Division of Pediatric Emergency Medicine, Department of Emergency Medicine, University of South Alabama, Mobile, AL, USAUnited States
Department of Pediatrics, University of South Alabama, Mobile, AL, USAUnited States
Baugh Biomedical Library, University of South Alabama, Mobile, AL, USAUnited States
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Objectives The electrocardiogram (ECG) of patients with hypertrophic cardiomyopathy (HCM) ranges from normal to exhibiting evidence of ventricular hypertrophy, including pathologic Q waves and ST-T wave changes. Deep Q waves in the inferior and lateral leads are one of the classic ECG findings associated with HCM. The prevalence or frequency of this finding in pediatric HCM patients, however, is not well-established. Furthermore, other pediatric health conditions have also been associated with pathologic and non-pathologic Q waves and an awareness of those conditions is important to consider when Q waves are observed. The primary goal of this systematic review of the literature is to describe the prevalence of pathologic Q waves in the ECGs of pediatric patients with echocardiogram proven HCM. A secondary goal is to review other pediatric conditions that can present with pathologic and non-pathologic Q waves. Methods The databases PubMed, Web of Science, Scopus and cumulative index to nursing and allied health literature (CINAHL) were searched utilizing the preferred reporting items for systematic reviews and meta-analyses (PRISMA) format. The Rayyan systemic review software was used to screen articles for final review. The initial search (Search 1) consisted of the following terms: “dagger Q wave”, “dagger-like Q waves”, “dagger shape Q waves”. Subsequently, a broader search (Search 2) was conducted to determine if viable articles were omitted in the first search. This broader search strategy eliminated the term “HCM”. The authors then performed detailed review of the articles these two searches yielded, as well as a review of the references of these articles to find other relevant articles as well as produce a list of other pediatric conditions that may be associated with pathologic or non-pathologic Q waves. Results Of the articles found via the three searches, a total of nine English language articles that specifically addressed the prevalence of pathological Q waves in pediatric HCM patients were ultimately included in our systematic review. These nine articles described a total of 845 pediatric patients with HCM. Of these, 258 (30.5%) demonstrated pathological Q waves on their electrocardiograms. The range of percentages reported for pathological Q waves was 12.5 to 66.7%. Additionally, our review found fifteen different pediatric conditions reported to be associated with pathologic or non-pathologic Q waves. Conclusion Our systematic review confirmed that pathologic Q waves are a common and early electrocardiographic finding in children with HCM and may, in fact, be the only ECG finding. In addition, our review provided an extensive list of other pediatric diseases and conditions associated with pathologic or non-pathologic Q waves on the electrocardiogram.
Keywords: Hypertrophic cardiomyopathy; Q wave; Pathologic Q wave; Sudden cardiac death; Pediatric
The databases PubMed, Web of Science, Scopus and cumulative index to nursing and allied health literature (CINAHL) were searched utilizing the preferred reporting items for systematic reviews and meta-analyses (PRISMA) format. The Rayyan systemic review software was used to screen articles for final review. The initial search (Search 1) consisted of the following terms: “dagger Q wave”, “dagger-like Q waves”, “dagger shape Q waves”. Subsequently, a broader search (Search 2) was conducted to determine if viable articles were omitted in the first search. This broader search strategy eliminated the term “HCM”. The authors then performed detailed review of the articles these two searches yielded, as well as a review of the references of these articles to find other relevant articles as well as produce a list of other pediatric conditions that may be associated with pathologic or nonpathologic Q waves.
Of the articles found via the three searches, a total of nine English language articles that specifically addressed the prevalence of pathological Q waves in pediatric HCM patients were ultimately included in our systematic review. These nine articles described a total of 845 pediatric patients with HCM. Of these, 258 (30.5%) demonstrated pathological Q waves on their electrocardiograms. The range of percentages reported for pathological Q waves was pediatric conditions reported to be associated with pathologic or
Our systematic review confirmed that pathologic Q waves are a common and early electrocardiographic finding in children with HCM and may, in fact, be the only ECG finding. In addition, our review provided an extensive list of other pediatric diseases and conditions associated with pathologic or non-pathologic Q waves on the electrocardiogram.
Hypertrophic cardiomyopathy; Q wave; Pathologic Q wave; Sudden cardiac death; Pediatric.
cc Copyright 2022 by Mellick LB. This is an open-access article distributed under Creative Commons Attribution 4.0 International License (CC BY 4.0), which 12.5 to 66.7%. Additionally, our review found fifteen different non-pathologic Q waves.
waves indicate the depolarization of the interventricular septum1 and in neonates may be a normal finding in the inferior Q and left lateral leads. They should not, however, be wide or deep. The normal Q wave duration is 0.02 seconds and does not exceed 2-5 0.03 seconds2-5 and voltages vary based on age but should never exceed 0.15 mV in an infant or 0.1 mV in a teenager.5 Although prominent Q waves are a characteristic finding in myocardial infarction, they can be seen in other disease states and serve as a screening tool for a spectrum of pathology.
