Cardiorespiratory optimal point during exercise testing and sudden cardiac death: A prospective cohort study

(Non)-Exertional Variables of Cardiopulmonary Exercise Testing in Heart Failure with and Without Cardiac Amyloidosis

PURPOSE OF REVIEW

Cardiac amyloidosis (CA) constitutes an important etiology of heart failure with preserved ejection fraction (HFpEF) or heart failure with mildly reduced ejection fraction (HFmrEF). Since patients with CA show early exhaustion, we aimed to investigate whether non-exertional variables of cardiopulmonary exercise testing (CPET) provide additional information in comparison to traditional peak oxygen consumption (VO2peak).

RECENT FINDINGS

We retrospectively investigated CPET variables of patients with HFpEF and HFmrEF with (n = 21) and without (n = 21, HF) CA at comparable age and ejection fraction. Exertional and non-exertional CPET variables as well as laboratory and echocardiographic markers were analyzed. The primary outcome was the difference in CPET variables between groups. The secondary outcome was rehospitalization in patients with CA during a follow-up of 24 months. Correlations between CPET, NTproBNP, and echocardiographic variables were calculated to detect patterns of discrimination between the groups. HF patients with CA were inferior to controls in most exertional and non-exertional CPET variables. Patients with CA were hospitalized more often (p = 0.002), and rehospitalization was associated with VE/VCO2 (p = 0.019), peak oxygen pulse (p = 0.042), the oxygen equivalent at the first ventilatory threshold (p = 0.003), circulatory (p = 0.024), and ventilatory power (p < .001), but not VO2peak (p = 0.127). Higher performance was correlated with lower E/e' and NTproBNP as well as higher resting heart rate and stroke volume in CA. Patients with CA displayed worse non-exertional CPET performance compared to non-CA HF patients, which was associated with rehospitalization. Differences between correlations of resting echocardiography and CPET variables between groups emphasize different properties of exercise physiology despite comparable ejection fraction.

Cardiorespiratory optimal point in post-COVID-19 patients: a cross-sectional study

The varied clinical presentations of SARS-CoV-2 infection have raised concerns about long-term consequences, especially "long-COVID" or "post-COVID-19 syndrome." In this context, the cardiorespiratory optimal point (COP) within the Cardiopulmonary Exercise Test (CPET) emerges as a crucial metric for evaluating functional capacities and detecting cardiovascular and pulmonary anomalies post-COVID-19. This study aimed to assess COP values among post-COVID-19 patients and categorized them based on the initial severity of their disease. In this cross-sectional study conducted in the Northeast Brazil, 80 patients (26 females and 54 males) previously infected with SARS-CoV-2 underwent CPET. We clinically stratified patients into mild, moderate, or severe COVID-19 categories and assessed COP values and other cardiorespiratory metrics. We found differences in the predicted COP between patients with mild and severe COVID-19 (p=0.042). Additionally, patients with moderate and severe COVID-19 record had an average COP value exceeding 22. Other parameters, including respiratory exchange ratio, heart rate, and oxygen uptake efficiency slope, did not differ across the groups. Patients with a history of severe COVID-19 showed altered COP values, suggesting potential discrepancies in cardiovascular and respiratory system integration. The outcomes emphasize the importance of continuous monitoring and assessment of the cardiorespiratory domain for post-COVID-19 patients. Further research is needed to understand the relationship between elevated COP in post-severe COVID-19 and its long-term prognostic implications.

Association between Serum Testosterone and Aortic Valve Stenosis: A Prospective Cohort Study

Serum testosterone is associated with atherosclerotic cardiovascular disease, which shares risk factors with aortic stenosis (AS). The association between serum testosterone and AS has not been previously investigated. We aimed to assess the prospective association between serum testosterone and risk of AS. Serum testosterone was determined at baseline using a radioimmunoassay kit in 2577 men aged 42-61 years recruited into the Kuopio Ischemic Heart Disease prospective cohort study. Hazard ratios (HRs) with 95% confidence intervals (Cis) were estimated for AS. After a median follow-up of 27.2 years, 119 cases of AS were recorded. The risk of AS increased continuously with increasing serum testosterone across the range 25-39 nmol/L (p-value for nonlinearity = 0.49). In an analysis adjusted for age, body mass index, systolic blood pressure, total cholesterol, high-density lipoprotein cholesterol, smoking status, history of type 2 diabetes, history of coronary heart disease, and alcohol consumption, the HR (95% CI) for AS was 1.39 (1.10-1.76) per 10 nmol/L increase in serum testosterone. When alcohol consumption was replaced with physical activity, the HR (95% CI) was 1.38 (1.09-1.74). Comparing the bottom versus top third of serum testosterone, the corresponding (adjusted) risk estimates were 1.76 (1.11-2.81) and 1.76 (1.10-2.80), respectively. In middle-aged and older Finnish men, elevated levels of serum testosterone were associated with an increased risk of AS. Further research is needed to replicate these findings and assess any potential relevance of serum testosterone in AS prevention.

