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PubMed1999

Cholinergic stimulation with pyridostigmine blunts the cardiac responses to mental stress.

Mental stress may induce myocardial ischemia and ventricular arrhythmia in patients with coronary artery disease, and cholinergic stimulation is a potential protective mechanism. The purpose of this study was to determine the effect of pyridostigmine bromide (PYR), a reversible cholinesterase inhibitor, on the cardiac responses to a mental stress challenge. Twelve healthy young volunteers were submitted to a mental stress test (arithmetic test) 2 hours after the oral administration of either placebo or PYR (45 mg) on two separate days, following a randomized crossover double-blind protocol. Heart rate was reduced after both placebo and PYR (p < 0.05), but the cardiac responses to the mental stress were lower with PYR (p < 0.05): mean RR interval (mean +/- SE)-placebo: 730 +/- 19 msec; PYR: 769 +/- 21 msec; Peak systolic pressure-placebo: 129 +/- 4 mmHg; PYR: 124 +/- 3 mmHg; Peak diastolic pressure-placebo: 92 +/- 3 mmHg; PYR: 89 +/- 4 mmHg; Mean rate-pressure product-placebo: 10,496 +/- 412 bpm x mmHg; PYR: 9,746 +/- 383 bpm x mmHg. In conclusion, 45 mg of pyridostigmine blunted the pressor and chronotropic responses to mental stress in healthy young subjects.

Aged↗

PubMed1994

[Not Available].

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Female↗

PubMed1994

[Initial heart rate transient at dynamic exercise performed in apnea. Influence of the variation rate of previous lung volume].

PURPOSE: To study the influence of inspiratory flow on the heart rate (HR) responses during the four-second exercise test (4sET) as a method to estimate cardiac vagal activity. METHODS: Fifteen healthy subjects performed the 4sET under two experimental situations: a) with maximal individual inspiratory flow (MIF) and b) with a slow inspiratory flow adjusted to reach total lung capacity in 4s (SIF). Vagal activity was estimated from B/C ratio obtained in ECG tracings, where B is the last R-R interval before the onset of exercise and C is the shortest R-R interval during exertion. RESULTS: Similar inspiratory capacities were reached, with significantly different inspiratory flows [mean (se)] [MIF = 2.23 (0.28) 1.s-1 and SIF = 0.59 (0.06) 1.s-1; t = 6.69; p < 0.0001]; as a result, it was observed a greater B/C ratio in MIF [1.36 (0.05)] as compared to SIF [1.13 (0.04); t = 4.42; p = 0.0006]. The inspiratory flow influenced HR responses in the 4sET. The biphasic transient induced by inspiration, with a HR acceleration followed by a relative bradycardia, has not been completed before exercise in the 4sET with SIF. CONCLUSION: Lower values of B/C in the 4sET with SIF seemed to be due to overlapping effects of apnea and exertion on HR during cycling. On the other hand, when the inspiration was performed at MIF, the oscillatory effect of respiration upon HR was completed before the onset of exercise. Therefore, the tachycardia observed during the 4sET performed after individual maximal inspiratory flow represents the isolated effect of dynamic exercise.

Adolescent↗