Increased minute ventilation-to-carbon dioxide slope during cardiopulmonary exercise test is associated with poor postoperative outcome following lung cancer resection

OBJECTIVES

Ventilatory efficiency [minute ventilation-to-carbon dioxide output slope (VE/VCO2 slope)] can be measured at sub-maximal workload during cardiopulmonary exercise test. The aim of this study is to assess the association between VE/VCO2 slope and outcome after lung cancer resections.

METHODS

Retrospective, single-centre analysis on all patients undergoing lung resection for cancer (April 2014-August 2022) and with a preoperative cardiopulmonary exercise test. VE/VCO2 slope >40 was chosen as high-risk threshold. Logistic regression analysis was used to test the association of VE/VCO2 slope and several patient- and surgery-related factors with 90-day mortality.

RESULTS

A total of 552 patients were included (374 lobectomies, 81 segmentectomies, 55 pneumonectomies and 42 wedge resections). Seventy-four percent were minimally invasive procedures. Cardiopulmonary morbidity was 32%, in-hospital/30-day mortality 6.9% and 90-day mortality 8.9%. A total of 137 patients (25%) had a slope of >40. These patients were older (72 vs 70 years, P = 0.012), had more frequently coronary artery disease (17% vs 10%, P = 0.028), lower carbon monoxide lung diffusion capacity (57% vs 68%, P < 0.001), lower body mass index (25.4 vs 27.0 kg/m2, P = 0.001) and lower peak VO2 (14.9 vs 17.0 ml/kg/min, P < 0.001) than those with a lower slope. The cardiopulmonary morbidity among patients with a slope of >40 was 40% vs 29% in those with lower slope (P = 0.019). Ninety-day mortality was 15% vs 6.7% (P = 0.002). The 90-day mortality of elderly patients with slope >40 was 21% vs 7.8% (P = 0.001). After adjusting for peak VO2 value, extent of operation and other patient-related variables in a logistic regression analysis, VE/VCO2 slope retained a significant association with 90-day mortality.

CONCLUSIONS

VE/VCO2 slope was strongly associated with morbidity and mortality following lung resection and should be included in the functional algorithm to assess fitness for surgery.

Dysregulation of ventilation at day and night time in heart failure

Heart failure (HF) is characterized by an increase in ventilatory response to exercise of multifactorial aetiology and by a dysregulation in the ventilatory control during sleep with the occurrence of both central and obstructive apnoeas. In this setting, the study of the ventilatory behaviour during exercise, by cardiopulmonary exercise testing, or during sleep, by complete polysomnography or simplified nocturnal cardiorespiratory monitoring, is of paramount importance because of its prognostic value and of the possible effects of sleep-disordered breathing on the progression of the disease. Moreover, several therapeutic interventions can significantly influence ventilatory control in HF. Also, rest daytime monitoring of cardiac, metabolic, and respiratory activities through specific wearable devices could provide useful information for HF management. The aim of the review is to summarize the main studies conducted at Centro Cardiologico Monzino on these topics.

Age Differences in Cardiopulmonary Exercise Testing Parameters in Heart Failure with Reduced Ejection Fraction

Background and Objectives: Cardiopulmonary exercise testing (CPET) is a cornerstone of risk stratification in heart failure with reduced ejection fraction (HFrEF). However, there is a paucity of evidence on its predictive power in older patients. The aim of this study was to evaluate the prognostic power of current heart transplantation (HTx) listing criteria in HFrEF stratified according to age groups. Materials and Methods: Consecutive patients with HFrEF undergoing CPET between 2009 and 2018 were followed-up for cardiac death and urgent HTx. Results: CPET was performed in 458 patients with HFrEF. The composite endpoint occurred in 16.8% of patients ≤50 years vs. 14.1% of patients ≥50 years in a 36-month follow-up. Peak VO2 (pVO2), VE/VCO2 slope and percentage of predicted pVO2 were strong independent predictors of outcomes. The International Society for Heart and Lung Transplantation thresholds of pVO2 ≤ 12 mL/kg/min (≤14 if intolerant to β-blockers), VE/VCO2 slope > 35 and percentage of predicted pVO2 ≤ 50% presented a higher overall diagnostic effectiveness in younger patients (≤50 years). Specific thresholds for each age subgroup outperformed the traditional cut-offs. Conclusions: Personalized age-specific thresholds may contribute to an accurate risk stratification in HFrEF. Further studies are needed to address the gap in evidence between younger and older patients.

