Linde-Edelstam et al. demonstrated that the importance of atrial contraction to ventricular filling diminishes in accordance with increasing blood flow velocity as the exercise work load increases . Furthermore, left atrial pressure determines the contribution of atrial contraction to LV filling, and the elevation of pulmonary capillary wedge pressure was reported to diminish the power of atrial contraction on the cardiac output . These studies suggest that multiple factors affect the contribution of atrial-derived factors on the cardiac output. Further investigations should be conducted to better understand the mechanism underlying decreased Odos pulse in AF patients.
Another interesting aspect of this manuscript is the close association between the HR response and increase in the O2 pulse above the AT level. The inverse association between HR change, which is a marker of chronotropy, and the increase in the O2 pulse above the AT level is strikingly enhanced in AF patients. The HR change during exercise could predict the trend of the O2 pulse at the submaximal stage. In addition, there were two different groups with different trends in the O2 pulse in AF patients; one wherein VO2 is maintained above the AT level by increasing HR and one wherein VO2 is maintained by increasing the stroke volume. The blunted increase in the O2 pulse above the AT level corresponded to the enhanced response of chronotropy, maintaining the value of VO2/kg. However, there were no differences in laboratory data, echocardiographic parameters, and medication profiles.
Multiple research has presented the fresh association between Hours otherwise Hour effect and practice ability [21,22]. The new enhanced Time reaction into the AF patients could have been displayed from inside the earlier degree [fourteen,23] and it has started said to be on account of an elevated sympathetic drive brought about to maintain cardiac production. not, growing Hours will not usually increase exercise endurance otherwise attacks in the AF people . Indeed, the amount of exaggerated chronotropic effect evoked an unfavorable influence on cardiac output over the moderate intensity of do so additionally the undesirable impression is actually way more increased within the AF customers. Contained in this data, discover no significant difference inside the Hr trend ranging from AF and you will cSR clients, that’ll have demostrated various connection off Hr impulse while the transform off cardiac efficiency anywhere between AF and you will cSR clients much more advanced level styles. The fresh new determinant things out of chronotropy in the AF customers had been justified a lot more concisely [twenty-five,26]. Another you can easily deciding grounds of chronotropy in AF is actually atrial setting, including atrial appendage draining acceleration or atrial contractile setting. So you can be certain that they, more detailed testing off atrial mode can be performed.
Yet not, the partnership ranging from exercise capacity and you may Hour response is more difficult within the AF clients
The findings of the current study suggested that, aerobic exercise is generally performed as a main protocol of cardiac rehabilitation, in which the change of O2 pulse during exercise had similar behavior between patients with sinus rhythm and AF. However, the exercise capacity is significantly impaired above the level of AT and the change of HR reflected the burden of exercise in a more exaggerated manner in patients with AF than patients with sinus rhythm.
5. Data restrictions
There are several limitations in the present study, which includes a small study population without healthy controls. In addition, the patient population was limited to those receiving cardiac rehabilitation, which could evoke referral bias because patients referred for cardiac rehabilitation are not representative of the general community population. In selecting cSR patients, there was some possibility that they were different from SR patients and the difference of chronotropic competency may be a candidate to segregate the cSR group from a general SR group, which, however, is above the scope of this study. The elucidation of basic characteristics of these classifications is also warranted. Because the disease severity in our patients was mild and the study population included only Japanese patients, the results should be carefully interpreted when applied to different populations. The voluntary participation of the study patients in ambulatory cardiac rehabilitation may introduce some bias in the present study. In addition, the study design was limited regarding the evaluation of the effect of medications. Among them, the medication of beta blockers should be carefully considered because it might significantly affect the behavior of HR lovestruck. However, there were no significant differences in HR trend, VO2/kg trend during exercise in AF patients in this study.