Left ventricular function in response to the transition from aerobic to anaerobic metabolism

Abstract

The purpose of this investigation was to study myocardial function at rest, during three phases of energy supply, and during recovery. Radionuclide angiography was performed during the aerobic phase (phase I, rest-first lactate increase), the aerobic-anaerobic transition phase (phase II, first lactate increase-second lactate increase), the anaerobic phase (phase III, second lactate increase-maximal work performance (Pmax)), and during recovery. Thirty-eight male patients (59 +/- 7 d after myocardial infarction) were compared with 19 healthy control subjects and 21 sport students of comparable age. Left ventricular ejection fraction (LVEF) increased from rest to phase I and from phase I to phase II in sports students and control subjects. During phase III, LVEF did not change significantly in sports students, but it decreased significantly in control subjects. This is in contrast to the patients, who showed an increase of LVEF from resting values (47 +/- 3%) to phase I (50 +/- 1%), no change during phase II (51 +/- 2%), and a decrease to resting values (45 +/- 2) during phase III. All subjects showed an increase in stroke volume (SV) during phase I and II, reaching a maximum at phase II. This was evidenced by an improvement of the systolic function with a constant left ventricular end-diastolic volume (EDV) in control subjects and sports students. In contrast, an improved SV in patients was achieved through an increase in EDV and a less distinct increase in the left ventricular end-systolic volume (ESV). Maximal LVEF values were measured during the first 90 s of recovery in all subjects. Values during recovery are not representative of load dependent myocardial function. This increase in LVEF does not cause an increase in cardiac output but is a consequence of changes in the EDV and ESV, which decrease again immediately after the end of exercise performance.

Validity of the Modified Conconi Running Test

“…Another relevant parameter in the analysis of the S/HR relationship is S dp . It is suggested that S dp coincides with the beginning of a sharp accumulation of blood lactate [8,13,15], and that it correlates well with racing speed in aerobic conditions [8,22,31]. In the present study, we found a strong relationship between experimental values of S dp determined in T stand and T fast (l " Fig.…”

Heart rate deflection point as a strategy to defend stroke volume during incremental exercise

“…It is not clear whether the detection or lack of detection of a SV plateau and a HRDP with increasing exercise intensity was an adaptation to training, a genetic consequence, or a combination of both. Nevertheless, Pokan et al (25) reported the increase in the LVEF from rest to LT in 21 sports students. Thus it remained relatively constant until the maximal aerobic power attainment.…”

“…Beyond this methodological criticism, the cause of the HRDP phenomena can also be questioned. Although left ventricular ejection fraction (LVEF) increased from rest to the LT in healthy male subjects (12,25,26), the break point in the HR-work performance curve became less pronounced or was absent altogether when the decrease in LVEF toward the end of the incremental exercise became more distinct (24). Expressed as higher ejection fraction both at rest and during exercise, it has been established that the endurance-trained athletes had a better systolic function than untrained subjects (10,13).…”

Praxisleitlinien Ergometrie

“…Während stufenförmig ansteigender Körperarbeit kann die Energiebereitstellung in 3 Phasen unterteilt werden [8][9][10][11][12] (Abb. 2).…”

“…2). Im Gegensatz zu Gesunden, wo ein deutlicher Anstieg der linksventrikulären Auswurffraktion (LVEF) im Sinne einer Zunahme der myokardialen Funktion von Ruhe bis zum Über-gang von Phase II zu Phase III mit einer anschließenden Plateau-Bildung oder einer geringfügigen Abnahme der LVEF zu beobachten ist [8,13], kommt es bei Patienten mit koronarer Herzerkrankung zu einer deutlichen Abnahme der LVEF wäh-rend Phase III der Energiebereitstellung. Als Zeichen der myokardialen Überlastung kann die LVEF bei maximaler Belastung auf Werte unter den Ruhewert bei gleichzeitiger Zunahme des enddiastolischen Volumens absinken [8,14].…”