Cardiopulmonary exercise testing reflects similar pathophysiology and disease severity in heart failure patients with reduced and preserved ejection fraction

Comparable Ventilatory Inefficiency at Maximal and Submaximal Performance in COPD vs. CHF subjects: An Innovative Approach

BACKGROUND

Currently, excess ventilation has been grounded under the relationship between minute-ventilation/carbon dioxide output ( V ˙ E - V ˙ CO 2 ). Alternatively, a new approach for ventilatory efficiency ( η E V ˙ ) has been published.

OBJECTIVE

Our main hypothesis is that comparatively low levels of η E V ˙ between chronic heart failure (CHF) and chronic obstructive pulmonary disease (COPD) are attainable for a similar level of maximum and submaximal aerobic performance, conversely to long-established methods ( V ˙ E - V ˙ CO 2 slope and intercept).

METHODS

Both groups performed lung function tests, echocardiography, and cardiopulmonary exercise testing. The significance level adopted in the statistical analysis was 5%. Thus, nineteen COPD and nineteen CHF-eligible subjects completed the study. With the aim of contrasting full values of V ˙ E - V ˙ CO 2 and η V ˙ E for the exercise period (100%), correlations were made with smaller fractions, such as 90% and 75% of the maximum values.

RESULTS

The two groups attained matched characteristics for age (62±6 vs. 59±9 yrs, p>.05), sex (10/9 vs. 14/5, p>0.05), BMI (26±4 vs. 27±3 Kg m2, p>0.05), and peak V ˙ O 2 (72±19 vs. 74±20 %pred, p>0.05), respectively. The V ˙ E - V ˙ CO 2 slope and intercept were significantly different for COPD and CHF (27.2±1.4 vs. 33.1±5.7 and 5.3±1.9 vs. 1.7±3.6, p<0.05 for both), but η V ˙ E average values were similar between-groups (10.2±3.4 vs. 10.9±2.3%, p=0.462). The correlations between 100% of the exercise period with 90% and 75% of it were stronger for η V ˙ E (r>0.850 for both).

CONCLUSION

The η V ˙ E is a valuable method for comparison between cardiopulmonary diseases, with so far distinct physiopathological mechanisms, including ventilatory constraints in COPD.

Cardiopulmonary Exercise Testing in Heart Failure With Preserved Ejection Fraction: Technique Principles, Current Evidence, and Future Perspectives

Heart failure with preserved ejection fraction (HFpEF) is a multifactorial clinical syndrome involving a rather complex pathophysiologic substrate and quite a challenging diagnosis. Exercise intolerance is a major feature of HFpEF, and in many cases, diagnosis is suspected in subjects presenting with exertional dyspnea. Cardiopulmonary exercise testing (CPET) is a noninvasive, dynamic technique that provides an integrative evaluation of cardiovascular, pulmonary, hematopoietic, neuropsychological, and metabolic functions during maximal or submaximal exercise. The assessment is based on the principle that system failure typically occurs when the system is under stress, and thus, CPET is currently considered to be the gold standard for identifying exercise intolerance, allowing the differential diagnosis of underlying causes. CPET is used in observational studies and clinical trials in HFpEF; however, in most cases, only a few from a wide variety of CPET parameters are examined, while the technique is largely underused in everyday cardiology practice. This article discusses the basic principles and methodology of CPET and studies that utilized CPET in patients with HFpEF, in an effort to increase awareness of CPET capabilities among practicing cardiologists.

Impact of Cardiac Power Output on Exercise Capacity and Clinical Outcome in Patients With Chronic Heart Failure

Less data are available regarding the impact of cardiac power output on exercise capacity or clinical outcome in patients with chronic heart failure (CHF). The study enrolled 280 consecutive patients with CHF referred for cardiopulmonary exercise testing and right-sided heart catheterization between 2013 and 2018. The primary outcome was composite of heart failure hospitalization or death. Cardiac power output was calculated as (mean arterial pressure × CO) ÷ 451. Patients with low cardiac power output (<0.53 W, n = 99) were older and had a higher brain natriuretic peptide level than patients with high cardiac power output (≥0.53W, n = 181). Cardiac power output was correlated with peak oxygen consumption (peak V̇O2), peak workload achievement, and ventilatory efficiency (V̇E/V̇CO2 slope) in cardiopulmonary exercise testing, whereas each of cardiac output or mean arterial pressure was not. There were 48 patients with events over a median follow-up period of 3.5 (interquartile range 1.0 to 6.0) years. Patients with low cardiac power output had about a 2-fold higher risk of events than those with a high cardiac power output (hazard ratio 1.97, 95% confidence interval 1.12 to 3.48). In the multivariable Cox regression, a 0.1-W decrease in cardiac power output was associated with 19% increased adverse events (hazard ratio 0.81, 95% confidence interval 0.67 to 0.99). In conclusion, cardiac power output was associated with reduced exercise capacity and poor clinical outcome, suggesting that cardiac power output is useful for risk stratification in patients with CHF. Further study is required to identify therapies targeting cardiac power output to improve the exercise capacity or clinical outcome in patients with CHF.

