Background:Acute decompensated heart failure (ADHF) causes multi-organ damage associated with congestion, hypoperfusion, or both. However, its impact on pancreatic exocrine function (PEF), which can be associated with impaired digestion and absorption and contribute to malnutrition, remains unclear. Thus, in this proof-of-concept study, we investigated whether hospitalized patients with ADHF have impaired PEF. Methods and Results:Patients admitted to the cardiac intensive care unit were enrolled. Following initial stabilization, the N-benzoyl-L-tyrosyl-p-aminobenzoic acid (BT-PABA) test, which is the only clinically available PEF test in Japan, was performed. Data from 51 patients (age 73.3±9.8 years; 80.4% men; body mass index 23.9±5.0 kg/m2) were assessed. Patients hospitalized for ADHF (n=33) exhibited significantly lower levels of urinary PABA excretion rate (i.e., pancreatic function diagnostic [PFD] value) than in those hospitalized for other cardiovascular conditions (52.4±20.1% vs. 66.4±17.3%; P=0.022). Simple regression analyses revealed that decreased PFD values were associated with advanced age, increased hemoglobin A1c level, impaired kidney function, low urinary volume in the BT-PABA test, and ADHF-related hospitalization. Multiple regression analysis revealed that only reduced estimated glomerular filtration rate (coefficient 0.319; P=0.031) and ADHF-related hospitalization (coefficient -0.326; P=0.027) were associated with poor PFD values. Conclusions:PEF was impaired in hospitalized patients with ADHF. Our findings could inform further hypotheses regarding how improved PEF in hospitalized patients with ADHF affects their nutritional status.

BACKGROUND:Cheyne-Stokes respiration (CSR) is a major form of central sleep apnea in patients with heart failure and is associated with mortality in these patients. Although full polysomnography is required for CSR diagnosis, access may be limited. Cyclic variation of heart rate (CVHR) detected by Holter electrocardiogram reflects changes in cardiac autonomic activity associated with apnea-hypopnea events and is easier to perform than polysomnography. METHODS:We examined whether RR interval shortening time in the CVHR analysis could be useful for screening CSR. In this study, 41 patients were analyzed. Holter electrocardiogram and polysomnography were simultaneously performed. CVHR events were classified as CSR or not based on RR interval shortening time, and the percentage of CSR (%CSR), defined as the ratio of total CSR duration to time in bed, was measured. RESULTS:There were 27 patients with heart failure. The patients tended to have severe sleep-disordered breathing and an apnea-hypopnea index of 38.9 (24.7), and seven patients had predominantly central events. Based on %CSR determined by polysomnography with manual scoring ≧20%, 10 patients were labeled as CSR-positive and 31 as CSR-negative. There was moderate-to-good reliability between the percentage of CSR determined via CVHR analysis and the percentage of CSR determined via polysomnography [intraclass correlation coefficient = 0.74 (0.56, 0.85); p < 0.001]. CONCLUSIONS:Holter electrocardiograms are performed for many patients with heart failure and are better tolerated than overnight polysomnography. Our method of using CVHR detected by Holter electrocardiogram could be helpful for CSR screening.

Obstructive sleep apnea (OSA) is closely associated with obesity and fluid retention. Our previous study suggested that, in patients with heart failure, the sodium-glucose cotransporter 2 inhibitor, tofogliflozin, promotes diuresis and weight loss and improves OSA severity. However, whether changes in the apnea-hypopnea index (AHI) are chronologically associated with body composition parameters remains unclear. We enrolled 10 patients (six men) with OSA. They received tofogliflozin (20 mg) daily for 6 months. The AHI was assessed using WatchPAT® at baseline, 3, and 6 months. Body composition, including water content and fat mass, was also measured. AHI changes measured using the WatchPAT peripheral arterial tonometry-derived AHI (pAHI) and their correlations with changes in body composition parameters were analyzed. Tofogliflozin administration significantly reduced pAHIs at 3 and 6 months compared to baseline, but more at 3 months, whereas body weight and body water content decreased over time. The

