Ventilatory and heart rate responses to exercise : better predictors of heart failure mortality than peak oxygen consumption

Prognostic value of heart rate and oxygen pulse response in heart failure with left ventricular ejection fraction over 40

BACKGROUNDS

Heart rate (HR) and stroke volume (SV)-the components of cardiac output-have a complementary relationship. Poor HR increase during exercise is associated with poor exercise tolerance in heart failure (HF) with preserved ejection fraction (HFpEF), but its prognostic impact remains unclear. Furthermore, whether the compensation for poor HR increase with SV during exercise is associated with prognosis remains unknown.

METHODS

We evaluated 129 consecutive hospitalized HF patients with sinus rhythm and left ventricular ejection fractions > 40% who underwent cardiopulmonary exercise testing before discharge from the index hospitalization.

RESULTS

Patients (age: 66 [55-74] years; 73% male) were divided into four groups by median HR reserve (HRR; peak-rest HR: 34 bpm) and O2 pulse, a surrogate for SV, reserve (peak-rest O2 pulse: 4.8 mL/beat). During a mean follow-up of 562 [294-961] days, cardiovascular events (cardiovascular death and/or HF rehospitalizations) occurred in 24 patients. Kaplan-Meier analysis identified significant differences in outcomes among the four groups (χ2 = 27.3, p < 0.001). Using the preserved HRR/preserved O2 pulse reserve group (n = 33) as a reference, the impaired HRR/impaired O2 pulse reserve group (n = 37) was associated with poor outcomes (adjusted hazard ratio: 5.66, 95% CI 1.15-27.74, p = 0.033), whereas the impaired HRR/preserved O2 pulse reserve group (n = 31) was not (adjusted hazard ratio: 0.38, 95% CI 0.03 to 4.76, p = 0.455).

CONCLUSION

The overlap of lower increases in HR and O2 pulse, a surrogate for SV, during exercise was associated with an extremely poor prognosis in HFpEF.

Predictive Value of V̇O 2peak in Adult Congenital Heart Disease in Comparison with Heart Failure with Reduced Ejection Fraction

BACKGROUND

Peak oxygen consumption (V̇O 2peak ) is used to predict outcomes and the timing of transplantation in patients with heart failure with reduced ejection fraction (HFrEF); V̇O 2peak also has predictive utility in patients with adult congenital heart disease (ACHD). However, the predictive value of a given V̇O 2peak in patients with ACHD compared to those with HFrEF, especially after adjustment for age and sex, is not clear.

METHODS

To address this, we performed a longitudinal cohort study comparing patients with ACHD to patients with HFrEF. The ACHD and HFrEF cohorts were matched for sex and age (+/- 10 y). V̇O 2peak tests were conducted between 1993 and 2012. Events were defined as death, cardiac transplantation, or left ventricular assist device placement. Outcome data were obtained via electronic medical record, Social Security Death Index, and phone interview. Cox proportional-hazard regressions were used to evaluate relationships of event-free survival with predictor variables.

RESULTS

Patients with ACHD (N=137) and HFrEF (N=137) with a median follow-up time of 14.5 (13.4-15.6) y in the ACHD cohort and 19 (14.8-21.1) y in the HFrEF cohort. Higher V̇O 2peak was associated with lower risk for a cardiac outcome, independent of age and sex, in both ACHD (HR 0.89, 95% CI 0.83-0.96, P =0.002) and HFrEF (HR 0.85, 95% CI 0.81-0.89, P <0.001Male sex was associated with greater risk of a cardiac outcome ( P =0.001) in ACHD (HR 3.34) and HFrEF (HR 1.83). After multivariable adjustment (that included age, sex, and V̇O 2peak ) having ACHD conferred a 66% lower risk of a cardiovascular event compared to a HFrEF diagnosis (HR 0.34, 95% CI 0.22-0.53, P <0.001).

CONCLUSIONS

V̇O 2peak independently predicts event-free survival among adults with ACHD or HFrEF and has clinical utility in the outpatient setting. Patients with ACHD, however, have a better prognosis for any given V̇O 2peak compared to those with HFrEF.

WHAT IS NEW?

In an age- and sex-matched longitudinal cohort study with over 7 y of follow-up, adults with congenital heart disease (ACHD) were found to have a better event-free (no transplant or LVAD) survival than adults with heart failure with reduced ejection fraction (HFrEF) even after multivariable adjustment that included age, sex, and V̇O 2peak . Thus, for any given V̇O 2peak a better event-free survival would be expected in ACHD compared with HFrEF. For both groups, a higher V̇O 2peak did still confer an improved event-free survival and male sex conferred a worse event-free survival.

WHAT ARE THE CLINICAL IMPLICATIONS?

Patients with HFrEF commonly undergo V̇O 2peak testing to evaluate clinical status, exercise capabilities, and timing for transplantation. Less commonly, patients with ACHD undergo V̇O 2peak testing. This study confirmed that a higher V̇O 2peak is still an excellent predictor of freedom from cardiac events and survival in both groups; however, for a given V̇O 2peak , a patient with ACHD would be expected to have a markedly improved event-free survival vs. a patient with HFrEF even after adjusting for age and sex. Moreover, our analysis adds to the understanding of how much of an advantage a higher V̇O 2peak confers for each mL·min -1 ·kg -1 confers in each group, with a slightly greater incremental benefit for the ACHD group. This finding has implications for timing of referral to cardiac transplantation for patients with ACHD. Future studies are needed to determine the optimal V̇O 2peak cut-off for transplantation for those with ACHD. Furthermore, more studies are needed to investigate the potential mechanism(s) for the ACHD survival advantage.

International Society for Heart and Lung Transplantation Guidelines for the Evaluation and Care of Cardiac Transplant Candidates-2024

The "International Society for Heart and Lung Transplantation Guidelines for the Evaluation and Care of Cardiac Transplant Candidates-2024" updates and replaces the "Listing Criteria for Heart Transplantation: International Society for Heart and Lung Transplantation Guidelines for the Care of Cardiac Transplant Candidates-2006" and the "2016 International Society for Heart Lung Transplantation Listing Criteria for Heart Transplantation: A 10-year Update." The document aims to provide tools to help integrate the numerous variables involved in evaluating patients for transplantation, emphasizing updating the collaborative treatment while waiting for a transplant. There have been significant practice-changing developments in the care of heart transplant recipients since the publication of the International Society for Heart and Lung Transplantation (ISHLT) guidelines in 2006 and the 10-year update in 2016. The changes pertain to 3 aspects of heart transplantation: (1) patient selection criteria, (2) care of selected patient populations, and (3) durable mechanical support. To address these issues, 3 task forces were assembled. Each task force was cochaired by a pediatric heart transplant physician with the specific mandate to highlight issues unique to the pediatric heart transplant population and ensure their adequate representation. This guideline was harmonized with other ISHLT guidelines published through November 2023. The 2024 ISHLT guidelines for the evaluation and care of cardiac transplant candidates provide recommendations based on contemporary scientific evidence and patient management flow diagrams. The American College of Cardiology and American Heart Association modular knowledge chunk format has been implemented, allowing guideline information to be grouped into discrete packages (or modules) of information on a disease-specific topic or management issue. Aiming to improve the quality of care for heart transplant candidates, the recommendations present an evidence-based approach.

