Results

Baseline demographic characteristics, cardiovascular risk factors, and anaemia prevalence of both groups are summarized in Table 1. The mean age of iron-deficient patients (Group I) was significantly higher than that of patients with normal iron status (Group II) (66.1 ± 8.66 years vs. 57.87 ± 8.16 years; p < 0.001). Female patients predominated in both groups, with 35 (58.3%) in Group I and 32 (53.3%) in Group II; however, this difference was not statistically significant (p=0.52). The prevalence of hypertension, diabetes mellitus, ischemic heart disease, and dyslipidaemia did not differ significantly between the two groups (all p>0.05). Anaemia was significantly more prevalent among iron-deficient patients, where 38 (63.3%) patients in Group I had anaemia compared with 11 (18.3%) patients in Group II (p<0.001).

Characteristic | Group I frequency (%) | Group II frequency (%) | Test statistic | df | Effect size | p value
Age (years)
Mean ± SD | 66.1 ± 8.66 | 57.87 ± 8.16 | t = 5.31 | 118 | Cohen’s d = 0.97 | < 0.001
Gender
Male | 25 (41.7) | 28 (46.7) | χ² = 0.42 | 1 | φ = 0.06 | 0.52
Female | 35 (58.3) | 32 (53.3)
Cardiovascular risk factors
Hypertension | 47 (78.3) | 49 (81.7) | χ² = 0.21 | 1 | φ = 0.04 | 0.648
Diabetes mellitus | 38 (63.3) | 31 (51.7) | χ² = 1.67 | 1 | φ = 0.12 | 0.196
Ischaemic heart disease | 23 (38.3) | 21 (35.0) | χ² = 0.14 | 1 | φ = 0.03 | 0.704
Dyslipidaemia | 19 (31.7) | 17 (28.3) | χ² = 0.16 | 1 | φ = 0.04 | 0.690
Anaemia status
Present | 38 (63.3) | 11 (18.3) | χ² = 25.30 | 1 | φ = 0.46 | < 0.001
Absent | 22 (36.7) | 49 (81.7)

Mean NT-proBNP concentration was significantly higher in iron-deficient patients (Group I: 3256.75 ± 1124.30 pg/mL) than in those with a normal iron status (Group II: 2099.07 ± 987.50 pg/mL; p < 0.001) (Table 2).

Variable | Group I Mean ± SD | Group II Mean ± SD | Test statistic | df | Effect size | p value
NT-proBNP (pg/mL) | 3256.75 ± 1124.30 | 2099.07 ± 987.50 | t = 5.99 | 118 | Cohen’s d = 1.09 | < 0.001

Iron deficiency was significantly associated with a higher NYHA functional class (p=0.003). Among Group I patients, 23 (38.3%) were classified as NYHA Class III and 4 (6.7%) as Class IV, indicating severe functional limitation. In contrast, 29 (48.3%) of Group II patients were in NYHA Class I, reflecting mild or absent symptomatic impairment. Diastolic dysfunction grading by transthoracic echocardiography, performed according to the 2016 ASE/EACVI recommendations, was significantly associated with iron deficiency (p=0.028). Grade 2 diastolic dysfunction was the most prevalent finding in Group I, with 29 (48.3%) patients, whereas Grade 1 was most common in Group II, with 38 (63.3%) patients. Grade 3 diastolic dysfunction was present in six (10.0%) of iron-deficient patients compared with only one (1.7%) of those with a normal iron status, indicating that more advanced diastolic dysfunction is significantly more frequent among iron-deficient HFpEF patients (Table 3).

Outcome | Group I frequency (%) | Group II frequency (%) | p value
NYHA functional class
Class I | 14 (23.3) | 29 (48.3) | 0.003
Class II | 19 (31.7) | 21 (35.0)
Class III | 23 (38.3) | 9 (15.0)
Class IV | 4 (6.7) | 1 (1.7)
Diastolic dysfunction grade
Grade 1 | 25 (41.7) | 38 (63.3) | 0.028
Grade 2 | 29 (48.3) | 21 (35.0)
Grade 3 | 6 (10.0) | 1 (1.7)