Ewing and Clarke autonomic function tests

Indications

Tests of cardiac parasympathetic and sympathetic damage.

Procedure

Tests of cardiac parasympathetic damage require the following equipment: a sphygmomanometer, a 5 ml syringe and an ECG machine.

1. Heart rate response to the Valsalva manoeuvre.

Start ECG machine (limb leads only, use lead II). Patient blows (hard) into the nozzle end of the 5 ml syringe for 15 seconds, continue recording for 30 seconds after release of pressure.

Measure shortest R-R interval during manoeuvre and longest after. Valsalva ratio equals longest after/shortest during. Take the mean of three readings.

2. Heart rate variation during deep breathing. 

Start ECG machine. Ask patient to breathe quietly at a rate of six breaths over one minute (5 seconds in and 5 seconds out). Mark ECG at start of each inspiration and expiration.

Measure maximum and minimum R-R interval for each cycle and convert to beats/min. Result is the mean difference (max - min) for heart rate during deep breathing.

3. Heart rate response to standing. 

Start ECG recording with patient lying. Ask the patient to stand, continue recording ECG for 1 minute. Measure shortest R-R interval around the 15th beat after standing and the longest around the 30th beat. Calculate longest/shortest ratio i.e. 30th:15th ratio.

Tests of sympathetic damage:

1. Blood pressure response to standing. 

Measure blood pressure lying and then 2 minutes after standing. Record postural difference.

Interpretation   

 

Tests

Normal

Borderline

Abnormal

Valsalva ratio

1.21

1.11-1.20

1.10

(max-min) HR

>15

11-14

<10

(30th:15th ratio)

>1.04

1.01-1.03

1.00

 Fall in BP

 10

 11-29

 30

 

These tests can be used to determine the degree of abnormality present: if two or more of the parasympathetic tests plus the sympathetic tests are clearly abnormal then this indicates significant autonomic damage.

Earlier damage is signified by abnormalities in at least two parasympathetic tests.

Printer Friendly Version

Diabetesbible is for health professionals