Abstract
Background
Acute coronary syndrome (ACS) is a critical condition with diverse clinical presentations. Aromatherapy, particularly with peppermint essential oil, has been explored for its potential to alleviate patient symptoms.
Objective
This study examines the effects of peppermint essential oil aromatherapy on anxiety, stress, and hemodynamic parameters in patients with ACS.
Methods
This randomized, double-blind clinical trial involved ACS patients from Qom University hospitals, recruited between July 2023 and January 2024. The intervention group received 0.2 mL of peppermint essential oil on an eye pad, while the control group received normal saline. Both groups underwent 20-minute sessions in a controlled environment, with data on demographics, stress, anxiety, and hemodynamic parameters collected.
Results
Peppermint oil significantly reduced systolic blood pressure (from 139.77 ± 10.83 to 126.36 ± 7.49 mmHg, P < 0.001), diastolic blood pressure, heart rate, pain scores, anxiety (from 24.64 ± 5.15 to 19.55 ± 3.10, P < 0.001), and stress levels (from 25.00 ± 5.14 to 17.18 ± 4.42, P < 0.001) compared to the placebo group.
Conclusion
Peppermint essential oil aromatherapy significantly improves cardiac parameters and reduces anxiety and stress in ACS patients. These findings suggest that incorporating aromatherapy into clinical practice may enhance patient well-being and provide a complementary approach to managing the challenges associated with ACS.
Introduction
Coronary diseases, especially ACS, are significant due to their high prevalence and impact on global mortality and morbidity, as ACS results from atherosclerotic plaque rupture and thrombosis, leading to myocardial ischemia or infarction and is a major cause of cardiovascular-related deaths worldwide. 1 Physiological and psychological changes from chest pain, fear of fatality, unfamiliar medical settings, invasive procedures, observation of critically ill patients, poor communication with healthcare professionals, and lack of social support contribute to heightened acute stress levels in ACS patients. 2 Stress emerges as a significant risk factor for this patient cohort, necessitating its serious consideration within the domain of cardiology care. The interplay between the “brain-heart axis” is particularly pivotal in determining cardiovascular outcomes, especially among individuals with pre-existing cardiovascular conditions. 3 Moreover, anxiety and depression are notably prevalent among patients experiencing ACS, with over half of this demographic exhibiting such psychological conditions. Notably, depression occurs more frequently than anxiety, thereby highlighting the urgent need for targeted therapeutic interventions. 4
Non-pharmacological strategies within psychology and complementary medicine have gained recognition as effective modalities for mitigating stress, anxiety, and adverse hemodynamic responses in individuals suffering from cardiovascular ailments. 2 Herbal remedies have shown promise as adjunctive therapies for those afflicted with ACS. Empirical studies suggest that commonly utilised herbal formulations do not result in significant adverse effects, thereby rendering them a safe alternative for patients with coronary heart disease. 5 The combination of herbal medicine with conventional Western treatments has shown greater efficacy in reducing major adverse cardiac events after percutaneous coronary intervention in ACS patients compared to Western medicine alone, suggesting that integrating traditional herbal therapies with established medical approaches may provide additional benefits in managing ACS and its complications. 6 The application of aromatic herbal substances such as lavender, chamomile, citrus aurantium, ginger, and mandarin has been advocated as a benign method for alleviating pain, and stress while simultaneously stabilising vital signs in patients with cardiovascular diseases. 7 Peppermint, a member of the Lamiaceae family, has been used as a rubefacient for centuries and is recognized for its ability to lower heart rate and systolic blood pressure, relax bronchial smooth muscles, and enhance ventilation, with its therapeutic efficacy primarily attributed to menthol, the principal active ingredient, which provides analgesic, anxiolytic, sedative properties, and improves sleep quality. 8
A plethora of studies have substantiated the effectiveness of peppermint in mitigating anxiety and stress among diverse patient cohorts.9-11 Nevertheless, there remains a pressing need for further investigation into the implications of olfactory stimulation using peppermint essential oil, particularly concerning its influence on hemodynamic symptoms and stress levels in patients experiencing ACS, a subject of considerable importance. Consequently, the aim of our research was to examine the effects of olfactory stimulation with peppermint essential oil on hemodynamic manifestations, as well as on stress and anxiety within this specific patient demographic.
