Chronotropic incompentence and functional capacity in chronic heart failure: no role of β-blockers and β-blocker dose

Low chronotropic response in post-myocardial infarction exercise test predicts worse prognosis in patients with preserved or mildly reduced left ventricular ejection fraction

BACKGROUND

Chronotropic incompetence is prevalent in post-myocardial infarction (MI) patients and linked to reduced exercise capacity. However, its prognostic significance and the determination of threshold values for prognosis remain unclear.

METHODS

Ninety-six post-MI patients with left ventricular ejection fraction (LVEF) ≥ 40 % at four weeks post-event were assessed. All underwent combined exercise stress echocardiography and cardiopulmonary exercise testing (CPET-SE). The chronotropic response was expressed as a percentage of the maximal predicted heart rate (%MPHR) at peak exercise. The primary endpoint was a composite of all-cause mortality or unplanned hospitalization for coronary syndromes or heart failure.

RESULTS

Eighty-six patients completed follow-up (median: 4.0 years [IQR 2.0, 5.6]). The median age was 60 years (IQR 53, 65); 67 % were male, 86 % on beta-blockers. The median LVEF was 57 % (IQR 51, 62), and the median peak VO2 was 19 mL/kg/min (IQR 15, 22). Fifteen composite endpoint events, including three deaths, occurred. Multivariate Cox regression showed %MPHR (HR 0.95, 95 % CI 0.92-0.98) and smoking history (HR 2.8, 95 % CI 1.1-7.4) were associated with the primary endpoint. A %MPHR threshold of 67 % best predicted the primary endpoint (AUC 73 %, PPV 29 %, NPV 95 %, sensitivity 87 %, specificity 55 %). Patients with %MPHR <67 % had significantly more composite endpoint events than those with %MPHR ≥67 % (p = 0.002).

CONCLUSIONS

A chronotropic response below 67 % of the maximal predicted heart rate is a negative prognostic marker in post-MI patients with preserved or mildly reduced LVEF. This threshold may help risk-stratify and guide management in this population.

Prevalence and functional impact of chronotropic incompetence in amyloid cardiomyopathy: a multicentre analysis

BACKGROUND

Little evidence is available about heart rate (HR) response to exercise as well as its relationship with functional capacity in amyloid cardiomyopathy. Then, in a multicentre cohort of patients with amyloid cardiomyopathy, we investigated the prevalence of chronotropic incompetence (CI) and its relationships with cardiopulmonary exercise testing (CPET) variables.

METHODS

Data from 172 outpatients with amyloid cardiomyopathy who performed a maximal CPET and who had no significant rhythm disorders were analysed.

RESULTS

The prevalence of CI differed depending on the age-predicted peak HR (pHR%) cut-off value adopted, ranging from 16% to 59%. pHR% correlated non-linearly with peak oxygen uptake (pVO2), either as expressed as a percentage of the maximum predicted or as mL/kg/min (p<0.001). Although to a lesser extent, pHR% correlated inversely with ventilatory efficiency (p<0.001). A pHR%≤75% resulted in the most accurate cut-off value in identifying a moderate-to-severe exercise impairment (sensitivity 72%; specificity 73%; area under the curve 77.2%).

CONCLUSIONS

CI is prevalent in patients with amyloid cardiomyopathy in sinus rhythm, its percentage varying according to the pHR% cut-off value. A blunted exercise-induced HR response correlated with a poor exercise capacity even in this setting of patients, a pHR%≤75% cut-off value being possibly useful in centres without CPET availability to identify a significant exercise impairment.

Association of chronotropic incompetence with reduced cardiorespiratory fitness in older adults with HIV

OBJECTIVE

Understanding the physiological drivers of reduced cardiorespiratory fitness in people with HIV (PWH) will inform strategies to optimize healthspan. Chronotropic incompetence is common in heart failure and associated with low cardiorespiratory fitness yet is understudied in PWH. The objective was to determine the prevalence of chronotropic incompetence and its relationship with cardiorespiratory fitness.

DESIGN

Participants were PWH at least 50 years of age with no prior history of heart failure or coronary heart disease who were enrolled in a randomized exercise trial. Baseline cardiopulmonary exercise testing (CPET) was used to measure cardiorespiratory fitness as peak oxygen consumption (VO2peak) and calculate the chronotropic index from heart rate values. Chronotropic incompetence was defined as an index less than 80%.

RESULTS

The 74 participants were on average 61 years old, 80% Black or African American, and 93% men. Chronotropic incompetence was present in 31.1%. VO2peak was significantly lower among participants with chronotropic incompetence compared with participants without chronotropic incompetence [mean (SD) ml/min/kg: 20.9 (5.1) vs. 25.0 (4.5), P = 0.001]. Linear regression showed that chronotropic incompetence and age were independent predictors of VO2peak, but smoking and comorbidity were not. The chronotropic index correlated with VO2peak (r = 0.48, P < 0.001).

CONCLUSION

Among older PWH without heart failure or coronary heart disease, chronotropic incompetence was present in approximately one-third of individuals and was associated with clinically relevant impaired cardiorespiratory fitness. Investigation of chronotropic incompetence in large cohorts which includes PWH and heart failure may contribute to strategies that promote healthy aging with HIV infection and offer a preclinical window for intervention.

What about chronotropic incompetence in heart failure with mildly reduced ejection fraction? Clinical and prognostic implications from the Metabolic Exercise combined with Cardiac and Kidney Indexes score dataset

AIMS

Chronotropic incompetence (CI) is a strong predictor of outcome in heart failure with reduced ejection fraction, however no data on its clinical and prognostic impacts in heart failure with mildly reduced ejection fraction (HFmrEF) are available. Therefore, the study aims to investigate, in a large multicentre HFmrEF cohort, the prevalence of CI as well as its relationship with exercise capacity and its prognostic role over the cardiopulmonary exercise testing (CPET) parameters.

METHODS AND RESULTS

Within the Metabolic Exercise combined with Cardiac and Kidney Indexes (MECKI) database, we analysed data of 864 HFmrEF out of 1164 stable outpatients who performed a maximal CPET at the cycle ergometer and who had no significant rhythm disorders or comorbidities. The primary study endpoint was cardiovascular (CV) death. All-cause death was also explored. Chronotropic incompetence prevalence differed depending on the method (peak heart rate, pHR% vs. pHR reserve, pHRR%) and the cut-off adopted (pHR% from ≤75% to ≤60% and pHRR% ≤ 65% to ≤50%), ranging from 11% to 62%. A total of 84 (9.7%) CV deaths were collected, with 39 (4.5%) occurring within 5 years. At multivariate analysis, both pHR% [hazard ratio 0.97 (0.95-0.99), P < 0.05] and pHRR% [hazard ratio 0.977 (0.961-0.993), P < 0.01] were associated with the primary endpoint. A pHR% ≤ 75% and a pHRR% ≤ 50% represented the most accurate cut-off values in predicting the outcome.

CONCLUSION

The study suggests an association between blunted exercise-HR response, functional capacity, and CV death risk among patients with HFmrEF. Whether the CI presence might be adopted in daily HFmrEF management needs to be addressed in larger prospective studies.

