# Association of N-terminal Pro-B-Type Natriuretic Peptide Levels and Electrocardiogram Changes With the Severity of Airflow Narrowing and Exercise Tolerance in Stable Chronic Obstructive Pulmonary Disease Patients: A Cross-Sectional Analytical Study

## TL;DR

This study shows that as COPD worsens, heart strain markers like NT-proBNP increase and exercise ability decreases, suggesting a link between lung and heart health in COPD patients.

## Contribution

The study identifies a progressive relationship between COPD severity and cardiac biomarkers and ECG changes in stable COPD patients.

## Key findings

- NT-proBNP levels increased significantly with worsening COPD severity (ANOVA p < 0.001).
- ECG abnormalities like P pulmonale and right ventricular hypertrophy were more common in severe/very severe COPD.
- Exercise capacity, measured by 6MWD, declined as COPD severity increased.

## Abstract

Background: Chronic obstructive pulmonary disease (COPD) is associated with significant cardiovascular morbidity. N-terminal pro-B-type natriuretic peptide (NT-proBNP), electrocardiogram (ECG) abnormalities, and reduced exercise tolerance may reflect cardiac involvement in COPD, but their relationship with airflow limitation stages is incompletely defined. This study evaluated associations between NT-proBNP, ECG changes, and six-minute walk distance (6MWD) across the Global Initiative for Obstructive Lung Disease (GOLD) stages in stable COPD patients.

Methods: A hospital-based cross-sectional analytical study enrolled 88 stable COPD patients aged ≥40 years between October 2022 and June 2024. Demographic, clinical, spirometric, ECG, 6MWD, and NT-proBNP data were collected. COPD severity was classified by the GOLD criteria. Continuous variables were compared by analysis of variance (ANOVA) and categorical variables by the chi-squared test. A p-value of <0.05 indicated statistical significance.

Results: Of 88 participants, 71 (80.7%) were male and 17 (19.3%) female. Distribution by GOLD stage was as follows: GOLD I 20 (22.7%), GOLD II 39 (44.3%), GOLD III 22 (25%), and GOLD IV seven (8%). Exercise capacity declined with severity: the mean 6MWD decreased markedly from the mild to the very severe groups. NT-proBNP levels rose progressively with airflow limitation (ANOVA p < 0.001), with markedly higher mean concentrations in the very severe group. ECG abnormalities increased with disease stage: P pulmonale was present in 24 (27.3%), right ventricular hypertrophy in 27 (30.7%), right axis deviation in 27 (30.7%), low voltage complexes in eight (9.1%), and incomplete right bundle branch block (IRBBB) in five (5.7%) of the cohort; these changes were more frequent in severe/very severe COPD. Smoking exposure and indices (current/former smokers, cigarettes/day, smoking index, duration) showed significant upward trends with worsening GOLD stage (p ≤ 0.042). NT-proBNP correlated positively with COPD stage, while 6MWD correlated negatively (r values significant; p < 0.001).

Conclusion: In stable COPD, advancing airflow limitation is associated with rising NT-proBNP, increasing ECG evidence of right heart strain, and declining exercise tolerance. NT-proBNP and simple ECG markers, alongside functional testing, may aid the early detection of cardiovascular involvement in COPD and help risk-stratify patients for closer cardiopulmonary evaluation and management.