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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 31, No 6, November/December 2020
334
AFRICA
descending artery of the right coronary artery. However, isolated
posterior STEMI can occur if the culprit occlusion is in a
posterior lateral wall branch of the right coronary artery or in
the circumflex artery (as in this case). In a posterior STEMI, the
evolution of changes over days includes the development of a
dominant R wave in V1 (a reciprocal Q wave) or Q waves in V7
to V9 with a T wave that is usually upright in V1 (Table 1).
PE is an important differential diagnosis to be excluded in
the patient presenting with chest pain. This life-threatening
condition can be clinically indistinguishable from MI, as both
conditions may present with chest pain and/or dyspnoea. In
addition, a further confounder is that a massive PE can mimic a
MI on the ECG. Both posterior MI and PE could be associated
with a dominant R wave in V1 and ST and/or T-wave changes in
the anterior leads (Table 1).
Chronic pulmonary thromboembolic disease can cause right
ventricular hypertrophy (RVH) with a dominant R wave in
V1, but in acute PE the right ventricle has not had time to
hypertrophy. Severe cases of PE may cause incomplete or
complete right bundle branch block (RBBB).
8
However, RBBB
could also be caused by MI.
Occasionally, patients present with the pathognomonic
S
I
Q
III
T
III
(S wave in lead I, Q wave in lead III, T-wave inversion
in lead III), ST-segment changes and/or widespread T-wave
inversion. The mechanism for the ST-segment deviation and
T-wave inversion in the anterior leads seen in PE could be
explained by the strain on the right ventricle caused by the
sudden rise in pulmonary artery pressure.
9
Whenever suspected,
compacted tomography pulmonary angiography (CTPA) would
be the diagnostic modality of choice for PE.
2
As sinus tachycardia
is the most common ECG feature of acute PE, its absence makes
the diagnosis less likely.
8
Because biomarkers such as troponins and CK-MB could be
elevated in STEMI, NSTEMI and PE, they should not be relied
on as the sole diagnostic modality. In this setting, imaging such
as coronary angiography and/or CTPA should be performed.
10
Accurate diagnosis of STEMI, NSTEMI or acute PE allows
for the timely institution of appropriate therapy. STEMI requires
emergency revascularisation in the form of PCI, or thrombolysis
if a PCI centre cannot be accessed within two hours of
diagnosis,
1
whereas angiography is indicated within 24 hours
after presenting with a NSTEMI.
4
Pain management and appropriate antiplatelet therapy form
part of the mainstay of therapy in both STEMI and NSTEMI.
1,4
PE, however, requires anticoagulation. Systemic thrombolytic
therapy is recommended for PE with haemodynamic instability.
In centres with the necessary skill, percutaneous catheter-directed
therapy or surgical embolectomy could be considered in high-risk
PE when thrombolysis has failed or is contra-indicated.
2
References
1.
Ibanez B, James S, Agewall S, Antunes MJ, Bucciarelli-Ducci C, Bueno
H,
et al
. 2017 ESC guidelines for the management of acute myocardial
infarction in patients presenting with ST-segment elevation: The task
force for the management of acute myocardial infarction in patients
presenting with ST-segment elevation of the European Society of
Cardiology (ESC).
Eur Heart J
2018;
39
(2): 119–177.
2.
Konstantinides SV, Meyer G, Becattini C, Bueno H, Geersing G-J,
Harjola V-P,
et al
. 2019 ESC guidelines for the diagnosis and manage-
ment of acute pulmonary embolism developed in collaboration with
the European Respiratory Society (ERS).
Eur Heart J
2020;
41
(4):
543,3–603.
3.
Klabunde RE. Cardiac electrophysiology: normal and ischemic ionic
currents and the ECG.
Adv Physiol Ed
2017;
41
(1): 29–37.
4.
Collet JP, Thiele H, Barbato E, Barthelemy O, Bauersachs J, Bhatt
DL,
et al
. 2020 ESC guidelines for the management of acute coronary
syndromes in patients presenting without persistent ST-segment eleva-
tion. E
ur Heart J
2020: ehaa575.
5.
Rautaharju PM, Surawicz B, Gettes LS, Bailey JJ, Childers R, Deal
BJ,
et al.
AHA/ACCF/HRS recommendations for the standardization
and interpretation of the electrocardiogram: part IV: the ST segment,
T and U waves, and the QT interval: a scientific statement from the
American Heart Association Electrocardiography and Arrhythmias
Committee, Council on Clinical Cardiology; the American College of
Cardiology Foundation; and the Heart Rhythm Society: endorsed by the
International Society for Computerized Electrocardiology.
Circulation
2009;
119
(10): e241–250.
6.
Van Gorselen EO, Verheugt FW, Meursing BT, Oude Ophuis AJ.
Posterior myocardial infarction: the dark side of the moon.
Neth Heart
J
2007;
15
(1): 16–21.
7.
Thygesen K, Alpert JS, Jaffe AS, Chaitman BR, Bax JJ, Morrow DA,
et al
. Fourth universal definition of myocardial infarction (2018).
Eur
Heart J
2019;
40
(3): 237–269.
8.
Shopp JD, Stewart LK, Emmett TW, Kline JA. Findings From 12-lead
electrocardiography that predict circulatory shock from pulmonary
embolism: systematic review and meta-analysis.
Acad Emerg Med
2015;
22
(10): 1127–1137.
9.
Ciliberti P, Rapezzi C, Villani C, Boriani G. Massive pulmonary embo-
lism with acute coronary syndrome-like electrocardiogram mimicking
acute left main coronary artery obstruction.
J Emerg Med
2012;
43
(4):
e255–258.
10. Kucher N, Goldhaber SZ. Cardiac biomarkers for risk stratification of
patients with acute pulmonary embolism.
Circulation
2003;
108
(18):
2191–2194.
V1
V2
V3
V4
V5
V6
Fig. 6.
Acute pulmonary embolism causing right ventricular
strain, which translates to ST-segment depression in
the anterior leads.