Autonomic Function Testing (Clinical)

(Ewing  DJ,  1985, 1988)  

05 November 2004

1.      SCREENING

i)                    BP response to standing.

Difference in systolic blood pressures between lying and after standing for 1 minute (time this).

Normal : - <10 mmHg.  Borderline : - 11-20 mmHg.  Abnormal : >30 mmHg.

ii)                  BP response to sustained handgrip.

Take resting systolic pressure.  Maintain handgrip in other arm at 30% of maximum voluntary pressure (use dynanometer) for up to 5 minutes; record systolic pressure each minute.  Stop if rise reaches normal level.  If not, record rise to just before handgrip release at 5 minutes.

Normal : - >16 mmHg.  Borderline : - 11-15 mmHg.  Abnormal : <10 mmHg.

iii)                HR response to standing.

Attach ECG limb leads.  With strip recorder running (II), patient stands from lying as quickly as possible.  Measure 30:15 ration : - ratio of longest R-R interval around 30^th b eat after standing to shortest R-R interval about 15 beats after standing.

Normal : - >1.04. Borderline : - 1.01-1.04.  Abnormal : <1.00.

iv)                HR response to deep breathing.

With patient sitting and strip ECG recording, patient breathes deeply and evenly at 6 breaths per minutes (5 seconds in; 5 seconds out) for 3 cycles (30 seconds).  Count “IN-2-3-4-5-OUT-2-3-4-5-as they do.  Measure greatest heart rate difference during each cycle and average the 3 differences.

Normal : - >15 beats / min.   Borderline : - 11-14 beats / min.

Abnormal :<10 beats / min.

v)                  HR response to Valsalva.

Pierce the cardboard tube in the middle first with a wide-bore needle to ensure a slow air leak.  With patient sitting and strip ECG recording, patient breathes into disposable cardboard mouthpiece attached to aneroid (not mercury) sphygmomanometer to keep pressure at 40 mmHg for 15 seconds.  Record for 30 seconds more after this.  Take ratio of longest R-R interval within 20 beats of ending manouvre to shortest interval during manouvre.  Repeat twice more, and average the ratio from the 3 Valsalva attempts.

Normal : - >1.21.  Abnormal : <1.20.

RESULTS

Normal                   : -          All tests normal, or 1 borderline result.

Mildly Abnormal           : -          One of the 3 HR tests abnormal, or 2 borderline.

Definitely abnormal : -          Two or more of the HR tests abnormal.

Severely abnormal           : -          Two or more of the HR tests abnormal, plus one

or both of the BP tests abnormal, or both borderline.

If result abnormal, then for further investigations.

2.      FURTHER TESTING

i)                    Pupil diameter in darkness.

Request to Medical Illustration for Polaroid shot of one eye (doesn’t matter which) in darkness with electronic flash, preferably taken at about x3 magnification.  Measure pupil diameter as percentage of iris diameter.

ii)                  Pupil cycle time.

Using a slit lamp, focus a narrow beam of light at the pupil margin.  The constricting pupil should interrupt the light beam, causing redilation.  Time 100 cycles, and calculate the mean. (An assistant with a sweep hand watch may be useful).

Mean : - 940 msec.  Mean + 2 s.d. : - 1160 msec.

iii)                Galvanic skin response.

Request to Clinical Neurophysiology  (although could be done with ECG, using LA lead connected to palm and RA to upper arm on same side, and recording “I”.  Patient would be warned to expect a painful pinch on the other arm, which would be given at a random time without the patient looking while the ECG was recording.  A similar arrangement should be applied to the sole of the foot, with the effective reference electrode higher up the same leg.  The stimulus could be applied in the same way, to an arm.) 

Failure to elicit a response (usually about 1 second after stimulus for palm recording) is abnormal.

SPECIAL TESTS  

i)  Cystometrogram.

ii)  IV tyramine and/or noradrenaline pressor responsiveness.

iii) Serum nordrenaline levels