STEMI vs. STE-Mimic Thompson 2 Electrode placement

V1 – 4th Intercostal space, right parasternal

V2 – 4th Intercostal space, left parasternal

V3 – Directly between V2 & V4

V4 – 5th Intercostal space, left mid clavicular

V5 – Anterior axillary line, lateral to V4

V6 – Mid axillary line, lateral to V5

* Electrodes should be placed on a bare torso,

with points of contact free of hair or moisture.

STEMI vs. STE-Mimic Thompson 3 The presence of artifact makes it very difficult to appropriately interpret a 12-lead ECG.

While it may be nearly impossible to mitigate all artifacts, steps should be taken to assure

the cleanest tracing possible. Above is a table that describes which electrode is causing

the problem.

The Culprit Electrode

Leads with artifact Electrode

Precordial Leads Check the associated electrode

Leads I & II Check the Right Shoulder electrode

Leads I & III Check the Left Shoulder electrode

Leads II & III Check the Left Leg electrode

STEMI vs. STE-Mimic Thompson 4

Contiguous Leads

Precordial Leads Limb Leads

Right Left I

High Lateral

aVR V1

Septal

V4

Anterior

II

Inferior

aVL

High Lateral

V2

Septal

V5

Low Lateral

III

Inferior

aVF

Inferior

V3

Anterior

V6

Low Lateral

STEMI vs. STE-Mimic Thompson 5 ECG – 1 ECG – 2

STEMI vs. STE-Mimic Thompson 6 ECG – 3 ECG – 4

STEMI vs. STE-Mimic Thompson 7 ECG – 5 ECG – 6

STEMI vs. STE-Mimic Thompson 8 ECG – 7 ECG – 8

STEMI vs. STE-Mimic Thompson 9 ECG – 9 ECG – 10

STEMI vs. STE-Mimic Thompson 10 ECG – 11 ECG – 12

STEMI vs. STE-Mimic Thompson 11 ECG – 13 ECG – 14

STEMI vs. STE-Mimic Thompson 12 ECG – 15 ECG – 16

STEMI vs. STE-Mimic Thompson 13 ECG – 17 ECG – 18

STEMI vs. STE-Mimic Thompson 14 ECG – 19 ECG - 20

STEMI vs. STE-Mimic Thompson 15 ECG – 21 ECG – 22

STEMI vs. STE-Mimic Thompson 16 ECG – 23 ECG – 24

STEMI vs. STE-Mimic Thompson 17 ECG – 25 ECG – 26

ECG – 27 ECG – 28

STEMI vs. STE-Mimic Thompson 19 ECG – 29 ECG – 30

STEMI vs. STE-Mimic Thompson 20 ECG – 31 ECG – 32

STEMI vs. STE-Mimic Thompson 21 ECG – 33 ECG – 34

STEMI vs. STE-Mimic Thompson 22

The Solutions

STEMI vs. STE-Mimic Thompson 23 ECG – 1 ECG – 2

STEMI vs. STE-Mimic Thompson 24 ECG – 1 & ECG – 2 These are both examples of Left Ventricular Hypertrophy with a typical Left Ventricular Strain Pattern. Because there is limited space on prehospital 12-lead print outs, the monitor actually cuts the depth and height of complexes short. This is to keep extra tall or deep complexes from interfering with other leads. The ST-Elevation present in the right precordial leads (V1, V2, V3) is entirely due to the LV-Strain pattern. With LV-Strain, you will typically see ST-Elevation in the right precordial leads, and ST-Depression in the left precordial leads (V4, V5, V6). "Strain" is a pattern of asymmetric ST segment depression and T wave inversion. LV strain is most commonly seen in one or more leads that look at the left ventricle (leads I, aVL, V4, V5, V6); less commonly it can be seen in inferior leads. Some clues to identifying LVH & LV-Strain: When the left ventricle enlarges (LVH), the left atrium often follows suit, and becomes larger as well. Left atrial enlargement can present as an altered p-wave morphology, known as P-Mitrale. A p-wave with the characteristic “double hump” is indicative of P-Mitrale. Left atrial enlargement can also be identified in V1. If the P-wave in lead V1 is biphasic, it may be due to left atrial enlargement. If it is deeper, than it is tall, LAE is likely.