Background:Bleeding risk is a concern in patients with atrial fibrillation (AF) on oral anticoagulants (OACs). The DOAC score, a novel bleeding risk score, was developed for patients on direct OACs (DOACs), but its applicability to all anticoagulated patients remains unclear. The aim of this study was to validate the DOAC score in patients with AF who received any OACs. Methods and Results:We analyzed data for 6,505 patients with nonvalvular AF receiving OACs from 2 Japanese multicenter registries (RAFFINE, SAKURA-AF; mean age 72±9 years; 28.1% female). Major bleeding occurred in 76 patients within 1 year. The DOAC score was compared to the HAS-BLED score in discrimination ability. The DOAC score showed higher area under the curve (AUC), although the difference was not statistically significant (AUC 0.653 vs. 0.601, P=0.23). The DOAC score also showed a trend towards improved net reclassification over the HAS-BLED score (net reclassification improvement (NRI): 25.4%, P=0.073). In patients without a prior history of major bleeding, the DOAC score offered a significant improvement in the NRI (30.9%, P=0.030). Conclusions:The DOAC score demonstrated moderate performance for predicting major bleeding in anticoagulated patients with AF. Although it did not significantly outperform the HAS-BLED score in this study, its applicability to both DOAC and warfarin users may offer a practical, unified approach.

Background/Objectives: Worsening renal function (WRF) during hospitalization for acute decompensated heart failure (ADHF) is associated with poor clinical outcomes. Data on the impact of WRF on clinical outcomes, considering blood urea nitrogen (BUN) level and its changes in patients with ADHF, are scarce. This study aimed to investigate the effects of BUN and its changes during hospitalization on the relationship between WRF during hospitalization and post-discharge clinical outcomes in patients with ADHF. Methods: A total of 509 patients with ADHF, hospitalized between 2007 and 2011, were included. WRF was defined as an absolute increase in serum creatinine level of >0.3 mg/dL, with a >25% increase during hospitalization. The risk of WRF for post-discharge clinical events, including death and rehospitalization, considering BUN levels, was assessed using three multivariable Cox regression models. Results: WRF was observed in 55 (10.8%) patients. The cumulative event-free survival was significantly worse in patients with WRF (p = 0.039). In Model 1 (excluding BUN changes), WRF was associated with a greater risk of post-discharge clinical events. In Model 2, which included both WRF and BUN changes, WRF was not a significant predictor. In Model 3, patients were subdivided according to WRF or BUN increase, and the subgroups were included instead of isolated WRF and BUN changes; only WRF with increased BUN level was associated with an increased risk of post-discharge clinical events. Conclusions: In patients with ADHF, WRF was associated with poor post-discharge clinical outcomes when accompanied by increased BUN levels during hospitalization.

Background: Limited data are available regarding the prevalence of sleep-disordered breathing (SDB), particularly Cheyne–Stokes respiration (CSR), in patients with atrial fibrillation (AF) and left ventricular (LV) systolic dysfunction. Thus, this study aimed to investigate the prevalence of SDB and CSR, as well as the factors associated with these conditions, in patients with AF without LV systolic dysfunction. Methods: Patients with paroxysmal and non-paroxysmal AF underwent echocardiography and cardiorespiratory polygraphy. Multiple linear regression analysis was performed using the apnea–hypopnea index (AHI) and %CSR as the dependent variables. Results: A total of 462 patients were enrolled; 335 patients (72.5%) were diagnosed with SDB (AHI ≥5/h), with a median AHI of 10.3 events per hour (interquartile range, 4.7–20.8). CSR was observed in 107 patients (23.2%). Multiple linear regression analysis showed that age, sex, body mass index, and hypertension were independently correlated with AHI (p = 0.0188, 0.0002, <0.0001, and 0.0457, respectively). Conversely, age, diabetes mellitus (DM), and the plasma N-terminal prohormone of brain natriuretic peptide (NT-proBNP) level were independently correlated with %CSR (p < 0.0001, 0.0047, and 0.0095, respectively). Conclusion: SDB and CSR were common in patients with AF. CSR was observed in older patients with DM and high NT-proBNP levels.