Ventilatory Efficiency Is Reduced in People With Hypertension During Exercise

Background An elevated ventilatory efficiency slope during exercise (minute ventilation/volume of expired CO2; VE/VCO2 slope) is a strong prognostic indicator in heart failure. It is elevated in people with heart failure with preserved ejection, many of whom have hypertension. However, whether the VE/VCO2 slope is also elevated in people with primary hypertension versus normotensive individuals is unknown. We hypothesize that there is a spectrum of ventilatory inefficiency in cardiovascular disease, reflecting an increasingly abnormal physiological response to exercise. The aim of this study was to evaluate the VE/VCO2 slope in patients with hypertension compared with age-, peak oxygen consumption-, and sex-matched healthy subjects. Methods and Results Ramped cardiovascular pulmonary exercise tests to peak oxygen consumption were completed on a bike ergometer in 55 patients with primary hypertension and 24 normotensive controls. The VE/VCO2 slope was assessed from the onset of exercise to peak oxygen consumption. Data were compared using unpaired Student t test. Age (mean±SD, 66±6 versus 64±6 years; P=0.18), body mass index (25.4±3.5 versus 24±2.4 kg/m2; P=0.13), and peak oxygen consumption (23.2±6.6 versus 24±7.3 mL/min per kg; P=0.64) were similar between groups. The VE/VCO2 slope was elevated in the hypertensive group versus controls (31.8±4.5 versus 28.4±3.4; P=0.002). Only 27% of the hypertensive group were classified as having a normal VE/VCO2 slope (20-30) versus 71% in the control group. Conclusions Ventilatory efficiency is impaired people with hypertension without a diagnosis of heart failure versus normotensive individuals. Future research needs to establish whether those patients with hypertension with elevated VE/VCO2 slopes are at risk of developing future heart failure.

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.

Peak exercise myocardial deformation indices during cardiopulmonary exercise testing are associated with exercise capacity and ventilatory efficiency in patients with dilated cardiomyopathy

OBJECTIVE

Little is known about the exercise-induced changes in the multidimensional mechanical properties of the heart. We aimed to evaluate the myocardial deformation indices (MDI) at rest and their response at peak exercise during the same cardiopulmonary exercise testing (CPET) session, investigating their relationship to exercise capacity and ventilatory sufficiency in dilated cardiomyopathy (DCM) patients.

METHODS

We evaluated left ventricular (LV) function using speckle tracking imaging (STI) at rest and peak exercise during the same CPET session in 57 idiopathic DCM patients in New York Heart Association (NYHA) I-II class [54 ± 12 years, 42 males, ejection fraction (EF) 33 ± 9%]. We measured global longitudinal strain (GLS), longitudinal strain rate at systole (LSRS) and diastole (LSRD), and circumferential strain rate (CircS).

RESULTS

Resting GLS, LSRS, and LSRD were impaired compared with the predicted values but were improved at peak exercise (p < 0.001). All MDI at rest and/or at peak exercise were related to several CPET-derived parameters, including peak VO₂, load, O₂ pulse, and VE/VCO₂ slope. Peak exercise LSRS > -1.10 sec^-1 (AUC = 0.80, p < 0.001) and GLS > -13% (AUC = 0.81, p = 0.002) predicted impaired exercise capacity (peak VO₂ < 20 ml/min/kg) and ventilatory inefficiency (VE/VCO₂ slope>34). In multiple regression analysis, peak exercise LSRS and GLS were independently related to the peak VO₂ (Beta = -0.39, p = 0.003) and VE/VCO₂ slope (Beta = 0.35, p = 0.02), respectively.

CONCLUSIONS

Peak exercise LSRS and GLS in NYHA I-II DCM patients subjected to CPET were associated with aerobic exercise capacity and ventilatory efficiency. Consequently, LSRS and GLS at peak exercise, through their association with CPET-derived CV risk indices, may underline the severity of heart failure and predict future CV events in this DCM population.

Hemodynamic Assessment in Heart Failure with Preserved Ejection Fraction

Heart failure (HF) with preserved ejection fraction (HFpEF) is characterized by an inability of the heart to perfuse the body without pathologic increases in filling pressure at rest or during exertion. Right heart catheterization provides direct assessment for HF, providing the most robust and direct method to evaluate the central hemodynamic abnormalities, and serves as the gold standard to confirm or refute the presence of HFpEF. This article reviews current understanding of the best practices in the performance and interpretation of hemodynamic assessment, relates important pathophysiologic concepts to clinical care, and discusses current and evidence-based applications of hemodynamics in HFpEF.

Excess ventilation and exertional dyspnoea in heart failure and pulmonary hypertension

Increased ventilation relative to metabolic demands, indicating alveolar hyperventilation and/or increased physiological dead space (excess ventilation), is a key cause of exertional dyspnoea. Excess ventilation has assumed a prominent role in the functional assessment of patients with heart failure (HF) with reduced (HFrEF) or preserved (HFpEF) ejection fraction, pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH). We herein provide the key pieces of information to the caring physician to 1) gain unique insights into the seeds of patients' shortness of breath and 2) develop a rationale for therapeutically lessening excess ventilation to mitigate this distressing symptom. Reduced bulk oxygen transfer induced by cardiac output limitation and/or right ventricle-pulmonary arterial uncoupling increase neurochemical afferent stimulation and (largely chemo-) receptor sensitivity, leading to alveolar hyperventilation in HFrEF, PAH and small-vessel, distal CTEPH. As such, interventions geared to improve central haemodynamics and/or reduce chemosensitivity have been particularly effective in lessening their excess ventilation. In contrast, 1) high filling pressures in HFpEF and 2) impaired lung perfusion leading to ventilation/perfusion mismatch in proximal CTEPH conspire to increase physiological dead space. Accordingly, 1) decreasing pulmonary capillary pressures and 2) mechanically unclogging larger pulmonary vessels (pulmonary endarterectomy and balloon pulmonary angioplasty) have been associated with larger decrements in excess ventilation. Exercise training has a strong beneficial effect across diseases. Addressing some major unanswered questions on the link of excess ventilation with exertional dyspnoea under the modulating influence of pharmacological and nonpharmacological interventions might prove instrumental to alleviate the devastating consequences of these prevalent diseases.

