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Analyzing Prominent T Waves and ST-segment Abnormalities in Acute Myocardial Infarction
The Journal of Emergency Medicine, Vol. 43, No. 2, pp. e81– e85, 2012 Copyright © 2012 Elsevier Inc. Printed in the USA. All rights reserved 0736-4679/$–see front matter
http://dx.doi.org/10.1016/j.jemermed.2009.08.032
Clinical Communications: Adults ANALYZING PROMINENT T WAVES AND ST-SEGMENT ABNORMALITIES IN ACUTE MYOCARDIAL INFARCTION Michele A. Genzlinger,
DO
and Mary Eberhardt,
MD
Department of Emergency Medicine, St. Luke’s Hospital, Bethlehem, Pennsylvania Reprint Address: Michele A. Genzlinger, DO, Department of Emergency Medicine, St. Luke’s Hospital, 801 Ostrum Street, Bethlehem, PA 18015
e Abstract—Background: Hyperacute T waves and the non-concave appearance of the ST segment are early changes that may be seen on the electrocardiogram (ECG) in an acute myocardial infarction (AMI) patient. There are specific morphological changes in these ECG findings that can help distinguish them from other conditions with similar ECG patterns. The differential diagnosis of prominent T waves and ST-segment elevation is well known, however, certain tools to distinguish ECG patterns with various etiologies have been developed and proven useful to the emergency physician. Objectives: 1) To discuss and review the more common differential diagnosis of prominent T waves and how to identify the hyperacute T wave of AMI. 2) To review the distinction and determination of a concave and non-concave ST segment that may be initially overlooked. Case Report: A 42-year-old woman with minimal cardiac risk factors developed an STsegment elevation myocardial infarction (STEMI) that illustrates the evolution of early and classic ECG changes associated with her infarct. Conclusions: The classic STEMI is ingrained in the emergency physician’s mind, however, sometimes other lesser known and obvious ECG patterns can present early on in the evolution of disease, and these morphological patterns should be identified and treated accordingly. © 2012 Elsevier Inc.
phological variants are important skills for the emergency physician. Often times these subtleties may be the only clue to a patients’ underlying disease process. The goal of this case report is to highlight the importance and improve the clinician’s awareness of these patterns as they relate to acute myocardial infarction (AMI). CASE REPORT A 42-year-old woman presented to the Emergency Department 1 h after the onset of a single episode of transient mid-sternal chest discomfort that woke her from sleep. At triage she was asymptomatic without any active complaints. She described the pain to the triage nurse as a burning discomfort in the middle of her chest with radiation to both of her arms. She denied any other concomitant symptoms other than feeling weak at the time. The pain resolved on its own about 15 min later without any specific intervention. She was a married, healthy mother of two children without any significant past medical or surgical history. She had a 20-pack-year smoking history, denied any alcohol or illicit drug use, and had no significant family history of coronary artery disease. As per department protocol, an initial ECG was obtained and reviewed by the attending physician before patient evaluation (Figure 1). This initial ECG was felt to be concerning for hyperacute T waves representing early cardiac ischemia, but did not meet criteria for cardiac catheterization. The nurse was instructed to initiate a cardiac work-up and administer aspirin. Approximately 3 min after
e Keywords—prominent T waves; ST-segment morphology; AMI (acute myocardial infarction); ECG (electrocardiogram)
INTRODUCTION The evaluation of early electrocardiogram (ECG) changes and recognition of specific T-wave and ST-segment mor-
RECEIVED: 7 May 2009; FINAL ACCEPTED: 30 August 2009
SUBMISSION RECEIVED:
13 July 2009; e81
e82
M. A. Genzlinger and M. Eberhardt
Figure 1. Electrocardiogram (ECG) 05:15. The patient’s initial ECG—would you be ready to activate the catheterization laboratory? This ECG demonstrates prominent T waves, specifically those found in early acute myocardial infarction.