T-Wave Discordance With LVH, paced rhythms, ventricular rhythms, and Bundle Branch Blocks, T-wave discordance is a normal finding. T-wave discordance is present when the terminal deflection of the QRS-complex is opposite of the direction of the following T-wave. If you look at the image to the left, you will see that with both complexes, the last wave of the complex, and the T-wave are deflected in opposite directions. When this is present, and the terminal deflection of the QRS is negative (S-wave), ST-elevation is normal. This can usually be seen on a normal 12-Lead in V1, V2, V3.

STEMI vs. STE-Mimic Thompson 25 ECG – 3 ECG – 4

STEMI vs. STE-Mimic Thompson 26 ECG – 5 ECG – 6

STEMI vs. STE-Mimic Thompson 27 ECG – 3, ECG – 4, ECG – 5, & ECG – 6 These are various examples of Left Bundle Branch Block (LBBB). LBBB is most commonly identified by a supraventricular rhythm (p-waves are present), that is wide (greater than 3 small boxes, 120ms), and has a terminal S-wave in V1. This means that if the 12-lead shows a sinus or atrial rhythm wider than 3 small boxes, with a negative last wave of the QRS-complex in V1, it is probably LBBB. Usually the terminal wave is the biggest wave in V1, so with LBBB, the QRS-complex typically presents as almost entirely negative (down). It is important to remember that the width of a QRS-complex in a monomorphic rhythm (doesn’t change) can be determined in any lead. Sometimes the QRS complex may appear of normal width in one lead, while looking wide in others. Always go with the width of the QRS-complex where it looks the widest. Because Bundle Branch Blocks have T-wave discordance. STEMI is not generally determined in the presence of a LBBB. This is because LBBB has deep S-waves in the right precordial leads, causing the presence of ST-elevation without any myocardial damage. Sgarbossa’s Criteria This is an advanced skill used to determine the presence of an MI with a LBBB. Since this is not widely understood by most medical professionals, it CAN’T be used to call a STEMI alert. The rule: If the ST-Elevation is greater than 25% of the preceding S-wave, or if concordant ST-elevation is present, an MI is almost 100% likely to be present. Non-Specific Intraventricular Conduction Delay (IVCD) A LBBB is a type of IVCD. To be a true LBBB, in addition to the V1 criteria, leads I and V6 should have monomorphic R-wave QRS-complexes. If a 12-lead presents with a LBBB pattern in V1, but has negative complexes in leads I & V6, it is actually considered a Non-Specific IVCD. This, however, is not of great importance in the emergency setting. STE-Mimic The important thing to remember is that a LBBB can look a lot like a STEMI. Do not inadvertently call STEMI alert on a patient with a LBBB, unless the LBBB spontaneously occurred right before your eyes.

STEMI vs. STE-Mimic Thompson 28 ECG – 7 ECG – 8

STEMI vs. STE-Mimic Thompson 29 ECG – 9 ECG – 10

STEMI vs. STE-Mimic Thompson 30 ECG – 7, ECG – 8, ECG – 9, & ECG – 10 These are all examples of Benign Early Repolarization (BER), “Early Repol”. BER is one of the most common reasons for misdiagnosed STEMI. BER is caused by an elevation of the J-Point due to premature repolarization (recharging) of the ventricles. “Early Repol” Clues

- No reciprocal changes – because an MI often causes st-depression in leads opposite to those with elevation - Asymmetrical T-waves – because an early infarction has hyperactute T-waves (tall, broad, & symmetrical) - Concave ST-elevation – because the presence of convex ST-elevation is almost always an MI - Notched J-points – not always present with early repol, but a GREAT indicator that it is NOT an MI - Normal R-wave progression – because a MI often causes poor R-wave progression (clockwise rotation)

Remember, these clues don’t rule out a MI just because of their presence. For instance, if you have notched j-points, but reciprocal changes are present, it is most likely a STEMI. These clues should be used together with patient presentation. If all clues are present, it is almost certainly NOT a STEMI. The chart above outlines reciprocal areas of the 12-lead. The image to the right illustrates the difference between concave & convex ST-elevation.

Draw a line from the J-Point to the top of the T-wave, if the ST-segment falls below that line it is concave. If it is above the line, it is convex. Convex is worse!

