CP series MEANS Physician Guide

MEANS Physicians Manual

Caution Federal US law restricts sale of the device identified in this manual to, or on the order of, a licensed physician. The information contained in this manual is subject to change without notice. No part of this manual may be photocopied, reproduced, or translated into another language without the prior written consent of Welch Allyn, Inc.

About this manual This manual documents the logic behind the diagnostic criteria provided by the Welch Allyn CP series interpretive resting ECG system. It is provided as a supplement to the electrocardiographs user's manual for those interested in or requiring knowledge of specific details of the system's algorithms. Please refer to the electrocardiographs general user's manual for information about use, installation and configuration, as well as applicable precautions and warnings. The algorithms employed in our system are collectively known as the Modular ECG Analysis System, MEANS. MEANS was developed by the Department of Medical Informatics at the Erasmus University of Rotterdam in the Netherlands. Portions of this manual are copyright © 1999 by the Department of Medical Informatics, Faculty of Medicine and Health Sciences, Erasmus University Rotterdam, P.O. Box 1738, 3000 DR Rotterdam, the Netherlands. The initial sections of this manual provide an overview of the general signal processing methodology involved, followed by detailed descriptions of the contour and rhythm analysis statement logic and in index to all statements. The final section provides an analysis of the performance of MEANS.

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Contents 1

INTRODUCTION ...4 1.1 1.2 1.3 1.4 1.5 1.6

2

CONTOUR ANALYSIS ...8 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10 2.11 2.12 2.13 2.14 2.15 2.16 2.17 2.18 2.19 2.20 2.21 2.22

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Signal conditioning...4 Pattern recognition ...5 Parameter extraction ...5 Diagnostic classification...6 Outline of the manual ...6 References ...7

Contour parameters...8 Dextrocardia and arm electrodes reversal ...10 Wolf-Parkinson-White syndrome (WPW)...10 Left Bundle Branch Block (LBBB)...11 Right Bundle Branch Block (RBBB) ...12 Incomplete Right Bundle Branch Block (IRBBB) ...13 Intraventricular conduction delay (IVCD) ...13 Atrial overload...14 Atrial abnormalities ...14 Axis deviations and fascicular blocks...15 Low QRS voltage...16 QT abnormalities ...16 Left ventricular hypertrophy (LVH) ...17 Right ventricular hypertrophy...18 Infarction...19 Pulmonary disease ...25 ST elevation...25 ST and T abnormalities ...26 Repolarization...27 Miscellaneous...28 Interaction of statements ...29 Combination of statements ...31

RHYTHM ANALYSIS ...32 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18

Introduction...32 Rhythm parameters ...33 Decision tree...34 Group 1: Rhythms with artificial pacemaker spikes ...37 Group 2: Non-dominant QRS complexes ...37 Group 3: Rhythms with atrial flutter or tachycardia ...43 Group 4: Regular rhythms with P/QRS ≤ 0.15 ...44 Group 5: Regular rhythms with 0.15<P/QRS≤1.0 and PR range > 60 ms ...45 Group 6: Regular rhythms with P/QRS > 1.0 and PR range ≤ 30 ms ...46 Group 7: Regular rhythms with P/QRS > 1.0 and PR range > 30 ms ...47 Group 8: Irregular rhythms with P/QRS ≤ 0.15 ...48 Group 9: Rhythms with paroxysmal acceleration or deceleration of ventricular rate...48 Group 10: Irregular rhythms with 0.15 < P/QRS ≤ 0.9 and PR range ≤ 30 ms...49 Group 11: Irregular rhythms with 0.15 < P/QRS ≤ 0.9 and PR range > 30 ms...50 Group 12: Irregular rhythms with 0.9 < P/QRS ≤ 1.2 and PR range > 30 ms ...51 Group 13: Irregular rhythms with P/QRS > 1.2 and PR range > 30 ms ...51 Group 14: Irregular rhythms with P/QRS > 1.0 and PR range ≤ 30 ms...52 Group 15: Rhythms with constant PR interval ...53

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STATEMENT INDEX...55

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THE PERFORMANCE OF MEANS ...60

