Total Heart Beats Research Articles

Improved estimation of total oxygen uptake in exercise by evaluation of aerobic fitness.

The purpose of the present study was to contrive a new practical method for estimating total O2 uptake during exercise from total heart beats after individual evaluation of aerobic fitness levels. Twenty healthy male subjects participated in cycle ergometer tests, maximal O2 uptake (VO2max) tests and various simple tests including simple endurance tests. From the cycle ergometer results, the following formula for estimating total O2 uptake in exercise was determined: TVO2 (ml X kg-1) = SR125 X (45.8 X mean HR + 4268) X THB X 10(-4) where TVO2, THB, and mean HR are total O2 uptake, total heart beats, and mean heart rate (beats X min-1) in exercise, respectively, and SR125 is the slope of the regression line between accumulated heart beats and accumulated O2 uptake during exercise at 125 beats X min-1 of mean HR. SR125 had a significant correlation not only with VO2max but also with each score (X) in any simple endurance tests such as, for example, a step test for 2 min. In this case, accordingly, SR125 can be found as; SR125 = -0.00118X + 0.3478. These formulae indicate that the total O2 uptake of any exercising subject can be estimated from his total heart beats regardless of intensities of exercise when his aerobic fitness level is evaluated by the simple endurance test. The total O2 uptake estimated by our method was compared to that measured by the Douglas bag method, and the discrepancy between the two results was less than the errors of values estimated by traditional methods.

Effect of sublingual nitroglycerin on left ventricular function at rest and during spontaneous angina pectoris: Assessment with a radionuclide approach

Left ventricular function and size were assessed with equilibrium radionuclide angiography at rest and after administration of 0.6 mg of sublingual nitroglycerin in 12 patients with a history of previous myocardial infarction. Spontaneous angina developed in five patients and seven patients had no pain at the time of study. Sequential ejection fractions and end-diastolic and end-systolic volumes were developed by summing multiple R-R intervals to produce a composite time-activity curve. Volumes were calculated with a nongeometric method that utilizes counts at end-diastole and end-systole and is corrected for total heartbeats and plasma radioactivity. In the patients without acute ischemia, peak increase in ejection fraction occurred 6 to 8 minutes after ingestion of nitroglycerin and was associated with an equal decrease in end-diastolic and end-systolic volumes with no change in stroke volume. End-diastolic and end-systolic volumes, stroke volume, heart rate and systolic blood pressure all returned to baseline levels by 1 hour after nitroglycerin. In the patients with spontaneous angina, ejection fraction and stroke volume decreased before pain occurred. End-diastolic volume increased slightly (7 percent), but end-systolic volume increased markedly (38 percent), thus explaining the decrease in stroke volume. After nitroglycerin, end-diastolic volume and end-systolic volume and systolic blood pressure decreased and stroke volume and ejection fraction increased. Improvement in function occurred before relief of pain. It is concluded that the action of nitroglycerin on the left ventricle in patients without acute ischemia is to increase ejection fraction by an equal decrease in end-diastolic and end-systolic volumes with little change in stroke volume. A reduction in left ventricular function during acute ischemia precedes complaints of pain and is associated with an increase in end-systolic and end-diastolic volumes and a decrease in ejection fraction and stroke volume. In these patients, nitroglycerin appeared to contribute to relief of pain by decreasing end-diastolic volume and systolic blood pressure.

Single and divided doses of penbutolol

Penbutolol, a nonselective beta-adrenoreceptor antagonist, induced reduction of exercise-induced heartbeats for at least 24 hr after a single 40-mg oral dose, and was equipotent with respect to a 2 X 20-mg regimen over the same period. Ingestion for 7 days did not influence the pharmacodynamics or pharmacokinetics of penbutolol, and there was no cumulation of drug in serum. A relationship was found between the logarithms of measurable serum concentrations of penbutolol and the percentage reduction of total heartbeats. Absorption of oral penbutolol appeared to be reduced when administered in the evening. Since beta-adrenoceptor activity was relatively unchanged between 13 and 24 hr after a single 40-mg dose of penbutolol, there is a possibility that an active metabolite or metabolites may contribute to prolonged duration of action.

Integrated circuit system for digitizing arterial blood pressure and heart rate

The measurement of arterial blood pressure during physiological, pharmacological or behavioral manipulations generates a vast amount of data which must be reduced. Hand scoring is both time consuming and inaccurate, while on-line computer analysis may be prohibitively expensive. As an alternative, an inexpensive circuit is described which digitizes, stores, and prints out mean systolic and diastolic blood pressure, as well as heart rate, from up to four analog channels. Channels are sequentially digitized, each for an interval dialed on the front panel (1–999 sec). For each beat, a peak and trough detector enables the systolic and diastolic accumulators, respectively, thus storing two ten bit words from the analog to digital converter. For each systolic occurrence, a count of one is added to the heart rate counter. At the end of the recording interval, an output routine prints the interval number, mean systolic pressure, mean diastolic pressure, and total heart beats. Offset and gain controls allow precise calibration of various transducer and polygraph amplifiers.

Aortic medical calcification and lowered metabolism in ground squirrels.

THIS study was intended to test in mammals the concept that some animals have a potential physiological limit of energy which may be utilized at different rates depending upon environmental temperatures. McArthur and Baillie1 were able to triple the life-span of Daphnia (Crustacea) by a 20-deg. drop in temperature. The total heart beats during the life of the Daphnia differed by less than 2 per cent whether the duration of life was a few days due to high temperature or several months due to low temperature. Similarly, Carlson and Hoelzel2 prolonged the life-span of white rats by reducing their metabolism by partial starvation.