Cardiopulmonary exercise responses in patients with non-ischemic heart failure and a mildly reduced ejection fraction

Background: The cardiopulmonary response to exercise in patients with heart failure exhibiting a mildly reduced ejection fraction (41% ≤ EF ≤ 49%) remains unclear. Materials & methods: A total of 193 consecutive patients with heart failure (excluding those with coronary artery disease) who underwent cardiopulmonary exercise (CPX) tests were examined. CPX variables were compared among patients with reduced, mildly reduced, and preserved EF. Results: The CPX test responses of patients with mildly reduced EF were similar to those of patients with reduced or preserved EF; however, increases in systolic blood pressure during exercise differed significantly (32 ± 26, 50 ± 24, and 41 ± 31 mmHg, respectively; p = 0.016). Grip strength and an increase in systolic blood pressure during exercise were independently associated with peak oxygen uptake in patients with mildly reduced EF (β = 0.41, 0.35, respectively; p < 0.05). Conclusion: Measurements of grip strength and blood pressure during exercise are useful predictors of prognoses in patients with non-ischemic and mildly reduced EF.

Distinguishing exercise intolerance in early-stage pulmonary hypertension with invasive exercise hemodynamics: Rest VE /VCO2 and ETCO2 identify pulmonary vascular disease

BACKGROUND

Among subjects with exercise intolerance and suspected early-stage pulmonary hypertension (PH), early identification of pulmonary vascular disease (PVD) with noninvasive methods is essential for prompt PH management.

HYPOTHESIS

Rest gas exchange parameters (minute ventilation to carbon dioxide production ratio: VE /VCO2 and end-tidal carbon dioxide: ETCO2 ) can identify PVD in early-stage PH.

METHODS

We conducted a retrospective review of 55 subjects with early-stage PH (per echocardiogram), undergoing invasive exercise hemodynamics with cardiopulmonary exercise test to distinguish exercise intolerance mechanisms. Based on the rest and exercise hemodynamics, three distinct phenotypes were defined: (1) PVD, (2) pulmonary venous hypertension, and (3) noncardiac dyspnea (no rest or exercise PH). For all tests, *p < .05 was considered statistically significant.

RESULTS

The mean age was 63.3 ± 13.4 years (53% female). In the overall cohort, higher rest VE /VCO2 and lower rest ETCO2 (mm Hg) correlated with high rest and exercise pulmonary vascular resistance (PVR) (r ~ 0.5-0.6*). On receiver-operating characteristic analysis to predict PVD (vs. non-PVD) subjects with noninvasive metrics, area under the curve for pulmonary artery systolic pressure (echocardiogram) = 0.53, rest VE /VCO2  = 0.70* and ETCO2  = 0.73*. Based on this, optimal thresholds of rest VE /VCO2  > 40 mm Hg and rest ETCO2  < 30 mm Hg were applied to the overall cohort. Subjects with both abnormal gas exchange parameters (n = 12, vs. both normal parameters, n = 19) had an exercise PVR 5.2 ± 2.6* (vs. 1.9 ± 1.2), mPAP/CO slope with exercise 10.2 ± 6.0* (vs. 2.9 ± 2.0), and none included subjects from the noncardiac dyspnea group.

CONCLUSIONS

In a broad cohort of subjects with suspected early-stage PH, referred for invasive exercise testing to distinguish mechanisms of exercise intolerance, rest gas exchange parameters (VE /VCO2  > 40 mm Hg and ETCO2  < 30 mm Hg) identify PVD.

Exercise-induced pulmonary hypertension in HFpEF and HFrEF: Different pathophysiologic mechanism behind similar functional impairment

AIMS

Pathophysiological mechanisms behind cardio-pulmonary impairment in heart failure (HF) with reduced (HFrEF) and preserved (HFpEF) ejection fraction are likely different. We analysed them using combined cardiopulmonary-exercise stress echocardiography (CPET-ESE).

METHODS

We matched 1:1 subjects with HFrEF (n = 90) and HFpEF (n = 90) for age, sex, body mass index (BMI), peak oxygen consumption, and minute ventilation/carbon dioxide production slope. All patients underwent a symptom-limited graded ramp bicycle CPET-ESE compared with 40 age-, sex- and BMI-matched healthy controls.

RESULTS

During a median follow-up of 25 months, we observed 22 deaths and 80 HF hospitalisations, with similar distribution between HFpEF and HFrEF. Compared with HFrEF, HFpEF had a higher prevalence of metabolic syndrome (p = 0.02) with higher levels of high-sensitivity C-reactive protein and uric acid (p < 0.01). The multipoint mean pulmonary artery pressure/cardiac output (mPAP/CO) slope showed equally increased values in HFrEF and HFpEF (3.5 ± 1.8 and 3.7 ± 1.5 mmHg/L/min) compared with controls (1.8 ± 1.1 mmHg/L/min; p < 0.0001). During exercise, HFpEF displayed more adverse interaction of right ventricle-pulmonary artery (RV-PA; tricuspid annular plane systolic excursion/systolic pulmonary artery pressure: 0.40 ± 0.2 vs 0.47 ± 0.2 mm/mmHg in HFrEF; p < 0.01) and left atrium-left ventricle (LA-LV; LA reservoir strain/LV global longitudinal strain: 1.5 ± 0.8 vs 2.2 ± 1.1 in HFrEF; p < 0.01). The latter were independent predictors of mPAP/CO slope, along with hs-CRP (adjusted R2: 0.21; p < 0.0001).

CONCLUSION

Despite similar disease severity, HFpEF and HFrEF show different pathophysiological mechanisms. HFpEF is characterised by a worse LA-LV and RV-PA interaction than HFrEF, with more prevalent low-grade systemic inflammation. In HFpEF, these features may have a role in exercise-induced pulmonary hypertension.

