The effect of symptoms on prehospital delay time in patients with acute myocardial infarction

Abstract

Objective

To improve time to treatment, the effects of acute myocardial infarction (AMI) symptoms on prehospital delay time (PDT) were investigated.

Methods

Patients with AMI completed a questionnaire on their AMI symptoms and their general knowledge of AMI symptoms.

Results

In total, 116 patients completed questionnaires. The mean PDT was 7.3 ± 2.4  h; the median PDT was 2.2 h. Each patient experienced a mean of 3.6 symptoms during their AMI. PDT was significantly shorter in the following groups: patients with chest compression pain/chest discomfort, profuse sweating or dyspnoea than in patients with other symptoms; patients presenting with typical rather than atypical symptoms; patients with pain scores >6 compared with scores ≤6; patients who were aware rather than unaware of AMI symptoms. Patients actually having AMI symptoms and patients being aware of AMI symptoms were inversely correlated with PDT. There was a linear relationship between pain scores and PDT.

Conclusion

Public awareness of AMI symptoms should be enhanced, in order to shorten PDT and improve AMI survival rates.

Introduction

Acute myocardial infarction (AMI) is a serious and life-threatening condition, characterized by an abrupt onset and a high mortality rate. Reperfusion therapy can decrease the death rate of AMI, ¹ but its effectiveness is strongly dependent on time, and it needs to be administered within 6 h of AMI onset. Life-threatening arrhythmias commonly occur within 2–4 h of AMI onset, and further increase the death rate. ² Therefore, the prehospital time in people experiencing AMI should be as short as possible, to provide the best chance of improving the overall survival rate of patients with AMI.^3,4 However, delays in receiving medical assistance occur in many patients with AMI because they are not aware that their symptoms require treatment. ⁵ If a patient realizes that his or her symptoms indicate an AMI, he/she is more likely to seek urgent medical attention, compared with someone who does not know what such symptoms might indicate. ⁶ Since the typical symptom – chest pain – does not occur in all patients with AMI, other (atypical) symptoms may mislead people into thinking their symptoms are due to other causes. In addition, although some patients know that their symptoms may be caused by AMI, they are unaware of the consequences of AMI ⁷ . These factors may protract the prehospital delay time (PDT). The purpose of the present study was to analyse the effects of AMI symptoms on PDT, to discover which patients receive the fastest AMI treatment.

Patients and methods

All study methods were approved by the Ethics Committee of the First Affiliated Hospital of Liaoning Medical University. All patients enrolled in the study gave written informed consent to participate.

Patients

The study participants were sequential patients who presented with AMI (diagnosed using Chinese guidelines 8 and who were hospitalized in The First Affiliated Hospital of Liaoning Medical University, Jinzhou, China, between January and October 2012. Patients with stable haemodynamics within 3 days of hospital admission, who had presented with AMI including ST-segment elevation and non-ST-segment elevation (with AMI diagnosed by electrocardiogram, coronary angiography and myocardial enzyme levels), and who were conscious and willing to participate, were included in this study. Those who were unable to communicate because of psychiatric illness, those who were unconscious and those whose condition was too critical to allow their participation were excluded.

Investigation methods

One-to-one communication between investigators and patients was used, so that investigators could answer any questions or problems raised by patients. Questionnaires were completed by the patients themselves or by their family members.

Research tools

Questionnaire

A 23-item questionnaire was designed by the investigators, based on other published resources, which underwent a validity analysis (performed by eight experts) to establish whether the questionnaire answered the questions posed by the study. Each item was scored on a five-point scale, with ‘5’ indicating very important and ‘1’ indicating very unimportant; validity for each item was established according to the number of experts who gave scores above 3/8. The validity score was calculated to be 0.86, which was the average validity score for all 23 items. A preliminary test in 15 patients indicated that the detection reliability (Cronbach’s α) of the questionnaire was 0.84.

