Benign early repolarization: electrocardiographic manifestations and differentiation from other ST segment elevation syndromes

A tale of two formulas: Differentiation of subtle anterior MI from benign ST segment elevation

BACKGROUND

It may sometimes be difficult to differentiate subtle ST-segment elevation (STE) due to anterior myocardial infarction (MI) from benign variant (BV) STE. Recently, two related formulas were proposed for this purpose. However, they have never been tested in an external population.

MATERIALS AND METHODS

Consecutive patients from May 2017 to January 2018, who were admitted with the diagnosis of acute anterior STEMI, were enrolled. Electrocardiograms were systematically reviewed and only subtle ones were included. First 200 consecutive patients with noncardiac chest pain were also enrolled as a control group. Relevant electrocardiographic parameters were measured.

RESULTS

A total of 379 anterior MI and 200 BV-STE cases were enrolled during study period. A total of 241 patients in STEMI group were excluded for not matching subtleness criteria, four patients in control group were also excluded because of prior left-anterior descending artery intervention. The three-variable formula, with recommended cut-point of 23.5, had a sensitivity, specificity, and diagnostic accuracy of 73.9%, 86.7%, and 81.4%, respectively. The four-variable formula, with the published cut-point of 18.2, had a sensitivity, specificity, and diagnostic accuracy of 83.3%, 87.7%, and 85.9%, respectively.

CONCLUSION

Three- and four-variable formulas with recommended cutoffs have a reasonable sensitivity, specificity, and diagnostic accuracy in differentiating subtle STEMI with BV-STE. Although both perform well, the four-variable formula has a higher sensitivity, specificity, and diagnostic accuracy and should be preferred.

Twelve-lead electrocardiography in the young: physiologic and pathologic abnormalities

BACKGROUND/ OBJECTIVE: The purpose of the present study was to analyze the prevalence of physiologic and pathologic ECG abnormalities in a cohort of young conscripts that represents the whole young generation of today.

METHODS

ECGs of all Swiss citizens who underwent conscription for the army during a 29-month period were analyzed manually.

RESULTS

ECGs of 43,401 conscripts (mean age 19.2 ± 1.1 years) were analyzed; 158 conscripts were female. Incomplete right bundle branch block was found in 5870 (13.5%) and left anterior fascicular block in 360 (0.83%). First-degree AV block was present in 329 (0.8%) and Mobitz type I (Wenckebach) second-degree AV block in 3 (0.01%). Early repolarization was observed in 1035 (2.4%), T-wave inversion in 39 (0.09%), and minor T-wave changes in 182 (0.42%). Brugada-like abnormalities were observed in 6 (0.01%). None of the conscripts had atrial fibrillation or flutter.

CONCLUSION

ECG abnormalities can be found in a relatively large proportion of young individuals. Incomplete right bundle branch block, left fascicular block, and first-degree AV block are the most frequent findings. No conscript presented with atrial fibrillation or flutter.

Recommendations for interpretation of 12-lead electrocardiogram in the athlete

Cardiovascular remodelling in the conditioned athlete is frequently associated with physiological ECG changes. Abnormalities, however, may be detected which represent expression of an underlying heart disease that puts the athlete at risk of arrhythmic cardiac arrest during sports. It is mandatory that ECG changes resulting from intensive physical training are distinguished from abnormalities which reflect a potential cardiac pathology. The present article represents the consensus statement of an international panel of cardiologists and sports medical physicians with expertise in the fields of electrocardiography, imaging, inherited cardiovascular disease, cardiovascular pathology, and management of young competitive athletes. The document provides cardiologists and sports medical physicians with a modern approach to correct interpretation of 12-lead ECG in the athlete and emerging understanding of incomplete penetrance of inherited cardiovascular disease. When the ECG of an athlete is examined, the main objective is to distinguish between physiological patterns that should cause no alarm and those that require action and/or additional testing to exclude (or confirm) the suspicion of an underlying cardiovascular condition carrying the risk of sudden death during sports. The aim of the present position paper is to provide a framework for this distinction. For every ECG abnormality, the document focuses on the ensuing clinical work-up required for differential diagnosis and clinical assessment. When appropriate the referral options for risk stratification and cardiovascular management of the athlete are briefly addressed.

