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Heart rate variability: Response to graded head up tilt in healthy men. 2009

Pramod Sharma, and B H Paudel, and P N Singh, and P Limbu
Department of Physiology, Kathmandu Medical College, Kathmandu, Nepal. aamodsharma@yahoo.com

BACKGROUND Heart rate variability is actually a misnomer for R to R variability in cardiac cycle. Variation in successive cycle length is called the heart rate variability (HRV). Head-up tilt is a model of studying cardiovascular haemodynamics, which reflects in heart rate variability (HRV). OBJECTIVE To study the effect of 10 degrees and 70 degrees head-up tilt on HRV. METHODS The study was done in the Department of Physiology using graded head up tilt (passive orthostatism). HRV measurement was done at 10 degrees and 70 degrees tilt and compared with supine using standardised methods on 30 consenting healthy males (age 25.37+/-3.89 years). The HRV variables across postures were compared by ANOVA and Bonferroni test. RESULTS The heart rate increased at 70 degrees compared to 10 degrees and supine (70.48+/-8.17 Vs 70.22+/-8.67 and 88.51+/-12.84 bpm, p<0.001). The 70 degrees tilt decreased vagal HRV indicators compared to 10 degrees and supine: SDNN (31.13+/-8.12 Vs 38.07+/-11.29 and 38.13+/-10.89 ms, p<0.05), RMSSD (20.06 +/-8.47 Vs 34.23+/-14.22 and 36.16+/-12.22 ms, p<0.001), NN50 count (13.03+/-20.58 Vs 45.07+/-44.44 and 55.27+/-44.10, p<0.01), pNN50 (3.28+/-6.08 Vs 14.06+/-15.65 and 16.65+/-14.23, p<0.01), HF power (197.20+/-143.76 Vs 218.17+/-155.85 and 216.87+/-150.98 Hz, p<0.05), HFnu unit (24.28+/-14.16 Vs 45.48+/-16.34 and 47.67+/-19.89, p<0.001). The 70 degrees tilt increased LF power% (197.20+/-143.76 Vs 218.17+/-155.85 and 216.87+/-150.98, p<0.001). LFnu unit (75.72+/-14.76 Vs 54.52+/-16.34 and 52.32+/-19.89, p<0.001), LF: HF (4.96+/-4.08 Vs 1.53+/-1.138 and 1.69+/-1.67, p<0.001) compared to 10 degrees and supine. CONCLUSIONS At 70 degrees tilt, HRV measures, reflecting vagal contribution to cardiac-cycle length, decreased with reciprocal increase in sympathetic activity compared to 10 degrees or supine leading to increase in sympathetic predominance. A 10 degrees tilt, which is almost equivalent to lying down with pillow, did not change HRV from supine. activity.

UI MeSH Term Description Entries
D008297 Male Males
D011187 Posture The position or physical attitude of the body. Postures
D012016 Reference Values The range or frequency distribution of a measurement in a population (of organisms, organs or things) that has not been selected for the presence of disease or abnormality. Normal Range,Normal Values,Reference Ranges,Normal Ranges,Normal Value,Range, Normal,Range, Reference,Ranges, Normal,Ranges, Reference,Reference Range,Reference Value,Value, Normal,Value, Reference,Values, Normal,Values, Reference
D004562 Electrocardiography Recording of the moment-to-moment electromotive forces of the HEART as projected onto various sites on the body's surface, delineated as a scalar function of time. The recording is monitored by a tracing on slow moving chart paper or by observing it on a cardioscope, which is a CATHODE RAY TUBE DISPLAY. 12-Lead ECG,12-Lead EKG,12-Lead Electrocardiography,Cardiography,ECG,EKG,Electrocardiogram,Electrocardiograph,12 Lead ECG,12 Lead EKG,12 Lead Electrocardiography,12-Lead ECGs,12-Lead EKGs,12-Lead Electrocardiographies,Cardiographies,ECG, 12-Lead,EKG, 12-Lead,Electrocardiograms,Electrocardiographies, 12-Lead,Electrocardiographs,Electrocardiography, 12-Lead
D006339 Heart Rate The number of times the HEART VENTRICLES contract per unit of time, usually per minute. Cardiac Rate,Chronotropism, Cardiac,Heart Rate Control,Heartbeat,Pulse Rate,Cardiac Chronotropy,Cardiac Chronotropism,Cardiac Rates,Chronotropy, Cardiac,Control, Heart Rate,Heart Rates,Heartbeats,Pulse Rates,Rate Control, Heart,Rate, Cardiac,Rate, Heart,Rate, Pulse
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000293 Adolescent A person 13 to 18 years of age. Adolescence,Youth,Adolescents,Adolescents, Female,Adolescents, Male,Teenagers,Teens,Adolescent, Female,Adolescent, Male,Female Adolescent,Female Adolescents,Male Adolescent,Male Adolescents,Teen,Teenager,Youths
D000328 Adult A person having attained full growth or maturity. Adults are of 19 through 44 years of age. For a person between 19 and 24 years of age, YOUNG ADULT is available. Adults
D013564 Sympathetic Nervous System The thoracolumbar division of the autonomic nervous system. Sympathetic preganglionic fibers originate in neurons of the intermediolateral column of the spinal cord and project to the paravertebral and prevertebral ganglia, which in turn project to target organs. The sympathetic nervous system mediates the body's response to stressful situations, i.e., the fight or flight reactions. It often acts reciprocally to the parasympathetic system. Nervous System, Sympathetic,Nervous Systems, Sympathetic,Sympathetic Nervous Systems,System, Sympathetic Nervous,Systems, Sympathetic Nervous
D055815 Young Adult A person between 19 and 24 years of age. Adult, Young,Adults, Young,Young Adults

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