Exercise capacity in patients with severe left ventricular dysfunction.

Abstract

SUMMARY Normal or near-normal exercise capacity has been thought to reflect normal left ventricular function. Many compensatory mechanisms could preserve exercise capacity in patients with severe left ventricular dysfunction. We evaluated exercise capacity using a treadmill exercise test in 26 patients with severe left ventricular dysfunction defined by a left ventricular ejection fraction of 30% or less by isotope ventriculography. One half of the patients had normal exercise capacity and a normal cardiothoracic ratio on chest x-ray. This study indicates that traditional predictors of left ventricular function that have been widely used in clinical evaluation of the patients with cardiac disease (cardiothoracic ratio and exercise capacity) can be normal in a significant number of patients with severe left ventricular dysfunction. Thus, left ventricular function cannot be accurately estimated using these traditional predictors and should be assessed quantitatively. The isotope ventriculogram appears to be ideal for this purpose.IN PATIENTS with suspected or established cardiac disease, normal or near-normal exercise capacity has generally been thought to reflect normal left ventricular function. The rationale for this assumption is based on studies that have shown a close linear correlation between maximal oxygen consumption and cardiac output. 1-4 Furthermore, the assumption that exercise capacity relates to the severity of heart disease has formed the basis of the most commonly used clinical classification of patients with heart disease (New York Heart Association).Although left ventricular dysfunction may alter exercise capacity, many compensatory mechanisms could preserve exercise tolerance despite severe left ventricular dysfunction, including preservation of absolute stroke volume, chronotropic competence, increased oxygen extraction, altered left ventricular compliance or augmented pulmonary lymphatic flow. Therefore, we reevaluated exercise capacity in patients with severe left ventricular dysfunction. If a substantial number of patients with severe left ventricular dysfunction and near-normal exercise tolerance could be identified, the concept that exercise capacity is a predictor of left ventricular performance would be challenged.

<b>Value of Left Atrial Function in Predicting Exercise Capacity in Heart Failure With Moderate to Severe Left Ventricular Systolic Dysfunction</b>

“…1) Previous studies have demonstrated that left ventricular (LV) systolic function does not predict exercise capacity. 2,3) In contrast, recent reports showed that LV diastolic dysfunction was intimately related to functional status. 4,5) Although LV diastolic dysfunction is known to reduce exercise capacity, it is often difficult to predict precise exercise capacity by evaluating diastolic filling because hemodynamic parameters measured at rest are influenced by age, heart rate, loading condition, and the properties of the LV and left atria (LA).…”

Capacidade funcional de indivíduos com insuficiência cardíaca avaliada pelo teste de esforço cardiopulmonar e classificação da New York Heart Association

“…Foram encontradas correlações fracas entre FEVE e VO 2pico (r=0,13; p<0,01) e também entre FEVE e VE/VCO 2 (r=-0,16; p<0,01) 26 . Apesar da disfunção ventricular esquerda poder alterar a capacidade de esforço, tem sido proposto que mecanismos compensatórios podem preservar a tolerância ao exercício, dentre eles: aumento do volume diastólico final, competência cronotrópica, aumento da extração de oxigênio, alteração da complacência ventricular esquerda ou, ainda, aumento do fluxo linfático pulmonar 27 . Assim, embora a intolerância ao exercício seja o maior sintoma destes pacientes, não parece existir relação direta entre a função sistólica e a capacidade de realização do exercício.…”

Heart failure: why and how to define it?

“…However, the LVEF cut-off chosen to define heart failure differs between studies: values of 35% [2], 40% [3] and 45% [4] have all been used; thus, patients included in many studies are not comparable. Furthermore, L YEF correlates poorly with exercise capacity [5]. Results from clinical trials are often difficult to apply to data collected by epidemiologists because their definitions and inclusion criteria often differ from those used by epidemiologists.…”