Alarming ST-segment elevation in a young male with left anterior descending coronary artery myocardial bridging

Chest pain continues to be one of the leading emergency department presentations. Acute coronary syndrome is the most dreaded chest pain scenario, as "time is myocardium" in this situation. Numerous benign and less life-threatening diseases like early repolarization, acute pericarditis, and vasospastic angina can present with a similar clinical picture. ST-segment elevation on an electrocardiogram can occur in all these situations and in many others, creating diagnostic dilemma. A young male with chest pain and concurrent ST-segment elevation was reported. He was ultimately discovered to have myocardial bridging of a coronary arterial segment.

Cardiac issues in the young athlete

Young athletes are disproportionately plagued with congenital cardiac disease. Many of these diseases predispose to sudden cardiac death (SCD), a dramatic and tragic outcome for any young athlete. In many cases, conditions that predispose to SCD do not cause symptoms or show signs on examination, making diagnosis of cardiac disease and prevention of SCD difficult. Clinicians should be familiar with common causes of SCD and their symptoms, perform careful evaluations, refer athletes in whom there are concerns, and make sure any concerning findings receive thorough evaluation. Clinicians should also be familiar with and follow recent guidelines on return to play. Unfortunately, most preparticipation examinations are inadequate, due in part to use of inadequate forms. Better forms are available and should replace inadequate ones.

Electrocardiogram differentiation of benign early repolarization versus acute myocardial infarction by emergency physicians and cardiologists

OBJECTIVES

ST-segment elevation (STE) related to benign early repolarization (BER), a common normal variant, can be difficult to distinguish from acute myocardial infarction (AMI). The authors compared the electrocardiogram (ECG) interpretations of these two entities by emergency physicians (EPs) and cardiologists.

METHODS

Twenty-five cases (13 BER, 12 AMI) of patients presenting to the emergency department with chest pain were identified. Criteria for BER required four of the following: 1) widespread STE (precordial greater than limb leads), 2) J-point elevation, 3) concavity of initial up-sloping portion of ST segment, 4) notching or irregular contour of J point, and 5) prominent, concordant T waves. Additional BER criteria were 1) stable ECG pattern, 2) negative cardiac injury markers, and 3) normal cardiac stress test or angiography. AMI criteria were 1) regional STE, 2) positive cardiac injury markers, and 3) identification of culprit coronary artery by angiography in less than eight hours of presentation. The 25 ECGs were distributed to 12 EPs and 12 cardiologists (four in academic medicine, four in community practice, and four in community academics [health maintenance organization] in each physician group). The physicians were informed of the patients' age, gender, and race, and they then interpreted the ECGs as BER or AMI. Undercalls (AMI misdiagnosed as BER) and overcalls (BER misdiagnosed as AMI) were calculated for each physician group.

RESULTS

Cardiologists correctly interpreted 90% of ECGs, and EPs correctly interpreted 81% of ECGs. The proportion of undercalls (missed AMI/total AMI) was 2.8% for cardiologists (95% confidence interval [CI] = 0.09% to 5.5%) compared with 9.7% for EPs (95% CI = 4.8% to 14.6%) (p = 0.02). The proportion of overcalls (missed BER/total BER) was 17.3% for cardiologists (95% CI = 11.4% to 23.3%) versus 27.6% for EPs (95% CI = 20.6% to 34.6%) (p = 0.03). The mean number of years in practice was 19.8 for cardiologists (95% CI = 19 to 20.5) and 11 years for EPs (95% CI = 10.5 to 12.0) (p < 0.001).

CONCLUSIONS

Although correct interpretation was high in both groups, cardiologists, who had significantly more years of practice, had fewer misinterpretations than EPs in distinguishing BER from AMI electrocardiographically.