Chronotropic Incompetence During Exercise Testing as a Marker of Autonomic Dysfunction in Individuals with Early Parkinson's Disease

BACKGROUND

An attenuated heart rate response to exercise, termed chronotropic incompetence, has been reported in Parkinson's disease (PD). Chronotropic incompetence may be a marker of autonomic dysfunction and a cause of exercise intolerance in early stages of PD.

OBJECTIVE

To investigate the relationship between chronotropic incompetence, orthostatic blood pressure change (supine - standing), and exercise performance (maximal oxygen consumption, VO2peak) in individuals with early PD within 5 years of diagnosis not on dopaminergic medications.

METHODS

We performed secondary analyses of heart rate and blood pressure data from the Study in Parkinson's Disease of Exercise (SPARX).

RESULTS

128 individuals were enrolled into SPARX (63.7±9.3 years; 57.0% male, 0.4 years since diagnosis [median]). 103 individuals were not taking chronotropic medications, of which 90 had a normal maximal heart rate response to exercise testing (155.3±14.0 bpm; PDnon-chrono) and 13 showed evidence of chronotropic incompetence (121.3±11.3 bpm; PDchrono, p < 0.05). PDchrono had decreased VO2peak compared to PDnon-chrono (19.7±4.5 mL/kg/min and 24.3±5.8 mL/kg/min, respectively, p = 0.027). There was a positive correlation between peak heart rate during exercise and the change in systolic blood pressure from supine to standing (r = 0.365, p < 0.001).

CONCLUSIONS

A subgroup of individuals with early PD not on dopaminergic medication had chronotropic incompetence and decreased VO2peak, which may be related to autonomic dysfunction. Evaluation of both heart rate responses to incremental exercise and orthostatic vital signs may serve as biomarkers of early autonomic impairment and guide treatment. Further studies should investigate whether cardiovascular autonomic dysfunction affects the ability to exercise and whether exercise training improves autonomic dysfunction.

Beta-Adrenergic Receptor Blockade Effects on Cardio-Pulmonary Exercise Testing in Healthy Young Adults: A Randomized, Placebo-Controlled Trial

BACKGROUND

Beta-blockers are increasingly prescribed while the effects of beta-adrenergic receptor blockade on cardio-pulmonary exercise test (CPET)-derived parameters remain under-studied.

METHODS

Twenty-one young healthy adults repeated three CPET at the same time with an interval of 7 days between each test. The tests were performed 3 h after a random, double-blind, cross-over single-dose intake of placebo, 2.5 mg or 5.0 mg bisoprolol, a cardio-selective beta1-adrenoreceptor antagonist. Gas exchange, heart rate (HR) and blood pressure (BP) were measured at rest and during cyclo-ergometric incremental CPET.

RESULTS

Maximal workload and VO₂max were unaffected by the treatment, with maximal respiratory exchange ratio > 1.15 in all tests. A beta-blocker dose-dependent effect reduced resting and maximal BP and HR and the chronotropic response to exercise, evaluated by the HR/VO₂ slope (placebo: 2.9 ± 0.4 beat/ml/kg; 2.5 mg bisoprolol: 2.4 ± 0.5 beat/ml/kg; 5.0 mg bisoprolol: 2.3 ± 0.4 beat/ml/kg, p < 0.001). Ventilation efficiency measured by the VE/VCO₂ slope and the ventilatory equivalent for CO₂ at the ventilatory threshold were not affected by beta1-receptor blockade. Post-exercise chronotropic recovery measured after 1 min was enhanced under beta1-blocker (placebo: 26 ± 7 bpm; 2.5 mg bisoprolol: 32 ± 6 bpm; 5.0 mg bisoprolol: 33 ± 6 bpm, p < 0.01).

CONCLUSION

The present results suggest that a single dose of bisoprolol does not affect metabolism, respiratory response and exercise capacity. However, beta-adrenergic blockade dose dependently reduces exercise hemodynamic response by lowering BP and the chronotropic response.

Old and new equations for maximal heart rate prediction in patients with heart failure and reduced ejection fraction on beta-blockers treatment: results from the MECKI score data set

AIMS

Predicting maximal heart rate (MHR) in heart failure with reduced ejection fraction (HFrEF) still remains a major concern. In such a context, the Keteyian equation is the only one derived in a HFrEF cohort on optimized β-blockers treatment. Therefore, using the Metabolic Exercise combined with Cardiac and Kidney Indexes (MECKI) data set, we looked for a possible MHR equation, for an external validation of Keteyien formula and, contextually, for accuracy of the historical MHR formulas and their relationship with the HR measured at the anaerobic threshold (AT).

METHODS AND RESULTS

Data from 3487 HFrEF outpatients on optimized β-blockers treatment from the MECKI data set were analyzed. Besides excluding all possible confounders, the new equation was derived by using HR data coming from maximal cardiopulmonary exercise test. The simplified derived equation was [109-(0.5*age) + (0.5*HR rest) + (0.2*LVEF)-(5 if haemoglobin <11 g/dL)]. The R2 and the standard error of the estimate were 0.24 and 17.5 beats min-1 with a mean absolute percentage error (MAPE) = 11.9%. The Keteyian equation had a slightly higher MAPE = 12.3%. Conversely, the Fox and Tanaka equations showed extremely higher MAPE values. The range 75-80% of MHR according to the new and the Keteyian equations was the most accurate in identifying the HR at the AT (MAPEs = 11.3-11.6%).

CONCLUSION

The derived equation to estimate the MHR in HFrEF patients, by accounting also for the systolic dysfunction degree and anaemia, improved slightly the Keteyian formula. Both formulas might be helpful in identifying the true maximal effort during an exercise test and the intensity domain during a rehabilitation programme.

Heart Rate Response to Exercise and Recovery: INDEPENDENT PROGNOSTIC MEASURES IN PATIENTS WITHOUT KNOWN MAJOR CARDIOVASCULAR DISEASE

PURPOSE

Heart rate response during exercise testing (ET) provides valuable prognostic information. Limited data are available regarding the prognostic interplay of heart rate (HR) measured at rest, exercise and recovery phases of ET, and its ability to predict risk beyond exercise capacity.

METHODS

Retrospective analysis of treadmill ETs was performed by the Bruce protocol in patients aged 35-75 yr without known cardiovascular disease (CVD; n = 13 887; 47% women). Heart rate recovery at 2 min (HRR2; defined abnormal <42 beats) and chronotropic index (CI; defined abnormal <80%, determined as age-predicted HR reserve) were analyzed in association with the risk of developing myocardial infarction, stroke, or death (major adverse cardiovascular event [MACE]) during median follow-up of 6.5 yr.

RESULTS

The HRR2 <42 beats and CI <80% were each associated with increased risk of MACE: adjusted hazard ratios with 95% confidence interval 1.47: 1.27-1.72 and 1.66: 1.42-1.93, P < .001, respectively, evident also when analyzed as continuous variables. Strength of association of HRR2 and CI with outcome was attenuated but remained significant with further adjustment for exercise duration and metabolic equivalents. Having both HRR2 and CI abnormal compared with only one measure abnormal was associated with hazard ratios with 95% confidence interval of 1.66: 1.38-2.00 and 1.48: 1.22-1.79 for MACE, before and after adjustment for cardiorespiratory fitness (CRF). The degree of CRF (low vs mid/high) did not modify the prognostic effect of HRR2 and CI (P-for-interaction nonsignificant).

