Chronic heart failure in the elderly: value of cardiopulmonary exercise testing in risk stratification

Cardiopulmonary Exercise Testing in a Prospective Multicenter Cohort of Older Adults: The Study of Muscle, Mobility and Aging (SOMMA)

BACKGROUND

Cardiorespiratory fitness (CRF) measured by peak oxygen consumption (VO2peak) declines with aging and correlates with mortality and morbidity. Cardiopulmonary Exercise Testing (CPET) has long been the criterion method to assess CRF, but its feasibility, efficacy and reliability in older adults is unclear. The large, multicenter Study of Muscle, Mobility and Aging (SOMMA) employed CPET to evaluate the mechanisms underlying declines in mobility with aging among community-dwelling older adults. Our primary objective was to design and implement a CPET protocol in older adults that was dependable, safe, scientifically valuable, and methodologically reliable.

METHODS

CPET was performed using treadmill exercise in 875 adults ≥70 years. A composite protocol included a symptom-limited peak exercise phase and two submaximal phases to assess cardiopulmonary ventilatory indices during 1) participants' preferred walking speed and 2) at slow walking speed of 1.5 mph (0.67 m/s). An adjudication process was in place to review tests for validity if they met any prespecified criteria (VO2peak <12.0 ml/kg/min; maximum heart rate (HR) <100 bpm; respiratory exchange ratio (RER) <1.05 and a rating of perceived exertion <15). A repeat test was performed in a subset (N=30) to assess reproducibility.

RESULTS

CPET was safe and well tolerated, with 95.8% of participants able to complete the VO2peak phase of the protocol. Only 56 (6.4%) participants had a risk alert during any phase of testing and only two adverse events occurred during the peak phase: a fall and atrial fibrillation. The average ± standard deviation for VO2peak was 20.2 ± 4.8 mL/kg/min, peak HR 142 ± 18 bpm, and peak RER 1.14 ± 0.09. VO2peak and RER were slightly higher in men than women. Adjudication was indicated in 47 participants; 20 were evaluated as valid, 27 as invalid (18 had a data collection error, 9 did not reach VO2peak). Reproducibility of VO2peak was high (intraclass correlation coefficient=0.97).

CONCLUSIONS

CPET was feasible, effective and safe for community-dwelling older adults, many of whom had multimorbidity and frailty. These data support a broader implementation of CPET to provide important insight into the role of CRF and its underlying determinants in aging and age-related conditions and diseases.

Clinical Perspective

What Is New?: Performing cardiopulmonary exercise testing in a community dwelling older adult with multimorbidities or frailty is feasible and exceptionally safe under highly trained exercise physiologists and physician supervision.Reproducibility of VO2peak among community-dwelling older adults with significant clinical complexity was high (intraclass correlation coefficient=0.97).The VO2peak observed was comparable to established normative data for older adults, and adds merit to the limited data collected on VO2peak norms in older adults.What Are the Clinical Implications?: Ventilatory gas collection during clinical cardiac stress testing may be valuable to plan of care in routine management of older adults due to the important role of aerobic fitness on morbidity and mortality.Cardiopulmonary exercise testing can provide insight into the role of cardiorespiratory fitness and its underlying determinants in aging and age-related conditions and diseases.

Examination of the Relationship and Dissociation Between Minimum Minute Ventilation/Carbon Dioxide Production and Minute Ventilation vs. Carbon Dioxide Production Slope

BACKGROUND

Minute ventilation/carbon dioxide production (V̇E/V̇CO₂) is a variable of cardiopulmonary exercise testing (CPET), which is evaluated by arterial CO₂pressure and ventilation-perfusion mismatch via invasive methods. This study evaluated substitute non-invasively obtained variables for minimum V̇E/V̇CO₂(Min) and V̇E vs. V̇CO₂slope (Slope) and the relationship between Min and Slope.Methods and Results:This study enrolled 1,052 patients with heart disease who underwent CPET and impedance cardiography simultaneously. At first, the correlations between the end-tidal CO₂pressure (PETCO₂), tidal volume/respiratory rate (TV/RR) ratio, V̇E and V̇CO₂Y-intercept (Y-int), and cardiac index (CI) and the Min and Slope were investigated. Second, the correlation between Min and Slope was investigated. PETCO₂showed the largest correlation value among the 4 variables. These 4 variables could reveal 84.2% and 81.9% of Min and Slope, respectively. Although Slope correlated with Min (R=0.868) and predicted 78.9% of Min, considering these 4 variables, Slope+Y-int was more strongly correlated with Min (R=0.940); the Slope+Y-int revealed 90.6% of the Min relationship in the multiple regression analysis.

CONCLUSIONS

Over 80% of the Min and Slope values were revealed with the above-mentioned 4 variables collected non-invasively. The formula, Min∝Slope+Y-int, can reveal >90% of the Min/Slope relationships, and the Y-int may be a crucial factor to clarify the relationship between Min and Slope.

Prognostic Value of Peak Oxygen Uptake in Patients Supported With Left Ventricular Assist Devices (PRO-VAD)

OBJECTIVES

The purpose of this study was to examine whether peak oxygen uptake (pVO₂) and other cardiopulmonary exercise test (CPET)-derived variables could predict intermediate-term mortality in stable continuous flow LVAD recipients.

BACKGROUND

pVO₂ is a cornerstone in the selection of patients for heart transplantation, but the prognostic power of pVO₂ obtained in patients treated with a left ventricular assist device (LVAD) is unknown.

METHODS

We collected data for pVO₂ and outcomes in adult LVAD recipients in a retrospective, multicenter study and evaluated cutoff values for pVO₂ including: 1) values above or below medians; 2) grouping patients in tertiles; and 3) pVO₂ ≤14 ml/kg/min if the patient was not treated with beta-blockers (BB) or pVO₂ ≤12 ml/kg/min if the patient was taking BB therapy.

RESULTS

Nine centers contributed data from 450 patients. Patients were 53 ± 13 years of age; 78% were male; body mass index was 25 ± 5 kg/m² with few comorbidities (stroke: 11%; diabetes: 18%; and peripheral artery disease: 4%). The cause of heart failure (HF) was most often nonischemic (66%). Devices included were the HeartMate II and 3 (Abbott); and Heartware ventricular assist devices Jarvik and Duraheart (Medtronic). The index CPET was performed at a median of 189 days (154 days-225 days) after LVAD implantation, and mean pVO₂ was 14.1 ± 5 ml/kg/min (47% ± 14% of predicted value). Lower pVO₂ values were strongly associated with poorer survival regardless of whether patients were analyzed for absolute pVO₂ in ml/kg/min, pVO₂ ≤12 BB/14 ml/kg/min, or as a percentage of predicted pVO₂ values (P ≤ 0.001 for all). For patients with pVO₂ >12 BB/14 and ventilation/carbon dioxide relationship (VE/VCO₂) slope <35, the 1-year survival was 100%.

CONCLUSIONS

Even after LVAD implantation, pVO₂ has prognostic value, similar to HF patients not supported by mechanical circulatory support devices. (PROgnostic Value of Exercise Capacity Measured as Peak Oxygen Uptake [pVO₂] in Recipients of Left Ventricular Assist Devices [PRO-VAD]; NCT04423562).

Correlation of the peak oxygen consumption and ventilatory aerobic threshold by cardiopulmonary exercise testing with atrial fibrillation recurrences after ablation in patients with paroxysmal atrial fibrillation

Background

The cardiopulmonary function is hypothesized to be associated with atrial fibrillation/atrial tachyarrhythmia (AF/AT) recurrence after AF ablation.

