Discussion:
Left Atrium (LA) is a low pressure , thin wall chamber located
inferoposteriorly and highly vulnerable and liable to compression by
dorsal mediastinal structure (1). The postero lateral approach of
pulmonic veins are also susceptible to be compressed by same structures.
The subdivision proposed by D’Cruz et al (1 ) is as follows
- Proximity – a contiguous or adjacent structure without chamber
deformation.
- Encroachment – distortion of normal cardio vascular architecture
without haemodynamic effect.
- Compression –where impression is responsible for development of
haemodynamic instability and symptoms(2).
The above mentioned impressions is clearly seen on TTE as deformed and
smaller LA which leads to low output state and causes symptoms like
dyspnoea, reduced exercise tolerance , easy fatigue ability and even
hemodynamic instability. Depending on the severity or degree of
compression , LA pressure may rises to a level leading to pulmonary
oedema mimicking heart failure or cardiac temponade (2).
TTE can easily visualise distorted shape of LA by conventional and
unconventional views except (i) extreme obesity (ii)poor echo window
(iii) previous cardio thoracic surgery (iv) patient on mechanical
ventilation etc.
With the aid of color Doppler ,we can pick up turbulent flow due to
compressed LA and pulmonic veins. Similarly by additional use of
agitated saline contrast echo and ingestion of aerated drinks orally ,
the vascular and non vascular causes of LA impression can be ruled out
(3).
However , Right heart catheterisation , Computed tomography , Cardiac
MRI techniques may be finally conclusive , to aid into further
management .
As reported before on the basis of its origin , the compression can be
classified (4-7):
A: Gastrointestinal (GI) tract structures
B: Mediastinal structure
C: Aorta / Intrapericardial structure
D:Pulmonary structure
But the compression by dorsum spine is not reported in the literature .
We , hereby report one such case of LA compression/ impression with
dorsal spine , although we have seen two of them.