Blood pressure levels and adverse cardiovascular outcomes in heart failure: A systematic review and meta-analysis

AIM

Existing data on the association between blood pressure levels and adverse cardiovascular outcomes in patients with heart failure (HF) are inconsistent. The optimal blood pressure targets for patients with HF remain uncertain. This study sought to assess the associations between blood pressure (systolic [SBP] and diastolic blood pressure [DBP]) levels and adverse cardiovascular disease (CVD) outcomes in patients with HF.

METHODS AND RESULTS

A systematic review and meta-analysis were conducted using MEDLINE, Embase, the Cochrane Library, and Web of Science databases up to 5 May 2023. The outcomes of interest included adverse cardiovascular events and all-cause mortality. Pooled relative risks (RRs) with corresponding 95% confidence intervals (CIs) were calculated. Forty-three unique observational cohort studies, comprising 120 643 participants with HF, were included. The pooled RRs (95% CIs) for SBP thresholds of ≥140 mmHg versus <140 mmHg were 0.92 (0.83-1.01) for all-cause mortality, 0.83 (0.67-1.04) for CVD death, and 0.98 (0.80-1.21) for HF hospitalization. The pooled RR (95% CI) for SBP thresholds of ≥160 mmHg versus <160 mmHg and all-cause mortality was 0.67 (0.62-0.74). SBP levels below <130, <120, and <110 mmHg were each associated with an increased risk of various cardiovascular endpoints and all-cause mortality. The pooled RR (95% CI) for DBP thresholds of ≥80 mmHg versus <80 mmHg and all-cause mortality was 0.86 (0.67-1.10). A 10 mmHg increase in SBP or DBP was associated with a reduction in all-cause mortality and other cardiovascular endpoints.

CONCLUSIONS

The findings suggest that lower and normal baseline SBP levels (<130, <120, and <110 mmHg) may be associated with future risk of worse outcomes in patients with HF. Optimal baseline blood pressure levels for these patients may lie within the range of ≥140 mmHg for SBP. In the absence of observational studies with repeated blood pressure measurements or definitive trials evaluating optimal blood pressure targets, individualized blood pressure targets based on patients' unique circumstances are warranted in HF management.

Clinical and functional effects of beta-blocker therapy discontinuation in patients with biventricular heart failure

BACKGROUND

Nearly two-thirds of patients with heart failure with reduced ejection fraction (HFrEF) have right ventricular dysfunction, previously identified as an independent predictor of reduced functional capacity and poor prognosis. Beta-blocker therapy (β-BT) reduces mortality and hospitalizations in patients with HFrEF and is approved as first-line therapy regardless of concomitant right ventricular function. However, the exact role of sympathetic nervous system activation in right ventricular dysfunction and the potential usefulness (or harmfulness) of β-BT in these patients are still unclear.

OBJECTIVES

The aim of the study is to evaluate the medium-term effect of β-BT discontinuation on functional capacity and right ventricular remodelling based on cardiopulmonary exercise testing (CPET), echocardiography and serum biomarkers in patients with clinically stable biventricular dysfunction.

METHODS

In this single-centre, open-label, prospective trial, 16 patients were enrolled using the following criteria: patients were clinically stable without signs of peripheral congestion; NYHA II-III while on optimal medical therapy (including β-BT); LVEF 40% or less; echocardiographic criteria of right ventricular dysfunction. Patients were randomized 1 : 1 either to withdraw (group 0) or continue (group 1) β-BT. In group 0, optimal heart rate was obtained with alternative rate-control drugs. Echo and serum biomarkers were performed at baseline, after 3 and 6 months; CPET was performed at baseline and 6 months. Mann--Whitney U test was adopted to determine the relationships between β-BT discontinuation and effects on right ventricular dysfunction.

RESULTS

At 6 months' follow up, S' DTI improved (ΔS': 1.01 vs. -0.92 cm/s; P = 0.03), while estimated PAPs (ΔPAPs: 0.8 vs. -7.5 mmHg; P = 0.04) and echo left ventricular-remodelling (ΔEDVi: 19.55 vs. -0.96 ml/mq; P = 0.03) worsened in group 0. In absolute terms, the only variables significantly affected by β-BT withdrawal were left ventricular EDV and ESV, appearing worse in group 0 (mean EDVi 115 vs. 84 ml/mq; mean ESVi 79 vs. 53.9 ml/mq, P = 0.03). No significant changes in terms of functional capacity were observed after β-BT withdrawal.

CONCLUSION

In HFrEF patients with concomitant right ventricular dysfunction, β-BT discontinuation did not produce any beneficial effects. In addition, despite maintenance of optimal heart rate control, β-BT discontinuation induced worsening of left ventricular remodelling. Our study corroborates the hypothesis that improvement in left ventricular function may likewise be a major determinant for improvement in right ventricular function, reducing pulmonary wedge pressure and right ventricular afterload, with only a marginal action of its negative inotropic effect. In conclusion, β-BT appears beneficial also in heart failure patients with biventricular dysfunction.

Effects of Sacubitril/Valsartan on Exercise Capacity in Patients with Heart Failure with Reduced Ejection Fraction and the Role of Percentage of Delayed Enhancement Measured by Cardiac Magnetic Resonance in Predicting Therapeutic Response: A Multicentre Study

Background: This study aims to evaluate the cardiopulmonary effects of sacubitril/valsartan therapy in patients with heart failure with reduced ejection fraction (HFrEF), investigating a possible correlation with the degree of myocardial fibrosis, as assessed by cardiac magnetic resonance. Methods: A total of 134 outpatients with HFrEF were enrolled. Results: After a mean follow-up of 13.3 ± 6.6 months, an improvement in ejection fraction and a reduction in E/A ratio, inferior vena cava size and N-terminal pro-B-type natriuretic peptide levels were observed. At follow-up, we observed an increase in VO₂ peak of 16% (p<0.0001) and in O₂ pulse of 13% (p=0.0002) as well as an improvement in ventilatory response associated with a 7% reduction in the VE/VCO₂ slope (p=0.0001). An 8% increase in the ΔVO₂/Δ work ratio and an 18% increase in exercise tolerance were also observed. Multivariate logistic regression analysis showed that the main predictors of events during follow-up were VE/VCO₂ slope >34 (OR 3.98; 95% CI [1.59-10.54]; p=0.0028); ventilatory oscillatory pattern (OR 4.65; 95% CI [1.55-16.13]; p=0.0052); and haemoglobin level (OR 0.35; 95% CI [0.21-0.55]; p<0.0001). In patients who had cardiac magnetic resonance, when delayed enhancement >4.6% was detected, a lower response after sacubitril/valsartan therapy was observed as expressed by improvement in ΔVO₂ peak, O₂ pulse, LVEF and N-terminal pro-B-type natriuretic peptide. No significant differences were observed in ΔVO₂/Δ work and VE/VCO₂ slope. Conclusion:Sacubitril/valsartan improves cardiopulmonary functional capacity in HFrEF patients. The presence of myocardial fibrosis on cardiac magnetic resonance is a predictor of response to therapy.