CONCLUSIONS

Both HRR2 and CI provide independent prognostic information beyond CRF in patients without CVD referred for ET. The predictive ability is more pronounced when both abnormal HR measures coexist.

Cardiopulmonary exercise test in patients with refractory angina: functional and ischemic evaluation

OBJECTIVES

Refractory angina (RA) is a chronic condition clinically characterized by low effort tolerance; therefore, physical stress testing is not usually requested for these patients. Cardiopulmonary exercise testing (CPET) is considered a gold standard examination for functional capacity evaluation, even in submaximal tests, and it has gained great prominence in detecting ischemia. The authors aimed to determine cardiorespiratory capacity by using the oxygen consumption efficiency slope (OUES) in patients with refractory angina. The authors also studied the O2 pulse response by CPET and the association of ischemic changes with contractile modifications by exercise stress echocardiography (ESE).

METHODS

Thirty-one patients of both sexes, aged 45 to 75 years, with symptomatic (Canadian Cardiovascular Society class II to IV) angina who underwent CPET on a treadmill and exercise stress echocardiography on a lower limb cycle ergometer were studied. ClinicalTrials.gov: NCT03218891.

RESULTS

The patients had low cardiorespiratory capacity (OUES of 1.74 ± 0.4 L/min; 63.9±14.7% of predicted), and 77% of patients had a flattening or drop in O2 pulse response. There was a direct association between Heart Rate (HR) at the onset of myocardial ischemia detected by ESE and HR at the onset of flattening or drop in oxygen pulse response detected by CPET (R = 0.48; p = 0.019).

CONCLUSION

Patients with refractory angina demonstrate low cardiorespiratory capacity. CPET shows good sensitivity for detecting abnormal cardiovascular response in these patients with a significant relationship between flattening O2 pulse response during CEPT and contractile alterations detected by exercise stress echocardiography.

The Impact of beta blockade on the cardio-respiratory system and symptoms during exercise

Background

Beta blockers prolong life in patients with cardiovascular diseases. Negative chronotropic and inotropic effects carry the potential to adversely effect peripheral skeletal and airway smooth muscle contributing to further fatigue, dyspnea and exercise intolerance.

Research questions

Do beta-blockers reduce maximal power output (MPO), VO2 max, cardiorespiratory responses, increase the perceived effort required to cycle and breath during cardiopulmonary exercise tests (CPET) and limit the capacity to exercise?

Methods

Retrospective observational study of subjects performing CPET to capacity from 1988 to 2012. Subjects with and without beta-blockers were compared: baseline physiological characteristics, MPO, VO₂ max, heart rate max, ventilation responses and perceived exertion required to cycle and breathe (modified Borg scale). Forward stepwise linear additive regression was performed with MPO as the dependent factor with height, age, gender, muscle strength, FEV1 and DLCO as independent contributors.

Results

42,771 subjects were included 7,787 were receiving beta-blocker [mean age 61 yrs, BMI 28.40 kg/m², 9% airflow obstruction (FEV1/FVC<0.7)] and 34,984 were not [mean age 51yrs, BMI 27.40 kg/m², 11% airflow obstruction]. Heart rate was lower by 18.2% (95% C.I. 18.15–18.38) (p<0.0001) while Oxygen pulse (VO₂/HR) was higher by 19.5% (95% C.I. 19.3–19.7) in those receiving beta blockers. Maximum power output (MPO) was 3.3% lower in those taking beta-blockers. The perceived effort required to cycle and breathe (mBorg) was 8% lower in those taking beta-blockers.

Interpretation

Increases in oxygen pulse minimize the reduction in exercise intolerance and symptom handicap associated with beta-blockers.

•

Comprehensive set of exercise physiology measurements in a large cohort, to delineate any hazardous effects of beta blockade.

•

Beta-blockers attenuate the heart rate at rest and during exercise.

•

Beta-blockade has no meaningful effects on muscle strength, breathing capacity or exercise induced bronchoconstriction.

•

Beta Blockers were not associated with a reduction in Maximal power output.

•

Increases in Oxygen pulse minimize the reduction in exercise intolerance and symptom handicap associated with beta-blockers.

Effect of β-Blocker Withdrawal on Functional Capacity in Heart Failure and Preserved Ejection Fraction

BACKGROUND

Chronotropic incompetence has shown to be associated with a decrease in exercise capacity in heart failure with preserved ejection fraction (HFpEF), yet β-blockers are commonly used in HFpEF despite the lack of robust evidence.

OBJECTIVES

This study aimed to evaluate the effect of β-blocker withdrawal on peak oxygen consumption (peak Vo₂) in patients with HFpEF and chronotropic incompetence.

METHODS

This is a multicenter, randomized, investigator-blinded, crossover clinical trial consisting of 2 treatment periods of 2 weeks separated by a washout period of 2 weeks. Patients with stable HFpEF, New York Heart Association functional classes II and III, previous treatment with β-blockers, and chronotropic incompetence were first randomized to withdrawing from (arm A: n = 26) versus continuing (arm B: n = 26) β-blocker treatment and were then crossed over to receive the opposite intervention. Changes in peak Vo₂ and percentage of predicted peak Vo₂ (peak Vo₂%) measured at the end of the trial were the primary outcome measures. To account for the paired-data nature of this crossover trial, linear mixed regression analysis was used.

RESULTS

The mean age was 72.6 ± 13.1 years, and most of the patients were women (59.6%) in New York Heart Association functional class II (66.7%). The mean peakVo₂ and peak Vo₂% were 12.4 ± 2.9 mL/kg/min, and 72.4 ± 17.8%, respectively. No significant baseline differences were found across treatment arms. Peak Vo₂ and peak Vo₂% increased significantly after β-blocker withdrawal (14.3 vs 12.2 mL/kg/min [Δ +2.1 mL/kg/min]; P < 0.001 and 81.1 vs 69.4% [Δ +11.7%]; P < 0.001, respectively).

CONCLUSIONS

β-blocker withdrawal improved maximal functional capacity in patients with HFpEF and chronotropic incompetence. β-blocker use in HFpEF deserves profound re-evaluation. (β-blockers Withdrawal in Patients With HFpEF and Chronotropic Incompetence: Effect on Functional Capacity [PRESERVE-HR]; NCT03871803; 2017-005077-39).

Impact of β-Blockers on Heart Rate and Oxygen Uptake During Exercise and Recovery in Older Patients With Heart Failure With Preserved Ejection Fraction

PURPOSE

The study aimed to investigate the differences in oxygen uptake ((Equation is included in full-text article.)O2) and heart rate (HR) (at rest, submaximal exercise, peak exercise, and recovery) in patients with heart failure with preserved ejection fraction (HFpEF) with β-blockers (BB) or without BB treatment (NBB) and to analyze the relationship between HR reserve (HRresv) and peak (Equation is included in full-text article.)O2 ((Equation is included in full-text article.)O2peak) in BB and NBB.

