Copyright ©The Author(s) 2015.
World J Diabetes. Feb 15, 2015; 6(1): 80-91
Published online Feb 15, 2015. doi: 10.4239/wjd.v6.i1.80
Table 1 Cardiovascular autonomic reflex tests[1]
TestTechniqueNormal response and values
Beat-to-beat HRVWith the patient at rest and supine, heart rate is monitored by ECG while the patient breathes in and out at 6 breaths per minute, paced by a metronome or similar deviceA difference in heart rate of > 15 beats per minute is normal and < 10 beats per minute is abnormal. The lowest normal value for the expiration-to inspiration ratio of the R-R interval decreases with age: age 20-24 yr, 1.17; 25-29, 1.15; 30-34, 1.13; 35-39, 1.12; 40-44, 1.10; 45-49, 1.08; 50-54, 1.07; 55-59, 1.06; 60-64, 1.04; 65-69, 1.03; and 70-75, 1.02
Heart rate response to standingDuring continuous ECG monitoring, the R-R interval is measured at beats 15 and 30 after standingNormally, a tachycardia is followed by reflex bradycardia. The 30:15 ratio should be > 1.03
Heart rate response to the Valsalva maneuverThe subject forcibly exhales into the mouthpiece of a manometer to 40 mmHg for 15 s during ECG monitoringHealthy subjects develop tachycardia and peripheral vasoconstriction during strain and an overshoot bradycardia and rise in blood pressure with release. The normal ratio of longest R-R to shortest R-R is > 1.2
Systolic blood pressure response to standingSystolic blood pressure is measured in the supine subject. The patient stands and the systolic blood pressure is measured after 2 minNormal response is a fall of < 10 mmHg, borderline fall is a fall of 10-29 mmHg and abnormal fall is a decrease of > 30 mmHg with symptoms
Diastolic blood pressure response to isometric exerciseThe subject squeezes a handgrip dynamometer to establish a maximum. Grip is then squeezed at 30% maximum for 5 minThe normal response for diastolic blood pressure is a rise of > 16 mmHg in the other arm