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1 Introduction Computers and humans interpret ECG signals in fundamentally different ways. The principal difference is in the manner in which a computer “looks at” the signal. To be interpretable, a continuous (analog) signal must be converted into numbers, i.e., digitized. The signals are measured at short intervals, and the measured values (the samples) are stored as digital numbers. On this set of numbers the analysis must take place. The sampling must be dense enough to ensure sufficient fidelity in rendering the original analog signal. Current standards for ECG recording recommend a sampling rate of 500 Hz or higher. After collection of the data, the processing follows a number of successive stages: • • • •

Signal conditioning Pattern recognition Parameter extraction Diagnostic classification

Each of these steps must be performed correctly to ensure a satisfactory final result. If, for instance, the signals are not correctly cured of disturbances this may result in a faulty waveform recognition. The diagnostic classification is then likely to come out wrong. The successive steps will now be discussed more extensively.

1.1 Signal conditioning The ECG signal can be disturbed in several ways: •

Continuous noise of a single frequency, sometimes with higher harmonics, due to 50 or 60 HzAC mains interference.

•

Drift: more or less gradual baseline shifts, e.g., caused by respiration.

•

Bursts of noise of mixed frequencies and various amplitudes due to electrical signals from active muscles.

•

Sudden baseline jumps due to changes in electrode-skin impedance.

•

Spikes: isolated, large amplitude variations of short duration.

•

Amplitude saturation of the signal.

To correct these disturbances, several techniques have been used. Mains interference is suppressed by an adaptive filter that estimates the coming noise estimates and subtracts the estimates from the encountered signal. Baseline shift is corrected by simply connecting the onsets of successive QRS complexes by straight lines and determining the signal amplitudes with respect to these line segments. Beat selection and averaging (see below) help to reduce disturbances of muscle noise. If a disturbance is detected that may affect the diagnostic classification, the program issues a warning.

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1.2 Pattern recognition This part deals with the analysis of the various waveforms. First of all, the QRS complexes must be detected. No other waves or artifacts should be labeled as such. The intervals between QRS complexes are measured and stored. After all QRS complexes have been detected, they are typified, i.e., a comparison is performed that gives rise to classes of similar QRS complexes. Often there is only one type of QRS complex. If there are more, the “ordinary,” “representative” or “dominant” one is established; the others are “extraordinary” or “nondominant”. Mostly, the number of dominant complexes in a recording is larger than that of the non-dominant ones. In special cases this may not be true. In bigeminy their number may be equal to that of the non-dominant complexes, or be one less or one more, depending on when the recording starts and stops. If runs of tachycardia occur, the unusual complexes in a recording may even outnumber the dominant ones. The second step is to search for atrial activity. Both P waves and flutter waves can be detected, when present. PP and PR intervals are also measured and stored for use in the rhythm analysis. The third step is to mutually compare the ST-T segments of the dominant complexes. For the calculation of the averaged complex, only complexes are selected that have not only similar QRS, but also similar ST-T. In this way complexes that are disturbed by spikes or sudden baseline jumps are discarded. For the morphological analysis, the selected dominant P-QRS-T complexes are averaged into one complex. The main advantage of averaging is to improve the signal-to-noise ratio. Noise is random and, in the averaging, the positive and negative oscillations will cancel out. An additional advantage is that the analysis now has to be performed only once, i.e.on a single representative complex. It may occur that in the averaged complex a P wave appears which was not consistently detectable in the rhythm analysis, or vice versa. The final step in the pattern recognition process is the determination of the zero level in the representative P-QRS-T complex and the identification of the points of onset and offset of P, QRS, and T. The zero level is determined for the averaged complex per lead in an interval preceding the onset of the QRS complex. Onsets and offsets however are determined simultaneously over all leads together.

1.3 Parameter extraction After the onset and end points of P, QRS and T waves have been established, the relevant parameters can be measured to provide the input for the diagnostic logic. Besides amplitudes and durations, other measurements such as surface areas under the signal are derived. Most measurements are made on the averaged complex in each lead separately (e.g., R amplitude, Q duration), but some are derived taking all leads in account (e.g., overall QRS duration, PR interval). These durations are generally longer than one would measure by hand in individual leads or lead groups since the first onset in any lead and the last offset are taken into account.

