Methods

One hundred fifty consecutive outpatients with systolic HF were enrolled into the current study after obtaining informed consent in 2 participating centers. Left ventricular ejection fraction (LVEF) was <40% on echocardiogram in all patients. Patients with creatinine clearance <60%, recent exacerbation within 1 month, long-term alcoholism, sepsis, pancreatitis, primary hyperparathyroidism, cancer, severe hepatic disease, and those taking spironolactone were excluded.

Blood samples were collected for intact PTH and brain natriuretic peptide (BNP) measurements. Serum intact PTH levels were obtained at an outpatient clinic using an Immulite intact PTH assay (Diagnostics Product Corporation, 2000, Los Angeles, California). The established normal range for this assay was 10 to 65 pg/ml.

Patients were classified into 4 groups based on New York Heart Association (NYHA) functional class. Consensus of 2 experienced clinicians blinded to each other was required for classification of functional classes. In case of disagreement, a third opinion was obtained from an expert physician. Anemia was defined as hemoglobin levels <13 g/dl in men and <12 g/dl in women in accordance with World Health Organization criteria. Hypertension was defined as blood pressure >140/90 mm Hg on >2 occasions during office measurements or during antihypertensive treatment. Diabetes mellitus was defined as fasting blood glucose ≥126 mg/dl or use of antidiabetic treatment. Hyperlipidemia was defined as serum low-density lipoprotein cholesterol >160 mg/dl or total cholesterol >240 mg/dl or triglyceride >200 mg/dl or high-density lipoprotein cholesterol <40 mg/dl or use of lipid-lowering drugs. Coronary artery disease was recorded as present if there was a clinical history of coronary artery disease, abnormal stress test results with evidence of ischemia, or documented coronary stenosis >50%. Those who continued smoking during the index admission were considered current smokers. Rhythm, medications, and hemodynamic findings such as heart rate and systolic and diastolic blood pressures were evaluated.

According to protocol, all participating centers were advised to perform transthoracic echocardiography at admission. Echocardiographic examinations were performed with the Vivid 7 system (GE Healthcare, Wauwatosa, Wisconsin) with 2.5- to 5-MHz probes in all participating centers. LVEF was calculated by the modified Simpson method. Chamber sizes were defined according to recent guidelines. Systolic pulmonary artery pressure was estimated from the tricuspid regurgitant velocity profile using the modified Bernoulli equation. Digital records of transthoracic echocardiographic examinations without recorded identities were sent to the main center and evaluated offline by an expert sonographer blinded to the study plan. The study was performed in accordance with the Declaration of Helsinki for human research and was approved by the institutional review board.

Parametric data were expressed as mean ± SD and categorical data as percentages. SPSS 16.0 (SPSS, Inc., Chicago, Illinois) was used to perform statistical procedures. Receiver operator characteristic curve analysis was performed to identify the optimal cut-off point of PTH (at which sensitivity and specificity would be maximal) for the prediction of advanced HF. Areas under the curve were calculated as measurements of the accuracy of the tests. We compared areas under the curve using the Z test. Comparisons between groups were performed using 1-way analysis of variance and Kruskal–Wallis tests for normally and abnormally distributed data, respectively. Categorical variables between groups were analyzed using chi-square test. Correlation was evaluated by the Pearson correlation test or Spearman correlation test. We used univariate analysis to quantify the association of variables with advanced HF. Variables found to be statistically significant in univariate analysis were used in a multivariate logistic regression model with forward stepwise method to determine the independent predictors of advanced HF. A p value of 0.05 was considered statistically significant.

Results

Considering the entire cohort, mean age of patients was 66 ± 10 years (69% men, 31% women). Mean LVEF was 27 ± 9% and mean PTH level was 101 ± 63 pg/ml. Advanced HF (NYHA functional class IV) was observed in 30 patients (20%).

A comparison of the 4 groups of patients with HF is presented in Table 1 . Body mass index, disease duration, PTH, BNP, creatinine clearance, hemoglobin levels, diuretic usage, LVEF, LV diastolic diameter, and left atrial size differed significantly in relation to NYHA functional class ( Table 1 ). Mean levels of PTH increased as NYHA functional class increased ( Figure 1 , Table 1 ).

Comparison of parathyroid hormone levels among 4 groups.

In patients with HF, serum intact PTH levels were correlated with BNP level, LVEF, heart rate, creatinine clearance, left atrial size, LV diastolic diameter, diuretic usage, presence of atrial fibrillation, and hemoglobin level ( Table 2 ).

Univariate and multivariate logistic regression analyses for identifying advanced HF are presented in Table 3 . Disease duration, body mass index, PTH, BNP and hemoglobin levels, creatinine clearance, heart rate, systolic blood pressure, LVEF, LV diastolic diameter, left atrial size, presence of atrial fibrillation, and diuretic usage were found to designate advanced HF. In multivariate logistic regression analysis, PTH level and body mass index were associated with advanced HF ( Table 3 ).

Table 3

Univariate and multivariate predictors of advanced heart failure

Variable	Univariate			Multivariate
	HR	95% CI	p Value	HR	95% CI	p Value
Body mass index	0.695	0.569–0.848	<0.001	0.542	0.273–1.075	0.079
Disease duration	1.015	1.004–1.026	0.010
Parathyroid hormone	1.010	1.006–1.015	<0.001	1.032	1.003–1.062	0.030
Brain natriuretic peptide	1.000	1.000–1.001	0.001
Creatinine clearance	0.935	0.893–0.978	0.004
Hemoglobin	0.757	0.567–1.011	0.059
Heart rate	1.028	1.010–1.046	0.003
Systolic blood pressure	0.971	0.951–0.990	0.004
Left ventricular ejection fraction	0.933	0.890–0.978	0.004
Left ventricular diastolic diameter	1.528	1.038–2.250	0.032
Left atrial size	2.670	1.299–5.489	0.008
Atrial fibrillation	3.344	1.419–7.883	0.006
Diuretic usage	3.273	0.929–11.533	0.065

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