We hypothesized that the extreme endurance exercise of an Ironman competition would lead to long-standing hemodynamic and autonomic changes. We investigated also the possibility of predicting competition performance from baseline hemodynamic and autonomic parameters. We have investigated 27 male athletes before competition, 1 h after, and then for the following week after the competition. The Task Force monitor was used to measure beat-to-beat hemodynamic and autonomic parameters during supine rest and active standing. Heart rate (P < 0.001) was increased, and stroke index (P = 0.011), systolic blood pressure (P = 0.004), diastolic blood pressure (P < 0.001), total peripheral resistance index (P < 0.001), and baroreceptor reflex sensitivity (P < 0.001) were decreased after the competition. The 0.05- to 0.17-Hz band of heart rate and blood pressure variability was increased (P < 0.001 and P < 0.001, respectively), the 0.17- to 0.40-Hz band of heart rate interval variability was decreased after the competition (P < 0.001). All parameters returned to baseline values 3 days after the competition. After the competition, the autonomic response to orthostasis was significantly impaired. The 0.05- to 0.17-Hz band of diastolic blood pressure variability before competition and weekly net exercise training, but not the other hemodynamic and autonomic parameters, were related to competition time in multivariate regression analysis (multiple r = 0.70, P < 0.001). The marked hemodynamic and autonomic changes after an ultraendurance race, which are compatible with myocardial depression in the face of sympathetic activation and reduction of afterload, return to baseline after only 1-3 days. Because the 0.05- to 0.17-Hz band of diastolic blood pressure variability contributes to the prediction of competition time, the analysis of blood pressure variability in the frequency domain deserves further study for the prediction of endurance capacity.

Fast performance in the marathon is associated with low sympathetic modulation of vasomotor tone, maintained stroke index postcompetition and enhanced exercise-induced vasodilatation. We postulate that maintaining a low level of sympathetic modulation to resistance vessels during the course of training may indicate its appropriateness, thus enabling fast performance by optimal postexercise vasodilatation and by prevention of postcompetition cardiac dysfunction. This will have to be tested in future longitudinal studies.

Post-exercise OI is associated with a 'high basal sympathetic modulation of vasomotor tone in combination with a diminished orthostatic sympathetic response' to resistance vessels. This situation may mimic the OI in some clinical conditions, which are also known to be associated with increased 'basal' sympathetic tone. The role of serum potassium deserves further study.

Central neutral activity may selectively influence cardiac regions. As an index of this, rate constants of norepinephrine turnover, KNE, in regions of guinea pig heart were determined by 1) disappearance of [3H]NE from tissues, and 2) conversion of [3H]tyrosine to [3H]NE. In sinoatrial (SA) node and right atrial appendage, KNE averaged 0.084 +/- 0.014 and 0.066 +/- 0.004 (SE) h-1, respectively (P greater than 0.05). In other specialized regions, KNE was lower than in SA node (P less than 0.05). In other contractile regions, KNE was lower than in right atrial appendage (P less than 0.05). Ganglionic blockade reduced KNE to uniform values in all heart regions. Cold stress increased KNE markedly (P less than 0.05) throughout the heart, but selectively more in SA node, AV node, proximal conduction bundles, and right atrial appendage (P less than 0.05). At room temperature, neural activity is greater to the right atrium including SA node than to other cardiac regions. At 4 degrees C, neural activity increases selectively in the right atrium and the conduction system. This suggests that central neural mechanisms contribute significantly to nonuniform cardiac regulation under conditions of progressive sympathetic activation.

Psychoanalytical initial interviews were monitored by cameras while, at the same time, both the patient’s and the doctor’s ECGs were telemetrically recorded. Changes of heart rate were related to intra- aswell as interpersonal occurrences during the interview. Both concordant and discordant courses were seen: communicative structures of the interview in some cases correlate with the pattern of heart rate. Cardiophobics, with their tendency to cling to the doctor, reveal a corresponding heart rate pattern. In a finally described case, bigeminy attacks during the interview could be related to special transference phenomena.