Ventilatory efficiency and resting hemodynamics in hypertrophic cardiomyopathy

The ventilatory efficiency parameters outperform peak oxygen consumption in monitoring the therapy effects in patients with hypertrophic cardiomyopathy

AIM

We sought the cardiopulmonary exercise testing (CPET) parameter that most accurately reflected therapeutic efficacy in patients with hypertrophic cardiomyopathy (HCM).

METHODS

Well-being questionnaire, N-terminal brain natriuretic peptide measurements, echocardiography, and CPET were performed in patients with symptomatic non-obstructive HCM during phase II, randomized, open-label multicentre study, before and after 16 weeks of traditional or sacubitril/valsartan treatment. Patients were followed 36 months after the initial CPET. Primary endpoints were changes in: 1) peak oxygen consumption (VO2); 2) VO2 at anaerobic threshold (AT); 3) oxygen pulse; 4) minute ventilation (VE)/carbon-dioxide (CO2) production slope; 5) VE/VCO2 at AT (VE/VCO2_AT); 6) VE/VCO2 nadir; 7) VE/VCO2 intercept; and 8) partial end-tidal pressure of carbon-dioxide (PETCO2) change during CPET.

RESULTS

Of 115 screened patients, 61 (52 ± 14 years, 43 % women) were included. Within subject therapy effects were detected only by the VE/VCO2 intercept and PETCO2 change, whereas the differences between medical regimens were detected by differences in VE/VCO2 nadir and VE/VCO2_AT changes after the treatment. The best predictors of the change in well-being were left ventricular outflow tract maximal gradient and VE/VCO2 intercept (B = 0.41,0.36; SE = 0.16,0.30; CI = 0.14-0.79, 0.15-1.14; p = 0.006,0.016, respectively). Adverse cardiac events were best predicted by the initial VE/VCO2 nadir.

CONCLUSION

Ventilatory efficiency parameters outperform peak VO2 in gauging therapy effects in patients with HCM.

New atrio-ventricular indices derived from conventional cine MRI correlate with functional capacity in patients with asymptomatic primary mitral regurgitation

Mitral regurgitation (MR) is associated with morphological and functional alterations of left atrium (LA) and ventricle (LV), possibly inducing LA-LV misalignment. We aimed to: (1) characterize angulation between LA and mitral annulus from conventional cine MRI data and feature-tracking (FT) contours, (2) assess their associations with functional capacity in MR patients, as assessed by oxygen consumption (peak-VO2) and minute ventilation to carbon dioxide production (VE/VCO2) slope, in comparison with MRI LA/LV strain indices. Thirty-two asymptomatic primary MR patients (56 [40; 66] years, 12 women) underwent cardiac MRI resulting in LA/LV conventional FT-derived strain indices. Then, end-diastolic angles were derived from FT LA contours: (1) α, centered on the LA centre of mass and defined by mitral valve extremities, (2) γ, centered on the mitral ring anterior/lateral side, and defined by LA centre and the other extremity of the mitral ring. Cardiopulmonary exercise testing with simultaneous echocardiography were also performed; peak-VO2 and VE/VCO2 slope were measured. While peak-VO2 and VE/VCO2 slope were not correlated to LA/LV strains, they were significantly associated with angles (α: r = 0.50, p = 0.003 and r = - 0.52, p = 0.003; γ: r = - 0.53, p = 0.002 and r = 0.52, p = 0.003; respectively), independently of age and gender (R2 ≥ 0.29, p ≤ 0.03). In primary MR, the new LA/mitral annulus angles, computed directly from standard-of-care MRI, are better correlated to exercise tolerance than conventional LA/LV strain.

Safety and Efficacy of Metabolic Modulation With Ninerafaxstat in Patients With Nonobstructive Hypertrophic Cardiomyopathy

BACKGROUND

In nonobstructive hypertrophic cardiomyopathy (nHCM), there are no approved medical therapies. Impaired myocardial energetics is a potential cause of symptoms and exercise limitation. Ninerafaxstat, a novel cardiac mitotrope, enhances cardiac energetics.

