Expert Answer :Journal review

  

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Journal Article Grading Rubric
2
Length 3-4 paragraphs.
Reference, and article or
URL given. Technical
terminology and
formalism are used
correctly.
1
Somewhat too long or
short. Reference or
article/URL given.
Small number of errors
in terminology or
formalism.
0
Much too long or short.
No reference or article
given. Terminology,
formalism frequently
misused.
Understanding of
article
Chosen point identified
and clearly explained.
Factually correct as
report of chosen aspect
of article. Explains
chosen point; goes
beyond merely
paraphrasing or quoting.
Class knowledge used
correctly where
appropriate.
Chosen point identified,
but explanation not fully
clear. Minor errors in
report of authors’
meaning. Chosen point
paraphrased in student’s
own words, but very
close to original. Minor
misunderstandings
related to class
knowledge.
No point identified, or
explanation very
unclear. Major errors in
report of authors’
meaning. Relies on
quotations or superficial
paraphrase; little
evidence of
understanding. Major
problems from not
applying class
knowledge.
Active and critical
thinking;
argumentation
Goes beyond summary;
includes critique,
connects to other data or
ideas. Tight focus on
main point. Report is
well organized;
paragraphs and overall
discussion is focused,
coherent. Examples,
data used appropriately.
Shows understanding of
relevant issues, but
contributes no
substantial original
points. Focus is
somewhat loose. Some
organization, but
relationships between
ideas not always clear.
Crucial examples, data
not always given.
Critical discussion
missing, or shows
serious
misunderstanding of
article. No clear focus.
Structure of discussion
has no clear
organization. Examples
used, but not connected
to discussion.
Writing
Clear articulate writing
used. One or two minor
edits needed to be a
perfect paper! Keep up
the great work
Edits needed. Proof
reading will help you.
Read aloud to yourself
and or ask others to read
it out loud to you.
Turns in something. Not
college level work at all.
Get help at the writing
center.
Your Thoughts
Articulates your
thoughts on the article
in a clear manner.
Discusses what you
learned from reading the
article or ideas you
might use in the future.
Brief mention of
thoughts, but did not
elaborate. No mention
of learning from reading
the article.
Does not write any of
your own thoughts or
ideas about what is
discussed in the article.
Basic Mechanics
The Journal of Emergency Medicine, Vol. 51, No. 1, pp. 1–8, 2016
! 2016 Elsevier Inc. All rights reserved.
0736-4679/$ – see front matter
http://dx.doi.org/10.1016/j.jemermed.2016.02.029
Original
Contributions
COMPARISON OF THE QRS COMPLEX, ST-SEGMENT, AND T-WAVE AMONG
PATIENTS WITH LEFT BUNDLE BRANCH BLOCK WITH AND WITHOUT ACUTE
MYOCARDIAL INFARCTION
Kenneth W. Dodd, MD,*† Kendra D. Elm, BS,*‡ and Stephen W. Smith, MD*‡
*Department of Emergency Medicine, Hennepin County Medical Center, Minneapolis, Minnesota, †Department of Internal Medicine,
Hennepin County Medical Center, Minneapolis, Minnesota, and ‡Department of Emergency Medicine, University of Minnesota Medical
School, Minneapolis, Minnesota
Reprint Address: Kenneth W. Dodd, MD, Department of Emergency Medicine, Hennepin County Medical Center, 701 Park Avenue,
Minneapolis, MN 55415
, Abstract—Background: The modified Sgarbossa
criteria have been validated as a rule for diagnosis of acute
coronary occlusion (ACO) in left bundle branch block
(LBBB). However, no analysis has been done on differences
in the QRS complex, T-wave, or ST-segment concordance of
< 1 mm in the derivation or validation studies. Furthermore, there was no comparison of patients with acute myocardial infarction (AMI) but without ACO (i.e., non–ST-elevation myocardial infarction [non-STEMI]) to patients with ACO or without AMI (no MI). Objective: We compare findings involving the QRS amplitude, ST-segment morphology, ST-concordance < 1 mm, and T-waves in patients with LBBB with ACO, non-STEMI, and no MI. Methods: Retrospectively, emergency department patients were identified with LBBB and ischemic symptoms but no MI, with angiographically proven ACO, and with non-STEMI. Results: ACO, non-STEMI, and no MI groups consisted of 33, 24, and 105 patients. The sum of the maximum deflection of the QRS amplitude across all leads (SQRS) was smaller in patients with ACO than those without ACO (101.5 mm vs. 132.5 mm; p < 0.0001) and a cutoff of SQRS < 90 mm was 92% specific. For ACO, non-concave ST-segment morphology was 91% specific, any ST concordance $ 1 mm was 95% specific, and any ST concordance $ 0.5 mm was 94% sensitive. For non-STEMI, terminal T-wave concordance, analogous to biphasic T-waves, was moderately sensitive at 79%. Conclusions: We found differences in QRS amplitude, ST-segment morphology, and T-waves between patients with LBBB and ACO, nonSTEMI, and no MI. However, none of these criteria outperformed the modified Sgarbossa criteria for diagnosis of ACO in LBBB. ! 