Methods and Materials
Study Design
The investigation was structured as a randomized, double-blind clinical trial comprising 2 distinct groups: an intervention group and a control group. The study population encompassed individuals diagnosed with ACS who sought treatment at the emergency departments of educational hospitals affiliated with Qom University of Medical Sciences. The recruitment of participants for this study occurred between July 2023 and January 2024.
The inclusion criteria stipulated that participant had to be fully conscious, aged between 18 and 60 years, and free from valvular heart disease, severe illnesses, or any impairments related to vision, hearing, or olfaction. Furthermore, individuals were required to exhibit no respiratory or allergic conditions, a history of substance abuse, hepatic or renal dysfunction, or the use of sedative medications within 4 hours prior to the intervention. Additionally, a documented absence of psychiatric disorders such as depression, anxiety, or stress was mandatory. Conversely, exclusion criteria encompassed the sudden emergence of severe alterations in vital signs, the presence of perilous cardiac arrhythmias, and any unwillingness to continue participation in the study.
Sampling and Sample Size Calculation
Patients who met the eligibility criteria were initially incorporated into the study through non-probability consecutive sampling. Following this, they were assigned to either the peppermint group or the placebo group via stratified block random sampling. Drawing on the anxiety scores reported in the study by Maghreb et al. (2017), which focused on patients undergoing colonoscopy, the intervention group that inhaled peppermint essential had a post-intervention anxiety level of 45.5 ± 4.0, compared to 50.1 ± 5.9 in the control group. 12 Using G. Power software (Version 3.1.9.2) and determining an effect size of 0.91, based on previous study, taking into account alfa error of 0.01 and a power of 0.95, the sample size was estimated to be 40 in each group.
Randomization
Eligible participants were recruited through convenience sampling. Before randomization, each underwent a medical history assessment, physical examination, and electrocardiogram by a cardiology specialist. Patients were assigned to the peppermint or placebo groups using stratified block randomization to ensure balanced gender distribution. Randomization was done in blocks of 4 with a 1:1 allocation ratio through a computer-generated list. The study workflow is shown in Figure 1. CONSORT diagram of the study
Blinding
Peppermint essential oil and a visually indistinguishable placebo (normal saline) were prepared and supplied in identical dark glass bottles labeled only with codes ‘A' and ‘B' by Barij Essence Pharmaceutical Company. The allocation sequence and key were held by an independent research nurse who had no contact with participants or involvement in data collection or outcome assessment. All participants, in both groups, were informed that they would receive 1 of 2 forms of aromatherapy with potential relaxing effects, neither described as definitively active or inactive. The control solution was presented as a “neutral aromatic base.” The administering nurse wore a tightly sealed, odor-neutralizing nasal clip continuously from the moment of preparing the eye pad until the end of the session and the removal of the pad from the participant’s environment, ensuring she was completely blinded to the group assignment.
Intervention
All participants received guideline-directed medical therapy for ACS throughout the study period, including antiplatelets, anticoagulants, statins, beta-blockers, nitrates, and analgesics as clinically indicated. The experimental aromatherapy intervention was administered as a complementary adjunct to this standard pharmacological management. In the intervention group, 0.2 mL of 100% peppermint essential oil from Barij Essence Company was applied to a non-absorbent eye pad. The control group received a non-absorbent eye pad saturated with 0.2 mL of normal saline for 20 minutes in a separate room. Both eye pads were secured to the patients’ clothing at the chest with a pin. The intervention took place under cardiac monitoring, with patients comfortably positioned in a controlled environment at 18 to 24 degrees Celsius. During the sessions, a nurse closely monitored the patients’ clinical status, documenting any signs of dyspnea, chest pain, arrhythmias, hemodynamic changes, and headaches using cardiac monitoring and self-report checklists.
