Does catheter position and respiration affect coronary sinus blood flow measurements by thermodilution?
Coronary sinus blood flow measurements by thermodilution are highly sensitive to catheter position and respiratory phase, making inter-patient comparisons unreliable unless position is strictly controlled.
By measuring the coronary sinus blood flow using the thermodilution technique the influence of "thermodilution catheter" withdrawal from the great cardiac vein to the ostium of the coronary sinus was investigated in 41 patients. In addition, the influence of normal and forced respiration on coronary sinus blood flow was measured in 16 of the patients. Mean great cardiac vein flow was measured to 54 +/- 25 ml X min-1. Catheter withdrawal revealed coronary sinus blood flows of 80 +/- 32, 103 +/- 35, 145 +/- 39 and 213 +/- 61 ml X min-1 when the catheter was moved by steps of 1 cm towards the coronary sinus ostium. The coronary sinus blood flow changed between 116 +/- 34 ml X min-1 and 128 +/- 41 ml X min-1 on expiration or inspiration during normal respiration, respectively, when the catheter was placed in a mid-coronary sinus position. Forced respiration changed the coronary sinus blood flow from 98 +/- 41 ml X min-1 during expiration to 196 +/- 76 ml X min-1 during inspiration. The data show that coronary sinus blood flow changes from 23 to 68 ml X min-1 per cm catheter movement, the nearer the ostium the greater the change. Therefore comparison of coronary sinus blood flow between groups of patients would be a comparison between different catheter positions. Normal respiration moves, as judged by the coronary sinus blood flow, the thermodilution catheter by less than 0.5 cm while forced respiration moves the catheter up to 2 cm within the coronary sinus.
J. P. Bagger (Tue,) studied this question.