OBJECTIVES

This study sought to evaluate the safety and efficacy of ninerafaxstat in nHCM.

METHODS

Patients with hypertrophic cardiomyopathy and left ventricular outflow tract gradient <30 mm Hg, ejection fraction ≥50%, and peak oxygen consumption <80% predicted were randomized to ninerafaxstat 200 mg twice daily or placebo (1:1) for 12 weeks. The primary endpoint was safety and tolerability, with efficacy outcomes also assessed as secondary endpoints.

RESULTS

A total of 67 patients with nHCM were enrolled at 12 centers (57 ± 11.8 years of age; 55% women). Serious adverse events occurred in 11.8% (n = 4 of 34) in the ninerafaxstat group and 6.1% (n = 2 of 33) of patients in the placebo group. From baseline to 12 weeks, ninerafaxstat was associated with significantly better VE/Vco2 (ventilatory efficiency) slope compared with placebo with a least-squares (LS) mean difference between the groups of -2.1 (95% CI: -3.6 to -0.6; P = 0.006), with no significant difference in peak VO2 (P = 0.90). The Kansas City Cardiomyopathy Questionnaire Clinical Summary Score was directionally, though not significantly, improved with ninerafaxstat vs placebo (LS mean 3.2; 95% CI: -2.9 to 9.2; P = 0.30); however, it was statistically significant when analyzed post hoc in the 35 patients with baseline Kansas City Cardiomyopathy Questionnaire Clinical Summary Score ≤80 (LS mean 9.4; 95% CI: 0.3-18.5; P = 0.04).

CONCLUSIONS

In symptomatic nHCM, novel drug therapy targeting myocardial energetics was safe and well tolerated and associated with better exercise performance and health status among those most symptomatically limited. The findings support assessing ninerafaxstat in a phase 3 study.

Effects of Mavacamten on Measures of Cardiopulmonary Exercise Testing Beyond Peak Oxygen Consumption: A Secondary Analysis of the EXPLORER-HCM Randomized Trial

Importance

Mavacamten, a cardiac myosin inhibitor, improved peak oxygen uptake (pVO2) in patients with symptomatic obstructive hypertrophic cardiomyopathy (HCM) in the EXPLORER-HCM study. However, the full extent of mavacamten's effects on exercise performance remains unclear.

Objective

To investigate the effect of mavacamten on exercise physiology using cardiopulmonary exercise testing (CPET).

Design, Setting, and Participants

Exploratory analyses of the data from the EXPLORER-HCM study, a randomized, double-blind, placebo-controlled, phase 3 trial that was conducted in 68 cardiovascular centers in 13 countries. In total, 251 patients with symptomatic obstructive HCM were enrolled.

Interventions

Patients were randomly assigned in a 1:1 ratio to mavacamten or placebo.

Main Outcomes and Measures

The following prespecified exploratory cardiovascular and performance parameters were assessed with a standardized treadmill or bicycle ergometer test protocol at baseline and week 30: carbon dioxide output (VCO2), minute ventilation (VE), peak VE/VCO2 ratio, ventilatory efficiency (VE/VCO2 slope), peak respiratory exchange ratio (RER), peak circulatory power, ventilatory power, ventilatory threshold, peak metabolic equivalents (METs), peak exercise time, partial pressure of end-tidal carbon dioxide (PETCO2), and VO2/workload slope.

