Cardiac rehabilitation in patients with peripheral arterial disease after revascularization

Abstract

Objectives

To evaluate safety, feasibility, and benefit of cardiac rehabilitation (CR) in patients with peripheral arterial disease (PAD) who undergo revascularization.

Methods

We conducted a prospective, non-randomized, pilot study to assess the feasibility, safety, and benefit of CR in PAD patients after revascularization compared to standard of care (controls). CR feasibility was assessed by the ability to complete 36 sessions. Safety was defined as the absence of adverse cardiovascular events during CR. Quality of life (QoL) assessment was performed using SF-36 form (Medical Outcomes Study 36-Item Short-Form Health Survey) and PAD-specific quality of life questionnaire (VascuQOL6). Other endpoints included incidence of claudication during 6-minute walk test (6MWT), mean distance, and number of laps walked. All outcome data were collected before and after CR completion. Standard statistical tests were used for comparisons.

Results

This study enrolled 20 subjects (CR group = 10). Mean age was 60.70 (±7.13) and 63.1 (±9.17) years in CR and controls, respectively (p-value > 0.05). Fifty percent and 60% were female in CR and control group, respectively. All subjects completed 36 CR sessions without adverse events. The increase in mean distance walked during 6MWT was higher in the CR group compared to control group (63.7 m vs. 10.5 m, p = 0.043). Change in mean number of laps walked was higher in the CR group (3.5 vs. –1.1; p < 0.01). Scores on 6 of 8 scales of SF-36 and VascuQOL6 were higher in the CR group, though not statistically significant.

Conclusion

CR is safe, feasible, and improves walking ability in ambulatory patients with PAD after arterial revascularization.

Keywords

Cardiac rehabilitation peripheral arterial disease revascularization

Introduction

Peripheral arterial disease (PAD) is a chronic, disabling atherosclerotic disease that affects more than 8.5 million people in the United States and accounts for annual costs of more than $21 billion.^1,2 Patients with PAD have very similar risk profiles and comorbidities as patients with coronary artery disease (CAD). In fact, studies have shown that these patients are at an even higher risk of cardiovascular mortality compared to patients with CAD.³ However, when compared to CAD patients, PAD patients are often undertreated in terms of risk factor and lifestyle modification.⁴

Cardiac rehabilitation (CR) is an effective secondary prevention therapy in patients with CAD who have undergone revascularization procedures (percutaneous or surgical).⁵ It has been shown to improve mortality and reduce future cardiovascular events in these patients.⁶ CR has been approved by Centers for Medicare & Medicaid Services (CMS) and most of third-party payers for patients undergoing coronary revascularization and is an important performance metric to assess health systems in this population in the USA. Even though CMS has approved supervised exercise therapy in PAD patients with claudication, these patients are not routinely enrolled in such programs. Furthermore, those who have undergone revascularization for PAD have been generally excluded from these discussions. These patients (similar to coronary revascularization patients) remain at high risk for future cardiovascular events. However, therapeutic benefit and feasibility of enrolling these patients in CR have not been well studied. This is important as these patients may have unique limitations due to debility that may prevent them from participating in CR programs.

We hypothesized that PAD patients will derive benefit from CR similarly to their CAD counterparts. To assess this, we conducted a pilot study to evaluate the primary outcomes of safety and feasibility of a CR program in PAD patients after treatment with arterial revascularization. Secondary aims were to assess functional capacity and change in quality of life (QoL) metrics from CR when compared to standard of care.

Methods

This is a prospective, non-randomized, pilot study conducted at a large tertiary care academic medical center in the United States. Adult patients with lifestyle limiting claudication and/or critical limb ischemia presentation who underwent surgical or endovascular revascularization in the prior 3 months were eligible for enrollment. Patients who could not ambulate without human assistance were excluded. Those awaiting further revascularization procedures were also excluded. All patients meeting the eligibility criterion were invited to voluntarily participate in the study. For practical purposes, patients with logistical issues to come to CR center (transportation issues, residing too far from the CR center) were assigned to the standard of care group. Those without these issues were assigned to the CR group. The study was approved by Institutional Review Board (study number HSC140692) at University of Kansas Medical Center, and all participants provided a written consent to participate in the study.

Patients in the CR group were enrolled in a formal CR program at our institution which comprised a total of 36 sessions. The control group did not undergo any formal exercise therapy but post-revascularization standard of care practices were followed. This included regular outpatient follow-up with focus on blood pressure management, statin therapy with goal low-density lipoprotein (LDL) <70 mg/dL, and antiplatelet therapy (dual antiplatelet therapy post angioplasty/stent and single agent therapy in case of bypass). Feasibility of CR was assessed as the ability to successfully complete all 36 sessions of CR, as this is the standard for CAD patients. Safety was defined by the absence of CR-related adverse events (falls, injury, etc.). Other safety parameters that were studied included incidence of myocardial infarction, stroke, rehospitalization, syncope, or chest pain. This information was obtained from medical records. QoL assessment was performed using the SF-36 form (Medical Outcomes Study 36-Item Short-Form Health Survey) at the start of the CR and at the end of the program. SF-36 scores were reported using eight scales in addition to health change scores as outlined in Table 2. A PAD-specific quality of life questionnaire (VascuQOL6) was also utilized similarly. Dyspnea and fatigue were measured during the initial and final 6-minute walk tests (6MWTs) using the Borg 0–10 scale. These QoL measures were chosen because of their widespread use in research, tested validity, and relative ease of use in the clinical setting.^7,8 Other endpoints assessed were incidence of claudication, mean distance, and number of laps walked. Baseline demographics and comorbidities between the two groups were compared using the Pearson χ² test for categorical variables and one way-ANOVA for continuous variables to identify significant univariate associations. Two-sided p value <0.05 was considered significant.