STEMI vs. STE-Mimic Thompson 31 ECG – 11 ECG – 12

STEMI vs. STE-Mimic Thompson 32 ECG – 13 ECG – 11, ECG – 12, & ECG – 13 These are all examples of Acute Pericarditis. Note the widespread ST-Elevation amongst the many leads. PR-depression is also a common finding with pericarditis. The patient’s symptoms may be the biggest clue; positional pain relief is common. ST-Elevation that occurs simultaneously in leads I and II should always be very suspicious. The most common cause of this is acute pericarditis. Another cause would be an Apical MI (infarct of the apex). An apical Mi is just a fancy way to say that the entire bottom of the heart is infracted. This is very rare, yet very severe. All three of these examples were identified by the ECG monitor’s 12-lead interpretive algorhythm. All three of these patients were treated as STEMI alerts, incorrectly. Sometimes the printout diagnosis is right! In fact, with a clean tracing, the 12-lead software is very accurate at determining a STEMI, bundle branch block, LVH, and even early repolarization.

STEMI vs. STE-Mimic Thompson 33 ECG – 14 ECG – 15

STEMI vs. STE-Mimic Thompson 34 ECG – 14 & ECG – 15 These are both examples of Hyperkalemia. Hyperkalemia is an elevated serum potassium level, and may lead to lethal cardiac arrhythmias. The patients most susceptible to hyperkalemia are renal failure patients that require dialysis. ECG – 14: This 12-lead presents as a LBBB vs. Sine-wave. The patient’s history, and presentation should be used come to a solid determination. A Sine-wave is a sign of significant hyperkalemia, and may only last for minutes before degrading into a lethal arrythmia. A Sine-wave is present when there is a straight line from the tip of the S-wave (nadir) to the peak of the T-wave. ECG – 15: This 12-lead has a great example of peaked T-waves, indicating hyperkalemia. Note the tall, narrow T-waves in nearly every lead. The T-waves are actually larger than most of the QRS-complexes. This is a sign of increased potassium.

STEMI vs. STE-Mimic Thompson 35 ECG – 16 ECG – 16 This is most likely an early Inferior Wall MI with lateral, and posterior wall extension. If you recall how the coronary anatomy works, the right coronary artery (RCA) is usually the producer of the posterior descending artery (85% of the time). The right coronary artery may supply the inferior, posterior, and part of the lateral wall of the heart. ST- Elevation: minimal, but present in leads II & III, V5 & V6 (remember to compare against the following TP-Segment) ST- Depression: leads V1 & V2 have some ST-Depression, probably reciprocal to a posterior wall injury T-Wave Inversion: lead aVL has a very indicative look of an inferior wall injury (aVL is the most reciprocal lead to lead III) Hyperacute T-Waves: the tall, symmetrical, broad-based t-waves in leads II & aVF are the easiest to identify With the combination of these findings, this patient should certainly be transported emergently to a PCI facility. Remember, 1mm of STE in two contiguous leads is all that is needed to call STEMI; we almost have that with leads II & III. This patient should be monitored diligently for any changes.

STEMI vs. STE-Mimic Thompson 36 ECG – 17 ECG – 17 This is an example of an Antero-Septal MI, with some lateral wall extension. This is likely due to a proximal occlusion of the Left Anterior Descending coronary artery (LAD). The LAD, termed “Widow Maker”, supplies predominately the left ventricle. ST-Elevation: extensive, note the convex STE in V1 to V4. ST-Depression: There appears to be reciprocal changes in III & aVF, probably opposite to lateral wall injury. Notice how the amount of ST-Elevation present is not dependant on the size of the QRS-complex. This is damning evidence, in favor of an MI. With a benign cause of ST-elevation (STE), you have more STE with bigger QRS-complexes. If you look at this 12-lead though, V3 has smaller QRS-complex than V1, but has much more STE. Also worth mentioning is V4. Note the size of the QRS-complexes in V4. When you have a very small QRS-complex, the degree of STE will be less. So a QRS-complex as small as the one in V4 with STE of 1mm is just as significant as the presence of “tombstones”.