Results

Two hundred fifty-one patients were enrolled. The mean (SD) age was 58.5 (11.9) years and 59% of patients were male. There were significant improvements with mavacamten vs placebo in the following peak-exercise CPET parameters: peak VE/VCO2 ratio (least squares [LS] mean difference, -2.2; 95% CI, -3.05 to -1.26; P < .001), peak METs (LS mean difference, 0.4; 95% CI, 0.17-0.60; P < .001), peak circulatory power (LS mean difference, 372.9 mL/kg/min × mm Hg; 95% CI, 153.12-592.61; P = .001), and peak PETCO2 (LS mean difference, 2.0 mm Hg; 95% CI, 1.12-2.79; P < .001). Mavacamten also improved peak exercise time compared with placebo (LS mean difference, 0.7 minutes; 95% CI, 0.13-1.24; P = .02). There was a significant improvement in nonpeak-exercise CPET parameters, such as VE/VCO2 slope (LS mean difference, -2.6; 95% CI, -3.58 to -1.52; P < .001) and ventilatory power (LS mean difference, 0.6 mm Hg; 95% CI, 0.29-0.90; P < .001) favoring mavacamten vs placebo.

Conclusions and Relevance

Mavacamten improved a range of CPET parameters beyond pVO2, indicating consistent and broad benefits on maximal exercise capacity. Although improvements in peak-exercise CPET parameters are clinically meaningful, the favorable effects of mavacamten on submaximal exertional tolerance provide further insights into the beneficial impact of mavacamten in patients with obstructive HCM.

Trial Registration

ClinicalTrials.gov Identifier: NCT03470545.

Correlation of Hemodynamic and Respiratory Parameters in Invasive Cardiopulmonary Exercise Testing (iCPET)

Background: Invasive cardiopulmonary exercise testing (iCPET) is an integral part in the advanced diagnostic workup of pulmonary hypertension (PH). Our study evaluated the relation between hemodynamic and respiratory parameters at two different resting conditions and two defined low exercise levels with a close synchronization of measurements in a broad variety of dyspnea patients. Subjects and methods: We included 146 patients (median age 69 years, range 22 to 85 years, n = 72 female) with dyspnea of uncertain origin. Invasive hemodynamic and gas exchange parameters were measured at rest, 45° upright position, unloaded cycling, 25 and 50 W exercise. All measurements were performed in a single RHC procedure. Results: Oxygen uptake (VO2/body mass) correlated significantly with cardiac index (all p ≤ 0.002) at every resting and exercise level and with every method of cardiac output measurement (thermodilution, method of Fick). Mean pulmonary arterial pressure (PAPmean) correlated with all respiratory parameters (respiratory rate, partial end-tidal pressures of oxygen and carbon dioxide [petCO2 and petO2], ventilation/carbon dioxide resp. oxygen ratio [VE/VCO2, VE/VO2], and minute ventilation [VE], all p < 0.05). These correlations improved with increasing exercise levels from rest via unloaded cycling to 25 W. There was no correlation with right atrial or pulmonary arterial wedge pressure. Summary: In dyspnea patients of different etiologies, the cardiac index is closely linked to VO2 at every level of rest and submaximal exercise. PAPmean is the only pressure that correlates with different respiratory parameters, but this correlation is highly significant and stable at rest, unloaded cycling and at 25 W.

[Invasive Cardiopulmonary Exercise Testing: A Review]

Right heart catheterization (RHC) is the internationally standardized reference method for measuring pulmonary hemodynamics under resting conditions. In recent years, increasing efforts have been made to establish the reliable assessment of exercise hemodynamics as well, in order to obtain additional diagnostic and prognostic data. Furthermore, cardiopulmonary exercise testing (CPET), as the most comprehensive non-invasive exercise test, is increasingly performed in combination with RHC providing detailed pathophysiological insights into the exercise response, so-called invasive cardiopulmonary exercise testing (iCPET).In this review, the accumulated experience with iCPET is presented and methodological details are discussed. This complex examination is especially helpful in differentiating the underlying causes of unexplained dyspnea. In particular, early forms of cardiac or pulmonary vascular dysfunction can be detected by integrated analysis of hemodynamic as well as ventilatory and gas exchange data. It is expected that with increasing validation of iCPET parameters, a more reliable differentiation of normal from pathological stress reactions will be possible.

