Michael Mück-Weymann

Agreement of two different methods for measurement of heart rate variability

Abstract.Background: The widespread use of affordable devices with sufficient precision for measurement of heart rate variability (HRV) might lead to early detection of abnormalities in a large number of high-risk patients and athletes. The purpose of this study was to determine the limits of agreement of two devices for measuring HRV parameters differing in price and assumed precision. Subjects and methods: 36 healthy subjects (22 men and 14 women) with a mean age of 27.4 (SD 11.1) years were included. The two devices used for comparison were PowerLab® with Chart® software as the reference golden standard, and Polar® Transmitter®/Advantage® with Precision Performance® software, respectively. Measurements included the following heart rate variability parameters: heart rate, range of R-R-interval duration, SDNN, rMSSD, total Power, VLF power, LF power, and HF power. Measurements were taken during metronomic respiration over a total period of 3 minutes. Statistical analysis was performed according to Bland and Altman and by means of scatterplots and Spearman correlation coefficients. Results: Good agreement was found for heart rate (95 % CI of limits of agreement: −0.7–0.6 bpm; r = 0.999), range of duration of R-R-intervals (95 % CI: −18.9–17.0 ms; r = 0.997), rMSSD (95 % CI: −1.5–2.5 ms; r = 0.999), and SDNN (95 % CI: −3.0–3.1 ms; r = 0.997). Correlation of measurements was high for the variables total Power, VLF power, LF power, and HF power. Analysis of method agreement for frequency domain variables was statistically not feasible. Conclusion: The level of agreement for the analyzed time domain variables between the reference golden standard and the inexpensive device is sufficient to permit initial screening by family doctors, and self-administration by high-risk patients and athletes.

TRANSCRANIAL DOPPLER SONOGRAPHY DURING ACUTE 80 DEGREES HEAD-DOWN TILT (HDT) FOR THE ASSESSMENT OF CEREBRAL AUTOREGULATION IN HUMANS

Cerebrovascular hemodynamics during postural changes have been sparsely Investigated despite the fact that abnormal responses may contribute to the risk of stroke. The aim of this study was to determine the effect of acute 80° head-down tilt (HDT) on cerebrovascular hemodynamics in humans using transcranial Doppler sonography (TCD). In 13 healthy volunteers (2 female, 7 1 male, age 19-37 years, mean age 26.8 years) left midcerebral artery blood flow velocities (CBFVs) were continuously monitored using TCD during 180 sec in horizontal position and during 60 sec of 80° HDT. Simultaneously, systolic, diastolic, mean CBFVs, pulsatility index (PI), heart rate, beat-to-beat blood pressure (BP) and transcutaneous pC02 were measured. In five volunteers, the procedure was repeated the next day to test the repeatability of the results. Mean BP increased slightly, but not significantly during tilt (from 80.5± 7.7 mmHg to 85.9 ±14.1 mmHg; p < 0.05). Heart rate decreased significantly during the first 20sec of HDT (from 66.8± 9.9 min-1 to 60± 11 min-1; p> 0.05). Transcutaneous pC02 was within physiological ranges during the whole procedure (mean pC02 minimum 39.5±2.9 mmHg, mean pC02 maximum 42.2±3.3 mmHg). Mean CBFV did not change significantly during tilt (from 70.1 ± 7 9.1 cm sec-1 to 66.6 ± 14.1 cm sec-1; p < 0.05). PI, however, increased significantly with a more pronounced increase during the first 20 sec than the last 40sec of tilt (Plsupine 0.92±0.11; Pltnt(0-20sec) 1.15±0.18; Pltnt(2i~6o sec) 1-03±0.16; p = 0.001; p = 0.017). The HDT results were found to be reproducible in the five volunteers. During 80°-HDT mean BP and pC02 did not change significantly. This observation combined with the significant decrease in heart rate during the first 20 sec of HDT, suggests that there is no sympathetic activation. The significant PI increase during HDT indicates a vasoconstriction of the cerebral resistance vessels. We assume that this vasoconstriction is due to the myogenic mechanism of cerebrovascular autoregulation triggered by a rapid, passive intracranial blood volume influx during HDT. [Neurol Res 1999; 21: 457-462].