the nurse brought the ECG to the attending for evaluation, the women went into cardiac arrest. Initially, she was in a ventricular fibrillation that subsequently converted into a sinus tachycardia after both electrical and pharmacological cardioversion. A subsequent ECG after conversion revealed ST-segment changes suggestive of AMI (Figure 2). The patient was then sent to the cardiac catheterization laboratory, where she was found to have an eccentric thrombogenic 70% stenosis in the left anterior descending coronary artery (LAD). The cardiologist reported a single fibrous plaque in the proximal LAD, which was then aspirated successfully and followed by placement of a non-drug-eluting stent. The patient was transferred in stable condition to the cardiac floor and discharged
home 4 days later after an uncomplicated hospital admission. DISCUSSION Hyperacute T Waves in the Evolution of STEMI AMI has well-known and characteristic ECG changes associated with its onset, evolution, and resolution. Sometimes, early changes may be difficult for the practitioner to identify. These ECGs illustrate some of the more well-known and ominous findings, as well as those that are more subtle and less recognized. In this review we discuss the recognition of prominent T waves, spe-
Figure 2. Electrocardiogram (ECG) 05:36. This ECG is post-cardiac arrest and 12 min before ECG 05:48 showing classic ST-segment elevation myocardial infarction. Please take note of the hyperacute T-waves.
Prominent T Waves and ST-Segment Abnormalities in AMI
e83
Table 1. Common Differential Diagnosis of Prominent T Waves STEAMI
Hyperkalemia
More asymmetric than symmetric with a broad base Associated reciprocal ST-segment depression
More symmetric in nature
Increased R-wave amplitude
As potassium levels increase, may be followed by increased amplitude of the T wave (generally occurs with potassium that exceeds 6.8 mL/dL) Patients at risk for electrolyte abnormalities (i.e., renal failure, may also see QT-interval prolongation and LVH)
J-point elevation
Tall, narrow, and peaked with a prominent apex
Short-lived and often followed by STE in AMI patient Patient with cardiac history or risk factors
BER
LVH
More asymmetric, tall and peaked STE appears elevated from the J point while maintaining a concave appearance Generally seen diffusely in all leads
Initial up-sloping pattern is concave in nature Strain pattern
Concordant with the QRS complex
Repolarization pattern of QS complex with STE and prominent T waves in precordial leads
LVH voltage criteria
Typically younger patients
STEAMI ⫽ ST-segment elevation acute myocardial infarction; BER ⫽ benign early repolarization; LVH ⫽ left ventricular hypertrophy.
cifically those found in AMI, known as hyperacute T waves, as well as the morphological analysis of the ST segment in AMI patients. The most obvious findings on the initial ECG may be the prominent T waves across the pre-cordial leads, as well as the ST-segment depression in the inferior leads (Figure 1). It is well known that one of the earliest findings in ST-elevation AMI is prominent T waves. These so called hyperacute T waves are noted as early as 30 min after the onset of coronary occlusion (1). These changes represent lack of adequate blood flow to the myocardium and are potentially reversible. If oxygen demand of the heart is lessened, T waves may revert to normal. If overlooked or not urgently addressed, it may progress to ST changes consistent with STEMI. Immediate intervention including oxygen, aspirin, heparin, and beta blockade, may aid in decreasing cardiac demand and improving oxygen-rich blood flow to the cardiac muscle. The utilization of serial ECGs to follow T-wave and ST progression is useful in determining whether the interventions are successful in reversing ischemia. The progression to STEMI from hyperacute T waves would dictate the need for thrombolysis or percutaneous coronary intervention (PCI). There are numerous conditions that can cause T-wave changes; the difficulty lies in distinguishing between them. The conditions that most closely resemble the hyperacute T waves of AMI are benign early repolarization (BER), hyperkalemia, and left ventricular hypertrophy (LVH). Of course, the clinical context in which one is interpreting the ECG is of utmost value, but there are also unique features that help differentiate between these very different conditions and their associated ECG changes (Table 1.) The hyperacute