METHODS

A total of 174 HFpEF patients (>65 yr; BB, n = 59; NBB, n = 115) were assessed with a cardiopulmonary exercise test to peak exertion using an incremental protocol. After 5 min of supine rest, HR and (Equation is included in full-text article.)O2 (HRrest, (Equation is included in full-text article.)O2rest) at submaximal exercise (HRsubmax, (Equation is included in full-text article.)O2submax), at peak exercise (HRpeak, (Equation is included in full-text article.)O2peak), at 1 min of passive recovery (HRrec1), HRresv (HRpeak- HRrest), and HR recovery (HRrecov = HRpeak- HRrec1) were evaluated.

RESULTS

Analysis showed that HRrest (66.0 ± 12.2 vs 69.7 ± 10.6 bpm), HRsubmax (91.7 ± 16.2 vs 98.6 ± 15.2 bpm), and HRrec1 (102.9 ± 18.9 vs 109.4 ± 16.9 bpm) were significantly lower (P ≤ .05) in BB than in NBB, respectively. However, there were no significant differences (P > .05) between the BB and the NBB for HRpeak, HRresv, HRrecov, (Equation is included in full-text article.)O2rest, (Equation is included in full-text article.)O2submax, and (Equation is included in full-text article.)O2peak. A significant relationship was found between HRresv and (Equation is included in full-text article.)O2peak values in both groups (BB, r = 0.52; NBB, r = 0.49, P < .001).

CONCLUSIONS

The nonsignificant differences in HRpeak, HRresv, HRrecov, or (Equation is included in full-text article.)O2 values between BB and NBB HFpEF patients, along with significant correlation between HRresv and (Equation is included in full-text article.)O2peak, suggest that these measures may have equal utility in prognostic and functional assessment as well as clinical applications, including the prescription of exercise, in elderly HFpEF patients.

Exercise Dynamic of Patients with Chronic Heart Failure and Reduced Ejection Fraction

PURPOSE OF REVIEW

Exercise causes various dynamic changes in all body parts either in healthy subject or in heart failure (HF) patients. The present review of current knowledge about HF patients with reduced ejection fraction focuses on dynamic changes along a "metabo-hemodynamic" perspective.

RECENT FINDINGS

Studies on the dynamic changes occurring during exercise span many years. Thanks to the availability of advanced methods, it is nowadays possible to properly characterize respiratory, hemodynamic, and muscular function adjustments and their mismatch with the pulmonary and systemic circulations. Exercise is a dynamic event that involves several body functions. In HF patients, it is important to know at what level the limitation takes place in order to better manage these patients and to optimize therapeutic strategies.

Effects of chronotropic incompetence on exercise capacity in people with heart failure versus age-matched controls

Chronotropic incompetence (CI) is an inability to adequately raise heart rate during physiological stress. We established CI prevalence and exercise capacity in heart failure versus healthy age-matched controls. We conducted a systematic search (1966-July 1, 2020) and meta-analysis of studies reporting peak VO₂ in people with heart failure with reduced (HFrEF) and preserved (HFpEF) left ventricular ejection fraction and controls. Seventeen studies of 4410 participants were included, 4167 with heart failure and 243 age-matched controls. In both heart failure phenotypes, CI was more prevalent in HFrEF (51.7%) and HFpEF (55.8%) than in healthy controls (9%). Mortality was 24% higher in people with HFrEF and CI versus those with HFrEF and without CI; OR -1.24 (95% CI -2.20 to -0.28; p = 0.01). People with heart failure and CI had lower peak VO₂ than those without CI (MD) -3.30 ml kg^-1 min^-1 (95% CI -4.25 to -2.35, p < 0.01), and this was primarily driven by the HFrEF sub-population (MD) -3.86 ml kg^-1 min^-1 (95% CI -4.83 to -2.89, p < 0.01). Maximum heart rate MD -37.51 beats min^-1 (95% CI -41.99 to -33.03, p < 0.01) and maximum-resting heart rate were lower MD -29.44 beats min^-1 (95% CI -34.55 to -24.33, p < 0.01) in people with heart failure with CI vs without CI. People with heart failure and CI demonstrated similar respiratory exchange ratios (RER) to people with heart failure but without CI; (MD) -0.02 (95% CI -0.03 to -0.01), p < 0.01, suggesting that poor effort was unlikely to explain CI. CI is more prevalent in heart failure than in age-matched controls and although it is associated with lower peak VO₂ in HFrEF, it is unrelated to the lower peak VO₂ in HFpEF. RER values suggest poor effort is unlikely to explain these findings.

Chronotropic Incompetence Limits Aerobic Exercise Capacity in Patients Taking Beta-Blockers: Real-Life Observation of Consecutive Patients

Background: Chronotropic incompetence in patients taking beta-blockers is associated with poor prognosis; however, its impact on exercise capacity (EC) remains unclear. Methods: We analyzed data from consecutive patients taking beta-blockers referred for cardiopulmonary exercise testing to assess EC. Chronotropic incompetence was defined as chronotropic index (CI) ≤ 62%. Results: Among 140 patients all taking beta-blockers (age 61 ± 9.7 years; 73% males), 64% with heart failure, chronotropic incompetence was present in 80.7%. EC assessed as peak oxygen uptake was lower in the group with chronotropic incompetence, 18.3 ± 5.7 vs. 24.0 ± 5.3 mL/kg/min, p < 0.001. EC correlated positively with CI (β = 0.14, p < 0.001) and male gender (β = 5.12, p < 0.001), and negatively with age (β = −0.17, p < 0.001) and presence of heart failure (β = −3.35, p < 0.001). Beta-blocker dose was not associated with EC. Partial correlation attributable to CI accounted for more than one-third of the variance in EC explained by the model (adjusted R² = 59.8%). Conclusions: In patients taking beta-blockers, presence of chronotropic incompetence was associated with lower EC, regardless of the beta-blocker dose. CI accounted for more than one-third of EC variance explained by our model.

Clinical and Physiologic Implications of Negative Cardiopulmonary Interactions in Coexisting Chronic Obstructive Pulmonary Disease-Heart Failure

Chronic obstructive pulmonary disease (COPD) and heart failure with reduced ejection fraction (HF) frequently coexist in the elderly. Expiratory flow limitation and lung hyperinflation due to COPD may adversely affect central hemodynamics in HF. Low lung compliance, increased alveolar-capillary membrane thickness, and abnormalities in pulmonary perfusion because of HF further deteriorates lung function in COPD. We discuss how those negative cardiopulmonary interactions create challenges in clinical interpretation of pulmonary function and cardiopulmonary exercise tests in coexisting COPD-HF. In the light of physiologic concepts, we also discuss the influence of COPD or HF on the current medical treatment of each disease.