2016 Elsevier Inc. All rights reserved. , Keywords—left bundle branch block; acute myocardial infarction; QRS complex; ST-segment; T-wave INTRODUCTION The electrocardiogram (ECG) remains the fastest tool for early diagnosis of acute myocardial infarction (AMI). Historically, the belief that left bundle branch block (LBBB) hopelessly obscures the diagnosis of AMI by ECG has impeded work on this topic. The confusion has come because, at baseline, patients with LBBB exhibit discordance of the QRS complex, ST-segment, and T-wave. That is, patients with LBBB have ST-elevation in leads with negative QRS complexes (Figure 1) and ST-depression, as well as negative Twaves, in leads with positive QRS complexes. When this ‘‘rule of appropriate discordance’’ in LBBB is kept in mind, the diagnosis of acute coronary occlusion (ACO), which is the anatomic substrate for ST-elevation Kenneth W. Dodd and Kendra D. Elm contributed equally to this work. RECEIVED: 15 November 2015; FINAL SUBMISSION RECEIVED: 25 January 2016; ACCEPTED: 3 February 2016 1 2 K. W. Dodd et al. loss of specificity. Third, we hypothesized that nonconcave ST-segment morphology would not be a sensitive or specific marker of ACO, in contrast to previously
published guidelines (3). Fourth, we hypothesized that
patients with ACO would exhibit hyperacute T-wave
equivalents more frequently than non-ACO patients, as
manifested by an increased T-wave amplitude (TWA)
and discordant TWA/QRS-amplitude ratio (T/QRS).
Finally, we hypothesized that patients with non-STEMI
and LBBB would more frequently have concordant
T-waves, a presumed analogue to T-wave inversions in
ECGs with normal conduction.
METHODS
Study Design and Population
Figure 1. Diagram of measurements and morphologies. The
main diagram demonstrates normal discordance in left bundle
branch block with a negative maximum QRS amplitude (i.e., an
S-wave) and resulting positive T-wave, as well as concave STsegment elevation. Appropriate measurements are also
demonstrated: S-wave = 19 mm; ST = 1.5 mm; T-wave amplitude (TWA) = 9 mm; ST/S ratio = 1.5/19 = 0.08; discordant T/
QRS ratio (i.e., T/S ratio in this example) = 9/19 = 0.47. Morphologies of straight (A) and convex (B) ST-segments, as well as
majority T-wave concordance (C) and terminal T-wave concordance (D) are also shown.
myocardial infarction (STEMI), may be made with far
more accuracy than previously believed. The modified
Sgarbossa criteria were 91% sensitive and 90% specific
for diagnosis of ACO in LBBB in the derivation trial
(Table 1), and have recently been validated with 80%
sensitivity and 99% specificity (1,2). No specific
analysis of the QRS complex, ST-segment morphology,
concordant ST-deviation of <1 mm, or T-waves has been published from the derivation or validation data. In this study, we tested several hypotheses regarding ECG characteristics in patients with LBBB and AMI (either ACO or non–STEMI). First, we hypothesized that patients with ACO would have lower QRS voltage on the ECG. Second, we hypothesized that concordant ST-elevation or concordant ST-depression of $0.5 mm would be more sensitive for ACO than 1 mm, without This was a secondary analysis of data collected for the derivation of the modified Sgarbossa criteria (1). For this retrospective study, data were collected from patients who presented to the emergency department with LBBB (4), had symptoms suspicious for MI (e.g., chest pain or shortness of breath), and had an ECG recorded at the time of symptoms. The ACO (STEMI) group was defined as angiographically proven ACO (thrombolysis in MI 0 to 1 flow) or arterial stenosis with either thrombosis or ulcerated culprit lesion and peak 24-hour cardiac troponin-I level cutoff of >10 ng/mL (implying probable ACO at the
time of ECG).
