Peak oxygen uptake in heart failure: Look behind the number!

Cardiopulmonary Exercise Testing in Children and Young Adolescents after a Multisystem Inflammatory Syndrome: Physical Deconditioning or Residual Pathology?

Multisystem inflammatory syndrome in children (MIS-C) is a serious health condition that imposes a long-term follow-up. The purpose of our pilot study is to evaluate the usefulness of the cardiopulmonary stress test (CPET) in the follow-up after MIS-C. All patients admitted for MIS-C in our hospital in the 12 months preceding the date of observation were considered for inclusion in the study. Pre-existing cardio-respiratory diseases and/or the lack of collaboration were the exclusion criteria. At enrolment, each subject passed a cardiological examination, rest ECG, echocardiogram, 24 h Holter-ECG, blood tests, and a CPET complete of spirometry. A total of 20 patients met the inclusion criteria (11.76 ± 3.29 years, 13 male). In contrast to the normality of all second-level investigations, CPET showed lower-than-expected peakVO₂ and peak-oxygen-pulse values (50% of cases) and higher-than-expected VE/VCO_2-slope values (95% of cases). A statistically significant inverse correlation was observed between P-reactive-protein values at admission and peakVO₂/kg values (p = 0.034), uric acid values at admission, and peakVO₂ (p = 0.011) or peak-oxygen-pulse expressed as a percentage of predicted (p = 0.021), NT-proBNP values at admission and peakVO₂ expressed as a percentage of predicted (p = 0.046). After MIS-C (4-12 months) relevant anomalies can be observed at CPET, which can be a valuable tool in the follow-up after this condition.

Insights from Cardiopulmonary Exercise Testing in Pediatric Patients with Hypertrophic Cardiomyopathy

The usefulness of cardiopulmonary exercise test (CPET) in adult hypertrophic cardiomyopathy (HCM) patients is well-known, whereas its role in pediatric HCM patients has not yet been explored. The present study investigates possible insights from a CPET assessment in a cohort of pediatric HCM outpatients in terms of functional and prognostic assessment. 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. A unique composite end-point of heart failure (HF) related and sudden cardiac death (SCD) or SCD-equivalent events was also explored. During a median follow-up of 53 months (25th–75th: 13–84 months), a total of 13 HF- and 7 SCD-related first events were collected. Compared to controls, HCM patients showed an impaired functional capacity with most of them showing peak oxygen uptake (pVO₂) values of <80% of the predicted, clearly discrepant with functional New York Heart Association class assessment. The composite end-point occurred more frequently in patients with the worst CPETs’ profiles. At the univariate analysis, pVO₂% 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. In a pediatric HCM subset, the CPET assessment allows a true functional capacity estimation and it might be helpful in identifying early those patients at high risk of events.

Risk stratification in heart failure with mild reduced ejection fraction

Heart failure with mid-range ejection fraction represents a heterogeneous and relatively young heart failure category accounting for nearly 20-30% of the overall heart failure population. Due to its complex phenotype, a reliable clinical picture of heart failure with mid-range ejection fraction patients as well as a definite risk stratification are still relevant unsolved issues. In such a context, there is growing interest in a comprehensive functional assessment by means of a cardiopulmonary exercise test, yet considered a cornerstone in the clinical management of patients with heart failure and reduced ejection fraction. Indeed, the cardiopulmonary exercise test has also been found to be particularly useful in the heart failure with mid-range ejection fraction category, several cardiopulmonary exercise test-derived parameters being associated with a poor outcome. In particular, a recent contribution by the metabolic exercise combined with cardiac and kidney indexes research group showed an independent association between the peak oxygen uptake and pure cardiovascular mortality in a large cohort of recovered heart failure with mid-range ejection fraction patients. Contextually, the same study supplied an easy approach to identify a high-risk heart failure with mid-range ejection fraction subset by using a combination of peak oxygen uptake and ventilatory efficiency cut-off values, namely 55% of the maximum predicted and 31, respectively. Thus, looking at the above-mentioned promising results and waiting for specific trials, it is reasonable to consider cardiopulmonary exercise test assessment as part of the heart failure with mid-range ejection fraction work-up in order to identify those patients with an unfavourable functional profile who probably deserve a close clinical follow-up and, probably, more aggressive therapeutic strategies.

Risk Stratification in Hypertrophic Cardiomyopathy. Insights from Genetic Analysis and Cardiopulmonary Exercise Testing

The role of genetic testing over the clinical and functional variables, including data from the cardiopulmonary exercise test (CPET), in the hypertrophic cardiomyopathy (HCM) risk stratification remains unclear. A retrospective genotype–phenotype correlation was performed to analyze possible differences between patients with and without likely pathogenic/pathogenic (LP/P) variants. A total of 371 HCM patients were screened at least for the main sarcomeric genes MYBPC3 (myosin binding protein C), MYH7 (β-myosin heavy chain), TNNI3 (cardiac troponin I) and TNNT2 (cardiac troponin T): 203 patients had at least an LP/P variant, 23 patients had a unique variant of uncertain significance (VUS) and 145 did not show any LP/P variant or VUS. During a median 5.4 years follow-up, 51 and 14 patients developed heart failure (HF) and sudden cardiac death (SCD) or SCD-equivalents events, respectively. The LP/P variant was associated with a more aggressive HCM phenotype. However, left atrial diameter (LAd), circulatory power (peak oxygen uptake*peak systolic blood pressure, CP%) and ventilatory efficiency (C-index = 0.839) were the only independent predictors of HF whereas only LAd and CP% were predictors of the SCD end-point (C-index = 0.738). The present study reaffirms the pivotal role of the clinical variables and, particularly of those CPET-derived, in the HCM risk stratification.

Cardiovascular Death Risk in Recovered Mid-Range Ejection Fraction Heart Failure: Insights From Cardiopulmonary Exercise Test

BACKGROUND

Heart failure with midrange ejection fraction (HFmrEF) represents a heterogeneous category where phenotype, as well as prognostic assessment, remains debated. The present study explores a specific HFmrEF subset, namely those who recovered from a reduced EF (rec-HFmrEF) and, particularly, it focuses on the possible additive prognostic role of cardiopulmonary exercise testing.

METHODS AND RESULTS

We analyzed data from 4535 patients with HFrEF and 1176 patients with rec-HFmrEF from the Metabolic Exercise combined with Cardiac and Kidney Indexes database. The end point was cardiovascular death at 5 years. The median follow-up was 1343 days (25th-75th range 627-2403 days). Cardiovascular death occurred in 552 HFrEF and 61 rec-HFmrEF patients. The multivariate analysis confirmed an independent role of the MECKI score's variables in HFrEF (C-index = 0.744) whereas, in the rec-HFmrEF group, only age and peak oxygen uptake (pVO₂) remained associated to the end point (C-index = 0.745). A peak oxygen uptake of ≤55% of predicted and a ventilatory efficiency of ≥31 resulted as the most accurate cut-off values in the outcome prediction.

CONCLUSIONS

Present data support the cardiopulmonary exercise test and, particularly, the peak oxygen uptake, as a useful tool in the rec-HFmrEF prognostic assessment. A peak VO₂ of ≤55% predicted and ventilatory efficiency of ≥31 might help to identify a high-risk rec-HFmrEF subgroup.