Cardiopulmonary Exercise Test in Patients with Hypertrophic Cardiomyopathy: A Systematic Review and Meta-Analysis

BACKGROUND

Patients with chronic diseases frequently adapt their lifestyles to their functional limitations. Functional capacity in Hypertrophic Cardiomyopathy (HCM) can be assessed by stress testing. We aim to review and analyze the available data from the literature on the value of Cardiopulmonary Exercise Test (CPET) in HCM. Objective measurements from CPET are used for evaluation of patient response to traditional and new developing therapeutic measurements.

METHODS

A systematic review of the literature was conducted in PubMed, Web of Science and Cochrane in Mar-20. The original search yielded 2628 results. One hundred and two full texts were read after the first screening, of which, 69 were included for qualitative synthesis. Relevant variables to be included in the review were set and 17 were selected, including comorbidities, body mass index (BMI), cardiac-related symptoms, echocardiographic variables, medications and outcomes.

RESULTS

Study sample consisted of 69 research articles, including 11,672 patients (48 ± 14 years old, 65.9%/34.1% men/women). Treadmill was the most common instrument employed (n = 37 studies), followed by upright cycle-ergometer (n = 16 studies). Mean maximal oxygen consumption (VO2max) was 22.3 ± 3.8 mL·kg^-1·min^-1. The highest average values were observed in supine and upright cycle-ergometer (25.3 ± 6.5 and 24.8 ± 9.1 mL·kg^-1·min^-1; respectively). Oxygen consumption in the anaerobic threshold (ATVO2) was reported in 18 publications. Left ventricular outflow tract gradient (LVOT) > 30 mmHg was present at baseline in 31.4% of cases. It increased to 49% during exercise. Proportion of abnormal blood pressure response (ABPRE) was higher in severe (>20 mm) vs. mild hypertrophy groups (17.9% vs. 13.6%, p < 0.001). Mean VO2max was not significantly different between severe vs. milder hypertrophy, or for obstructive vs. non-obstructive groups. Occurrence of arrhythmias during functional assessment was higher among younger adults (5.42% vs. 1.69% in older adults, p < 0.001). Twenty-three publications (9145 patients) evaluated the prognostic value of exercise capacity. There were 8.5% total deaths, 6.7% cardiovascular deaths, 3.0% sudden cardiac deaths (SCD), 1.2% heart failure death, 0.6% resuscitated cardiac arrests, 1.1% transplants, 2.6% implantable cardioverter defibrillator (ICD) therapies and 1.2 strokes (mean follow-up: 3.81 ± 2.77 years). VO2max, ATVO2, METs, % of age-gender predicted VO2max, % of age-gender predicted METs, ABPRE and ventricular arrhythmias were significantly associated with major outcomes individually. Mean VO2max was reduced in patients who reached the combined cardiovascular death outcome compared to those who survived (-6.20 mL·kg^-1·min^-1; CI 95%: -7.95, -4.46; p < 0.01).

CONCLUSIONS

CPET is a valuable tool and can safely perform for assessment of physical functional capacity in patients with HCM. VO2max is the most common performance measurement evaluated in functional studies, showing higher values in those based on cycle-ergometer compared to treadmill. Subgroup analysis shows that exercise intolerance seems to be more related to age, medication and comorbidities than HCM phenotype itself. Lower VO2max is consistently seen in HCM patients at major cardiovascular risk.

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.

Insights from Cardiopulmonary Exercise Testing in Pediatric Patients with Hypertrophic Cardiomyopathy