T waves of AMI tend to be asymmetric in nature with a broader base. They are often associated with reciprocal ST-segment depression in opposing leads, may have increased R-wave amplitude, J-point elevation, and usually are very short-lived (1). The importance of T-wave findings cannot be overemphasized. T-wave changes may be the only manifestation of ischemia on the initial ECG and may help make the difference in diagnosis. Studies have shown that 1–21% of patients with AMI present with an initially normal ECG or non-specific ST segment/T-wave abnormalities, which include hyperacute T waves (2). T waves of hyperkalemia are more symmetric in nature, tall, and narrow, with a more prominent apex. They are generally associated with potassium levels ⬎ 6.8 mL/dL. In BER, the T waves tend to be more asymmetric, tall, and peaked, and the STE appears elevated from the J point while maintaining a concave appearance. LVH tends to have a concave appearance, with an associated strain pattern and LVH by voltage criteria. Subtle ST Segment Elevation of AMI Figure 2 is the second 12-lead ECG obtained after the patient converted from ventricular fibrillation to sinus rhythm. At first glance, the ST segments across the precordium do not appear different from Figure 1, but there is an important distinction. There are various benign disease states and normal presentations of the ECG that may result in ST elevation. Often, it is the morphology, concave or non-concave, of the ST segment that is important in distinguishing ischemia from normal vari-
e84
M. A. Genzlinger and M. Eberhardt
Figure 3. Electrocardiogram (ECG) 05:15 compared to ECG 05:36. These two ECGs demonstrated comparison between concave vs. non-concave ST segment morphology as manifested in acute myocardial infarction.
ants. Figure 3 highlights an objective way to analyze whether the ST segment elevation from the J point is concave in nature. This method was found to be 97% specific for identifying STE morphology in AMI (2). To determine this, mark two points on the ST segment: the J point (where the QRS ends and the ST segment begins) and the apex of the ST-segment/T-wave complex. Next, a line is drawn to connect the two points. If the ST segment is above the line or falls directly on the line, this is deemed non-concave and in the right clinical setting is consistent with AMI. If the ST segment is found below the line, then the morphology is concave and likely associated with BER. This method, despite having a sensitivity of 77% for AMI, has a positive predictive value of 94% (2).
Although not readily apparent from first glance, the morphology on the initial ECG, timed 5:15, and the postarrest ECG timed 5:36, is different. By applying the rule described by Brady, this becomes more apparent (2). The drawn red line in the initial ECG highlights a concave pattern of the ST segment. In the subsequent ECG, the ST segment falls directly on the drawn line, indicating a non-concave pattern more indicative of subtle ST changes of AMI. This finding was captured approximately 12 min before the ECG in Figure 4, which demonstrated a more classic pattern of STEMI. ST elevation signifies myocardial injury; this indicates a degree of cellular damage beyond that of mere ischemia. In most circumstances, ST elevation is a reliable sign that the AMI has occurred. It too may be potentially reversible
Figure 4. Electrocardiogram (ECG) 05:48. This ECG demonstrates the classic ST-segment elevation morphology of an acute anterior wall ST-segment elevation myocardial infarction.
Prominent T Waves and ST-Segment Abnormalities in AMI
e85
with proper interventions. These include oxygen, heparin, aspirin, beta-blockade, serial ECGs, and because ST segment is more indicative of cellular damage, thrombolytics and emergent PCI are indicated.
ECGs are crucial in identifying all possible AMI patients, and knowledge of subtle ST-segment and T-wave findings may make the difference in the early diagnosis of these patients.
