Imaging of Heart failure

Objectives

• To describe the role of imaging in  heart failure

• To identify and correlate radiological signs with the stages of pulmonary venous hypertension

• To describe the Chest radiographic signs of left heart failure

• To identify the mimics of left heart failure on CXR

 Role of imaging in Heart failure

•  Imaging is a supplement or a confirmatory test for the clinical diagnosis, as the symptoms are non   specific.

•  Imaging quantifies heart failure, by identifying the degree / stage

•  It  assess the response to treatment

•  It is useful to assess the aetiology 

Imaging methods

• Plain radiography ( CXR) – most commonly done examination, detects all the stages of left heart failure, even before the clinical signs are overt

• ECHO – is important in detecting the aetiology, type of failure

• US -   not routinely done,may detect CCF, as an incidental finding on US in a patient with abdominal discomfort or RHC pain the changes of right heart failure on US such as IVC and  hepatic venous congestion, liver enlargement and ascites

• CT scan not routinely done for heart failure, but may be found incidentally, when performed for non specific dyspnoea

Stages of Pulmonary Venous congestion or Hypertension ( left heart failure)
1. Pulmonary venous congestion         > 20 mm Hg
2. Interstitial oedema                           > 20 mm Hg 
3. Alveolar oedema                   > 25 mm Hg

Radiological signs of heart failure on CXR 

Radiological signs depend on the stage and severity, and they are as follows
1.    Cardiomegaly
2.    Upper lobe venous congestion
3.    Interstitial shadows
4.    Alveolar shadows
5.    Pleural effusion,  usually small to moderate and B / L ,  if unilateral predilection for right.

Stage 1 - Upper lobe venous congestion-Usually the upper lobe veins are not visible on CXR. Even if they are seen, they are confined to one intercostals space above the hilum. If the upper lobe veins are visible above two intercostals spaces it is called upper lobe venous congestion. Redistribution of pulmonary venous blood ( fig 1a, b).

 Fig 1a - normal CXR

Fig 1b - upper lobe venous congestion

Stage 2 - Interstitial pulmonary oedema - Linear  interstitial shadows, radiating from the hilum or mostly in  mid and  lower zones. Kerley B lines are well recognized, fascinating linear shadows of interstitial oedema. They are horizontal, perpendicular to the pleura and only about 3-6mm long and 1-2 mm thick. They are interlobular septae thickened by transudate. There are Kerley B and C lines described, latter being curved lines at hilar levels, not very often seen as Kerley’s B lines. Other sign that may seen in this stage is perivascular oedema which leads to blurring of vascular margings, which is predominantly seen in right lowere lobe as the vessels are clearly seen in this region, comaparatively. Peribronchial cuffing may also be seen at this stage in perihilar regions.

Stage 3 - Alveolar oedema - Alveolar oedema is characterized by air space shadowing with homogenous opacification with tendency to confluence , predominantly in mid, perihila and lower zones of lung. Usually symmetrical, ( 3a, b)may be asymmetrical if the patient is kept turned to one  side( 3c). Typical symmetrical alveolar oedemma is called Bat’ s wing appearance described in acute renal failure characteristically. May be seen in acute myocardial infarctionand papillary muscle rupture, even without cardiac enlargement.

 3a - alveolar oedema/ air space shadowing

 3b- Bat’s wing pulmonary oedema

fig 3c -   asymmetrical

Pseudo tumour of heart failure
In some instances pleural fluid gets trapped in horizontal fissure mimicking a mass, with biconvex shape, this is called a pseudotumour( fig 4). This is so called as it disappears after treatment with diuretics, instantly.

Fig 4 - Vanishing tumour

Mimics of heart failure
 Certain pulmonary conditions mimic heart failure, but the pathophysiology and management strategies  are different.

• Adult respiratory distress syndrome

• Interstitial inflammatory diseases    eg- Pneumocystis carinii pneumonia (PCP )    ( fig 5)

Fig 5-  Peri hilar / Mid zonal    interstitial shadowing, Pneumocystis carinii pneumonia