European Journal of Cardiovascular Medicine

Cardiovascular disease remains the leading cause of death worldwide, accounting for an estimated 17.9 million deaths annually, with acute coronary syndrome (ACS) contributing disproportionately to this burden in low- and middle-income countries.1 ST-elevation myocardial infarction (STEMI), the most acute and high-risk presentation of ACS, requires prompt risk stratification at admission to guide reperfusion strategy, monitoring intensity, and prediction of in-hospital complications.2 Even with widespread adoption of primary percutaneous coronary intervention (PCI), in-hospital mortality and morbidity remain considerable, particularly in resource-limited settings where delays in presentation and reperfusion are common.3 Timing of reperfusion remains a central determinant of outcome: prolonged door-to-balloon and total ischemic times have both been independently associated with higher in-hospital mortality in recent STEMI cohorts.4,5 Beyond procedural timing, several complications occurring during the index admission including acute kidney injury, cardiogenic shock, and acute left ventricular failure, substantially worsen prognosis and identifying patients at elevated risk for these complications at the time of admission remains an active area of investigation.6,7 Among the biochemical tools available for early risk stratification, biomarkers reflecting myocardial stress and metabolic derangement have drawn particular interest because they can be measured rapidly using routine laboratory assays. The triglyceride-glucose index, a surrogate marker of insulin resistance, has recently been shown to correlate with thrombus burden and mortality risk in STEMI patients undergoing primary PCI,8 illustrating the broader principle that simple, widely available laboratory parameters can meaningfully stratify risk in this population when validated in the relevant clinical context. Natriuretic peptide testing follows a similar logic: N-terminal pro-B-type natriuretic peptide (NT-proBNP) is released from the myocardium under conditions of wall stress and is among the most extensively studied biomarkers for cardiovascular risk stratification, with applications ranging from heart failure diagnosis to prognostication after acute coronary events. Outcomes after STEMI also vary considerably by geography and healthcare system. Mortality data from sub-Saharan Africa,9 South Asia,10 and Latin America11 have each demonstrated that regional differences in presentation delay, reperfusion access, and comorbidity burden materially affect prognosis, reinforcing that risk-stratification tools validated in high-income settings cannot be assumed to perform identically elsewhere. Locally derived data are therefore necessary to determine whether established biomarkers and cut-offs retain their prognostic value in a given population.12 This study was therefore undertaken to evaluate the prognostic significance of NT-proBNP in predicting adverse in-hospital outcomes among 92 patients with acute STEMI presenting to a tertiary care center in Bangladesh, with the aim of establishing a locally validated cut-off and clarifying the marker's clinical utility for early risk stratification in this population.

This prospective observational analytical study was conducted in the Department of Cardiology, National Heart Foundation Hospital and Research Institute, Dhaka, Bangladesh, from May 2017 to April 2018 after obtaining approval from the Institutional Ethics Review Committee. A total of 100 consecutive patients with acute ST-segment elevation myocardial infarction (STEMI) undergoing reperfusion therapy were initially screened, of whom 92 patients were finally included after excluding eight patients with poor echocardiographic windows. Written informed consent was obtained from all participants. Baseline demographic characteristics, cardiovascular risk factors, clinical findings, electrocardiographic features, and laboratory investigations, including random blood glucose, HbA1c, serum creatinine, fasting lipid profile, cardiac troponin-I, CK-MB, and serum electrolytes, were recorded using a structured case record form. Venous blood samples were collected on admission before echocardiographic assessment to measure plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP) using the Getein1100 Immunofluorescence Quantitative Analyzer (Getein Biotech, China), and patients were categorized into normal (100–900 pg/mL) and elevated (>900 pg/mL) NT-proBNP groups. Transthoracic echocardiography was subsequently performed using a GE Vivid E9 system with a 2.5-MHz phased-array transducer to assess left ventricular ejection fraction (LVEF) by the modified Simpson's biplane method and left atrial volume index (LAVI) according to the recommendations of the American Society of Echocardiography. Patients were followed throughout their hospital stay for the occurrence of adverse in-hospital outcomes. Data were analyzed using IBM SPSS Statistics version 22.0. Continuous variables were expressed as mean ± standard deviation (SD) and compared using the independent-samples Student's *t*-test, whereas categorical variables were presented as frequencies and percentages and compared using the chi-square test or Fisher's exact test, as appropriate. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic performance of admission NT-proBNP in predicting adverse in-hospital outcomes by calculating the area under the curve (AUC), sensitivity, specificity, and 95% confidence intervals. A two-tailed p value <0.05 was considered statistically significant.