BACKGROUND:Patients with bradyarrhythmia requiring pacemaker implantation often report disrupted sleep, which could be related to bradyarrhythmia, apprehension of having heart disease and undiagnosed sleep disorders, resulting in impaired quality of life (QOL). We aimed to assess the prevalence of poor subjective sleep quality in patients with bradyarrhythmia requiring pacemaker implantation and its effect on sleep quality. METHODS AND RESULTS:Patients undergoing permanent pacemaker implantation for bradyarrhythmia were evaluated for subjective sleep quality and health-related QOL using the Pittsburgh Sleep Quality Index (PSQI) and Short Form-8 (SF-8) before and after pacemaker implantation. Poor subjective sleep quality was defined as PSQI score ≥6. Of 89 enrolled patients, 54 (60.7%) reported poor subjective sleep quality. A greater PSQI score indicative of poor sleep quality was likely to be observed in patients who had greater left ventricular ejection fraction and were treated with calcium-channel blockers, as well as in patients with more frequent sleep disturbance-related complaints/symptoms. After pacemaker implantation, the PSQI score improved significantly (from a median score of 6.0 to 5.0; P=0.015) proportional to an improvement in the mental component summary score. CONCLUSIONS:Poor subjective sleep quality is common among patients with bradyarrhythmia, contributing to impaired QOL. Pacemaker implantation may have a favorable effect on subjective sleep quality, and QOL for such patients.

Purpose:Home sleep apnea tests (HSATs) using polygraphy devices are becoming increasingly important for evaluating obstructive sleep apnea. Alice NightOne, a widely used polygraphy device, includes automatic scoring software; however, more reliable scoring results can be provided by incorporating advanced algorithmic systems like Somnolyzer. Despite this, the accuracy of automatic scoring of this polygraphy device using such applications has not been specifically investigated. Thus, in this study, we aimed to compare the respiratory event indices (REIs) obtained via automatic scoring versus manual scoring. Patients and Methods:Data of eligible patients who underwent HSAT with this polygraphy device were retrospectively analyzed using the following three methods: 1) manual scoring; 2) default automatic scoring of the analysis software; and 3) automatic scoring with the Somnolyzer system. The REIs were calculated using these three methods and expressed as mREI, aREI, and sREI, respectively. Correlations and agreements between the aREI, sREI, and mREI were assessed. Results:Data from 20 patients were analyzed. The mean mREI, aREI, and sREI were 14.7±13.3, 13.7±11.8, and 14.3±13.4 events/h, respectively. A strong correlation was found between aREI and mREI (coefficient, 0.976; P<0.01), with a mean difference between them of 1.0 and a limit of agreement of -5.3 to 7.3. The correlation between sREI and mREI was more prominent (coefficient, 0.996; P<0.001); their mean difference was 0.1, with a limit of agreement of -2.1 to 2.9. Conclusion:Automatic scoring of REI using this polygraphy device showed good correlation and agreement with manual scoring. The favorable correlation and agreement were more pronounced with the Somnolyzer system.

Background/Objectives: Heart failure (HF) can damage organs because of poor perfusion and/or congestion. The interactions between HF and other organs have recently been studied; however, data on the interaction between HF and pancreatic exocrine function, which may affect fat and protein absorption and malnutrition, are scarce. We previously showed that the serum levels of pancreatic exocrine enzymes, as suggestive of pancreatic exocrine function, were low and associated with malnutrition or congestion in hospitalized patients with acute decompensated HF (ADHF). This study investigated the relationship between the serum levels of pancreatic exocrine enzymes and long-term outcomes in patients with ADHF. Methods: We collected serum levels of pancreatic exocrine enzymes (amylase and lipase) from patients who were admitted to the cardiac intensive care unit due to ADHF. Patients undergoing dialysis and those with neoplasms were excluded. Patients were categorized as having high or low pancreatic exocrine enzyme levels in the first quartile upon admission. The association between low serum pancreatic exocrine enzyme levels at admission and the composite of death and ADHF readmission was assessed. Results: Of the 146 patients, 37 (25.3%) and 36 (24.7%) had low amylase and lipase levels, respectively. Patients with low lipase levels showed worse cumulative event-free survival than those with high lipase levels (p < 0.001). A low lipase level was associated with worse outcomes (hazard ratio: 1.96; p = 0.012). Conclusions: These findings suggest that low serum lipase levels may be a predictor of long-term outcomes in patients with ADHF.