Purpose

To clarify the relationship between the cardiopulmonary function after successful ablation and AF/AT recurrence.

Methods

We examined 31 patients with paroxysmal AF who underwent AF ablation. Cardiopulmonary exercise testing (CPET) was performed at 1month after the ablation. A continuously increasing loading method on a bicycle ergometer was employed for the CPET.

Results

No adverse events, including AF/AT recurrence, occurred during the CPET. Among 31 patients, AT/AF recurrence was observed in seven (23%). The ventilatory anaerobic threshold (VAT) and peak oxygen consumption (VO2) were significantly higher in patients without AF/AT recurrence than in those with AT/AF recurrences (peak VO2 23.6 ± 5.7 vs 17.2 ± 4.1 mL/kg/min; VAT, 16.7 ± 2.8 vs 13.8 ± 2.7 mL/min/kg). The areas under the receiver operating characteristic curve for the peak VO2 and VAT were 0.786 (P < .01) and 0.789(P < .01), respectively. Both indices had a sensitivity of 70%–80% and specificity of 70%–80% for predicting AT/AF recurrence. Similar results were obtained for the percent values of the predicted peak VO2 and VAT.

Conclusions

The present pilot study found that CPET can be performed safely at approximately 1 month after AF ablation. The peak VO2 and VAT were significantly associated with AT/AF recurrence. The peak VO2 and VAT were thought to provide helpful information regarding AT/AF recurrence.

Ventilatory Efficacy After Transcatheter Aortic Valve Replacement Predicts Mortality and Heart Failure Events in Elderly Patients

BACKGROUND

We aimed to clarify the predictors of death or heart failure (HF) in elderly patients who undergo transcatheter aortic valve replacement (TAVR).Methods and Results:We prospectively enrolled 83 patients (age, 83±5 years) who underwent transthoracic echocardiography (TTE) and cardiopulmonary exercise testing (CPET) with impedance cardiography post-TAVR. We investigated the association of TTE and CPET parameters with death and the combined outcome of death and HF hospitalization. Over a follow-up of 19±9 months, peak oxygen uptake (V̇O₂) was not associated with death or the combined outcome. The minimum ratio of minute ventilation (V̇E) to carbon dioxide production (V̇CO₂) and the V̇E vs. V̇CO₂slope were higher in patients with the combined outcome. After adjusting for age, sex, Society of Thoracic Surgeons score and peak V̇O₂, ventilatory efficacy parameters remained independent predictors of the combined outcome (minimum V̇E/V̇O₂: hazard ratio, 1.108; 95% confidence interval, 1.010-1.215; P=0.031; V̇E vs. V̇CO₂slope: hazard ratio, 1.035; 95% confidence interval, 1.001-1.071; P=0.044), and had a greater area under the receiver-operating characteristic curve. The V̇E vs. V̇CO₂slope ≥34.6 was associated with higher rates of the combined outcome, as well as lower cardiac output at peak work rate during CPET.

CONCLUSIONS

In elderly patients, lower ventilatory efficacy post-TAVR is a predictor of death and HF hospitalization, reflecting lower cardiac output at peak exercise.

Effects of Exercise Training With and Without Ranolazine on Peak Oxygen Consumption, Daily Physical Activity, and Quality of Life in Patients With Chronic Stable Angina Pectoris

Ranolazine reduces angina frequency and increases exercise capacity. We hypothesized that exercise training with ranolazine would allow subjects to train at greater intensities, resulting in greater improvements in exercise capacity, physical activity, and health-related quality of life (HRQOL). In a pilot study, subjects with chronic stable angina pectoris were randomized to ranolazine (n = 13) or placebo (n = 16). After a 2-week drug titration period, subjects participated in a 12-week exercise program. Peak VO₂, physical activity (via accelerometer), and HRQOL were assessed before and after training. After exercise training, peak VO₂increased twice as much with ranolazine (2.1 ± 3.4 ml/kg/min) as with placebo (0.9 ± 1.5) (both p <0.05). After exercise training, both groups significantly improved HRQOL score (p <0.05); however, the improvement with ranolazine (19 ± 21) was almost 50% greater than with placebo (13 ± 18). There was a significant decrease in maximal heart rate after training with ranolazine but not with placebo (group difference, p = 0.04). Oxygen pulse (peak VO₂/peak HR) increased in both groups after training; but, the increase was 4 times greater with ranolazine - resulting in a significant difference between groups (p = 0.044). In conclusion, patients with angina, the addition of ranolazine to an exercise program may improve aerobic fitness, physical activity, and HRQOL beyond the results of an exercise training program alone. Exercise training with ranolazine led to significantly greater increases in oxygen pulse, which is significantly correlated with stroke volume and is an independent predictor of mortality.

Role of cardiopulmonary exercise testing in clinical stratification in heart failure. A position paper from the Committee on Exercise Physiology and Training of the Heart Failure Association of the European Society of Cardiology

Traditionally, the main indication for cardiopulmonary exercise testing (CPET) in heart failure (HF) was for the selection of candidates to heart transplantation: CPET was mainly performed in middle-aged male patients with HF and reduced left ventricular ejection fraction. Today, CPET is used in broader patients' populations, including women, elderly, patients with co-morbidities, those with preserved ejection fraction, or left ventricular assistance device recipients, i.e. individuals with different responses to incremental exercise and markedly different prognosis. Moreover, the diagnostic and prognostic utility of symptom-limited CPET parameters derived from submaximal tests is more and more considered, since many patients are unable to achieve maximal aerobic power. Repeated tests are also being used for risk stratification and evaluation of intervention, so that these data are now available. Finally, patients, physicians and healthcare decision makers are increasingly considering how treatments might impact morbidity and quality of life rather than focusing more exclusively on hard endpoints (such as mortality) as was often the case in the past. Innovative prognostic flowcharts, with CPET at their core, that help optimize risk stratification and the selection of management options in HF patients, have been developed.

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.

The long-term prognostic significance of 6-minute walk test distance in patients with chronic heart failure

Background. The 6-minute walk test (6-MWT) is used to assess patients with chronic heart failure (CHF). The prognostic significance of the 6-MWT distance during long-term followup (>5 years) is unclear. Methods. 1,667 patients (median [inter-quartile range, IQR]) (age 72 [65–77]; 75% males) with heart failure due to left ventricular systolic impairment undertook a 6-MWT as part of their baseline assessment and were followed up for 5 years. Results. At 5 years' followup, those patients who died (n = 959) were older at baseline and had a higher log NT pro-BNP than those who survived to 5 years (n = 708). 6-MWT distance was lower in those who died [163 (153) m versus 269 (160) m; P < 0.0001]. Median 6-MWT distance was 300 (150–376) m, and quartile ranges were <46 m, 46–240 m, 241–360 m, and >360 m. 6-MWT distance was a predictor of all-cause mortality (HR 0.97; 95% CI 0.96-0.97; Chi-square = 184.1; P < 0.0001). Independent predictors of all-cause mortality were decreasing 6-MWT distance, increasing age, increasing NYHA classification, increasing log NT pro-BNP, decreasing diastolic blood pressure, decreasing sodium, and increasing urea. Conclusion. The 6-MWT is an important independent predictor of all-cause mortality following long-term followup in patients with CHF.

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.

Ventilatory efficiency testing as prognostic value in patients with pulmonary hypertension

BACKGROUND

Increased ventilatory response has been shown to have a high prognostic value in patients with chronic heart failure. Our aim was therefore to determine the ventilatory efficiency in pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension by cardiopulmonary exercise testing (CPET) identifying PH-patients with increased risk for death within 24 months after evaluation.