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1.4 Diagnostic classification The diagnostic logic operates on the parameters and produces both a rhythm classification and a contour or morphology classification. The criteria used by the computer may differ from the criteria used in the ECG textbooks. The basic reason is that a human observer is inaccurate but flexible and creative, a computer precise and obedient but rigid in its operation. There are several specific reasons why ECG criteria in the program may differ from the conventional ones. First of all, of course, there is no uniformity of criteria in the literature. Then, criteria may be based on inaccurate measurement by eye. Also, ECG measurements may be “falsified” for the ease of the reader: axis calculations are generally made from the amplitudes of QRS complexes rather than from the surface areas under the QRS tracings as prescribed by theory. Further, criteria are sometimes not quantitatively defined (How flat must a flat ST-T be? How slurred is a slurred QRS upstroke?) or their measurement is not unequivocally prescribed. For the computer program to work, a quantitative definition must somehow be decided upon. Moreover, conventional criteria may have been based on measurements produced by technically outdated instrumentation. The amplitudes of R waves have been consistently underestimated, especially in children, due to filtering effets by too low frequency response of the electrocardiographs. Finally, a human interpreter may deviate from strict criteria as he sees fit: sometimes criteria have been made to meet a priori expectations. In one respect, the computer is inferior to the human observer: although the computer can measure very accurately, its powers of pattern recognition are inferior. For instance, it will have great trouble in detecting a P wave buried in a ST segment which is easily seen by the human eye.

1.5 Outline of the manual The following of this manual consists of two main parts. One part describes the diagnostic criteria that are employed in the contour classification of the Modular ECG Analysis System (MEANS), the other describes the criteria used in the rhythm classification of MEANS. Each part contains a brief introductory section, a description of the measurements that are used in the diagnostic logic, and a comprehensive list of statements and corresponding diagnostic criteria. Related statements have been grouped in sections, e.g., all statements related to intraventricular conduction delay, left ventricular hypertrophy, etc. Finally, an index of the statements that can be generated by the program is provided. A general format is used to specify the diagnostic criteria. The statement is given first, followed by one or more conditions that must be fulfilled for the statement to be issued by the program. Multiple conditions are combined with the use of logical “and” and “or” connectives, binding the (combinations of) conditions that have the same level of indentation. For example: Say: if: or or and

“probable inferior infarct” Q duration ≥ 40 ms and 0.2 ≤ Q/R ratio < 0.3 in aVF 30 ≤ Q duration < 40 ms and Q/R ratio ≥ 0.3 in aVF Q duration in aVF ≥ 20 ms Q duration ≥ 50 ms and Q amplitude > 300 µV in III

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1.6 References In several publications, the program structure and signal analysis part of MEANS have been described. One publication, which also provides many references for further reading, is: •

Van Bemmel JH, Kors JA, Van Herpen G. Methodology of the modular ECG analysis system MEANS. Methods Inf Med 1990;29:346-53.

The measurement and classification parts of MEANS have extensively been evaluated, both by the developers themselves and by independent observers. A major evaluation study in the field of automated electrocardiography has been the project Common Standards for Quantitative Electrocardiology (CSE), in which about 15 ECG computer programs from all over the world have participated. The CSE study consisted of two parts, one pertaining to the measurement part of the ECG programs, the other to the diagnostic classification part. Two key references are: •

Willems JL, Arnaud P, Van Bemmel JH, Bourdillon PJ, Degani R, Denis B, et al. A reference database for multi-lead electrocardiographic computer measurement programs. J Am Coll Cardiol 1987;10:1313-21.

•

Willems JL, Abreu-Lima C, Arnaud P, Van Bemmel JH, Brohet C, Degani R, et al. The diagnostic performance of computer programs for the interpretation of electrocardiograms. N Engl J Med 1991;325:1767-73.