Background:Cardiac acoustic biomarkers (CABs) measured by acoustic cardiography support the diagnosis or monitoring of worsening heart failure (HF). Our previous observational study suggested that temporal changes in CABs in patients with acute decompensated HF may reflect changes in cardiac function during hospitalization and between discharge and the first follow-up visit. This study aimed to assess whether changes in CABs between discharge and the first follow-up visit in such patients are associated with cardiac events over a 1-year follow-up period. Methods:This study was a follow-up to our previous observational study. CABs assessed at discharge and the first clinic visit following discharge were examined. The incidence of cardiac events, defined as the composite of death and rehospitalization due to worsening HF following the first clinic visit, was investigated. Results:Among 60 patients enrolled in our previous study, 47 who had CAB data at discharge and their first clinic visit were monitored for 1 year. During a median follow-up period of 351 days, 17 of these 47 patients experienced cardiac events, including 4 deaths and 13 rehospitalizations. The cumulative event-free survival rate was significantly poorer in patients whose change in third heart sound (ΔS3) strength was ≥ 0.1 than in those whose ΔS3 strength was < 0.1. Multivariate Cox regression models indicated that the ΔS3 strength increase was significantly associated with increased risk of cardiac events. Conclusions:An increase in S3 as assessed using the CAB device between discharge and the first clinic visit may be a predictor of subsequent cardiac events in patients initially hospitalized for acute decompensated HF.

Background:Interactions between the heart and other organs have been a focus in acute decompensated heart failure (ADHF). However, the association between ADHF and pancreatic exocrine insufficiency (PEI), which may lead to malnutrition, remains unclear. We investigated the relationship between exocrine pancreatic enzymes and ADHF. Methods:We enrolled 155 and 46 patients with and without ADHF, respectively. Serum amylase and lipase levels were compared between the two groups. In the ADHF group, factors correlating with serum amylase or lipase levels were assessed using multiple regression analysis, and changes in their levels throughout the hospital course were determined. Results:Patients with ADHF exhibited significantly lower amylase and lipase levels. In the same group, the significant independent correlates of lower amylase levels included a lower blood urea-nitrogen level (partial correlation coefficient, 0.530; p < 0.001), lower albumin level (partial correlation coefficient, 0.252; p = 0.015), and higher uric acid level (partial correlation coefficient, -0.371; p < 0.001). The significant independent correlates of lower lipase levels included coexisting atrial fibrillation (coefficient, 0.287; p = 0.026), lower creatinine level (coefficient, 0.236; p = 0.042), and higher B-type natriuretic peptide level (coefficient, -0.257; p = 0.013). Both amylase and lipase levels significantly increased following the improvement in ADHF. Conclusions:In patients with ADHF, decreased serum amylase and lipase levels were associated with the congestion severity, suggesting that PEI may occur in patients with ADHF, potentially due to ADHF-related congestion.

Background and aimsSuccessful left atrial posterior wall isolation (LAPWI) using only the cryoballoon (CB) is technically challenging for the treatment of atrial fibrillation (AF). This study aimed to evaluate the efficacy of the cross-over technique, wherein an overlapped ablation is performed by placing the CB from both directions in contact with the LAPW.MethodsThis was a single-center, retrospective, observational study of 194 consecutive patients with persistent atrial fibrillation (PerAF) who underwent a first-time procedure of pulmonary vein isolation (PVI) + PWI (108 patients) or PVI-only (86 patients) using the CB. The cross-over technique was applied in all LAPWI.ResultsFor ablation of the LA roof and bottom, respectively, a mean of 8.6 +/- 1.0 (right to left [R -> L] 4.3 +/- 1.1 and left to right [L -> R] 4.3 +/- 1.1) and 9.1 +/- 1.2 (R -> L 4.6 +/- 1.6 and L -> R 4.5 +/- 1.2) CB applications were delivered. LAPW was successfully isolated solely using the CB in 99.1% of patients. Although the PVI + PWI group had significantly longer procedure time, no severe adverse events were observed in either group. During a median follow-up of 19 months, freedom from recurrence of all atrial tachyarrhythmias was achieved in 93.5% of the PVI + PWI group and 72.9% of the PVI-only group (p = .011).ConclusionsLAPWI performed solely with the CB using the cross-over technique is feasibly, safe, and was independently associated with a significantly higher freedom from recurrence of atrial tachyarrhythmias compared with PVI alone in patients with PerAF.