STEMI vs. STE-Mimic Thompson 37 ECG – 18 ECG – 18 This is an example of an extensive Inferior Wall MI (IWMI), with posterior & lateral wall extension. Just like ECG-16, this is probably due to a proximal RCA occlusion. Something worth noting on this ECG is that lead III has more STE than lead II. This is an indication of possible right ventricular (RV) infarction. A RV MI can effectively turn the right side of the heart into a conduit system, making cardiac output very dependent on preload. These patients often present with hypotension, and are very sensitive to preload reducers like nitroglycerine. Fluid administration goes a long way to increase cardiac output for these patients. V4R is the most sensitive lead for identifying a RV infarct. Move V3 & V4 to a mirrored placement on the right side of the patient’s chest to obtain V3R & V4R. Posterior Wall MI (PMI) With ST-depression in V1, V2, or V3 with or without T-wave inversion, a PWMI should be suspected; especially when an IWMI is present. Posterior leads (V7, V8, V9) may be used to conclude the presence of a PWMI.

STEMI vs. STE-Mimic Thompson 38 ECG – 19 ECG – 19 This is another example of an Antero-Septal MI. Often, multiple sides of the heart are affected simultaneously. The anterior wall, and septum are commonly infarcted together. The image to the right outlines the contiguous leads. Remember, STE must be present in 2 or more contiguous leads for a STEMI Alert.

STEMI vs. STE-Mimic Thompson 39 ECG - 20 ECG – 20 This is a rare example of an isolated Lateral Wall Infarct. This injury pattern is nearly always due to an occlusion to the Left Circumflex (LCx). Since the LCx is a sharp-turned branch of the Left Main coronary artery, it is the least likely to develop a susceptible lesion. This 12-lead is difficult to interpret though, due to its PR-depression & concave STE. STEMI vs. STE-Mimic: There are some clues on this ECG to help us determine that it is an AMI.

- The STE is in the left precordial leads. Usually with “early repol”, the benign STE is present mostly in V2 to V4. - No Global STE. All of the STE present is in contiguous leads, even minimally in aVR. - Reciprocal change. Lead III shows minimal, but present ST-depression. - The STE is concordant. This means that the STE is in the same direction as the terminal wave of the preceding R-wave. - Hyperacute T-waves. The T-waves in the leads with STE are tall, symmetrical, and broad-based.

STEMI vs. STE-Mimic Thompson 40 ECG – 21 ECG – 21 This is an example of an Inferior Wall MI, with probable posterior wall extension. Its important to note that since aVR is the most reciprocal lead to Lead III, it almost always has some form of reciprocal change present with an IWMI. The most common change is downwardly sloping ST-depression. Once again, like ECG – 16 & ECG – 18, we see possible posterior wall changes in the presence of an IWMI. To obtain V7, V8, & V9, move leads V4, V5, & V6 just below the patient’s left scapula. See the image to the right.

STEMI vs. STE-Mimic Thompson 41 ECG – 22 ECG – 22 This is an example of Wellen’s Phenomenon. Sometimes called Wellen’s warning, syndrome, or sign, this phenomenon is an indication of an impending anterior infarction. This phenomenon does NOT always occur. There is no rhyme or reason as to which patients will present with Wellen’s prior to his or her anterior MI, but its presence is an ominous finding. Wellen’s Syndrome can present as it does above, with symmetrical inverted T-waves in the septal and/or anterior leads (V2/V3 most common). It may also present as biphasic (positive & negative) T-waves, also most commonly seen in V2 & V3. In the absence of ST-elevation, these patients are not STEMI alerts, but should be transported to a STEMI facility, and monitored for the impending MI. Some literature states that an infarction has already begun when Wellen’s is present. It would be appropriate to treat these patients as if they are having a STEMI, notify the receiving facility of your concern, and call STEMI Alert if STE becomes present. Nitrates may impede STE from occurring.

STEMI vs. STE-Mimic Thompson 42 ECG – 23 ECG – 23 This is another Antero-Septal Infarct with lateral wall extension (seen best in aVL). A 12-lead with this many ST-elevated leads may create concern about possible acute pericarditis. The reciprocal changes found in the inferior leads should erase any doubt, confirming that this is, in fact a STEMI. Remember that leads aVL & III are the most reciprocal to each other. If you see ST-segment changes in one of these leads, immediately look for inverse changes in the other. As you can see on this ECG, there is STE in aVL, and ST-depression in lead III. This is true because of lead III & aVL’s placements. Look at the hexaxial reference system to the right. You can see that lead III’s positive pole is at 120 degrees, and aVL is at -30 degrees.

