Journal

of Electrocardiology

Vol. 25 Supplement

Electrocardiographic Phasing of Acute Myocardial Infarction

Stanley T. Anderson, MB,* Michelle Wilkins,? W. Douglas Weaver, MD,+ Ronald H. Selvester, MD,5 and Galen S. Wagner, MD+

Table 1.

The use of reperfusion therapy has been demonstrated to reduce the mortality rate from acute myocardial infarction (AMI), and a relationship has been established with the historical time from the onset of symptoms.’ The only additional, readily available clinical information that might assist in the early decision about reperfusion is the standard 12 -lead electrocardiogram (ECG). This study was undertaken to evaluate electrocardiographic recordings taken early after patient presentation with regard to changes that might indicate the stage of evolution of the infarct process. Utilizing paired ECGs from 154 patients with AM1 from the Myocardial Infarction, Triage and Intervention project2 at the University of Washington, Seattle, where thrombolysis was not given in the interval between tracings, a phasing system was designed.3,4 Phasing of the “acuteness” of the infarction process was based on ST elevation measured at the J point, the presence or absence of tall T waves (2 1 .O mV in precordial leads or 2 0.5 mV in the limb leads), T wave morphology, and the presence of abnormal Q waves, according to the initial version of the form in the Appendix. Each electrocardiographic lead with the exception of aVR was assigned a phase according to Table 1. The earliest phase of the prehospital electrocardiogram (ECGl) in any of the 11 leads was phase IA or 1B in 15 1 patients, was unchanged in the hospital electrocardiogram (ECG2) in 67% of patients, moved to a later phase in 3 I%, and moved to an earlier *From tFrom *From §From

Electrocardiographic Lead Phase Assignment

T Wave

Tall T

Positive T

Flat or Biphasic T

Negative T

Abnormal Q Absent Present

1A 2A

1B 2B

Don’t Know 3

Don’t Know 4

phase in 2% (Fig 1). Results were similar for both anterior and inferior infarction. To quantitate phase, a scoring system5 has been developed allocating 4 points for phase lA, 3 for lB, 2 for 2A, 1 for 2B, and 0 for all other phases. A total phasing score was estimated by adding the score of each of the 11 leads phased. Utilizing the phasing score and allowing for a variation of + 1 point, stability was present between ECGl and ECG2 in 32% Earliest Phase on ECG 1

Earliest Phase on ECG 2

Earliest Phase on ECG 1

Alfred Hospital, Melbourne, Australia. Duke University Medical Center, Durham, North Carolina. the University of Washington, Seattle, Washington. Memorial Hospital, Long Beach, California.

Reprint requests: Stanley T. Anderson, MB, Department of Cardiology, Alfred Hospital, Commercial Road, Prahran, Victoria 3 181, Australia.

Fig. 1. The percentage of change in the phases the prehospital and hospital ECGs.

3

between

4

Journal of Electrocardiology

Vol. 25 Supplement

60%

0%

Earliest Phase

Fig. 4. Comparison

of changes in phasing between ECGl and ECG2 with anterior and inferior infarction. There is a greater percentage of patients that had a zero score on the hospital ECG among those with inferior than with anterior infarcts. (A) Anterior; (B) Inferior.

m Increased a Unchanged a Decreased Fig. 2. Comparison of the percentage of change in the phases between the prehospital and hospital ECGs using the earliest phase and the phasing score.

OVL

Fig. 3. Serial ECGs in the panoramic display presentation from a patient with an acute anterior infarct.

I3

A

Score

I

-aVR

It

aVF

IU

n&L-A-&*-+

of patients, 55% showed a reduction in score, and 13% showed an increase (Fig. 2). The ECGs presented in Figure 3 show the progression of an anterior infarction over an interval of 43 minutes. The initial ECG (upper tracing) has ST-J elevation in leads VI-V5 with tall T waves in leads V3 and V4, positive T waves in leads VI, Vz, and V5, and a phasing score of 17 points. The subsequent ECG shows persistent ST-J elevation in leads VI-VT, persistent criteria for tall T waves in lead Vs, the T wave flattening (FT) in lead Vr and a phasing score of 13 points. This scoring system would appear superior to the use of the earliest phase in showing progression of the infarction process. Of interest, only 8% of patients with anterior infarcts progressed to a score of zero on ECG2 whereas 20% of patients with inferior infarcts progressed to zero on ECG2 (Fig. 4). This report presents the initial attempt to provide an electrocardiographic method for estimating the acuteness of the myocardial infarction process. Further modifications are being evaluated in both the qualitative and quantitative aspects of ECG phasing.