The cardiorespiratory optimal point as a discriminator of lesion severity in adults with congenital heart disease

BACKGROUND

Peak oxygen consumption (VO2peak), which depends on maximal exertion and is reduced in adults with congenital heart disease (ACHD), is associated with lesion severity. The lowest ventilatory equivalent for oxygen (the minimum value of VE/VO2) reflects the cardiorespiratory optimal point (COP) as best possible respiration-circulatory interaction and may discriminate between lesion types without the need for maximal exertion. However, data on COP in ACHD is scarce.

METHODS

We retrospectively analyzed stable ACHD with moderate (N.=13) and severe lesions (N.=17) reporting to our outpatient clinic undergoing cardiopulmonary exercise testing. The primary outcome of the study was the difference of COP between moderate and severe lesions. Secondary outcomes were between group differences of the submaximal variable exercise oxygen uptake efficiency slope (OUES) and peak O2 pulse (O2pulsemax) as a surrogate for peripheral oxygen extraction and stroke volume increase during exercise.

RESULTS

The group of severe lesions displayed higher COP (29.5±7.0 vs. 25.2±6.2, P=0.028) as well as lower O2pulsemax (13.3±8.4 vs. 14.9±3.4 mL/beat/kg 102, P=0.038). VO2peak (17.4±6.5 vs. 20.8±8.5 mL/kg/min, P=0.286) and OUES (1.5±0.7 vs. 1.8±0.9, P=0.613) showed a trend towards lower values in severe lesions. COP was a better between group discriminator than O2pulsemax (area under the curve 73.8% vs. 72.4%).

CONCLUSIONS

As a submaximal variable, COP discriminated between moderate and severe lesions and may prove beneficial in a highly vulnerable population that is often unable to undergo exertional testing.

Cardiopulmonary Profiling of Athletes with Post-Exertional Malaise after COVID-19 Infection-A Single-Center Experience

(1) Background: Cardiopulmonary exercise testing (CPET) has been suggested by the European Society of Cardiology (ESC) for assessing the exercise limitations of apparently healthy individuals, but data on elite athletes regarding this test are scarce. (2) Methods: We analyzed CPET in elite (n = 43, 21.9 ± 3.7 years) and recreational (n = 40, 34.7 ± 13.0 years) athletes with persistent subjective exercise intolerance and post-exertional malaise (PEM) after COVID-19 infection. The primary outcome was the point prevalence of the adequate cardiopulmonary response (ACPR), defined by the presence of all of the following ESC criteria for apparently healthy individuals: (1) >100% of predicted peak oxygen consumption (predVO2peak), (2) VE/VCO2 < 30, (3) no exercise oscillatory ventilation (EOV), and (4) heart rate recovery of ≥12 beats/minute 1 min after exercise termination (HRR1). Results: ACPR occurred more frequently in elite athletes than in recreational athletes (70.0% vs. 39.5%; p = 0.005), mainly driven by the lower VE/VCO2 (<30: 97.7% vs. 65%, p < 0.001). Elite (11.6%) and recreational athletes (22.5%) showing a plateau of O2 pulse did not display ACPR. Conclusions: ACPR was not observed in all recreational and elite athletes with PEM. In particular, perturbed VE/VCO2 and the plateauing of O2 pulse are suitable for quantifying exercise limitations and may identify a high-risk population with long-COVID-19 syndrome who require their training intensities to be adapted.

Cardiorespiratory Fitness and Risk of Aortic Stenosis (from a Prospective Cohort Analysis)

Cardiorespiratory fitness (CRF) is a major risk factor and predictor of atherosclerotic cardiovascular disease. However, the relationship between CRF and risk of aortic stenosis (AS) has not been previously investigated. Thus, we aimed to assess the prospective association between CRF and risk of AS. CRF, as measured by maximal oxygen uptake, was assessed using a respiratory gas exchange analyzer during cardiopulmonary exercise testing in 2,308 men aged 42 to 61 years recruited into the Kuopio Ischemic Heart Disease prospective cohort study. Hazard ratios (HRs) with 95% confidence intervals (CIs) were estimated for AS. During a median follow-up of 27 years, 101 cases of AS occurred. Dose-response analysis suggested there might be a nonlinear relation between CRF levels and AS risk. In an analysis adjusted for age, body mass index, systolic blood pressure, total cholesterol, high-density lipoprotein cholesterol, smoking, history of type 2 diabetes mellitus, and coronary heart disease, the HRs 95% (CIs) of AS were 0.57 (0.34 to 0.96) and 0.91 (0.53 to 1.57) for participants in the middle and upper third of CRF levels, respectively, compared with participants in the bottom third. After further adjustment for alcohol consumption, the corresponding HRs (95% CIs) were 0.58 (0.34 to 0.97) and 0.91 (0.53 to 1.56), respectively. In conclusion, higher CRF levels may be associated with a lower incidence of AS in middle-aged and older Finnish men. Given the likely limitations of low statistical power, further research is needed to provide insights into the dose-response nature of any relationship between CRF and AS.