METHODS

116 patients (age: 64 ± 1 years) with a mean pulmonary arterial pressure of 35 ± 1 mmHg underwent CPET and right heart catheterization. During a follow-up of 24 months, we compared the initial characteristics of survivors (n = 87) with nonsurvivors (n = 29).

RESULTS

Significant differences (p ≤ 0.005) between survivors and nonsurvivors existed in ventilatory equivalents for oxygen (42.1 ± 2.1 versus 56.9 ± 2.6) and for carbon dioxide (Ve/VCO2) (47.5 ± 2.2 versus 64.4 ± 2.3). Patients with peak oxygen uptake ≤ 10.4 ml/min/kg had a 1.5-fold, Ve/VCO2 ≥ 55 a 7.8-fold, alveolar-arterial oxygen difference ≥ 55 mmHg a 2.9-fold, and with Ve/VCO2 slope ≥ 60 a 5.8-fold increased risk of mortality in the next 24 months.

CONCLUSIONS

Our results demonstrate that abnormalities in exercise ventilation powerfully predict outcomes in PH. Consideration should be given to add clinical guidelines to reflect the prognostic importance of ventilatory efficiency parameters in addition to peak VO2.

Diastolic dysfunction and abnormal exercise ventilation predict adverse outcome in elderly patients with chronic systolic heart failure

BACKGROUND

Heart failure is increasing in the elderly and represents a socioeconomic burden requiring the correct management for which risk stratification is mandatory. Among younger patients, echocardiogram and cardiopulmonary exercise test are useful in prognostic stratification. Few studies have analyzed the utility of these tests in elderly patients.

METHODS

We report on 90 patients over 70 years old, on whom cardiopulmonary tests and echocardiograms were performed between 1998 and 2006 (67 M, 23 F; 75 ± 3 years; ejection fraction (EF) 30 ± 6%; NYHA 2.1 ± 0.8; 60% ischemic; therapy according to international guidelines). Echocardiographic variables were (1) left ventricular ejection fraction (EF); (2) severity of diastolic dysfunction on multiparametric examination of Doppler and TDI parameters; (3) severity of functional mitral regurgitation. Cardiopulmonary variables were (1) peak VO(2); (2) peak O(2) pulse; (3) peak respiratory quotient (RQ); (4) VE/VCO(2) slope. Endpoint considered was mortality of any cause at three-years follow-up.

RESULTS

Mortality was 21%. At univariate analysis, survivors (n = 71) and deceased (n = 19) were similar for age, NYHA class, peakVO(2) and RQ; they differed for EF, severity of mitral regurgitation, severity of diastolic dysfunction, O(2) pulse and VE/VCO(2) slope. At multivariate analysis, only VE/VCO(2) slope and severe diastolic dysfunction (restrictive filling pattern) discriminated between the two groups. In particular, the association of restrictive filling pattern and VE/VCO(2) slope ≥ 45 predicted 3-year mortality with sensitivity of 84% and specificity of 88%.

CONCLUSIONS

Echocardiographic and cardiopulmonary data can identify high-risk elderly patients with systolic heart failure, who may need aggressive clinical management.

A case for assessment of oscillatory breathing during cardiopulmonary exercise test in risk stratification of elderly patients with chronic heart failure

The prognostic value of exercise oscillatory breathing (EOB) during cardiopulmonary test (CPX) has been described in young chronic heart failure (HF) patients. We assessed the prognostic role of EOB vs other clinical and ventilatory parameters in elderly HF patients performing a maximal CPX.

METHODS AND RESULTS

We prospectively followed-up 370 HF outpatients ≥ 65 years after a symptom limited CPX. We tested the predictive value of clinical and ventilatory parameters for all-cause mortality and a composite of all-cause mortality and HF hospitalizations. Median age was 74 years, 51% had ischemic heart disease, 25% NYHA class III; ejection fraction was 41% [34-50]. Peak oxygen consumption (PVO(2)) was 11.9 [9.9-14] mL/kg/min, the slope of the regression line relating ventilation to CO(2) output, (VE/VCO(2) slope) was 33.9 [29.8-39.2]. EOB was found in 58% of patients. At follow-up, 84 patients died and overall 158, using a time-to-first event approach, met the composite end-point. Independent predictors of all-cause mortality were CPX EOB and the ratio of VE/VCO(2) slope to peak VO(2), hemoglobin, creatinine and body mass index. The area under the ROC curve (AUC) of the Cox multivariable model was 0.80 (95% CI 0.73 to 0.87). Independent predictors of the composite end-point were EOB, VE/VCO(2) slope, hemoglobin and HF admissions in the previous year (Model AUC 0.75) (95% CI 0.69 to 0.81).

CONCLUSIONS

Among elderly HF patients, EOB prevalence is higher than middle-aged cohorts. EOB and the ratio of VE/VCO(2) slope to peak VO(2) resulted the strongest ventilatory predictor of all-cause mortality, independent of ventricular function.

Cardiopulmonary exercise testing is equally prognostic in young, middle-aged and older individuals diagnosed with heart failure

BACKGROUND

Previous research has demonstrated the prognostic value of cardiopulmonary exercise testing (CPX) in elderly patients with heart failure (HF). Investigations that have comprehensively examined the value of CPX across different age groups are lacking. The purpose of the present investigation was to evaluate the prognostic value of CPX in young, middle-aged and older patients with HF.

METHODS

A total of 1605 subjects (age: 59.2 ± 13.7 years, 78% male) underwent CPX and were subsequently tracked for major cardiac events. Ventilatory efficiency (VE/VCO(2) slope) and peak oxygen consumption (VO(2)), both absolute and percent-predicted, were determined. The prognostic value of these CPX variables was assessed in ≤ 45, 46-65 and ≥ 66 year subgroups.

RESULTS

The three year event rates for major cardiac events in the ≤ 45, 46-65 and ≥ 66 year subgroups were 8.8%, 6.0% and 5.7%, respectively. The VE/VCO(2) slope (Hazard ratio ≥ 1.07, p<0.001), peak VO(2) (Hazard ratio ≤ 0.87, p<0.001) and percent-predicted peak VO(2) (Hazard ratio 0 ≤ 0.98, p<0.001) were all significant prognostic markers in each age subgroup. While the VE/VCO(2) slope carried the greatest prognostic strength, peak VO(2) and percent-predicted peak VO(2) were retained in multivariate analyses (Residual Chi-Square ≥ 5.2, p<0.05). With respect to peak VO(2), the actual value was the more robust prognostic marker in the ≤ 45 and ≥ 66 year subgroups while the percent-predicted expression provided better predictive resolution in subjects who were 46-65 years old.

CONCLUSIONS

These results indicate that, irrespective of a patient's age at presentation, CPX provides valuable prognostic information in the HF population.

Oxygen Pulse as a Predictor of Cardiopulmonary Events in Lung Resection

Traditional algorithms suggest a stepwise approach to the functional evaluation of candidates for lung resection. A cardiopulmonary exercise test is incorporated as a supplementary test for patients with borderline pulmonary predicted values, and sometimes as a first screening test for cardiac risk evaluation. To assess the predictive weight of exercise tests in noncardiac thoracic surgery, we retrospectively analyzed 99 patients (80 males) aged 67.8 ± 8.1 years who underwent lung resection after a cardiopulmonary exercise test. During basal spirometry, the mean predicted forced expiratory volume in the first second was 69.9% ± 18.6%, and predicted carbon monoxide diffusing capacity was 71.6% ± 20.5%. Peak oxygen consumption was 11.1 ± 3.2 mL·kg−1·min−1, oxygen pulse was 9 ± 2.8 mL·beat−1, and minute ventilation/CO2 output was 45.2 ± 7.7. Mean hospital stay was 10.4 days, and intensive care unit stay was 0.3 days. Postoperative complications occurred in 20 (20%) patients. On multivariate analysis, body mass index, a high level of exercise achieved during the cardiopulmonary exercise test, lower heart rate at peak exercise, and oxygen pulse correlated significantly with better postoperative outcome. Cardiopulmonary exercise tests are helpful for stratifying patients undergoing thoracic surgery. Perioperative complications seem to be strongly related to left ventricular function and physical performance.