Table 1. Age Distribution of the Study Population (n = 92)

The mean age of the study population was 53.66 ± 11.63 years. The highest proportion of patients belonged to the 51–60 years age group (31.5%), followed by those aged >60 years (27.2%), 41–50 years (26.1%), and <40 years (15.2%). These findings indicate that acute STEMI was most frequently observed among middle-aged and older adults in the study population.

Figure 1: Sex Distribution of the Study Population (n = 92)

Among the 92 study participants, 79 (85.9%) were male and 13 (14.1%) were female, demonstrating a marked male predominance among patients presenting with acute STEMI.

Table 2: Clinical Characteristics of the Study Population (n = 92)

Regarding cardiovascular risk factors, hypertension was present in 44 (47.8%) patients, dyslipidemia in 41 (44.6%), and diabetes mellitus in 39 (42.4%). Nearly one-third of the patients (32.6%) were current smokers, while 14.1% were ex-smokers. A family history of ischemic heart disease was documented in 34.8% of patients. According to the Killip classification, the majority of patients (83.7%) presented in Killip class I, whereas 16.3% were in Killip class II on admission.

Table 3: Baseline laboratory and echocardiographic findings of the study population.

Of the study population, 39 (42.4%) patients had elevated NT-proBNP levels (>900 pg/mL), while 53 (57.6%) had NT-proBNP levels between 100 and 900 pg/mL. High LAVI (>34 mL/m²) was observed in 48 (52.2%) patients. The mean NT-proBNP level was substantially higher among patients with elevated LAVI than among those with normal LAVI (1234.6 ± 738.8 pg/mL vs. 689.5 ± 721.0 pg/mL, p = 0.001). The mean left ventricular ejection fraction was 41.7 ± 6.7% in the high-LAVI group and 43.3 ± 6.2% in the normal-LAVI group.

Table 4: Association of NT-proBNP level with adverse in-hospital outcome.

Patients with elevated NT-proBNP levels (>900 pg/mL) experienced a significantly higher frequency of adverse in-hospital outcomes than those with normal NT-proBNP levels (89.7% vs. 62.3%, p = 0.003). Conversely, uneventful hospital courses were more common among patients with normal NT-proBNP levels (37.7% vs. 10.3%). These findings suggest that elevated NT-proBNP is significantly associated with adverse in-hospital outcomes in patients with acute STEMI.

Table 5: Diagnostic performance of NT-proBNP in predicting adverse in-hospital outcome.

Receiver operating characteristic (ROC) analysis demonstrated that an NT-proBNP cut-off value of 900 pg/mL yielded a sensitivity of 50.0% and specificity of 83.3% for predicting adverse in-hospital outcomes. The area under the ROC curve (AUC) was 0.631 (95% CI: 0.511–0.751), indicating modest discriminatory ability. The ROC analysis did not reach conventional statistical significance (p = 0.057).