Ventilatory efficiency in post-COVID-19 athletes

Limitation in exercise capacity has not been described in athletes affected by SARS-CoV-2 infection. However, patients who have recovered from COVID-19 without cardiopulmonary impairment show exaggerated ventilatory response during exercise. Therefore, we aimed to evaluate the ventilatory efficiency (VEf) in competitive athletes recovered from COVID-19 and to characterize the ventilation versus carbon dioxide relationship (VE/VCO2 ) slope in this population. Thirty-seven competitive athletes with COVID-19 were recruited for this study. All participants underwent spirometry, echocardiography, and cardiopulmonary exercise testing (CPET). z-FVC values and end-title pressure of CO2 (PET CO2 ) were lower in the third tertile compared with the first tertile: -0.753 ± 0.473 vs. 0.037 ± 0.911, p = 0.05; 42.2 ± 2.7 vs. 37.1 ± 2.5 mmHg, p < 0.01. VE/VCO2 slope was significantly correlated to maximal VCO2 /VE and maximal VO2 /VE: coefficient = -0.5 R2  = 0.58, p < 0.0001 and coefficient = -0.3 R2  = 0.16, p = 0.008. Competitive athletes affected by SARS-CoV-2 infection, without cardio-respiratory disease sequel, may present ventilatory inefficiency (ViE), without exercise capacity limitation. FVC is higher in athletes with better ventilatory performance during exercise, and increased VE/VCO2 slope is inversely correlated to max VCO2 /VE and max VO2 /VE.

Cardiopulmonary Exercise Testing in the Age of New Heart Failure Therapies: Still a Powerful Tool?

BACKGROUND

New therapies with prognostic benefits have been recently introduced in heart failure with reduced ejection fraction (HFrEF) management. The aim of this study was to evaluate the prognostic power of current listing criteria for heart transplantation (HT) in an HFrEF cohort submitted to cardiopulmonary exercise testing (CPET) between 2009 and 2014 (group A) and between 2015 and 2018 (group B).

METHODS

Consecutive patients with HFrEF who underwent CPET were followed-up for cardiac death and urgent HT.

RESULTS

CPET was performed in 487 patients. The composite endpoint occurred in 19.4% of group A vs. 7.4% of group B in a 36-month follow-up. Peak VO2 (pVO2) and VE/VCO2 slope were the strongest independent predictors of mortality. International Society for Heart and Lung Transplantation (ISHLT) thresholds of pVO2 ≤ 12 mL/kg/min (≤14 if intolerant to β-blockers) and VE/VCO2 slope > 35 presented a similar and lower Youden index, respectively, in group B compared to group A, and a lower positive predictive value. pVO2 ≤ 10 mL/kg/min and VE/VCO2 slope > 40 outperformed the traditional cut-offs. An ischemic etiology subanalysis showed similar results.

CONCLUSION

ISHLT thresholds showed a lower overall prognostic effectiveness in a contemporary HFrEF population. Novel parameters may be needed to improve risk stratification.

