Exercise stress testing: A valuable tool to predict risk and prognosis

Hybrid PET/MR in Cardiac Imaging

In the last few years, technological advances in MR imaging, PET detectors, and attenuation correction algorithms have allowed the creation of truly integrated PET/MR imaging systems, for both clinical and research applications. These machines allow a comprehensive investigation of cardiovascular diseases, by offering a wide variety of detailed anatomical and functional data in combination. Despite significant pathophysiologic mechanisms being clarified by this new data, its clinical relevance and prognostic significance have not been demonstrated yet.

Cardiopulmonary Exercise Testing in Pediatric Patients With Hypertrophic Cardiomyopathy

Background

Exercise stress testing (EST) in pediatric hypertrophic cardiomyopathy (HCM) patients has not well described in a large heterogenous cohort.

Objectives

The objective of the study was to determine the clinical utility of EST in pediatric HCM.

Methods

This was a retrospective single-center analysis of HCM patients younger than 21 years who had EST between January 1, 2000, and January 1, 2019. Clinical, demographic characteristics, and EST data were analyzed, using the last EST during the study or prior to the event in subjects with a primary outcome. The primary composite endpoint included cardiac death, transplant, or arrhythmia requiring implantable cardioverter-defibrillator placement. Outcome analysis was performed using Cox proportional hazard modeling.

Results

The study cohort included 140 patients, 52% with a recognized genetic variant. There were 2 tests aborted due to safety concerns (ST-segment changes, ventricular ectopy). The median age at first EST was 13.6 years. Ninety percent of patients were tested using cycle ergometry, and 44% were on a beta-blocker. The median peak oxygen consumption was 37.1 mL/kg/min (IQR: 12.5 mL/kg/min) or 81.2% predicted, the mean anaerobic threshold was 21.8 Ml (IQR: 8.3 mL), and the median peak power was 2.6 ± 1.1 W/kg or 73.7% predicted. Ectopy during EST was seen in 44% of patients, and 8% had an abnormal blood pressure response to exercise. The endpoint was reached in 12 patients. The presence of any degree of ectopy was a predictor of the composite endpoint (hazard ratio: 5.8; 95% CI: 1.3-26.7).

Conclusions

EST is clinically useful in select pediatric patients with HCM. Ectopy on EST is a risk factor for cardiac death, cardiac transplant, and arrhythmias requiring implantable cardioverter-defibrillator.

Normative Values for Cardiopulmonary Exercise Stress Testing Using Ramp Cycle Ergometry in Children and Adolescents

OBJECTIVES

To provide sex, age, and race specific reference values for ramp cycle ergometer cardiopulmonary exercise test (CPET) in children in the US.

STUDY DESIGN

Retrospective review was conducted of all cardiopulmonary CPET data from our Exercise Physiology Laboratory on healthy children and adolescents (6-18 years) with body mass index between the 5th and 95th percentiles and structurally normal hearts who performed a ramp cycle ergometry stress test between 1999 and 2015. Twenty-eight exercise variables were included: peak oxygen consumption, oxygen consumption at ventilatory anaerobic threshold, peak work rate, resting and peak heart rate and blood pressure, resting pulmonary function testing, and ventilatory responses to progressive exercise using breath-by-breath gas exchange. Owing to the nonlinear association between CPET results and age, fractional polynomials were used in the mixed-effects regression models to describe the sex- and age-specific normative values with 95% CIs, after adjusting for race and body mass index.

RESULTS

We analyzed data on 1829 children (average age, 13.6 ± 2.6 years; 52% male). After 12 years of age, males generally had higher peak values for aerobic capacity and work rate. There were progressive increases with age for both sexes in resting pulmonary function and ventilatory response to exercise, peak aerobic and work rate, and oxygen pulse. Notably, there was an age-related decrease in ventilatory equivalents of oxygen and carbon dioxide at the ventilatory anaerobic threshold.

CONCLUSIONS

Future research using prospective, inclusive, and statistically planned cohorts with standardized laboratory approaches and confirmed interoperability should be considered as a focus for validating normative pediatric CPET values in the future.

Cardiopulmonary Rehabilitation in Pediatric Patients With Congenital and Acquired Heart Disease

BACKGROUND

Heart disease in children and adolescents is common, approaching 1.0% of the population. In those patients with complex physiology and severe cardiac dysfunction, the inability to participate in physical activity results in significant obstacles to normal acts of daily living and significantly diminished quality of life. Attempts to study the practicality and benefits of cardiopulmonary rehabilitation (CR) programs in this population have been hampered by the heterogeneity of lesions, lack of facilities, and trained personnel to supervise these types of programs. Although there are numerous articles on CR in children with cardiac disease, all suffer from the same basic problems of small sample size, short duration of study, and heterogeneous study populations.

PURPOSE

The purpose of this review was to first evaluate the current rehabilitation literature on both congenital cardiac defects and acquired abnormalities-in this latter group placing a significant emphasis on cardiomyopathies, as well as the special populations in the peri-transplant period and/or mechanical circulatory support. Second, we discussed what is known about practical approaches to CR for the various types of pediatric-specific cardiac conditions. This limited data will be supplemented by the current approach of our institution to CR in these populations with the understanding that this is by no means a consensus approach to these patients. Finally, we summarized research goals for this growing group of patients.

CONCLUSION

Cardiopulmonary rehabilitation in pediatric congenital and acquired heart disease is currently a field in its infancy. Significant strides have been made for complex heart disease and impaired myocardial function. Current research holds the promise for the development of programs that are practical, scalable, and can be implemented in most clinical sites within the foreseeable future.