VI

v2

V3

V4

V5

V6

r 02.10

y&L

References 1. Gruppo Italian0 Per Lo Studio Della Streptokinasi Nell’Infarto Miocardio (GIS SI) : Effectiveness of intravenous thrombolytic treatment in acute myocardial infarction. Lancet 1:397, 1986 2. Weaver WD, Eisenberg MS, Martin JS et al: Myocardial Infarction, Triage and Intervention project-phase 1: patient characteristics and feasibility of prehospital initiation of thrombolytic therapy. J Am Co11 Card 15:925, 1990 3. Wagner NB, White RD, Wagner GS: The 12-lead ECG and the extent of myocardium at risk of acute infarction: cardiac anatomy and lead locations, and the phases of serial changes during acute occlusion. p. 3 1. In Califf RM, Mark DB, Wagner GS (eds): Acute coronary care in the Thrombolytic Era. Year Book Medical Publishers, Inc., Chicago, 1988 4. Pryor AD, Anderson ST, Pahlm 0 et al: Identification of the acuteness of myocardial injury/infarction by quantitative assessment of the changes in electrocardiographic waveforms. Circulation (in press) 5. Anderson ST, Wilkins M, Weaver WD et al: Quantification of electrocardiographic phase to assess acuteness of myocardial infarction. Circulation (in press)

Electrocardiographic

Phasing

of AMI

l

Anderson

et al.

5

Appendix ECG Phasing of Myocardial Infarction

Version one

Observer ECG ID No.

CHECK:

Time

Date ECG

Leads

reversed

RVH

mtssmg

LBBB ___

~

Severe

;

artifact

WPW _

RBBB

CmlrnV

Cal

baseline

Ventricular

-

60 Hz -

HR>llO

LVH

rhythm

DO NOT PROCEED FURTHER IF ANY OF THE ABOVE HAS BEEN CHECKED

STEP ONE: Check all leads in A. B. and C where stated criteria are met A. ST-Segment

elevation

0.1 mV measured

B. Tall T Waves

Z

Limb 2 0.5 mV

at J

C. Abnormal

Precordial

Q waves. Criteria from Selvester

QRS scoring

system.

In lead III check only if Q wave criteria met in aVF.

2 1.0 mV

point

I

VI

V4

I

VI

V4

I 2 30 ms

VI any

V4 2 20 ms

11

aVL

V2

VS

II

a!JL

V2

Vr

II 2 30 ms

aVL E 30 Ins

Vz any

VI 2 30 ms

III

aVF

V,

V6

III

aVF

V3

V6

III aVF 2 30 ms

aVF 2 30 ms

Vi any

V6 2 30 ms

STEP TWO: For each lead checked

in STEP ONE, enter T wave morphology

in D according

to definitions. D.

T Wave Morphology TT

= T t

1 .O mV in any precordial

PT

= Positive,

FT

= T < 0.05 mV either positive

EN

= Initial

2 0.05 mV, and not meeting

> 50% of T positive

MN = 2 50% of T negative

but terminal

I < 50% negative

2 0.05 mV

by 2 0.05 mV

Table: T Wave Absent Abnormal

TT criteria

or negative

STEP THREE: Enter phase in E according

* Meets criteria for 2B but without

VI

Va

II

aVL

V2

V,

III

aVF

V,

Vb

to table for each lead where an entry was made in STEP TWO

TT

PT

FUEN

MN

E. Phase

1A

1B

Don’t Know

Don’t Know

I

Q wave

Present

T Wave

Morphology

lead or t 0.5 mV in any limb lead

2A

ZB/Don’f Know*

ST elevation.

3

4

VI

Va

11

aVL

VZ

Vs

III

aVF

V>

Vh