Mechanisms of exercise-induced pulmonary hypertension in patients with cardiac septal defects.

The objective of this study was to investigate mechanisms of exercise-induced pulmonary hypertension in patients with congenital cardiac septal defects. This was a randomized, placebo controlled, crossover drug trial in a single national pediatric cardiology centre that performs congenital cardiac defect surgery. There were 14 patients with cardiac septal defects and known exercise-induced pulmonary hypertension. The intervention consisted of 50 mg oral sildenafil versus placebo. Measurements included supine bicycle exercise echocardiography and oxygen uptake. The outcome measure was right-ventricular systolic pressure as estimated by Doppler tracings of tricuspid regurgitant jet as well as systolic and diastolic longitudinal myocardial velocities by color tissue Doppler echocardiography. Sildenafil did not change exercise right-ventricular systolic pressure during exercise; however, decreased systemic systolic pressure was seen. Enhanced biventricular longitudinal function with sildenafil compared with placebo was indicated by greater tissue Doppler velocities and displacement measurements during exercise. Finally, a less steep increase of right-ventricular pressure during exercise was associated with greater left-ventricular diastolic myocardial tissue Doppler velocity. Exercise-induced pulmonary hypertension in cardiac septal defects does not seem to have a pulmonary vasoconstrictive component, but it may be related to left-ventricular filling pressure. Furthermore, sildenafil improved biventricular systolic performance in this patient group, possibly related to decreased systemic afterload.

Energy requirements of tire pulling.

BACKGROUND: We have investigated the effect using walking poles and pulling tires at 4 and 6 km·h-1 (1.11 and 1.67 m·s-1) speeds on oxygen uptake (V̇O2) and heart rate. METHODS: Eleven subjects, 6 males, with a mean (SD) age of 25.2 (6.9) years participated in field tests involving walking without poles, walking with poles and tire pulling with poles. RESULTS: Increasing the load caused the largest increases in energy demand, more than 4 MET. Speed increase also caused substantial energy increase, approximately 4 MET. Increasing the inclination only modestly increased the oxygen uptake, approximately 2 MET. In both level walking and uphill walking, using poles marginally increased oxygen uptake compared to working without poles. Pulling one tire (12.5 kg) required an oxygen uptake of 27 (4) mL·kg-1·min-1 at 4 km·h-1 and 0% inclination. Adding one more tire (6 kg) drove the oxygen uptake further up to 39 (4) mL·kg-1·min-1. This is close to the requirement of level running at 10.5 km·h-1. Pulling both tires at 6 km·h-1 and 5% inclination required a V̇O2 of 54 (6) mL·kg-1·min-1, equal to running uphill at 5% inclination and 12.5 km·h-1 speed. Heart rate rose comparably with oxygen uptake. At 4 km·h-1 and 0% inclination the increase was 29 bpm, from 134 (21) to 163 (22) bpm when going from pulling one tire to two tires. In the hardest exercise, 6 km·h-1 and 5% inclination, heart rate reached 174 (14) bpm. CONCLUSIONS: The study showed that tire pulling even at slow speeds has an energy requirement that is so large that the activity may be feasible as endurance training.

Moderate altitude increases right ventricular pressure and oxygen desaturation in adolescents with surgically closed septal defect.

OBJECTIVES: Abnormal right ventricular systolic pressure response (RVPR) during exercise has previously been demonstrated in patients with septal defects of the heart. Our study investigated whether moderate altitude affects RVPR and oxygen saturation during rest and exercise in patients with surgically closed septal defects. DESIGN: Ten patients with surgically closed heart septal defects (six secundum atrial septal defects, four ventricular septal defects) were examined by cardiopulmonary exercise testing and by echocardiography at rest and during supine cycling at sea level. After 2 hours in a hypobaric chamber at 2500 m/8200 ft altitude, exercise echocardiography was repeated. RESULTS: During sea level exercise four patients showed abnormal RVPR (>50 mm Hg). Acute hypoxic exposure led to right ventricular systolic pressure increase above 40 mm Hg in two patients. During altitude exercise seven patients showed abnormal RVPR. Average maximal right ventricular systolic pressure was 56.5 ± 12.7 mm Hg and average for the lowest oxygen saturation was 80.0 ± 5.7%. Two patients had simultaneous oxygen desaturation below 80% and right ventricular systolic pressure above 50 mm Hg. CONCLUSIONS: Moderate altitude affects right ventricular systolic pressure and oxygen saturation in adolescents with surgically closed ventricular or atrial septal defects. Moderate altitude may induce or aggravate abnormal RVPR and oxygen desaturation during exercise in these patients.