Left ventricular markers of global dyssynchrony predict limited exercise capacity in heart failure, but not in patients with preserved ejection fraction

Abstract

BackgroundThe aim of this study was to prospectively examine echocardiographic parameters that correlate and predict functional capacity assessed by 6 min walk test (6-MWT) in patients with heart failure (HF), irrespective of ejection fraction (EF).MethodsIn 147 HF patients (mean age 61 ± 11 years, 50.3% male), a 6-MWT and an echo-Doppler study were performed in the same day. Global LV dyssynchrony was indirectly assessed by total isovolumic time - t-IVT [in s/min; calculated as: 60 – (total ejection time + total filling time)], and Tei index (t-IVT/ejection time). Patients were divided into two groups based on the 6-MWT distance (Group I: ≤300 m and Group II: >300 m), and also in two groups according to EF (Group A: LVEF ≥ 45% and Group B: LVEF < 45%).ResultsIn the cohort of patients as a whole, the 6-MWT correlated with t-IVT (r = −0.49, p < 0.001) and Tei index (r = −0.43, p < 0.001) but not with any of the other clinical or echocardiographic parameters. Group I had lower hemoglobin level (p = 0.02), lower EF (p = 0.003), larger left atrium (p = 0.02), thicker interventricular septum (p = 0.02), lower A wave (p = 0.01) and lateral wall late diastolic myocardial velocity a’ (p = 0.047), longer isovolumic relaxation time (r = 0.003) and longer t-IVT (p = 0.03), compared with Group II. In the patients cohort as a whole, only t-IVT ratio [1.257 (1.071-1.476), p = 0.005], LV EF [0.947 (0.903-0.993), p = 0.02], and E/A ratio [0.553 (0.315-0.972), p = 0.04] independently predicted poor 6-MWT performance (<300 m) in multivariate analysis. None of the echocardiographic measurements predicted exercise tolerance in HFpEF.ConclusionIn patients with HF, the limited exercise capacity, assessed by 6-MWT, is related mostly to severity of global LV dyssynchrony, more than EF or raised filling pressures. The lack of exercise predictors in HFpEF reflects its multifactorial pathophysiology.

The impact of age on cardiac electromechanical function in asymptomatic individuals

“…Finally, nature seems to dictate that the overall LV pump function shown by ejection fraction and its time relations with isovolumic contraction time are normally independent of cavity size and wall thickness, but they become related to each other in symptomatic patients with heart failure and enlarged LV cavity, suggesting a pathological crossing of natural boundary. A further support of this suggestion is the lack of such relationship in patients with symptomatic heart failure but preserved LV cavity size and ejection fraction . The same applies to the normal relationship between LV E/A ratio in asymptomatic individuals which when pseudonormalize as they develop symptoms suggest raised filling pressures and unstable cardiac physiology …”

“…Short LV filling time due to fast heart rate with exercise or loss of the atrial contribution to filling due to atrial fibrillation, may be the main factors behind symptom development in heart failure . Likewise, short ejection time due to early systolic dyssynchrony contributes to compromise stroke volume and symptoms …”

Left ventricular systolic dysfunction potentially contributes to the symptoms in heart failure with preserved ejection fraction

“…A previous study highlighted the incidence of LV diastolic function in the progression of HfpEF and the role of concomitant LV systolic performance, including LV systolic function and synchrony in the setting of LVDD with or without HF symptoms, which may help to guide further management strategies . Moreover, impaired LV longitudinal systolic dysfunction is significantly deteriorated by mechanical dyssynchrony in HF with reduced ejection fraction (HFrEF) . However, whether LV mechanical dyssynchrony promotes progressive impairment of LV systolic function, which eventually progresses to clinical HF in patients with LVDD, remains unclear.…”

Predictors of exercise capacity in heart failure

“…the main concern for professionals is the patient's limiting symptoms and the mechanisms behind them. several LV function parameters have been shown to predict patient's exercise capacity 12,13 assessed by six-minute walk test -6-MWt [14][15][16][17] . Despite the fact that 6-MWt itself has been used to assess functional status of HF patients 18 and to predict prognosis 19,20 it is limited to a relatively few cardiac centres or specialized units.…”