Outcome Measures and Data Collection
The primary outcomes were psychological measures of acute stress and anxiety. Secondary outcomes included physiological and symptomatic measures: hemodynamic parameters (systolic blood pressure, diastolic blood pressure, mean arterial pressure, and heart rate) and chest pain intensity. These variables were selected because they are clinically important for this patient population and their relevance is well-supported by prior research on herbal essential oil aromatherapy.2,12 The instruments employed for data collection encompassed a form designed to capture socio-demographic and clinical characteristics, a condensed version of the 21-item Stress Scale, the Depression, Anxiety, and Stress Scale (DASS-21), a Visual Analog Scale (VAS), and a form dedicated to recording haemodynamic parameters. The socio-demographic clinical characteristics were assessed via a 12-question format addressing variables such as age, gender, and history of myocardial infarction, with responses gathered through face-to-face interviews. Acute stress was evaluated as the primary outcome measure using the DASS-21 scale.
The DASS-21, developed by Lovibond and Lovibond in 1995, 13 comprised 21 items divided into 3 subscales: stress, anxiety, and depression. Each item was rated on a four-point Likert scale, with scores subsequently doubled. The DASS-21 underwent rigorous validation as an assessment tool, demonstrating acceptable reliability and validity.7,14
To evaluate the severity of chest pain, the Visual Analog Scale (VAS) was employed. This scale operated as a continuous measurement tool, represented by a ruler extending from 0 to 10 cm. Participants were instructed to indicate their pain intensity on this scale, with 0 denoting the absence of pain and 10 representing the most excruciating pain conceivable. A score of zero signified no pain; scores ranging from 1 to 2.9 reflected mild discomfort; scores between 3 and 6.9 denoted moderate pain; whereas scores of 7 and above indicated acute pain. 2 The VAS underwent rigorous validation for assessing the intensity of acute pain within the context of emergency medical settings. 15 Furthermore, the intensity of chest pain was monitored as a potential confounding variable.
The hemodynamic parameters identified as secondary outcomes encompassed mean arterial pressure (MAP) measured in mmHg and heart rate (HR) expressed in beats per minute (bpm). These parameters were meticulously monitored via a digital cardiac monitoring system, with readings systematically documented on a designated vital sign chart. Blood pressure measurements (in mmHg) and heart rate evaluations were conducted while the patient was positioned supine.
Ethical Considerations
This clinical trial adhered to the Declaration of Helsinki guidelines and received approval from the Ethics Committee of Qom University of Medical Sciences (ethics code IR.MUQ.REC.1401.174). Written informed consent was obtained from all participants, who could withdraw at any time. They were assured of confidentiality and secure data handling. The trial was registered with the Iranian Registry of Clinical Trials under code IRCT20221205056718N1.
Data Analysis
Descriptive statistics for quantitative variables were reported as Mean ± SD or Median (IQR), while qualitative variables were expressed as frequencies. Normality was assessed using the Kolmogorov-Smirnov test. In cases where the data were normally distributed, a paired t-test was employed, while the Wilcoxon test was utilized for non-normally distributed data. Homogeneity of qualitative variables was examined with Chi-square or Fisher’s exact tests. Data analysis was performed using SPSS Statistics version 26.0, with statistical significance set at P < 0.05.
Results
Comparison of Demographic Characteristics Between Two Study Groups
Comparison of Stress, Depression, Anxiety, MAP, HR and Pain Scores Between Two Study Groups at Different Times (Mean ± SD)
*P-value is significant at the 0.05 level.
In terms of pain management, peppermint oil significantly reduced pain scores from 6.18 ± 0.94 to 4.59 ± 0.89 (P < 0.001), whereas the placebo group showed no significant improvement, with scores changing from 6.09 ± 0.96 to 5.98 ± 0.95 (P = 0.132). Anxiety levels were also significantly decreased in the peppermint oil group, with scores dropping from 24.64 ± 5.15 to 19.55 ± 3.10 (P < 0.001), while the placebo group did not exhibit any notable changes. Furthermore, a marked reduction in stress levels was observed in the peppermint oil group, with scores declining from 25.00 ± 5.14 to 17.18 ± 4.42 (P < 0.001), whereas the placebo group exhibited a slight increase in stress levels, rising from 25.14 ± 5.36 to 25.95 ± 5.16 (P = 0.005) (Table 2).
