Left ventricular functional response to moderate and intense exercise.
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.
Available from: Asbjørn Støylen
- "The constant E/E a indicates a constant filling pressure, and thus no indication of Frank–Starling mechanism. E/E a ratio is slightly higher than in previous studies   , as tissue velocity is by colour Doppler  . The lack of evidence of the Frank– Starling effect in this group of young males is in accordance with Gerstenblith et al.  . "
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ABSTRACT: To study left ventricular mechanics of exercise with Doppler and tissue Doppler.
Twenty-one males (mean age, 26; height, 184 cm; weight, 84 kg), exercised on a bicycle, with increasing workload, with oxygen uptake, Doppler flow and tissue Doppler recordings during exercise. There was correlation between peak systolic LVOT flow and annulus velocity; R=0.72, (p<0.001) and between peak mitral E flow and annulus E(a) velocity; R=0.68(p<0.001). Finally there was correlation between peak LVOT and mitral flow velocity; R=0.83(p<0.001) and peak systolic and early diastolic annulus velocity R=0.69(p<0.001). All intervals of the heart cycle decreased with RR-interval. There was a linear relation between diastolic filling and RR-interval, while ejection period was less increased with RR-intervals above 600 ms, and thus not a linear relationship. There was no change in E/E(a) ratio during exercise.
Mechanism for increased filling as well as ejection during exercise seems to be increased contraction and relaxation velocity, with no evidence of Frank-Starling mechanism. Bazett's formula gives a better heart rate correction of LVET at high heart rates than Weissler's.
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ABSTRACT: Exercise testing is a valuable tool to assess cardiopulmonary function. It can define the limits of performance in an athlete or the functional capabilities of the patient with heart disease. Exercise capacity is determined most accurately by ventilatory oxygen uptake, which is defined by maximal cardiac output and the ability to extract and utilize oxygen in the working muscle. A given increase in cardiac output must be matched by a concomitant increase in ventilation, such that efficient pulmonary gas exchange can occur. The increase in cardiac output required by an exercise test places major demands on the heart muscle; the increase in myocardial oxygen demand can bring out abnormalities not apparent at rest. Thus, the exercise test is useful clinically to assess cardiac perfusion and function under controlled conditions. The physiologic response to exercise is influenced by the state of health and fitness, age, gender, the type of exercise, exercise position, and the environment. A good understanding of the basic physiologic responses to acute exercise can assist the clinician in applying the information gained from the exercise test to patients with cardiovascular disease. In addition to diagnostic and prognostic information, these applications include the assessment of therapy, exercise prescription, and hemodynamic responses.
Available from: Livia Maria dos Santos Sabbag
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