Clinical Investigation
Exercise Echocardiography
Cardiac Reserve and Exercise Capacity: Insights from Combined Cardiopulmonary and Exercise Echocardiography Stress Testing

https://doi.org/10.1016/j.echo.2020.08.015Get rights and content

Highlights

  • Cardiopulmonary exercise/stress echo to study effort intolerance in heart failure.

  • Peak oxygen consumption (VO2) is directly related to measures of cardiac function.

  • Left ventricle systolic function is an independent predictor of effort intolerance.

  • Left atrial compliance/right ventricle-arterial coupling can also predict peak VO2.

Background

Cardiopulmonary exercise testing (CPET) represents the gold standard to estimate peak oxygen consumption (VO2) noninvasively. To improve the analysis of the mechanisms behind effort intolerance, we examined whether exercise stress echocardiography measurements relate to directly measured peak VO2 during exercise in a large cohort of patients within the heart failure (HF) spectrum.

Methods

We performed a symptom-limited graded ramp bicycle CPET exercise stress echocardiography in 30 healthy controls and 357 patients: 113 at risk of developing HF (American College of Cardiology/American Heart Association stage A-B) and 244 in HF stage C with preserved (HFpEF, n = 101) or reduced ejection fraction (HFrEF, n = 143).

Results

Peak VO2 significantly decreased from controls (23, 21.7–29.7 mL/kg/minute; median, interquartile range) to stage A-B (18, 15.4-20.7 mL/kg/minute) and stage C (HFpEF: 13.6, 11.8-16.8 mL/kg/minute; HFrEF: 14.2, 10.7-17.5 mL/kg/minute). A regression model to predict peak VO2 revealed that peak left ventricular (LV) systolic annulus tissue velocity (S′), peak tricuspid annular plane systolic excursion/systolic pulmonary artery pressure (right ventricle-pulmonary artery coupling), and low-load left atrial (LA) reservoir strain/E/e’ (LA compliance) were independent predictors, in addition to peak heart rate, stroke volume, and workload (adjusted R2 = 0.76, P < .0001). The model was successfully tested in subjects with atrial fibrillation (n = 49) and with (n = 224) and without (n = 163) beta-blockers (all P < .01). Peak S′ showed the highest accuracy in predicting peak VO2 < 10 mL/kg/minute (cut point ≤ 7.5 cm/sec, area under the curve = 0.92, P < .0001) and peak VO2 > 20 mL/kg/minute (cut point > 12.5 cm/sec, area under the curve = 0.84, P < .0001) in comparison with the other cardiac variables of the model (P < .05).

Conclusions

Peak VO2 is directly related to measures of LV systolic function, LA compliance, and right ventricle-pulmonary artery coupling, in addition to heart rate and stroke volume and independently of workload, age, and sex. The evaluation of cardiac mechanics may provide more insights into the causes of effort intolerance in subjects from HF stages A-C.

Section snippets

Study Population

We prospectively enrolled 465 consecutive patients referred for dyspnea to the University Hospital of Pisa between September 2017 and February 2020 (Figure 1). All patients fell within the ACC/AHA HF stage A (asymptomatic subjects with cardiovascular risk factors), stage B (structural heart disease without signs or symptoms of HF), or stage C (clinically overt HF). Arterial hypertension (AH) was defined by the presence of at least two BP recordings >140/90 mm Hg or treatment with

Study Population

Demographic and clinical characteristics of the population are shown in Table 1. There were no significant differences in terms of age and sex between patient subgroups. Individuals in stage A-B had the largest body mass index and the highest prevalence of AH, dyslipidemia, and diabetes mellitus; stage C patients showed the highest prevalence of CKD, but there were no patients receiving dialysis. Stage C HFrEF profile was characterized by coronary artery disease with its complications and

Discussion

Peak VO2 during exercise is directly related to measures of LV and LA function and RV-PA coupling, in addition to central components of the Fick principle (i.e., HR and SV) and independently of workload, age, and sex. The evaluation of cardiac mechanics using an integrated CPET-ESE approach provides valuable knowledge about the factors that may determine effort intolerance across the spectrum of HF, above and beyond insights assessed only in resting conditions. We summarized in Figure 5 the

Conclusion

The necessity of studying multiple aspects of the cardiovascular system is growing strong to fill the gaps in HF management, mainly for HFpEF and subjects at risk of developing it.34,35 A functional model including different aspects of cardiac function may enable more mechanistic insight into the nature of VO2 impairment during exercise. The measurement of HR, SV, LV contractility, LA compliance, and RV-PA coupling is feasible in a combined CPET-ESE approach and can identify different causes of

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  • Cited by (0)

    The last two authors should be considered the same in author order.

    Conflicts of Interest: None.

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