STEMI vs. STE-Mimic Thompson 43 ECG – 24 ECG – 25

STEMI vs. STE-Mimic Thompson 44 ECG – 24 & ECG – 25 These are both examples of Inferior Wall Infarction, with probable posterior wall extension. Note that both ECGs have reciprocal changes present in aVL. Hyperacute T-Waves The inferior leads in ECG – 24, and the low lateral leads (V5 & V6) in ECG – 25 both have examples of hyperacute T-waves. These T-waves are usually present for the first 30 minutes of an MI, and they are symmetrical, broad-based (wider than hyperkalemic T-waves), and tall.

A symmetrical T-wave is always a result of some sort of pathology. They don’t necessarily have to be a result of an AMI, but may indicate hyperkalemia (tall & narrow), or some other disease process. Conditions like LVH with left ventricular strain should always have asymmetrical T-waves. Keep in mind; a person may still be having an MI with asymmetrical T-waves.

STEMI vs. STE-Mimic Thompson 45 ECG – 26 ECG – 26 This ECG is an example of Right Bundle Branch Block (RBBB). RBBB is present when a wide supraventricular rhythm presents with a positive terminal deflection in V1. Other findings include appropriate T-wave discordance, and a slurred S-wave in Lead I and V6. The absence of the slurred S-wave in Leads I and V6 would indicate a non- specific intraventricular conduction delay (IVCD). This is of little importance in the prehospital arena though. For matters of simplicity, a wide supraventricular rhythm with a terminal R-wave in V1 is a RBBB. This ECG does not have any STE. Often, STE is misdiagnosed on 12-leads with RBBB because the J-point is inaccurately identified. Remember that the QRS-complexes above and below any lead in question will have J-points in the exact same spot. If you are unsure of the presence of ST-elevation, compare your J-points to the other leads in the same vertical plane by drawing a straight line.

STEMI vs. STE-Mimic Thompson 46 ECG – 27 ECG – 27 This is an early Antero-Septal Infarct. This ECG does not meet STEMI Alert criteria yet, since V1 is the only lead with STE. The concavity of the STE in V1 is a significant sign of myocardial injury. Other factors that help in determining that this ECG indicates an early AMI are the hyperacute T-waves in V2 to V4, and the reciprocal ST-depression in the inferior leads. Remember, when trying to determine if STE is present, compare the J-point to the following TP-segment.

STEMI vs. STE-Mimic Thompson 47 ECG – 28 ECG – 28 This is an example of Atrial Bigeminy with an Anterior Infarct. The extra-systole is probably occurring because of the severe 1st degree AV block found in the underlined rhythm. If you look at the ECG from afar, it appears to have a pattern. This coupling of complexes is caused by the premature beat, persistently occurring in the same position. This is the heart’s own electrical backup system taking effect. ST-elevation can be seen with both morphologies, in V3 through V5, indicating some lateral extension. The convex STE in V4 & V5 leaves no question, this IS an AMI. STEMI Alert should be called for this patient. Side note: Premature complexes, whether ventricular or not, should not be treated if the underlined rhythm is very slow. The cardiac conduction system has a magnificent way of compensating for itself, and if this compensation is blocked by medications, the patient’s condition may decline rapidly. Not everything abnormal is bad!

STEMI vs. STE-Mimic Thompson 48 ECG – 29 ECG - 29 ECG – 29 This ECG is that of a Right Bundle Branch Block with Antero-Septal Infarction, and lateral extension. T-wave discordance is normal with a RBBB, however, it is not excessive enough to cause benign STE. STEMI Alert may still be called in the presence of a RBBB. This ECG has enough evidence to call STEMI Alert. Massive STE in V2 through V6, with reciprocal changes in the inferior leads (II, III, aVF). Whenever you see a QRS-complex in V1 & V2 that is more positive than it is negative, RBBB should be considered. Right Ventricular Hypertrophy (RVH) may cause an R:S ratio in V1/V2 greater that 1 as well. RVH presents with narrow QRS-complexes, and RBBB presents with wide QRS-complexes. Even though these QRS-complexes don’t appear excessively wide, they are greater than 120 ms, concluding the presence of RBBB. Tall R-waves in V1/V2 may also be present with a posterior wall infarct; this is the equivalent of the Q-waves found with an older infarction.