How Does the Method Used to Measure the VE/VCO2 Slope Affect Its Value? A Cross-Sectional and Retrospective Cohort Study

Cardiopulmonary exercise testing (CPET) was limited to peak oxygen consumption analysis (VO₂peak), and now the ventilation/carbon dioxide production (VE/VCO₂) slope is recognized as having independent prognostic value. Unlike VO₂peak, the VE/VCO₂ slope does not require maximal effort, making it more feasible. There is no consensus on how to measure the VE/VCO₂ slope; therefore, we assessed whether different methods affect its value. This is a retrospective study assessing sociodemographic data, left ventricular ejection fraction, CPET parameters, and indications of patients referred for CPET. The VE/VCO₂ slope was measured to the first ventilatory threshold (VT1-slope), secondary threshold (VT2-slope), and included all test data (full-slope). Of the 697 CPETs analyzed, 308 reached VT2. All VE/VCO₂ slopes increased with age, regardless of test indications. In patients not reaching VT2, the VT1-slope was 32 vs. 36 (p < 0.001) for the full-slope; in those surpassing VT2, the VT1-slope was 29 vs. 33 (p < 0.001) for the VT2-slope and 37 (all p < 0.001) for the full-slope. The mean difference between the submaximal and full-slopes was ±4 units, sufficient to reclassify patients from low to high risk for heart failure or pulmonary hypertension. We conclude that the method used for determining the VE/VCO₂ slope greatly influences the result, the significant variations limiting its prognostic value. The calculation method must be standardized to improve its prognostic value.

Cardiopulmonary Exercise Testing in Children and Young Adolescents after a Multisystem Inflammatory Syndrome: Physical Deconditioning or Residual Pathology?

Multisystem inflammatory syndrome in children (MIS-C) is a serious health condition that imposes a long-term follow-up. The purpose of our pilot study is to evaluate the usefulness of the cardiopulmonary stress test (CPET) in the follow-up after MIS-C. All patients admitted for MIS-C in our hospital in the 12 months preceding the date of observation were considered for inclusion in the study. Pre-existing cardio-respiratory diseases and/or the lack of collaboration were the exclusion criteria. At enrolment, each subject passed a cardiological examination, rest ECG, echocardiogram, 24 h Holter-ECG, blood tests, and a CPET complete of spirometry. A total of 20 patients met the inclusion criteria (11.76 ± 3.29 years, 13 male). In contrast to the normality of all second-level investigations, CPET showed lower-than-expected peakVO₂ and peak-oxygen-pulse values (50% of cases) and higher-than-expected VE/VCO_2-slope values (95% of cases). A statistically significant inverse correlation was observed between P-reactive-protein values at admission and peakVO₂/kg values (p = 0.034), uric acid values at admission, and peakVO₂ (p = 0.011) or peak-oxygen-pulse expressed as a percentage of predicted (p = 0.021), NT-proBNP values at admission and peakVO₂ expressed as a percentage of predicted (p = 0.046). After MIS-C (4-12 months) relevant anomalies can be observed at CPET, which can be a valuable tool in the follow-up after this condition.

Correlation between acylcarnitine/free carnitine ratio and cardiopulmonary exercise test parameters in patients with incident dialysis

Objective: Diminished physical capacity is common and progressive in patients undergoing dialysis, who are also prone to deficiency in carnitine, which plays a pivotal role in maintaining skeletal muscle and cardiac function. The present study aimed to evaluate the association of carnitine profile with exercise parameters in patients with incident dialysis. Design and Methods: This was a single-center cross-sectional study including 87 consecutive patients aged 20-90 years who were initiated on dialysis in Keio University Hospital between December 2019 and December 2022 and fulfilled the eligibility criteria. Exercise parameters were evaluated via cardiopulmonary testing (CPX) using the electronically braked STRENGTH ERGO 8 ergometer, whereas the carnitine profile was assessed by determining serum free carnitine (FC), acylcarnitine (AC) levels and AC/FC ratio. Results: The mean cohort age was 62.1 ± 15.2 years, with male and hemodialysis predominance (70% and 73%, respectively). AC/FC was 0.46 ± 0.15, and CPX revealed peak oxygen consumption (VO₂) of 13.9 ± 3.7 (mL/kg/min) with percent-predicted peak VO₂ of 53.6% ± 14.7% and minute ventilation (VE)/carbon dioxide output (VCO₂) slope of 35.1 ± 8.0. Fully-adjusted multivariate linear regression analysis showed that AC/FC was significantly associated with decreased peak VO₂ (β, -5.43 [95% confidence interval (CI), -10.15 to -0.70]) and percent-predicted peak VO₂ (β, -19.98 [95% CI, -38.43 to -1.52]) and with increased VE/VCO₂ slope (β, 13.76 [95% CI, 3.78-23.75]); FC and AC did not exhibit similar associations with these parameters. Moreover, only AC/FC was associated with a decreased peak work rate (WR), percent-predicted WR, anaerobic threshold, delta VO₂/delta WR, and chronotropic index. Conclusion: In patients on incident dialysis, exercise parameters, including those related to both skeletal muscle and cardiac function, were strongly associated with AC/FC, a marker of carnitine deficiency indicating altered fatty acid metabolism. Further studies are warranted to determine whether carnitine supplementation can improve exercise capacity in patients on incident dialysis.

