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Posts Tagged ‘ct ratio during systole and diastole’

Have you ever wondered a given chest x-ray is taken in systole or diastole ?  We should . . .  isn’t ?  Statistically chances of a  X ray to  fall in  diastole is 10-20 % more than systole as the later phase is longer . The peculiarity of cardiac anatomy is that ,  the  profile of the heart alters so little between systole and diastole  .Still the blood is pumped  efficiently into both pulmonary and systemic circulation . The left ventricle shortens by 35%  and ejects 65 % of blood . Similarly RV shortens but with  lesser quantum.

ct ratio in systole and diastole influnce of cardiac cycle on ct ratio

In a simple and elegant study  by Stephen Gammill  in 1970  published in Radiology journal,

he concluded the following about the CT ratio between systole and diastole.

  • 52 %   showed changes of 0.3 cm
  • 41 per cent showed alterations of 0.4 to 0.9 cm,
  • Only  7 per cent  showed a significant  variation of 1.0 to 1.7 cm in transverse cardiac diameter.

(I wonder why any follow up studies on this vital issue is scarce !)

xray chest 002

In spite both ventricles contracting during systole the radiological transverse cardiac diameter is relatively undisturbed ! 

Importance of  Rotary , Twist ,Torsional  and Longitudinal motion

The fact that CT ratio does not alter significantly in most ,  imply the heart has some other  kinetic motion which does not compromise the transverse diameter during systole. They are the rotary , and twist  motion .The relative constancy  of  CT ratio  is a good evidence  for existence for such alternate motions .We have since  confirmed  this  by sophisticated echocardiographic techniques .

Another evidence for rotary motion  recognised in the bed side when the apical impulse hits you in the fingers even as the ventricle is supposed to go away from chest wall during systole . This is  the torsional  movement of  LV  apex  and adjacent inter ventricular septum .

Reference

http://radiology.rsna.org/content/94/1/115.abstract

Coming soon

Inspiratory and expiratory  x ray chest and  the effect on cardiac contours .

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