The usefulness of cardiopulmonary exercise test (CPET) in adult hypertrophic cardiomyopathy (HCM) patients is well-known, whereas its role in pediatric HCM patients has not yet been explored. The present study investigates possible insights from a CPET assessment in a cohort of pediatric HCM outpatients in terms of functional and prognostic assessment. Sixty consecutive pediatric HCM outpatients aged <18 years old were enrolled, each of them undergoing a full clinical assessment including a CPET; a group of 60 healthy subjects served as controls. A unique composite end-point of heart failure (HF) related and sudden cardiac death (SCD) or SCD-equivalent events was also explored. During a median follow-up of 53 months (25th–75th: 13–84 months), a total of 13 HF- and 7 SCD-related first events were collected. Compared to controls, HCM patients showed an impaired functional capacity with most of them showing peak oxygen uptake (pVO₂) values of <80% of the predicted, clearly discrepant with functional New York Heart Association class assessment. The composite end-point occurred more frequently in patients with the worst CPETs’ profiles. At the univariate analysis, pVO₂% was the variable with the strongest association with adverse events at follow-up (C-index = 0.72, p = 0.025) and a cut-off value equal to 60% was the most accurate in identifying those patients at the highest risk. In a pediatric HCM subset, the CPET assessment allows a true functional capacity estimation and it might be helpful in identifying early those patients at high risk of events.

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

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

Effect of pre-discharge cardiopulmonary fitness on outcomes in patients with ST-elevation myocardial infarction after percutaneous coronary intervention

BACKGROUND

The purpose of this study was to analyze cardiopulmonary fitness in Phase I cardiac rehabilitation on the prognosis of patients with ST-Elevation Myocardial Infarction (STEMI) after percutaneous coronary intervention (PCI).

METHODS

The study enrolled a total of 499 STEMI patients treated with PCI between January 2015 and December 2015. Patients were assigned to individualized exercise prescriptions (IEP) group and non-individualized exercise prescriptions (NIEP) group according to whether they accept or refuse individualized exercise prescriptions. We compared the incidence of major cardiovascular events between the two groups. IEP group were further divided into two subgroups based on prognosis status, namely good prognosis (GP) group and poor prognosis (PP) group. Key cardio-pulmonary exercise testing (CPX) variables that may affect the prognosis of patients were identified through comparison of the cardio-respiratory fitness (CRF).

RESULTS

There is no significant difference in the incidence of cardio-genetic death, re-hospitalization, heart failure, stroke, or atrial fibrillation between the IEP and the NIEP group. But the incidence of total major adverse cardiac events (MACE) was significantly lower in the IEP group than in the NIEP group (P = 0.039). The oxygen consumption (VO₂) at ventilation threshold (VT), minute CO₂ ventilation (E-VCO₂), margin of minute ventilation carbon dioxide production (△CO₂)_, rest partial pressure of end-tidal carbon dioxide(R-P_ETCO₂), exercise partial pressure of end-tidal carbon dioxide(E-P_ETCO₂) and margin of partial pressure of end-tidal carbon dioxide(△P_ETCO₂) were significantly higher in the GP subgroup than in the PP subgroup; and the slope for minute ventilation/carbon dioxide production (V_E/VCO₂) was significantly lower in GP subgroup than in PP subgroup (P = 0.010). The VO₂ at VT, V_E/VCO₂ slope, E-VCO₂, △CO₂, R-P_ETCO₂, E-P_ETCO₂ and margin of partial pressure of end-tidal carbon dioxide CO₂ (△P_ETCO₂) were predictive of adverse events. The VO₂ at VT was an independent risk factor for cardiovascular disease prognosis.

CONCLUSIONS

Individualized exercise prescription of Phase I cardiac rehabilitation reduced the incidence of cardiovascular events in patients with STEMI after PCI. VO₂ at VT is an independent risk factor for cardiovascular disease prognosis, and could be used as an important evaluating indicator for Phase I cardiac rehabilitation.

Diastolic dysfunction is associated with exercise impairment in patients with sickle cell anemia

BACKGROUND

Left ventricular diastolic dysfunction (DD) is an independent risk factor for mortality in sickle cell anemia (SCA) and is associated with increased extracellular volume (ECV) on cardiac MRI (CMR). Exercise impairment is common in SCA, but its causes and prognostic value are not well understood.

OBJECTIVE

To study the effects of DD and ECV on cardiopulmonary exercise test (CPET) in patients with SCA.