Heart Failure with Reduced Ejection Fraction and Prognostic Scales: The Impact of Exercise Modality in Cardiopulmonary Exercise Tests

The cardiopulmonary exercise (CPET) test is an essential tool to determine the severity, prognosis, and need for invasive treatments in heart failure with reduced ejection fraction (HFrEF) but disregards the exercise modality. The present study aimed at analyzing the differences between treadmill and cycle-ergometer exercises. This was a prospective study, involving 65 patients with HfrEF who performed treadmill exercise followed by cycle-ergometer exercise 72 h later. We enrolled 65 patients, aged 58 ± 9 years, with an ejection fraction of 29 ± 9%. Peak VO2 was 20% greater (95% CI: 18−21%; p < 0.000) on the treadmill, and the ventilatory efficiency estimated by the VE/VCO2 slope (32 ± 8 vs. 34 ± 9; p < 0.05). The ventilatory response was greater on the treadmill: maximum ventilation (55 ± 16 vs. 46 ± 11 L/min; p < 0.000) and ventilatory reserve at the maximum effort (28 ± 17 vs. 41 ± 15%; p < 0.000). These values led to a change in the functional class of 23 (51%) patients and ventilatory class of 28 (47%) patients. Differences in the main parameters, including peak VO2 and VE/VCO2, impact prognostic scales and possible advanced treatments; therefore, the results should be interpreted in accordance with the exercise modality.

Usefulness of ventilatory inefficiency in predicting prognosis across the heart failure spectrum

Aims

The minute ventilation–carbon dioxide production relationship (VE/VCO₂ slope) is widely used for prognostication in heart failure (HF) with reduced left ventricular ejection fraction (LVEF). This study explored the prognostic value of VE/VCO₂ slope across the spectrum of HF defined by ranges of LVEF.

Methods and results

In this single‐centre retrospective observational study of 1347 patients with HF referred for cardiopulmonary exercise testing, patients with HF were categorized into HF with reduced (HFrEF, LVEF < 40%, n = 598), mid‐range (HFmrEF, 40% ≤ LVEF < 50%, n = 164), and preserved (HFpEF, LVEF ≥ 50%, n = 585) LVEF. Four ventilatory efficiency categories (VC) were defined: VC‐I, VE/VCO₂ slope ≤ 29; VC‐II, 29 < VE/VCO₂ slope < 36; VC‐III, 36 ≤ VE/VCO₂ slope < 45; and VC‐IV, VE/VCO₂ slope ≥ 45. The associations of these VE/VCO₂ slope categories with a composite outcome of all‐cause mortality or HF hospitalization were evaluated for each category of LVEF. Over a median follow‐up of 2.0 (interquartile range: 1.9, 2.0) years, 201 patients experienced the composite outcome. Compared with patients in VC‐I, those in VC‐II, III, and IV demonstrated three‐fold, five‐fold, and eight‐fold increased risk for the composite outcome. This incremental risk was observed across HFrEF, HFmrEF, and HFpEF cohorts.

Conclusions

Higher VE/VCO₂ slope is associated with incremental risk of 2 year all‐cause mortality and HF hospitalization across the spectrum of HF defined by LVEF. A multilevel categorical approach to the interpretation of VE/VCO₂ slope may offer more refined risk stratification than the current binary approach employed in clinical practice.