Discussion
The study highlights the significant effects of peppermint oil on various physiological and psychological parameters in patients with ACS. Compared to placebo, peppermint oil significantly reduced systolic blood pressure, heart rate, pain, anxiety, and stress. These findings suggest that peppermint oil may serve as a complementary treatment for ACS, potentially improving patient outcomes during acute episodes.
One of the most compelling results of the trial is the significant reduction in systolic blood pressure in the peppermint oil group. In contrast, the placebo group exhibited no significant change in systolic blood pressure, with values remaining relatively stable. The effects of peppermint essential oil on blood pressure are inconsistent; some studies report increases while others indicate decreases. Notably, 1 study found that inhalation of peppermint essential oil does not significantly affect systolic blood pressure. 16 The reason for this discrepancy can be attributed to the methods of administration and the contexts in which they are applied across different groups of individuals. The potential of peppermint oil to exert a significant antihypertensive effect likely underscores mechanisms such as vasodilation or the modulation of autonomic nervous system activity, which may impact the cardiovascular system. 17 Furthermore, while both groups demonstrated a statistically significant reduction in diastolic blood pressure, the peppermint oil group experienced a more pronounced decrease, reinforcing the notion that peppermint oil may enhance cardiovascular function in patients with ACS. Essential oil aromatherapy has shown promise in improving cardiac symptoms, particularly blood pressure and stress responses. A study on clients with essential hypertension found that inhaling a blend of lavender, ylang-ylang, and bergamot essential oils daily for 4 weeks significantly reduced blood pressure, pulse rate, subjective stress, state anxiety, and serum cortisol levels compared to placebo. 18 In another study, lavender aromatherapy reduced systolic and diastolic blood pressure and heart rate in patients after open-heart surgery, suggesting its potential as a complementary intervention for stabilizing vital signs in cardiac care settings. 19 Essential oils contain various active compounds that contribute to their therapeutic effects, and peppermint essential oil, in particular, includes several compounds such as menthol, menthone, limonene, menthofuran, and isomenthone, which enhance its effects on the body.20,21 Diastolic blood pressure exhibited a significant decrease in the intervention group; however, it is noteworthy that a similar reduction was observed in the placebo group. This phenomenon may be attributed to the placebo effect stemming from study participation and the attention received from healthcare providers, as well as a relaxation response facilitated by the calming environment.22,23 Interpretation of the benefits attributed to peppermint oil must account for 2 key contexts. First, all participants in this trial received standard, guideline-directed pharmacological therapy for ACS (eg, antiplatelets, anticoagulants, beta-blockers, analgesics), which has a powerful and established effect on hemodynamics and symptom relief. The peppermint oil intervention was administered as a complementary adjunct to this foundational care. Therefore, the observed improvements particularly in physiological parameters like blood pressure and heart rate represent an additive effect layered upon optimized medical management, not a substitute for it. Second, as a non-pharmacological sensory intervention, aromatherapy is inherently susceptible to strong contextual and placebo effects; the distinctive peppermint scent may have amplified both perceived and measured responses, despite efforts to blind participants. In addition to blood pressure changes, the trial reported a modest yet significant reduction in heart rate within the peppermint oil group, while no significant change was observed in the placebo group. Similar to our study, previous studies have revealed that the application of some essential oils on the heart rate can lead to hypotension thereby leading to general cardiovascular health. 24 In a separate study, the inhalation of lavender oil was found to significantly reduce both heart rate and blood pressure, indicating a calming effect on physiological stress responses. 25 However, the effects of essential oils can vary based on the specific type of oil and the duration of exposure. For instance, prolonged exposure to certain essential oils may lead to increased heart rate and blood pressure, thereby highlighting potential risks associated with long-term use. 26 Therefore, the therapeutic potential of essential oils in the treatment of cardiovascular diseases, such as arterial hypertension and heart failure, warrants further investigation.