Minute ventilation/carbon dioxide production in congenital heart disease

This review summarises various applications of how ventilatory equivalent (ventilatory efficiency or better still ventilatory inefficiency) and the minute ventilation (Vʹ_E)/carbon dioxide production (Vʹ_CO2) slope obtained from cardiopulmonary exercise testing (CPET) can be used in the diagnostic or prognostic workup of patients with congenital heart disease.

The field of congenital heart disease comprises not only a very heterogeneous patient group with various heart diseases, but also various conditions in different stages of repair, as well as the different residuals seen in long-term follow-up. As such, various physiologic disarrangements must be considered in the analysis of increased Vʹ_E/Vʹ_CO2 slope from CPET in patients with congenital heart disease. In addition to congestive heart failure (CHF), cyanosis, unilateral pulmonary stenosis and pulmonary hypertension (PH) provide the background for this finding. The predictive value of increased Vʹ_E/Vʹ_CO2 slope on prognosis seems to be more important in conditions where circulatory failure is associated with failure of the systemic ventricle. In cyanotic patients, those with Fontan circulation, or those with substantial mortality from arrhythmia, the impact of Vʹ_E/Vʹ_CO2 on prognosis is not that important.

Vʹ_E/Vʹ_CO2 elevation is a common finding in patients with congenital heart disease. It can be used as a sign for right-to-left shunting, unilateral pulmonary stenosis, pulmonary hypertension and circulatory failure. It is predictive for clinical worsening.https://bit.ly/33gj3NQ

Traditional markers of cardiac toxicity fail to detect marked reductions in cardiorespiratory fitness among cancer patients undergoing anti-cancer treatment

AIMS

Left ventricular ejection fraction (LVEF) is standard of care for evaluating chemotherapy-associated cardiotoxicity, although global longitudinal strain (GLS) offers advantages. However, neither change in LVEF or GLS has been associated with short-term symptoms, functional capacity, or long-term heart failure (HF) risk. We sought to determine whether an integrative measure of cardiovascular function (VO2peak) that is strongly associated with HF risk would be more sensitive to cardiac damage induced by cancer treatment than LVEF, GLS, or cardiac biomarkers.

METHODS AND RESULTS

Patients (n = 206, 53 ± 13 years, 35% male) scheduled to commence anti-cancer treatment completed assessment prior to, and within 6 months after therapy. Changes in echocardiographic measures of LV function (LVEF, GLS), cardiac biomarkers (troponin and BNP), and cardiorespiratory fitness (VO2peak) were measured. LV function was normal prior to treatment (LVEF 61 ± 5%; GLS -19.4 ± 2.1), but VO2peak was only 88 ± 26% of age-predicted. After treatment, VO2peak was reduced by 7 ± 15% (equivalent of 7 years normal ageing, P < 0.0001) and the rates of functional disability (defined as VO2peak ≤ 18 mL/min/kg) almost doubled (15% vs. 26%, P = 0.016). In contrast, small, reductions in LVEF (59 ± 5% vs. 58 ± 5%, P = 0.03) and GLS (-19.4 ± 2.1 vs. -18.9 ± 2.2, P = 0.002) and an increase in troponin levels (4.0 ± 6.9 vs. 26.4 ± 26.2 ng/mL, P < 0.0001) were observed.

CONCLUSION

Anti-cancer treatment is associated with marked reductions in functional capacity that occur independent of reductions in LVEF and GLS. The assessment of VO2peak prior to, and following treatment may be a more sensitive means of identifying patients at increased risk of HF.

Respiratory dyssynchrony is a predictor of prognosis in patients with hypertrophic non-obstructive cardiomyopathy

BACKGROUND

Respiratory dyssynchrony (RD) is a phenomenon that may be reflected by reduced breathing efficiency (CO₂ output relative to minute ventilation, V̇E/V̇CO₂ slope) or by Exercise oscillatory ventilation (EOV). Low breathing efficiency and EOV indicate a worse prognosis in chronic heart failure patients with reduced ejection fraction (HFrEF). However, only little is known about their role in other forms of structural myocardial diseases. In this study, we assessed the prognostic impact of RD in hypertrophic non-obstructive cardiomyopathy (HNCM) as a subgroup of patients with heart failure and preserved ejection fraction (HFpEF).

METHODS AND RESULTS

We selected n = 132 HNCM patients (pts) who underwent cardiopulmonary exercise testing (CPET) during baseline assessment. The average follow-up was 4.3 ± 3.6 years. The primary endpoint was a composite of death, heart transplantation (HTX), and implantation of a ventricular assist device (VAD). Respiratory dyssynchrony, as measured by EOV, was recorded in 18 pts. (14%), and as measured by a V̇E/V̇CO₂ relationship of higher than 34 in 34 pts. (26%). In total, 22 (16.7%) pts. met the endpoint. Multivariate COX regression Analysis were made for EOV, V̇E/V̇CO₂ and the combination of EOV andV̇E/V̇CO₂. All parameters correlated significantly with the endpoint: EOV (hazard ratio [HR]: 3.7; p = 0.006), V̇E/V̇CO₂ > 34 (HR: 5.6; p = 0.001) and EOV andV̇E/V̇CO₂: (HR: 6.1; p ≤ 0.001).

CONCLUSION

This is the first study to demonstrate the prognostic impact of RD on pts. with HNCM, and to investigate EOV as a novel factor to aid risk stratification in HNCM.

Left atrial function and maximal exercise capacity in heart failure with preserved and mid-range ejection fraction

Aims

Exercise intolerance is the leading manifestation of heart failure with preserved or mid‐range ejection fraction (HFpEF or HFmrEF), and left atrial (LA) function might contribute to modulating left ventricular filling and pulmonary venous pressures. We aim to assess the association between LA function and maximal exercise capacity in patients with HFpEF or HFmrEF.

