Relationships among exercise capacity, hypertrophy, and left ventricular diastolic function in nonobstructive hypertrophic cardiomyopathy

Shifting paradigms in hypertrophic cardiomyopathy: the role of exercise in disease management

Hypertrophic cardiomyopathy (HCM) is traditionally associated with exercise restriction due to potential risks, yet recent evidence and guidelines suggest a more permissive stance for low-risk individuals. The aim of this comprehensive review was to examine existing research on the impact of exercise on cardiovascular outcomes, safety, and quality of life in this population and to consider implications for clinical practice. Recent studies suggest that regular exercise and physical activity in low-risk individuals with HCM are associated with positive outcomes in functional capacity, haemodynamic response, and quality of life, with consistent safety. Various studies highlight the safety of moderate-intensity exercise, showing improvements in exercise capacity without adverse cardiac remodelling or significant arrhythmias. Psychological benefits, including reductions in anxiety and depression, have been also reported following structured exercise programmes. These findings support the potential benefits of integrating individualised exercise regimens in the management of low-risk individuals with HCM, with the aim of improving their overall well-being and cardiovascular health. Adoption of the FITT (frequency, intensity, time, and type of exercise) principle, consideration of individual risk profiles, and shared decision-making are recommended. Future research is warranted to clarify the definition of 'low risk' for exercise participation and investigate the influence of physical activity on disease progression in HCM. Innovation in therapeutic strategies and lifestyle interventions, alongside improved patient and provider education, will help advance the care and safety of individuals with HCM engaging in exercise.

Efficacy and Safety of Hybrid Cardiac Telerehabilitation in Patients with Hypertrophic Cardiomyopathy without Left Ventricular Outflow Tract Obstruction and Preserved Ejection Fraction—A Study Design

Hypertrophic cardiomyopathy (HCM) is the most common congenital disease increasing the risk of sudden cardiac death. For many years, HCM patients were excluded from exercise training. However, there are data showing that patients with HCM undergoing supervised exercise training could improve physical performance without serious adverse events. A project was designed as a randomized clinical trial to assess the effectiveness and safety of hybrid cardiac rehabilitation (HCR)—a combination of hospital-based cardiac rehabilitation (1 month) with a new form of home-based telemonitored cardiac rehabilitation (2 months) in HCM patients without left ventricular (LV) outflow tract obstruction and preserved systolic function. Sixty patients who fulfil the inclusion criteria have been randomly assigned (1:1) to either HCR plus usual care (training group) or usual care only (control group). The primary endpoint is a functional capacity evaluated by peak oxygen uptake (pVO2). Secondary endpoints include workload time during the cardiopulmonary exercise testing, a six-minute walk test distance, NT-pro BNP level, echocardiographic parameters of the left ventricular diastolic function (E/A, E/e’, myocardial strain rate), right ventricular systolic pressure, a gradient in the LV outflow tract, and quality of life. The tertiary analysis includes safety, acceptance and adherence to the HCR program. Our research will provide innovative data on the effectiveness and safety of hybrid cardiac rehabilitation in HCM patients without LV outflow tract obstruction and preserved systolic function. Clinical trials registry: ClinicalTrials.gov Identifier NCT03178357.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Predictors of Exercise Capacity in Patients with Hypertrophic Obstructive Cardiomyopathy

