European Journal of Cardiovascular Medicine

Hypertension (HTN) remains one of the most significant risk factors for cardiovascular diseases (CVD), contributing extensively to the global burden of morbidity and mortality.¹ In India, the prevalence of hypertension has been steadily rising, with an estimated 33% of the adult population affected.¹ It is well-established that hypertensive heart disease significantly increases the risk of myocardial infarction (MI), which remains a leading cause of death in the country.^2,3 Despite advances in treatment, the incidence of MI in hypertensive individuals continues to rise, reflecting the increased burden of both hypertension and its complications in the Indian population.³

The pathological features of myocardial infarction in hypertensive patients are often more severe and complex compared to individuals without hypertension. Chronic high blood pressure induces alterations in the vascular and myocardial structure, leading to accelerated atherosclerosis, left ventricular hypertrophy (LVH), and myocardial fibrosis, all of which contribute to increased myocardial damage during infarction.⁴ Pathological findings from post-mortem studies have shown that hypertensive patients often present with more extensive myocardial necrosis, greater coronary artery atherosclerosis, and increased inflammatory infiltration compared to normotensive patients.⁵

In India, the interplay between hypertension and myocardial infarction is further compounded by factors such as genetic predisposition, dietary habits, lack of awareness, and suboptimal management of risk factors.⁶ Studies have demonstrated that despite high levels of awareness about hypertension, effective control of blood pressure remains a challenge, especially in rural and semi-urban populations.⁷ Understanding the pathological features of MI in the context of pre-existing hypertension is essential for identifying high-risk individuals and tailoring effective treatment strategies.

This article aims to review the pathological changes observed in myocardial infarction among patients with pre-existing hypertension, with a particular focus on the Indian scenario, to enhance clinical management and therapeutic interventions.

The study was conducted at a tertiary healthcare hospital over a period of four years, from January 2021 to November 2024, with a total of 100 participants included. These patients were selected from those diagnosed with myocardial infarction (MI) who had pre-existing hypertension, as well as a control group of MI patients without hypertension. The inclusion criteria for the hypertensive group were patients aged 30-70 years with a confirmed diagnosis of hypertension, as per the World Health Organization (WHO) criteria, and those who had experienced a first or recurrent episode of MI. The control group consisted of age-matched patients with MI but no history of hypertension. Exclusion criteria included patients with secondary causes of hypertension, such as endocrine disorders, or those with contraindications to post-mortem tissue analysis or inadequate clinical data.

A retrospective analysis was performed using hospital records, with patient data gathered from the hospital’s electronic medical records (EMR) and the pathology department. The primary objective was to examine the pathological features of myocardial infarction in hypertensive patients. Detailed clinical information, including age, gender, medical history, comorbidities, and laboratory results, was collected. Pathological features, including myocardial necrosis, fibrosis, coronary artery atherosclerosis, and myocardial hypertrophy, were assessed through post-mortem tissue examination in cases where consent for autopsy was granted. Additionally, tissue samples were obtained from coronary artery segments to study the degree of atherosclerotic plaque formation and any associated inflammation.

The severity of myocardial infarction was graded based on the extent of myocardial damage observed in histological slides, with specific emphasis on the degree of myocardial fibrosis, extent of necrosis, and presence of thrombus formation. These findings were compared between hypertensive and non-hypertensive patients. Data were analyzed using appropriate statistical methods to determine the correlation between the pathological features and the presence of pre-existing hypertension. The study also assessed the impact of hypertension on the overall prognosis, including hospital stay duration, complications like arrhythmias, and mortality rates.

Ethical approval for the study was obtained from the hospital’s Institutional Review Board (IRB), and patient confidentiality was strictly maintained throughout the research. Informed consent was acquired from family members for the post-mortem analysis where applicable. The study was conducted in adherence to the ethical guidelines of the Declaration of Helsinki and relevant local regulations.

The findings from this observational study offer valuable insights into the pathological differences between hypertensive and non-hypertensive myocardial infarction patients, contributing to the understanding of how hypertension exacerbates myocardial damage and impacts patient outcomes. The results are expected to guide future clinical practices and interventions for the management of myocardial infarction in hypertensive patients.

Table 1: Demographic and Clinical Characteristics of Study Participants

Table 1 presents the demographic and clinical characteristics of the study participants, comparing the hypertensive and non-hypertensive groups. The average age of participants in the hypertensive group was 59.3 ± 6.8 years, while the non-hypertensive group had a slightly higher mean age of 60.7 ± 6.2 years, with no statistically significant difference between the two groups (p = 0.33).

Regarding gender distribution, the hypertensive group had a higher proportion of males (74%) compared to the non-hypertensive group, which had 58% males, though this difference was not statistically significant (p = 0.09).

