Cardiovascular death risk in mid-range ejection fraction heart failure: insights from cardiopulmonary exercise test

Background

The pivotal role of cardiopulmonary exercise testing (CPET) in the assessment of functional capacity and prognosis of patients with heart failure with reduced ejection fraction (HFrEF), either as a single CPET parameter (i.e. peak oxygen uptake, peak VO2), as a combination of CPET parameters (i.e. oxygen uptake at the anaerobic threshold (AT) and ventilatory efficiency (VE/VCO2 slope), or as a part of more comprehensive scores (i.e. Metabolic Exercise combined with Cardiac and Kidney Indexes, MECKI) is well established. Just few studies are available with respect a possible role of CPET in risk stratification of patients in HF with midrange EF (HFmrEF) subset, namely HF patients with LVEF between 40% and 49%.

Purpose

The aim of the present large Italian multicenter study was to characterize and to compare stable HFmrEF and HFrEF patients in terms of exercise capacity as well as of instrumental and laboratory variables. We analyzed a possible independent and incremental prognostic value of CPET parameters in identifying those HFmrEF patients at high cardiovascular death risk.

Methods

We retrospectively analyzed clinical and CPET data of stable HF patients with HFrEF and HFmrEF from the MECKI Score database. Five-thousand-seven-hundred-eleven patients, 4,535 with HFrEF and 1,176 with HFmrEF, were considered for the study. The end-point was cardiovascular death at 5 years. The median follow-up was 1343 days (25th–75th range, 627–2403 days).

Results

Cardiovascular death occurred in 552 HFrEF (12.2% event rate) and 61 HFmrEF (5.2% event rate) patients. At multivariate analysis, an independent role of variables included in the MECKI score (age, atrial fibrillation, LVEF, haemoglobin, sodium, MDRD, AT identification, VO2 at AT, peak VO2 also expressed as percentage of the maximum predicted, VE/VCO2 slope) was confirmed in HFrEF group (C-index=0.744) whereas, in the HFmrEF group, only age and peak VO2 remained outcome predictors (C-index=0.745).

We identified a peak VO2 <55% of predicted and a VE/VCO2 slope >31 as the most accurate cut-off values able to identify a HFmrEF subgroup with a cardiovascular mortality rate significantly higher than the overall HFmrEF (5.2% vs 8.5%) (Figure 1). By using both cut-off values contextually, we recognized a relatively small HFmrEF population with a cardiovascular risk quite similar to the HFrEF sample (11.4% vs 12.2%) (Figure 1).

Conclusions

Present data support the CPET as a useful tool in the HFmrEF management. Besides the peak VO2, which resulted as a strong independent outcome predictor, also a number of other CPET variables were associated to the cardiovascular death risk. Particularly, a peak VO2 ≤55% of the maximum and a VE/VCO2 slope ≥31 identified a HFmrEF subgroup of patients with a high cardiovascular death risk, similar to the one observed in the HFrEF group.

Funding Acknowledgement

Type of funding sources: None. Figure 1

Insights from cardiopulmonary exercise testing in pediatric patients with hypertrophic cardiomyopathy

Background

Hypertrophic cardiomyopathy (HCM) is characterized by extremely varied phenotypic expression ranging from asymptomatic to heart failure (HF) to sudden cardiac death (SCD). Although children with HCM are considered in the highest risk spectrum, the most common recommendations on pharmacological and non-pharmacological treatment (i.e. drugs, ICD, septal reduction procedures, inclusion in cardiac transplantation list) are often disregarded or too much postponed in this setting and strong evidence-based risk prediction models are missing. A systematic cardiopulmonary exercise test (CPET) assessment might be helpful to disclose an unsuspected functional limitation.

Purpose

The aim of our multicenter retrospective study was to investigate possible clinical insights, in terms of functional and prognostic assessment, coming from a full CPET assessment in a cohort of pediatric HCM outpatients aged less than 18 years old.

Methods

Sixty consecutive pediatric HCM outpatients aged <18 years-old were enrolled, each of them undergoing a full clinical assessment including a CPET; a group of 60 healthy subjects served as controls. An unique composite end-point of HF-related and SCD or SCD-equivalent events was also explored. During a median follow-up of 53 months, a total of 13 HF- and 7 SCD-related first events were collected.

Results

An impaired exercise capacity, consisting on peak VO2 values <80% of the predicted, has been found in the 78% of the study sample (n. 47 patients). Despite most of the HCM patients were classified in NYHA I functional class, most of them (n. 33, 73%) showed a reduced exercise capacity, the percentage of impaired exercise capacity raising in the NYHA II group (n. 14 patients, 93%).

Respect to the control Group, the HCM patients showed a significantly poorer functional status in terms of maximum workload achieved, peak VO2 (regardless the adopted correction), circulatory power and VE/VCO2 slope values (Figure 1, panel A).

HCM patients who experience adverse events during the follow-up (Event Group) showed the worst CPET profile (Figure 1, panel B).

The composite end-point occurred more frequently in patients with the worst CPETs' profiles. At the univariate analysis, peak VO2% was the variable with the strongest association with adverse events at follow-up (C-index=0.72, p=0.025) and a cut-off value equal to 60% was the most accurate in identifying those patients at the highest risk (Figure 2).

Conclusions

Our findings support the role of CPET analysis as an insightful approach in the young HCM clinical management. In a group of young asymptomatic or slightly symptomatic HCM patients, the CPET allowed us to estimate accurately their functional capacity and to disclose a portion of un-recognized exercise impairment. Our data argue in favor of a possible role of some CPET-derived variables in the early identification of those young HCM patients at highest risk of HCM related events.

Funding Acknowledgement

Type of funding sources: None. Figure 1Figure 2