Methods and results

Sixty‐five patients, prospectively enrolled in the German HFpEF Registry, were analysed. Inclusion criteria were New York Heart Association functional class ≥ II, left ventricular ejection fraction > 40%, structural heart disease or diastolic dysfunction, and elevated levels of N terminal pro brain natriuretic peptide (NT‐proBNP). LA function was evaluated through speckle‐tracking echocardiography by central reading in the Charité Academic Echocardiography core lab. All patients underwent maximal cardiopulmonary exercise test and were classified according to a peak VO₂ cut‐off of prognostic value (14 mL/kg/min). NT‐pro‐BNP was measured. Twenty‐nine patients (45%) reached a peak VO₂ < 14 mL/kg/min (mean value 12.4 ± 1.5) and 36 patients (55%) peak VO₂ ≥ 14 mL/kg/min (mean value 19.4 ± 3.9). There was no significant difference in left ventricular ejection fraction (60 ± 9 vs. 59 ± 8%), left ventricular mass (109 ± 23 vs. 112 ± 32 g/m²), LA volume index (45 ± 17 vs. 47 ± 22 mL/m²), or E/e´ (13.1 ± 4.7 vs. 13.0 ± 6.0) between these groups. In contrast, all LA strain measures were impaired in patients with lower peak VO₂ (reservoir strain 14 ± 5 vs. 21 ± 9%, P = 0.002; conduit strain 9 ± 2 vs. 13 ± 4%, P = 0.001; contractile strain 7 ± 4 vs. 11 ± 6%, P = 0.02; reported lower limits of normality for LA reservoir, conduit and contractile strains: 26.1%, 12.0%, and 7.7%). In linear regression analysis, lower values of LA reservoir strain were associated with impaired peak VO₂ after adjustment for age, sex, body mass index, heart rhythm (sinus/AFib), and log‐NTproBNP [β 0.29, 95% confidence interval (CI) 0.02–0.30, P = 0.02], with an odds ratio 1.22 (95% CI 1.05–1.42, P = 0.01) for peak VO₂ < 14 mL/kg/min for LA reservoir strain decrease after adjustment for these five covariates. Adding left ventricular ejection fraction, it did not influence the results. On the other hand, the addition of LA strain to the adjustment parameters alone described above provided a significant increase of the predictive value for lower peak VO₂ values (R² 0.50 vs. 0.45, P = 0.02). With receiver operating characteristic curve analysis, we identified LA reservoir strain < 22% to have 93% sensitivity and 49% specificity in predicting peak VO₂ < 14 mL/kg/min. Using this cut‐off, LA reservoir strain < 22% was associated with peak VO₂ < 14 mL/kg/min in logistic regression analysis after comprehensive adjustment for age, sex, body mass index, heart rhythm, and log‐NTproBNP [odds ratio 95% CI 10.4 (1.4–74), P = 0.02].

Conclusions

In this HFpEF and HFmrEF cohort, a reduction in LA reservoir strain was a sensible marker of decreased peak exercise capacity. Therefore, LA reservoir strain might be of clinical value in predicting exercise capacity in patients with HFpEF or HFmrEF.

Left ventricular concentric remodeling and impaired cardiorespiratory fitness in patients with heart failure and preserved ejection fraction

BACKGROUND

Left ventricular (LV) concentric remodeling refers to a process by which increased LV relative wall thickness alters myocardial geometry, resulting in reduced LV end-diastolic volume (LVEDV) and stroke volume (SV). While the degree of concentric remodeling is a negative prognostic factor in heart failure with preserved ejection fraction (HFpEF), it is not known how it contributes to cardiorespiratory fitness (CRF).

METHODS

We performed a retrospective analysis of patients with HFpEF who underwent treadmill single-photon emission computed tomography myocardial perfusion imaging (SPECT-MPI) and cardiopulmonary exercise testing (CPX). From exercise SPECT-MPI, we recorded postexercise LVEDVi, LVESVi, SVi, LVEF, the presence and extent of perfusion defects, and perfusion reversibility. Peak oxygen consumption (VO<inf>2</inf>), the oxygen uptake efficiency slope (OUES), oxygen (O<inf>2</inf>) pulse, ventilatory efficiency (V<inf>E</inf>/VCO<inf>2</inf> slope), ventilatory anaerobic threshold, respiratory exchange ratio, exercise time, and maximum heart rate were obtained from CPX. Data are expressed as mean (±standard deviation). Univariate and multivariate linear regression was performed.

RESULTS

We identified 23 subjects who had completed both an exercise SPECT-MPI and a CPX. Patients were more commonly women (83%), black (65%), middle age (50 [±7.3] years), and obese (Body Mass Index [BMI] 39.7 [±6.0] kg/m²). Greater LVEDVi and LVESVi correlated positively with peak VO<inf>2</inf> (R=+0.648, P=0.001; R=+0.601, P=0.002), O<inf>2</inf> pulse (R=+0.686, P<0.001; R=+0.625, P=0.001) and OUES (R=+0.882, P<0.001; R=+0.779, P<0.001). The LVEF correlated inversely with peak VO<inf>2</inf> and OUES (R=-0.450, P=0.031; R=-0.485, P=0.035). Perfusion defect area, grade of severity, and presence of reversibility were not associated with CRF variables.

CONCLUSIONS

Postexercise reduced LV volumes correlate with measures of impaired CRF in patients with HFpEF, thus supporting a pathophysiologic role of concentric remodeling in impaired CRF in HFpEF.