In terms of comorbidities, the prevalence of diabetes was higher in the hypertensive group (48%) compared to the non-hypertensive group (36%), but this difference was also not statistically significant (p = 0.19). Similarly, smoking prevalence was slightly higher in the hypertensive group (44%) compared to the non-hypertensive group (32%), with no significant difference between the two groups (p = 0.26). Lastly, hyperlipidemia was present in 60% of the hypertensive group and 52% of the non-hypertensive group, again showing no statistically significant difference (p = 0.36).

Table 2: Pathological Features of Myocardial Infarction in Hypertensive vs. Non-Hypertensive Groups

Table 2 presents the comparison of pathological features of myocardial infarction (MI) between hypertensive and non-hypertensive groups. The data highlights notable differences in several key pathological features associated with MI.

In terms of myocardial necrosis, a severe form of tissue damage, the hypertensive group showed a significantly higher proportion of severe necrosis (80%) compared to the non-hypertensive group (56%), with a statistically significant difference (p = 0.02). This suggests that severe myocardial necrosis is more common in hypertensive patients who experience MI.

Similarly, myocardial fibrosis, a process where scar tissue forms after the infarction, was also significantly more prevalent in the hypertensive group, with 70% of hypertensive patients showing moderate to severe fibrosis, compared to 44% in the non-hypertensive group (p = 0.04). This suggests that hypertension may exacerbate the fibrotic response following MI, potentially leading to a worse long-term prognosis.

Regarding atherosclerosis, which is the build-up of plaques in the arteries, 60% of hypertensive patients had advanced atherosclerosis, compared to 44% in the non-hypertensive group. However, this difference was not statistically significant (p = 0.14), indicating that while hypertension may contribute to a higher burden of atherosclerosis, the difference was not large enough to be statistically meaningful in this study.

Thrombus formation, the presence of blood clots within the coronary arteries, was observed in 56% of hypertensive patients and 40% of non-hypertensive patients. However, this difference was also not statistically significant (p = 0.18), suggesting that while thrombus formation is more common in hypertensive patients, the difference is not substantial enough to conclude a strong association in this sample.

Table 3: Comparison of Clinical Outcomes in Hypertensive vs. Non-Hypertensive MI Patients

Table 3 compares the clinical outcomes between hypertensive and non-hypertensive patients who experienced myocardial infarction (MI). The hospital stay was significantly longer for the hypertensive group (8.2 ± 3.1 days) compared to the non-hypertensive group (6.4 ± 2.6 days), with a p-value of 0.01, indicating a statistically significant difference. This suggests that hypertensive patients may experience more severe complications or slower recovery post-MI.

For arrhythmias, 44% of hypertensive patients experienced arrhythmias, while 36% of non-hypertensive patients had similar issues. However, this difference was not statistically significant (p = 0.37), indicating that hypertension may not significantly influence the occurrence of arrhythmias in MI patients.

The mortality rate was higher in the hypertensive group (26%) compared to the non-hypertensive group (18%), but this difference was not statistically significant (p = 0.33), suggesting that hypertension may not substantially impact the short-term mortality following MI in this sample.

Table 4: Histological Grading of Myocardial Damage in Hypertensive vs. Non-Hypertensive Groups

Table 4 compares the histological grading of myocardial damage between hypertensive and non-hypertensive groups. The incidence of mild myocardial damage was significantly higher in the non-hypertensive group (38%) compared to the hypertensive group (20%), though the difference was not statistically significant (p = 0.07), suggesting a potential trend that requires further investigation.

For moderate myocardial damage, both groups showed similar proportions (44% in hypertensive and 42% in non-hypertensive), with no significant difference (p = 0.88), indicating that moderate damage is equally prevalent in both groups.

However, severe myocardial damage was notably higher in the hypertensive group (36%) compared to the non-hypertensive group (20%), with a statistically significant difference (p = 0.05). This suggests that hypertensive patients are more likely to experience severe myocardial damage following an MI.

Table 5: Coronary Artery Findings in Hypertensive vs. Non-Hypertensive MI Patients

Table 5 compares the coronary artery findings between hypertensive and non-hypertensive myocardial infarction (MI) patients. The proportion of patients with no significant stenosis was lower in the hypertensive group (16%) compared to the non-hypertensive group (26%), but this difference was not statistically significant (p = 0.18), indicating that there is no strong association between hypertension and the absence of stenosis. Regarding 50-70% stenosis, both groups had similar proportions, with 40% of hypertensive patients and 42% of non-hypertensive patients showing this level of stenosis, and the difference was not statistically significant (p = 0.75). However, for >70% stenosis, a higher proportion of hypertensive patients (44%) had severe stenosis compared to the non-hypertensive group (32%), but this difference was also not statistically significant (p = 0.20), suggesting that while there is a trend towards more severe stenosis in hypertensive patients, it did not reach statistical significance in this study.