Cardiopulmonary exercise testing for heart failure: pathophysiology and predictive markers

Despite the numerous recent advancements in therapy, heart failure (HF) remains a principle cause of both morbidity and mortality. HF with preserved ejection fraction (HFpEF), a condition that shares the prevalence and adverse outcomes of HF with reduced ejection fraction, remains poorly recognised in its initial manifestations. Cardiopulmonary exercise testing (CPET), defined as a progressive work exercise test that includes non-invasive continuous measurement of cardiovascular and respiratory parameters, provides a reliable mode to evaluate for early features and for the assessment of prognostic features of both forms of HF. While CPET measurements are standard of care for advanced HF and transplant programmes, they merit a broader clinical application in the early diagnosis and assessment of patients with HFpEF. In this review, we provide an overview of the pathophysiology of exercise intolerance in HF and discuss key findings in CPETs used to evaluate both severity of impairment and the prognostic implications.

Minute ventilation/carbon dioxide production in chronic heart failure

In chronic heart failure, minute ventilation (V'_E) for a given carbon dioxide production (V'_CO2 ) might be abnormally high during exercise due to increased dead space ventilation, lung stiffness, chemo- and metaboreflex sensitivity, early metabolic acidosis and abnormal pulmonary haemodynamics. The V'_E versus V'_CO2 relationship, analysed either as ratio or as slope, enables us to evaluate the causes and entity of the V'_E/perfusion mismatch. Moreover, the V'_E axis intercept, i.e. when V'_CO2 is extrapolated to 0, embeds information on exercise-induced dead space changes, while the analysis of end-tidal and arterial CO₂ pressures provides knowledge about reflex activities. The V'_E versus V'_CO2 relationship has a relevant prognostic power either alone or, better, when included within prognostic scores. The V'_E versus V'_CO2 slope is reported as an absolute number with a recognised cut-off prognostic value of 35, except for specific diseases such as hypertrophic cardiomyopathy and idiopathic cardiomyopathy, where a lower cut-off has been suggested. However, nowadays, it is more appropriate to report V'_E versus V'_CO2 slope as percentage of the predicted value, due to age and gender interferences. Relevant attention is needed in V'_E versus V'_CO2 analysis in the presence of heart failure comorbidities. Finally, V'_E versus V'_CO2 abnormalities are relevant targets for treatment in heart failure.

Heart Failure With Preserved Ejection Fraction vs. Reduced Ejection Fraction - Mechanisms of Ventilatory Inefficiency During Exercise in Heart Failure

Background: Ventilatory inefficiency during exercise assessed using the lowest minute ventilation/carbon dioxide production (V̇E/V̇CO₂) ratio was recently proven to be a strong prognostic marker of heart failure (HF) regardless of left ventricular ejection fraction (LVEF). Its physiological background, however, has not been elucidated. Methods and Results: Fifty-seven HF patients underwent cardiopulmonary exercise testing and exercise-stress echocardiography. The lowest V̇E/V̇CO₂ ratio was assessed on respiratory gas analysis. Echocardiography was obtained at rest and at peak exercise. LVEF was measured using the method of disks. Cardiac output (CO) and the ratio of transmitral early filling velocity (E) to early diastolic tissue velocity (e') were calculated using the Doppler method. HF patients were divided into preserved EF (HFpEF) and reduced EF (HFrEF) using the LVEF cut-off 40% at rest. Twenty-four patients were classified as HFpEF and 33 as HFrEF. In HFpEF, age (r=0.58), CO (r=-0.44), e' (r=-0.48) and E/e' (r=0.45) during exercise correlated with the lowest V̇E/V̇CO₂ ratio (P<0.05 for all). In contrast, in HFrEF, age (r=0.47) and CO (r=-0.54) during exercise, but not e' and E/e', correlated with the lowest V̇E/V̇CO₂ ratio. Conclusions: Loss of CO augmentation was associated with ventilatory inefficiency in HF regardless of LVEF, although lung congestion determined ventilatory efficiency only in HFpEF.

Acute Decompensated Heart Failure in Patients with Heart Failure with Preserved Ejection Fraction

There are few treatment options for acute decompensated heart failure patients with preserved ejection fraction, but an increasing number of patients with heart failure with preserved ejection fraction. A deeper understanding of the cause, diagnosis, and prognosis of heart failure with preserved ejection fraction may be informative for clinical practice or clinical decision making and therapeutic investigation in the acute care setting.

Cardiopulmonary exercise test indices of respiratory buffering before and after aerobic exercise training in women with pulmonary hypertension: Differentiation by magnitudes of change in six-minute walk test performance

While aerobic exercise training (AET) has generally been shown to improve 6-min walk test (6MWT) distance (6MWD) in patients with pulmonary hypertension (PH), a substantial number of patients appear to adapt differently, with minimal or even negative changes in 6MWT distance being reported.

PURPOSE

To compare post-aerobic exercise training adaptations in cardiorespiratory functional capacity across three groups of patients with PH: those with high (HI), low (LI) and negative (NEG) post-training increases in 6MWD.

METHODS

Participants were 25 females (age 54 ± 11 years; BMI 31 ± 7 kg/m²) who completed a vigorous, 10-week, thrice weekly, supervised treadmill walking exercise program. Cardiopulmonary exercise tests (CPET) and 6MWT were completed before and after training. Ten of the 25 participants were classified as HI (range = 47-143 m), 11 were classified as LI (range = 4-37 m) and 4 were classified as NEG (range = -17 to -53 m).

RESULTS

Peak CPET duration, WR and time to anaerobic threshold (AT) were significantly higher (p < 0.05) after training in both the LI and HI groups but not in the NEG group. There was a significant improvement in VE/VCO₂ (p = 0.042), PETCO₂ (p = 0.011) and TV (p = 0.050) in the HI group after training, but not in the NEG or LI group.

CONCLUSION

These findings suggest that sustained ventilatory inefficiency and restricted respiratory buffering may mediate exercise intolerance and impede the ability to adapt to exercise training in some patients with PH.

Quantification of coronary artery disease using different modalities of cardiopulmonary exercise testing

BACKGROUND

This study examined the accuracy of cardiopulmonary exercise testing (CPET) on a treadmill (TM) and recumbent ergometry (RE) in the predicting coronary artery disease (CAD) severity and prognosis.

METHODS

Forty Caucasian subjects, mean age 63.5 ± 7.6, with significant coronary artery lesions (≥50%) were included. Within two months of coronary angiography, TM and RE CPET were performed on two visits 2-4 days apart and subsequently followed up to 32 ± 10 months.