ST Segment and T Wave Abnormalities Not Caused by Acute Coronary Syndromes

This article reviews the ST segment and T wave abnormalities seen in non-acute coronary syndrome (ACS) electrocardiograph presentations. Particular emphasis is placed on the distinction of these non-ACS syndromes from acute coronary syndrome related ST segment and or T wave change.

The athlete's electrocardiogram

The electrocardiogram performed in the competitive athlete may manifest abnormal electrocardiographic findings; these findings may indicate either normal variant syndromes as well as true cardiac pathology. The normal variant syndromes include ST-segment and T-wave abnormalities, rhythm disturbances, and intraventricular conduction delay--it must be stressed that these electrocardiographic findings are, in fact, normal variants, not indicative of underlying pathology. Other presentations in these same competitive athletes describe significant cardiac pathology, including syndromes predisposing the patient to sudden cardiac death and other potentially dangerous dysrhythmias and diagnostic of acute coronary syndrome. This article reviews the various findings in this group of patients.

Vectorcardiography risk stratifies emergency department chest pain patients with left ventricular hypertrophy on the initial 12-lead ECG

BACKGROUND

Vectorcardiographic (VCG) measurements of ST-vector magnitude (VM) and QRS-vector difference (VD) have been demonstrated to be independent predictors of adverse outcome (AO) and acute myocardial infarction (AMI) in emergency department (ED) chest pain patients with absence of bundle branch block or left ventricular hypertrophy (LVH) on the initial 12-lead electrocardiogram (ECG). The prognostic value of ST-VM and QRS-VD in ED chest pain patients with LVH on the initial 12-lead ECG has not been previously investigated.

METHODS

A prospective observational study was performed in 196 consecutive ED chest pain patients with suspected AMI and presence of voltage criteria for LVH on initial ECG who underwent continuous VCG monitoring during the initial evaluation. The optimal baseline ST-VM value and 2-hour QRS-VD value were defined as the most accurate value on the receiver operator characteristic curve (value with lowest false-negative and false-positive rate). Thirty-day AO was defined as AMI, percutaneous coronary intervention, coronary artery bypass grafting (CABG), or cardiac death occurring within 30 days of initial ED visit.

RESULTS

Fourteen patients (7.1%) were diagnosed as 24-hour AMI and 28 patients (14.3%) experienced 30-day AO. The optimal cut-off value for predicting 30-day AO was > 124 microV for ST-VM and > 21.7 microV for QRS-VD. Patients with either a positive ST-VM or a positive QRS-VD had 8.8 times increased odds of AMI (95% confidence interval, CI, 1.9-40.3; P = 0.003); 4.3 times increased odds of 30-day PTCA/CABG (95% CI 1.3-13.8; P = 0.019); and 3.8 times increased odds of 30-day AO (95% CI 1.6-9.3; P = 0.003).

CONCLUSIONS

Baseline ST-VM and 2-hour QRS-VD risk stratifies ED chest pain patients with LVH voltage criteria on the initial 12-lead ECG.

Electrocardiographic ST segment elevation: a comparison of AMI and non-AMI ECG syndromes