Chronotropic Incompetence in Chronic Heart Failure

Chronotropic incompetence (CI) is generally defined as the inability to increase the heart rate (HR) adequately during exercise to match cardiac output to metabolic demands. In patients with heart failure (HF), however, this definition is unsuitable because metabolic demands are unmatched to cardiac output in both conditions. Moreover, HR dynamics in patients with HF differ from those in healthy subjects and may be affected by β-blocking medication. Nevertheless, it has been demonstrated that CI in HF is associated with reduced functional capacity and poor survival. During exercise, the normal heart increases both stroke volume and HR, whereas in the failing heart, contractility reserve is lost, thus rendering increases in cardiac output primarily dependent on cardioacceleration. Consequently, insufficient cardioacceleration because of CI may be considered a major limiting factor in the exercise capacity of patients with HF. Despite the profound effects of CI in this specific population, the issue has drawn limited attention during the past years and is often overlooked in clinical practice. This might partly be caused by a lack of standardized approach to diagnose the disease, further complicated by changes in HR dynamics in the HF population, which render reference values derived from a normal population invalid. Cardiac implantable electronic devices (implantable cardioverter defibrillator; cardiac resynchronization therapy) now offer a unique opportunity to study HR dynamics and provide treatment options for CI by rate-adaptive pacing using an incorporated sensor that measures physical activity. This review provides an overview of disease mechanisms, diagnostic strategies, clinical consequences, and state-of-the-art device therapy for CI in HF.

Heart rate during exercise: mechanisms, behavior, and therapeutic and prognostic implications in heart failure patients with reduced ejection fraction

Exercise intolerance is a typical manifestation of patients affected by heart failure with reduced ejection fraction (HFrEF); however, the relationship among functional capacity, mortality, and exercise-induced heart rate response during exercise remains unclear in either sinus rhythm or atrial fibrillation subjects. Heart rate increase during incremental load exercise has a typical pattern in normal subjects, whereas it is commonly compromised in HFrEF patients, mainly due to the imbalance of the autonomic nervous system. In the present review, we aim to describe the behavior of heart rate during exercise in normal subjects and in HFrEF patients in sinus rhythm and atrial fibrillation, understanding and explaining the mechanism leading to a different exercise performance and functional limitation. Moreover, the role of chronotropic incompetence and the need of standardizing the cutoff criteria are also discussed in order to clarify the clinical importance, the prognostic relevance, and the potential therapeutic implications of this condition. Looking into the relative contribution and interaction of heart rate response during exercise might represent an important issue to guide individualized therapeutic interventions and prognostic assessment in HFrEF patients.

Heart rate response to graded exercise test of elderly subjects in different ranges of TSH levels

OBJECTIVE

Life expectancy is increasing worldwide and studies have been demonstrating that elevated serum thyroid stimulating hormone (TSH) concentration in elderly is associated with some better health outcomes. This elevation is somewhat physiological as aging. The aim of this study was to investigate the heart rate (HR) response during a graded exercise test and its recovery in healthy elderly, comparing subjects within serum TSH in the lower limit of reference range to those within the TSH in the upper limit.

SUBJECTS AND METHODS

A cross-sectional study was conducted with 86 healthy elderly aged 71.5 ± 5.1 years, with serum TSH between 0.4 - 4.0 mUl/mL. The participants were divided into two groups according to TSH level: < 1.0 mUl/mL (n = 13) and ≥ 1.0 µUI/mL (n = 73). All participants performed an ergometric test on a treadmill. The HR was recorded and analyzed at rest, during exercise and during the three minutes immediately after exercise.

RESULTS

No differences were observed in relation to HR at peak of exercise (TSH < 1.0 µUI/mL: 133.9 ± 22.5 bpm vs. TSH ≥ 1.0 µUI/mL: 132.4 ± 21.3 bpm; p = 0.70) and during the first minute of recovery phase (TSH < 1.0 µUI/mL: 122.3 ± 23.1 bpm vs. TSH ≥ 1.0 µUI/mL: 115.7 ± 18.4 bpm p = 0.33). The groups also presented similar chronotropic index (TSH < 1.0 µUI/mL: 78.1 ± 30.6 vs. TSH ≥ 1.0 µUI/mL: 79.5 ± 26.4; p = 0.74).

CONCLUSION

In this sample studied, there were no difference between lower and upper TSH level concerning HR response during rest, peak of exercise and exercise recovery.

Right Ventricular Contractile Reserve Is Impaired in Children and Adolescents With Repaired Tetralogy of Fallot: An Exercise Strain Imaging Study

BACKGROUND

Pulmonary insufficiency (PI) and right ventricular (RV) dysfunction are long-term complications in patients with repaired tetralogy of Fallot (rTOF). The aim of this study was to investigate RV contractile reserve and changes in PI that occur during exercise in patients with rTOF and the associations of these changes with exercise performance using stress echocardiography.

METHODS

Subjects with rTOF (n = 32) and healthy control subjects (n = 10) were prospectively enrolled and underwent rest and peak exercise echocardiography during standard cardiopulmonary exercise test protocol on a cycle ergometer or treadmill. RV contractile reserve was defined as the change in RV global longitudinal strain from rest to peak exercise. PI was assessed with the diastolic-to-systolic time-velocity integral ratio and diastolic/systolic velocity ratio from pulmonary artery Doppler interrogation. Exercise measures included heart rate reserve, percentage predicted maximum oxygen consumption, percentage predicted maximum work, and oxygen pulse.

RESULTS

RV contractile reserve was impaired in patients with rTOF compared with control subjects, with a significant drop in the absolute value of RV global longitudinal strain from 17% (range, 8%-27%) at rest to 13% (range, 5%-28%) at peak exercise. Similarly, PI decreased at peak exercise, with decreases in diastolic-to-systolic time-velocity integral and diastolic/systolic velocity ratios. Reduction in PI was directly associated with percentage predicted maximum oxygen consumption, percentage predicted maximum work, and greater oxygen pulse. Heart rate reserve was directly associated with percentage predicted maximum oxygen consumption and percentage predicted maximum work. RV contractile reserve was not associated with any exercise parameters.

CONCLUSIONS

Patients with rTOF have an abnormal myocardial response to exercise with impaired RV contractile reserve compared with control subjects. Heart rate reserve and reduction in PI at peak exercise are associated with better exercise performance and appear to be significant contributors to exercise performance in rTOF. Measures to improve chronotropic health in rTOF should be explored.

Current challenges in managing comorbid heart failure and COPD

INTRODUCTION

Heart failure (HF) with reduced ejection fraction and chronic obstructive pulmonary disease (COPD) frequently coexist, particularly in the elderly. Given their rising prevalence and the contemporary trend to longer life expectancy, overlapping HF-COPD will become a major cause of morbidity and mortality in the next decade. Areas covered: Drawing on current clinical and physiological constructs, the consequences of negative cardiopulmonary interactions on the interpretation of pulmonary function and cardiopulmonary exercise tests in HF-COPD are discussed. Although those interactions may create challenges for the diagnosis and assessment of disease stability, they provide a valuable conceptual framework to rationalize HF-COPD treatment. The impact of COPD or HF on the pharmacological treatment of HF or COPD, respectively, is then comprehensively discussed. Authors finalize by outlining how the non-pharmacological treatment (i.e. rehabilitation and exercise reconditioning) can be tailored to the specific needs of patients with HF-COPD. Expert commentary: Randomized clinical trials testing the efficacy and safety of new medications for HF or COPD should include a sizeable fraction of patients with these coexistent pathologies. Multidisciplinary clinics involving cardiologists and respirologists trained in both diseases (with access to unified cardiorespiratory rehabilitation programs) are paramount to decrease the humanitarian and social burden of HF-COPD.