Increased Dead Space Ventilation as a Contributing Factor to Persistent Exercise Limitation in Patients with a Left Ventricular Assist Device

(1) Background: The exercise capacity of patients with a left ventricular assist device (LVAD) remains limited despite mechanical support. Higher dead space ventilation (VD/VT) may be a surrogate for right ventricular to pulmonary artery uncoupling (RV-PA) during cardiopulmonary exercise testing (CPET) to explain persistent exercise limitations. (2) Methods: We investigated 197 patients with heart failure and reduced ejection fraction with (n = 89) and without (HFrEF, n = 108) LVAD. As a primary outcome NTproBNP, CPET, and echocardiographic variables were analyzed for their potential to discriminate between HFrEF and LVAD. As a secondary outcome CPET variables were evaluated for a composite of hospitalization due to worsening heart failure and overall mortality over 22 months. (3) Results: NTproBNP (OR 0.6315, 0.5037-0.7647) and RV function (OR 0.45, 0.34-0.56) discriminated between LVAD and HFrEF. The rise of endtidal CO2 (OR 4.25, 1.31-15.81) and VD/VT (OR 1.23, 1.10-1.40) were higher in LVAD patients. Group (OR 2.01, 1.07-3.85), VE/VCO2 (OR 1.04, 1.00-1.08), and ventilatory power (OR 0.74, 0.55-0.98) were best associated with rehospitalization and mortality. (4) Conclusions: LVAD patients displayed higher VD/VT compared to HFrEF. Higher VD/VT as a surrogate for RV-PA uncoupling could be another marker of persistent exercise limitations in LVAD patients.

Haemodynamic Gain Index Is Associated with Risk of Sudden Cardiac Death and Improves Risk Prediction: A Cohort Study

INTRODUCTION

Haemodynamic gain index (HGI) is a novel haemodynamic parameter which can be obtained from cardiopulmonary exercise testing (CPX), but its association with sudden cardiac death (SCD) is not known. We aimed to assess the association of HGI with SCD risk in a long-term prospective cohort study.

METHODS

HGI was calculated using heart rate and systolic blood pressure (SBP) responses measured in 1897 men aged 42–61 years during CPX from rest to peak exercise. Cardiorespiratory fitness (CRF) was measured using respiratory gas exchange analysis. Multivariable adjusted hazard ratios (HRs) (95% confidence intervals [CIs]) were estimated for SCD.

RESULTS

During a median follow-up of 28.7 years, 205 SCDs occurred. The risk of SCD decreased gradually with increasing HGI (p value for non-linearity = 0.63). A unit (bpm/mm Hg) higher HGI was associated with a decreased risk of SCD (HR: 0.84; 95% CI: 0.71-0.99), which was attenuated following adjustment for CRF. CRF was inversely associated with SCD, which remained after further adjustment for HGI (HR: 0.85; 95% CI: 0.77-0.94) per each unit higher CRF. Addition of HGI to a SCD risk prediction model containing established risk factors improved risk discrimination (C-index change = 0.0096; p = 0.017) and reclassification (net reclassification improvement [NRI] = 39.40%, p = 0.001). The corresponding values for CRF were (C-index change = 0.0178; p = 0.007) and (NRI = 43.79%, p = 0.001).

CONCLUSION

Higher HGI during CPX is associated with a lower SCD risk, consistent with a dose-response relationship but dependent on CRF levels. Though HGI significantly improves the prediction and classification of SCD beyond common cardiovascular risk factors, CRF remains a stronger risk indicator and predictor of SCD compared to HGI.

Heart failure classification based on resting ejection fraction does not display a unique exercise response pattern

BACKGROUND

Heart failure with preserved (HFpEF), mildly reduced (HFmrEF) and reduced (HFrEF) ejection fraction (EF) remains a controversial categorization. Whether these three categories reflect a distinct pattern of exercise limitation in cardiopulmonary exercise testing (CPET) needs to be investigated. We aimed to analyze whether CPET variables differ between all heart failure categories (HF).

