Left ventricular functional response to moderate and intense exercise.
ABSTRACT The left ventricular (LV) volume and ejection fraction (EF) response to upright exercise was assessed on 15 normal subjects during cycle ergometry. Measures of cardiac function and gas exchange were made at rest, at 85% of the ventilatory anaerobic threshold (VAT; WL1), and at peak exercise (WL2). EF increased from rest (58 +/- 12%) during WL1 (66 +/- 10%), reaching significantly higher values at WL2 (69 +/- 8%; p less than .05). End-diastolic volume increased from rest during WL1 (136 +/- 36 ml vs. 118 +/- 32 ml; p less than .05), becoming significantly higher than rest during WL2 (141 +/- 41 ml). End-systolic volume was unchanged from rest (51 +/- 25 ml) during submaximal exercise (50 +/- 20 ml), but it decreased significantly during WL2 (44 +/- 21 ml; p less than .05). The systolic pressure/end-systolic volume ratio increased from 3.0 +/- 1.7 (rest) to 5.8 +/- 3.0 at WL2 (p less than .05). These results suggest that the Frank-Starling mechanism is operative throughout exercise, particularly during exercise below the VAT. LV performance after the VAT is further augmented by increased contractility with continued, yet diminished, utilization of the Frank-Starling mechanism.
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ABSTRACT: The assessment of cardiac function, particularly cardiac output (Q) during heavy exercise is essential for the evaluation of cardiovascular factors that might limit oxygen transport. A series of invasive and noninvasive techniques has been developed for the assessment and monitoring of Q during resting and submaximal exercise conditions. However, very few techniques have been found to give accurate and reliable determinations of Q during vigorous to maximum exercise. For exercise physiologists and sport cardiologists, maximal exercise data are of primary importance. The 'gold standard' measures of cardiac function are considered to be the direct Fick and dye-dilution methods. These have been widely shown to give accurate and reliable determinations of Q during resting and submaximal exercise conditions; however, their use during maximal exercise conditions is debatable due to the inherent risks involved with each and their increasing inaccuracy during the later stages of vigorous exercise. Thermodilution has also been considered to be a relatively good method for the determination of Q during rest and exercise conditions, but recent authors have questioned its use due to the nature of the measure and its inaccuracy during strenuous exercise. Various noninvasive measures of cardiac function have been developed to overcome the problems associated with the 'gold standard' measures. The first part of this article discusses conventional techniques used in exercise physiology settings. The majority of these provide accurate and reliable determinations of Q during rest and submaximal exercise. However, very few techniques are suitable for maximal exercise conditions. Perhaps only the foreign gas rebreathe using acetylene (C2H2) meets all the criteria of being noninvasive, simple to use, reliable over repeated measurements, accurate and useful during maximal exercise.Sports Medicine 02/1999; 27(1):23-41. · 5.32 Impact Factor
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ABSTRACT: Training adaptations in patients with coronary artery disease (CAD) have been reported previously, but little is known about central and peripheral adaptations in those recovering from coronary artery bypass graft surgery (CABG). The purpose of this study was to examine the effects of 12 weeks of endurance exercise training on exercise performance and left ventricular and peripheral vascular reserve in a group of uncomplicated CABG patients. Thirty-one patients were recruited and began training 8 to 10 weeks after uncomplicated CABG. Patients underwent progressive exercise training consisting of walking and jogging, at 75% to 80% maximal oxygen intake (VO2max). Measures of left ventricular function included ejection fraction (EF), ventricular volumes, and the pressure volume ratio, an index of contractility. Peak ischemic exercise calf blood flow and vascular conductance was determined using strain-gauge plethysmography. Maximal oxygen intake and submaximal blood lactate concentration also was determined. A significant improvement in VO2max (1497 +/- 60 mL/min versus 1691 +/- 71 mL/min) was observed after training. This change was accompanied by an increase in the EF during submaximal exercise (60 +/- 3% versus 63 +/- 2% at 40% VO2max; 61 +/- 3% versus 64 +/- 3% at 70% VO2max) (P < 0.05), and the change in EF from rest to exercise (delta EF). No changes were observed for ventricular volumes during exercise, although there was a trend for a higher stroke volume at 70% VO2max. A significant increase (18%) was observed for peak ischemic exercise calf blood flow and vascular conductance. In addition, submaximal blood lactate concentration was lower after training. These data indicate that exercise training for 12 weeks in patients recovering from CABG can elicit significant improvements in functional capacity that, for the most part, are secondary to peripheral adaptations, with limited support for improvement in left ventricular function.Journal of Cardiopulmonary Rehabilitation 01/1999; 19(3):144-50.
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ABSTRACT: We assessed left ventricular systolic and diastolic performance during and after prolonged exercise under controlled conditions in a group of healthy, trained men. Previous studies have examined the effects of prolonged effort on left ventricular function, yet it remains unclear whether or not left ventricular dysfunction (e.g. cardiac fatigue) can be produced under such conditions. We studied 15 healthy men, aged 27+/-1 years (mean+/-S.E.M.). Subjects exercised on bicycles at a constant work rate (60% of maximum oxygen uptake per min) for 150 min. Measurements of gas exchange, blood pressure and haematocrit were obtained, concurrent with the assessment of left ventricular function using equilibrium radionuclide angiography, at rest, during exercise (every 30 min) and after 30 min of recovery. Fluid replacement was provided and monitored during the exercise period. The baseline resting and exercise ejection fractions were 66+/-2% and 78+/-2% respectively. During exercise, subjects consumed 1816+/-136 ml of fluid, and the haematocrit had increased at 120 min of exercise (from 47.2%+/-0.6 to 49.9+/-0.8%; P<0.05). There was no change in either systolic or diastolic blood pressure throughout the exercise period, but heart rate drifted upwards from 141+/-2 beats/min after 30 min to 154+/-3 beats/min after 150 min (P<0.05). There was a small decline (8%; P<0.05) in end-diastolic volume at 150 min. No changes were observed in left ventricular ejection fraction, the pressure/volume ratio or end-systolic volume. After 30 min of sitting in recovery, heart rate was still higher than the pre-exercise value (84+/-3 compared with 69+/-2 beats/min; P<0.05), as were measures of peak filling rate and time to peak filling (P<0.05). The ejection fraction in the post-exercise recovery period was similar to the pre-exercise value. The results indicate that prolonged exercise of moderate duration may not induce abnormal left ventricular systolic function or cardiac fatigue during exercise.Clinical Science 06/2001; 100(5):529-37. · 4.86 Impact Factor