Ist die autonome kardiale Regulation bei Patienten mit Depression und Koronarer Herzkrankheit gestört

Zusammenfassung. Hintergrund und Zielsetzung: Beeintrachtigung der Herzratenvariabilitat ist ein Indikator fur eine erhohte kardiovaskulare Mortalitat. Gepruft werden sollte, ob depressive Symptome die Herzratenvariabilitat beeinflussen konnen. Methode: Die Herzratenvariabilitat wurde bei 22 ambulanten nicht behandelten Patienten (16 w, 6 m) und bei 11 gesunden Kontrollpersonen (8 w, 3 m) gemessen. Daruber hinaus wurden 41 Patienten mit koronarangiographisch gesicherter KHK (5 w, 36 m) untersucht. Ergebnisse: Die Herzratenvariabilitat war bei herzgesunden Patienten mit Depression um 50% vermindert im Vergleich zu Kontrollpersonen (p < 0,05) wahrend das Vorhandensein depressiver Symptome bei Patienten mit KHK keinen signifikanten Einfluss auf die Herzratenvariabilitat hatte. Schlussfolgerungen: Storung der autonomen kardialen Regulation konnte fur herzgesunde Patienten mit Depression nachgewiesen werden.

Inspirationsgetriggerte vasokonstriktorische Episoden bei Gesunden, bei Patienten mit Diabetes mellitus sowie bei Patienten mit klinisch manifester Polyneuropathie unterschiedlicher Genese

BACKGROUND A cost- and time efficient ultrasound-Doppler-test is introduced to evaluate the function of autonomic innervation of the upper limb. A voluntary inspiratory vasoconstrictor episode (VICE) after a provoked deep inspiration, transmitted via sympathetic nervous system, can be demonstrated at the radial artery using basic Doppler equipment. PATIENTS AND METHOD VICEs were investigated in 30 healthy subjects (group A), in 20 patients with diabetes mellitus without clinical signs of polyneuropathy (group B) and in 20 patients with clinically manifest polyneuropathy (group C). RESULTS In all healthy subjects a two minutes arterial occlusion led to a decrease of resistance index (RI) lower than 0.9 indicating sufficient hyperemia. RI during VICE increased to 1.0 in all healthy subjects. In 50% of the patients of group B as well as in 50% of the patients of group C the test revealed abnormal findings suggesting a disorder of the functional peripheral neurovascular unity.Zusammenfassung□ HintergrundVorgestellt wird ein kostengünstig und zeitsparend durchführbarer Ultraschall-Doppler-Test zur Untersuchung der autonom-vaskulären Funktionseinheit an den Akren zur frühzeitigen Diagnosefindung bei potentiell „Polyneuropathie-gefährdeten” Patienten. Nach tiefer Inspiration kommt es zu einer reflexartigen akralen Vasokonstriktion, die über sympathische Nervenfasern vermittelt wird und mittels eines einfachen Ultraschall-Dopplers zum Beispiel an der Arteria radialis nachweisbar ist.□ Patienten und MethodeUntersucht wurde die inspirationsgetriggerte vasokonstriktorische Episode an 30 Kontrollpersonen, bei 20 Patienten mit Diabetes mellitus Typ II ohne klinisch manifeste Polyneuropathie und bei 20 Patienten mit klinisch manifester Polyneuropathie.□ ErgebnisseBei allen Kontrollpersonen kam es nach einer durch zweiminütige Okklusion provozierten Hyperämie zu einer Senkung des Widerstandsindexes RI auf Werte unter 0,9. Nach tiefer Inspiration stieg der RI-Wert bei allen Kontrollpersonen auf 1,0. Hingegen wiesen 50% der Patienten aus Kollektiv B sowie 50% der Patienten aus Kollektiv C eine vom Kontrollkollektiv abweichende Vasokonstriktionstreaktion auf.□ SchlußfolgerungDer hier vorgestellte Ultraschall-Doppler-Test zur Überprüfung der funktionellen Einheit sympathischer Innervation und kleiner Gefäße könnte eine einfache und kostengünstige Ergänzung des diagnostischen Repertoires zum Beispiel beim diabetischen Patienten werden.Summary□ BackgroundA cost- and time efficient ultrasound-Doppler-test is introduced to evaluate the function of autonomic innervation of the upper limb. A voluntary inspiratory vasoconstrictor episode (VICE) after a provoked deep inspiration, transmitted via sympathetic nervous system, can be demonstrated at the radial artery using basic Doppler equipment.□ Patients and MethodVICEs were investigated in 30 healthy subjects (group A), in 20 patients with diabetes mellitus without clinical signs of polyneuropathy (group B) and in 20 patients with clinically manifest polyneuropathy (group C).□ ResultsIn all healthy subjects a two minutes arterial occlusion led to a decrease of resistance index (RI) lower than 0.9 indicating sufficient hyperemia. RI during VICE increased to 1.0 in all healthy subjects. In 50% of the patients of group B as well as in 50% of the patients of group C the test revealed abnormal findings suggesting a disorder of the functional peripheral neurovascular unity.□ ConclusionThe test may get a new and helpful diagnostic tool in the management of patients with suspected or clinically manifest polyneuropathy.