Symptom presentation in myocardial infarction, ambulance times and prehospital delay

Research output: ThesisDoctoral Thesis

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Abstract

Background
Early prehospital recognition of presenting symptoms of myocardial infarction (MI) is time-critical because reperfusion and medical therapies improve patient outcomes. Failure to recognize symptoms of MI may lead to longer delays in both prehospital and medical care. Some previous studies have identified that women are less likely to present with chest pain, however, findings from these studies have been inconsistent.

Aims
The aims of this doctoral research were fivefold: (1) to investigate if men and women present equally with chest pain as a symptom of MI and whether there were sex differences in other presenting symptoms of MI; (2) to determine if the symptoms reported during the emergency telephone call, in particular chest pain, and ambulance response times are the same for men and women with MI; (3) to determine if paramedic records, compared with hospital medical records, are a reliable source of information about presenting symptoms of MI and onset-time of symptoms; (4) to compare patient characteristics from the hospital medical records and patient outcomes for patients presenting with and without chest pain; and (5) to describe prehospital delay time for MI patients transported by ambulance and identify patient characteristics and presenting symptoms which contribute to prehospital delay for MI patients.

Methodology
To address aim 1, a systematic review and meta-analysis were conducted. Aims 2 to 5 were addressed by retrospective cohort studies of patients with an emergency department (ED) discharge diagnosis of MI, who were transported by ambulance to one of the seven metropolitan EDs in Perth, between January 2008 and October 2009. Symptoms of MI were transcribed from audio tapes of the emergency telephone call to the ambulance service and the text description in the paramedic patient care record (PCR). To validate the accuracy of the paramedic documentation of presenting symptoms and symptom onset-time of MI, the patients’ hospital medical records were reviewed at a single teaching hospital. The following statistical methodologies were employed: multivariable linear and logistic regression; McNemar tests; kappa and adjusted kappa statistics, sensitivity, specificity, and positive and negative predictive values; and Kaplan-Meier curves and Cox regression.

Results
Meta-analysis of 27 studies (1,654,588 patients) showed women with MI had lower odds (OR 0.63, 95% CI 0.59-0.68) and a lower rate (RR 0.93, 95% CI 0.91-0.95) of presenting with chest pain than men. Women were significantly more likely to present with fatigue, neck pain, syncope, nausea, right arm pain, dizziness and jaw pain.

In age-adjusted regression analyses of emergency calls to the ambulance service (n=1681), women were less likely than men to report chest pain (OR 0.70, 95% CI 0.57-0.88); and although ambulance times did not differ between men and women with chest pain, women with chest pain were less likely than men with chest pain to be allocated a priority 1 (lights and sirens) (OR 0.39, 95% CI 0.18-0.87) ambulance response.

In the comparison of paramedic PCRs with hospital medical records (n=400 pairs of records), the majority (71.4%) of 21 documented MI symptoms had adjusted Kappa statistics greater than 0.75, and observed agreement greater than 90%. For the symptom of chest pain, sensitivity, specificity, positive predictive value and negative predictive value were all greater than 85%. Where symptom onset-time was recorded in both the paramedic PCR and the hospital medical record (n=196 pairs of records), it agreed exactly in 60% of the records, and the times were within 30 minutes in over 80% of the records.

In the comparison of patient characteristics and survival outcomes for patients who presented with and without chest pain (n=382), the adjusted odds of presenting without chest pain were increased for women (OR 1.67, 95% CI 0.99-2.82), and patients aged 70-79 years (OR 4.33, 95% CI 1.50-12.5) and aged over 80 years (OR 7.54, 95% CI 2.81-20.3) compared with patients less than 60 years. The adjusted hazard (median follow-up time 2.2 years) of presenting without chest pain was not significantly associated with survival.

For patients with a recorded onset-time (n=829) median delay was 2.2 hours. Decreased delay was associated with age less than 70 years, presenting with chest pain, and diaphoresis. Increased delay was associated with being with a primary health care provider, if the patient was at home, and if the person who called the ambulance was anyone other than the spouse. For patients with onset-times recorded as word descriptions (n=174), 37% of patients delayed 1-3 days and 64% of patients described their symptoms as intermittent and/or of gradual onset.

Conclusions
This doctoral thesis contributes to the evidence about sex differences in symptoms of MI presentation: women were less likely to present with chest pain and more likely to present with other symptoms of MI. Women were also less likely to include the symptom of chest pain in their emergency telephone call to the ambulance service, as were older patients. Furthermore, it contributes to our knowledge of factors that affect prehospital delay: older age and presenting without chest pain or diaphoresis were associated with increased delay. Given that for MI the symptom of chest pain differs with age, between men and women, and prehospital delay times remain longer than is recommended, public awareness of symptoms, including education of health professionals, should be enhanced to reduce time from symptom onset to definitive care.
Original languageEnglish
QualificationDoctor of Philosophy
Publication statusUnpublished - 2015

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