High-intensity interval training is effective and superior to moderate continuous training in patients with heart failure with preserved ejection fraction: A randomized clinical trial

BACKGROUND

Heart failure with preserved ejection fraction (HFpEF) is a prevalent syndrome, with exercise intolerance being one of its hallmarks, contributing to worse quality of life and mortality. High-intensity interval training is an emerging training option, but its efficacy in HFpEF patients is still unknown.

DESIGN

Single-blinded randomized clinical trial.

METHODS

Single-blinded randomized clinical trial with exercise training 3 days per week for 12 weeks. HFpEF patients were randomly assigned to high-intensity interval training or moderate continuous training. At baseline and after 12 week follow-up, patients underwent clinical assessment, echocardiography and cardiopulmonary exercise testing (CPET).

RESULTS

Mean age was 60 ± 9 years and 63% were women. Both groups (N = 19) showed improved peak oxygen consumption (VO₂), but high-intensity interval training patients (n = 10) had a significantly higher increase, of 22%, compared with 11% in the moderate continuous training (n = 9) individuals (3.5 (3.1 to 4.0) vs. 1.9 (1.2 to 2.5) mL·kg^-1·min^-1, p < 0.001). Ventilatory efficiency and other CPET measures, as well as quality of life score, increased equally in the two groups. Left ventricular diastolic function also improved with training, reflected by a significant reduction in E/e' ratio by echocardiography (-2.6 (-4.3 to -1.0) vs. -2.2 (-3.6 to -0.9) for high-intensity interval training and moderate continuous training, respectively; p < 0.01). There were no exercise-related adverse events.

CONCLUSIONS

This randomized clinical trial provided evidence that high-intensity interval training is a potential exercise modality for HFpEF patients, being more effective than moderate continuous training in improving peak VO₂. However, the two strategies were equally effective in improving ventilatory efficiency and other CPET parameters, quality of life score and diastolic function after 3 months of training.

Exercise Ventilatory Efficiency in Older and Younger Heart Failure Patients With Preserved Ejection Fraction

BACKGROUND

Patients with heart failure with preserved ejection fraction (HFpEF) exhibit pulmonary abnormalities, but the studies to date have reported wide variability in the ventilatory equivalent for carbon dioxide (V̇_E/V̇CO₂) slope. It is possible that aging may contribute to that variability. We sought to compare ventilatory efficiency and its components in older and younger HFpEF patients during exercise.

METHODS AND RESULTS

Eighteen older (O; 80 ± 4 y) and 19 younger (Y; 59 ± 7 y) HFpEF patients performed cardiopulmonary exercise testing to volitional fatigue. Measurements of arterial blood gases were used to derive V_D/V_T, dead space ventilation, and alveolar ventilation. V̇_E/V̇CO₂ slope was greater in older compared with younger HFpEF patients (O 36 ± 7vs Y 31 ± 7; P = .04). At peak exercise, older HFpEF exhibited greater V_D/V_T compared with younger HFpEF (O 0.37 ± 0.10vs Y 0.28 ± 0.10; P < .01), whereas PaCO₂ was not different between groups (P = .58). V̇_E and alveolar ventilation were similar (P > .23), but dead space ventilation was greater in older compared with younger HFpEF at peak exercise (P = .04).

CONCLUSIONS

Older HFpEF patients exhibit greater ventilatory inefficiency resulting from elevated physiologic dead space during peak exercise compared with younger HFpEF patients. These results suggest that aging can worsen the pathophysiologic mechanisms underlying ventilatory efficiency during exercise in HFpEF.

Relation of Hepatic Fibrosis in Nonalcoholic Fatty Liver Disease to Left Ventricular Diastolic Function and Exercise Tolerance

The purpose of this study was to determine the relation between liver histology, exercise tolerance, and diastolic function in patients with nonalcoholic fatty liver disease (NAFLD). Myocardial remodeling and diastolic dysfunction have been associated with NAFLD. However, its physiological impact and relationship to the histological severity of NAFLD is not known. Cardiopulmonary exercise testing and stress echocardiography was performed in subjects with biopsy-confirmed NAFLD. Maximal aerobic exercise capacity (peak oxygen consumption [VO2]) was related to diastolic function (mitral annulus Doppler velocity e' and ratio of early diastolic filling pressure [E] to e' [E/e']) at rest and peak exercise. Autonomic dysfunction was determined from heart rate recovery after exercise. Independent predictors of cardiac function and exercise capacity were identified by multivariable regression. Thirty-six subjects (nonalcoholic fatty liver [NAFL  =  15], nonalcoholic steatohepatitis [NASH  =  21]) were enrolled. NASH was associated with impaired exercise capacity compared with NAFL (median peak VO2 17.0 [15.4, 18.9] vs 19.9 [17.4, 26.0], p  =  001); pVO2 declined with increasing fibrosis (F0  =  22.5, F1  =  19.9, F2  =  19.0, F3  =  16.6 ml·kg-1·min-1; p  =  0.01). Similarly, E/e' during exercise increased progressively with increasing fibrosis (F0  =  5.6, F1  =  6.5, F2  =  8.7, F3  =  9.8; P  =  0.02). Finally, heart rate recovery, a marker of autonomic function, was blunted in those with higher fibrosis stages (F0  =  25 [20, 30], F1  =  23 [17.5, 27.0], F2  =  17 [11.8, 21.5], F3  =  11 [8.5, 18.0] beats per minute; p <0.01). Fibrosis was an independent predictor of these functional outcomes. In conclusion, NASH is associated with impaired exercise capacity and diastolic dysfunction compared with NAFL. The severity of impairment is directly related to the severity of fibrosis stage in precirrhotic stages of NAFLD.