METHODS AND RESULTS

As part of a prospective study to characterize the cardiomyopathy of SCA (NCT02410811), 20 children and adults with SCA underwent CMR, echocardiography, and cycle ergometer CPET (age range 8-43 years). Maximum exercise was reached in 18 patients and 17 (94%) had reduced exercise capacity (%predicted VO₂ less than 80%). Six patients had DD and none had systolic dysfunction. Patients with DD had lower exercise capacity compared to patients with normal diastolic function (%predicted VO₂ 48.2 ± 9.1% vs. 61.2 ± 11.7%; P = 0.01). The z-score of left ventricular lateral E/e' ratio, which is a marker of DD, was negatively associated with %predicted VO₂ (r = -0.61, P = 0.01). All patients with moderate-to-severe exercise impairment (%predicted VO₂  < 60%) had lateral E/e' z-score > 2. In a multivariate analysis, lateral E/e' z-score was independently associated with %predicted VO₂ (P = 0.02). All participants had elevated ECV but the degree of elevation was not associated with exercise parameters.

CONCLUSION

Left ventricular DD is associated with decreased exercise capacity in SCA. Interventions to prevent or delay DD could improve exercise capacity, quality of life, and long-term outcomes in SCA.

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.

Cardiopulmonary Exercise Testing as a Tool for Diagnosing Pulmonary Hypertension in Patients with Dilated Cardiomyopathy

Background

Recently, it has become increasingly recognized that pulmonary hypertension (PH) is a particularly threatening result of left‐sided heart disease. However, there have been few investigations of the impact of cardiopulmonary exercise testing (CPX) variables on PH in dilated cardiomyopathy (DCM). We evaluated the usefulness of crucial CPX variables for detecting elevated pulmonary arterial pressure (PAP) in patients with DCM.

Methods

Ninety subjects with DCM underwent cardiac catheterization and CPX at our hospital. Receiver operator characteristic (ROC) analysis was performed to assess the ability of CPX variables to distinguish between the presence and absence of PH.

Results

Overall mean values were: mean PAP (mPAP), 18.0 ± 9.6 mmHg; plasma brain natriuretic peptide, 233 ± 295 pg/mL; and left ventricular ejection fraction, 30.2 ± 11.0%. Patients were allocated to one of two groups on the basis of mean PAP, namely DCM without PH [mean PAP (mPAP) <25 mmHg; n = 75] and DCM with PH (mPAP ≥25 mmHg; n = 15). A cutoff achieved percentage of predicted peak VO₂ (%PPeak VO₂) of 52.5% was the best predictor of an mPAP ≥25 mmHg in the ROC analysis (area under curve: 0.911). In the multivariate analysis, %PPeak VO₂ was the only significant independent predictor of PH (Wald 6.52, odds ratio 0.892, 95% CI 0.818–0.974; P = 0.011).

Conclusions

%PPeak VO₂ was strongly associated with the presence of PH in patients with DCM. Taken together, these findings indicate that CPX variables could be important for diagnosing PH in patients with DCM.

Cardiopulmonary Exercise Testing and Prognosis in Hypertrophic Cardiomyopathy

Background—

Exercise testing is performed in patients with hypertrophic cardiomyopathy to evaluate blood pressure response, a risk factor for sudden cardiac death. The prognostic role of exercise gas exchange variables is unknown.

Methods and Results—

Between 1998 and 2010, 1898 patients (age 47±15 years, range 16–86 years; 67% male) with hypertrophic cardiomyopathy underwent cardiopulmonary exercise testing. A total of 178 (9.4%) patients reached the primary end point of all-cause mortality or heart transplant (death/transplant) during a median follow-up of 5.6 years (interquartile range 2.6–8.9), giving an annual event rate of 1.6% per person year. Peak oxygen consumption (adjusted hazard ratio [HR] 0.82, 95% confidence interval [CI] 0.77–0.88, P <0.001), ventilatory efficiency (adjusted HR 1.10, 95% CI 1.00–1.22, P =0.049), and ventilatory anaerobic threshold (adjusted HR 0.82, 95% CI 0.70–0.96, P =0.016) were predictors of the primary outcome after correction for age, sex, left atrial size, nonsustained ventricular tachycardia, and ejection fraction. The overall adjusted death/transplant estimates for patients in the lowest quartile with peak oxygen consumption ≤15.3 mL/kg/min were 14% at 5 years and 31% at 10 years. Peak oxygen consumption (HR 0.81, 95% CI 0.77–0.86, P <0.01) and ventilation to carbon dioxide production (HR 1.10, 95% CI 1.08–1.13, P <0.001) were predictors of death because of heart failure or transplantation but not sudden cardiac death or implantable cardioverter defibrillator shocks.