CONCLUSION REFERENCES As emergency medicine practitioners, it is our responsibility to identify individuals at higher risk of developing AMI. Many methodologies of risk stratification exist, but there are patients who may have ischemia that these methods fail to identify. Often, the only indication of ischemia may be subtle findings on the ECG. Serial
1. Somers M, Brady W, Perron A, Mattu A. The prominent T wave: electrocardiographic differential diagnosis. Am J Emerg Med 2002; 20:243–51. 2. Brady WJ. Electrocardiographic ST-segment elevation: the diagnosis of acute myocardial infarction by morphological analyisis of the ST segment. Acad Emerg Med 2001;8:961–7.
http://dx.doi.org/10.1016/j.jemermed.2009.08.032
Clinical Communications: Adults ANALYZING PROMINENT T WAVES AND ST-SEGMENT ABNORMALITIES IN ACUTE MYOCARDIAL INFARCTION Michele A. Genzlinger,
DO
and Mary Eberhardt,
MD
Department of Emergency Medicine, St. Luke’s Hospital, Bethlehem, Pennsylvania Reprint Address: Michele A. Genzlinger, DO, Department of Emergency Medicine, St. Luke’s Hospital, 801 Ostrum Street, Bethlehem, PA 18015
e Abstract—Background: Hyperacute T waves and the non-concave appearance of the ST segment are early changes that may be seen on the electrocardiogram (ECG) in an acute myocardial infarction (AMI) patient. There are specific morphological changes in these ECG findings that can help distinguish them from other conditions with similar ECG patterns. The differential diagnosis of prominent T waves and ST-segment elevation is well known, however, certain tools to distinguish ECG patterns with various etiologies have been developed and proven useful to the emergency physician. Objectives: 1) To discuss and review the more common differential diagnosis of prominent T waves and how to identify the hyperacute T wave of AMI. 2) To review the distinction and determination of a concave and non-concave ST segment that may be initially overlooked. Case Report: A 42-year-old woman with minimal cardiac risk factors developed an STsegment elevation myocardial infarction (STEMI) that illustrates the evolution of early and classic ECG changes associated with her infarct. Conclusions: The classic STEMI is ingrained in the emergency physician’s mind, however, sometimes other lesser known and obvious ECG patterns can present early on in the evolution of disease, and these morphological patterns should be identified and treated accordingly. © 2012 Elsevier Inc.
phological variants are important skills for the emergency physician. Often times these subtleties may be the only clue to a patients’ underlying disease process. The goal of this case report is to highlight the importance and improve the clinician’s awareness of these patterns as they relate to acute myocardial infarction (AMI). CASE REPORT A 42-year-old woman presented to the Emergency Department 1 h after the onset of a single episode of transient mid-sternal chest discomfort that woke her from sleep. At triage she was asymptomatic without any active complaints. She described the pain to the triage nurse as a burning discomfort in the middle of her chest with radiation to both of her arms. She denied any other concomitant symptoms other than feeling weak at the time. The pain resolved on its own about 15 min later without any specific intervention. She was a married, healthy mother of two children without any significant past medical or surgical history. She had a 20-pack-year smoking history, denied any alcohol or illicit drug use, and had no significant family history of coronary artery disease. As per department protocol, an initial ECG was obtained and reviewed by the attending physician before patient evaluation (Figure 1). This initial ECG was felt to be concerning for hyperacute T waves representing early cardiac ischemia, but did not meet criteria for cardiac catheterization. The nurse was instructed to initiate a cardiac work-up and administer aspirin. Approximately 3 min after
e Keywords—prominent T waves; ST-segment morphology; AMI (acute myocardial infarction); ECG (electrocardiogram)
INTRODUCTION The evaluation of early electrocardiogram (ECG) changes and recognition of specific T-wave and ST-segment mor-
RECEIVED: 7 May 2009; FINAL ACCEPTED: 30 August 2009
SUBMISSION RECEIVED:
13 July 2009; e81
e82
M. A. Genzlinger and M. Eberhardt
Figure 1. Electrocardiogram (ECG) 05:15. The patient’s initial ECG—would you be ready to activate the catheterization laboratory? This ECG demonstrates prominent T waves, specifically those found in early acute myocardial infarction.