Usefulness of peak exercise oxygen consumption and the heart failure survival score to predict survival in patients >65 years of age with heart failure

Peak exercise oxygen consumption (Vo(2)) and the Heart Failure (HF) Survival Score (HFSS) were developed in middle-aged patient cohorts referred for heart transplantation with HF. The prognostic value of Vo(2) in patients >65 years has not been well studied. Accordingly, the prognostic value of peak Vo(2) was evaluated in these patients with HF. A retrospective analysis of 396 patients with HF >65 years with cardiopulmonary exercise testing was performed. Peak Vo(2) and components of the HFSS (presence of coronary artery disease, left ventricular ejection fraction, heart rate, mean arterial blood pressure, presence of intraventricular conduction defects, and serum sodium) were collected. Follow-up averaged 1,038 +/- 983 days. Outcome events were defined as death, implantation of a left ventricular assist device, or urgent transplantation. Patients were divided into risk strata for peak Vo(2) and HFSS based on previous cut-off points. Survival curves were derived using Kaplan-Meier analysis and compared using log-rank analysis. Survival differed markedly by Vo(2) stratum (p <0.0001), with significantly better survival rates for the low- (>14 ml/kg/min) versus medium- (10 to 14 ml/kg/min), low- versus high- (<10 ml/kg/min), and medium- versus high-risk strata (all p <0.05). Survival also differed markedly by HFSS stratum (p <0.0001), with significantly better survival rates for the low- (> or =8.10) versus medium- (7.20 to 8.09), low- versus high- (< or =7.19), and medium- versus high-risk strata (all p <0.0001). In conclusion, peak Vo(2) and the HFSS were both excellent parameters to predict survival in patients >65 years with HF.

Additive prognostic value of cardiopulmonary exercise testing in elderly patients with heart failure

To date, the role of CPET (cardiopulmonary exercise testing) for risk stratification in elderly patients with HF (heart failure) with depressed or preserved ventricular function has not been evaluated. In the present study, we analysed whether CPET is useful in predicting outcome in this population. A total of 220 NYHA (New York Heart Association) class I–III patients with HF ≥70 years of age [median age, 75 years; 23% had NYHA class III; and 59% had preserved ventricular systolic function (left ventricular ejection fraction ≥40%)] performed maximal CPET (peak expiratory exchange ratio >1.00). Median peak oxygen uptake was 11.9 ml·kg−1 of body weight·min−1, median V̇E/V̇CO2 slope (slope of the minute ventilation/carbon dioxide production ratio) was 33.2 and 45% had an EVR (enhanced ventilatory response) to exercise (V̇E/V̇CO2 slope ≥34). During 19 months of follow-up, 94 patients (43%) met the combined end point of death and hospital admission for worsening HF, arrhythmias or acute coronary syndromes. By Cox multivariable analysis, a creatinine clearance of <50 ml/min {HR (hazard ratio), 1.657 [95% CI (confidence interval), 1.055–2.602]} and EVR [HR, 1.965 (95% CI, 1.195–3.231)] were the best predictors of outcome, while ventricular function had no influence on prognosis. In conclusion, in elderly patients with HF, a steeper V̇E/V̇CO2 slope provides additional information for risk stratification across the spectrum of ventricular function and identifies a high-risk population, commonly not considered in exercise testing guidelines.

Prognostic value of brain natriuretic peptide and enhanced ventilatory response to exercise in patients with chronic heart failure

Whether brain natriuretic peptide (BNP), combined with a cardiopulmonary exercise test (CPx) parameters or echocardiography improves prognostic stratification in mild-to-moderate systolic heart failure (HF) is currently unclear. In 156 consecutive stable outpatients with mild to moderate HF and left ventricular ejection fraction (LVEF) <40%, we assessed the impact of BNP assay, Doppler echocardiography and CPx on survival. Median BNP plasma levels were 207 [90-520] pg/mL. Mean LVEF was 33 +/- 7%. Left bundle branch block (LBBB) was present in 52 patients (33%) and a restrictive filling pattern in 35 (22%). The slope of the relation between minute ventilation and carbon dioxide production (VE/VCO(2) slope) averaged 35 +/- 8; an enhanced ventilatory response (EVR) to exercise (VE/VCO(2) slope >35) was found in 67 patients (43%). During 759 +/- 346 days of follow-up, 24 patients died. By multivariate analysis, the strongest independent predictors of all-cause death among clinical, echocardiographic variables and BNP were LBBB and beta-blocker treatment. When CPx variables were added, the best predictors of mortality were LBBB, beta-blockade and VE/VCO(2) slope. This study highlights the value of a sequential approach, based on clinical, laboratory and functional data to identify high-risk HF patients. BNP assay might constitute a simple alternative tool for patients with an inability or with clinical contraindications to exercise, advanced physical deconditioning and unreliable CPx results. However, whenever feasible, CPx with assessment of EVR is recommended for a more accurate prediction of prognosis.

Influence of DDD rate response pacing with integrated double sensors on physical efficiency and quality of life

AIMS

The aim of this study was to evaluate whether the use of a double sensor gives additional benefits for patients in improving physical efficiency as well as quality of life (QoL) as compared to the accelerometer sensor alone.

METHODS AND RESULTS

The presented research is a prospective, randomized, single-blind clinical trial. Double-sensor (accelerometer and minute-ventilation) pacemakers (Guidant, Pulsar Max DR) were implanted in 20 patients with sinus node dysfunction (SND) and chronotropic incompetence. After randomization, patients were placed in one of two groups: 1, only the accelerometer sensor was activated; 2, both sensors were activated. After a 3-month follow-up, an initial cardio-pulmonary exercise test was performed, after which the patients were placed in the opposite group for a further 3 months. Finally, the second tests were performed. In 75% of the patients an improvement in QoL was observed in the double-sensor group (P = 0.0242) when compared with the single-sensor group. The addition of a ventilating sensor had no influence on the duration of exercise test (A: 11 +/- 3.19 vs. B: 11 +/- 2.92 P = 1.0000). The parameters of cardio-pulmonary exercise tests recorded in situations A and B before exertion, and 6 minutes after exertion were not statistically different.

CONCLUSION

The use of double-sensor pacemakers does not improve physical efficiency; however, it does improve QoL.

The initial slope of the VCO2/VO2-curve (s1) in cardiopulmonary exercise testing is a strong and independent predictor of outcome in patients with previous myocardial infarction

BACKGROUND

Detecting heart failure (HF) patients at risk is a relevant clinical problem. Our goal was to define associations of clinical HF-markers and exercise parameters with respect to their prognostic power in HF-patients.

METHODS

We performed cardiopulmonary exercise testing (CPET) in 103 ischemic HF-patients. CPET-parameters included peak VO(2), VO(2) at AT, peak oxygen pulse, minimal CO(2) and O(2) equivalents, VE/VCO(2) and s1, a motivation-independent and submaximal parameter representing the initial slope of the VCO(2)/VO(2)-curve that has not been described in HF-patients so far.

