Variation in the frozen lesion size according to the non-occluded application duration and technique for cryoballoon ablation.

OBJECTIVE: The frozen lesion formation created by cryoballoon ablation, especially with non-occluded applications, has not been fully evaluated. This study aimed to validate the lesion size under different cryoballoon ablation settings: application duration, push-up technique, and laminar flow. METHODS: The frozen lesion size was evaluated immediately after ending the freezing with three different application durations (120, 150, and 180 seconds) in porcine hearts (N = 24). During the application, the push-up technique was applied at 10, 20, and 30 seconds after starting the freezing with or without laminar flow. RESULTS: The lesion size was significantly correlated with the nadir balloon temperature (P<0.001). The lesion volume became significantly larger after 150 seconds than 120 seconds (1272mm3 versus 1709mm3, P = 0.004), but not after 150 seconds (versus 1876mm3 at 180 seconds, P = 0.29) with a comparable nadir balloon temperature. Furthermore, the lesion volume became significantly larger with the push-up technique with the largest lesion size with a 20-second push-up after the freezing (1193mm3 without the push-up technique versus 1585mm3 with a push-up at 10 seconds versus 1808mm3 with a push-up at 20 seconds versus 1714mm3 with a push-up at 30 seconds, P = 0.04). Further, the absence of laminar flow was not associated with larger lesion size despite a significantly lower nadir balloon temperature. CONCLUSION: The frozen lesion size created by cryoballoon ablation became larger with longer applications at least 150 seconds and with a push-up technique especially at 20 seconds after the freezing.

Nardilysin in adipocytes regulates UCP1 expression and body temperature homeostasis.

Brown adipose tissue (BAT) dissipates chemical energy as heat through uncoupling protein 1 (UCP1). The induction of mitochondrial reactive oxygen species (ROS) in BAT was recently identified as a mechanism that supports UCP1-dependent thermogenesis. We previously demonstrated that nardilysin (NRDC) plays critical roles in body temperature homeostasis. Global NRDC-deficient (Nrdc-/-) mice show hypothermia due to a lower set point for body temperature, whereas BAT thermogenesis at room temperature (RT) is enhanced mainly to compensate for poor thermal insulation. To examine the primary role of NRDC in BAT thermogenesis, we generated adipocyte-specific NRDC-deficient (Adipo-KO) mice by mating Nrdc floxed (Nrdcflox/flox) mice with adiponectin-Cre mice. Adipo-KO mice showed hyperthermia at both RT and thermoneutrality. They were also more cold-tolerant than Nrdcflox/flox mice. However, UCP1 mRNA levels were significantly lower in Adipo-KO BAT at RT, thermoneutrality, and 4 °C, whereas no significant differences were observed in UCP1 protein levels at RT and 4 °C. We examined the protein stability of UCP1 using the cycloheximide chase assay and found that NRDC negatively regulated its stability via the ubiquitin-proteasome pathway. NRDC may be also involved in ROS-mediated in vivo thermogenesis because the inhibitory effects of N-acetyl cysteine, an ROS scavenger, on ß3 agonist-induced thermogenesis were stronger in Adipo-KO mice. Collectively, the present results demonstrate that NRDC in BAT controls adaptive thermogenesis and body temperature homeostasis possibly via the regulation of UCP1 protein stability and ROS levels.

Nardilysin controls cardiac sympathetic innervation patterning through regulation of p75 neurotrophin receptor.

