Assessment of cardiac contractility during a cold pressor test by using (dP/dt)/P of carotid artery pulses

Abstract

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.

Increased cardiovascular reactivity to the cold pressor test is not associated with increased reactivity to isometric handgrip exercise

“…The cold pressor test increases heart rate, cardiac contractility, and vascular resistance through sympathetic activation depending on the intensity of cold and painful stimuli, factors which increase blood pressure (Mark et al 1985;Fagius et al 1989;Moriyama and Ifuku 2007). Arterial baroreflex is reset at 120 s after immersion to control the heart rate and blood pressure , but not to control peripheral resistance, as shown by the progressive increases in muscle sympathetic nerve activity (MSNA) (Victor et al 1987).…”

Regulation of cardiac function during a cold pressor test in athletes and untrained subjects

“…Two large and long-term prospective studies using survival analysis have reported that blood pressure hyperreactors to the cold pressor test, responding with a rise of 15 mmHg or greater in their systolic and/or diastolic blood pressure, have a higher incidence rate of hypertension than normal reactors (Menkes et al 1989;Kasagi et al 1995). The hyperreactors have specific responses of cardiac function to the cold pressor test, which depends on parasympathetic activity rather than on cardiac contractility (Moriyama and Ifuku 2007). In the present study, seven hyperreactors were identified and treated separately from athletes and untrained subjects of normal reactors.…”

“…Data are mean ± SEM BMI, Body mass index; SBP, systolic blood pressure; DBP, diastolic blood pressure; MBP, mean blood pressure; HR, heart rate at rest in a sitting position * Difference between athletes and untrained subjects at P < 0.05 a Estimated from the Å strand nomogram time heart rate and cardiac contractility maximally increased (Yamamoto et al 1992;Moriyama and Ifuku 2007), and recovered for 3 min. The room temperature was 23.5 ± 0.8°C (mean ± SD).…”

“…The experimental procedures were approved by our institutional committee for the protection of humans in research, and written informed consent was obtained from each subject prior to participation. Seven blood pressure hyperreactors (4 athletes), who responded to the cold pressor test with a rise of 15 mmHg or greater in their systolic and/or diastolic blood pressure (Menkes et al 1989;Kasagi et al 1995), were excluded and analyzed separately (Table 1), because of their specific cardiovascular responses (Moriyama and Ifuku 2007). Of the remaining 17 subjects (9 females), 9 (4 females) were athletes (4 non-endurance track and field athletes, 1 endurance track and field athlete, 2 non-endurance competitive swimmers, 1 basketball player, and 1 soccer player) who had been practicing their sports for more than 7 years.…”

“…This pressor response is characterized by increased cardiac output during the initial period (0-30 s) (Yamamoto et al 1992) and by enhanced muscle sympathetic nerve activity (MSNA) during the later period (30-120 s) (Victor et al 1987;Yamamoto et al 1992). By (dP/dt)/P of carotid artery pulse, a non-invasive index of cardiac contractility reflecting the state of cardiac sympathetic nerve activity (Ifuku et al 1994), cardiac contractility increases during 0-90 s of cold-water immersion, but it dose not reflect the levels of heart rate and MSNA (Moriyama and Ifuku 2007).…”