RESULTS

Median follow-up was 668 days. The combined endpoint of cardiovascular death and rehospitalization due to HF occurred in 14 patients. Patients with/without events differed significantly regarding their age, NYHA-class, LVEF and NT-proBNP serum-levels. Patients with events had significantly lower peak VO(2)- and higher s1-values. NT-proBNP serum-levels, NYHA-class and LVEF were significantly correlated with peak VO(2). Only age, peak VO(2) and s1 were independent predictors of adverse events. Using multivariate analysis, s1 was a strong and independent parameter with good sensitivity and specificity.

CONCLUSION

s1 is an independent and powerful predictor in HF-patients. Since s1 is independent of maximal exercise capacity, s1 might be more accurate for the evaluation of HF-patients not willing or unable to perform maximal exercise.

Muscle sympathetic nerve activity and ventilation during exercise in subjects with and without chronic heart failure

BACKGROUND

Changes within skeletal muscle, including augmentation of its capacity to elicit reflex increases in both efferent muscle sympathetic nerve activity (MSNA) and ventilation during work, contribute significantly to exercise intolerance in heart failure (HF). Previously, we demonstrated that peak oxygen uptake (pVO(2)) in HF relates inversely to MSNA at rest and during exercise.

OBJECTIVE

To test the hypothesis that there is an independent positive relationship between resting MSNA and the ratio of ventilation to carbon dioxide output during exercise (VE/VCO(2)) that is augmented in HF.

METHODS

MSNA at rest and VE/VCO(2)) during stationary cycling were measured in 30 patients (27 men) with HF (mean +/- SD ejection fraction 20+/-6%) and in 31 age-matched controls (29 men).

RESULTS

MSNA was higher in HF patients than in controls (51.5+/-14.3 bursts/min versus 33.0+/-11.1 bursts/min; P<0.0001). The VE/VCO(2) slope was also higher in HF patients than in controls (33.7+/-5.7 versus 26.0+/-3.5; P<0.0001), whereas pVO(2) was lower in HF patients than in controls (18.6+/-6.6 versus 31.4+/-8.4 mL/kg/min; P<0.0001). There were significant relationships between MSNA and VE/VCO(2) in both HF (r=0.50; P=0.005) and control subjects (r=0.36; P=0.046). The slope of this regression equation was steeper in HF (0.20 versus 0.11 x MSNA; P=0.001). An analysis of covariance for main effects, including age and pVO(2), identified a significant independent relationship between MSNA burst frequency and VE/VCO(2) (P=0.013) that differed between HF and controls (P<0.01).

CONCLUSIONS

The magnitude of resting sympathetic activity correlates positively with the VE/VCO(2) slope. Augmentation of this relationship in HF patients is consistent with the concept that enhanced mechanoreceptor reflex activity exaggerates their ventilatory response to exercise.

The cardiopulmonary exercise test is safe and reliable in elderly patients with chronic heart failure

AIM

To assess safety and feasibility of cardiopulmonary exercise test (CPX) in elderly patients with chronic heart failure (CHF) and left ventricular dysfunction.

METHODS AND RESULTS

We analysed 395 cardiopulmonary exercise tests (CPXs) performed in 227 clinically stable patients with CHF [mean age 76 years, males 70%, mean New York Heart Association (NYHA) class 2.2 +/- 0.5] and impaired left ventricular function (mean ejection fraction 43 +/- 12%). Ninety-eight out of 395 CPXs (25%) were performed in patients older than 80 years. A standard bicycle exercise ramp protocol was used, with increments of 10 W/min. An expiratory exchange ratio (RER) >or= 1.05 at the peak of CPX was considered as the index of maximal exercise. Average workload was 65 +/- 23 W. No adverse reactions were observed, although one test was stopped for non-sustained ventricular tachycardia. The main reasons for stopping were exhaustion (50%), dyspnoea (30%), maximal predicted heart rate (17%), orthopaedic problems (2.5%) and significant ST segment depression (0.5%). In the overall cohort, 80% of patients achieved an RER >or= 1.05 and, in 56% of them, the RER was >or= 1.15. The anaerobic threshold (AT) was detectable in 80% of CPXs, and mean oxygen consumption (VO2) at AT was 9 +/- 6 ml/kg per min, whereas mean peak VO2 was 11 +/- 3 ml/kg per min. In the cohort of patients aged > 80 years, 71% reached an RER >or= 1.05 and 47% reached an RER >or= 1.15. In these older patients, AT was detectable in 68% of CPXs performed, and the mean peak VO2 was 10 +/- 3 ml/kg per min.

CONCLUSIONS

In elderly patients with CHF, the CPX is safe, feasible and able to provide basic information for individual risk assessment. These findings potentially extend the indications of CPX, which is currently applied to selected middle-aged patients with CHF, to the elderly population.

Metabolic gas kinetics depend upon the level of exercise performed

BACKGROUND

The kinetics of oxygen and carbon dioxide at the onset of and recovery from exercise are slowed in patients with chronic heart failure (CHF). The aim of the present study was to establish whether the kinetics of O2 are influenced by the work rate.

METHODS

Thirteen CHF patients and 12 control subjects underwent bicycle-based peak exercise testing with metabolic gas exchange analysis. Each subject then exercised at 15%, 25% and 50% of the maximal workload achieved until reaching steady state. Time constants for onset (T(onset)) and offset (T(offset)) for O2 uptake and CO2 output were correlated to the workload and the percentage of peak V(O2) performed during the steady state tests.

RESULTS

Patients had lower peak oxygen uptake (pV(O2)) and the relation between ventilation and carbon dioxide output was steeper in patients than controls. T(offset) for both oxygen (O2) and carbon dioxide (CO(2)) from peak exercise was significantly greater in the patients than the controls and correlated with peak V(O2) (r=0.56, p<0.005 and r=0.58, p<0.005). T(onset) and T(offset) for O2 were increased in patients for each of the steady state tests and peak V(O2) correlated with T for recovery of O2 (r=0.44; p<0.05 from 15%, r=0.35; p= or <0.05 from 25%, and r=0.54; p<0.01 from 50%). There was a correlation between the T(onset) (r=0.42; p<0.0005 for O2 and r=0.23; p<0.05 for CO2) and T(offset) (r=0.49; p<0.0001 for O2 and r=0.42; p<0.0005 for CO2) and oxygen uptake as a percentage of peak exercise.

CONCLUSIONS

This study demonstrates that the time constants of onset and offset for oxygen are dependent upon the degree of exertion performed relative to the individual's peak capacity.

The Prognostic Value of Ventilatory Efficiency with Beta-Blocker Therapy in Heart Failure

PURPOSE

Beta-blockade (BB) has been shown to improve outcomes among patients with heart failure (HF). The impact this pharmacological approach has on the prognostic information gained from cardiopulmonary exercise testing (CPX) is, however, unclear.

METHODS

Four hundred seventeen subjects diagnosed with HF underwent CPX. The numbers of subjects prescribed and not prescribed a BB agent were 167 and 250, respectively. Subjects were tracked for cardiac-related mortality after CPX.

RESULTS

Values are reported for the no-BB versus the BB group throughout. Age (57.9 +/- 13.3 vs 55.6 +/- 12.5), peak VO2 (16.2 +/- 5.7 vs 16.5 +/- 5.5 mL x kg(-1) x min(-1)), VE/VCO2 slope (34.2 +/- 9.0 vs 33.2 +/- 7.4), and peak RER (1.07 +/- 0.16 vs 1.05 +/- 0.14) were similar between groups (P > 0.05). Multivariate Cox regression analysis revealed that the VE/VCO2 slope was the superior predictor of death in both groups (chi-square: 71.9, P < 0.001; and 18.4, P < 0.001). The optimal threshold values for VE/VCO2 slope in the no-BB and BB groups were 36.0 and 34.3, respectively.

