Cardiac Rehabilitation Improves Cardiometabolic Health in Young Patients with Nonischemic Dilated Cardiomyopathy

Patients and Methods

This retrospective study was approved by our institutional review board. We searched the database of the Cardiac Rehabilitation Program at Cincinnati Children's Hospital Medical Center for patients with nonischemic DCM who were referred between 2011 and 2015. The diagnosis was independently confirmed by 2 cardiologists. For each patient, we recorded baseline characteristics, including demographic information, body mass index (BMI), waist circumference, medications, American Heart Association (AHA) HF class, quality of life (QOL) score (as measured by the Pediatric Quality of Life Inventory [PedsQL] scoring tool),⁴ echocardiographic left ventricular ejection fraction (LVEF), serum brain natriuretic peptide (BNP) level, cardiopulmonary exercise test (CPET) results, and 6-minute walk distance test (6MWD).

Eight patients whose primary cardiologists had prescribed CR for the indication of HF with reduced LVEF were included in the study (Table I). Their mean age was 20.6 ± 6.6 years (range, 10–31 yr), and 4 were male. The group was predominately obese (mean BMI, 38.2 ± 12.5 kg/m²; mean waist circumference, 46.8 ± 7.7 in). Six patients had idiopathic DCM, one had anthracycline-induced cardiomyopathy, and one had peripartum cardiomyopathy. According to the AHA's objectives for assessment of HF, 5 patients were in class C, and 3, in class D. The mean baseline LVEF was 0.26 ± 0.15, and the mean baseline indexed maximum oxygen consumption was 17 ± 5 mL/kg/min (data not shown). All patients had been prescribed maximal medical therapy at the time of CR. Two patients participated in CR as inpatients, and 2 were on LVAD support.

TABLE I. Patients' Baseline Demographic and Clinical Characteristics

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The CR sessions consisted of supervised, personalized exercise therapy, administered in the hospital by a single exercise physiologist according to the standards of the American Association of Cardiovascular and Pulmonary Rehabilitation. Each session lasted at least 45 minutes and included active warm-up, cardiovascular exercise, strength, flexibility, and cooldown components. The patient's heart rate reserve (HRR) was calculated from baseline CPET values, and 75% to 85% of HRR was maintained for at least half of each session. Patients were encouraged to attend 2 sessions per week for up to 16 weeks.

Immediately after completion of CR, endpoints were reevaluated. The echocardiograms nearest to the start and end of CR were compared. Safety was evaluated by counting adverse events during CR sessions. All-cause and cardiovascular-related hospitalizations during a 12-month follow-up period were totaled.

Statistical analysis was conducted by using JMP^® Pro 12 software (SAS Institute Inc.). Continuous demographic and clinical variables were summarized as mean ± SD. Baseline and post-CR measurements of waist circumference and 6MWD were compared with use of a 2-tailed paired-sample t test. Statistical significance could not be evaluated because of the small number of patients.

Results

The patients attended 120 of 141 (85%) possible CR sessions. There were no deaths, adverse events necessitating discontinuation of CR sessions, or cardiovascular-related hospitalizations during patients' participation. In patients who had post-CR endpoints recorded (n=5), mean waist circumference decreased by 1.37 ± 0.6 in (95% CI, −2.1 to −0.63) (Fig. 1); there was no significant change in BMI. The 6MWD increased by a mean of 111 ± 75 m (n=5; 95% CI, 18–205) (Fig. 2). The mean serum BNP level decreased, and the QOL score improved in all patients in whom it was measured (Table II). There was no marked change in left ventricular systolic function after CR (mean LVEF, 0.28 ± 0.17).

TABLE II. Clinical Endpoints Immediately after Cardiac Rehabilitation and at One Year

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Within one year of starting CR, one patient with an LVAD underwent heart transplantation, and the other remained stable at home. One patient was hospitalized twice for HF exacerbations that necessitated medication adjustment, and another patient was hospitalized for stroke, possibly due to embolism of an undiagnosed left ventricular thrombus.

Discussion

Diminished functional capacity, which is predictive of adverse cardiovascular outcomes such as death and the need for a heart transplant, can be worsened by obesity, a condition common in patients with HF.^2,3 Many children with HF also have a poor QOL, which is associated with depression and anxiety.⁴ Reducing obesity and improving QOL in young patients with HF and nonischemic DCM may help prevent decompensation or, at least, put patients with advanced HF in a better psychological state before heart transplantation or the implantation of a ventricular assist device. In our young patient population, functional capacity and QOL improved after exercise therapy, and this finding is consistent with that in O'Connor and colleagues' study of exercise training in adults with HF.⁵ We also observed an intriguing decrease in serum BNP levels in our patients; this may indicate that optimal management of HF leads to lower ventricular wall stress.

Limitations of this study include the small number of patients, which indicates the novelty of treating young HF patients with CR. Moreover, we did not control for medications, which may have had a confounding effect on our results. Although some patients participated in CR as inpatients and others as outpatients, only one exercise physiologist administered the sessions, which meant little or no variability in technique. Finally, because most patients did not have a post-therapy CPET available, our ability to state the effect of CR on functional capacity is limited; however, the magnitude of the increase in their 6MWD offers compelling evidence that CR was beneficial.

Conclusion

Young patients with nonischemic DCM, including those with advanced HF that necessitates an LVAD, may be able to participate in supervised exercise therapy with minimal risk. In our patients with HF, we observed a reduction in central adiposity, improved 6MWD, a decrease in serum BNP, and improved patient-reported QOL after exercise therapy—results that are similar to those in older adults with HF. A more robust, prospective study of the safety and effects of CR in young patients with nonischemic DCM is needed to confirm these findings and to examine clinical outcomes in more depth.