DISCUSSION
Although primary tumor of the heart is rare with the reported prevalence
of 0.1%-0.01, metastatic cardiac tumor is more frequent than primary
tumors with the range of 0.7%-3.5% in autopsy
series.1 The prevalence of cardiac metastasis is
reported up to 9.1% in oncology patients. The leading malignancies that
metastasize to heart are lung, breast and hematologic malignancies with
the rates of 36-39%, 10-12% and 10-21%,
respectively.1 Prostate cancer is the most common
malignancy in men, but nevertheless hardly metastasize to heart due to
its low aggressiveness.2
The common mechanism of lung cancer to metastasize to the heart is by
means of direct extension to epicardium or
pericardium.2 Other possible pathways for various
malignancies are lymphatic (most common) and hematogenous spread. Renal
cell carcinoma is the leading cause for transvenous (caval) extension.
Yet, lung cancer tends to use pulmonary veins to reach left
atrium.3 Myocardial metastasis is rare and endocardial
or intracavitary metastases are even rarer. The right chambers are
affected mostly up to 80% and right atrium is the common site for
metastases.4
Due to most cardiac metastases are indolent and course without cardiac
specific symptoms, the diagnose often delay untill the advanced stages
of the disease even at autopsy if not detected incidentally by
imaging.1 If any symptom occurs, location and size of
the tumor or invasion to surrounding organs may determine the clinical
scenario. The involved chambers or valves may be obstructed, coronary
flow may be altered due to mass effect, contraction abnormalities or
arrhythmic interferences may occur5. Direct invasion
of the tumor can result malignant pericardial effusion.
Echocardiography is the first line imaging modality to detect any
obvious masses in any chambers, valves or apparent myocardial
thickening.5,6 Transesophageal echocardiography (TEE)
is superior than any other imaging modalities to reveal valvular mass
lesions and its hemodynamical consequences.5 Computed
tomography (CT) and cardiac magnetic resonance (CMR) are useful tools to
detect, localize and characterize the mass. CMR has the unique feature
to reveal tissue characteristics which is of utmost importance in case
of any myocardial mass.6 Contrast administration may
aid in differentiating between thrombus and tumor.6
In conclusion, though cardiac metastases in lung cancer patients are
expressed at the late stages of the disease, it is vital to detect any
metastasis to adequately manage the patients as survival rate prolongs
with the aid of novel therapies. Patients with known malignancy
necessitates clinicians, echographers or imagers being more vigilant in
case of unexpected myocardial thickening as it might resemble
hypertrophic cardiomyopathy phenotype.