The non-STEMI group consisted of patients who were
adjudicated as AMI by a study author (S.W.S) with 24-h
troponin-I > 99% upper reference limit (99% upper reference limit range was 0.1–0.6 ng/mL for assays used
during the study period) in which ACO was excluded
by either angiogram showing no culprit lesion, a lesion
but no angiographic occlusion and peak troponin
<10 ng/mL, or an urgent echocardiogram with no wall motion abnormality and peak troponin-I <10 ng/mL. The no-MI group consisted of consecutive patients presenting to Hennepin County Medical Center emergency department with chest pain or dyspnea between September 2000 and June 2003, who had all 24-h serial troponin-I measurements below the 99% upper reference limit and who met the study inclusion/exclusion criteria (1). Table 1. Performance Characteristics of the Modified Sgarbossa Criteria for Diagnosis of Acute Coronary Occlusion in Left Bundle Branch Block (1) Characteristic Sensitivity, % (95% CI) Specificity, % (95% CI) $1 mm concordant ST-elevation in any lead $1 mm concordant ST-depression in V1-3 ST/S ratio # !0.25 in any lead with $1 mm ST-elevation Modified Sgarbossa criteria: any one of the above 42 (26–61) 21 (10–39) 79 (61–91) 91 (76–98) 98 (94–99) 100 (96–100) 91 (84–95) 90 (83–95) CI = confidence interval. Diagnosis of Acute Myocardial Infarction in Left Bundle Branch Block Data Collection and Statistical Analysis The first ECG recorded during a patient’s presentation was used for measurements. A representative beat from each lead was chosen and the largest amplitude deflection of the QRS complex (either R-wave or S-wave), ST-segment at the J-point, and T-wave was measured to the nearest 0.5 mm (0.05 mV) with respect to the P–Q junction (see Figure 1 for measurements and calculations). If the T-wave was biphasic, both the positive and negative values were recorded. All values were entered as positive or negative with regard to their deflection from the isoelectric line. ‘‘Majority T-wave concordance’’ was defined as having the largest amplitude deflection of the T-wave in the same direction as the largest amplitude deflection the QRS complex. Similarly, ‘‘terminal T-wave concordance’’ was defined as a biphasic T-wave with the terminal portion >0.5 mm (0.05 mV) concordant to the largest
amplitude deflection of the QRS complex.
‘‘ST morphology’’ was determined by drawing a
straight line from the J-point to the apex of the T-wave
in leads with a negative QRS complex and positive
T-wave. The ST-segment was determined to be convex
if the ECG tracing fell above the line, straight if the tracing
fell on the line, or concave if the tracing fell below the line.
Leads with less than a 2-mm change in amplitude from the
J-point to the apex of the T-wave were excluded from analysis due to indistinct T-wave morphologies. The ECG was
considered ‘‘non-concave’’ if the tracing was either
straight or convex in one or more leads. The ECG was
classified as concave if all leads were concave (5,6).
The ‘‘sum of the QRS amplitude’’ was computed as
follows. For each lead, we chose a representative QRS
complex and measured the wave of largest amplitude
deflection (either the R-wave or S-wave). We took the absolute value of these measurements so that all were
positive numbers. On each patient’s ECG, we added these
numbers over all 12 leads for an overall QRS amplitude
sum (SQRS).
‘‘Maximum TWA’’ was calculated as the maximum
absolute value of TWA in any lead, whether the T-wave
was positive or negative. Similarly, the maximum
3
discordant T/QRS ratios were calculated: if the majority
of the QRS was positive, then we would divide a negative
T-wave by the (positive) R-wave amplitude; if the majority of the QRS was negative, then we would divide a positive T-wave by the (negative) S-wave amplitude.
