Topics

Topic

design image
Heart

The heart is a muscular, hollow organ located in the middle mediastinum, resting on the diaphragm and enclosed by the pericardium. It consists of four chambers — the right atrium and ventricle, and the left atrium and ventricle — separated by valves that ensure unidirectional blood flow. The right heart pumps deoxygenated blood into the pulmonary circulation, while the left heart pumps oxygenated blood into the systemic circulation. Structurally, the heart wall is composed of three layers: endocardium (inner lining), myocardium (muscular middle layer), and epicardium (outer layer, part of the pericardium).

Synonyms

  • Cardiac organ

  • Myocardium (in reference to muscular wall)

  • Cor (Latin)

Function

  • Pumps blood through pulmonary circulation (right heart → lungs) and systemic circulation (left heart → body)

  • Maintains oxygen and nutrient delivery to tissues

  • Supports venous return and blood pressure regulation

  • Adapts output via neurohormonal control and intrinsic conduction system (SA node, AV node, His-Purkinje fibers)

Arterial Supply

  • Right coronary artery (RCA): supplies right atrium, right ventricle, inferior left ventricle, posterior interventricular septum (via PDA in right-dominant circulation)

  • Left coronary artery (LCA): divides into:

    • Left anterior descending (LAD): supplies anterior LV, anterior septum, and apex

    • Left circumflex (LCX): supplies lateral LV and LA

  • Coronary dominance (right, left, or co-dominant) depends on which artery gives rise to the posterior descending artery (PDA).

Venous Drainage

  • Coronary sinus: primary venous drainage into the right atrium

  • Great cardiac vein: drains LAD territory

  • Middle cardiac vein: drains PDA territory

  • Small cardiac vein: drains RCA territory

  • Anterior cardiac veins drain directly into the right atrium

Nerve Supply

  • Parasympathetic innervation: via the vagus nerve (CN X) → decreases heart rate and conduction velocity

  • Sympathetic innervation: via the thoracic sympathetic trunk (T1–T5) → increases heart rate, conduction, and contractility

  • Cardiac plexus integrates autonomic fibers, providing motor and sensory innervation

MRI Appearance

T1-weighted images:

  • Myocardium shows intermediate signal intensity

  • Blood in chambers is usually low signal (black) due to flow void

  • Fat surrounding the heart appears hyperintense, aiding contrast

T2-weighted images:

  • Normal myocardium is intermediate to low signal

  • Areas of edema (e.g., myocarditis, infarction) appear hyperintense

  • Pericardial effusion shows high signal fluid surrounding the heart

STIR (Short Tau Inversion Recovery):

  • Suppresses fat, highlighting myocardial edema, inflammation, or acute infarction

  • Normal myocardium remains relatively low signal; pathology appears bright hyperintense

T1 Post-Contrast (Gadolinium-enhanced):

  • Used in Late Gadolinium Enhancement (LGE) imaging

  • Infarcted or fibrotic myocardium appears bright hyperintense, while normal myocardium remains dark

  • Helps distinguish ischemic scar, fibrosis, cardiomyopathy, or myocarditis

CT Appearance

Non-contrast CT:

  • Heart chambers and myocardium appear as soft tissue density

  • Useful for detecting pericardial calcification, coronary artery calcium (CAC scoring), and gross anatomy

Contrast-enhanced CT (Cardiac CTA):

  • Provides detailed visualization of coronary arteries, cardiac chambers, and great vessels

  • Normal myocardium enhances homogeneously; infarcted areas may show delayed hypoenhancement

  • Excellent for assessing coronary stenosis, anomalies, thrombus, pericardial disease, and congenital cardiac defects

MRI images

Heart CT AXIAL image -img-00000-00000

MRI images

Pericardium MRI coronal image -img-00000-00000

X Ray image

x ray Heart