Chest pain (CP) patients presenting to the ED may manifest electrocardiographic ST segment elevation (STE). AMI (acute myocardial infarction) is a less frequent cause of such abnormality and one of many patterns responsible for ST segment elevation in ED CP patients. We performed a retrospective comparative review of the electrocardiographic features of various STE syndromes, focusing on differences between AMI and non-AMI syndromes. The electrocardiograms (ECGs) of consecutive ED adult CP patients (with 3 serial troponin I determinations) were interpreted by 3 attending emergency physicians. These ECGs with STE represented the study population used for analysis. Various electrocardiographic features such as STE, ST segment depression (STD), STE morphology, anatomic distribution of STE, and the number of leads with STE were recorded; derived values such as total STE, total ST segment deviation, and average STE per lead were calculated. Interobserver reliability concerning STE morphology was determined. AMI was diagnosed by abnormal serum troponin I values (>0.1 mg/dL) followed by a rise and fall of the serum marker; STE diagnoses of non-AMI causes were determined by medical record review. Five hundred ninety-nine CP patients were entered in the study with 212 (35%) individuals showing STE, 55 (26%) with electrocardiographic AMI and 157 (74%) with non-AMI electrocardiographic syndromes. Anatomic location within the AMI group included 32 inferior and inferior variants, 18 anterior and anterior variants, and 5 lateral; non-AMI anatomic locations included 56 inferior and inferior variants, 98 anterior and anterior variants, and 3 lateral; anterior STE occurred significantly more often in non-AMI syndromes. Total STE was 15.3 mm in AMI patients and 7.4 mm in non-AMI patients (P =.0004). The number of leads with STE was not significantly different between the two groups, 3.4 mm in AMI and 4.1 in non-AMI syndromes. ST segment elevation per lead was not significantly different in the 2 groups, 4.4 mm in AMI versus 1.8 mm in non-AMI syndromes. Total ST segment deviation (sum of STE and STD) was significantly greater in AMI syndromes, 17.8 mm in AMI compared with 10.5 mm in non-AMI syndromes (P =.00009). The presence of STD occurred at statistically similar rates in both groups. The morphology of the STE occurred in significantly different rates between AMI and non-AMI patterns, concave more often in non-AMI patterns (P <.00001) and nonconcave more often in AMI (P <.00001). Non-AMI causes of STE account for the majority of electrocardiographic syndromes encountered in ED chest pain patients. These findings alone are not adequate to determine the electrocardiographic cause of the ST segment elevation in chest pain patients. When determining AMI versus non-AMI with the ECG, these various findings should be used in the consideration of the overall clinical picture (history, examination, and electrocardiogram) in chest pain patients with ST segment elevation.

Use of baseline ST-vector magnitude to identify electrocardiographic injury in patients with suspected acute myocardial infarction

No information is currently available regarding optimal cut-off values of the ST-vector magnitude (ST-VM) for predicting acute myocardial infarction (AMI) in emergency department (ED) chest pain patients undergoing vectorcardiographic (VCG) monitoring. A prospective observational study was performed in 1,722 chest pain patients with suspected acute coronary syndrome and absence of bundle branch block (BBB) and left ventricular hypertrophy (LVH) on initial ECG who underwent continuous VCG ST-segment monitoring during the initial ED evaluation. Three cut-off values for baseline ST-VM are reported and represent the smallest values in which the positive likelihood ratio (+LR) for AMI is greater than 5, 10, and 20, respectively. AMI occurred in 158 of 1,722 patients (9.2%) without BBB or LVH on initial ECG. Optimal cut-off values at the predetermined +LR values of 5, 10, and 20, were 121 microV (sensitivity, 41.8%; specificity, 92.0%), 151 microV (sensitivity, 29.1%; specificity, 97.1%), and 175 microV (sensitivity, 25.9%; specificity, 98.7%), respectively. Combining the earlier-mentioned cut-off values with physician judgment of initial pretest probability (high, intermediate, or low, respectively) resulted in a relative increase in identification of injury of 37.5% as compared with the ED physician's interpretation of initial ECG (41.8% v 30.4%; P <.0001), and 65.2% as compared with the official ECG interpretation (41.8% v 25.3%; P <.0001). Increasing ST-VM results in increasing likelihood of AMI. Clinical studies need to be performed to determine if ST-VM cut-off values of 121, 151, and 175 microV in conjunction with physician pretest probability of AMI can be used as criterion for emergent reperfusion therapy in patients without LVH or BBB on the initial ECG.

The prominent T wave: electrocardiographic differential diagnosis

The prominent T wave is an abnormal T-wave morphology encountered in the earliest phase of ST-segment elevation acute myocardial infarction (AMI). Prominent T waves, however, are associated with other diagnoses, including hyperkalemia, early repolarization, and left ventricular hypertrophy (LVH). This article focuses on the electrocardiographic differential diagnosis of the prominent T wave with the presentation of 4 illustrative cases. We also recommend that the designation hyperacute should refer exclusively to the prominent T waves of ST-segment elevation AMI.