Revisiting and Implementing the Weber and Ventilatory Functional Classifications in Heart Failure by Cardiopulmonary Imaging Phenotyping

Background

In heart failure, the exercise gas exchange Weber (A to D) and ventilatory classifications (VC‐1 to VC‐4) historically define disease severity and prognosis. However, their applications in the modern heart failure population of any left ventricular ejection fraction combined with hemodynamics are undefined. We aimed at revisiting and implementing these classifications by cardiopulmonary exercise testing imaging.

Methods and Results

269 patients with heart failure with reduced (n=105), mid‐range (n=88) and preserved (n=76) ejection fraction underwent cardiopulmonary exercise testing imaging, primarily assessing the cardiac output (CO), mitral regurgitation, and mean pulmonary arterial pressure (mPAP)/CO slope. Within both classes, a progressively lower exercise CO, higher mPAP/CO slopes, and mitral regurgitation (P<0.01 all) were observed. After adjustment for age and sex, Cox proportional hazard regression analyses showed that Weber (hazard ratio [HR], 2.9; 95% CI, 1.8–4.7; P<0.001) and ventilatory classes (HR, 1.4; 95% CI, 1.1–2.0; P=0.017) were independently associated with outcome. The best stratification was observed when combining Weber (A/B or C/D) with severe ventilation inefficiency (VC‐4) (HR, 2.7; 95% CI, 1.6–4.8; P<0.001). At multivariable analysis the best hemodynamic determinants of peak oxygen consumption and ventilation to carbon dioxide production slope were CO (β‐coefficient, 0.72±0.16; P<0.001) and mPAP/CO slope (β‐coefficient, 0.72±0.16; P<0.001), respectively.

Conclusions

In the contemporary heart failure population, the Weber and ventilatory classifications maintain their prognostic ability, especially when combined. Exercise CO and mPAP/CO slope are the best predictors of peak oxygen consumption and ventilation to carbon dioxide production slope classifications representing the main targets of interventions to impact functional class and, likely, event rate.

Prognostic value of VE/VCO2 slope in overweight heart failure patients

BACKGROUND

A decreased hypercapnic ventilatory response of the overweight patients would lower the ventilation equivalent of carbon dioxide (VE/VCO₂) slope but worsen prognosis. The aim of this study was to compare the prognostic ability of the VE/VCO₂ slope and peak oxygen consumption (pVO₂) between normal and overweight heart failure (HF) patients.

METHODS

Prospective evaluation of ambulatory patients with reduced left ventricular ejection fraction who underwent baseline assessment with a cardiopulmonary exercise test. The primary endpoint was cardiac death or urgent heart transplantation in the 5-year period of follow-up. The predictive power of VE/VCO₂ slope and pVO₂ were compared (area under the curve (AUC) analysis and Hanley & McNeil test), in the subgroups of patients with body mass index (BMI) of 18.5-24.9 kg/m² and ≥ 25 kg/m². Statistical differences with a p value < 0.05 were considered significant.

RESULTS

There were 270 enrolled patients, with a mean BMI of 27 ± 4 kg/m². No differences between normal and overweight patients (38.0% vs 29.8%, P=0.170) were found during the 5-year period for the primary endpoint. The VE/VCO₂ slope was non-inferior to pVO₂ in both groups at 1, 3 and 5 years of follow-up. The comparison of VE/VCO₂ slope between groups revealed a significant lower AUC at 3 (0.921 vs 0.787, P=0.022) and 5 years (0.898 vs 0.787, P=0.044) of follow-up for overweight patients.

CONCLUSION

Despite VE/VCO₂ slope provides a discriminative power at least as good as pVO₂ for predicting adverse events in both normal and overweight HF patients, a significant lower predictive power was found in overweight patients.