Sleep apnea (SA) is prevalent among patients with heart failure (HF) and contributes to a poor prognosis. Sodium–glucose cotransporter 2 (SGLT2) inhibitors have demonstrated efficacy in reducing the risk of serious clinical events in patients with HF. Additionally, SGLT2 inhibitors may reduce the risk of incident SA and mitigate its severity in patients with cardiovascular disease and T2DM. We aimed to investigate whether the SGLT2 inhibitor tofogliflozin reduced the severity of SA, as assessed using the apnea–hypopnea index (AHI), in patients with HF and T2DM and whether a decrease in AHI correlates with changes in body composition and cardiorenal function parameters. This is a single-arm, prospective pathophysiologic study involving patients with HF, T2DM, and SA, defined as having an AHI of 15 events/h and more. SA was assessed using polysomnography. Changes in AHI before and 6 months after starting oral administration of tofogliflozin (20 mg) were assessed. Additionally, body composition and cardiorenal functions were assessed before and 6 months after tofogliflozin administration. Ten patients with HF, T2DM, and SA were finally enrolled (60

Background: Sleep disordered breathing (SDB) is known as a common comorbidity in patients with atrial fibrillation (AF). Indeed, patients undergoing pulmonary vein isolation (PVI) for AF had a high prevalence of SDB in particular, Cheyne-Stokes respiration (CSR). The aim of the present study is to assess the correlates of SDB severity and CSR in AF patients undergoing PVI. Methods and Results: The study was conducted under a single-center, observational design. We enrolled 140 consecutive patients undergoing PVI. All participants underwent home sleep apnea test (ApneaLink Air, ResMed, Australia) which could determine the severity of SDB as assessed by apnea-hypopnea index (AHI) and the percent of CSR (%CSR) pattern. Overall, 33 (27.9%) patients was no SDB (AHI<5), 53 (37.9%) patients was mild SDB (5≦AHI<15), 33 (23.6%) patients was moderate SDB (15≦AHI<30), and 15 (10.7%) patients was severe SDB(30≦AHI). Correlates of the increased AHI includes male sex (β=0.27, p=0.001), high age (β=0.19, p=0.0028), high body mass index (BMI) (β=0.29, p=0.0013), hypertension (β=0.18, p=0.038), and non-paroxysmal AF (β=0.17, p=0.047). On the other hand, correlates to %CSR rate includes male sex (β=0.17, p=0.026), high age (β=0.22, p=0.0054), non-paroxysmal AF (β=0.27, p=0.0005), high value of HbA1c (β=0.3, p<0.0001), and greater N-terminal fragment of the Brain natriuretic peptide (NT-proBNP) (β=0.26, p=0.0007). Conclusion: Increased SDB severity correlated with male sex, high age, obesity, hypertension and chronicity of AF in patients with PVI. Correlates the percent of %CSR were male sex, high age, the chronicity of AF, high value of HbA1c, and greater NT-proBNP. Treatment for SDB should be consider for these AF patients, because SDB increases the recurrence ratio of AF after PVI.

Serum uric acid (UA) level is associated with the high cumulative incidence or prevalence of coronary artery disease (CAD), and hyperuricemia is considered as an independent risk marker for CAD. Sleep-disordered breathing (SDB) is also associated with an increased risk of CAD. Several studies have shown that SDB is associated with hyperuricemia, but the mechanisms are unclear. We measured serum levels of UA and xanthine oxidoreductase (XOR) activity and urinary levels of 8-hydroxy-2’-deoxyguanosine (8-OHdG), all of which were assessed at 6 p.m. and the following 6 a.m. in males with CAD. In addition, nocturnal pulse oximetry was performed for the night. Overall 32 eligible patients with CAD were enrolled. Serum UA levels significantly increased overnight. (5.32 ± 0.98 mg/dl to 5.46 ± 1.02 mg/dl, p < 0.001) Moreover, XOR activity and urinary 8-OHdG levels significantly increased from 6 p.m. to 6 a.m. Furthermore, 3% Oxygen desaturation index (ODI) was correlated with the overnight changes in XOR activity (r = 0.36, P = 0.047) and urinary 8-OHdG levels (r = 0.41, P = 0.02). In addition, 3%ODI was independently correlated with the changes in XOR activity (correlation coefficient, 0.36; P = 0.047) and 8-OHdG (partial correlation coefficient, 0.63; P = 0.004) in multivariable analyses. SDB severity was associated with the overnight changes in XOR activity and urinary 8-OHdG, suggesting that SDB may be associated with oxidative stress via UA production. This trial is registered at University Hospital Medical Information Network (UMIN), number: UMIN000021624.