the nurse brought the ECG to the attending for evaluation, the women went into cardiac arrest. Initially, she was in a ventricular fibrillation that subsequently converted into a sinus tachycardia after both electrical and pharmacological cardioversion. A subsequent ECG after conversion revealed ST-segment changes suggestive of AMI (Figure 2). The patient was then sent to the cardiac catheterization laboratory, where she was found to have an eccentric thrombogenic 70% stenosis in the left anterior descending coronary artery (LAD). The cardiologist reported a single fibrous plaque in the proximal LAD, which was then aspirated successfully and followed by placement of a non-drug-eluting stent. The patient was transferred in stable condition to the cardiac floor and discharged
home 4 days later after an uncomplicated hospital admission. DISCUSSION Hyperacute T Waves in the Evolution of STEMI AMI has well-known and characteristic ECG changes associated with its onset, evolution, and resolution. Sometimes, early changes may be difficult for the practitioner to identify. These ECGs illustrate some of the more well-known and ominous findings, as well as those that are more subtle and less recognized. In this review we discuss the recognition of prominent T waves, spe-
Figure 2. Electrocardiogram (ECG) 05:36. This ECG is post-cardiac arrest and 12 min before ECG 05:48 showing classic ST-segment elevation myocardial infarction. Please take note of the hyperacute T-waves.
Prominent T Waves and ST-Segment Abnormalities in AMI
e83
Table 1. Common Differential Diagnosis of Prominent T Waves STEAMI
Hyperkalemia
More asymmetric than symmetric with a broad base Associated reciprocal ST-segment depression
More symmetric in nature
Increased R-wave amplitude
As potassium levels increase, may be followed by increased amplitude of the T wave (generally occurs with potassium that exceeds 6.8 mL/dL) Patients at risk for electrolyte abnormalities (i.e., renal failure, may also see QT-interval prolongation and LVH)
J-point elevation
Tall, narrow, and peaked with a prominent apex
Short-lived and often followed by STE in AMI patient Patient with cardiac history or risk factors
BER
LVH
More asymmetric, tall and peaked STE appears elevated from the J point while maintaining a concave appearance Generally seen diffusely in all leads
Initial up-sloping pattern is concave in nature Strain pattern
Concordant with the QRS complex
Repolarization pattern of QS complex with STE and prominent T waves in precordial leads
LVH voltage criteria
Typically younger patients
STEAMI ⫽ ST-segment elevation acute myocardial infarction; BER ⫽ benign early repolarization; LVH ⫽ left ventricular hypertrophy.
cifically those found in AMI, known as hyperacute T waves, as well as the morphological analysis of the ST segment in AMI patients. The most obvious findings on the initial ECG may be the prominent T waves across the pre-cordial leads, as well as the ST-segment depression in the inferior leads (Figure 1). It is well known that one of the earliest findings in ST-elevation AMI is prominent T waves. These so called hyperacute T waves are noted as early as 30 min after the onset of coronary occlusion (1). These changes represent lack of adequate blood flow to the myocardium and are potentially reversible. If oxygen demand of the heart is lessened, T waves may revert to normal. If overlooked or not urgently addressed, it may progress to ST changes consistent with STEMI. Immediate intervention including oxygen, aspirin, heparin, and beta blockade, may aid in decreasing cardiac demand and improving oxygen-rich blood flow to the cardiac muscle. The utilization of serial ECGs to follow T-wave and ST progression is useful in determining whether the interventions are successful in reversing ischemia. The progression to STEMI from hyperacute T waves would dictate the need for thrombolysis or percutaneous coronary intervention (PCI). There are numerous conditions that can cause T-wave changes; the difficulty lies in distinguishing between them. The conditions that most closely resemble the hyperacute T waves of AMI are benign early repolarization (BER), hyperkalemia, and left ventricular hypertrophy (LVH). Of course, the clinical context in which one is interpreting the ECG is of utmost value, but there are also unique features that help differentiate between these very different conditions and their associated ECG changes (Table 1.) The hyperacute