METHODS

We analyzed CPET variables of stable HFpEF (n = 123), HFmrEF (n = 31), and HFrEF (n = 153; 74 patients with and 79 patients without left ventricular assist device, LVAD) patients. The association between HF and peak oxygen consumption (VO_2peak) was used as a primary outcome, while the association between HF, oxygen uptake efficiency slope (OUES), and increase of O₂ pulse (ΔO₂ pulse) were analyzed as secondary outcomes.

RESULTS

VO_2peak displayed a consistent decline across all HF categories (19.8 ml ± 6.2/kg/min vs. 17.5 ± 7.9 ml/kg/min vs. 13.7 ± 4.0 ml/kg/min, p < 0.001). OUES only showed differences between HFpEF and HFrEF (1.8 ± 0.6 vs. 1.4 ± 0.5, p < 0.001) as well as HFmrEF and HFrEF (1.9 ± 0.9 vs. 1.4 ± 0.5, p = 0.004). ΔO₂ pulse differed between HFpEF and HFrEF (7.7 ± 3.5 ml/beat/kg*100 vs. 5.5 ± 3.0 ml/beat/kg*100, p < 0.001) as well as HFpEF and HFmrEF (7.7 ± 3.5 ml/beat/kg*100 vs. 6.3 ± 4.1 ml/beat/kg*100, p = 0.049). Outcome variables did not differ between HFrEF with and without LVAD support (VO_2peak: p = 0.364, OUES: p = 0.129, ΔO₂ pulse: p = 0.564).

CONCLUSIONS

HF did not display a distinct CPET profile. Thus, EF-based categorization does not entirely reflect exercise limitations. CPET variables could contribute to better characterize HF phenotypes.

Betablockers reduce oxygen pulse increase and performance in heart failure patients with preserved ejection fraction

BACKGROUND

Beta blockers (BB) reduce chronotropic response and exercise capacity in heart failure with preserved ejection fraction (HFpEF). To analyze the influence of BB on exercise performance and O 2 pulse increase as a surrogate for stroke volume in HFpEF.

METHODS

We retrospectively analyzed the influence of BB intake (yes: n = 48/no: n = 51) on peak oxygen uptake (VO 2peak), oxygen uptake efficiency slope (OUES), and increase of O 2 pulse in HFpEF patients undergoing cardiopulmonary exercise testing (CPET). Associations of outcome variables and risk category of the algorithm of the Heart Failure Association of the European Society of Cardiology (HFA-PEFF score) were calculated.

RESULTS

Patients on BB showed lower VO 2peak (p = .003) and OUES (p = .002), with a dominant effect in the high-risk (p = .020; 0.002), but not in the low risk-group (p = .434; p = .499). In the intermediate group BB showed a trend towards lower VO 2peak (p = .078) and lower values for OUES (p = .020). Patients on BB also demonstrated a lower increase of O 2 pulse during exercise (p = .002), without differences between HFA-PEFF risk groups (low: p = .322, intermediate: p = .269, high: p = .313).

CONCLUSIONS

BB reduce exercise capacity and O 2 pulse increase in HFpEF patients. Direct quantification of O 2 pulse increase may help to improve the discrimination of HFpEF patients.

Cardiorespiratory Optimal Point Is a Submaximal Exercise Test Variable and a Predictor of Mortality Risk: THE BALL STATE ADULT FITNESS LONGITUDINAL LIFESTYLE STUDY (BALL ST)

PURPOSE

The cardiorespiratory optimal point (COP) is the minimum ventilatory equivalent for oxygen. The COP can be determined during a submaximal incremental exercise test. Reflecting the optimal interaction between the respiratory and cardiovascular systems, COP may have prognostic utility. The aim of this investigation was to determine the relationship between COP and all-cause mortality in a cohort of apparently healthy adults.

METHODS

The sample included 3160 apparently healthy adults (46% females) with a mean age of 44.0 ± 12.5 yr who performed a cardiopulmonary exercise test. Cox proportional hazards models were performed to assess the relationship between COP and mortality risk. Prognostic peak oxygen uptake (V˙ o2peak ) and COP models were compared using the concordance index.

RESULTS

There were 558 deaths (31% females) over a follow-up period of 23.0 ± 11.9 yr. For males, all Cox proportional hazards models, including the model adjusted for traditional risk factors and V˙ o2peak , had a positive association with risk for mortality ( P < .05). For females, only the unadjusted COP model was associated with risk for mortality ( P < .05). The concordance index values indicated that unadjusted COP models had lower discrimination compared with unadjusted V˙ o2peak models ( P < .05) and V˙ o2peak did not complement COP models ( P ≥ .13).

CONCLUSIONS

Cardiorespiratory optimal point is related to all-cause mortality in males but not females. These findings suggest that a determination of COP can have prognostic utility in apparently healthy males aged 18-85 yr, which may be relevant when a maximal exercise test is not feasible or desirable.