Pain management is a critical aspect of ACS treatment, and the results indicate that peppermint oil significantly reduced pain scores, whereas the placebo group showed no significant improvement. Another study investigated the efficacy of peppermint essential oil (0.2%) as a topical anesthetic in children, demonstrating its effectiveness in reducing pain. When compared to lignocaine spray, children treated with peppermint oil reported significantly lower pain scores on the Wong-Baker Faces Pain Rating Scale and exhibited improved pain tolerance, thereby confirming its analgesic potential. 27 The analgesic properties of peppermint oil can be attributed to menthol, known for its cooling and soothing effects, which may distract patients from pain perception and enhance comfort during acute episodes. Menthol primarily activates TRPM8, a receptor that mediates cold sensations, creating a cooling effect that distracts the brain from pain signals while also inhibiting pain pathways in the central nervous system, thereby enhancing its analgesic effects. 28 The psychological dimensions of ACS management are equally important, and this trial revealed significant reductions in anxiety and stress levels among participants receiving peppermint oil. In stark contrast, the placebo group exhibited a slight increase in stress levels, suggesting that standard care alone may not adequately address psychological distress associated with ACS. Consistent with our study, a placebo-controlled trial demonstrated that aromatherapy with peppermint essential oil effectively reduced anxiety in cardiac patients in the emergency department, indicating its potential as a complementary therapy for stress management in this population. 9 Furthermore, a literature review indicated that various complementary therapies, including peppermint oil inhalation, are effective in reducing anxiety and pain in patients with ACS. 29 The calming effects of peppermint oil are attributed to its influence on the central nervous system, which may help in managing stress and anxiety levels.
Limitation
Our study has several important limitations. First, while rigorous efforts were made to blind investigators and outcome assessors, the inherent nature of the olfactory intervention poses a significant challenge to participant blinding. The distinctive scent of peppermint oil, compared to the odorless saline placebo, may have allowed some participants to discern their group assignment, potentially introducing expectation bias. Second, individual responses to aromatherapy can vary due to differences in olfactory sensitivity and psychological factors, complicating the interpretation of results. The study was also conducted at a single center with a specific patient cohort, which may limit the generalizability of the findings. Furthermore, the short-term follow-up period restricts our understanding of the sustained effects of the intervention. Finally, while no adverse effects were reported, the study was not powered to comprehensively assess safety, and the underreporting of minor subjective side effects remains a possibility. Addressing these limitations, particularly through designs that better control for olfactory blinding in future trials, is crucial for enhancing the validity and applicability of research in this complementary therapy area.
Conclusion
This randomized clinical trial demonstrates that peppermint aromatherapy is an effective adjunct therapy for patients with acute coronary syndrome (ACS). The intervention significantly reduced blood pressure, heart rate, pain, anxiety, and stress, suggesting its potential to improve both physiological and psychological outcomes during acute care. These results, however, must be interpreted alongside standard clinical management. All patients received foundational pharmacotherapy for ACS, and the benefits of aromatherapy are therefore complementary and additive to evidence-based medical care. Future studies employing an active placebo could further isolate the specific pharmacological contribution of peppermint from the non-specific effects of the therapeutic ritual.
Footnotes
Acknowledgement
The researchers would like to extend their sincere gratitude and appreciation to all individuals who contributed to the successful execution of this study, particularly the research assistant from Qom University of Medical Sciences and the participating patients.
Ethical Considerations
The research adhered to the principles outlined in the Declaration of Helsinki. Prior to conducting the study, approval was obtained from the Medical Ethics Committee at Qom University of Medical Sciences (registration number: IR.MUQ.REC.1401.174). Participants were required to provide written informed consent before being included in the study. It is important to note that all participants had the freedom to withdraw from the study at any time.
Funding
The authors received no financial support for the research, authorship, and/or publication of this article.
Declaration of Conflicting Interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Data Availability Statement
The datasets utilized and/or examined in the present study are accessible upon reasonable request from the corresponding author.