Study Population: We retrospectively analyzed the data from the Prospective Multicenter Observational Study of Patients with Heart Failure with Preserved Ejection Fraction (PURSUIT-HFpEF), a multicenter, observational study enrolling consecutive patients hospitalized with acute decompensated HFpEF (left ventricular ejection fraction (LVEF) ≥ 50%) in 31 collaborating hospitals [UMIN-CTR ID: UMIN000021831][8]. Details of the entry criteria and data collection have been described elsewhere. Briefly, patients admitted with acutely decompensated HFpEF were registered, and their clinical data, including medications, laboratory tests, and ECG, were collected on admission, at discharge, and 1 year after discharge. Acutely decompensated HFpEF was diagnosed based on the following criteria: (1) clinical symptoms and signs according to the Framingham Heart Study criteria, (2) LVEF on admission ≥ 50%, and (3) serum N-terminal pro-B type natriuretic peptide (NT-proBNP) ≥ 400 pg/mL or brain natriuretic peptide ≥ 100 pg/mL. T2DM was diagnosed based on clinical history or on fasting plasma glucose and/or hemoglobin A1c (HbA1c) during hospitalization based on the Japanese Clinical Practice Guideline for Diabetes 2019[9]. Oral glucose tolerance testing was not mandatory for the present study.
This study was conducted in accordance with the Declaration of Helsinki. The study protocol was approved by each corresponding hospital’s Ethics Committee. Informed consent was obtained from each patient by one of the investigators before the study.
Data Collection
We collected patient data, including risk factors and history of major comorbidities such as DM, hypertension, dyslipidemia, smoking, chronic kidney disease (CKD), history of HF hospitalization, prior myocardial infarction, prior stroke and malignancy, and history of percutaneous coronary intervention or coronary artery bypass graft (CABG). Blood tests, standard 12-lead ECG recording, chest radiography, and echocardiography were performed immediately after admission, before discharge, and 1 year after discharge. LVEF was determined by either the Teichholz method or the modified Simpson’s technique on admission but only by Simpson’s technique at discharge and 1 year after discharge. Study patients were followed up by direct contact or telephone interview with patients to observe all-cause death, which was a primary endpoint of the PURSUIT-HFpEF registry[8]. For patients whose survival information could not be determined by these means, the data from National Vital Statistics of Japan, which includes all death records in Japan reported by prefectural public health centers, were used with the permission of the Ministry of Health, Labor and Welfare in accordance with the Statistics Act in Japan.
The WATCH-DM risk score and other heart failure risk scores: We calculated the WATCH-DM score as the sum of the scores obtained from the following factors[7]: age (0 to 6 points), body mass index (BMI, 0 to 5 points), systolic (0 to 3 points) and diastolic (0 to 2 points) blood pressure (BP), fasting plasma glucose (0 to 3 points), serum creatinine (0 to 5 points), high density lipoprotein cholesterol (HDL-c, 0 to 2 points), QRS width on ECG (0 or 3 points) and history of myocardial infarction (0 or 3 points) or CABG (0 or 2 points), all of which were measured or obtained at hospital discharge. The risk of HF in each patient was estimated as very low (≤ 7 points), low (8–9 points), average (10 points), high (11–13 points) and very high (≥ 14 points) (Table 1). Due to the limited number of patients, we combined patients with very low to average risk as the “average or lower” risk group.
Table 1
Age (years) | < 50 | 50–54 | 55–59 | 60–64 | 65–69 | 70–74 | ≥ 75 |
0 | 1 | 2 | 3 | 4 | 5 | 6 |
BMI (kg/m2) | < 25 | 25–34 | 35–39 | ≥ 40 | |
0 | 1 | 2 | 3 |
Systolic BP (mmHg) | < 100 | 100–139 | 140–159 | ≥ 160 | |
0 | 1 | 2 | 3 |
Diastolic BP (mmHg) | < 60 | 60–80 | ≥ 80 | |
2 | 1 | 0 |
FPG (mg/dL) | < 125 | 125–199 | 200–299 | ≥ 300 | |
0 | 1 | 2 | 3 |
HDL-c (mg/dL) | < 30 | 30–59 | ≥ 60 | |
2 | 1 | 0 |
Serum Cr (mg/dL) | < 1.0 | 1.0-1.49 | ≥ 1.50 | |
0 | 2 | 5 |
Ischemic events | Prior CABG | Prior MI | |
2 | 3 |
The WATCH-DM score was calculated as the sum of scores, which are shown in the bottom row corresponding to each factor.
BMI depicts body mass index; BP, blood pressure; FPG, fasting plasma glucose; HDL-C, high-density lipoprotein cholesterol; Cr, serum creatinine; CABG, coronary artery bypass grafting; MI, myocardial infarction.
To compare the ability of the WATCH-DM risk score to predict 1-year mortality with other HF risk scores, we calculated the Meta-Analysis Global Group in Chronic Heart Failure (MAGGIC) risk score[10] and the mortality risk using the Barcelona Bio-Heart Failure Risk (BCN Bio-HF) calculator[11]. We calculated the MAGGIC risk score as the sum of scores provided from the following factors: LVEF (0 point to all present patients with HFpEF), age (0 to 15 points), systolic BP (0 to 2 points), BMI (0 to 6 points), creatinine (0 to 8 points), New York Heart Association (NYHA) class (0 to 8 points), male sex (0 or 1 point), current smoker (0 or 1 point), DM (3 points for all preset patients), diagnosis of chronic obstructive pulmonary disease (0 or 2 points), first diagnosis of heart failure in the 18 months (0 or 2 points), not on beta blockers (0 or 3 points) and not on renin-angiotensin-aldosterone blockers (0 or 1 point)[10]. We estimated 1-year mortality by the web-based BCN Bio-HF calculator (http://ww2.bcnbiohfcalculator.org/web/, accessed at September and October 2021) using age, sex, NYHA class, LVEF, serum sodium, estimated glomerular filtration rate (eGFR), hemoglobin, loop diuretic dose, beta blocker, angiotensin converting enzyme inhibitor/angiotensin-2 receptor blocker, and statin treatments[11]. We did not include biomarkers for the present analysis because NT-proBNP was not measured in some patients, and cardiac troponin T or ST-2 was not measured at all.
Statistical Analysis
Continuous variables are expressed as the mean and standard deviation or median [the interquartile range (IQR)]. Categorical variables are expressed as absolute frequencies or relative percentages. We made comparisons by one-way ANOVA for continuous variables, and the significance of differences among groups was calculated with the Bonferroni correction. Categorical variables were compared with Fisher’s exact test. For the correlation between WATCH-DM score and continuous or ordinal values, Spearman's rank correlation coefficient was calculated. A Cox proportional hazard model for all-cause death was constructed including factors that showed significant differences (p < 0.05) among the 3 risk groups, although factors that were included by or highly related to the WATCH-DM score were not included. Event-free survival analysis was performed using the Kaplan‒Meier method with the log-rank test for group comparisons.
We constructed time-dependent receiver operating characteristic (ROC) curves of the risk scores for all-cause death at 1 year after hospitalization using the “time ROC” package (ver 0.4) for R. We compared the difference between the estimated area under the curves (AUC) of both risk scores for each time point, and the variance of the difference using the independent and identically distributed (iid) representation of the AUC estimators was used to obtain the p value of the comparison test. All statistical analyses were performed using R (version 4.1.1) or R with a graphical user interface EZR (Saitama Medical Centre, Jichi Medical University, Japan).