Assessment of cardiac contractility during a cold pressor test by using (dP/dt)/P of carotid artery pulses.
The ratio of the first derivative (dP/dt) of a carotid artery pulse to the developed pressure (P), (dP/dt)/P, is an easily measurable, noninvasive index of cardiac contractility even in moderate exercise. We examined the effects of transient cold exposure on cardiac contractility in normal reactors (n = 12) and hyperreactors (an increase in systolic or diastolic pressure >15 mm Hg; n = 6) by using this index. Eighteen healthy participants were subjected to the cold pressor test, which required them to immerse the right hand in chilly water (4 degrees C) for 2 min. Although cold stress maximally increased mean blood pressure during the second minute, it maximally increased heart rate and cardiac contractility after 60 s of immersion in both groups of subjects. Comparing normal reactors and hyperreactors by two-way ANOVA revealed a group x time interaction for heart rate but not for cardiac contractility. These findings suggest that the increase in cardiac contractility during cold-water immersion dose not reflect the levels of heart rate and muscle sympathetic nerve activity, and that the specific responses of cardiac function to a cold pressor test in hyperreactors depends on heart rate rather than cardiac contractility.
Moriyama
Kayo
K
Graduate School of Education, Kumamoto University, Kumamoto 860-8555, Japan.
Ifuku
Hirotoshi
H
D000328:Adult; D001794:Blood Pressure / Q000502:physiology*; D002302:Cardiac Output / Q000502:physiology; D002339:Carotid Arteries / Q000502:physiology*; D003080:Cold Temperature; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D009200:Myocardial Contraction / Q000502:physiology*; D010146:Pain; D011674:Pulse; D012677:Sensation / Q000502:physiology; D013318:Stroke Volume / Q000502:physiology