The questionnaire was divided into three sections. The first section recorded descriptions of the patients’ symptoms and feelings. Symptoms included typical and atypical symptoms. Typical symptoms included chest compression pain or chest discomfort, radiating pain in the arms, shoulders or back, or dyspnoea. Atypical symptoms included nausea or vomiting, diarrhoea or abdominal pain, profuse sweating, dizziness, collapse or fainting and tiredness. Patients selected ‘yes’ or ‘no’ to answer these questions. The second section included questions relating to whether or not patients knew that their symptoms were caused by an AMI, and again, the patients selected ‘yes’ or ‘no’ to answer these questions. The third section explored the amount of pain the patients experienced, and was investigated with a visual analogue scale (VAS).

Visual analogue scale

Pain was evaluated with a VAS. A ruler marked between 1 and 10 in equal units, with ‘0’ indicating the patient was pain free and ‘10’ indicating they were experiencing intolerable pain, was used. Patients moved a marker on the ruler according to their feelings, and the corresponding values served as their pain scores. ⁹

Optimum time for reperfusion therapy

The optimum time for reperfusion therapy for AMI is within 6 h of AMI onset, thus, 6 h was used as the cut-off point for treatment delay.

Statistical analyses

Statistical analyses were performed with SPSS® software, version 19.0 (SPSS Inc., Chicago, IL, USA). As PDT, which is a continuous variable, showed a skewed distribution, it was changed into a normal distribution by logarithmic transformation and expressed as Ln (PDT). Student’s t-test was used to compare PDT data and χ²-test was used to analyse AMI symptom data. Pearson’s correlation coefficient was used to analyse PDT-related factors and linear regression was used to explore the relationship between pain scores and PDT. Statistical significance was established at P < 0.05.

Results

A total of 116 patients were enrolled in this study and completed the questionnaire: 84 (72.4%) were male and 32 (27.6%) female, mean age 64.1 ± 13.9 years.

The mean PDT was 7.3 ± 2.4 h and the median PDT was 2.2 h. Patients experienced a mean of 3.6 symptoms during their AMI attack. ‘Chest compression pain or chest discomfort’ was the most common category of symptom reported (Table 1).

Table 1.

Effect of various symptoms of acute myocardial infarction (AMI) on prehospital delay time (PDT) in 116 patients completing questionnaires on their AMI symptoms and general knowledge of the condition.

Chest compression pain/discomfort	Profuse sweating	Dyspnoea	Dizziness	Nausea or vomiting	Radiating pain	Diarrhoea or abdominal pain	Collapse orfainting	Tiredness
Patients affected, n (%)	79 (68.1)	71 (61.2)	59 (50.9)	12 (10.3)	39 (33.6)	43 (37.1)	3 (2.5)	5 (4.3)	8 (6.8)
Having symptoms Ln(PDT)*	1.533	1.618	1.426	1.779	1.875	1.806	2.084	1.900	1.589
Having no symptoms Ln(PDT)*	2.054	2.123	1.840	2.243	1.885	2.250	2.999	2.318	1.917
Statistical significance	P = 0.021	P = 0.029	P = 0.049	NS	NS	NS	NS	NS	NS

PDT: Prehospital delay time; AMI: acute myocardial infarction; NS: no statistically significant difference.

*

As PDT, which is a continuous variable, showed a skewed distribution, it was changed to a normal distribution by logarithmic transformation and expressed as Ln(PDT).

Student’s t-test.

The period of PDT was significantly shorter in patients experiencing chest compression pain or chest discomfort, profuse sweating or dyspnoea, compared with the period of PDT in patients experiencing other symptoms (P < 0.05) (Table 1).

Of the 116 patients, 84 (72.4%) had one or more typical symptoms (chest compression pain or chest discomfort, radiating pain in the arms, shoulders or back, or dyspnoea); 32 patients had only atypical symptoms (nausea or vomiting, diarrhea or abdominal pain, profuse sweating, dizziness, collapse or faintness, or tiredness). Patients were classified as having typical symptoms if they had typical and atypical symptoms, those classified as having atypical symptoms only had atypical symptoms, no typical symptoms. PDT was significantly shorter in patients with typical symptoms compared with atypical symptoms (P < 0.05; Table 2).