Hyperuricemia is influenced by diet and can cause gout. Whether it is a potential risk factor for cardiovascular disease (CVD) remains controversial, and the mechanism is unclear. Similar to CVDs, gout attacks occur more frequently in the morning and at night. A possible reason for this is the diurnal variation in uric acid (UA), However, scientific data regarding this variation in patients with CVD are not available. Thus, we aimed to investigate diurnal variations in serum levels of UA and plasma levels of xanthine, hypoxanthine, and xanthine oxidoreductase (XOR) activity, which were measured at 18:00, 6:00, and 12:00 in male patients with coronary artery disease. Thirty eligible patients participated in the study. UA and xanthine levels significantly increased from 18:00 to 6:00 but significantly decreased from 6:00 to 12:00. By contrast, XOR activity significantly increased both from 18:00 to 6:00 and 6:00 to 12:00. Furthermore, the rates of increase in UA and xanthine levels from night to morning were significantly and positively correlated. In conclusion, UA and xanthine showed similar diurnal variations, whereas XOR activity showed different diurnal variations. The morning UA surge could be due to UA production. The mechanism involved XOR activity, but other factors were also considered.

Overnight increases in arterial stiffness associated with sleep-disordered breathing may adversely affect patients with acute heart failure. Thus, we investigated overnight changes in arterial stiffness and their association with sleep-disordered breathing in patients hospitalized for acute heart failure. Consecutive patients with acute heart failure were enrolled. All participants underwent overnight full polysomnography following the initial improvement of acute signs and symptoms of acute heart failure. The arterial stiffness parameter, cardio-ankle vascular index (CAVI), was assessed before and after polysomnography. Overall, 60 patients (86.7% men) were analyzed. CAVI significantly increased overnight (from 8.4 ± 1.6 at night to 9.1 ± 1.7 in the morning, P < 0.001) in addition to systolic and diastolic blood pressure (from 114.1 mmHg to 121.6 mmHg, P < 0.001; and from 70.1 mmHg to 78.2 mmHg, P < 0.001, respectively). Overnight increase in CAVI (ΔCAVI ≥ 0) was observed in 42 patients (70%). The ΔCAVI ≥ 0 group was likely to have moderate-to-severe sleep-disordered breathing (i.e., apnea-hypopnea index ≥15, 55.6% vs 80.9%, P = 0.047) and greater obstructive respiratory events (29.4% vs 58.5%, P = 0.041). In multivariable analysis, moderate-to-severe sleep-disordered breathing and greater obstructive respiratory events were independently correlated with an overnight increase in CAVI ( P = 0.033 and P = 0.042, respectively). In patients hospitalized for acute heart failure, arterial stiffness, as assessed by CAVI, significantly increased overnight. Moderate-to-severe sleep-disordered breathing and obstructive respiratory events may play an important role in the overnight increase in cardio-ankle vascular index.