Clinical and prognostic impact of chronotropic incompetence in patients with hypertrophic cardiomyopathy

BACKGROUND

A blunted heart rate (HR) response is associated with an impaired peak oxygen uptake (pVO₂), a powerful outcome predictor in hypertrophic cardiomyopathy (HCM). The present multicenter study sought to determine the prognostic role for exercise-induced HR response in HCM.

METHODS

A total of 681 consecutive HCM outpatients on optimized treatment were recruited. The heart failure (HF) end-point was death due to HF, cardiac transplantation, NYHA III-IV class progression, HF worsening leading to hospitalization and severe functional deterioration leading to septal reduction. The sudden cardiac death (SCD) end-point included SCD, aborted SCD and appropriate implantable cardioverter defibrillator discharges.

RESULTS

During a median follow-up of 4.2 years (25-75th centile: 3.9-5.2), 81 patients reached the HF and 23 the SCD end-point. Covariates with independent effects on the HF end-point were left atrial diameter, left ventricular ejection fraction, maximal left ventricular outflow tract gradient and exercise cardiac power (ECP = pVO₂∗systolic blood pressure) (C-Index = 0.807) whereas the HCM Risk-SCD score and the ECP remained associated with the SCD end-point (C-Index = 0.674). When the VO₂-derived variables were not pursued, peak HR (pHR) re-entered in the multivariate HF model (C-Index = 0.777) and, marginally, in the SCD model (C-index = 0.656). A pHR = 70% of the maximum predicted resulted as the best cut-off value in predicting the HF-related events.

CONCLUSIONS

The cardiopulmonary exercise test is pivotal in the HCM management, however the pHR remains a meaningful alternative parameter. A pHR < 70% identified a HCM population at high risk of HF-related events, thus calling for a reappraisal of the chronotropic incompetence threshold in HCM.

Cardiopulmonary Exercise Test in Hypertrophic Cardiomyopathy

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

Cardiopulmonary Exercise Test as a Tool to Choose Therapy in Heart Failure

Heart failure treatment depends on several drugs, all providing improvement in outcome, but that cannot be realistically used all together in the same patient. It would be useful to have a tool that allows the arrangement of the most appropriate therapy cocktail for each patient. The aim of this article is to show the main differences in the effects of several drugs on cardiopulmonary function in patients with heart failure, both while resting and during exercise, and to discuss how these differences can be taken into account when choosing the most appropriate therapeutic protocol. In summary, angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers act synergistically to increase exercise capacity and peak oxygen uptake, but through different mechanisms: the former improving lung diffusion and exercise ventilatory efficiency, an action that is counteracted by concomitant aspirin therapy, and the latter probably by improving muscle perfusion. As for β-blockers, nonselective compounds, such as carvedilol, improve ventilation efficiency on the one hand, but interfere with lung diffusion on the other, and they are probably less tolerated under hypoxic conditions. On the contrary, β₁-selective compounds, such as bisoprolol or nebivolol, have a neutral effect on both lung diffusion and ventilation efficiency. These observations could be the basis for the choice of pharmacological therapy in patients with heart failure.

Application of exercise ECG stress test in the current high cost modern-era healthcare system

Exercise electrocardiogram (ECG) tests boasts of being more widely available, less resource intensive, lower cost and absence of radiation. In the presence of a normal baseline ECG, an exercise ECG test is able to generate a reliable and reproducible result almost comparable to Technitium–99 m sestamibi perfusion imaging. Exercise ECG changes when combined with other clinical parameters obtained during the test has the potential to allow effective redistribution of scarce resources by excluding low risk patients with significant accuracy. As we look towards a future of rising healthcare costs, increased prevalence of cardiovascular disease and the need for proper allocation of limited resources; exercise ECG test offers low cost, vital and reliable disease interpretation.

This article highlights the physiology of the exercise ECG test, patient selection, effective interpretation, describe previously reported scores and their clinical application in today’s clinical practice.

Impaired chronotropic response to physical activities in heart failure patients

Background

While exercise-based cardiac rehabilitation has a beneficial effect on heart failure hospitalization and mortality, it is limited by the presence of chronotropic incompetence (CI) in some patients. This study explored the feasibility of using wearable devices to assess impaired chronotropic response in heart failure patients.

Methods

Forty patients with heart failure (left ventricular ejection fraction, LVEF: 44.6 ± 5.8; age: 54.4 ± 11.7) received ECG Holter and accelerometer to monitor heart rate (HR) and physical activities during symptom-limited treadmill exercise testing, 6-min hall walk (6MHW), and 24-h daily living. CI was defined as maximal HR during peak exercise testing failing to reach 70% of age-predicted maximal HR (APMHR, 220 – age). The correlation between HR and physical activities in Holter-accelerometer recording was analyzed.

Results

Of 40 enrolled patients, 26 were able to perform treadmill exercise testing. Based on exercise test reports, 13 (50%) of 26 patients did not achieve at least 70% of APMHR (CI patients). CI patients achieved a lower % APMHR (62.0 ± 6.3%) than non-CI patients who achieved 72.0 ± 1.2% of APMHR (P < 0.0001). When Holter-accelerometer recording was used to assess chronotropic response, the percent APMHR achieved during 6MHW and physical activities was significantly lower in CI patients than in non-CI patients. CI patients had a significantly shorter 6MHW distance and less physical activity intensity than non-CI patients.

Conclusion

The study found impaired chronotropic response in 50% of heart failure patients who took treadmill exercise testing. The wearable Holter-accelerometer recording could help to identify impaired chronotropic response to physical activities in heart failure patients.

Trial registration

ClinicalTrials.gov ID NCT02358603. Registered 16 May 2014.

Chronotropic Incompetence and its Relation to Exercise Intolerance in Chronic Obstructive Pulmonary Disease

BACKGROUND

To study the relationship between chronotropic incompetence (CI) and disease severity and to assess the effect of CI on exercise capacity in patients with chronic obstructive pulmonary disease (COPD).

MATERIALS AND METHODS

Arterial blood gas analysis, pulmonary function test and cardiopulmonary exercise testing were conducted in 60 patients with stable COPD and 45 healthy volunteers. CI was defined using the chronotropic response index (CRI = (peak heart rate-resting heart rate) / (220-age-resting heart rate). Based on CRI, patients with COPD were divided into the normal chronotropic group (n = 23) and CI group (n = 37).

RESULTS

CI was present in 61.7% of the patients with COPD. Exercise capacity (peak oxygen uptake as percentage of predicted value, peak VO₂%pred), peak heart rate and CRI were significantly lower in patients with COPD than in controls. However, resting heart rate was significantly higher than in controls. FEV₁%pred and exercise capacity were significantly decreased in the CI group when compared with those in the normotropic group. There was significant association between CRI with FEV₁%pred and peak VO₂%pred. Multivariate regression analysis showed that CRI and FEV₁%pred were independent predictors of exercise capacity in patients with COPD. A cutoff of 0.74 for the CRI showed a specificity of 94.1% in predicting patients with a peak VO₂%pred < 60%.