TWA measurements were done by a trained medical
student research assistant (K.D.E.) and morphology analysis was completed by an emergency medicine resident
physician (K.W.D.). Both authors were blinded to the
patient groups during measurements. Remaining measurements were described previously (1).
Statistics were by McNemar’s test, Mann-Whitney
U test, Kruskal-Wallis, and two-tailed Fischer’s exact
test where appropriate. Continuous data were presented
as median with interquartile range (IQR). Sensitivity
and specificity were reported with a 95% confidence
interval (CI). Statistical significance was accepted at the
a = 0.05 level (type 1 error probability of 5%). Statistics
were performed using Microsoft Excel (version 14.4.7;
Microsoft Inc., Redmond, WA).
RESULTS
Characteristics of Study Groups
Among all sites, 33 patients with ACO were identified
and comprised the ACO group. Of these, 27 had complete
ACO on angiography and 6 had partial ACO with thrombosis or ulcerated culprit lesion and troponin-I >10 ng/
mL. There were 105 no-MI patients that had negative serial troponin-I for up to 24 h. An additional 24 patients
met adjudication criteria for non-STEMI. In total, 162 patients were included in the study. As reported in the original study, there was good inter-rater reliability of the
measurements (1). Patient characteristics for each group
are shown in Table 2.
QRS Amplitude in LBBB and ACO
For the sum of QRS amplitudes across all 12 leads
(SQRS), the median value was 101.5 mm (IQR 82.5–
115.5 mm) for ACO, 129.75 mm (IQR 103.4–142.3 mm)
for non-STEMI, and 132.5 mm (IQR 109.5–159.0 mm)
Table 2. Patient Characteristics
Characteristic
ACO
(n = 33)
Non-STEMI
(n = 24)
No MI
(n = 105)
Age, y (95% CI)
Mean no. (%)
Peak troponin-I, ng/mL (95% CI)
72.8 (68.4–77.2)
20 (61)
114.7 (65.3–164.1)
70.9 (66.2–75.7)
8 (33)
3.5† (2.34–4.66)
65.5* (61.8–69.2)
50 (48)
ACO = acute coronary occlusion; CI = confidence interval; n/a = not applicable; no MI = without acute myocardial infarction; nonSTEMI = non–ST-elevation myocardial infarction.
* p < 0.05 compared to ACO. † p < 0.001 compared to ACO. 4 K. W. Dodd et al. Table 3. Criteria for Diagnosis of Acute Coronary Occlusion vs. Non–Acute Coronary Occlusion in Left Bundle Branch Block Criteria QRS amplitude SQRS < 90 mm ST-segment concordance Concordant ST-elevation $ 0.5 mm in any lead Concordant ST-depression $ 0.5 mm in leads V1–V3 Concordant ST-depression $ 0 mm in leads V1–V3 Concordant ST-depression $ 0.5 mm in any lead Concordant ST-depression $ 1.0 mm in any lead Any concordance $ 0.5 mm Any concordance $ 1.0 mm ST-segment morphology Non-concave (convex or straight) ST-segment T-wave to QRS amplitude ratio Discordant T/QRS > 1.25
T-wave concordance
Majority T-wave concordance in any lead
T-wave concordance in leads V5 or V6
for no MI (p < 0.0001 for both non-STEMI and no MI compared with ACO). When non-ACO patients were compared with ACO patients, the median SQRS was also significantly higher for the non-ACO group (132.5 mm [IQR 108.5–156.5 mm]; p < 0.0001). Using a cutoff value of SQRS <90 mm resulted in >90% specificity for diagnosis of ACO (Table 3).
ST-Segment Concordance in LBBB and ACO
ST-segment concordance comparisons in LBBB with
ACO are found in Table 3. When a cutoff of $0.5 mm
of concordant ST-elevation was used in any lead or
$0.5 mm of concordant ST-depression in V1–V3, there
was no significant difference in sensitivity or specificity
when compared with the previously reported cutoffs of
$1 mm (p = NS, Tables 1 and 3). A composite rule
with combination of any concordance $0.5 mm or ST/
S ratio of # !0.25 yielded 100% (95% CI 87–100) sensitivity and 57% (95% CI 47–65) specificity for the diagnosis of ACO in LBBB.