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2 Contour analysis 2.1 Contour parameters All parameters that are used in the diagnostic criteria of the contour classification are measured in the representative P-QRS-T complex. The lead-independent, overall parameters are presented in Table 1. Table 1. Lead-independent parameters for the contour classification. Name Heart rate P axis P duration PR interval QRS axis QRS duration Corrected QT interval

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Description Ventricular rate (in beats per minute, bpm) Axis of the P wave (in degrees, from –180 to 180) Duration of the P wave (in ms) Duration of the PR interval (in ms) Axis of the QRS complex (in degrees, from −180 to 180) Duration of the QRS complex (in ms). QT interval corrected for heart rate according to Bazett’s formula: QTc = QT * √ (HR/60) (in ms)

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The parameters that are computed for each lead separately, are shown in Table 2. All amplitudes are taken as absolute values. Table 2. Lead-dependent parameters for the contour classification. Name Delta wave Negative J amplitude Positive J amplitude Negative P amplitude Positive P amplitude P notch Q amplitude Q duration negative QRS amplitude positive QRS amplitude top-top QRS amplitude QRS area

Q/R ratio QS pattern R amplitude R duration R notch R′ amplitude R/S ratio S amplitude S duration S′ amplitude ST slope Negative T amplitude Positive T amplitude

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Description Slurring of the initial part of the QRS complex. Amplitude of a negative J point (in µV). Amplitude of a positive J point (in µV). Amplitude of the negative deflection of the P wave (in µV). Amplitude of the positive deflection of the P wave (in µV). Notch in the positive deflection of the P wave Maximum amplitude of the Q wave (in µV). Duration of the Q wave (in ms). Amplitude of the largest negative deflection of the QRS complex (in µV). Amplitude of the largest positive deflection of the QRS complex (in µV). Amplitude of largest positive plus largest negative deflections of the QRS complex (in µV) Area under the positive deflections of the QRS complex minus area under the negative deflections of the QRS complex (in mVms). Ratio of the maximum amplitudes of the Q and R waves. QRS complex consisting of a Q wave only. Maximum amplitude of the R wave (in µV). Duration of the R wave (in ms). Notch in the positive deflection of the QRS complex. Maximum amplitude of the R′ wave (in µV). Ratio of the maximum amplitudes of the R and S waves. Maximum amplitude of the S wave (in µV). Duration of the S wave (in ms). Maximum amplitude of the S′ wave (in µV). Slope of the ST segment (in µV/100 ms). Amplitude of the negative deflection of the T wave (in µV). Amplitude of the positive deflection of the T wave (in µV).

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2.2 Dextrocardia and arm electrodes reversal Skip tests if: QRS area in I > 0 or top-top QRS amplitude in I ≤ 150 µV or positive T wave in I or −100 ≤ P axis ≤ 100° Say: if:

“dextrocardia” top-top QRS amplitude in V6 ≤ 500 µV

Say: if:

“arm electrodes interchanged” top-top QRS amplitude in V6 > 500 µV

If either test passed, no further contour analysis is performed.

2.3 Wolf-Parkinson-White syndrome (WPW) The presence of delta waves is a necessary condition for the diagnosis of WPW. The length of the PR interval is another obvious parameter to use. However, it is not a necessary criterion, for if the accessory pathway is slowly conducting, the PR interval could be normal. Moreover, WPW can occur in the absence of P waves, for example in the presence of atrial fibrillation. For this reason this criterion has not been used to construct the diagnosis of WPW, but has only to distinguish between LBBB and WPW type B in case both diagnoses have been made (see section LBBB). Say: if: and and

“WPW” delta waves in at least 2 extremity leads delta waves in at least 2 precordial leads QRS duration > 100 ms

If test WPW passed, only a test for LBBB is performed.

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2.4 Left Bundle Branch Block (LBBB) The primary condition for the diagnosis of a complete block is prolonged QRS duration. In the program the limit is 130 ms. The normal initial QRS activity to the right and anterior is smaller than normal or absent. Soon after the beginning of QRS the electrical forces turn posteriorly, and somewhat to the left and mostly horizontally. The predominantly posterior activity produces generally deep S waves in V1 and V2 while the R waves in V5 and V6 tend to remain low. Therefore, the program requires r waves in V1 and V2 to be minor (they even may be lacking, and in V5 and V6 q’s must be reciprocally absent). This is expressed by the requirement of a nett negative area and R/S ratio of less than 1/3 in V1. The R waves in V5 and V6 will have a delayed intrinsicoid deflection. Septal infarction should not be diagnosed in the presence of LBBB. Finally, if LBBB and WPW both come into consideration the case is decided by the duration of the PR interval. Skip tests if: Q wave in any of I, V5, V6 or QRS duration ≤ 130 ms Say: if:

“LBBB” and

or and and and Say: if: or

if: and and and then:

QRS area in V1 < −100 mVms S amplitude in V6 ≤ 1000 µV −100 ≤ QRS area in V1 < −40 mVms negative QRS amplitude > 3 times positive QRS amplitude in V1 QRS area > 0 in V6 intrinsicoid deflection at ≥ 50 ms in V5 or V6

“possible LBBB” QRS area in V1 < −100 mVms and S amplitude in V6 > 1000 µV −100 ≤ QRS area in V1 < −40 mVms and negative QRS amplitude > 3 times positive QRS amplitude in V1 and QRS area > 0 in V6 and intrinsicoid deflection at < 50 ms in V5 and V6 or QRS area ≤ 0 in V6 and intrinsicoid deflection at ≥ 50 ms in V5 or V6 test LBBB passed test WPW passed QRS area in V1 ≤ −5 mVms 0 ≤ QRS axis ≤ 90° Say: if:

“possible LBBB” “possible WPW” PR interval > 140 ms

suppress: if:

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“LBBB” PR interval ≤ 140 ms

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2.5 Right Bundle Branch Block (RBBB) The ECG abnormality in RBBB consists of a late, protracted QRS activity to the right and anterior with concomitant overall increase of QRS duration (≥ 130 ms). The program therefore looks for a late R, an R′ or a broad notched R wave in V1 or V2, all with delayed intrinsicoid deflection, and reciprocal broad S waves in the lateral leads. The QRS axis has a certain influence on the S duration in lead I. Lead I, although horizontal in geometrical space, is tilted upward on the left side in electrical space. In left axis deviation, this will result in a projected S wave which is less deep and of shorter duration than the S wave in V5 or V6, leads that are tilted downwards on the left. This aspect has been taken into account for the criteria on the S duration. In the presence of RBBB, a diagnosis of RVH may also be entertained if the R wave in V1 is tall. Skip tests if: QRS duration < 130 ms or S′ amplitude in V1 ≥ 100 µV Say: if:

“RBBB” and

or and and

if: and then:

S duration ≥ 50 ms in I, V5, V6 intrinsicoid deflection at ≥ 55 ms in V1 or V2 S duration ≥ 30 ms in V5 or V6 S duration in I ≥ 20 ms and QRS axis < −45° or S duration in I ≥ 30 ms and QRS axis ≥ 45° R′ wave or R notch in V1 or V2 or Q wave and intrinsicoid deflection at ≥ 50 ms in V1

test RBBB passed Q amplitude > 100 µV in V1 and V2 Say: if:

“septal infarct” Q duration ≥ 30 ms in V1 or V2

Say: if:

“probable septal infarct” Q duration ≥ 20 ms in V1 or V2

Suppress “RBBB” if: Q amplitude in V2 ≤ 100 µV or R amplitude in V2 < 200 µV or intrinsicoid deflection in V2 at < 50 ms if: then: Say: if: and

test RBBB passed “posterior infarct” positive QRS amplitude in V1 ≥ 1500 µV positive T amplitude in V1 ≥ 700 µV

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2.6 Incomplete Right Bundle Branch Block (IRBBB) For IRBBB comparable conditions apply as for RBBB but QRS duration is less increased (between 110 and 130 ms) and the intrinsicoid deflection time is shorter. Skip tests if: QRS duration ≥ 130 ms or QRS duration ≤ 110 ms or S′ amplitude in V1 ≥ 100 µV Say: if: or or

“incomplete RBBB” R′ amplitude ≥ 300 µV in V1 or V2 R′ in V1 and positive P wave in V1 S duration ≥ 40 ms in I, V5, V6 and intrinsicoid deflection at ≥ 45 ms in V1 or V2

2.7 Intraventricular conduction delay (IVCD) Only in the absence of diagnosable RBBB, LBBB or WPW will a statement of intraventricular conduction delay be made. The delay can be classified in different grades of severity. Say: if:

“slight intraventricular conduction delay 112 ms ≤ QRS duration < 126 ms

Say: if:

“moderate intraventricular conduction delay” 126 ms ≤ QRS duration < 140 ms

Say: if:

“marked intraventricular conduction delay” 140 ms ≤ QRS duration < 180 ms

Say: if:

“very marked intraventricular conduction delay” QRS duration ≥ 180 ms

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2.8 Atrial overload The diagnosis of right or left atrial overload (RAO and LAO) will be considered in the presence of a normal P axis. Otherwise an unusual P axis will be reported. In LAO the P wave is characterized by a broad negative terminal part in lead V1 and increase of overall duration. In RAO a tall P wave in lead II and aVF and/or in V1 and V2 is expected. In diagnosing RAO an adjustment has been built in for heart rate: in tachycardia the amplitude of the P wave has to be slightly higher to qualify for the diagnosis, than with normal heart rate. The reason for this adjustment is the superposition of the P on the preceding U wave or T wave occurring at higher heart rates. Above 130 bpm no attempt is made to diagnose RAO. Skip tests if: P axis ≤ −30° or P axis > 100° Say: if: and

“left atrial overload” negative P amplitude in V1 ≥ 180 µV P duration > 135 ms or LVH test passed

Say: if:

“right atrial overload” heart rate < 100 bpm and positive P amplitude ≥ 275 µV in V1 or V2 or positive P amplitude in II + positive P amplitude in aVF ≥ 525 µV 100 ≤ heart rate < 130 bpm and positive P amplitude ≥ 300 µV in V1 or V2 or positive P amplitude in II + positive P amplitude in aVF ≥ 575 µV

or

2.9 Atrial abnormalities Say: if: or

“unusual P axis” P axis ≤ −30° P axis > 100°

Say: if: and

“intra-atrial conduction delay” P duration > 135 ms negative P amplitude in V1 ≤ 180 µV

Say: if: and

“high P voltage” test RAO did not pass positive P amplitude ≥ 275 µV in any lead and heart rate < 100 bpm or positive P amplitude ≥ 300 µV in any lead and 100 ≤ heart rate < 130 bpm

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2.10 Axis deviations and fascicular blocks Axis deviations are distinguished in vertical, right, marked right and extreme right inferior on the one hand and horizontal, left, marked left and extreme right superior on the other hand. Besides a complete LBBB it is also possible to find a left anterior or posterior fascicular block (LAFB or LPFB). These statements will always be tested in combination with an axis deviation. (LPFB can only be diagnosed in conjunction with RBBB.) In the presence of inferior infarction no statement of left axis deviation is given, it being due to initial negativity in the inferior leads. In the presence of LBBB the axis tends to deviate to the left. Therefore the threshold for stating left axis deviation is increased. Moreover, the diagnosis of complete LBBB takes precedence over that of left anterior fascicular block. Say: if:

“vertical axis” 80 < QRS axis ≤ 100°

Say: if:

“right axis deviation” 100 < QRS axis ≤ 120°

Say: if:

“marked right axis deviation” 120 < QRS axis ≤ 150°

Say: if:

“extreme right inferior axis deviation” 150 < QRS axis ≤ 180°

Say: if: and

“consistent with LPFB” 120 < QRS axis ≤ 180° RBBB

Say: if:

“horizontal axis” −30 ≤ QRS axis < −10°

if: then:

test LBBB did not pass

if: then:

Say: if:

“left axis deviation” −60 ≤ QRS axis < −30°

Say: if:

“marked left axis deviation” −120 ≤ QRS axis < −60°

Say: if:

“extreme right superior axis deviation” −180 ≤ QRS axis < −120°

Say: if: and and

“consistent with LAFB” −120 ≤ QRS axis < −45° S amplitude in III > 500 µV S amplitude in III < S amplitude in II

test LBBB passed Say: if:

“left axis deviation” −120 ≤ QRS axis < −45°

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2.11 Low QRS voltage Say: if:

“low QRS voltage in extremity leads” top-top QRS amplitude ≤ 500 µV in all extremity leads

Say: if:

“low QRS voltage in precordial leads” top-top QRS amplitude ≤ 1000 µV in all precordial leads

Say: if:

“low QRS voltage” both previous tests passed

2.12 QT abnormalities The QT interval is measured from the beginning of the Q wave until the end of the T wave. In the case of intraventricular conduction delay, the excess QRS duration (>106 ms) is subtracted from the measured QT. A correction is made for the heart rate, using Bazett’s equation: corrected QT interval = QT interval * √(heart rate/60). The corrected QT interval renders the QT interval for a standard heart rate of 60 beats per minute. The upper limit of 470 ms is, in case of infarct, increased to 500 ms. Skip tests if: WPWB and QRS duration < 126 ms or heart rate ≥ 110 bpm Say: if:

“short QT interval, consider hypercalcaemia” corrected QT interval < 330 ms

Say: if:

“long QT interval, consider hypocalcaemia or quinidine-like drug” corrected QT interval ≥ 470 ms and no infarct test passed corrected QT interval ≥ 500 ms and any infarct test passed

or

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2.13 Left ventricular hypertrophy (LVH) The diagnosis of LVH rests on three types of parameters: voltage, shape, and repolarization. For each parameter, points are accumulated according to its degree of abnormality. The higher the score, the higher the overall grading of the LVH. The following gradations are distinguished, in which severity and probability go together: “consider”, “possible”, “probable”, “definite”, “pronounced”, and “very pronounced”. The voltage is determined in both the horizontal and frontal planes, but only the plane with the highest score will be used in the classification. For the horizontal plane the voltages are measured in leads V1, V5 and V6. In the frontal plane leads I and II are used. If the voltage in either plane does not meet the criteria, no further analysis for diagnosing LVH will be done. In both planes an adjustment has been made for age. At age 35 no correction is applied, at age 90 a maximal correction of about 6 mm in the precordial measurement and of 3 mm in the frontal plane is added to the measured voltage. For people younger than 35 years the adjusted voltage will be lower than the calculated voltage, for older people the opposite applies. The shape of the QRS complex is determined in that plane where the highest voltage score is reached. The main parameters on which the shape score is based are the intrinsicoid deflection and the sequence of small r waves in the right and tall R waves in the left precordial leads. In the category repolarization the program tests for the presence and degree of ST depression and T negativity in the leads I, II, aVL, aVF, V5, and V6. Strain scores in the frontal and horizontal planes are determined using the ST slope and the J- and T-wave amplitudes.

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2.14 Right ventricular hypertrophy The diagnosis RVH is not subdivided in such an elaborate way as LVH is. A distinction between probable and definite can be made. Presence of left or right atrial overload helps to make the diagnosis of RVH, because it provides circumstantial evidence. In the presence of RBBB, IRBBB or posterior infarction, the program may issue a statement that RVH is still to be considered. A more definite statement of RVH is ruled out, to prevent too much over-diagnosing. Skip tests if: QRS duration ≥ 160 ms or QRS axis ≤ 0° or test RBBB passed or test LBBB passed Say: if:

“RVH” and

or and and and and Say: if:

or

or

or

Say: if:

or

or

R/S ratio ≥ 1 in V1 and Q/R ratio ≤ 1 in V1 positive QRS amplitude in V1 ≥ 500 µV and positive T amplitude < negative T amplitude in V1 and V2 or positive QRS amplitude < S amplitude in V5 or V6 or QRS axis ≥ 100° and LAO or RAO QRS axis ≥ 120° R amplitude < S amplitude in II S amplitude in aVF ≤ 200 µV S duration in aVF < 40 ms tests for high-lateral, lateral, and inferior infarcts did not pass

“probable RVH” Q/R ratio ≤ 1 and R/S ratio ≥ 1 in V1 and positive QRS amplitude in V1 ≥ 1500 µV and positive T amplitude in V1 < 700 µV Q/R ratio ≤ 1/2 and R/S ratio ≥ 2 in V1 and positive QRS amplitude in V1 ≥ 300 µV and positive T amplitude < negative T amplitude in V1 or positive QRS amplitude < S amplitude in V5 or V6 QRS axis ≥ 80° and positive T amplitude < negative T amplitude in V1 and V2 and positive QRS amplitude < S amplitude in V5 or V6 and S amplitude in aVF ≤ 200 µV and S duration in aVF < 40 ms and test for lateral infarct did not pass QRS axis ≥ 100° and LAO or RAO “consider RVH” test RBBB passed and QRS axis ≥ -45° and positive T amplitude < negative T amplitude in V2 test IRBBB passed and positive QRS amplitude in V1 ≥ 500 µV and positive QRS amplitude > negative QRS amplitude in V1 test posterior infarct passed and QRS axis > 100°