Role of Advanced Testing: Invasive Hemodynamics, Endomyocardial Biopsy, and Cardiopulmonary Exercise Testing

Hypertrophic cardiomyopathy affects 0.5% of the population. Advanced testing is considered, including cardiac catheterization, endomyocardial biopsy, and cardiopulmonary exercise testing. Right and left heart catheterization provides essential hemodynamic data, identifies patients who might benefit from septal reduction therapy, and assesses for comorbidities. Pathologic analysis reveals ventricular hypertrophy, myocardial disarray, and endocardial and interstitial fibrosis. Routine endomyocardial biopsy is not recommended unless other conditions that cause hypertrophy need to be ruled out. Cardiopulmonary exercise testing provides useful physiologic data, allows monitoring of the response to medication and surgical interventions, estimates prognosis, and guides referral for orthotopic heart transplantation.

Exercise ventilatory inefficiency in heart failure and chronic obstructive pulmonary disease

BACKGROUND

Dyspnea on exertion is common to both heart failure (HF) and chronic obstructive pulmonary disease (COPD), and it is important to discriminate whether symptoms are caused by HF or COPD in clinical practice. The ventilatory equivalent for carbon dioxide (V̇_E/V̇CO₂) slope and V̇_E intercept (a reflection of pulmonary dead space) are two candidate non-invasive indices that could be used for this purpose. Thus, we compared non-invasive indexes of ventilatory efficiency in patients with HF and preserved or reduced ejection fraction (HFpEF and HFrEF, respectively) or COPD.

METHODS

Patients with HFpEF (n = 21), HFrEF (n = 20), and COPD (n = 22) patients performed cardiopulmonary exercise testing to volitional fatigue. V̇_E and gas exchange were measured via breath-by-breath open circuit spirometry. All data from rest to peak exercise were used to calculate V̇_E/V̇CO₂ slope and V̇_E intercept using linear regression. Receiver operating characteristic (ROC) curves were constructed to determine optimized cutoffs for V̇_E/V̇CO₂ slope and V̇_E intercept to discriminate HFpEF and HFrEF from COPD.

RESULTS

HFrEF patients had a greater V̇_E/V̇CO₂ slope than HFpEF and COPD patients (HFrEF: 40 ± 9; HFpEF: 32 ± 7; COPD: 32 ± 7) (p < 0.01). COPD patients had a greater V̇_E intercept than HFpEF and HFrEF patients (COPD: 3.32 ± 1.66; HFpEF: 0.77 ± 1.23; HFrEF: 1.28 ± 1.19 L/min) (p < 0.01). A V̇_E intercept of 2.64 L/min discriminated COPD from HF patients (AUC: 0.88, p < 0.01), while V̇_E/V̇CO₂ slope did not (p = 0.11).

CONCLUSION

These findings demonstrate that V̇_E intercept, not V̇_E/V̇CO₂ slope, may discriminate COPD from both HFpEF and HFrEF patients.

Hemodynamic Correlates and Diagnostic Role of Cardiopulmonary Exercise Testing in Heart Failure With Preserved Ejection Fraction

OBJECTIVES

This study sought to define the invasive hemodynamic correlates of peak oxygen consumption (Vo2) in both supine and upright exercise in heart failure with preserved ejection fraction (HFpEF) and evaluate its diagnostic role as a method to discriminate HFpEF from noncardiac etiologies of dyspnea (NCD).

BACKGROUND

Peak Vo2 is depressed in patients with HFpEF. The hemodynamic correlates of reduced peak Vo2 and its role in the clinical evaluation of HFpEF are unclear.

METHODS

Consecutive patients with dyspnea and normal EF (N = 206) undergoing both noninvasive upright and invasive supine cardiopulmonary exercise testing were examined. Patients with invasively verified HFpEF were compared with those with NCD.

RESULTS

Compared with NCD (n = 72), HFpEF patients (n = 134) displayed lower peak Vo2 during upright and supine exercise. Left heart filling pressures during exercise were inversely correlated with peak Vo2 in HFpEF, even after accounting for known determinants of O2 transport according to the Fick principle. Very low upright peak Vo2 (<14 ml/kg/min) discriminated HFpEF from NCD with excellent specificity (91%) but poor sensitivity (50%). Preserved peak Vo2 (>20 ml/kg/min) excluded HFpEF with high sensitivity (90%) but had poor specificity (49%). Intermediate peak Vo2 cutoff points were associated with substantial overlap between cases and NCD.

CONCLUSIONS

Elevated cardiac filling pressure during exercise is independently correlated with reduced exercise capacity in HFpEF, irrespective of body position, emphasizing its importance as a novel therapeutic target. Noninvasive cardiopulmonary testing discriminates HFpEF and NCD at high and low values, but additional testing is required for patients with intermediate peak Vo2.

Cardiopulmonary Exercise Test in Hypertrophic Cardiomyopathy

Understanding the functional limitation in hypertrophic cardiomyopathy, the most common inherited heart disease, is challenging. In addition to the occurrence of disease-related complications, several factors are potential determinants of exercise limitation, including left ventricular hypertrophy, myocardial fiber disarray, left ventricular outflow tract obstruction, microvascular ischemia, and interstitial fibrosis. Furthermore, drugs commonly used in the daily management of these patients may interfere with exercise capacity, especially those with a negative chronotropic effect. Cardiopulmonary exercise testing can safely and objectively evaluate the functional capacity of these patients and help the physician in understanding the mechanisms that underlie this limitation. Features that reduce exercise capacity may predict progression to heart failure in these patients and even the risk of sudden cardiac death.

Exercise testing in heart failure: a contemporary discussion in an era of novel diagnostic techniques and biomarkers

PURPOSE OF REVIEW

The purpose of this review is to highlight recent advances in the field of exercise testing for patients with heart failure.