There are several possible explanations for the Q waves found in the setting of hypertrophic cardiomyopathy (HCM), but most agree that the Q waves are generated by the increased electrical forces of disproportionate hypertrophy of the basal septum as well as the ventricular free wall found in HCM.5-7
Currently, the Seattle criteria8 are most frequently used to delineate abnormal Q waves (Q waves >3 mm deep and/or >40 ms duration in ≥2 leads except III and a VR), as originally proposed by Charron et al9 and found to be the most sensitive criteria for abnormal Q waves in pediatric patients.10
In this systematic review, we had two research goals.
The first was to describe the reported prevalence of pathologic Q waves in the electrocardiograms (ECGs) of pediatric patients with echocardiogram proven HCM. The second goal was to perform an extensive review and report other pediatric conditions that can present with pathologic and non-pathologic Q waves.
Our paper is unique in that it is the first systematic review of the prevalence of pathologic Q waves in the ECGs of pediatric patients with echocardiogram proven HCM.
Figure 1. Results of Literature Search Performed Utilizing the PRISMA Format
The databases PubMed, Web of Science, Scopus and cumulative index to nursing and allied health literature (CINAHL) were searched utilizing the preferred reporting items for systematic reviews and meta-analyses (PRISMA) format.11 The publication dates ranged from inception to October 2019. We included retrospective and prospective studies, chart reviews, systemic reviews, and case series. Non-english or opinion articles were excluded. The Rayyan Systemic Review Software was used to screen articles for final inclusion in the review. Two search strategies were employed. The initial search (Search 1) consisted of the following terms: “dagger Q wave”, “dagger-like Q waves”, “dagger shape Q waves”, “deep Q wave”, “narrow Q wave” or “Q wave elevation” and “hypertrophic cardiomyopathy”. After reviewing those articles, a broader search (Search 2) was conducted 5-7 to determine if viable articles were omitted in the first search. This broader search strategy included the same terms as Search 1 but eliminated the term “HCM” (Figure 1). The authors then performed an exhaustive manual review of the articles gleaned from these two searches to find other references that met the two research goals.
Search one yielded 55 articles, all of which were screened by the authors. Of these, only 4 were found eligible for full-text 10,12-14 assessment by both reviewers. Search Two yielded 343 articles, all of which were screened by the authors. Of these, only 15-17 3 were found eligible for full-text assessment by both reviewers. A manual search of the literature was also performed by two of the authors. This yielded six additional articles that discussed pathologic Q wave abnormalities. Of all the articles found in the three searches, a total of nine articles ultimately specifically addressed the prevalence of pathological Q waves in pediatric
Table 1. Studies Reporting Pediatric Patients with Pathological Q Waves
9 2/16 (12.5%) Charron et al
10 7/15 (46.6%) Konno et al
Balagi et al 107/446 (23.99%) 13 9/40 (22.5%) Phenotype positive voltage Guerrier et al
Shimizu et al 4/6 (66.7%)
Thompson et al 31/148 (21%)
Dipchand et al 16/37 (43%) 21 18/44 (40.9%) school screening 23/44 Morimoto et al 22 59/93 (63.4%) Yetman et al Total 258/845 (30.5%)
9,10,12,13,18-22 HCM patients (Table 1). These nine articles described a total of 845 pediatric patients with hypertrophic cardiomyopathy. Of these, 258 (30.5%) demonstrated pathological Q waves on their electrocardiograms. The range of percentages reported for pathological Q waves was 12.5 to 66.7%. The Seattle criteria8,23 was used to delineate pathological Q waves in seven of 9 articles.
The second aim of our review is to list all pediatric conditions that may be associated with Q waves, both nonpathological and pathological by the Seattle criteria. Q waves can be normal in some age groups. Neonates normally have small Q waves in the inferior (II, III, aVF), and lateral (V5 and V6) leads. Deep Q waves in V5 and V6 can be seen with improperly (too high) placed leads. However, Q waves in other leads can signify disease. Deep Q waves can be found in patients with disorders such as infiltrative myocardial diseases, accessory pathways, arrhythmogenic right ventricular cardiomyopathy, and transmural myocardial infarction. Although the ECGs of athletes frequently meet the criteria for left ventricular hypertrophy, Q waves are 26,27 28 relatively uncommon. However, Pelliccia et al found that a deep Q wave can be found in about 10% of trained athletes in the
Table 2. Conditions Associated with Q Waves on ECG Derived from Literature Search
2 8,17,23,28 Core pulmonale Athletic heart 15 24 Duchene muscular dystrophy Incorrect lead placement Anomalous origin left coronary artery Myocardial infarction 32,33 31 (ALCAPA) 34 34 Hypertrophic cardiomyopathy Idiopathic dilated cardiomyopathy 35 36,37 Tricuspid atresia Normal variant 37 38 Kawasaki disease37 Dextrocardia38 39 40 Myocarditis39 Left ventricular aneuysm40 Spinal muscular atrophy
Q waves >3 mm or duration > 0.04 second, and present in > 2 leads.Q waves present only in V1 and V2 or only in lead III were not considered as abnormal.
