Impact of body mass index on clinical outcomes following percutaneous coronary intervention in young adults with non-ST-elevation myocardial infarction

INTRODUCTION

Global health systems continue to face a significant challenge from acute coronary syndrome (ACS). Within this spectrum, non-ST elevated myocardial infarction (NSTEMI) represents a substantial portion of cases that necessitate invasive coronary angiography and revascularisation. While coronary artery disease (CAD) typically manifests in older populations, there is a burgeoning trend of premature CAD among young adults, with a particularly high prevalence noted in developing countries & South Asian demographics.^{[1, 2]}

Body mass index (BMI) serves as a primary metric for obesity and a critical determinant of cardiovascular risk. Elevated BMI is often coupled with metabolic disturbances- such as hypertension, dyslipidaemia and systemic inflammation, which collectively drive the progression of atherosclerosis.^[3] Interestingly, the “obesity paradox” has emerged in recent literature, suggesting that overweight or obese patients may experience comparable or even improved clinical outcomes after cardiac interventions.^[4,5] This paradoxical association has been observed in patients with CAD, heart failure, and ACS.

Despite the clinical relevance of this phenomenon, evidence remains sparse concerning the link between BMI and PCI outcomes in young NSTEMI patients. Therefore, this study aimed to evaluate the impact of BMI on angiographic findings, procedural characteristics, and in-hospital outcomes among young adults (≤40 Years) undergoing PCI following NSTEMI.

MATERIAL AND METHODS

This observational cross-sectional study included 120 consecutive patients aged <40 years who underwent PCI following NSTEMI at a tertiary cardiac care centre. NSTEMI was diagnosed according to established clinical and biochemical criteria, including ischemic symptoms, elevated cardiac biomarkers, and electrocardiographic changes without persistent ST-segment elevation, consistent with current guidelines from the European Society of Cardiology.^[6]

BMI was calculated as weight in kilograms divided by height in meters squared (kg/m²). Patients were classified according to the World Health Organisation BMI criteria.^[3]

• Underweight: <18.5 kg/m²

• Normal weight: 18.5–24.9 kg/m²

• Overweight: 25–29.9 kg/m²

• Obese: ≥30 kg/m²

Demographics data, cardiovascular risk factors (hypertension, diabetes, smoking, and dyslipidaemia), echocardiographic findings (LVEF), angiographic severity, PCI procedural details, and in-hospital outcomes were recorded.

Categorical variables were expressed as counts and percentages; continuous variables as mean ± SD. Comparisons across BMI groups were performed using Chi-square or Fisher’s exact test (for small counts). A p-value <0.05 was considered statistically significant.

RESULTS

A total of 120 patients with NSTEMI were included in the study. The majority of the patients were male (108, 90%), while 12 patients (10%) were female, showing a clear male predominance.

BMI distribution was: underweight 8 (6.7%), normal 68 (56.6%), overweight 32 (26.7%) and obese 12 (10.0%). The mean BMI of the study population was 23.8 ± 5.0 kg/m². Most patients belonged to the normal BMI category. BMI distribution among study populations is seen in Figure 1.

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Figure 1: Showing distribution of body mass index (BMI).

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Hypertension was present in 78 (65.0%), diabetes in 58 (48.3%), smoking in 60 (50.0%), and dyslipidaemia in 59 (49.2%). Overweight patients had a higher prevalence of diabetes (62.5%) [Table 1].

LVEF was preserved across all groups (54–59%). Distribution is seen in Figure 2.

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Figure 2: Showing distribution left ventricular ejection fraction (LVEF) among body mass index (BMI) Categories

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Angiographic findings

Coronary angiography revealed single-vessel disease in 39 (32.5%), double-vessel in 30 (25.0%), and triple-vessel in 25 (20.8%) patients [Table 2 and Figure 3].

Table 2: Angiographic severity in body mass index categories

Angiographic finding	Underweight (n=8)	Normal (n=68)	Overweight (n=32)	Obese (n=12)	Total (n=120)	p-value
Single-vessel disease	3 (37.5%)	22 (32.4%)	10 (31.3%)	4 (33.3%)	39 (32.5%)	0.98
Double-vessel disease	2 (25.0%)	17 (25.0%)	8 (25.0%)	3 (25.0%)	30 (25.0%)	1.00
Triple-vessel disease	1 (12.5%)	14 (20.6%)	7 (21.9%)	3 (25.0%)	25 (20.8%)	0.85
Non-significant CAD / other	2 (25.0%)	15 (22.1%)	7 (21.9%)	2 (16.7%)	26 (21.7%)	0.92

p-value <0.05 was considered statistically significant. CAD: Coronary artery disease.