T waves of AMI tend to be asymmetric in nature with a broader base. They are often associated with reciprocal ST-segment depression in opposing leads, may have increased R-wave amplitude, J-point elevation, and usually are very short-lived (1). The importance of T-wave findings cannot be overemphasized. T-wave changes may be the only manifestation of ischemia on the initial ECG and may help make the difference in diagnosis. Studies have shown that 1–21% of patients with AMI present with an initially normal ECG or non-specific ST segment/T-wave abnormalities, which include hyperacute T waves (2). T waves of hyperkalemia are more symmetric in nature, tall, and narrow, with a more prominent apex. They are generally associated with potassium levels ⬎ 6.8 mL/dL. In BER, the T waves tend to be more asymmetric, tall, and peaked, and the STE appears elevated from the J point while maintaining a concave appearance. LVH tends to have a concave appearance, with an associated strain pattern and LVH by voltage criteria. Subtle ST Segment Elevation of AMI Figure 2 is the second 12-lead ECG obtained after the patient converted from ventricular fibrillation to sinus rhythm. At first glance, the ST segments across the precordium do not appear different from Figure 1, but there is an important distinction. There are various benign disease states and normal presentations of the ECG that may result in ST elevation. Often, it is the morphology, concave or non-concave, of the ST segment that is important in distinguishing ischemia from normal vari-
e84
M. A. Genzlinger and M. Eberhardt
Figure 3. Electrocardiogram (ECG) 05:15 compared to ECG 05:36. These two ECGs demonstrated comparison between concave vs. non-concave ST segment morphology as manifested in acute myocardial infarction.
ants. Figure 3 highlights an objective way to analyze whether the ST segment elevation from the J point is concave in nature. This method was found to be 97% specific for identifying STE morphology in AMI (2). To determine this, mark two points on the ST segment: the J point (where the QRS ends and the ST segment begins) and the apex of the ST-segment/T-wave complex. Next, a line is drawn to connect the two points. If the ST segment is above the line or falls directly on the line, this is deemed non-concave and in the right clinical setting is consistent with AMI. If the ST segment is found below the line, then the morphology is concave and likely associated with BER. This method, despite having a sensitivity of 77% for AMI, has a positive predictive value of 94% (2).
Although not readily apparent from first glance, the morphology on the initial ECG, timed 5:15, and the postarrest ECG timed 5:36, is different. By applying the rule described by Brady, this becomes more apparent (2). The drawn red line in the initial ECG highlights a concave pattern of the ST segment. In the subsequent ECG, the ST segment falls directly on the drawn line, indicating a non-concave pattern more indicative of subtle ST changes of AMI. This finding was captured approximately 12 min before the ECG in Figure 4, which demonstrated a more classic pattern of STEMI. ST elevation signifies myocardial injury; this indicates a degree of cellular damage beyond that of mere ischemia. In most circumstances, ST elevation is a reliable sign that the AMI has occurred. It too may be potentially reversible
Figure 4. Electrocardiogram (ECG) 05:48. This ECG demonstrates the classic ST-segment elevation morphology of an acute anterior wall ST-segment elevation myocardial infarction.
Prominent T Waves and ST-Segment Abnormalities in AMI
e85
with proper interventions. These include oxygen, heparin, aspirin, beta-blockade, serial ECGs, and because ST segment is more indicative of cellular damage, thrombolytics and emergent PCI are indicated.
ECGs are crucial in identifying all possible AMI patients, and knowledge of subtle ST-segment and T-wave findings may make the difference in the early diagnosis of these patients.
CONCLUSION REFERENCES As emergency medicine practitioners, it is our responsibility to identify individuals at higher risk of developing AMI. Many methodologies of risk stratification exist, but there are patients who may have ischemia that these methods fail to identify. Often, the only indication of ischemia may be subtle findings on the ECG. Serial
1. Somers M, Brady W, Perron A, Mattu A. The prominent T wave: electrocardiographic differential diagnosis. Am J Emerg Med 2002; 20:243–51. 2. Brady WJ. Electrocardiographic ST-segment elevation: the diagnosis of acute myocardial infarction by morphological analyisis of the ST segment. Acad Emerg Med 2001;8:961–7.