CONCLUSIONS

The results of the present study indicate that BB does not alter the prognostic value/characteristics of the VE/VCO2 slope. Findings from previous investigations examining the prognostic significance of CPX predominantly using HF groups not receiving a BB agent may, therefore, still be applicable in modern-day clinical practice.

Limitations of the New York Heart Association functional classification system and self-reported walking distances in chronic heart failure

BACKGROUND

Two ways to evaluate the symptoms of heart failure are the New York Heart Association (NYHA) classification and asking patients how far they can walk (walk distance). The NYHA system is commonly used, although it is not clear how individual clinicians apply it.

AIM

To investigate how useful these measures are to assess heart failure and whether other questions might be more helpful.

METHODS

30 cardiologists were asked what questions they used when assessing patients with heart failure. To assess interoperator variability, two cardiologists assessed a series of 50 patients in classes II and III using the NYHA classification. 45 patients who had undergone cardiopulmonary testing were interviewed using a specially formulated questionnaire. They were also asked how far they could walk before being stopped by symptoms, and then tested on their ability to estimate distance.

RESULTS

The survey of cardiologists showed no consistent method for assessing NYHA class and a literature survey showed that 99% of research papers do not reference or describe their methods for assigning NYHA classes. The interoperator variability study showed only 54% concordance between the two cardiologists. 70% of cardiologists asked patients for their walk distance; however, this walk distance correlated poorly with actual exercise capacity measured by cardiopulmonary testing (rho = 0.04, p = 0.82).

CONCLUSION

No consistent method of assessing NYHA class is in use and the interoperator study on class II and class III patients gave a result little better than chance. Some potential questions are offered for use in assessment. Walking distance, although frequently asked, does not correlate with formally measured exercise capacity, even after correction for patient perception of distance, and has never been found to have prognostic relevance. Its value is therefore doubtful.

Enhanced prognostic value from cardiopulmonary exercise testing in chronic heart failure by non-linear analysis: oxygen uptake efficiency slope

AIMS

Predicting survival from peak exercise oxygen uptake (peak VO2) in chronic heart failure (CHF) is hindered by its reduction if exercise duration is submaximal. The oxygen uptake efficiency slope (OUES) is a non-linear description of the ventilatory response to exercise, which has the potential to describe abnormalities even early in exercise. We evaluated the physiology of OUES and assessed its potential for prognostic information in patients with CHF.

METHODS AND RESULTS

Two hundred and forty-three patients with CHF (mean age 59+/-12 years) underwent cardiopulmonary exercise testing between May 1992 and July 1996. Mean peak VO2 was 16.2+/-6.7 mL/kg/min, VE/VCO2 slope 38+/-12.5, ventilatory anaerobic threshold 10.9+/-3.5 mL/kg/min, and OUES 1.6+/-0.7 L/min. The value for each variable fell across the New York Heart Association classes (P<0.0001 by analysis of variance for each). When only the first 50% of each exercise test was used to calculate the variables, the value obtained for OUES changed the least (peak VO2 25% difference and OUES 1% difference). After a median of 9 years of follow-up, 139 patients (57%) had died. Each of the exercise variables was a significant univariate predictor of prognosis but in a multivariable model, only OUES was identified as the sole significant independent prognostic variable.

CONCLUSION

OUES provides an effective, independent measure of pathological exercise physiology. Its numerical value is relatively insensitive to the duration of exercise data from which it is calculated. Its prognostic value seems to be stronger than the best available existing measures of exercise physiology.

Influence of Heart Failure Etiology on the Prognostic Value of Peak Oxygen Consumption and Minute Ventilation/Carbon Dioxide Production Slope

BACKGROUND

Peak oxygen consumption (V(O2)) and minute ventilation (V(E))/carbon dioxide production (V(CO2)) slope have been widely demonstrated to have strong prognostic value in patients with heart failure (HF). In the present study, we investigated the effect of HF etiology on the prognostic applications of peak V(O2) and Ve/V(CO2) slope.

METHODS

Two hundred sixty-eight subjects underwent symptom-limited cardiopulmonary exercise testing (CPX). The population was divided into ischemic (115 men and 22 women) and nonischemic (108 men and 23 women) subgroups. The occurrence of cardiac-related events over the year following CPX was compared between groups using receiver operating characteristic curve (ROC) analysis

RESULTS

Mean age +/- SD was significantly higher (61.0 +/- 10.0 years vs 50.3 +/- 16.2 years) while mean peak V(O2) was significantly lower (15.0 +/- 5.2 mL/kg/min vs 17.5 +/- 6.7 mL/kg/min) in the ischemic HF group (p < 0.05). ROC curve analysis demonstrated that both peak V(O2) and V(E)/V(CO2) slope were significant predictors of cardiac events in both the ischemic group (peak V(O2), 0.74; V(E)/V(CO2) slope, 0.76; p < 0.001) and the nonischemic group (peak V(O2), 0.75; V(E)/V(CO2) slope, 0.86; p < 0.001). Optimal prognostic threshold values for peak V(O2) were 14.1 mL/kg/min and 14.6 mL/kg/min in the ischemic and nonischemic groups, respectively. Optimal prognostic threshold values for the V(E)/V(CO2) slope were 34.2 and 34.5 in the ischemic and nonischemic groups, respectively.

CONCLUSIONS

Baseline and exercise characteristics were different between ischemic and nonischemic patients with HF. However, the prognostic power of the major CPX variables was strikingly similar. Different prognostic classification schemes based on HF etiology may therefore not be necessary when analyzing CPX responses in clinical practice.

Impact of time past exercise testing on prognostic variables in heart failure

BACKGROUND

Cardiopulmonary exercise testing (CPET) is considered a standard of care in heart failure (HF). The impact that duration of time post-evaluation has on the prognostic value of CPET, however, has not been explored. The purpose of this investigation was to examine the ability of peak oxygen consumption (VO(2)) and the minute ventilation-carbon dioxide production (VE/VCO(2)) slope to predict cardiac-related events at different time intervals post CPET.

METHODS

Two hundred fifty-eight subjects diagnosed with HF underwent CPET. The ability of peak VO(2) and VE/VCO(2) slope to predict cardiac-related events without a time limit, one year post CPET and greater than one year post CPET was examined.

RESULTS

Both peak VO(2) and VE/VCO(2) slope were significant predictors of cardiac-related mortality and hospitalization during the no time constraint and one year post CPET tracking scenarios (Hazard Ratio Range: 3.5-12.4, p<0.001). Peak VO(2) was no longer a significant predictor of mortality greater than one year post CPET. Generally, as time following CPET surpassed one year, the prognostic sensitivity of both variables slightly increased ( approximately 5%) while specificity sharply decreased ( approximately 20%).

CONCLUSIONS

Both peak VO(2) and VE/VCO(2) slope are significant predictors of cardiac-related events in HF. However, the prognostic characteristics of these variables following CPET appear to be time-sensitive.

Influence of etiology on ventilatory expired gas and prognosis in heart failure

BACKGROUND

Mechanisms leading to heart failure (HF) are numerous. Etiology-based differences are, however, frequently not taken into account when assessing results of an exercise test. The purpose of this investigation is to: (1) compare subject characteristics and ventilatory expired gas measures demonstrating clinical value between subjects with ischemic and non-ischemic HF. (2) Examine the prognostic value of HF etiology.