Variation in patient management based on ECG interpretation by emergency medicine and internal medicine residents

This study was performed to determine the impact of electrocardiogram (ECG) interpretation on urgent patient care decisions by internal medicine (IM) and emergency medicine (EM) resident physicians. Six clinical scenarios and ECGs were given to 31 IM residents and 31 EM residents at a university medical center. Based on the ECG interpretation, the residents were asked to select the best patient management from a list of choices. IM and EM residents were equally likely to choose the correct management for complete heart block (90% IM v 97% EM, P = NS), and pulseless ventricular tachycardia (VT) (94% IM v 97% EM, P = NS). IM residents were less likely to choose the correct management for acute posterior wall myocardial infarction (MI) (26% IM v 74% EM, P <.0001) and unstable supraventricular tachycardia (SVT) (87% IM v 100% EM, P <.05). Residents in both programs were equally likely to misinterpret left ventricular hypertrophy (LVH) (23% IM and 16% EM, P = NS) and benign early repolarization (BER) (48% IM and 52% EM, P = NS) as acute myocardial ischemia when presented with a clinical history not suggestive of cardiac ischemia. IM and EM residents were equally likely to choose the correct management for complete heart block and pulseless VT. Compared with EM residents, IM residents were less likely to choose the correct management of posterior wall MI and unstable SVT. Both IM and EM residents were prone to misinterpreting LVH and BER as acute myocardial ischemia. Resident education in both specialties should focus on ECG interpretation skills to improve patient management decisions.

Serial electrocardiography

During the past 15 years, medicine has witnessed several important advances in coronary artery reperfusion therapy for acute myocardial infarction (AMI). Both percutaneous transluminal coronary angioplasty (PTCA) and thrombolytic therapy have made significant advances in the early treatment of the AMI patient. Given both the shown benefit of these treatment modalities and the cardiac injury that they can prevent, it behooves the emergency physician (EP) to make a timely diagnosis of AMI to restore adequate perfusion and to salvage the maximum amount of myocardium. A correct diagnosis is dependent on EP expertise in the evaluation of the chest pain patient--in large part, the electrocardiogram.

Ethnic differences in the ST segment of the electrocardiogram: a comparative study among six ethnic groups

Deviation of the ST segment of the electrocardiogram (ECG) may signify infarction or ischemia. Prior studies suggest that normal ECG patterns may differ among ethnic groups. We retrospectively reviewed the first thousand medical files of a multiethnic community, where all individuals shared similar living conditions. Only healthy adults, aged 15 to 60 years, were included. Along with age, the most common causes for exclusion were diabetes, hypertension, and ischemic heart disease. A total of 597 subjects (349 men) were included: 350 Saudi Arabians, 39 Filipinos, 95 Indians, 17 Sri-Lankans, and 57 Caucasians. Twenty men and one woman had an ECG pattern of early repolarization (ST segment elevation with upward concavity, notching on QRS, and large symmetrical T wave), with no difference in incidence among ethnic groups. ST segment elevation (2 mm in any of the leads V1-V4, or 1 mm in any of the other leads) without criteria of early repolarization occurred in 11.58%, 13.46%, 3.57%, 4.35%, 11.76%, 7.32% of Saudi, Indian, Jordanian, Filipino, Sri-Lankan, and Caucasian men, respectively (P =.61). Only one Jordanian and 2 Indian women had this pattern. However, Filipino men had higher median ST segment levels than others in leads V1 and V3. Among women, the median ST segment level was iso-electric in all leads in all ethnic groups. Only 3 subjects had ST segment depression >1 mm. Significant ST segment elevation is common in normal healthy men but may not fulfill criteria for early repolarization; it has no ethnic predilection. ST segment elevation is uncommon in normal women. ST segment depression is a rare finding in healthy adults regardless of ethnic origin.