Poor ventilatory efficiency during exercise may predict prolonged air leak after pulmonary lobectomy

Poor ventilatory efficiency, defined as the increase in minute ventilation relative to carbon dioxide production during exercise (VE/VCO2 slope), may be associated with dynamic hyperinflation and thereby promote the development of prolonged air leak (PAL) after lung resection. Consecutive lung lobectomy candidates (n = 96) were recruited for this prospective two-centre study. All subjects underwent pulmonary function tests and cardiopulmonary exercise testing prior to surgery. PAL was defined as the presence of air leaks from the chest tube on the 5th postoperative day and developed in 28 (29%) subjects. Subjects with PAL were not different in terms of age, sex, American Society of Anesthesiologists class, type of surgery (thoracotomy/video-assisted thoracoscopic surgery) and site of surgery (right/left lung; upper/lower lobes). Subjects with PAL had more frequent pleural adhesions (50% vs 21%; P = 0.006) and steeper VE/VCO2 slope (35 ± 7 vs 30 ± 5; P = 0.001). Stepwise logistic regression showed that only the presence of pleural adhesions [odds ratio (OR) 3.9, 95% confidence interval (CI) 1.4-10.9; P = 0.008] and VE/VCO2 slope (OR 1.1, 95% CI 1.0-1.2; P = 0.003) were independently associated with PAL (AUC 0.74, 95% CI 0.62-0.86). We conclude that a high VE/VCO2 slope during exercise may be helpful in identifying patients at greater risk for the development of PAL after lung lobectomy.

CLINICAL TRIAL REGISTRATION NUMBER

ClinicalTrials.gov identifier: NCT03498352.

Heart failure prognosis over time: how the prognostic role of oxygen consumption and ventilatory efficiency during exercise has changed in the last 20 years

AIMS

Exercise-derived parameters, specifically peak exercise oxygen uptake (peak VO₂ ) and minute ventilation/carbon dioxide relationship slope (VE/VCO₂ slope), have a pivotal prognostic value in heart failure (HF). It is unknown how the prognostic threshold of peak VO₂ and VE/VCO₂ slope has changed over the last 20 years in parallel with HF prognosis improvement.

METHODS AND RESULTS

Data from 6083 HF patients (81% male, age 61 ± 13 years), enrolled in the MECKI score database between 1993 and 2015, were retrospectively analysed. By enrolment year, four groups were generated: group 1 1993-2000 (n = 440), group 2 2001-2005 (n = 1288), group 3 2006-2010 (n = 2368), and group 4 2011-2015 (n = 1987). We compared the 10-year survival of groups and analysed how the overall risk (cardiovascular death, urgent heart transplantation, or left ventricular assist device implantation) changed over time according to peak VO₂ and VE/VCO₂ slope and to major clinical and therapeutic variables. At 10 years, a progressively higher survival from group 1 to group 3 was observed, with no further improvement afterwards. A 20% risk for peak VO₂ 15 mL/min/kg (95% confidence interval 16-13), 9 (11-8), 4 (4-2) and 5 (7-4) was observed in group 1, 2, 3, and 4, respectively, while the VE/VCO₂ slope value for a 20% risk was 32 (37-29), 47 (51-43), 59 (64-55), and 57 (63-52), respectively.

CONCLUSIONS

Heart failure prognosis improved over time up to 2010 in a HF population followed by experienced centres. The peak VO₂ and VE/VCO₂ slope cut-offs identifying a definite risk progressively decreased and increased over time, respectively. The prognostic threshold of peak VO₂ and VE/VCO₂ slope must be updated whenever HF prognosis improves.