RESULTS

Mean left ventricular ejection fraction was 56.7 ± 9.6%. TM CPET exhibited a higher occurrence of ST segment depression ≥ 1 mm (71.05% vs 28.95%, p = 0.04). Subjects with 1-2 stenotic coronary arteries (SCA) demonstrated a better CPET response compared to those with 3-SCA. ROC analysis revealed a high predictive value for the ventilation/carbon dioxide production (VE/VCO₂) slope obtained on TM (area 0.84, p = 0.003, Sn 88.9%, Sp 72%) in distinguishing between 1 and 2-SCA and 3-SCA. Among all CPET parameters, work efficiency (∆VO₂/∆WR) during RE predicted cumulative cardiac events (p < 0.01).

CONCLUSIONS

CPET parameters hold predictive value for CAD severity and prognosis. CPET on a TM appears to be more reliable in the quantification of CAD compared to RE.

Early Effects of Sacubitril/Valsartan on Exercise Tolerance in Patients with Heart Failure with Reduced Ejection Fraction

BACKGROUND

Sacubitril/valsartan in heart failure (HF) with reduced ejection fraction (HFrEF) was shown to be superior to enalapril in reducing the risk of death and hospitalization for HF. Our aim was to evaluate the cardiopulmonary effects of sacubitril/valsartan in patients with HFrEF.

METHODS

We conducted an observational study. Ninety-nine ambulatory patients with HFrEF underwent serial cardiopulmonary exercise tests (CPET) after initiation of sacubitril/valsartan in addition to recommended therapy.

RESULTS

At baseline, 37% of patients had New York Heart Association (NYHA) class III. After a median follow-up of 6.2 months (range 3⁻14.9 months) systolic blood pressure decreased from 117 ± 14 to 101 ± 12 mmHg (p < 0.0001), left ventricular ejection fraction (LVEF) increased from 27 ± 6 to 29.7 ± 7% (p < 0.0001), peak oxygen consumption (VO₂) improved from 14.6 ± 3.3 (% of predicted = 53.8 ± 14.1) to 17.2 ± 4.7 mL/kg/min (% of predicted = 64.7 ± 17.8) (p < 0.0001), minute ventilation/carbon dioxide production relationship (VE/VCO₂ Slope) decreased from 34.1 ± 6.3 to 31.7 ± 6.1 (p = 0.006), VO₂ at anaerobic threshold increased from 11.3 ± 2.6 to 12.6 ± 3.5 mL/kg/min (p = 0.007), oxygen pulse increased from 11.5 ± 3.0 to 13.4 ± 4.3 mL/kg/min (p < 0.0001), and ∆VO₂/∆Work increased from 9.2 ± 1.5 to 10.1 ± 1.8 mL/min/watt (p = 0.0002).

CONCLUSION

Sacubitril/valsartan improved exercise tolerance, LVEF, peak VO₂, and ventilatory efficiency at 6.2 months follow-up. Further studies are necessary to better clarify underlying mechanisms of this functional improvement.

The Relationship between Circulating Polyunsaturated Fatty Acid Levels and Exercise Responses of Patients with Non-ischemic Heart Failure

Objective Polyunsaturated fatty acids (PUFAs) are associated with heart failure (HF) as well as coronary artery disease. However, little is known about the relationships between PUFAs and the exercise responses of patients with HF. We evaluated the relationships between PUFAs and the parameters of cardiopulmonary exercise tests (CPETs) in patients with non-ischemic HF. Methods Fifty patients with stable non-ischemic HF underwent CPETs at our hospital. Data were analyzed to evaluate the relationships between PUFAs and echocardiographic findings as well as CPET and other test parameters. Results Correlations were significant and negative between dihomo-γ-linolenic acid (DGLA) + arachidonic acid (AA) and minute ventilation versus carbon dioxide production (VE/VCO₂) slope, and positive between N-terminal pro-B-type natriuretic peptide (NT-proBNP) and VE/VCO₂ slope. A multivariate regression analysis selected DGLA+AA and AA as independent predictors of VE/VCO₂ slope. However, eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) were not significantly correlated with the CPET parameters. Conclusion Low levels of circulating DGLA+AA and AA among PUFAs were associated with decreased exercise responses in patients with stable non-ischemic HF. These findings suggest that high levels of omega-6 PUFAs may improve the clinical outcomes of patients with non-ischemic HF via their effects on exercise responses.

The Metabolic Syndrome, Cardiovascular Fitness and Survival in Patients With Advanced Systolic Heart Failure

The metabolic syndrome (MetS), which incorporates insulin resistance, visceral adiposity, and dyslipidemia, is an independent risk factor for incident heart failure (HF), but the impact on survival is uncertain. We sought to determine the relation between the metabolic syndrome and survival in ambulatory systolic HF patients and the impact of MetS on cardiopulmonary exercise test (CPET). We identified adults with ejection fraction ≤40% who underwent CPETs between 2000 and 2011. Baseline MetS status was defined by 3 or more of: (1) Triglycerides ≥150 mg/dl; (2) High density lipoprotein <40 mg/dl males or <50 mg/dl females; (3) Diabetes mellitus; (4) Hypertension; (5) Body mass index ≥35 kg/m². Minimally-adjusted (for age, sex, transplantation and left ventricular assist device implantation) and fully-adjusted Cox proportional hazards models were constructed for all-cause mortality. MetS prevalence was 37% (716 of 1,953) and median follow-up 5 years. Mortality was 36% for +MetS and 29% for -MetS (p = 0.006), with highest mortality in the subgroup with both MetS plus diabetes (39%). The minimally-adjusted hazard ratio for mortality with MetS was 1.27 (95% confidence interval, 1.08 to 1.49, p = 0.004). After adjustment, MetS was no longer independently associated with mortality (hazard ratio 1.01, 95% confidence interval 0.85 to 1.19, p = 0.921). Patients with MetS achieved poorer CPET performance compared and MetS was independently associated with a lower peak VO₂. MetS was associated with a higher hazard of mortality in the minimally-adjusted model, which was primarily driven by the unfavorable impact of diabetes on mortality, but this association was no longer significant after full adjustment. In conclusion, there was no independent association between MetS and survival in an ambulatory systolic HF population.

Resting Heart Rate and Chronotropic Response to Exercise: Prognostic Implications in Heart Failure Across the Left Ventricular Ejection Fraction Spectrum

BACKGROUND

We studied the relationship between resting heart rate (HR), chronotropic response to exercise, and clinical outcomes in patients with heart failure (HF) across the spectrum of left ventricle ejection fraction (LVEF).

METHODS AND RESULTS

Resting HR and chronotropic index (CIx) were assessed in 718 patients with HF (53 ± 14 years of age, 66% male) referred for exercise testing. Associations with the composite outcome of left ventricular assist device implantation, transplantation, or death (151 events, 4.4 [range 3.0-5.8] years of follow-up) were assessed with the use of Cox models adjusted for age, sex, HF etiology, diabetes, LVEF, beta-blocker use, device therapy, estimated glomerular filtration rate, and peak oxygen uptake. Resting HR was 73 ± 15 beats/min, CIx was 0.60 ± 0.26, LVEF was 34% ± 15%, and 39% had an LVEF ≥40%. Resting HR correlated poorly with CIx (r = 0.08; P = .04) and did not predict (P = .84) chronotropic incompetence (CIx <0.60). Both higher resting HR (per 5 beats/min increase: adjusted hazard ratio [HR] -1.05, 95% confidence interval [CI] 1.00-1.11) and CIx (per SD change: adjusted HR -0.77, 95% CI 0.62-0.94) were independent prognostic markers. No heterogeneity of effect was noted based on LVEF (P >.05).

