Discussion:
Coronary embolism occurs in about 3% of patients with acute coronary
syndrome. However, it is a rare occurrence in a patient without a
cardiac history of endocarditis, arrhythmia or family history. Coronary
embolism is of three main types: direct, paradoxical and iatrogenic
Direct embolism usually results from a thrombus originating in the left
ventricle, left atrium, or due to endocarditis involving the mitral or
aortic valve. Paradoxical embolism occurs from the venous circulation
through a patent foramen ovale. Iatrogenic embolism occurs after a
cardiac procedure. [1]
Risk Factors include evidence of blood stasis (i.e left ventricular
aneurysm, atrial fibrillation, deep vein thrombosis with ASD or PFO),
Hypercoagulable state (i.e cancer, thrombophilia, oral contraceptive
use, heparin induced thrombocytopenia), endothelial injury (i.e
angioplasty, valvuloplasty, aortic/coronary surgery), and anatomic
predisposition (i.e ASD/PFO, endocarditis, mitral stenosis)
Diagnosis of coronary embolism can be made using a scoring system
proposed by Shibata et al. [3] Major criteria includes 1)
Angiographic evidence of coronary embolus 2) Concomitant systemic
embolization without evidence of left ventricular thrombus 3)
Concomitant coronary emboli in multiple coronary territories 4) Evidence
of an embolic source based on imaging. 5) Histological evidence of
venous origin of coronary embolic material
Minor criteria include 1) <25% stenosis on angiography in the
non-culprit vessels 2) Presence of Atrial fibrillation 3) Presence of
embolic risk factors
Patients with 2 or more major criteria, 1 major and 2 minor, or 3 minor
criteria were considered to have a definite coronary embolus. Patients
with 1 major and 1 minor or 2 minor criteria were considered to have a
probable coronary embolus. [1,3]
Our patient is a young female with tobacco abuse, on norgestimate
/ethinyl estradiol pills for dysfunctional uterine bleed who presented
with an inferior STEMI secondary to a clot (thrombus) involving the
distal left main artery, left circumflex, proximal and distal LAD.
ECG changes were mainly seen in the inferior rather than anterior or
antero-lateral leads. That can be explained by two theories. 1) There
might have been a right coronary artery clot that was dislodged prior to
the angiogram especially that the repeat ECG showed resolution of
inferior ST elevations. 2) Complete occlusion of the distal LAD artery
(which is a wrap-around artery), with evidence of continued flow in the
left main and proximal LAD artery.
She did not have history of atrial fibrillation, no evidence of clot,
valvular heart disease, wall motion abnormality or an intra-atrial shunt
with rest and provocation on TTE, and no evidence of DVT. The primary
hypothesis is that she had a direct arterial thromboembolism that
developed secondary to the combination of oral contraception and smoking
which is a rare entity, since most thromboembolisms due to acquired
thrombophilia are rather venous. Although patient was monitored on
telemetry over 48 hours without cardiac arrhythmias, she was recommended
to have a long-term cardiac monitoring (by an event monitor) to rule out
paroxysmal atrial fibrillation as a possible cause of this
thromboembolism which was negative on further outpatient visits.
Transesophageal echocardiogram was also recommended to be done in the
outpatient setting to further assess the presence of a clot in the left
atrial appendage.
Although thrombophilia workup is seldom indicated at part of coronary
embolism workup [1], it was performed during her admission and was
negative. Long - term cohort studies revealed increased risk of venous
rather than arterial thromboembolism in patients with inherited
thrombophilia’s [8].
Antiplatelet therapy was continued in our case due to presence of a
distal LAD (apical) occlusion which is most likely due to the presence
of a clot (thrombus) but we were unable to completely rule out the
presence of atherosclerotic disease in that area.
Although estrogen and progesterone therapy may be an effective method of
dysfunctional uterine bleeding, it is an oral contraceptive which is
known to create a hypercoagulable state in combination with smoking and
thereby increase the risk for a thromboembolic event [4, 5, 6].
Valdeti et al performed a literature review on a total of 214 cases of
coronary thromboembolism with the etiology being atrial fibrillation
(26%), endocarditis (24%), iatrogenic emboli (21%), prosthetic valve
thrombi (12%), hypercoagulable state with PFO (6%), aortic atheroma
(5%), myxoma (2%), fat emboli (2%), and coronary stent emboli (2%)
[7]
Treatment of coronary embolism depends on the root cause. Patients with
atrial fibrillation or recurrent coronary embolism should be offered
long term anticoagulation regardless of their CHADS2-VASc score.
Patients with a reversible risk factor such smoking or OCP use should
receive oral anticoagulation for 3 months [1]
After review of literature, we believe that this is the first case
report to describe a case of a STEMI due to coronary embolism in a
patient who is taking OCP’s without evidence of a DVT or a patent
foramen ovale.