METHODS

71 subjects (44 male/27 female) diagnosed with compensated HF underwent exercise testing with ventilatory expired gas analysis. Mean age and ejection fraction (EF) were 51.3% (+/-12.8) and 27.0% (+/-12.5%) for the entire group. HF etiology was ischemic in 30 subjects (16 male/14 female) and non-ischemic in 41 (28 male/13 female).

RESULTS

Age (57.5+/-10.7 vs. 46.7+/-12.5, p<0.001), minute ventilation-carbon dioxide production (VE/VCO2) slope (39.5+/-9.1 vs. 32.6+/-7.7, p=0.001), and duration of phase 1 kinetics in seconds (46.0+/-23.0 vs. 30.0+/-15.6, p=0.001) were significantly higher while peak oxygen consumption (VO2) in ml O2 kg(-1) min(-1) (12.5+/-4.7 vs. 16.0+/-5.2, p=0.006) and partial pressure of end-tidal CO2 (P(ET)CO2) in mm Hg at rest (32.1+/-4.8 vs. 36.1+/-8.0, p=0.02) and peak exercise (31.7+/-4.3 vs. 36.2+/-5.9, p=0.001) were significantly lower in the ischemic group. Difference in EF did not reach statistical significance (28.4% +/-12.5%-ischemic vs. 26.1%+/-12.5%-non-ischemic, p=0.44). Ischemic etiology was additionally a significant predictor of cardiac-related events (p=0.04).

CONCLUSIONS

These findings demonstrate noninvasive indicators of cardiac function and prognosis is poorer in subjects with ischemic HF etiology. Consideration of HF etiology may therefore be prudent, particularly when considering prognosis.

The effect of aspirin on the ventilatory response to exercise in chronic heart failure

INTRODUCTION

Patients with chronic heart failure (CHF) experience breathlessness and fatigue on exercise. One of the abnormalities seen on maximal exercise testing is an increased ventilatory response to exercise (VE/VCO(2) slope). The cause of this is unknown, but is likely to be due to a combination of interacting peripheral and central factors. Recent data have demonstrated a relation between VE/VCO(2) slope and prostaglandin levels in contracting muscles. The present study examined the influence of the presence of a potent non-selective prostaglandin inhibitor, aspirin, on the ventilatory response to exercise in a group of patients with CHF.

METHODS

We investigated the ventilatory response to exercise of 120 consecutive patients in sinus rhythm attending a specialist heart failure clinic. We excluded those taking clopidogrel (six patients) and those on both warfarin and aspirin or taking other non-steroidal anti-inflammatory agents (five patients). The other 109 patients were grouped according to whether they were taking aspirin (n=52 (48%)) or not (n=57 (52%)). Each patient underwent echocardiography to assess left ventricular function, and exercise testing with metabolic gas exchange to derive peak oxygen consumption (pVO(2)) and the VE/VCO(2) slope.

RESULTS

The groups were similar in terms of age, (67 (13) vs. 66 (12) years; P=0.34) drug use, heart failure aetiology, left ventricular function (ejection fraction; 33.3 (9.4) vs. 31.8 (9.9)%; P=0.05)) and exercise tolerance (pVO(2); 20.4 (5.3) vs. 19.9 (6.0); P=0.68, and VE/VCO(2) slope; 35.4 (6.2) vs. 35.7 (9.3); P=0.73). There was no difference in the ventilatory response to exercise or the symptoms of breathlessness between the two groups.

CONCLUSIONS

Aspirin does not appear to affect exercise performance in CHF.

Technical considerations related to the minute ventilation/carbon dioxide output slope in patients with heart failure

BACKGROUND

The minute ventilation (VE)-carbon dioxide output (VCO(2)) relationship has recently been demonstrated to have prognostic significance in the heart failure (HF) population. However, the method by which the VE/VCO(2) slope is expressed has been inconsistent.

METHODS

One hundred eighty-eight subjects, who had received diagnoses of HF, underwent exercise testing. Two VE/VCO(2) slope calculations were made, one using exercise data prior to the ventilatory threshold (VT), and one using all data points from rest to peak exercise. Four separate peak exercise VE/VCO(2) slope calculations also were derived with unaveraged, 10-s, 30-s, and 60-s ventilatory expired gas sampling intervals.

RESULTS

Although univariate Cox regression analysis demonstrated pre-VT and peak VE/VCO(2) slope calculations to both be significant predictors of cardiac-related mortality and hospitalization (p < 0.001), the peak classification scheme was significantly better (p < 0.01). The ventilatory expired gas-sampling interval that was used did not impact the predictive ability of the peak VE/VCO(2) slope.

CONCLUSION

Although both the pre-VT and peak VE/VCO(2) slope calculations were prognostically significant, the peak expression was superior. The sampling interval did not appear to have a significant impact on prognostic utility. We hope that the results of the present study will contribute to the standardization of the VE/VCO(2) slope and will enhance its clinical application.

Pattern of ventilation during exercise in chronic heart failure

OBJECTIVE

To determine the pattern of the abnormal ventilatory response in heart failure and how it relates to symptoms by looking at tidal volume (VT) and frequency (f) during exercise.

METHODS

45 patients with heart failure and 21 controls underwent maximal treadmill based exercise testing with metabolic gas exchange analysis. The relation of ventilation (VE) to VT was plotted to look for an inflection point where VT failed to increase further. The slope of the relation before this inflection point was documented. Time to the inflection point, VT, and f at the inflection point were recorded. The relation of symptom scores to f and E was also examined.

RESULTS

Peak oxygen consumption (PVO2) (mean (SD)) was lower (19.7 (4.5) v 37.9 (8.6) ml/kg/min; p < 0001) and the ventilation to carbon dioxide production (VE/VCO2) slope was steeper (40.0 (6.5) v 26.0 (1.6); p < 0.0001) in patients with heart failure than in the control group. The patients reached the inflection point of the VE/VT slope sooner during exercise than the controls (271 (110) v 502 (196) seconds; p < 0.0001). Patients had a higher f and a smaller VT at that point and throughout exercise until the peak where f was the same for patients and controls. VT at the inflection point correlated with PVO2 (r = 0.67; p < 0.0001). Despite having an increased sensation of breathlessness for a given E, patients were less symptomatic of f than controls.

CONCLUSIONS

Patients with heart failure breathe at a higher f throughout exercise, reaching an apparent maximal VT earlier. The VT at an inflection point on the VE/VT slope predicts PVO2.

Role of cardiac power in heart failure

The heart is a muscular mechanical pump with an ability to generate both flow (cardiac output) and pressure. The product of flow output and systemic arterial pressure is the rate of useful work done, or power output. Cardiac pumping capability can be defined as the cardiac power output (CPO(max)) achieved by the heart during maximal stimulation. Cardiac reserve is the increase in power output as the cardiac performance is increased from the resting to the maximally stimulated state. Recently, several studies have shown that CPO(max), a direct indicator of overall cardiac function, measured directly or as an approximation, is a major determinant of exercise capacity and a most powerful predictor of prognosis for patients with chronic heart failure. The same holds true in acute heart failure, where it is also useful in subclassifying the conditions to select the appropriate treatment.

Ventilatory variables are strong prognostic markers in elderly patients with heart failure

OBJECTIVE

To evaluate the safety and prognostic capacity of cardiopulmonary exercise testing in patients > or = 60 years old who are hospitalised with heart failure caused by left ventricular dysfunction.

DESIGN

Prospective study.

SETTING

University hospital.

PATIENTS

Study participants were 67 patients (66% men) with clinical heart failure stabilised on medical treatment. The study is a part of a nursing intervention study. Mean (SD) age was 74 (6) years, New York Heart Association functional class II-III, and ejection fraction 0.36 (0.11).