RECENT FINDINGS

The importance of assessment of cardiorespiratory fitness (CRF) and exercise testing in heart failure is highlighted in the consensus recommendation of the American Heart Association. Contemporary studies have validated the independent and incremental strength of CRF metrics in patients with heart failure and coronary artery disease. The use of respiratory gas analysis and imaging or hemodynamics during physical exercise is feasible and results in high prognostic utility across the continuum of heart failure. Understanding how CRF metrics complement existing and novel biomarkers and risk scores is an emerging subject of scientific inquiry.

SUMMARY

In the current era of personalized medicine, integrating CRF, imaging and circulating biomarkers will allow us to further develop individualized strategies for improving outcome in patients with heart failure.

Prognostic value of cardiopulmonary exercise testing in heart failure with preserved ejection fraction. The Henry Ford HospITal CardioPulmonary EXercise Testing (FIT-CPX) project

BACKGROUND

Although cardiopulmonary exercise (CPX) testing in patients with heart failure and reduced ejection fraction is well established, there are limited data on the value of CPX variables in patients with HF and preserved ejection fraction (HFpEF). We sought to determine the prognostic value of select CPX measures in patients with HFpEF.

METHODS

This was a retrospective analysis of patients with HFpEF (ejection fraction ≥ 50%) who performed a CPX test between 1997 and 2010. Selected CPX variables included peak oxygen uptake (VO2), percent predicted maximum oxygen uptake (ppMVO2), minute ventilation to carbon dioxide production slope (VE/VCO2 slope) and exercise oscillatory ventilation (EOV). Separate Cox regression analyses were performed to assess the relationship between each CPX variable and a composite outcome of all-cause mortality or cardiac transplant.

RESULTS

We identified 173 HFpEF patients (45% women, 58% non-white, age 54 ± 14 years) with complete CPX data. During a median follow-up of 5.2 years, there were 42 deaths and 5 cardiac transplants. The 1-, 3-, and 5-year cumulative event-free survival was 96%, 90%, and 82%, respectively. Based on the Wald statistic from the Cox regression analyses adjusted for age, sex, and β-blockade therapy, ppMVO2 was the strongest predictor of the end point (Wald χ(2) = 15.0, hazard ratio per 10%, P < .001), followed by peak VO2 (Wald χ(2) = 11.8, P = .001). VE/VCO2 slope (Wald χ(2)= 0.4, P = .54) and EOV (Wald χ(2) = 0.15, P = .70) had no significant association to the composite outcome.

CONCLUSION

These data support the prognostic utility of peak VO2 and ppMVO2 in patients with HFpEF. Additional studies are needed to define optimal cut points to identify low- and high-risk patients.

An overview of the applied definitions and diagnostic methods to assess exercise oscillatory ventilation--a systematic review

The variable "exercise oscillatory ventilation" (EOV), assessed during cardiopulmonary exercise test (CPET), recently became a fundamental prognostic parameter in patients with heart failure. In literature, various definitions are suggested, but an uniformly accepted description to identify EOV still lacks. We performed a systematic review of the literature in order to determine the different definitions and diagnostic techniques to assess EOV. A systematic search strategy was established and executed in seven databases (PubMed, Google Scholar, Cochrane Clinical Trials, Science Direct, Pedro, Web Of Science library and Medline (Ovid)) resulting in 605 citations after de-duplication. Full-text articles (n=124) were assessed for eligibility, resulting in 75 citations. The review accounted 17,440 patients of whom 4,638 subjects presented EOV. Seven studies described EOV in a non-heart failure population accounting 168 EOV subjects. The definitions could be categorized in nine subdivisions of which four (n=43) referred to an original description. The other subdivisions were combinations of the original definitions (n=11), quantifications (n=4), computational (n=3), vaguely described (n=8) or not defined (n=6). Symptom limited maximal exercise tests were conducted to assess EOV, however the modes, protocols, software and data sampling were divers. Heterogeneity in the numerous definitions to identify EOV and the vaguely described assessment methods are hindering the evolution to a standardized uniformly accepted definition and technique to identify this abnormal breathing pattern. Unity in definition and international adopted assessment is warranted to strengthen its validity as a prognostic marker and could promote communication. It may facilitate clinical trials on pathophysiology and origin of EOV.

Pathophysiology and clinical relevance of pulmonary remodelling in pulmonary hypertension due to left heart diseases

Pulmonary hypertension (PH) in left heart disease, classified as group II, is the most common form of PH that occurs in approximately 60% of cases of reduced and preserved left ventricular ejection fraction. Although relatively much is known about hemodynamic stages (passive or reactive) and their consequences on the right ventricle (RV) there is no consensus on the best hemodynamic definition of group II PH. In addition, the main pathways that lead to lung capillary injury and impaired biology of small artery remodelling processes are largely unknown. Typical lung manifestations of an increased pulmonary pressure and progressive RV-pulmonary circulation uncoupling are an abnormal alveolar capillary gas diffusion, impaired lung mechanics (restriction), and exercise ventilation inefficiency. Of several classes of pulmonary vasodilators currently clinically available, oral phosphodiesterase 5 inhibition, because of its strong selectivity for targeting the cyclic guanosine monophosphate pathway in the pulmonary circulation, is increasingly emerging as an attractive opportunity to reach hemodynamic benefits, reverse capillary injury, and RV remodelling, and improve functional capacity. Guanylate cyclase stimulators offer an additional intriguing opportunity but the lack of selectivity and systemic effects might preclude some of the anticipated benefits on the pulmonary circulation. Future trials will determine whether new routes of pharmacologic strategy aimed at targeting lung structural and vascular remodelling might affect morbidity and mortality in left heart disease populations. We believe that this therapeutic goal rather than a pure hemodynamic effect might ultimately emerge as an important challenge for the clinician.