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MEANS Physicians Manual

2.15 Infarction This section of the program classifies an infarction according to location and estimates the probability of its presence. The diagnosis of infarction is largely based on the presence and duration of Q waves, Q/R ratios, and QS patterns. T and ST abnormalities are used in statements on the age of the infarct (see section Repolarization). The location of the infarction is determined by the leads in which the abnormalities are found. The program distinguishes six locations: septal (lead V1, V2), anterior (V3, V4), lateral (V5, V6), high lateral (I, aVL), inferior (aVF, III), and posterior (V1, V2). Lead II may be involved in inferior infarction as well as in lateral infarction. Combined and more extensive infarcts will generate infarct statements for more than one location (see section Combination of statements). Four degrees of probability are distinguished: “definite”, “probable”, “possible”, or “consider”. Criteria on which a diagnosis of infarction has been made can also lead to other diagnoses, like LBBB, RBBB, LVH and RVH. The choice between these possible diagnoses is based on exclusion logic in the program and in some situations probabilities are adapted or criteria are tightened.

Inferior infarction An abnormal Q wave must be found in aVF and either II or III to even consider the diagnosis of inferior infarction. As a rule the Q wave in aVF is shallower and shorter than that in III. Its threshold to qualify as an infarct Q can therefore be lower. Inferior infarction may produce a left (i.e., superior) axis deviation if one only considers the ratio of upward and downward forces. In inferior myocardial infarction, however, this ratio is shifted due to initial negativity (Q in aVF) whereas in ordinary left axis deviation it is associated with deepening of the S wave in aVF. Skip tests if: Q amplitude + R amplitude in aVF < 200 µV or Q amplitude in aVF ≤ 100 µV or Q amplitude in II ≤ 70 µV and Q amplitude in aVF ≤ 70 µV or Q amplitude in III ≤ 100 µV Say: if:

“inferior infarct” Q duration ≥ 40 ms and Q/R ratio ≥ 0.3 in aVF

Say: if: or or

“probable inferior infarct” Q duration ≥ 40 ms and 0.2 ≤ Q/R ratio < 0.3 in aVF 30 ≤ Q duration < 40 ms and Q/R ratio ≥ 0.3 in aVF Q duration in aVF ≥ 20 ms and Q duration ≥ 50 ms and Q amplitude > 300 µV in III

Say: if: or

“possible inferior infarct” 30 ≤ Q duration < 40 ms and 0.2 ≤ Q/R ratio < 0.3 in aVF 20 ≤ Q duration < 30 ms and Q/R ratio ≥ 0.3 in aVF and Q duration in III ≥ 40 ms Q duration in aVF ≥ 20 ms and 40 ≤ Q duration < 50 ms and Q amplitude > 300 µV in III

or

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MEANS Physicians Manual

Septal infarction Say: if: or or

“septal infarct” Q duration ≥ 35 ms and Q/R ratio ≥ 1/3 in V1 or V2 Q duration ≥ 40 ms and Q amplitude > 100 µV in V1 or V2 QS pattern in V2 and R amplitude in V1 ≥ 70 µV or QS pattern in V3 or Q duration in V3 ≥ 25 ms or Q wave and R amplitude < 250 µV and R duration < 26 ms in V3 or R amplitude < 200 µV and R duration < 16 ms in V3

Say: if: or or or

“probable septal infarct” 25 ≤ Q duration < 35 ms and Q/R ratio ≥ 1/3 in V2 or V3 35 ≤ Q duration < 40 ms and 1/4 ≤ Q/R ratio < 1/3 in V2 or V3 Q duration ≥ 30 ms and R amplitude ≥ 200 µV in V2 R amplitude in V2 < 150 µV and R amplitude in V2 < R amplitude in V1 − 50 µV and R duration in V2 ≤ R duration in V1 or Q duration in V3 ≥ 25 ms

Say: if: or

“possible septal infarct” 25 ≤ Q duration < 35 ms and 1/4 ≤ Q/R ratio < 1/3 in V1 or V2 QS pattern and R amplitude < 70 µV in V1 and QS pattern in V2 and test LVH did not pass QS pattern or R amplitude < 70 µV in V1 and Q amplitude < S amplitude and R amplitude < S amplitude in V2 and test LVH did not pass

or

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