Cardiac sympathetic innervation is critically involved in the regulation of circulatory dynamics. However, the molecular mechanism for the innervation patterning has remained elusive. Here, we demonstrate that nardilysin (NRDC, Nrdc), an enhancer of ectodomain shedding, regulates cardiac sympathetic innervation. Nardilysin-deficient (Nrdc-/- ) mice show hypoplastic hearts, hypotension, bradycardia, and abnormal sympathetic innervation patterning. While the innervation of left ventricle (LV) of wild-type mice is denser in the subepicardium than in the subendocardium, Nrdc-/- LV lacks such a polarity and is uniformly and more abundantly innervated. At the molecular level, the full-length form of p75 neurotrophin receptor (p75NTR , Ngfr) is increased in Nrdc-/- LV due to the reduced ectodomain shedding of p75NTR . Importantly, the reduction of p75NTR rescued the abnormal innervation phenotype of Nrdc-/- mice. Moreover, sympathetic neuron-specific, but not cardiomyocyte-specific deletion of Nrdc recapitulated the abnormal innervation patterning of Nrdc-/- mice. In conclusion, neuronal nardilysin critically regulates cardiac sympathetic innervation and circulatory dynamics via modulation of p75NTR .

Decline in Left Ventricular Ejection Fraction During Follow-Up in Patients With Severe Aortic Stenosis.

OBJECTIVES: The aim of this study was to investigate the prognostic impact of the decline in left ventricular ejection fraction (LVEF) at 1-year follow-up in patients with severe aortic stenosis (AS) managed conservatively. BACKGROUND: No previous study has explored the association between LVEF decline during follow-up and clinical outcomes in patients with severe AS. METHODS: Among 3,815 patients with severe AS enrolled in the multicenter CURRENT AS (Contemporary Outcomes After Surgery and Medical Treatment in Patients With Severe Aortic Stenosis) registry in Japan, 839 conservatively managed patients who underwent echocardiography at 1-year follow-up were analyzed. The primary outcome measure was a composite of AS-related deaths and hospitalization for heart failure. RESULTS: There were 91 patients (10.8%) with >10% declines in LVEF and 748 patients (89.2%) without declines. Left ventricular dimensions and the prevalence of valve regurgitation and atrial fibrillation or flutter significantly increased in the group with declines in LVEF. The cumulative 3-year incidence of the primary outcome measure was significantly higher in the group with declines in LVEF than in the group with no decline (39.5% vs. 26.5%; p < 0.001). After adjusting for confounders, the excess risk of decline in LVEF over no decline for the primary outcome measure remained significant (hazard ratio: 1.98; 95% confidence interval: 1.29 to 3.06). When stratified by LVEF at index echocardiography (≥70%, 60% to 69%, and <60%), the risk of decline in LVEF on the primary outcome was consistently seen in all the subgroups, without any interaction (p = 0.77). CONCLUSIONS: Patients with severe AS with >10% declines in LVEF at 1 year after diagnosis had worse AS-related clinical outcomes than those without declines in LVEF under conservative management. (Contemporary Outcomes After Surgery and Medical Treatment in Patients With Severe Aortic Stenosis Registry; UMIN000012140).

Prognostic Impact of Aortic Valve Area in Conservatively Managed Patients With Asymptomatic Severe Aortic Stenosis With Preserved Ejection Fraction.

Background Data are scarce on the role of aortic valve area (AVA) to identify those patients with asymptomatic severe aortic stenosis (AS) who are at high risk of adverse events. We sought to explore the prognostic impact of AVA in asymptomatic patients with severe AS in a large observational database. Methods and Results Among 3815 consecutive patients with severe AS enrolled in the CURRENT AS (Contemporary Outcomes After Surgery and Medical Treatment in Patients With Severe Aortic Stenosis) registry, the present study included 1309 conservatively managed asymptomatic patients with left ventricular ejection fraction ≥50%. The study patients were subdivided into 3 groups based on AVA (group 1: AVA >0.80 cm2, N=645; group 2: 0.8 cm2 ≥AVA >0.6 cm2, N=465; and group 3: AVA ≤0.6 cm2, N=199). The prevalence of very severe AS patients (peak aortic jet velocity ≥5 m/s or mean aortic pressure gradient ≥60 mm Hg) was 2.0%, 5.8%, and 26.1% in groups 1, 2, and 3, respectively. The cumulative 5-year incidence of AVR was not different across the 3 groups (39.7%, 43.7%, and 39.9%; P=0.43). The cumulative 5-year incidence of the primary outcome measure (a composite of aortic valve-related death or heart failure hospitalization) was incrementally higher with decreasing AVA (24.1%, 29.1%, and 48.1%; P<0.001). After adjusting for confounders, the excess risk of group 3 and group 2 relative to group 1 for the primary outcome measure remained significant (hazard ratio, 2.21, 95% CI, 1.56-3.11, P<0.001; and hazard ratio, 1.34, 95% CI, 1.01-1.78, P=0.04, respectively). Conclusions AVA ≤0.6 cm2 would be a useful marker to identify those high-risk patients with asymptomatic severe AS, who might benefit from early AVR. Clinical Trial Registration URL: www.umin.ac.jp . Unique identifier: UMIN000012140.