CONCLUSIONS

CRI was associated with disease severity in patients with COPD. CI may be an important parameter to reflect exercise capacity in patients with COPD.

Clinical feasibility of a new method to identify chronotropic incompetence in heart failure patients

Heart failure patients have a high incidence of chronotropic incompetence (CI) that receives less clinical attention. This study assessed a method using wearable devices to identify CI in heart failure patients. Twenty-six heart failure patients (LVEF: 43.9  ±  5.7% with LVEF  ⩾40% in 19 patients; age: 52.8  ±  12.4 years, female patients  =  6) were enrolled. Each patient underwent symptom-limited treadmill maximal exercise testing during which the simultaneous recording of ECG Holter and physical activity using Actigraph was conducted. The APMHR ratio, the maximal heart rate during peak exercise over the age-predicted maximal heart rate (APMHR, 220-age), was determined. CI was diagnosed in patients who failed to reach at least 0.70 APMHR ratio. Holter-Actigraph recording was also applied during a 6 min hall walk (6MHW) and for 24 h to validate the method to assess impaired chronotropic response. Based on the reports of exercise testing in 26 patients, 13 patients (50%) failed to reach at least 0.70 APMHR ratio while the remaining 13 patients achieved  ⩾0.70 APMHR ratio. The APMHR ratio measured by Holter-Actigraph recording was significantly correlated with the APMHR ratio based on exercise test reports (R  =  0.99, P  <  0.001). The cut-off values of APMHR ratio (0.65) measured during 6MHW, APMHR ratio (0.69) measured during daily activities, and maximum Δ heart rate (37.8 bpm) measured during daily activities significantly predicted the results of exercise test reports with an area under the ROC curve of 0.7337, 0.7544 and 0.7870, respectively (all P values  <  0.05). This pilot study found that the wearable device can potentially help in the identification of chronotropic incompetence in heart failure patients.

Is there a heart rate paradox in acute heart failure?

BACKGROUND

Higher heart rate predicts higher mortality in chronic heart failure (HF). We studied the prognostic impact of admission heart rate in acute HF and analysed the importance of its change during hospitalization.

METHODS

Acute HF patients were studied. Endpoint was all-cause death. Patients were followed-up for 12 months from hospital admission. Cox-regression analysis was used to study the association of heart rate (both as a continuous and as a categorical variable) with mortality. Analysis was stratified according to admission rhythm and to systolic dysfunction. Multivariate models were built. Patients surviving hospitalization were additionally cross-classified attending to admission and discharge heart rates – cut-offs: 100 and 80 beats per minute (bpm), respectively.

RESULTS

We analysed 564 patients. Median age was 78 years and median admission heart rate 87 bpm. In a 12-month period 205 patients died, 23 in-hospital. Mortality increased steadily with heart rate decrease. Patients with heart rate ≥ 100 bpm had a multivariate-adjusted HR of 12-month death of 0.57 (95%CI: 0.39-0.81), and the HR was 0.92 (0.85-0.98) per 10 bpm increase in heart rate. Association of heart rate with mortality was stronger in patients in sinus rhythm (SR) and in those with systolic dysfunction. Eighty-seven patients had admission heart rate ≥ 100 and discharge heart rate < 80 bpm. In them, death rate was 14.9%; in the remaining patients it was 37.7%.

CONCLUSIONS

Higher admission heart rate predicted survival advantage in acute HF. Patients presenting with tachycardia and discharged with a controlled heart rate had better outcome than those admitted non-tachycardic or discharged with a non-controlled heart rate.

Characterization of exercise limitations by evaluating individual cardiac output patterns: a prospective cohort study in patients with chronic heart failure

BACKGROUND

Patients with chronic heart failure (CHF) suffer from exercise intolerance due to impaired central hemodynamics and subsequent alterations in peripheral skeletal muscle function and structure. The relative contribution of central versus peripheral factors in the reduced exercise capacity is still subject of debate. The main purpose was to investigate heterogeneity in the nature of exercise intolerance by evaluating individual cardiac output (Q) patterns. The secondary purpose was to evaluate whether patient and disease characteristics were associated with a central hemodynamic exercise limitation.

METHODS

Sixty-four stable CHF patients performed a symptom limited incremental exercise test with respiratory gas analysis and simultaneous assessment of Q, using a radial artery pulse contour analysis method. A central hemodynamic exercise limitation was defined as a plateau or decline in Q from 90 to 100 % of exercise duration.

RESULTS

Data from 61 patients were analyzed. A central hemodynamic exercise limitation was observed in 21 patients (34 %). In these patients, a higher occurrence of a plateau/decrease in oxygen uptake (VO2) (52 % vs 23 %, p = 0.02), stroke volume (SV) (100 % vs. 75 %, p = 0.01) and chronotropic incompetence (31 % vs. 2.5 %, p = 0.01) was observed, while presence of a left bundle branch block (LBBB) occurred significantly less (19 % vs 48 %, p = 0.03) There was no difference in disease characteristics such as etiology, duration, NYHA class, mitral regurgitation or ischemia.

CONCLUSIONS

The study revealed considerable heterogeneity in the nature of exercise limitations between moderately impaired CHF patients. In one third of the study population a plateau or decrease in Q towards peak exercise was demonstrated, which is indicative of a central hemodynamic exercise limitation. A central hemodynamic exercise limitation was associated with an impairment to augment stroke volume and heart rate.

Are 30 minutes of rest between two incremental shuttle walking tests enough for cardiovascular variables and perceived exertion to return to baseline values?

Objective:

To verify whether 30 minutes of rest between two incremental shuttle walking tests (ISWT) are enough for cardiovascular variables and perceived exertion to return to baseline values in healthy subjects in a broad age range.

Method:

The maximal exercise capacity of 334 apparently healthy subjects (age ≥18) was evaluated using the ISWT. The test was performed twice with 30 minutes of rest in between. Heart rate (HR), arterial blood pressure (ABP), dyspnea, and leg fatigue were evaluated before and after each test. Subjects were allocated to 6 groups according to their age: G1: 18-29 years; G2: 30-39 years; G3: 40-49 years; G4: 50-59 years; G5: 60-69 years and G6: ≥70 years.

Results:

All groups had a good performance in the ISWT (median >90% of the predicted distance). The initial HR (HRi) of the second ISWT was higher than the first ISWT in the total sample (p<0.0001), as well as in all groups (p<0.0001). No difference was observed in the behavior of ABP (systolic and diastolic) and dyspnea between the two tests, but this difference occurred for leg fatigue (greater before the second ISWT) in G1 (p<0.05). Most subjects (58%) performed better in the second test.

Conclusion:

30 minutes of rest between two ISWTs are not enough for all cardiovascular variables and perceived exertion to return to baseline values. However, this period appears to be sufficient for blood pressure and performance to recover in most subjects.

Relationship between chronotropic incompetence and β-blockers based on changes in chronotropic response during cardiopulmonary exercise testing

Background

Chronotropic incompetence (CI), an attenuated heart rate (HR) response to exercise, is common in patients with cardiovascular disease. The aim of this study was to assess changes in the chronotropic response (CR) during cardiopulmonary exercise testing (CPET) in patients undergoing cardiac rehabilitation and investigate the effects of β-blockers.