CONCLUSION

Higher resting HR and lower CIx are both associated with more severe HF, but correlated poorly with each other. They provide independent and additive prognostic information in HF across the LVEF spectrum.

The Role of Gas Exchange Variables in Cardiopulmonary Exercise Testing for Risk Stratification and Management of Heart Failure with Reduced Ejection Fraction

Heart failure with reduced ejection fraction (HFrEF) is common in the developed world and results in significant morbidity and mortality. Accurate risk assessment methods and prognostic variables are therefore needed to guide clinical decision making for medical therapy and surgical interventions with the ultimate goal of decreasing risk and improving health outcomes. The purpose of this review is to examine the role of cardiopulmonary exercise testing (CPET) and its most commonly used ventilatory gas exchange variables for the purpose of risk stratification and management of HFrEF. We evaluated five widely studied gas exchange variables from CPET in HFrEF patients based on nine previously used systematic criteria for biomarkers. This paper provides clinicians with a comprehensive and critical overview, class recommendations and evidence levels. Although some CPET variables met more criteria than others, evidence supporting the clinical assessment of variables beyond peak V̇O₂ is well-established. A multi-variable approach also including the V̇_E-V̇CO₂ slope and EOV is therefore recommended.

Analysis of Exercise-Induced Periodic Breathing Using an Autoregressive Model and the Hilbert-Huang Transform

Evaluation of exercise-induced periodic breathing (PB) in cardiopulmonary exercise testing (CPET) is one of important diagnostic evidences to judge the prognosis of chronic heart failure cases. In this study, we propose a method for the quantitative analysis of measured ventilation signals from an exercise test. We used an autoregressive (AR) model to filter the breath-by-breath measurements of ventilation from exercise tests. Then, the signals before reaching the most ventilation were decomposed into intrinsic mode functions (IMF) by using the Hilbert-Huang transform (HHT). An IMF represents a simple oscillatory pattern which catches a part of original ventilation signal in different frequency band. For each component of IMF, we computed the number of peaks as the feature of its oscillatory pattern denoted by Δ_i. In our experiment, 61 chronic heart failure patients with or without PB pattern were studied. The computed peaks of the third and fourth IMF components, Δ₃ and Δ₄, were statistically significant for the two groups (both p values < 0.02). In summary, our study shows a close link between the HHT analysis and level of intrinsic energy for pulmonary ventilation. The third and fourth IMF components are highly potential to indicate the prognosis of chronic heart failure.

Change in Submaximal Cardiorespiratory Fitness and All-Cause Mortality

OBJECTIVE

To evaluate the relationship between change in submaximal cardiorespiratory fitness (sCRF) and all-cause mortality risk in adult men and women.

PATIENTS AND METHODS

A prospective study with at least 2 clinical visits (mean follow-up time, 4.2±3.0 years) between April 1974 and January 2002 was conducted to assess the relationship between change in sCRF and mortality risk during follow-up. Participants were 6106 men and women. Submaximal CRF was determined using the heart rate obtained at the 5-minute mark of a graded maximal treadmill test used to determine maximal CRF (mCRF). Change in sCRF from baseline to follow-up was categorized into 3 groups: increased fitness (decreased heart rate, <-4.0 beats/min), stable fitness (heart rate, -4.0 to 3.0 beats/min), and decreased fitness (increased heart rate, >3.0 beats/min).

RESULTS

The mean change in sCRF at follow-up for all 6106 study participants was -0.5±10.0 beats/min, and the mean change in mCRF was -0.3±1.4 metabolic equivalents. Change in sCRF was related to change in mCRF, though the variance explained was small (R²=0.21; P<.001). The hazard ratios (95% CIs) for all-cause mortality were 0.60 (0.38-0.96) for stable and 0.59 (0.35-1.00) for increased sCRF compared with decreased sCRF after adjusting for age, change in weight, and other common risk factors for premature mortality. The hazard ratios for changes in sCRF and mCRF were not significant after adjusting for changes in mCRF (P=.29) and sCRF (P=.60), respectively.

CONCLUSION

A simple 5-minute submaximal test of CRF identified that adults who maintained or improved sCRF were less likely to die from all causes during follow-up than were adults whose sCRF decreased.

Impact of Atrial Fibrillation on Exercise Capacity and Mortality in Heart Failure With Preserved Ejection Fraction: Insights From Cardiopulmonary Stress Testing

Background

Atrial fibrillation (AF) has been objectively associated with exercise intolerance in patients with heart failure with reduced ejection fraction; however, its impact in patients with heart failure with preserved ejection fraction has not been fully scrutinized.

Methods and Results

We identified 1744 patients with heart failure and ejection fraction ≥50% referred for cardiopulmonary stress testing at the Cleveland Clinic (Cleveland, OH), 239 of whom had AF. We used inverse probability of treatment weighting to balance clinical characteristics between patients with and without AF. A weighted linear regression model, adjusted for unbalanced variables (age, sex, diagnosis, hypertension, and β‐blocker use), was used to compare metabolic stress parameters and 8‐year total mortality (social security index) between both groups. Weighted mean ejection fraction was 58±5.9% in the entire population. After adjusting for unbalanced weighted variables, patients with AF versus those without AF had lower mean peak oxygen consumption (18.5±6.2 versus 20.3±7.1 mL/kg per minute), oxygen pulse (12.4±4.3 versus 12.9±4.7 mL/beat), and circulatory power (2877±1402 versus 3351±1788 mm Hg·mL/kg per minute) (P<0.001 for all comparisons) but similar submaximal exercise capacity (oxygen consumption at anaerobic threshold, 12.0±5.1 versus 12.4±6.0mL/kg per minute; P =0.3). Both groups had similar peak heart rate, whereas mean peak systolic blood pressure was lower in the AF group (150±35 versus 160±51 mm Hg; P<0.001). Moreover, AF was associated with higher total mortality.

Conclusions

In the largest study of its kind, we demonstrate that AF is associated with peak exercise intolerance, impaired contractile reserve, and increased mortality in patients with heart failure with preserved ejection fraction. Whether AF is the primary offender in these patients or merely a bystander to worse diastolic function requires further investigation.

Prognostic ability of VE/VCO2 slope calculations using different exercise test time intervals in subjects with heart failure

BACKGROUND

The minute ventilation-carbon dioxide production (VE/VCO2) slope, obtained during exercise testing, possesses prognostic value in heart failure (HF). The VE-VCO2 relationship is generally linear thereby hypothetically producing similar slope values regardless of the exercise-test time interval used for calculation.

DESIGN

This study assesses the ability of the VE/VCO2 slope, calculated at different time intervals throughout a progressive exercise test, to predict 1-year cardiac-related hospitalization and mortality in subjects with HF.