The present study aimed to examine the pathological features, clinical outcomes, and coronary artery findings in hypertensive and non-hypertensive patients who suffered a myocardial infarction (MI). The results indicated significant differences between the two groups in certain aspects, particularly in the pathological features of myocardial damage and clinical outcomes such as hospital stay duration. However, other factors such as arrhythmias, mortality, and coronary artery stenosis did not show statistically significant differences.

The hypertensive group exhibited a significantly higher prevalence of severe myocardial necrosis (80% vs. 56%, p = 0.02) and moderate to severe myocardial fibrosis (70% vs. 44%, p = 0.04). These findings are consistent with existing research that suggests hypertension accelerates myocardial damage during infarction, likely due to the increased workload on the heart over time, leading to more extensive tissue damage. A study by Blanca Gordon et al. (2022)⁸ found that patients with pre-existing hypertension tend to have more severe myocardial injury and greater levels of fibrosis following MI, supporting our observation of worse myocardial necrosis and fibrosis in hypertensive patients.

In contrast, the presence of advanced atherosclerosis and thrombus formation did not show significant differences between the groups (p = 0.14 and p = 0.18, respectively), although hypertensive patients had a higher prevalence. This finding aligns with the hypothesis that while hypertension contributes to the progression of atherosclerosis, other factors, such as dyslipidemia or diabetes, may play a more prominent role in determining the extent of coronary artery disease (CAD). Linton et al. (2019)⁹ highlighted that while hypertension exacerbates atherosclerotic plaque formation, the interaction with other risk factors (like diabetes and hyperlipidemia) often determines the severity of CAD.

The clinical outcomes of patients were also influenced by hypertension. The mean hospital stay was significantly longer in the hypertensive group (8.2 ± 3.1 days vs. 6.4 ± 2.6 days, p = 0.01). Hypertensive patients may experience more severe complications such as heart failure, arrhythmias, or delayed recovery due to their already strained cardiovascular system. This is in line with findings from Jenča  et al. (2020)¹⁰, who observed that hypertensive patients with MI often have prolonged hospitalization due to the increased risk of post-infarction complications such as heart failure and arrhythmias.

Despite a higher hospital stay, the incidence of arrhythmias (44% vs. 36%, p = 0.37) and the mortality rate (26% vs. 18%, p = 0.33) did not differ significantly between the groups. These findings suggest that while hypertensive patients may experience more severe myocardial damage and longer hospital stays, their short-term survival and arrhythmic complications may not differ significantly from non-hypertensive MI patients.^11,12 However, Frampton et al. (2023)¹³ found that hypertension is an independent risk factor for arrhythmias post-MI, which might explain the trend towards more arrhythmic events in the hypertensive group in our study, although the difference was not statistically significant.

The hypertensive group demonstrated a significantly higher proportion of severe myocardial damage (36% vs. 20%, p = 0.05). These findings align with research suggesting that chronic hypertension contributes to more severe myocardial injury during an MI event due to structural changes in the heart, such as left ventricular hypertrophy (LVH) and increased collagen deposition in the myocardium.^14.15 Talle et al. (2022)¹⁶ reported that patients with pre-existing hypertension suffer more extensive myocardial damage during infarction, likely because the hypertensive heart has less capacity to tolerate the stress imposed by ischemia.

In terms of coronary artery pathology, while hypertensive patients had a higher prevalence of >70% stenosis (44% vs. 32%, p = 0.20), this difference did not reach statistical significance. The lack of significant differences in the severity of coronary artery stenosis between the two groups may be attributed to the complex interplay of multiple cardiovascular risk factors in both hypertensive and non-hypertensive patients. For instance, hyperlipidemia, smoking, and diabetes can contribute equally to atherosclerotic progression, which may obscure the isolated effect of hypertension. A study by Poznyak et al. (2022)¹⁷ found that while hypertension accelerates the development of atherosclerosis, it is often the combined effect of these risk factors that determines the extent of coronary artery disease.

Overall, the findings of this study underscore the significant impact of hypertension on myocardial infarction. Hypertensive patients exhibited more severe myocardial damage, longer hospital stays, and greater myocardial fibrosis, which may contribute to worse long-term outcomes. However, factors such as arrhythmias, mortality, and coronary artery stenosis did not show significant differences between hypertensive and non-hypertensive MI patients. These results are consistent with previous studies that have highlighted the compounded effect of hypertension on myocardial injury and recovery post-MI, but they also suggest the need for further research to understand the complex interaction between hypertension and other cardiovascular risk factors in MI. Future studies with larger sample sizes and longer follow-up periods are needed to explore the long-term outcomes of hypertensive MI patients and the impact of intensive hypertension management on reducing myocardial damage and improving recovery.

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