA within 6 months before ablation (Group 1), 30 more than 6 months before ablation (Group 2), and the other 400 without CS or TIA (Group 3). Procedural complications and recurrence of AF and atrial tachyarrhythmias were compared among the 3 groups. RESULTS: The mean age was 71±7, 66±9, and 61±11 years in Groups 1, 2, and 3, respectively (p<0.05, Group 1 versus Group 3). The oral anticoagulants were warfarin (n=108, 24.1%), dabigatran (n=101, 22.6%), rivaroxaban (n=147, 32.9%), apixaban (n=87, 19.5%), and edoxaban (n=4, 0.9%), and did not differ among the 3 groups. Median follow-up period was 14 [IQR 12-22], 13 [12-14], and 12 [10-16] months, respectively. One episode of cardiac tamponade, 2 episodes of arteriovenous fistula, and some minor complications occurred in Group 3, but no complications occurred in Groups 1 and 2 in the periprocedural period. Although one episode of CS occurred 11 days after the procedure in Group 3, there were no periprocedural CS, TIA, or major bleedings in Groups 1 and 2. AF recurrence-free rate after the procedure was 76.5%, 86.7%, and 79.1% in Groups 1, 2, and 3, respectively, and there was no difference in Kaplan-Meier curves among the 3 groups. CONCLUSION: The safety and efficacy of CF-guided AF ablation in the era of direct oral anticoagulants in patients with a recent or previous history of CS or TIA are similar to those in patients without it.