Test of the Acute Cardiac Ischemia Time-Insensitive Predictive Instrument (ACI-TIPI) for Prehospital Use,☆☆,,★★

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Abstract

Study objectives: To test diagnostic performance for acute cardiac ischemia (ACI) in a manually calculated and in a computerized, ECG-calculated ACI time-insensitive predictive instrument (ACI-TIPI) in prehospital chest pain patients. Methods: We carried out prospective inclusion and data acquisition with retrospective analysis. Over a 6-month period, 439 adult emergency medical services patients with chest pain underwent prehospital electrocardiography. Because of incomplete data, 77 cases were excluded, leaving a study sample of 362 patients. Excluded patients did not differ significantly with respect to age, sex, final diagnosis, or history of myocardial infarction, heart surgery, diabetes, or stroke. ACI-TIPI probabilities of ACI were computed on the basis of the prehospital ECGs as interpreted retrospectively and independently by two study investigators blinded to patient outcome, with a specially programmed electrocardiograph, and with a computer algorithm further modified by logistic-regression analysis. Results: Diagnostic performance on the basis of receiver operating characteristic (ROC) curve areas of the ACI-TIPI was scored, by the two physician readers, .73 and .74; and by ECG, .75. Patients with low ACI-TIPI probability (0% to 9%) had no acute myocardial infarctions, a 2.3% incidence of angina, and no prehospital life-threatening events. Conclusion: ACI-TIPI probabilities of ACI as generated by a specially programmed electrocardiograph are comparable to those based on physician ECG interpretations and may be useful in the prehospital evaluation of chest pain. [Aufderheide TP, Rowlandson I, Lawrence SW, Kuhn EM, Selker HP: Test of the acute cardiac ischemia time-insensitive predictive instrument (ACI-TIPI) for prehospital use. Ann Emerg Med February 1996;27:193-198.]

Section snippets

INTRODUCTION

Two acute cardiac ischemia (ACI) predictive instruments have been developed as diagnostic aids for hospital-based emergency physicians in the triage of patients with chest pain or other symptoms suggestive of acute ischemia. In 1984, Pozen et al1 developed a predictive instrument for ACI based on logistic regression for use in a handheld programmable calculator. This mathematic instrument provided an estimate of a patient's probability of having acute ischemia, based on seven clinical and ECG

MATERIALS AND METHODS

The Milwaukee County Paramedic System is a two-tiered urban emergency medical services system.7 For this study, all 10 Milwaukee County paramedic units were equipped with computerized, portable MAC PC 12-lead electrocardiographs (Marquette Electronics, Incorporated) coupled with cellular telephone transmission capability. The transmission of prehospital 12-lead ECGs has been demonstrated to be accurate and reliable.8

Prehospital 12-lead ECGs were acquired by Milwaukee County paramedics in phase

RESULTS

During a 6-month period (July 17, 1989, through January 1, 1990), the Milwaukee paramedics acquired and transmitted prehospital 12-lead ECGs for 439 adult prehospital chest pain patients. Seventy-seven patients (17%) were excluded because of incomplete data. Excluded patients did not differ significantly with respect to age, sex, final hospital diagnosis, or history of myocardial infarction, heart surgery, diabetes, or stroke. Excluded patients had a lower incidence of history of hypertension

DISCUSSION

Approximately 5 million patients present to EDs each year with chest pain or other symptoms suggesting acute ischemia.3 Approximately 50% of these patients are transported by EMS systems.6 Identifying the patients with true ACI (AMI or angina pectoris) is one of the most difficult challenges in emergency medicine.13 Physicians still rely mainly on the patient's presenting symptoms and ECG findings to determine initial patient disposition.14 Studies of emergency physicians demonstrate that they

Acknowledgements

The authors gratefully acknowledge and thank Paul Elko, Tony Holmes, and Marquette Electronics, Incorporated, for their valuable assistance; Michael H Milbrath, Judy E Larsen, Lauryl M Pukansky, and the Milwaukee County paramedics, without whose enthusiasm and dedication this project would not have been possible; Joni R Beshansky, RN, MPH, for her assistance in handling the ECGs and coding system for this study; and Dawn Kawa for her valuable assistance in preparing this manuscript.

References (25)

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    Impact of the acute cardiac ischemia time-insensitive predictive instrument (ACI-TIPI) on the speed of triage decision making for emergency department patients presenting with chest pain: A controlled clinical trial

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    • Pre-hospital 12-lead electrocardiography programs: A call for implementation by emergency medical services systems providing advanced life support - National Heart Attack Alert Program (NHAAP) Coordinating Committee; National Heart, Lung, and Blood Institute (NHLBI); national institutes of health

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      The same report (42) found that the acute cardiac ischemia time-insensitive predictive instrument (ACI-TIPI), which prints the patient’s probability of having ACS on the electrocardiogram header, improved the diagnosis of ACS. Further research is needed to test the potential impact of ACI-TIPI on EMS-based identification of ACS (55). Pre-hospital 12-lead electrocardiography acquisition has been shown to be feasible and to result in earlier identification of patients with STEMI (39,56–59).

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    From the Departments of Emergency Medicine* and Family and Community Medicine, Medical College of Wisconsin, and the Diagnostic Division, Marquette Electronics, Incorporated§, Milwaukee, Wisconsin; and the Division of Clinical Care Research, Tufts University School of Medicine, New England Medical Center, Boston, Massachusetts.

    ☆☆

    Dr Aufderheide acted as a consultant to Marquette Electronics in developing the Marquette version of the ACI-TIPI. He has no direct financial interest in the ACI-TIPI or in Marquette Electronics. Dr Selker developed the originial ACI-TIPI but has had no involvement with Marquette Electronics.

    Address for reprints: Tom P Aufderheide, MD, Department of Emergency Medicine, Medical College of Wisconsin, 8700 West Wisconsin Avenue, DH-204, Milwaukee, Wisconsin 53226

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    Reprint no. 47/1/70708

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