Conclusions—

Cardiopulmonary exercise testing provides prognostic information in patients with hypertrophic cardiomyopathy. Submaximal exercise parameters, such as ventilatory efficiency and anaerobic threshold, measured alone or in combination with peak oxygen consumption, predict death from heart failure.

Pulmonary congestion at rest and abnormal ventilation during exercise in chronic systolic heart failure

BACKGROUND

In patients with chronic heart failure, abnormal ventilation at cardiopulmonary testing (expressed by minute ventilation-to-carbon dioxide production, or VE/VCO2 slope, and resting end-tidal CO2 pressure) may derive either from abnormal autonomic or chemoreflex regulation or from lung dysfunction induced by pulmonary congestion. The latter hypothesis is supported by measurement of pulmonary capillary wedge pressure, which cannot be obtained routinely but may be estimated noninvasively by measuring transthoracic conductance (thoracic fluid content 1/kΩ) with impedance cardiography.

METHODS AND RESULTS

Preliminarily, in 9 patients undergoing invasive hemodynamics during cardiopulmonary testing, we demonstrated a significant relationship between VE/VCO2 slope and resting end-tidal CO2 pressure with baseline and peak pulmonary capillary wedge pressure. Later, noninvasive hemodynamic evaluation by impedance cardiography was performed before cardiopulmonary testing in 190 patients with chronic systolic heart failure and normal lung function (aged 67±3 years, 71% with ischemia, ejection fraction 32±7%, 69% with implantable cardioverter-defibrillator or cardiac resynchronization therapy). In this group, we determined the relationship between abnormal ventilation (VE/VCO2 slope and resting end-tidal CO2 pressure) and transthoracic conductance. In the whole population, thoracic fluid content values were significantly related to VE/VCO2 slope (R=0.63, P<0.0001) and to resting end-tidal CO2 pressure (R=-0.44, P<0.001).

CONCLUSIONS

In patients with chronic heart failure, abnormal ventilation during exercise may be related in part to pulmonary congestion, as detected by resting baseline impedance cardiography.

Causes of exercise intolerance in heart failure with preserved ejection fraction: searching for consensus

Exercise intolerance is one of the cardinal symptoms of heart failure with preserved ejection fraction (HFpEF). We review its mechanistic basis using evidence from exercise studies. One barrier to a consensus understanding of the pathophysiology is heterogeneity of the patient population. Therefore, we pay special attention to varying study definitions of the disease and their possible impact on the causal factors that are implicated. We then discuss the role of exercise testing and its potential to subtype HFpEF in to more homogeneous mechanism-based subclasses.

Determinants of peak oxygen uptake in patients with hypertrophic cardiomyopathy: a single-center study