ELECTROCARDIOGRAPHIC DIAGNOSIS OF ACUTE MYOCARDIAL INFARCTION

The widely recognized benefits of early diagnosis and treatment of acute myocardial infarction (AMI) have only emphasized the importance of emergency physician (EP) competence in electrocardiographic interpretation. As such, the EP must be an expert in the interpretation of the electrocardiogram (ECG) in the emergency department chest pain center patient. The ECG is a powerful clinical tool used in the evaluation of patients, assisting in making the diagnosis of AMI and other syndromes, selecting appropriate therapies (including thrombolysis and primary angioplasty), securing the location of an adequate inpatient disposition, and predicting the risk of cardiovascular complications and death. This article will discuss the appropriate uses of the ECG in the patient with possible or confirmed AMI and review the typical electrocardiographic findings of AMI, diagnostically confounding patterns, mimickers of infarction, and new techniques.

Electrocardiographic ST-segment elevation: correct identification of acute myocardial infarction (AMI) and non-AMI syndromes by emergency physicians

OBJECTIVE

To determine the emergency physician's (EP's) ability to identify the cause of ST-segment elevation (STE) in a hypothetical chest pain patient.

METHODS

Eleven electrocardiograms (ECGs) with STE were given to EPs; the patient in each instance was a 45-year-old male with a medical history of hypertension and diabetes mellitus with the chief complaint of chest pain. The EP was asked to determine the cause of the STE and, if due to acute myocardial infarction (AMI), to decide whether thrombolytic therapy (TT) would be administered (the patient had no contraindication to such treatment). Rates of TT administration were determined; appropriate TT administration was defined as that occurring in an AMI patient, while inappropriate TT administration was defined as that in the non-AMI patient.

RESULTS

Four hundred fifty-eight EPs completed the questionnaire; levels of medical experience included the following: postgraduate year 2-3, 193 (42%); and attending, 265 (58%). The overall rate of correct interpretation of the study ECGs was 94.9% (4,782 correct interpretations out of 5,038 instances). Acute myocardial infarction with typical STE, ventricular paced rhythm, and right bundle branch block were never misinterpreted. The remaining conditions were misinterpreted with rates ranging between 9% (left bundle branch block, LBBB) and 72% (left ventricular aneurysm, LVA). The overall rate of appropriate thrombolytic agent administration was 83% (1,525 correct administrations out of 1,832 indicated administrations). The leading diagnosis for which thrombolytic agent was given inappropriately was LVA (28%), followed by benign early repolarization (23%), pericarditis (21%), and LBBB without electrocardiographic AMI (5%). Thrombolytic agent was appropriately given in all cases of AMI except when associated with atypical STE, where it was inappropriately withheld 67% of the time.

CONCLUSIONS

In this survey, EPs were asked whether they would give TT based on limited information (ECG). Certain syndromes with STE were frequently misdiagnosed. Emergency physician electrocardiographic education must focus on the proper identification of these syndromes so that TT may be appropriately utilized.

Electrocardiographic manifestations: patterns that confound the EKG diagnosis of acute myocardial infarction-left bundle branch block, ventricular paced rhythm, and left ventricular hypertrophy

The 12-lead electrocardiogram (EKG), a powerful tool used in evaluating the chest pain patient, has its shortcomings. One such failing is encountered in a patient with one of the following electrocardiographic patterns: left bundle branch block (LBBB), ventricular paced rhythm (VPR), and left ventricular hypertrophy (LVH). These patterns reduce the ability of the EKG to detect acute coronary ischemic change and acute myocardial infarction (AMI). Several strategies are available to assist in the correct interpretation of these complicated electrocardiographic patterns, including a knowledge of the ST segment-T wave changes associated with these confounding patterns, performance of serial EKGs, and comparison with previous EKGs if available. This article suggests guidelines and interpretive tools for diagnosing AMI on EKG in patients with these confounding patterns.