Author + information
- Richard B. Thompson, PhD∗ (, )
- Joseph J. Pagano, MD,
- Kelvin Chow, PhD,
- Viktor Sekowski, BSc,
- Ian Paterson, MD,
- Justin Ezekowitz, MBBCh, MSc,
- Todd Anderson, MD,
- Jason R.B. Dyck, PhD,
- Mark J. Haykowsky, PhD,
- on behalf of the Alberta HEART investigators
- ↵∗Department of Biomedical Engineering, 1082 Research Transition Facility, University of Alberta, Edmonton, Alberta T6G 2V2, Canada
A cardinal feature of heart failure (HF) is reduced exercise tolerance (peak oxygen uptake [Vo2]) that is associated with dyspnea and increased left ventricular (LV) filling pressure (1). Elevated resting LV filling pressures in patients with HF have been shown to be associated with increased lung water density measured with magnetic resonance imaging (2); however, the relationship between lung water content and peak Vo2 has not been evaluated. We measured peak Vo2, lung water density, and cardiac structure and function in clinically stable outpatients, older patients with HF with preserved ejection fraction (HFpEF) (n = 23) or HF with reduced ejection fraction (HFrEF) (n = 23), and 16 age-matched healthy control subjects from the Alberta HEART (Heart Failure Etiology and Analysis Research Team) study (3).
Cardiopulmonary exercise testing was performed in the upright position on a cycle ergometer during which time Vo2, heart rate, and blood pressure were measured. All HF patients were classified into those above (HF Group A) or below (HF Group B) a peak Vo2 of 15.4 ml/kg/min, which has been previously described as the threshold for independent living (4). A resting cardiac magnetic resonance imaging exam was used to measure lung water density (2), cardiac structure, and function.
By design, peak Vo2 was lower in HF Group B versus HF Group A patients and versus healthy control subjects (Table 1). Peak exercise power output, heart rate, and systolic and diastolic blood pressure were significantly lower in HF Group B patients compared with HF Group A patients and control subjects. Cardiac structure and function were similar in the HF Group A and HF Group B patients; however, lung water density was significantly higher in the HF Group B patients (Table 1) and lung water density was linearly correlated with peak Vo2 in all patients (R = −0.44; p = 0.01). Lung water density was similar in those HF patients with preserved or reduced ejection fraction (Table 1).
A novel finding of this study is that patients with HFrEF and HFpEF with a peak Vo2 below the threshold level associated with independent living (HF Group B) have relatively higher lung water density (23% higher) compared with HF patients with a peak Vo2 above the independence threshold (HF Group A) and healthy age-matched control subjects. Based on our previous finding that lung water is positively related to LV filling pressure (2), it is likely that the HF Group B patients have chronically increased filling pressures. Indeed, Dhakal et al. (1), using invasive hemodynamic measures coupled with respiratory gas exchange parameters during upright cycle exercise, reported LV filling pressures of 21 mm Hg at rest and 29 mm Hg at peak exercise in HF patients with similar peak Vo2 to our HF Group B patients. Importantly, quantification of lung water content, as compared with invasively measured filling pressure or B-type natriuretic peptide, provides additional information regarding an individual’s capacity to manage increased filling pressure, to clear fluids from the pulmonary system, as noted for other pulmonary imaging methods applied to HF such as ultrasound B-line count (5). Because pulmonary congestion is itself a clinical symptom linked to hospitalization and because it can impair pulmonary oxygen diffusing capacity, quantitative noninvasive assessment of lung water density may offer new insights into the characterization of HF.
Please note: Dr. Haykowsky’s research is supported by the Moritz Chair in Geriatrics, College of Nursing and Health Innovation, at the University of Texas and the National Institute of Nursing Research of the National Institutes of Health (Grant No. R15NR016826). Dr. Chow is a full-time employee of Siemens Medical Solutions. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- 2017 American College of Cardiology Foundation
- Dhakal B.P.,
- Malhotra R.,
- Murphy R.M.,
- et al.
- Thompson R.B.,
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