METHODS

Seventy-two subjects underwent symptom-limited exercise testing with ventilatory expired gas analysis. Mean age and left ventricular ejection fraction for 44 male and 28 female subjects were 51.2 years (+/-13.0) and 27.0% (+/-12.3) respectively. The VE/VCO2 slope was calculated from time 0 to 25, 50, 75 and 100% of exercise time and subsequently used to create five randomly selected VE/VCO2 slope categories.

RESULTS

(The intraclass correlation coefficient found calculation of the VE/VCO2 slope, when divided into quartiles, to be a reliable measure (alpha=0.94, P<0.0001). Univariate Cox regression analysis revealed all VE/VCO2 slope categories (25-100% and random selections) were significant predictors of cardiac-related hospitalization and mortality over a 1-year period. Multivariate Cox regression analysis revealed all VE/VCO2 slope categories outperformed peak oxygen consumption (VO2) in predicting hospitalization and mortality at 1 year.

CONCLUSIONS

Although the different classification schemes were not identical, these results suggest VE/VCO2 slope maintains prognostic significance regardless of exercise-test time interval. Calculation of VE/VCO2 slope may therefore still be valuable in subjects putting forth a sub-maximal effort while effort-dependent measures, such as peak VO2, are not.

Statement on cardiopulmonary exercise testing in chronic heart failure due to left ventricular dysfunction: recommendations for performance and interpretation Part III: Interpretation of cardiopulmonary exercise testing in chronic heart failure and future applications: Task Force of the Italian Working Group on Cardiac Rehabilitation and Prevention (Gruppo Italiano di Cardiologia Riabilitativa e Prevenzione, GICR), endorsed by Working Group on Cardiac Rehabilitation and Exercise Physiology of the European Society of Cardiology

Optimal use of cardiopulmonary exercise testing (CPET) in clinical practice and chronic heart failure (CHF) requires appropriate data presentation and a flexible interpretative strategy. The greatest potential impact on the decision-making process may rest not on the value of any individual measurement, although some are obviously more important than others, but rather on their integrative use. Such an integrative approach relies on interrelationship, trending phenomena and patterns of key gas exchange variable responses. An multiparametric approach will be discussed in different clinical applications, for exercise prescription and monitoring, functional evaluation of drug therapy or cardiac resynchronisation therapy efficacy, and risk stratification. The role of CPET in the daily clinical decision-making process will be underscored. Future indications of CPET will be addressed, suggesting and promoting an extended candidacy either to all CHF patients, including those at high risk or most vulnerable, such as female, elderly patients, and patients with implantable cardioverter defibrillator or in every clinical setting where objective definition of exercise capacity provides implications for medical, surgical, and social decision making.

Effect of Selective Heart Rate Slowing in Heart Failure With Preserved Ejection Fraction

BACKGROUND

Heart failure with preserved ejection fraction (HFpEF) is associated with significant morbidity and mortality but is currently refractory to therapy. Despite limited evidence, heart rate reduction has been advocated, on the basis of physiological considerations, as a therapeutic strategy in HFpEF. We tested the hypothesis that heart rate reduction improves exercise capacity in HFpEF.

METHODS AND RESULTS

We conducted a randomized, crossover study comparing selective heart rate reduction with the If blocker ivabradine at 7.5 mg twice daily versus placebo for 2 weeks each in 22 symptomatic patients with HFpEF who had objective evidence of exercise limitation (peak oxygen consumption at maximal exercise [o2 peak] <80% predicted for age and sex). The result was compared with 22 similarly treated matched asymptomatic hypertensive volunteers. The primary end point was the change in o2 peak. Secondary outcomes included tissue Doppler-derived E/e' at echocardiography, plasma brain natriuretic peptide, and quality-of-life scores. Ivabradine significantly reduced peak heart rate compared with placebo in the HFpEF (107 versus 129 bpm; P<0.0001) and hypertensive (127 versus 145 bpm; P=0.003) cohorts. Ivabradine compared with placebo significantly worsened the change in o2 peak in the HFpEF cohort (-2.1 versus 0.9 mL·kg(-1)·min(-1); P=0.003) and significantly reduced submaximal exercise capacity, as determined by the oxygen uptake efficiency slope. No significant effects on the secondary end points were discernable.

CONCLUSION

Our observations bring into question the value of heart rate reduction with ivabradine for improving symptoms in a HFpEF population characterized by exercise limitation.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT02354573.

The Heart Failure Overweight/Obesity Survival Paradox: The Missing Sex Link

OBJECTIVES

This study sought to determine whether body mass index (BMI) has a differential impact on survival for females versus males with advanced systolic heart failure (HF).

BACKGROUND

Females have a survival advantage in HF, the mechanisms of which are unclear. There is also a proposed "obesity survival paradox" in which excess adiposity promotes HF survival.

METHODS

We reviewed 3,811 patients with left ventricular ejection fraction ≤40% who had undergone cardiopulmonary exercise testing between 1995 and 2011. The endpoint was all-cause mortality. Multivariable analysis was performed using a Cox proportional hazards model. Because of the nonlinearity of BMI, a restricted cubic spline was used. An interaction term was added to investigate the impact of BMI on mortality by sex.

RESULTS

The unadjusted data demonstrated an overall obesity survival paradox in HF. This survival paradox disappeared for males after adjustment for potential confounders, with overweight and obese males showing higher adjusted mortality hazard ratios compared with normal weight males. Conversely, females in the overweight BMI range (25.0 to 29.9 kg/m(2)) had the lowest adjusted mortality (hazard ratio: 0.84; 95% confidence interval: 0.77 to 0.93; p = 0.0005 compared with normal weight females) with a nadir in mortality hazard just below BMI 30 kg/m(2). The multivariable model supported a differential impact of BMI on mortality in males versus females (p for interaction <0.0001).

CONCLUSIONS

In this advanced HF cohort, an unadjusted obesity survival paradox disappeared after adjustment for confounders. Overweight and obese males had higher adjusted mortality than normal weight males, whereas a BMI in the overweight range was associated with a significant survival benefit in females.

Skeletal Muscle Changes in Chronic Cardiac Disease and Failure

Peak exercise performance in healthy man is limited not only by pulmonary or skeletal muscle function but also by cardiac function. Thus, abnormalities in cardiac function will have a major impact on exercise performance. Many cardiac diseases affect exercise performance and indeed for some cardiac conditions such as atherosclerotic heart disease, exercise testing is frequently used not only to measure functional capacity but also to make a diagnosis of heart disease, evaluate the efficacy of treatment, and predict prognosis. Early in the course of cardiac diseases, exercise performance will be minimally affected but with disease progression impairment in exercise capacity will become apparent. Ejection fraction, that is, the percent of blood volume ejected with each cardiac cycle is often used as a measure of cardiac performance but frequently there is a dissociation between the ejection fraction and exercise capacity in patients with heart disease. How abnormalities in cardiac function impacts the muscles, vasculature, and lungs to impact exercise performance will here be reviewed. The focus of this work will be on patients with systolic heart failure as the incidence and prevalence of heart failure is reaching epidemic proportions and heart failure is the end result of many other chronic cardiac diseases. The prognostic role of exercise and benefits of exercise training will also be discussed.