B-type natriuretic peptide in patients with asymptomatic severe aortic stenosis.

OBJECTIVES: We sought to evaluate the prognostic impact of the B-type natriuretic peptide (BNP) levels in patients with asymptomatic severe aortic stenosis (AS), who were not referred for aortic valve replacement (AVR). METHODS: We used data from a Japanese multicentre registry, the Contemporary outcomes after sURgery and medical tREatmeNT in patients with severe Aortic Stenosis Registry, which enrolled 3815 consecutive patients with severe AS. Of those, 387 asymptomatic patients who were not referred for AVR without left ventricular dysfunction and very severe AS were subdivided into four groups based on their BNP levels (BNP<100 pg/mL, n=201; 100≤BNP<200 pg/mL, n=94; 200≤BNP<300 pg/mL, n=42 and BNP>300 pg/mL, n=50). RESULTS: The cumulative 5-year incidence of AS-related events (aortic valve-related death or heart failure hospitalisation) was incrementally higher with increasing BNP level (14.2%, 29.6%, 46.3% and 47.0%, p<0.001). After adjusting for confounders, the risk for AS-related events was incrementally greater with increasing BNP levels (HR: 1.97, 95% CI: 0.97 to 3.98, p=0.06; HR: 3.59, 95% CI: 1.55 to 8.32, p=0.03 and HR: 7.38, 95% CI: 3.21 to 16.9, p<0.001, respectively). Notably, asymptomatic patients with BNPlevels of <100 pg/mL had an event rate of only 2.1% at 1 year. CONCLUSIONS: Increased BNP level was associated with a higher risk for AS-related adverse events in patients with asymptomatic severe AS with normal left ventricular ejection fraction who were not referred for AVR. Asymptomatic patients with BNP levels of <100 pg/mL had relatively low event rate, who might be safely followed with watchful waiting strategy. TRAIL REGISTRATION NUMBER: UMIN000012140.

Genome-wide profiling of nardilysin target genes reveals its role in epigenetic regulation and cell cycle progression.

Post-translational histone modifications, such as acetylation and methylation, are prerequisites for transcriptional regulation. The metalloendopeptidase nardilysin (Nrdc) is a H3K4me2-binding protein that controls thermoregulation and ß-cell functions through its transcriptional coregulator function. We herein combined high-throughput ChIP-seq and RNA-seq to achieve the first genome-wide identification of Nrdc target genes. A ChIP-seq analysis of immortalized mouse embryo fibroblasts (iMEF) identified 4053 Nrdc-binding sites, most of which were located in proximal promoter sites (2587 Nrdc-binding genes). Global H3K4me2 levels at Nrdc-binding promoters slightly increased, while H3K9ac levels decreased in the absence of Nrdc. Among Nrdc-binding genes, a comparative RNA-seq analysis identified 448 candidates for Nrdc target genes, among which cell cycle-related genes were significantly enriched. We confirmed decreased mRNA and H3K9ac levels at the promoters of individual genes in Nrdc-deficient iMEF, which were restored by the ectopic introduction of Nrdc. Reduced mRNA levels, but not H3K9ac levels were fully restored by the reintroduction of the peptidase-dead mutant of Nrdc. Furthermore, Nrdc promoted cell cycle progression at multiple stages, which enhanced cell proliferation in vivo. Collectively, our integrative studies emphasize the importance of Nrdc for maintaining a proper epigenetic status and cell growth.