Functional capacity and ventilatory efficiency are preserved in well-controlled people living with human immunodeficiency virus/acquired immunodeficiency syndrome

To verify and compare the responses of the cardiopulmonary variables to the incremental test in physically inactive people living with human immunodeficiency virus (HIV)/acquired immune deficiency syndrome (AIDS) (PLWHA) with well-controlled disease and physically inactive healthy subjects (non-HIV/AIDS). Participants performed a cardiopulmonary exercise test (CPX) on a treadmill. Data were analyzed using the Mann–Whitney test and Spearman correlation. Nine PLWHA (5 women) and 9 non-HIV/AIDS gender and activity level-matched controls were included in the data analysis. Data are expressed in median (range). No difference was shown in the PLWHA group when compared to the control group in functional capacity (peak oxygen consumption [VO_2peak]: 29.9 (20.9–36.4) mL/kg/min vs. 32.2 (24.5–39.4) mL/kg/min) and ventilatory efficiency (oxygen uptake efficiency slope [OUES]: 2,058 [1,474–3,204] vs. 2,612 [1,383–4,119]; minute ventilation carbon dioxide production slope: 27.4 [22.5–33.6] vs. 27.5 [20.4–38.1]). The results are also similar to maximal heart rate, oxygen pulse, gas exchange threshold, respiratory compensation point, heart rate recovery, and half-time of VO_2peak recovery. OUES had a strong correlation with VO_2peak in the PLWHA group (r_s=0.70, P=0.04) and control group (r_s=0.78, P=0.02). The results of this study indicate that functional capacity and ventilatory efficiency in PLWHA with well-controlled disease are preserved and are not different from sedentary subjects. In this sense, when CPX is unavailable, the aerobic assessment and prescription could be based on simpler procedures used in healthy subjects.

Influence of Inspiratory Muscle Training on Ventilatory Efficiency and Cycling Performance in Normoxia and Hypoxia

The aim of this study was to analyse the influence of inspiratory muscle training (IMT) on ventilatory efficiency, in normoxia and hypoxia, and to investigate the relationship between ventilatory efficiency and cycling performance. Sixteen sport students (23.05 ± 4.7 years; 175.11 ± 7.1 cm; 67.0 ± 19.4 kg; 46.4 ± 8.7 ml·kg⁻¹·min⁻¹) were randomly assigned to an inspiratory muscle training group (IMTG) and a control group (CG). The IMTG performed two training sessions/day [30 inspiratory breaths, 50% peak inspiratory pressure (Pimax), 5 days/week, 6-weeks]. Before and after the training period subjects carried out an incremental exercise test to exhaustion with gas analysis, lung function testing, and a cycling time trial test in hypoxia and normoxia. Simulated hypoxia (FiO₂ = 16.45%), significantly altered the ventilatory efficiency response in all subjects (p < 0.05). Pimax increased significantly in the IMTG whereas no changes occurred in the CG (time × group, p < 0.05). Within group analyses showed that the IMTG improved ventilatory efficiency (V_E/VCO₂ slope; EqCO₂VT₂) in hypoxia (p < 0.05) and cycling time trial performance [W_{TTmax (W)}; W_{TTmean (W)}; PTF_(W)] (p < 0.05) in hypoxia and normoxia. Significant correlations were not found in hypoxia nor normoxia found between ventilatory efficiency parameters (V_E/VCO₂ slope; LEqCO₂; EqCO₂VT₂) and time trial performance. On the contrary the oxygen uptake efficiency slope (OUES) was highly correlated with cycling time trial performance (r = 0.89; r = 0.82; p < 0.001) under both conditions. Even though no interaction effect was found, the within group analysis may suggest that IMT reduces the negative effects of hypoxia on ventilatory efficiency. In addition, the data suggest that OUES plays an important role in submaximal cycling performance.

Ventilatory efficiency slope correlates with functional capacity, outcomes, and disease severity in pediatric patients with pulmonary hypertension

BACKGROUND

Cardiopulmonary exercise testing is widely used in a variety of cardiovascular conditions. Ventilatory efficiency slope can be derived from submaximal exercise testing. The present study sought to evaluate the relationship between ventilatory efficiency slope and functional capacity, outcomes, and disease severity in pediatric patients with pulmonary hypertension.

METHODS

Seventy six children and young adults with a diagnosis of pulmonary hypertension (PH) performed 258 cardiopulmonary exercise tests from 2001 to 2011. Each individual PH test was matched to a control test. Ventilatory efficiency slope was compared to traditional measures of functional capacity and disease severity including WHO functional classification, peak oxygen consumption, and invasive measures of pulmonary arterial pressures and pulmonary vascular resistance.