Editorial comment to “Sleep apnea severity in patients undergoing atrial fibrillation ablation: Home sleep apnea-test and polysomnography comparison.”.1 Sleep apnea (SA) is associated with an increased incidence of cardiovascular diseases such as hypertension, coronary heart disease, heart failure and atrial fibrillation (AF). This indicates a possible cause-and-effect relationship between them. In general, SA is classified as obstructive or central based on respiratory effort. In patients with obstructive SA (OSA), repetitive upper airway obstruction during sleep leads to intermittent nocturnal hypoxemia, hypercapnia, overactivation of the sympathetic nervous system, enhanced oxidative stress and inflammation. These factors contribute to atrial remodeling and fibrosis, predisposing patients to an increased risk of AF. Catheter ablation (CA) is an effective treatment for AF; however, its relatively high recurrence rate remains an important issue. Although the recurrence rate of AF after CA is significantly higher in patients with OSA than in those without, optimal CPAP therapy is associated with a reduction in AF recurrence rates after CA. A meta-analysis of nine prospective cohort studies including 2,134 participants indicated that CPAP is associated with a 37% relative risk reduction in AF recurrence among OSA patients under rhythm-control strategies.2 Therefore, diagnosing and treating SA are important for patients with AF undergoing CA. The Centers for Medicare & Medicaid Services (CMS) in the United States defines the indications of CPAP for OSA as an apnea-hypopnea index (AHI) ≥15 or an AHI ≥5 with documented symptoms of excessive daytime sleepiness, impaired cognition, mood disorders or insomnia, or documented cardiovascular diseases.3 Notably, for the indication of CPAP in CMS, the AHI values measured using the home sleep apnea test (HSAT) can be considered equivalent to those measured using polysomnography (PSG), although the HSAT mentioned here is not the same as the devices used in Japan for HSAT. On the other hand, the current Japanese health insurance system defines CPAP indications as an AHI ≥20 assessed using PSG or an AHI ≥40 assessed using HSAT.4 Therefore, AF patients with an AHI <40 as indicated by HSAT must undergo additional PSG to determine CPAP indications. PSG is the standard diagnostic tool for SA; however, many patients suspected to have SA may not be able to undergo this test because of its high cost, limited access and long waiting times. Additionally, patients may be unwilling to undergo PSG without objective data suggesting pathological OSA. Patients with AF and OSA are less likely to complain of excessive daytime sleepiness, which is an important symptom indicating the need for treatment. Therefore, objective data suggestive of pathological OSA are important, particularly in patients with AF. The advantages of HSAT over PSG in terms of cost-effectiveness have already been reported. Kawakami et al. reported the cost-effectiveness of facilitating OSA screening using HSAT before CA in AF patients.5 In their study, the incremental cost-effectiveness ratio of the Japanese health insurance system was compared among patients without screening, those with HSAT-guided screening and those with PSG-guided screening. HSAT-guided screening was most cost-effective at a willingness-to-pay threshold of JPY 5,000,000. However, few studies have investigated the validity of OSA severity derived using HSAT against that derived using PSG among patients with AF. In this issue of the Journal, Tanaka et al.1 provided valuable insights into the correlation between the AHI derived using HSAT and that obtained using PSG in patients with AF. Prior to CA, they performed HSAT using a peripheral arterial tonometry (PAT)-based device (Watch-PAT200U [WP]; Itamar Medical Ltd.). WP devices were sent to the patients' homes, where the patients self-administered the devices and returned them with a filled screening questionnaire. Afterward, they were admitted for CA. PSG was performed under stable postoperative conditions at least 1 day after CA. A significant correlation was observed between WP-AHI and PSG-AHI (r = 0.48, p < 0.001), and the best cut-off value of the WP-AHI predicting PSG-AHI ≥20 (indications for CPAP as per the Japanese health insurance system), was almost identical to PSH-AHI (i.e., 18.1). According to the results, patients deemed eligible for CPAP treatment by PSG (i.e., PSG-AHI ≥20) were 70.9%, whereas patients deemed eligible for CPAP treatment by HSAT (i.e., WP-AHI ≥40) were only 12.5%. This indicates that many patients who need to be treated with CPAP miss the indication if they do not undergo PSG. Several limitations, some of which have been acknowledged by the authors themselves, should be considered when interpreting the study results. First, WP and PSG were not performed simultaneously; WP was performed before CA, and PSG was performed after CA. Therefore, CA may have influenced PSG-AHI and caused some differences between WP-AHI and PSG-AHI. Second, the PAT-based device indirectly detects apnea and hypopnea by selectively measuring peripheral arterial volume changes using a finger-mounted plethysmogram. In patients with AF, irregular heartbeats may influence beat-to-beat changes in the peripheral arterial volume. Therefore, it is unclear whether these findings apply to other HSAT devices. Nevertheless, the findings of the study by Tanaka et al. provide valuable information for cardiologists which will help them consider whether to initiate CPAP or perform PSG prior to or soon after CA in patients with a WP-AHI ≥20. Ideally, the CPAP indication for patients with AF undergoing CA under the Japanese health insurance system is the same as that in CMS (i.e., the AHI values measured using HSAT can be treated as if they were measured using PSG). If so, more patients with AF with moderate-to-severe OSA will be treated with CPAP, AF recurrence in such patients will decrease and burden of healthcare costs may be minimized. This study was supported by JSPS KAKENHI (grant numbers: JP17K09527, JP18K15904, JP21K08116 and JP21K16034), a grant to The Intractable Respiratory Diseases and Pulmonary Hypertension Research Group from the Ministry of Health, Labor and Welfare (20FC1027) and a research grant from the Japanese Center for Research on Women in Sport, Juntendo University. These funding sources did not play any other role in this study. Drs. Akihiro Sato and Takatoshi Kasai are affiliated with a department endowed by Philips Japan, ResMed and Fukuda Denshi. The authors have no conflicts of interest to declare.