STEMI vs. STE-Mimic Thompson 49 ECG – 30 ECG – 30 This is an example of Global Ischemia. The ST-depression, found in most of the leads, indicates ischemia. This is a much more interesting ECG than that, however. This particular 12-lead tracing indicates a significant lesion in the Left Main Coronary Artery (LMCA); that’s the big one. This is one of the very few times that aVR can be used for more than just assuring correct limb lead placement. The rule states that if you have STE in aVR greater than the STE in V1, a LMCA lesion is very likely. The likeliness only improves in the presence of global ST-depression. This is NOT an indication of occlusion; an occluded LMCA is present mostly on dead people only. This is not a STEMI Alert, but this patient should be transported to a PCI facility because of their risk of morbidity & mortality. * ST-Elevation in aVR may also be indicative of “Three Vessel Disease”, occlusions of the RCA, LAD, & LCx. ** Isolated ST-Elevation in V1 may also be indicative of a Right Ventricular Infarct. Consider performing a right-sided 12-lead when STE is present in V1, hypotension exists, and/or inferior changes exist.

STEMI vs. STE-Mimic Thompson 50 ECG – 31 ECG – 31 This is an Anterior Wall Infarct. This is not an obvious STEMI, but the tracings taken after this one were. Although V3 looks to have ST-elevation on this printout, it does not. If you compare the J-point in V3 to the TP-segment that follows, you will find that there is no STE; this is why we don’t compare the J-point to the PR-segment. The presence of hyperacute T-waves help to conclude the presence of myocardial injury. The T-wave inversion in V1 & V2 is likely due to the zone of ischemia surrounding the area of injury. This ECG is an example of poor data quality. The limb leads have obscuring artifact, and the entire tracing has a wandering baseline—making interpretation more difficult. It is possible that a cleaner tracing may have had more clear cut STEMI criteria present. Fortunately, the 12-leads that followed had obvious STEMI criteria, and the patient was transported to a PCI facility. Worth Noting: Those tall, peaked P-waves, seen most obviously in the limb leads, are a sign of Right Atrial Enlargement. This finding is called P-pulmonale. Right atrial enlargement is often a result of RVH; usually caused by pulmonary hypertension, resulting from a chronic respiratory pathology (COPD, Asthma, etc.). P-pulmonale & P-mitrale combined is known as biatrial enlargement.

STEMI vs. STE-Mimic Thompson 51 ECG – 32 ECG – 32 This is an example of Reversed Limb Leads. While at first glance the inverted T-waves on this ECG look concerning, the problem with this tracing are misplaced electrodes. Lead I should almost always be predominately positive, although a left posterior fascicular block may cause Right Axis Deviation. aVR should always be mostly negative outside of paced or ventricular arrhythmias. The combination of a narrow QRS-complex, negatively deflected Lead I, and positively deflected aVR will almost always be due to misplaced limb leads. Dextrocardia Situs Inversus (reversed heart) is a very uncommon congenital pathology that could also cause these findings.

STEMI vs. STE-Mimic Thompson 52 ECG – 33 ECG – 33 This ECG shows a Sinus Tachycardia With Trigeminy. This is a more difficult 12-lead to interpret, but if you take a close look, you will see that there is a regularly occurring aberrant complex, every third beat. If you look at the underlined complex, there appears to be some form of an intraventricular conduction delay, similar to a LBBB. There is also ST-elevation present in V1 & V2. ST-depression appears in V5 & V6. The ST-segments are very diffuse in the inferior, and anterior leads. Due to the LBBB pattern in V1, we cannot call this a STEMI Alert.

STEMI vs. STE-Mimic Thompson 53 ECG – 34 ECG – 34 This is an excellent example of Left Bundle Branch Block. Notice the presence of P-waves, the wide QRS-complex, and the terminal S-wave in V1. This ECG also displays how LBBB can alter ST-segments & T-waves without the presence of myocardial damage.