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Figure 3: Angiographic severity of coronary arteries among body mass index (BMI) categories, CAD: Coronary artery disease.

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DISCUSSION

The primary findings of this investigation include: (1) a remarkably high prevalence of traditional cardiovascular risk factors within this young cohort; (2) a significantly higher burden of metabolic comorbidities, such as hypertension and dyslipidaemia, among overweight participants; and (3) a lack of significant association between BMI categories and angiographic severity, procedural characteristics and inhospital outcomes.

Early-onset CAD is a critical global health priority, particularly within low-to-middle-income nations and South Asian populations.^[2,7]

Young adults presenting with ACS frequently exhibit a high density of modifiable risk factors, including smoking, hypertension, diabetes mellitus, and dyslipidaemia.^[8,9]

In our study, smoking, hypertension, and diabetes were the most prominent contributors. These observations align with the landmark INTERnational HEART study study, which demonstrated that modifiable risk factors account for the majority of myocardial infarction risk.^[8] Additionally, obesity and metabolic syndrome are increasingly recognised contributors to premature coronary artery disease, especially in the young.^[4,10]

Our data revealed that single-vessel disease was the predominant angiographic pattern. This is consistent with existing literature suggesting that younger patients often present with less diffuse coronary involvement than their older counterparts.^[9,5]

Interestingly, despite the known risks associated with obesity, the present study did not demonstrate a significant association between BMI category and angiographic disease severity and outcome in young patients with NSTEMI. This mirrors findings from other PCI registries where BMI showed limited predictive value for CAD severity.^[11] This may reflect the multifactorial pathogenesis of CAD in younger individuals, where genetic predisposition, metabolic abnormalities, inflammatory processes, and smoking may play a more important role than body weight alone.^[4,10]

One of the most tempting observations in cardiovascular epidemiology is the “obesity paradox,” in which overweight or mildly obese patients demonstrate better survival outcomes compared with individuals with normal BMI.^[4,12] While some meta-analyses support this paradox even in premature CAD,^[10,12]

Multiple hypotheses have been proposed to explain the obesity paradox observed in cardiovascular disease. Additionally, BMI does not accurately distinguish between lean mass and adipose tissue, nor does it reflect fat distribution. Central obesity and visceral adiposity may be more closely associated with adverse cardiovascular outcomes than BMI alone.^[4]

Although BMI was not significantly associated with angiographic severity or in-hospital outcomes in this study, overweight patients demonstrated a higher prevalence of metabolic risk factors such as diabetes and dyslipidaemia. These findings emphasise the importance of comprehensive cardiovascular risk factor assessment in young individuals presenting with NSTEMI.^[13]

Focusing on early identification and management of modifiable risk factors, such as smoking cessation, blood pressure and glycaemic control, lipid management, and lifestyle modification, remains a cornerstone of preventing premature CAD and improving long-term outcomes.^[6]

Furthermore, BMI alone may not be sufficient for cardiovascular risk stratification. Future studies should incorporate additional measures such as waist circumference, visceral adiposity and metabolic health status to better refine risk stratification and its outcome.^[4]

CONCLUSION

In young adults presenting with NSTEMI and undergoing PCI, there is a high prevalence of traditional cardiovascular risk factors, notably hypertension, diabetes mellitus, and smoking. Although overweight patients in this cohort exhibited a greater burden of metabolic co-morbidities, BMI did not serve as a significant predictor of angiographic severity or in-hospital outcomes. These results underscore the necessity of aggressive early screening and risk factor modification to combat the rise of premature coronary artery disease. Furthermore, invasive management appears to be both safe and effective in this younger demographic, yielding favourable short-term results. To further elucidate the complex interplay between BMI, metabolic health, and long-term post-PCI prognoses in young NSTEMI patients, large-scale multicentre studies with extended follow-up periods are warranted.