This study evaluated the prognostic significance of NT-proBNP in 92 patients with acute STEMI. Elevated NT-proBNP (>900 pg/mL) was found in 42.4% of patients and was significantly associated with adverse in-hospital outcomes, occurring in 89.7% of patients with high NT-proBNP compared with 62.3% of those with normal levels (p=0.003), while uneventful hospital courses were correspondingly more frequent in the normal NT-proBNP group (37.7% vs 10.3%). This directional association is consistent with Zhu et al.13, who evaluated NT-proBNP alongside the systemic immune-inflammation index in STEMI patients and similarly reported that the two markers correlated positively with adverse outcomes and remained independent indicators of clinical prognosis. On ROC analysis, a cut-off of 900 pg/mL in our cohort yielded 50.0% sensitivity and 83.3% specificity, with an AUC of 0.631 (95% CI: 0.511–0.751), which did not reach conventional statistical significance (p=0.057). A near-identical cut-off was independently validated by Badiger et al.14, who correlated NT-proBNP with the Tpeak–Tend/QT interval ratio in STEMI patients and found that NT-proBNP levels above 900 pg/mL were strongly associated with heart failure risk, lending external support to the threshold used in our analysis despite our AUC falling short of significance. By contrast, Ozbaltan et al.15 used a considerably lower threshold in a broader ACS cohort and reported stronger discrimination, with an NT-proBNP level of 250 pg/mL achieving 73.1% sensitivity and 88.3% specificity for predicting major adverse cardiovascular events, and an AUC of 0.847 likely reflecting that study's inclusion of NSTEMI and unstable angina alongside STEMI and its longer 6-month follow-up window, versus our STEMI-restricted, in-hospital-only endpoint and smaller sample of 92 patients, both of which limit statistical power and event accrual.  Patients with elevated NT-proBNP in our cohort also had higher LAVI values and lower LVEF, suggesting that NT-proBNP release reflects both ventricular wall stress and atrial remodeling rather than ventricular dysfunction alone. This is consistent with Bacaksiz et al.16, who assessed left atrial functional indices in STEMI patients treated with PCI and found that NT-proBNP, LV dyssynchrony, and left atrial volume were each associated with PCI outcomes and predicted short- and long-term prognosis, reinforcing that NT-proBNP elevation and atrial structural change tend to occur together as part of the same post-infarction stress response rather than as independent phenomena. ScienceDirect The standalone discriminatory power of NT-proBNP observed here (AUC 0.631) was notably lower than that reported when NT-proBNP was combined with an additional biomarker. Zhu et al.13 found that the combined SII–NT-proBNP index achieved 78.0% sensitivity and 88.0% specificity for predicting major adverse cardiovascular events, outperforming either marker alone in DeLong testing. This pattern supports our interpretation that NT-proBNP's borderline ROC significance (p=0.057) in our study most likely reflects the limitations of a single-marker, modestly sized cohort (n=92) rather than a true absence of prognostic effect, given the strong and statistically significant categorical association we observed between NT-proBNP elevation and adverse outcome.  Baseline demographic and clinical characteristics in our study a mean age of 53.7±11.6 years, male predominance (85.9%), and a risk-factor profile dominated by hypertension (47.8%), dyslipidemia (44.6%), and diabetes (42.4%), with 83.7% of patients presenting in Killip class I were broadly comparable to those reported across the cited STEMI and ACS cohorts 13⁻14, indicating that the differences in NT-proBNP's predictive performance across studies are more plausibly explained by methodological factors (cut-off selection, single- vs multi-marker design, follow-up duration, endpoint definition) than by underlying population differences. Taken together, these findings support NT-proBNP as a clinically meaningful, accessible marker of adverse in-hospital risk in acute STEMI in our population, while indicating that its predictive performance would likely be strengthened by combination with a structural parameter such as LAVI or an inflammatory index, a direction supported by Zhu et al.13 and consistent with our own findings. Larger, multi-center studies in the Bangladeshi population are warranted to validate optimal cut-offs and to evaluate multi-marker risk-stratification models.

Limitation of the Study:

This was a single-center study with a relatively small sample size and assessment limited to in-hospital outcomes, which may reduce the generalizability of the findings.

Admission NT-proBNP is a valuable biomarker for early risk stratification in acute STEMI. Elevated levels were significantly associated with adverse in-hospital outcomes, supporting its clinical utility in identifying high-risk patients. Incorporating NT-proBNP into routine assessment may improve prognostic evaluation and facilitate timely, individualized management strategies.

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