Methods

Patients undergoing cardiac rehabilitation performed CPET. Failure to achieve 80% of the age-predicted maximal HR (APMHR) defined CI. Values of the metabolic chronotropic relationship (MCR) were calculated from the ratio of the HR reserve to metabolic reserve at 4 stages, warm-up (MCR-Wu), anaerobic threshold (MCR-AT), respiratory compensation (MCR-Rc), and peak point (MCR-Pk), using the Wilkoff model. In patients who showed an increase in MCR at ≥ 3 of the 4 exercise stages, CR was considered to have improved.

Results

Patients with high BNP levels (≥ 80 pg/ml) had a lower MCR at all stages compared with those with low BNP levels (< 80 pg/ml). Of the 80 patients, 47 showed an increase in both peak VO₂ and AT, and of these 31 (66.0%) were taking β-blockers. Improvement in CR was observed in 30 of 47 patients with CI, and 70% of these were taking β-blockers. In patients not taking β-blockers, MCR-AT was lower than MCR-Rc, whereas in those taking β-blockers MCR-AT was higher than MCR-Rc.

Conclusions

An attenuated HR response may occur during the early stages of exercise. The HR response according to the presence or absence of β-blockers is clearly identifiable by comparing MCR-AT and MCR-Rc using the Wilkoff model.

•

We have standardized definitions of CI objectively based on the Wilkoff model.

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An attenuated HR response may occur during the early stages of exercise.

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MCR values without β-blockers decreased from warm-up to AT and increased after AT.

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MCR values with β-blockers decreased from warm-up to Rc and increased after Rc.

•

Cardiac rehabilitation increased peak VO₂ with an improvement in HR response.

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

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

Effect of β-blocker cessation on chronotropic incompetence and exercise tolerance in patients with advanced heart failure

BACKGROUND

Chronotropic incompetence is defined as the inability to reach 80% of heart rate (HR) reserve or 80% of the maximally predicted HR during exercise. The presence of chronotropic incompetence is associated with reduced peak oxygen consumption, and rate-responsive pacing therapy is under investigation to improve exercise capacity in heart failure (HF). However, uncertainty exists about whether chronotropic incompetence and reduced exercise tolerance in HF are attributable to β-blockade.

METHODS AND RESULTS

Subjects with HF and receiving long-term β-blocker therapy underwent cardiopulmonary exercise tolerance testing under 2 conditions in random sequence: (1) after a 27-hour washout period (Off-BB) and (2) 3 hours after β-blocker ingestion (On-BB). Norepinephrine levels were drawn at rest and at peak exercise. β1-response to norepinephrine was assessed using the chronotropic responsiveness index: ΔHR/Δlog norepinephrine. Nineteen patients with systolic HF (left ventricular ejection fraction, 22.8±7.7%) were enrolled. Mean age was 49.4±12.3 years. Average carvedilol equivalent dose was 29.1±17.0 mg daily. Peak HR off/on β-blockers was 62.7±18.7% and 51.4±18.2% HR reserve (P<0.01) and 79.1±11.0% and 70.3±12.3% maximally predicted HR (P<0.01). For the Off-BB and On-BB conditions, the respiratory exchange ratios were 1.05±0.06 and 1.05±0.10 (P=0.77), respectively, confirming maximal and near identical effort in both conditions. The peak oxygen consumption was 16.6±3.34 and 15.9±3.31 mL/kg/min (P=0.03), and the chronotropic responsiveness index was 19.3±7.2 and 16.2±7.1 (P=0.18).

CONCLUSIONS

Acute β-blocker cessation does not normalize the chronotropic response to exercise in patients with advanced HF and chronotropic incompetence.

Capacidade funcional de indivíduos com insuficiência cardíaca avaliada pelo teste de esforço cardiopulmonar e classificação da New York Heart Association

O objetivo deste estudo foi avaliar a capacidade discriminativa da classificação da New York Heart Association (NYHA) em indivíduos com insuficiência cardíaca (IC) classes II e III por meio de variáveis do teste de esforço cardiopulmonar (TECP). Participaram do estudo 17 pessoas com IC classe II (44,47±10,11 anos; fração de ejeção ventricular 32,11±10,37%) e 15 classe III (46,73±8,74 anos; fração de ejeção ventricular 30,46±10,23%) da NYHA que realizaram TECP máximo em esteira ergométrica. De acordo com a distribuição dos dados, houve correlação de Pearson ou Spearman e, para comparação entre classes, utilizou-se o teste t de Student. Foram encontradas correlações significativas (p<0,05) entre consumo de oxigênio (VO2) e pulso de oxigênio (r=0,76), idade (r=0,35) e índice de massa corpórea (r=0,45). Não houve correlação significativa entre fração de ejeção ventricular e as demais variáveis estudadas. Comparando as classes da NYHA, foram encontradas diferenças para VO2 e pulso de oxigênio (p<0,05). Nesta pesquisa, as correlações refletem a complexidade de se analisar e entender o processo de disfunção da IC, considerando que provavelmente há outros fatores influenciando cada uma das variáveis estudadas. A classificação da NYHA foi efetiva na diferenciação dos indivíduos nos diferentes grupos, reforçando sua utilidade na caracterização de grupos de indivíduos com IC para fins de pesquisas científicas, assim como para avaliação de terapêuticas.

Chronotropic incompetence and abnormal heart rate recovery early after left ventricular assist device implantation

BACKGROUND

Chronotropic response to exercise and heart rate recovery immediately after exercise (HRR(1) ) are valid prognostic markers in patients with chronic heart failure (CHF). The aim of this study was to evaluate heart rate profile during and after exercise in CHF patients early after left ventricular assist device (LVAD) implantation.

METHODS

We enrolled seven stable consecutive CHF patients (five males, mean age: 45 ± 16 years) after 1 month of LVAD (HeartMate II; Thoratec Corp, Pleasanton, CA, USA) implantation, seven healthy subjects, and 14 patients with advanced HF (HF control group) who performed an incremental symptom-limited cardiopulmonary exercise testing (CPET). CHF patients performed CPET at 1 and 3 months after LVAD. HRR(1) was defined as the HR difference from peak to 1 minute after exercise and chronotropic response to exercise as the chronotropic reserve ([CR, %]=[peak HR-resting HR/220-age-resting HR]× 100).

RESULTS

LVAD patients 3 months after implantation had a significantly different HR profile during exercise compared to healthy controls, with significantly lower CR (57 ± 31 vs 90 ± 14, %, P < 0.001) and HRR(1) (14 ± 6 vs 28 ± 8, bpm, P < 0.01). HR profile during exercise did not significantly change 1 and 3 months after LVAD implantation. There was no statistical difference compared to HF control group and LVAD group regarding cardiopulmonary parameters.

CONCLUSIONS

LVAD patients present an impaired CR and an abnormal HRR(1) after implantation, indicating significant cardiac autonomic abnormalities. These alterations seem to remain unaltered 3 months after LVAD implantation.