Discussion
Cardiovascular events have been reported as side effects of the COVID-19
vaccine; however, it is still unclear how vaccination can be associated
with acute coronary syndrome (ACS) [2,3,4], coronary embolism due to
severe inflammation induced by the vaccine, or coronary thrombosis
mainly caused by plaque rupture.
Coronary embolism is a rare disease and is difficult to distinguish from
coronary thrombosis. It has been reported to be caused occasionally in
patients with arrhythmia and valvular disease [5]. Moreover,
inflammatory hypercoagulation is known as a mechanism of coronary
embolism [6]. It is often diagnosed by relating these conditions to
embolism and by features such as fewer atherosclerosis lesions on
specific angiographic images [6]. The typical thrombus is found to
be platelet and fibrin rich on pathological examination [6].
This patient had an atypical clinical history, leading to myocardial
infarction shortly after vaccination. Therefore, we considered that the
onset was related to the vaccine. It was difficult to find the culprit
lesion even using IVUS and OCT. However, we suspected myocardial
infarction caused by plaque rupture, rather than by emboli, from the
results of the pathological examination of the collected thrombus, which
contained atheroma rich in cholesterin crystals and foam cells.
The vasa vasorum are small vessels that provide blood to the walls of
arteries and veins. It is known that atherosclerosis facilitates the
growth of vulnerable plaques and promotes neovascularisation of the vasa
vasorum, which predisposes plaques to rupture [7]. Treatment with a
low dose of statin has a little effect on the vasa vasorum, and a high
dose is often needed [8]. Other medications for this condition are
not known to date.
Through OCT, we discovered a rare large vasa vasorum in a thick plaque,
indicating that it was unstable. These findings support the theory that
plaque rupture led to the patient’s ACS. Therefore, angioplasty was
performed, and high-dose statins were administered for these lesions.
Only three cases of acute myocardial infarction have been reported to
occur within 2 hours after COVID-19 vaccination [2,3,4]. Patients in
all three cases had RCA lesions; this finding was similar to that in the
present case report. Kounis syndrome has been reported to occur after
the vaccination [9]. Around 70% of patients with Kounis syndrome
show ST elevation in inferior leads on electrocardiography [10]; the
reason for high probability of RCA lesion still has been unknown. It
might also support the fact that acute myocardial infarct immediately
after vaccination is caused by allergic factors like Kounis syndrome.
The patient in the present case was at a high risk of ACS. We suspected
that stress or an allergic reaction caused by the vaccination might have
led to elevated blood pressure and vasoconstriction, which affected the
vulnerable plaque and caused plaque rupture.