Hypertrophic obstructive cardiomyopathy (HOCM) patients exhibit compromised peak exercise capacity (VO₂peak). Importantly, severely reduced VO₂peak is directly related to increased morbidity and mortality in these patients. Therefore, we sought to determine clinical predictors of VO₂peak in HOCM patients. HOCM patients who performed symptom-limited cardiopulmonary exercise testing between 1995 and 2016 were included for analysis. Peak VO₂ was reported as absolute peak VO₂, indexed to body weight and analyzed as quartiles, with quartile 1 representing the lowest VO₂peak. Step-wise regression models using demographic features and clinical and physiologic characteristics were created to determine predictors of HOCM patients with the lowest VO₂peak. We included 1177 HOCM patients (age: 53 ± 14 years; BMI: 24 ± 12 kg/m²) with a VO₂peak of 18.0 ± 5.6 mL/kg/min. Significant univariate predictors of the lowest VO₂peak included age, female sex, New York Health Association (NYHA) class, BMI, left atrial volume index, E/e’, E/A, hemoglobin, N-terminal pro b-type natriuretic peptide (NT-proBNP), and a history of diabetes, hypertension, stroke, atrial fibrillation, or coronary artery disease. Independent predictors of the lowest VO₂peak included age (OR, CI: 1.03, 1.02–1.06; p < 0.0001), women (4.66, 2.94–7.47; p = 0.001), a history of diabetes (2.05, 1.17–3.60; p = 0.01), BMI (0.94, 0.92–0.96; p < 0.0001), left atrial volume index (1.07, 1.05–1.21; p = 0.04), E/e’ (1.05, 1.01–1.08; p = 0.004), hemoglobin (0.76, 0.65–0.88; p = 0.0004), and NT-proBNP (1.72, 1.42–2.11; p < 0.0001). These findings demonstrate that demographic factors (i.e., age and sex), comorbidities (e.g., diabetes and obesity), echocardiography indices, and biomarkers (e.g., hemoglobin and NT-proBNP) are predictive of severely compromised VO₂peak in HOCM patients.

Modeling Cardiac Hemodynamic Response During Exercise in Health and Hypertrophic Cardiomyopathy

INTRODUCTION

Hypertrophic cardiomyopathy (HCM) is associated with altered hemodynamics in the left ventricular outflow tract and tissue abnormalities. Exercise testing has become an integral and powerful tool for the noninvasive evaluation of HCM and, in some patients, it could define a treatment strategy. Obiective: To model the hemodynamic alterations during exercise in healthy and HCM patients, obtained by noninvasive methods.

METHODS

Cardiac output (CO), heart rate (HR), arterial blood pressure (ABP) and Total Peripheral Resistance (TPR) were assessed during exercise. The evaluation included a curve-fitting approach (sigmoidal model) that allowed a quantitative comparison of CO profiles.

RESULTS

When compared to controls, patients with HCM showed reduced peak exercise cardiac output and demonstrated high peripheral resistance during exercise. Analysis of modeled it CO curves revealed a higher maximum rate of recovery in healthy individuals than in HCM patients.

CONCLUSION

The application of the sigmoidal model showed to be efficient in the characterization of CO dynamics for the different studied groups.

Efficacy of exercise training in symptomatic patients with hypertrophic cardiomyopathy: results of a structured exercise training program in a cardiac rehabilitation center

BACKGROUND

Recent data suggest that exercise training (ET) confers significant symptomatic and functional improvements in patients with diastolic dysfunction, and thus may be beneficial in patients with hypertrophic cardiomyopathy (HCM). However, there are no data regarding the safety or efficacy of ET in HCM patients.

DESIGN

A prospective non-randomized intervention design was used.

METHODS

We enrolled 20 patients with symptomatic HCM, significantly limited in everyday activity, into a supervised cardiac rehabilitation exercise program.

RESULTS

Patients were 62 ± 13 years old, in New York Heart Association (NYHA) functional class II (35%) or III (65%), had a mean interventricular septum dimension of 17 ± 5 mm and left ventricular ejection fraction (LVEF) of 53 ± 15%. Left ventricular outflow gradient was present at rest in nine patients (mean 51 ± 24 mm Hg) and six patients had an implantable defibrillator. Exercise prescription was based on heart rate reserve (HRR) determined from a symptom-limited graded exercise stress test. Exercise intensity was gradually increased from 50% to 85% of the HRR over the training period. Patients completed an average of 41 ± 8 hours of aerobic ET. No adverse events or sustained ventricular arrhythmias occurred during the training program. Functional capacity, assessed by a graded exercise test, improved from 4.7 ± 2.2 to 7.2 ± 2.8 metabolic equivalents (METs) (p = 0.01). NYHA functional class improved from baseline by ≥ 1 grade in 10 patients (50%) and none experiencing deterioration during follow-up.