Speckle-Tracking Echocardiographic Measures of Right Ventricular Function Correlate With Improvement in Exercise Function After Percutaneous Pulmonary Valve Implantation

BACKGROUND

Speckle-tracking echocardiographic (STE) measures of right ventricular (RV) function appear to improve after transcatheter pulmonary valve implantation (TPVI). Measures of exercise function, such as ventilatory efficiency (the minute ventilation [VE]/carbon dioxide production [VCO2] slope), have been shown to be prognostic of mortality in patients who may require TPVI. The aim of this study was to evaluate the correlation between STE measures of RV function and changes in VE/VCO2 after TPVI.

METHODS

Speckle-tracking echocardiography and cardiopulmonary exercise testing were performed at baseline and 6 months after TPVI in 24 patients from four centers. Conventional echocardiographic measures of RV function were also assessed. Echocardiographic and exercise stress test results were interpreted by single blinded observers at separate core laboratories.

RESULTS

All patients demonstrated relief of pulmonary regurgitation and stenosis after TPVI. Improvements in RV longitudinal strain (-16.9 ± 3.5% vs -19.7 ± 4.3%, P < .01) and strain rate (-0.9 ± 0.4 vs. -1.2 ± 0.4 s(-1), P < .01) were noted. The VE/VCO2 slope improved (32.4 ± 5.7 vs 31.5 ± 8.8, P = .03). No other significant echocardiographic or exercise changes were found. On multivariate regression, the change in VE/VCO2 was independently associated with change in RV longitudinal early diastolic strain rate (P < .001) and tricuspid A velocity (P < .001). Preintervention RV longitudinal strain was found to be a predictor of change in VE/VCO2 after TPVI (r = -0.60, P < .001).

CONCLUSIONS

STE measures of RV function appear to hold the potential for use as predictors of improved outcomes in patients requiring TPVI. Future studies should directly assess the prognostic significance of STE measures of RV function in this population.

Comprehensive analysis of cardiopulmonary exercise testing and mortality in patients with systolic heart failure: the Henry Ford Hospital cardiopulmonary exercise testing (FIT-CPX) project

BACKGROUND

Many studies have shown a strong association between numerous variables from a cardiopulmonary exercise (CPX) test and prognosis in patients with heart failure with reduced ejection fraction (HFrEF). However, few studies have compared the prognostic value of a majority of these variables simultaneously, so controversy remains regarding optimal interpretation.

METHODS AND RESULTS

This was a retrospective analysis of patients with HFrEF (n = 1,201; age = 55 ± 13 y; 33% female) and a CPX test from 1997 to 2010. Thirty variables from a CPX test were considered in separate adjusted Cox regression analyses to describe the strength of the relation of each to a composite end point of all-cause mortality, left ventricular assist device implantation, or heart transplantation. During a median follow-up of 3.8 years, there were 577 (48.0%) events. The majority of variables were highly significant (P < .001). Among these, percentage of predicted maximum V˙O2 (ppMV˙O2; Wald = 203; P < .001; C-index = 0.73) was similar to VE-VCO2 slope (Wald = 201; P < .001; C = 0.72) and peak V˙O2 (Wald = 161; P < .001; C = 0.72). In addition, there was no significant interaction observed for peak respiratory exchange ratio <1 vs ≥1.

CONCLUSIONS

Consistent with prior studies, many CPX test variables were strongly associated with prognosis in patients with HFrEF. The choice of which variable to use is up to the clinician. Renewed attention should be given to ppMV˙O2, which appears to be highly predictive of survival in these patients.

Physiology of oxygen uptake kinetics: Insights from incremental cardiopulmonary exercise testing in the Study of Health in Pomerania

BACKGROUND

Cardiopulmonary exercise testing allows for assessment of cardiac and respiratory limitation, but is often affected by patient effort. Indices of oxygen kinetics, including the oxygen uptake efficiency slope (OUES), oxygen uptake-work-rate slope (VO2-WR slope) and the heart rate-oxygen uptake slope (HR-VO2 slope) are relatively effort independent but may be affected by patient characteristics. The objective of this study is to identify the impact of factors, such as age, gender, body size, respiratory function, smoking and beta-blockade on these parameters, as well as generate predictive equations.

METHODS

1708 volunteers from the population-based Study of Health in Pomerania underwent an incremental bicycle exercise protocol. Markers of oxygen kinetics were calculated. Participants with structural heart disease, echocardiographic or lung function pathology were excluded, leaving 577 males and 625 females. Age, height, weight, smoking, forced expiratory volume in 1 s (FEV1) and beta-blockers were analysed for their influencing power by gender. Quantile regression analysis determined the reference equations for each parameter.

RESULTS

Age, gender, height, weight and FEV1 (but not percent predicted FEV1) are strongly related to OUES. Participants using beta-blockers and male smokers had significantly lower OUES values. VO2-WR slope was minimally affected by age, gender, weight and FEV1. Gender, height, weight and beta-blocker use, but not FEV1 and smoking status, were related to the HR-VO2 slope whilst age was only related in females.

CONCLUSIONS

Markers of oxygen kinetics are differentially affected by patient characteristics. This study provides normal reference values for these variables thereby facilitating interpretation of oxygen uptake kinetics in health and disease.

Predictors of long-term outcomes in patients with hypertrophic cardiomyopathy undergoing cardiopulmonary stress testing and echocardiography

BACKGROUND

Patients with hypertrophic cardiomyopathy (HCM) have exercise intolerance due to left ventricular outflow tract (LVOT) obstruction, mitral regurgitation, and left ventricular dysfunction. We sought to study predictors of outcomes in HCM patients undergoing cardiopulmonary stress testing (CPT).

METHODS

We studied 1,005 HCM patients (50 ± 14 years, 64% men, 77% on β-blockers) who underwent CPT with echocardiography. Clinical, echocardiographic, and exercise variables (peak oxygen consumption [VO2] and heart rate recovery [HRR] at first minute postexercise) were recorded. End point was a composite of death, appropriate defibrillator discharges, resuscitated sudden death, stroke, and heart failure admission.

RESULTS

Mean left ventricular ejection fraction (LVEF), postexercise LVOT gradient, and peak VO2 were 62% ± 6%, 92 ± 51 mm Hg, and 21 ± 6 mL kg(-1) min(-1), respectively. Despite 789 patients (78%) being in New York Heart Association classes I to II, only 8% achieved >100% age-gender predicted peak VO2, whereas 77% and 15% achieved 50% to 100% and <50%, respectively. Left ventricular outflow tract gradient ≥30 mm Hg was observed in 83% patients, whereas 23% had abnormal HRR. More than 5.5 ± 4 years, there were 94 (9%) events; 511 (50%) patients underwent surgery for LVOT obstruction. Multivariable Cox proportional analysis demonstrated % age-gender predicted peak VO2 (hazard ratio [HR] 0.96 [0.93-0.98]), normal vs abnormal HRR (HR 0.48 [0.32-0.73]), higher LVEF (HR 0.96 [0.93-0.98]), surgery (0.53 [0.33-0.83]), and atrial fibrillation (HR 1.65 [1.04-2.60]) were associated with outcomes (all P < .05).