Causes of Death in Patients with Severe Aortic Stenosis: An Observational study.

Whether patients with severe aortic stenosis (AS) die because of AS-related causes is an important issue for the management of these patients. We used data from CURRENT AS registry, a Japanese multicenter registry, to assess the causes of death in severe AS patients and to identify the factors associated with non-cardiac mortality. We enrolled 3815 consecutive patients with a median follow-up of 1176 days; the 1449 overall deaths comprised 802 (55.3%) from cardiac and 647 (44.7%) from non-cardiac causes. Heart failure (HF) (25.7%) and sudden death (13.0%) caused the most cardiac deaths, whereas infection (13.0%) and malignancy (11.1%) were the main non-cardiac causes. According to treatment strategies, infection was the most common cause of non-cardiac death, followed by malignancy, in both the initial aortic valve replacement (AVR) cohort (N = 1197), and the conservative management cohort (N = 2618). Both non-cardiac factors (age, male, body mass index <22, diabetes, prior history of stroke, dialysis, anemia, and malignancy) and cardiac factors (atrial fibrillation, ejection fraction <68%, and the initial AVR strategy) were associated with non-cardiac death. These findings highlight the importance of close monitoring of non-cardiac comorbidities, as well as HF and sudden death, to improve the mortality rate of severe AS patients.

Prognostic Impact of Peak Aortic Jet Velocity in Conservatively Managed Patients With Severe Aortic Stenosis: An Observation From the CURRENT AS Registry.

BACKGROUND: There are limited data regarding the risk stratification based on peak aortic jet velocity (Vmax) in patients with severe aortic stenosis (AS). METHODS AND RESULTS: Among 3815 consecutive patients with severe AS enrolled in the CURRENT AS (Contemporary Outcomes After Surgery and Medical Treatment in Patients With Severe Aortic Stenosis) registry, the study population consisted of 1075 conservatively managed patients with Vmax ≥4.0 m/s and left ventricular ejection fraction ≥50%. The study patients were subdivided into 3 groups based on Vmax (group 1, 4.0 ≤ Vmax <4.5 m/s, N=550; group 2, 4.5 ≤ Vmax <5 m/s, N=279; and group 3, Vmax ≥5 m/s, N=246). Cumulative 5-year incidence of AS-related events (aortic valve-related death or heart failure hospitalization) was incrementally higher with increasing Vmax (entire population; 38.0%, 49.4%, and 62.8%, P<0.001; symptomatic patients; 55.7%, 60.9%, and 72.2%, P=0.008; and asymptomatic patients; 29.4%, 38.9%, and 47.7%, P=0.005). After adjusting for confounders, the excess risk of group 2 and group 3 relative to group 1 for AS-related events remained significant (hazard ratio, 1.39; 95% CI, 1.07-1.81; P=0.02, and hazard ratio, 1.53; 95% CI, 1.17-2.00; P=0.002, respectively). The effect size of group 3 relative to group 1 for AS-related events in asymptomatic patients (N=479) was similar to that in symptomatic patients (N=596; hazard ratio, 1.59; 95% CI, 1.01-2.52; P=0.047, and hazard ratio, 1.67; 95% CI, 1.16-2.40, P=0.008, respectively), and there was no significant overall interaction between the symptomatic status and the effect of the Vmax categories on AS-related events (interaction, P=0.88). CONCLUSIONS: In conservatively managed severe AS patients with preserved left ventricular ejection fraction, increasing Vmax was associated with incrementally higher risk for AS-related events. However, the cumulative 5-year incidence of the AS-related events remained very high even in asymptomatic patients with less greater Vmax.