Table 2.

Effects of factors associated with acute myocardial infarction (AMI) symptoms on prehospital delay time (PDT).

Factor associated with AMI	Cases, n	Ln(PDT)*	t	Statistical significance
Having typical AMI symptoms	84	1.7270	2.519	P = 0.014
Having atypical AMI symptoms	32	2.1684
Understanding symptom is AMI	62	1.5802	4.974	P = 0.000
Not understanding symptom is AMI	54	2.4220
Pain score >6	87	1.5965	2.759	P = 0.018
Pain score ≤6	29	2.2753
There is history of alcohol	31	1.6051	1.799	NS
There is no history of alcohol	85	2.0383
Male	84	1.994	2.067	NS
Female	32	2.210

*

As PDT, which is a continuous variable, showed a skewed distribution, it was changed to a normal distribution by logarithmic transformation and expressed as Ln(PDT).

Student’s t-test.

The mean pain score in the 116 patients with AMI, as rated by the patients on a VAS, was 7.3 ± 2.4. PDT was significantly shorter in patients with pain scores >6 compared with those with pain scores ≤6 (P < 0.05; Table 2).

Of the 116 patients, 39 had had a previous AMI and 77 had not. Among those patients with a history of AMI, 13 still failed to make an accurate self diagnosis of their symptoms. Only 62 (53.4%) of the 116 patients were aware of AMI symptoms. PDT was significantly shorter in patients who were aware of AMI symptoms than in those who were unaware (P < 0.05; Table 2).

The cut-off point for treatment delay was 6 h. ² In the present study, 14 patients believed that their symptoms were not caused by AMI and treatment delay occurred in eight of these patients; 31 patients believed that their symptoms seemed to be AMI related and treatment delay occurred in six of these patients; 17 patients believed that their symptoms were caused by AMI and treatment delay occurred in five of these patients; finally, 54 patients did not understand what symptoms AMI produced, and treatment delay occurred in 32 of these patients. These results indicate that greater treatment delay occurred in patients who believed that their symptoms were not AMI symptoms, or who did not understand that the symptoms they were experiencing indicated an AMI. Time to treatment was shorter for patients who believed that their symptoms seemed to be (or certainly were) AMI-related (χ²= 15.197, P = 0.002).

The relationships between patients’ experiences and understanding of typical symptoms of AMI, and understanding that these symptoms are indicative of AMI, are shown in Figure 1. Similarly, Figure 2 provides information on the relationships between patients’ experiences and understanding of atypical symptoms of AMI. Chest pain was the symptom most widely understood (by 56 patients [48%]), although it occurred in far more patients (79; 68.1%). For other typical symptoms, more patients experienced radiating pain in the arms, shoulders or back than knew these were AMI symptoms. Likewise, more patients experienced dyspnoea, profuse sweating, nausea or vomiting, or dizziness than knew that these were AMI symptoms. Conversely, more patients knew that collapsing or faintness, or tiredness were AMI symptoms than experienced these symptoms (Figure 2).

Figure 1.

Relationship between patients experiencing typical acute myocardial infarction (AMI) symptoms and understanding that these symptoms are indicative of AMI, in 116 patients completing questionnaires on their AMI symptoms and general knowledge of the condition.

Figure 2.

Relationship between patients experiencing atypical acute myocardial infarction (AMI) symptoms and understanding that these symptoms are indicative of AMI, in 116 patients completing questionnaires on their AMI symptoms and general knowledge of the condition.

Pearson’s correlation coefficient test indicated that the agreement between patients actually having an AMI symptom and understanding that the symptom was an AMI was inversely correlated with PDT (correlation coefficient: R = 0.192, P = 0.039). Linear regression analysis indicated that there was a linear relationship between pain scores (independent variable, x) and PDT (dependent variable, y) with a linear equation: y = 3.098 − 0. 196 x (coefficient of determination: R²= 0.356, F = 27.114, P < 0.001).

