Cardiomegaly

Cardiomegaly Normal heart AP view

Normal heart lateral view

Cardiomegaly Measurement of cardiac sizeCardiothoracic ratiois measured on a PA chest x-ray, and is the ratio of:maximal horizontal cardiac diametermaximal horizontal thoracic diameter (inner edge of ribs / edge of pleura)A normal measurement should be less than 0.5.

Normal Cardiomegaly If clinical concern exists then echocardiography is required. It will not only be able to assess cardiac function (cardiac size being a surrogate marker of function) but also exclude other causes of enlargement of the cardiac silhouette (e.g.pericardial effusion).

In some situations an increased cardiothoracic ratio on a PA radiograph may simply result from aprominent epicardial fat padand due to expiration rather than from due cardiomegaly.

Cardiomegaly AP view

Modality:X-rayAP and lateral chest x-rays demonstrate markedly enlarged cardiacsilhouette. There is a double contour to the right heart border and splaying of the carina.

Cardiomegaly Lateral viewRed : Splayed carina and double contour. Blue : Most lateral contour is due to the right atriumOrange : more medial contour due to the left atrium

Cardiomegaly CT Scan

Single image from a CT (obtained for unrelated reasons) at the level of the heart confirms cardiomegaly, with dilatation of all chambers (the left atrium most prominent). No pericardial effusion.

Left atrialenlargementAcquiredMitral stenosisMitral regurgitationLeft ventricular failureLeft atrial myxomaCongenitalVentricular septal defect (VSD)Patent ductus arteriosus (PDA)Left atrialenlargement

Right atrial enlargementis less common, and harder to delineate on chest radiograph, thanleft atrial enlargementCausesRaised right ventricular pressurespulmonary arterial hypertensioncor pulmonaleValvular diseasetricuspid regurgitationtricuspid stenosisEbstein's anomalyAtrial septal defect (ASD)Atrial fibrillation (AF)Dilated cardiomyopathy

Right Atrial EnlargementAP view

Lateral viewLEFT VENTRICULAR ENLARGEMENTPressure overload: HTN, ASVolume overload: VSD, AR, MRAneurysmCardiomyopathy

PA CXREnlarges in post, inferior and leftward directionIncreased CTRLarger radius of curvature of left heart borderDownturned cardiac apexDepression of left hemidiaphragm

Left ventricular enlargement

LAT CXRIncreased convexity of posteroinferior cardiac marginHofman rigler rule: posterior cardiac margin projects >1.8 cm post to IVC measured at a point 2cm above intersection of IVC with right hemi diaphragm

RIGHT VENTRICULAR ENLARGEMENTPV stenosisCor pulmonaleASDTricuspid regurgitationSecondary to LVF

PA CXROnly extreme dilatation causes signs on frontal viewStraightening/ convexity of left upper cardiac contourUpturned cardiac apexLeft upper cardiac margin parallels left main stem bronchus as a long convex curvatureLarge appearance of main pulmonary arteryOccurs higher on the left heart border b/w left ventricular contour and pulmonary outflow tract

LAT CXRProminent convexity of ant heart border >1/3 distance from anterior cardiophrenic sulcus to sternal angleIncreased size prominent in retrosternal area

Reference:Radiopaedia.org

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