Most patients with hypertrophic cardiomyopathy (HCM) usually complain of a reduced exercise capacity, and several factors have been advocated as possible causes of this clinical feature. The present single-center study was designed to investigate exercise capacity and its main clinical determinants in HCM patients. One hundred ninety seven patients of 223 evaluated underwent a complete clinical assessment, including Doppler echocardiography, cardiopulmonary exercise test (CPET) and, in most cases, cardiac magnetic resonance. The HCM population (male 75 %; age 47 ± 16 years; NYHA class I or II 95 %; left ventricular ejection fraction 61 ± 3 %; resting left ventricular outflow tract gradient ≥30 mmHg 22 %; late gadolinium enhancement presence 58 %) showed slightly reduced mean peak oxygen uptake values (pVO2 75 ± 15 %, 23.2 ± 6.7 ml/kg/min) with a significant reduction of the achieved percentage of peak heart rate reserve (%pHRR 65 ± 20 %). Adopting a pVO2 <80 % cut-off value, 59 % of HCM patients showed a reduced exercise capacity. Age, male gender, left atrial size, chronotropic and systolic blood pressure response, ventilatory efficiency, late gadolinium enhancement presence and β-blocker therapy were independently associated with pVO2 (R (2)-adjusted index 0.738). A %pHRR cut-off value of 74 % appeared to most accurately predict an impaired exercise capacity (area under curve 0.90). A great prevalence of reduced exercise capacity is present in NYHA class I-II HCM patients. Notwithstanding its multifactorial genesis, few parameters might be adopted in identifying this feature. In this context, %pHRR value might represent a reliable and easy-to-obtain tool for the clinical evaluation of HCM patients.

Exercise intolerance in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is associated with symptoms of dyspnea and fatigue, which contribute to exercise limitation. The origins and significance of dyspnea and fatigue in PAH are not completely understood. This has created uncertainly among healthcare professionals regarding acceptable levels of these symptoms, on exertion, for patients with PAH. Dysfunction of the right ventricle (RV) contributes to functional limitation and mortality in PAH; however, the role of the RV in eliciting dyspnea and fatigue has not been thoroughly examined. This paper explores the contribution of the RV and systemic and peripheral abnormalities to exercise limitation and symptoms in PAH. Further, it explores the relationship between exercise abnormalities and symptoms, the utility of the cardiopulmonary exercise test in identifying RV dysfunction, and offers suggestions for further research.

Prognostic utility of metabolic exercise testing in minimally symptomatic patients with obstructive hypertrophic cardiomyopathy

Patients with obstructive hypertrophic cardiomyopathy (HC) are at increased risk of death or severe symptoms. Although metabolic exercise testing is routinely used in the evaluation of a variety of cardiac diseases, data on the prognostic information that can be derived from such testing in HC is lacking. We examined 182 patients (mean age 53 ± 15 years; 65% men) with obstructive HC and minimal or no cardiovascular symptoms. Each patient underwent maximum exercise testing with simultaneous metabolic gas exchange measurement. Follow-up (mean 4.0 ± 3.0 years; 100% complete) was performed to determine the vital status and occurrence of severe symptoms, defined as class III or IV symptoms of dyspnea or angina. Multiple parameters of metabolic exercise were associated with a risk of death and the development of severe symptoms. On multivariate analyses, the independent predictors of death and severe symptoms were the severity of the left ventricular outflow tract gradient at rest and the percentage of predicted peak myocardial oxygen consumption achieved during exercise. For patients with a percentage of predicted peak myocardial oxygen consumption of <60%, the 4-year survival rate free of death and severe symptoms was only 59%. In conclusion, among patients with obstructive HC and mild or no symptoms, a low metabolic exercise capacity is associated with an increased risk of death and the subsequent development of severe symptoms.

Cardiopulmonary exercise testing in the assessment of pulmonary hypertension

The assessment of patients with suspected or confirmed pulmonary arterial hypertension (PAH) and secondary pulmonary hypertension (PH) continues to evolve and, in recent years, evidence demonstrating that cardiopulmonary exercise testing (CPX) provides valuable information has grown at an impressive rate. The key premise supporting the use of CPX is that certain variables obtained provide insight into the degree of ventilation/perfusion mismatching secondary to altered pulmonary hemodynamics. In this article, we discuss the pathophysiology of PAH and secondary PH and its impact on cardiac function, review the clinical presentation of patients with elevated pulmonary pressures and outline a case for the use of CPX as an integral assessment technique, discuss CPX technology and testing procedures, and review the current state of available evidence and provide clinical recommendations for CPX in the setting of known or suspected PAH and secondary PH.