CONCLUSIONS

The present study suggests that patients with HCM who remain symptomatic despite medical therapy may achieve considerable functional improvement through a supervised ET program.

Exercise eco-Doppler in hypertrophic cardiomyopathy patients. Determinant factors of exercise intolerance

INTRODUCTION AND OBJECTIVES

At-rest echocardiography is a poor predictor of exercise capacity in patients with hypertrophic cardiomyopathy. We aimed to test the performance of treadmill exercise Doppler echocardiography in the prediction of functional limitations in these patients.

METHODS

Eighty-seven consecutive patients with hypertrophic cardiomyopathy underwent treadmill exercise echocardiography with direct measurement of oxygen consumption. Both at rest and at peak exercise, the mitral inflow, mitral regurgitation, left ventricular outflow tract obstruction and mitral annulus velocities were assessed.

RESULTS

Forty-three patients developed left ventricular outflow tract obstruction during exercise, which significantly decreased oxygen consumption (21.3 [5.7] mL/kg/min vs 24.6 [6.1] mL/kg/min; P=.012), and had greater left atrial volume (42.1 [14.5] mL/m(2) vs 31.1 [11.6] mL/m(2); P<.001) and a higher degree of mitral regurgitation and E/E' ratio during exercise. Exercise variables improved the predictive value of functional capacity (adjusted R(2) rose from 0.38 to 0.49). Independent predictors of oxygen consumption were age, left atrial volume, E/E' ratio and the presence of left ventricular outflow tract obstruction. In a subset of patients without left ventricular outflow obstruction, only left ventricular and atrial volume indexes were independent predictors of exercise capacity.

CONCLUSIONS

In patients with hypertrophic cardiomyopathy, left ventricular outflow tract obstruction and left atrial volume are the main predictors of exercise capacity. Exercise echocardiography is a better predictor of functional performance than at-rest echocardiography, although its predictive power is under 50%. In nonobstructed patients, left atrial and ventricular volumes were the independent factors.

Incremental Value of Left Ventricular Diastolic Function Reserve Index for Predicting Exercise Capacity in Patients with Hypertrophic Cardiomyopathy

The changes of left ventricular diastolic function during exercise are heterogeneous in patients with hypertrophic cardiomyopathy (HCM). We sought to investigate whether exertional changes of mitral annular velocities and plasma N-terminal-pro-B-type natriuretic peptide (BNP) concentration are associated with exercise capacity in patients with HCM. After a comprehensive echocardiographic study, 32 patients with HCM performed symptom-limited graded supine bicycle exercise. Echocardiographic Doppler parameters were measured at each stage of exercise. Blood samples were collected at rest and immediately after exercise to determine the concentration of pro-BNP. Resting pro-BNP (r = -0.620, P < .001), E'(base) (r = 0.414, P = .018), and DeltaE'(50W) (change of E' from base to 50 W of exercise) (r = 0.367, P = .039) were significantly correlated with exercise duration. Left ventricular longitudinal diastolic function reserve index, defined as DeltaE' x E'(base), significantly correlated with exercise duration (at 50 W, r = 0.540, P = .001) independent of age, sex, body mass index, and resting pro-BNP level. When combining DeltaE' x E'(50W) (<5.85 cm(2)/s(2)) and resting pro-BNP (>740 mg/dL), the predictive accuracy for exercise capacity could be improved (for <500 seconds, global chi(2) = 5.84 in pro-BNP vs 8.10 in pro-BNP + DeltaE' x E'(50W), P = .023). The assessment of left ventricular longitudinal diastolic function reserve can provide incremental information to pro-BNP for the prediction of exercise capacity in patients with HCM.

Clinical significance of tissue Doppler imaging in patients with hypertrophic cardiomyopathy

BACKGROUND

A transmitral E/septal Ea ratio > or =15 is a predictor of adverse outcome in cardiac disease, so it was hypothesized that a septal E/Ea >/=15 would predict the risk of adverse outcome, including sustained ventricular tachycardia (VT), cardiac arrest, implantable cardioverter defibrillator (ICD) discharge, or sudden death (SD) in patients with hypertrophic cardiomyopathy (HCM).

