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Table 1 Common variables that affect Doppler patterns.

From: A simplified study of trans-mitral Doppler patterns

Technical factors
   Image quality
   Position of sample volume
Physiological factors
   Heart rate
   Respiration
   Position
   Preload
   Valsalva maneuver
   Age
Pathological causes
   Non-cardiac
Obesity
Deconditioning
Chronic obstructive airways disease
Sleep apnoea
Renal failure
   Cardiac
   See Table 2 and Figure 6
  1. Each of the factors mentioned could confound Doppler interpretation. So these factors should be eliminated or their effects should be factored in. The list is not exhaustive and the non-cardiac causes could also affect cardiac function.