No abstract

SummaryIn able-bodied subjects heart rate and oxygen uptake have a linear relation up to submaximal workloads. Cardiac response to exercise or physical stress is described to be under the control of the sympathetic nervous system. Various workers have claimed that the sympathetic contribution to the cardiac plexus arises between thoracic spinal cord levels Tl and T6. Paraplegics are participating in various sporting activities in increasing numbers. Theoretically, assessing the progress of physical fitness of paraplegics with lesions above T6 by monitoring heart rate alone becomes unreliable because of damage to their sympathetic system. Forty-four paraplegics with lesion levels between T3 and TIO were put through an arm cranking exercise routine with increasing power levels. Their heart rate and oxygen uptake was measured for each power level. For analytical purposes the subjects were grouped into two groups according to their lesion level. All the subjects with the lesion at T6 or above were in one group and the other group consisted of lesion at T7 or below.Almost linear relation was found between the heart rate and oxygen uptake in all subjects of both groups.The findings of this study suggest that either the sympathetic contribution comes from above spinal level T3, or the cardiac response to an increased demand in physical exercise is controlled by some other mechanism.

Several recent studies evaluated a possible effect of the prothrombotic polymorphisms such as 5,10 methylenetetrahydrofolate reductase (MTHFR) nt 677C → T, factor V (F V) nt 1691G → A (F V Leiden), and factor II (F II) nt 20210 G → A on the risk of myocardial infarction. In the present study, we analyzed the effect of these prothrombotic polymorphisms, as well as apolipoprotein (Apo) E4, smoking, hypertension, diabetes mellitus, and hypercholesterolemia, on the risk of myocardial infarction in young males. We conducted a case-control study of 112 young males with first acute myocardial infarction (AMI) before the age of 52 and 187 healthy controls of similar age. The prevalences of heterozygotes for F V G1691A and F II G20210A were not significantly different between cases and controls (6.3% v 6.4% and 5.9% v 3.4% among cases and controls, respectively). In contrast, the prevalence of MTHFR 677T homozygosity and the allele frequency of Apo E4 were significantly higher among patients (24.1% v 10.7% and 9.4% v5.3% among cases and controls, respectively). Concomitant presence of hypertension, hypercholesterolemia, or diabetes and one or more of the four examined polymorphisms increased the risk by almost ninefold (odds ratio [OR] = 8.66; 95% confidence interval [CI], 3.49 to 21.5) and concomitant smoking by almost 18-fold (OR = 17.6; 95% CI, 6.30 to 48.9). When all atherogenic risk factors were analyzed simultaneously by a logistic model, the combination of prothrombotic and Apo E4 polymorphisms with current smoking increased the risk 25-fold (OR = 24.7; 95% CI, 7.17 to 84.9).The presented data suggest a synergistic effect between atherogenic and thrombogenic risk factors in the pathogenesis of AMI, as was recently found in a similar cohort of women.