Discussion

The efficacy of any therapy for AMI is time-dependent: generally, the sooner a patient receives treatment, the lower the death rate. ¹⁰ However, for most patients with AMI, there is a mean PDT of 1.5–6 h, and only one-third of patients see the doctor within 2 h of AMI onset. Consequently, the majority of patients lose the best time for AMI treatment.^11,12 The present study has shown that patients’ correct identification of AMI symptoms can shorten their PDT.

In our study, patients who had chest compression pain or chest discomfort, profuse sweating and dyspnoea were significantly more likely to receive timely medical treatment than those who had other symptoms. PDT was significantly shortened in patients with chest compression pain or chest discomfort, as this symptom is linked with heart disease, in many people’s minds. Patients generally paid more attention to potential heart disease symptoms and to substantial pain, compared with other symptoms that can be associated with AMI. ¹³

Profuse sweating was the most common atypical symptom reported in our study, and was the second most common presenting symptom. Most patients had never previously experienced profuse sweating, and, as it was unusual, went directly to hospital. Macinnes, ¹⁴ Goldberg ¹⁵ and Dracup¹⁶ reported that patients see a doctor as soon as possible when they believe their symptoms are unusual or severe.

Dyspnoea was strongly associated with a short PDT. Severe dyspnoea can lead to a reduction in blood oxygen saturation, development of brain hypoxia and a series of painful feelings; such symptoms mean that patients usually go to hospital without delay. ¹⁷ In our study, most patients had typical symptoms, including chest compression pain or discomfort and dyspnoea. Patients were less likely to think of heart disease when they had atypical symptoms, such as dizziness, profuse sweating, nausea or vomiting, diarrhoea or abdominal pain, tiredness, collapse or faintness. Health education about AMI should therefore be enhanced so that more patients know that AMI has typical and atypical symptoms and they should go to hospital immediately when either typical or atypical symptoms occur.

A strong association between PDT patients having AMI symptoms and understanding that their symptoms were indicative of an AMI has been reported. ¹⁸ In the present study, 56 (48%) of patients knew that chest pain was an AMI symptom and 79 patients (68.1%) had this symptom. However, for some atypical symptoms, the distribution between the patient actually experiencing a symptom and understanding that it is indicative of AMI was quite different. Nearly one third of patients had atypical symptoms without typical symptoms, and many patients did not realize that these were symptoms of AMI. Although the results of the correlation analysis were statistically significant, these findings can hardly be described as clinically significant because they account for little of the variability.

In this study, 39 of the 116 patients enrolled had a history of AMI, yet 13 of these 39 people still failed to make an accurate assessment of their AMI symptoms. Of the 77 study patients who had no AMI history, 57 (60.3%) were unaware of AMI symptoms. Their lack of knowledge of AMI meant that they lost the best time for AMI treatment. Therefore, increasing public AMI knowledge should shorten patients’ PDT and improve the survival rate of patients with AMI. Enhancing health guidance and popularizing disease knowledge should be undertaken, especially among high-risk populations (i.e. people aged >50 years old or those with a history of diabetes, hypertension, heart disease or smoking). The educational content should include typical and atypical symptoms of AMI, distinctions between coronary heart disease, angina pectoris and AMI, the causative factors of AMI, the early symptoms of AMI onset, the benefits of early treatment for AMI and the serious consequences of delaying treatment for AMI. The information should be disseminated face-to-face at patients’ bedsides, as written information on ward corridor walls and on electronic screens in outpatient areas.

In addition, the Community Service Centre can play an important role in popularizing AMI knowledge ¹⁹ by improving the health education ability of Community Service Centre staff and by collating medical records and contact information for high-risk residents in their jurisdiction. Staff may educate patients through face-to-face interviews or telephone contact, and by displaying written information in the district.

Although our study found that many factors, such as symptoms (typical versus atypical symptoms and level of pain) and awareness of AMI symptoms, were associated with PDT, some factors could not be controlled. Only awareness of AMI symptoms could be changed. Therefore, we should improve public awareness of heart disease and AMI symptoms as much as possible.