INTERVENTIONS

Cardiopulmonary exercise testing and echocardiography.

MAIN OUTCOME MEASURES

Peak oxygen consumption (VO2), peak ventilatory equivalents for carbon dioxide (VE/VCO2) and oxygen (VE/VO2), left ventricular volumes, and mortality.

RESULTS

Mean (SD) peak VO2 was 11.7 (3.7) ml/kg/min, peak VE/VCO2 43 (9), and peak VE/VO2 46 (11). During 12-59 months of follow up, 14 patients died. In univariate analyses peak VO2, VE/VO2, and VE/VCO2 were all strongly related (p < 0.01) to mortality. In a multivariate Cox regression analysis, peak VE/VCO2 was the strongest predictor of mortality (p < 0.001), followed by left ventricular end systolic volume (p < 0.001). A cut off of peak VE/VCO2 at > or = 45 gave a univariate hazard ratio of 6.7 for death during follow up. No adverse events occurred during the exercise test.

CONCLUSION

These findings extend results found in selected middle aged patients to elderly patients with heart failure and show that ventilatory parameters from a cardiopulmonary exercise test, such as peak VO2, VE/O2, and VE/VCO2 are powerful predictors of mortality.

Is the elevated slope relating ventilation to carbon dioxide production in chronic heart failure a consequence of slow metabolic gas kinetics?

OBJECTIVE

Patients with heart failure have slow metabolic gas exchange kinetics, which may contribute to the elevated slope of the relationship between ventilation and carbon dioxide production (Ve/Vco(2) slope).

SETTING

A tertiary referral centre for cardiology.

SUBJECTS

Eleven patients with stable chronic heart failure and 11 age-matched controls.

DESIGN

Each subject underwent maximal bicycle-based peak exercise testing with metabolic gas exchange analysis and three further repeated tests at 15%, 25% and 50% of the load achieved at peak exercise. The ventilation and carbon dioxide production from each of these steady-state tests was used to re-calculate the Ve/Vco(2) slope and compared with the Ve/Vco(2) slope derived from the maximal test.

RESULTS

Peak oxygen consumption [mean (S.D.)] was lower in heart failure patients [18.2 (4.0) vs. 31.2 (6.3) ml/kg per min; P<0.001] than in controls. The Ve/Vco(2) slope was steeper in patients than controls [32.7 (8.3) vs. 27.1 (1.6); P<0.05]. There was no difference between the Ve/Vco(2) slope reconstructed from the three steady state tests and resting data and that gained from the maximal test [35.3 (7.8) vs. 25.9 (3.2); P=0.43].

CONCLUSIONS

The elevated slope of the relationship between ventilation and carbon dioxide production is not a consequence of the short stages of a standard incremental exercise test combined with delayed metabolic gas kinetics in heart failure patients.

Comparison of ventilatory expired gas parameters used to predict hospitalization in patients with heart failure

BACKGROUND

Several ventilatory expired gas measures obtained during exercise testing demonstrate prognostic value in the heart failure (HF) population. Comparison of prognostic efficacy between pertinent measures is sparse.

METHODS

The ability of various expressions of peak oxygen consumption (VO2), the relationship between minute ventilation (VE) and carbon dioxide production (VCO2), and the partial pressure of end-tidal carbon dioxide (P(ET)CO2) were assessed to determine which measure(s) best predicted cardiac-related hospitalization over a 1-year period in subjects diagnosed with HF.

RESULTS

Univariate Cox regression analysis found that several expressions of peak VO 2, VE-VCO2 relationship, and P(ET)CO2 were significant predictors of hospitalization. Multivariate Cox regression analysis revealed that the VE/VCO2 slope significantly predicted hospitalization (chi2 = 29.1, P <.00001). Peak VO 2 and P(ET)CO2 did not provide additional predictive value.

CONCLUSIONS

The prognostic superiority of the VE/VCO2 slope over peak VO2 may be a result of the latter measure's partial dependence on subject effort and skeletal muscle function.

Clinical features and outcomes of elderly outpatients with heart failure followed up in hospital cardiology units: data from a large nationwide cardiology database (IN-CHF Registry)

BACKGROUND

Congestive heart failure (HF) represents a major public health problem with an age-related increasing prevalence. Despite the high mortality and morbidity in elderly patients with HF, limited clinical and prognostic data are available for development of appropriate prevention and treatment strategies.

METHODS

A cohort of 3327 outpatients consecutively enrolled in the Registry of Italian Network on Congestive Heart Failure by 133 cardiology centers was studied. Univariate and multivariate analyses were performed to compare patients <70 and > or =70 years old and to evaluate associations between clinical variables and the 1-year mortality rate and hospitalizations.

RESULTS

With respect to the 2294 patients <70 years old, the 1033 (31%) elderly patients were significantly more likely to be female, to be in New York Heart Association (NYHA) class III-IV, and to have preserved left ventricular systolic function (ejection fraction >40%), an ischemic/valvular etiology, and atrial fibrillation/flutter. Elderly patients received angiotensin-converting enzyme inhibitors, beta-blockers, and anticoagulants less frequently than younger patients did. The 1-year mortality rate was significantly higher in patients > or =70 years old (22% vs 13.7%, P <.001). Age was an independent predictor of 1-year mortality, increasing 2.8% by each year of age. Independent predictors of 1-year mortality in elderly patients were (1) > or =1 hospital admission in the previous year (relative risk [RR] 2.09, 95% CI 1.51-2.87), (2) systolic blood pressure (RR 0.98, 95% CI 0.97-0.99), (3) NYHA class III-IV (RR 1.57, 95% CI 1.20-2.07), and (4) age (RR 1.028, 95% CI 1.001-1.056).

CONCLUSIONS

Our study confirms that elderly patients (1) are seen in a more advanced stage of HF, (2) are less likely to receive evidence-based treatments, (3) show more frequently preserved systolic function, and (4) have a worse prognosis. Consequently, there is a need to develop more effective and targeted management strategies for this escalating health problem.

Assessing patients with possible heart disease using scores

Multivariable analysis of clinical and exercise test data has the potential to become a useful tool for assisting in the diagnosis of coronary artery disease, assessing prognosis, and reducing the cost of evaluating patients with suspected coronary disease. Since general practitioners are functioning as gatekeepers and decide which patients must be referred to the cardiologist, they need to use the basic tools they have available (i.e. history, physical examination and the exercise test), in an optimal fashion. Scores derived from multivariable statistical techniques considering clinical and exercise data have demonstrated superior discriminating power compared with simple classification of the ST response. In addition, by stratifying patients as to probability of disease and prognosis, they provide a management strategy. While computers, as part of information management systems, can run complicated equations and derive these scores, physicians are reluctant to trust them. Thus, these scores have been represented as nomograms or simple additive tables so physicians are comfortable with their application. Their results have also been compared with physician judgment and found to estimate the presence of coronary disease and prognosis as well as expert cardiologists and often better than nonspecialists. However, the discriminating power of specific variables from the medical history and exercise test remains unclear because of inadequate study design and differences in study populations. Should expired gases be substituted for estimated metabolic equivalents (METs)? Should ST/heart rate (HR) index be used instead of putting these measurements separately into the models? Should right-sided chest leads and HR in recovery be considered? There is a need for further evaluation of these routinely obtained variables to improve the accuracy of prediction algorithms especially in women. The portability and reliability of these equations must be demonstrated since access to specialised care must be safe-guarded. Hopefully, sequential assessment of the clinical and exercise test data and application of the newer generation of multivariable equations can empower the clinician to assure the cardiac patient access to appropriate and cost-effective cardiological care.