METHODS AND RESULTS

The study group comprised 96 consecutive patients with HCM (median age 53 years) who completed all noninvasive tests for risk stratification. The endpoint of the study was defined as death, cardiac arrest, documented sustained VT, or ICD-discharge. The median follow-up was 20.6 months. All patients were alive at the end of follow-up, although 8 patients had reached the endpoint during the study period. The variables that were predictive of adverse clinical outcome were family history of premature SD (p=0.03), syncope (p<0.001), maximum wall thickness > or =3 cm (p=0.02), and septal E/Ea > or =15 (p<0.001). In a stepwise multivariable model the only independent prognostic indicator was a septal E/Ea > or =15 (relative risk 0.26, 95% confidence interval 0.2-0.58, p<0.001). The cumulative event-free survival rate was 78.9% in patients with septal E/Ea > or =15, and 100% in patients with septal E/Ea <15 (p=0.0003).

CONCLUSIONS

Septal E/Ea > or =15 predicts patients with HCM who are at risk of sustained VT, cardiac arrest, ICD-discharge, or SD. (Circ J 2007; 71: 897 - 903).

Relation of left ventricular chamber stiffness at rest to exercise capacity in hypertrophic cardiomyopathy

The degree of exercise capacity is poorly predicted by conventional markers of disease severity in patients with hypertrophic cardiomyopathy (HC). The principal mechanism of exercise intolerance in patients with HC is the failure of stroke volume augmentation due to left ventricular (LV) diastolic dysfunction. The role of LV chamber stiffness, assessed noninvasively, as a determinant of exercise tolerance is unknown. Sixty-four patients with HC were studied with Doppler echocardiography, exercise testing, and gadolinium cardiac magnetic resonance. The LV chamber stiffness index was determined as the ratio of pulmonary capillary wedge pressure (derived from the E/Ea ratio) to LV end-diastolic volume (assessed by cardiac magnetic resonance). Maximal exercise tolerance was defined as achieved METs. There were inverse correlations between METs achieved and age (r = -0.38, p = 0.003), heart rate deficit (r = -0.39, p = 0.002), LV outflow tract gradient (r = -0.33, p = 0.009), the E/Ea ratio (r = -0.4, p = 0.001), mean LV wall thickness (r = -0.26, p = 0.04), and LV stiffness (r = -0.56, p <0.001) and a positive correlation between METs achieved and LV end-diastolic volume (r = 0.33, p = 0.01). On multivariate analysis, only LV chamber stiffness was associated with exercise capacity. A LV stiffness level of 0.18 mm Hg/ml had 100% sensitivity and 75% specificity (area under the curve 0.84) for predicting < or =7 METs achieved. In conclusion, LV diastolic dysfunction at rest, as manifested by increased LV chamber stiffness, is a major determinant of maximal exercise capacity in patients with HC.

Wave intensity analysis of left atrial mechanics and energetics in anesthetized dogs

The left atrium (LA) acts as a booster pump during late diastole, generating the Doppler transmitral A wave and contributing incrementally to left ventricular (LV) filling. However, after volume loading and in certain disease states, LA contraction fills the LV less effectively, and retrograde flow (i.e., the Doppler Ar wave) into the pulmonary veins increases. The purpose of this study was to provide an energetic analysis of LA contraction to clarify the mechanisms responsible for changes in forward and backward flow. Wave intensity analysis was performed at the mitral valve and a pulmonary vein orifice. As operative LV stiffness increased with progressive volume loading, the reflection coefficient (i.e., energy of reflected wave/energy of incident wave) also increased. This reflected wave decelerated the forward movement of blood through the mitral valve and was transmitted through the LA, accelerating retrograde blood flow in the pulmonary veins. Although total LA work increased with volume loading, the forward hydraulic work decreased and backward hydraulic work increased. Thus wave reflection due to increased LV stiffness accounts for the decrease in the A wave and the increase in the Ar wave measured by Doppler.