CONCLUSIONS

In HCM patients undergoing CPT, a higher % of achieved age-gender predicted VO2 and surgical relief of LVOT obstruction were associated with better outcomes, whereas abnormal HRR, atrial fibrillation, and lower LVEF were associated with worse outcomes.

Clinical utility of exercise training in heart failure with reduced and preserved ejection fraction

Reduced exercise tolerance is an independent predictor of hospital readmission and mortality in patients with heart failure (HF). Exercise training for HF patients is well established as an adjunct therapy, and there is sufficient evidence to support the favorable role of exercise training programs for HF patients over and above the optimal medical therapy. Some of the documented benefits include improved functional capacity, quality of life (QoL), fatigue, and dyspnea. Major trials to assess exercise training in HF have, however, focused on heart failure with reduced ejection fraction (HFREF). At least half of the patients presenting with HF have heart failure with preserved ejection fraction (HFPEF) and experience similar symptoms of exercise intolerance, dyspnea, and early fatigue, and similar mortality risk and rehospitalization rates. The role of exercise training in the management of HFPEF remains less clear. This article provides a brief overview of pathophysiology of reduced exercise tolerance in HFREF and heart failure with preserved ejection fraction (HFPEF), and summarizes the evidence and mechanisms by which exercise training can improve symptoms and HF. Clinical and practical aspects of exercise training prescription are also discussed.

Echocardiographic determinants of peak aerobic capacity and breathing efficiency in patients with undifferentiated dyspnea

Diastolic function and E/e' correlate with peak aerobic capacity (VO2) in patients with heart failure, but the echocardiographic correlates of abnormal gas exchange in patients without heart failure are not well defined. We sought to determine the echocardiographic correlates of peak VO2 and breathing efficiency (estimated using the ratio of minute ventilation to carbon dioxide production, or VE/VCO2 nadir) in patients with unexplained dyspnea. We identified 232 patients with unexplained dyspnea who underwent echocardiography at rest followed by stress echocardiography with simultaneous measurement of peak VO2 and VE/VCO2 nadir. At baseline, 17 patients (5%) had an E/e' of ≥15 while 31 patients (17%) had a right ventricular systolic pressure (RVSP) of >35 mm Hg. E/e' ≥15 and RVSP >35 mm Hg were associated with lower peak VO2 (14.1 ± 4.4 vs 21.0 ± 6.9 and 15.2 ± 3.6 vs 21.8 ± 6.8 ml/kg/min, respectively, p <0.0001). E/e' ≥15 (sensitivity 0.13, specificity 0.99, area under the curve 0.64) and RVSP >35 mm Hg (sensitivity 0.38, specificity 0.93, area under the curve 0.76) were highly specific for predicting limited peak VO2. Age and RVSP at rest were independent correlates with VE/VCO2, but diastolic function was not. However, the risk of having abnormal VE/VCO2 nadir was only elevated in subjects with elevated RVSP in the setting of abnormal diastolic function (hazard ratio 2.4, 95% confidence interval 1.3 to 4.6, p = 0.02). In conclusion, both E/e' ≥15 and RVSP >35 mm Hg are highly specific markers of exercise limitation in patients without heart failure, but RVSP at rest may offer better overall diagnostic power than E/e' to predict low peak VO2 in this group.

Early defects identified by computed tomography angiography are associated with left ventricular dysfunction and exercise intolerance following acute myocardial infarction

PURPOSE

We evaluated the influence of early defects (EDs) in the infarcted myocardium after reperfusion, detected by computed tomography angiography (CTA), on cardiac function and exercise capacity in the chronic phase.

MATERIALS AND METHODS

We retrospectively analyzed 48 acute myocardial infarction (AMI) patients who underwent both CTA using 64-slice multidetector CT within 14 ± 6 days and cardiopulmonary exercise testing within 3 months after AMI onset between 2005 and 2007. The patients were divided into 2 groups: the EDs <75 % or EDs ≥75 % group. Brain natriuretic peptide (BNP) levels and ejection fraction (EF) were measured 6 months after AMI onset.

RESULTS

The minute ventilation-carbon dioxide production slope was significantly higher in the EDs ≥75 % group (28.7 ± 4.9) than in the EDs <75 % group (25.1 ± 3.1, P = 0.048). EF at 6 months was significantly lower in the EDs ≥75 % group (48.1 ± 12.0 %) than in the EDs <75 % group (56.8 ± 10.0 %, P = 0.01). Log of BNP levels was higher in the EDs ≥75 % group than in the EDs <75 % group (P < 0.001).

CONCLUSION

EDs detected by CTA in the acute phase of AMI influenced myocardial dysfunction and exercise intolerance in the chronic phase.

Do optimal prognostic thresholds in continuous physiological variables really exist? Analysis of origin of apparent thresholds, with systematic review for peak oxygen consumption, ejection fraction and BNP

Background

Clinicians are sometimes advised to make decisions using thresholds in measured variables, derived from prognostic studies.

Objectives

We studied why there are conflicting apparently-optimal prognostic thresholds, for example in exercise peak oxygen uptake (pVO₂), ejection fraction (EF), and Brain Natriuretic Peptide (BNP) in heart failure (HF).

Data Sources and Eligibility Criteria

Studies testing pVO₂, EF or BNP prognostic thresholds in heart failure, published between 1990 and 2010, listed on Pubmed.

Methods

First, we examined studies testing pVO₂, EF or BNP prognostic thresholds. Second, we created repeated simulations of 1500 patients to identify whether an apparently-optimal prognostic threshold indicates step change in risk.

Results

33 studies (8946 patients) tested a pVO₂ threshold. 18 found it prognostically significant: the actual reported threshold ranged widely (10–18 ml/kg/min) but was overwhelmingly controlled by the individual study population's mean pVO₂ (r = 0.86, p<0.00001). In contrast, the 15 negative publications were testing thresholds 199% further from their means (p = 0.0001). Likewise, of 35 EF studies (10220 patients), the thresholds in the 22 positive reports were strongly determined by study means (r = 0.90, p<0.0001). Similarly, in the 19 positives of 20 BNP studies (9725 patients): r = 0.86 (p<0.0001).

Second, survival simulations always discovered a “most significant” threshold, even when there was definitely no step change in mortality. With linear increase in risk, the apparently-optimal threshold was always near the sample mean (r = 0.99, p<0.001).

Limitations

This study cannot report the best threshold for any of these variables; instead it explains how common clinical research procedures routinely produce false thresholds.

Key Findings

First, shifting (and/or disappearance) of an apparently-optimal prognostic threshold is strongly determined by studies' average pVO₂, EF or BNP. Second, apparently-optimal thresholds always appear, even with no step in prognosis.

Conclusions

Emphatic therapeutic guidance based on thresholds from observational studies may be ill-founded. We should not assume that optimal thresholds, or any thresholds, exist.