Sensitivity, % (95% CI)
Specificity, % (95% CI)
33 (19–52)
92 (85–96)
64 (45–79)
24 (12–43)
39 (23–56)
70 (67–82)
61 (42–77)
94 (78–99)
73 (54–86)
92 (86–96)
99 (95–100)
85 (78–91)
75 (51–84)
95 (95–100)
70 (61–77)
95 (88–97)
55 (37–71)
91 (84–96)
45 (28–63)
93 (87–97)
76 (57–88)
49 (31–66)
62 (53–70)
79 (69–84)
p < 0.05). Using a cutoff of discordant T/QRS $1.25 yielded >90% specificity for ACO (Table 3). But this statistical difference in discordant T/QRS is entirely due to
the difference in QRS amplitudes.
T-Wave Concordance in LBBB
In non-STEMI compared with no MI, terminal T-wave
concordance of >0.5 mm in any lead was the most sensitive of all criteria analyzed (Table 4). This criterion, as
well as majority T-wave concordance in any lead and majority T-wave concordance in leads V5 or V6, was more
sensitive for diagnosis of non-STEMI than the modified
Sgarbossa criteria (p < 0.05 for all). As expected, majority T-wave concordance in any lead was less specific for ACO than the modified Sgarbossa criteria (p < 0.05, Table 3). T-wave concordance in V5 or V6 was less sensitive and less specific for ACO than the modified Sgarbossa criteria (p = NS). For diagnosis of any MI (i.e., ACO and non-STEMI) compared to no MI, the addition of terminal T-wave concordance to the modified Sgarbossa criteria resulted ST-Segment Morphology in LBBB and ACO Non-concave ST-segment morphology in at least one lead with ST-elevation $1 mm was present in 18 (55%) patients with ACO compared with 11 (9%) non-ACO patients (p < 0.05) resulting in >90% specificity (Table 3).
Table 4. Criteria for Diagnosis of Non–ST-Elevation
Myocardial Infarction vs. No Acute Myocardial
Infarction in Left Bundle Branch Block
T-Wave Amplitude and T-Wave Ratios in LBBB and ACO
Modified Sgarbossa criteria
Terminal T-wave
concordance in any lead
Majority T-wave
concordance in any lead
Majority T-wave
concordance in leads V5 or V6
The maximum TWA was similar for the ACO (9 mm
[IQR 6.5–11 mm]) and non-ACO groups (8 mm [IQR
6.5–11 mm]; p = NS). The median discordant T/QRS ratio was significantly larger for ACO (1.08 [IQR 0.8–1.5])
compared with non-ACO (0.70 [IQR 0.43–0.75];
Criteria
Sensitivity, % Specificity, %
(95% CI)
(95% CI)
8 (2–29)
79* (57–92)
88 (79–93)
47* (37–57)
46* (26–67)
64* (54–73)
29* (13–51)
79* (70–86)
* p < 0.05 compared to the modified Sgarbossa criteria. Diagnosis of Acute Myocardial Infarction in Left Bundle Branch Block Table 5. Rules for Diagnosis of Any Acute Myocardial Infarction vs. No Acute Myocardial Infarction in Left Bundle Branch Block Rules Modified Sgarbossa criteria Modified Sgarbossa criteria or majority T-wave concordance in any lead Modified Sgarbossa criteria or terminal T-wave concordance in any lead Sensitivity, % (95% CI) Specificity, % (95% CI) 54 (41–68) 79* (66–88) 88 (79–93) 56* (46–66) 91* (80–97) 43* (33–53) 5 reported that $1 mm concordant ST-elevation in at least one lead and $1 mm concordant ST-depression in leads V1–V3 has high specificity for ACO with relatively low sensitivity. In this study, we found that lowering the cutoff to $ 0.5 mm of concordant ST-elevation or ST-depression increased the sensitivity of these criteria, while retaining a relatively high specificity with each criterion analyzed independently. When a composite rule consisting of any concordance (ST-elevation or ST-depression) $ 0.5 mm or an ST/S rat ... Purchase answer to see full attachment

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