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Cardiovascular function accounts for endurance performance and, by a rapid increase in oxygen supply at the onset of exercise, contributes to short-lasting intensive exertion prevailing in many kinds of sports activities. This study determined the time for oxygen uptake (VO.sub.2]) to reach one half of its asymptotic level above rest, and the respective oxygen deficit following the onset of a constant-load exercise corresponding to 80% to 90% of the maximal oxygen uptake ([VO.sub.2]max) in 35 children after surgical closure of a ventricular septal defect, after corrective surgery for tetralogy of Fallot, or after the Senging, Mustard, or Fontan procedures. In addition, [VO.sub.2]max and maximal blood lactate were determined. The half-time of [VO.sub.2] response and oxygen deficit was lowest in patients after closure of a ventricular septal defect, whereas children had the most unfavorable [VO.sub.2] transient kinetics after Fontan operation or with a transannular patch after correction of tetralogy of Fallot. A negative correlation was evaluated between half-time of [VO.sub.2] response and [VO.sub.2]max, whereas maximal blood lactate varied independently of [VO.sub.2]max. It is concluded that many children with decreased [VO.sub.2]max after cardiac surgery also have unfavorable [VO.sub.2] transient kinetics. In addition to being less qualified for endurance performance, they are also less prepared for short-lasting intensive energy expenditure. Therefore, the primary aim of training in these children is to improve the economy of motion of the respective tasks.

The role of myocardial oxygen demand in the pathogenesis of silent ambulatory myocardial ischemia was evaluated by reviewing and assessing the methods and results of recent studies. The performance of simultaneous ambulatory electrocardiographic and blood pressure monitoring in 25 men with proven coronary artery disease (CAD) revealed significant increases in heart rate and blood pressure (p < 0.001) preceding most silent ischemic events. By plotting the mean heart rate obtained at 5-minute intervals during the 30 minutes before an ischemic event, the ischemic heart rate was shown to be significantly higher (95 [+ or -] 15 vs 74 [+ or -] 11 beats per minute [bpm]; p < 0.01) than the nonischemic heart rate. The evaluation of heart rate changes during ambulatory ischemia (in patients with CAD and ischemia induced by an exercise test using gradual work load increments) showed a significant heart rate increase (> 10 bpm) at 1-5 minutes preceding the onset of ST-segment depression. Heart rate increases during exercise testing according to the gradual work load increments of the National Institutes of Health protocol were compared with the heart rate preceding ischemic events during daily life monitored by ambulatory electrocardiography and were found to be closely related. In contrast, heart rate increases that occurred during exercise testing using the standard Bruce protocol were higher and correlated less with those preceding ischemia in dally life. Heart rate and blood pressure increased significantly in most silent ischemic episodes, indicating that increased myocardial oxygen demand plays a significant role in the pathogenesis of myocardial ischemia during daily life.

Cardiogenic shock is insufficient blood flow in the peripheral circulation, resulting from the failure of the heart to pump blood and maintain oxygen supply to body tissues. Myocardial infarction, or heart attack, may be followed by cardiogenic shock, but little is known about the oxygen transport in cardiogenic shock after a heart attack. Various measures of oxygen transport and responses to treatment were assessed in 19 patients with cardiogenic shock after a heart attack. In eight patients, hypoxemia (decreased blood oxygen level) was treated by mechanical ventilation, or providing oxygen by artificial means. Defibrillation, the restoration of normal heart rhythm, was performed in three patients, and five patients underwent pacing, a procedure for setting the heart rate. Three patients had normal blood pressure and cardiac output (the volume of blood pumped by the heart), despite the presence of shock, and recovered without further treatment. Fourteen of 16 patients treated with intravenous fluids and the drug dobutamine survived for further evaluation. Their heart rate and cardiac index, a measure of the blood volume pumped by the heart, increased. In addition, oxygen consumption, or the amount of oxygen used by the tissues, was maintained, despite a diminished oxygen supply. Treatment increased both oxygen consumption and the availability of oxygen to body tissues. The results also indicated that the tissues were extracting less oxygen from the blood. Thirteen patients survived and were discharged. (Consumer Summary produced by Reliance Medical Information, Inc.)