Q wave >3 mm in depth and/or >0.04 s in duration in at Visual estimate from chart least two leads except aVR Q waves either >25% of the size of the R wave or >3 mm in any of the inferior leads (II, III, and aVF) Q waves >3 mm in depth or >40 ms in two or more leads and non-voltage Q wave abnormalities Q wave >0.04 second in duration or >25% of the ensuring R wave in depth in at least 2 leads except aVR.
Q waves >3 mm deep or 40 ms in duration in ≥2 leads excluding III and aVR th The Q wave in lead III was > 95 percentile.
Q waves >3 mm deep and/or >40 ms duration in ≥2 leads (52.3%) last eval except III and aVR Prominent inferolateral Q-wave
absence of any changes on two-dimensional echocardiogram, suggesting that Q waves can be a non-pathologic consequence of athletic training. Table 2 lists in addition to HCM other pediatric conditions that can present with Q waves on ECG.
8,23
The evidence suggests that Q waves >3 mm in depth or 0.40 ms in duration in at least two leads may be the most accurate diagnostic 10,13 13 definition for HCM. Guerrier et al found that voltage-based ECG criteria were associated with a low sensitivity but a high specificity for HCM; specifically, Q waves >3 mm in depth in two or more leads had a sensitivity of 13% and a specificity of 100%, whereas Q waves >40 ms had a sensitivity of 10% but a specificity of 100%.
The recognition of HCM is critical as it is the single most common cardiac cause of sudden death, especially in young patients. The diagnosis of HCM is often based on the presence of unexplained left ventricular hypertrophy which usually does not develop until late adolescence or adulthood.29 An abnormal electrocardiogram is often the first evidence of this disease and abnormal Q waves may be one of the earliest ECG findings to 18,29,30 suggest HCM. Therefore, abnormal Q waves can be helpful in finding preclinical carriers of HCM.
Konno et al reported that in the young population, abnormal Q waves, compared to other ECG abnormalities, showed the highest sensitivity (50%) and specificity (90%) for HCM, in contrast to the adult population where abnormal Q waves showed the lowest sensitivity (29%), a high specificity (97%) and the lowest accuracy (52%). Shimizu et al reported in a smaller study that the sensitivity, specificity, positive predictive value, and negative predictive value of abnormal Q waves in teens were 67%, 100%, 100% and 78%, respectively. Abnormal Q waves were frequently observed in leads II, III, aVF, V5, and V6 in teenage patients, whereas they were observed in many leads in patients >20-years
18 29 old. Lakdawala et al reported that in overt HCM, 75% had Q waves and/or repolarization changes, but <25% demonstrated common isolated voltage criteria for LVH. In conclusion, Q waves and repolarization abnormalities are the most discriminating ECG features of sarcomere mutation carriers with and without LVH.
Despite two slightly different systematic reviews of the literature, it is still possible that other relevant articles may have been missed as evidenced by the fact that the majority of the relevant articles were discovered by a careful and detailed manual search.
The papers available, reviewed and selected for the systematic review were overall low to moderate quality.
Minimal heterogeneity of the definition of abnormal Q wave definitions existed, but most articles reported in our review used the Seattle criteria (Q waves >3 mm deep and/or >40 ms duration in ≥2 leads except III and aVR). Five of the articles included in Table 1 were published prior to 2013 when the Seattle criteria 9,10,18,20,22 were first formalized. However, three of the earlier studies 9,10,18 did apply the Seattle criteria The remaining two studies either th 20 used Q waves at the 95 percentile as their criteria or reported prominent Q waves.
The diagnosis of Hypertrophic Cardiomyopathy requires a high index of suspicion by the emergency physician as it is a potentially fatal condition. However, there are relatively few articles that specifically address the diagnostic importance of Q waves in the pediatric population with hypertrophic cardiomyopathy. Our systematic review confirms that pathologic Q waves are a common and early electrocardiographic finding in children with HCM. In fact, pathologic Q waves may initially be the only ECG findings. Consequently, the importance of this ECG finding cannot be over emphasized in the early diagnosis of this condition.
Finally, while it is essential to be familiar with the ECG criteria for HCM, it is also important to note that Q waves in pediatric electrocardiograms have other potential etiologies as evidenced by our secondary search. Many of these etiologies are pathologic and require a detailed history, complete physical examination, and additional diagnostic testing.
The authors have no financial interest concerning the material in this work.
The authors declare that they have no conflicts of interest.