RESULTS

Ventilatory efficiency slope was significantly higher in patients with pulmonary arterial hypertension, with an estimated increase of 7.2 for each increase in WHO class (p<0.0001), compared with normal control subjects (38.9 vs. 30.9, p<0.001). Ventilatory efficiency slope correlated strongly with invasive measures of disease severity including pulmonary vascular resistance index (r =0.61), pulmonary artery pressure (r =0.58), mean pulmonary artery pressure/mean aortic pressure ratio (r =0.52), and peak VO2 (r=-0.58). Ventilatory efficiency slope in 12 patients with poor outcomes (9 death, 3 lung transplant), was significantly elevated compared to patients who did not (51.1 vs. 37.9, p<0.001).

CONCLUSIONS

Ventilatory efficiency slope correlates well with invasive and noninvasive markers of disease severity including peak VO2, WHO functional class, and catheterization variables in pediatric patients with PH. Ventilatory efficiency slope may be a useful noninvasive marker for disease severity.

Cardiac resynchronization therapy improves minute ventilation/carbon dioxide production slope and skeletal muscle capillary density without reversal of skeletal muscle pathology or inflammation

AIMS

We evaluated the effects of cardiac resynchronization therapy (CRT) on skeletal muscle pathology and inflammation in patients with heart failure.

METHODS AND RESULTS

Stable patients (n = 21, 14 males, mean age 70 ± 7 years) with symptomatic heart failure (mean left ventricular ejection fraction 24 ± 6%) and an indication for CRT were included. Ergospirometry, skeletal muscle open biopsy, and blood sampling were performed prior to implantation and after 6 months of CRT. After CRT there was a reduction in both left ventricular end-diastolic diameter (LVEDD; 6.8 ± 0.8 vs. 6.3 ± 0.7 cm, P < 0.001) and native QRS duration (D) minus biventricular paced QRSD (172.9 ± 23 vs. 136.3 ± 23 ms, P ≤ 0.001). These changes were associated with an increase in peak slope oxygen uptake (consumption) (VO₂) (13.3 ± 2.2 vs. 14.5 ± 2.6 mL/kg/min, P = 0.07) and an improvement in the minute ventilation/carbon dioxide production slope (VE/VCO₂) slope (41.6 ± 7.4 vs. 39.1 ± 5.6, P = 0.012). There were no statistically significant changes in levels of pro-inflammatory cytokines, in mediators of mitochondrial biosynthesis or skeletal muscle pathology, except for an increase in skeletal muscle capillary density (4.5 ± 2.4 vs. 7.7 ± 3.3%, P = 0.002). Both the reduction of QRS duration and the increase in peak VO₂ correlated significantly with the change in mitochondrial density (r = 0.57, P = 0.008 and r = 0.54, P = 0.027, respectively).

CONCLUSION

Cardiac resynchronization therapy, with improved functional status and reduced LVEDD resulted in increased peak VO₂, improvement in VE/VCO₂ slope and capillary density in skeletal muscle, with no reduction in systemic pro-inflammatory cytokines, increase in intramuscular levels of mediators of mitochondrial biosynthesis or improvement in skeletal muscle ultrastructure per se. ClinicalTrials.gov Identifier: NCT01019915.

Cardio-pulmonary exercise testing: An objective approach to pre-operative assessment to define level of perioperative care

Cardiopulmonary exercise testing is a non-invasive, objective method of assessing integrated response of heart, lungs and musculoskeletal system to incremental exercise. Though it has been in use for a few decades, the recent rise in its use as a preoperative test modality is reviewed. A brief account of cardiopulmonary exercise test, as it is carried out in practice and its applications, is given. The physiological basis is explained and relationship of pathophysiology of poor exercise capacity with various test variables is discussed. Its use for prediction of postoperative morbidity in various noncardiopulmonary surgical procedures is reviewed.