High- Versus Low-Gradient Severe Aortic Stenosis: Demographics, Clinical Outcomes, and Effects of the Initial Aortic Valve Replacement Strategy on Long-Term Prognosis.

BACKGROUND: There is considerable debate on the management of patients with low-gradient severe aortic stenosis (LG-AS), defined as aortic valve area <1 cm2 with peak aortic jet velocity ≤4.0 m/s, and mean aortic pressure gradient ≤40 mm Hg. METHODS AND RESULTS: In the CURRENT AS registry (Contemporary Outcomes After Surgery and Medical Treatment in Patients With Severe Aortic Stenosis), there were 2097 patients (initial aortic valve replacement [AVR] strategy: n=977, and conservative strategy: n=1120) with high-gradient severe aortic stenosis (HG-AS) and 1712 patients (initial AVR strategy: n=219, and conservative strategy: n=1493) with LG-AS. AVR was more frequently performed in HG-AS patients than in LG-AS patients (60% versus 28%) during the entire follow-up. In the comparison between the initial AVR and conservative groups, the propensity score-matched cohorts were developed in both HG-AS (n=887 for each group) and LG-AS (n=218 for each group) strata. The initial AVR strategy when compared with the conservative strategy was associated with markedly lower risk for a composite of aortic valve-related death or heart failure hospitalization in both HG-AS and LG-AS strata (hazard ratio, 0.30; 95% confidence interval, 0.25-0.37; P<0.001 and hazard ratio, 0.46; 95% confidence interval, 0.32-0.67; P<0.001, respectively). Among 1358 patients with LG-AS with preserved left ventricular ejection fraction, the initial AVR strategy was associated with a better outcome than the conservative strategy (adjusted hazard ratio, 0.37; 95% confidence interval, 0.23-0.59; P<0.001). CONCLUSIONS: The initial AVR strategy was associated with better outcomes than the conservative strategy in both HG-AS and LG-AS patients, although AVR was less frequently performed in LG-AS patients than in HG-AS patients. The favorable effect of initial AVR strategy was also seen in patients with LG-AS with preserved left ventricular ejection fraction. CLINICAL TRIAL REGISTRATION: URL: http://www.umin.ac.jp/ctr/index.htm. Unique identifier: UMIN000012140.

Initial Surgical Versus Conservative Strategies in Patients With Asymptomatic Severe Aortic Stenosis.

BACKGROUND: Current guidelines generally recommend watchful waiting until symptoms emerge for aortic valve replacement (AVR) in asymptomatic patients with severe aortic stenosis (AS). OBJECTIVES: The study sought to compare the long-term outcomes of initial AVR versus conservative strategies following the diagnosis of asymptomatic severe AS. METHODS: We used data from a large multicenter registry enrolling 3,815 consecutive patients with severe AS (peak aortic jet velocity >4.0 m/s, or mean aortic pressure gradient >40 mm Hg, or aortic valve area <1.0 cm(2)) between January 2003 and December 2011. Among 1,808 asymptomatic patients, the initial AVR and conservative strategies were chosen in 291 patients, and 1,517 patients, respectively. Median follow-up was 1,361 days with 90% follow-up rate at 2 years. The propensity score-matched cohort of 582 patients (n = 291 in each group) was developed as the main analysis set for the current report. RESULTS: Baseline characteristics of the propensity score-matched cohort were largely comparable, except for the slightly younger age and the greater AS severity in the initial AVR group. In the conservative group, AVR was performed in 41% of patients during follow-up. The cumulative 5-year incidences of all-cause death and heart failure hospitalization were significantly lower in the initial AVR group than in the conservative group (15.4% vs. 26.4%, p = 0.009; 3.8% vs. 19.9%, p < 0.001, respectively). CONCLUSIONS: The long-term outcome of asymptomatic patients with severe AS was dismal when managed conservatively in this real-world analysis and might be substantially improved by an initial AVR strategy. (Contemporary Outcomes After Surgery and Medical Treatment in Patients With Severe Aortic Stenosis Registry; UMIN000012140).