Results

The study enrolled 20 subjects (10 in CR group, 10 in control group). Mean age was 60.70 (±9.17) years in the CR group and 63.10 (±7.13) in the control group (p = 0.52). Women comprised 50% and 60% of the CR and control groups, respectively. One patient in each group underwent surgical bypass while all the other patients had endovascular interventions (stent and/or angioplasty). Both the groups had a high prevalence of atherosclerotic risk factors and comorbidities but lacked significant intergroup differences (Table 1). There were no baseline differences between the two groups in terms of walking scores or QoL surveys. All subjects in the CR group successfully completed a total of 36 sessions per protocol. No significant or unusual modification of protocol was needed for any subject. No subjects in either group had any cardiovascular (myocardial infarction, stroke, chest pain resulting in hospitalization or syncope) or mobility-related adverse events.

Table 1.

Comparison of baseline characteristics between the control and intervention groups.

Variable	Standard of careN (%)	Cardiac rehabilitationN (%)	p value
Number of patients	10 (100%)	10 (100%)
Mean age (in years)	63.1 ± 7.13	60.70 ± 9.17	0.52
Female	6 (60%)	5 (50%)	0.65
Race			0.31
White	8 (80%)	7 (70%)
Black	2 (20%)	2 (20%)
Unknown or not reported	0	1 (10%)
Diabetes	3 (30%)		0.51
Insulin-dependent	2 (20%)	2 (20%)
Non-insulin dependent	1 (10%)	3 (30%)
Tobacco use	8 (80%)	8 (80%)	1.00
Never	2 (20%)	2 (20%)
Past	6 (60%)	6 (60%)
Current	2 (20%)	2 (20%)
Coronary artery disease	5 (50%)	5 (50%)	1.00
Hypertension	9 (90%)	10 (100%)	0.31
Obesity (BMI>30)	2 (20%)	5 (50%)	0.16
Atrial fibrillation	1 (10%)	1 (10%)	1.00

BMI: body mass index.

Physical function, as measured by total distance walked during 6MWT and number of laps covered, showed a significant difference between the two study groups at study completion after 12 weeks. The CR group showed a greater increase in mean walking distance (63.8 m vs. 10.6 m in the control group; p = 0.04). Similarly, the change in mean number of laps walked was also greater in the CR group when compared to the control group (3.5 vs –1.1; p < 0.01). Although statistically not significant, change in VascuQOL and SF-36 scores (6 out of 8 scales) was noted to be higher in the CR group than the control group (Table 2). Incidence of claudication during 6MWT, albeit higher in the control group, was not found to be statistically significant (10% in CR vs 40% in control group; p = 0.12). No statistically significant differences were noted in either group for reported dyspnea or fatigue between the initial and final 6MWTs (Table 2).

Table 2.

Comparison of study outcomes between the control and the cardiac rehab groups.

Groups	Standard of care	Cardiac rehabilitation	p value
Results of the 6MWT
Change in mean total distance walked during 6MWT	10.55 m	63.75 m	0.043
Change in mean number of laps walked	–1.1	3.5	0.005
Mean difference in Borg Fatigue Scale	0.1	0.85	0.28
Mean difference in Borg Dyspnea Scale	2.0	1.0	0.48
Incidence of claudication	4	1	0.12
Quality of life measures
Change in VascQOL	0.8 (±3.76)	1.3 (±3.8)	0.77
Change in mean SF36 scores
SF36 Physical functioning	2	12	0.20
SF36 Role limitation due to physical health	20	25	0.76
SF36 Role limitation due to emotional problems	–12.29	6.68	0.12
SF36 Energy and fatigue	10	11.5	0.83
SF36 Emotional well-being	8.8	4.8	0.36
SF36 Social functioning	25	22.5	0.84
SF36 Pain	5.75	7.75	0.87
SF36 General health	7.50	14.00	0.35
SF36 Health change	5	19.44	0.36

6MWT: six-minute walk test; SF36: short form (36) Health Survey; VascQOL: vascular quality of life questionnaire.

Discussion

The results of our study suggest that CR is safe and feasible in patients who have undergone a recent revascularization procedure for PAD and improves walking ability compared to standard of care. This was a pilot study intended to test the primary outcomes of safety and feasibility of standard CR in these patients. All the 10 patients in the CR group were able to complete 36 sessions of CR with no patients suffering adverse events during and upon completion of the study. This safety/feasibility check of CR provides a platform for further prospective studies to research other clinical outcomes of CR in our patient population.

CR integrates supervised exercise therapy along with lipid management, smoking cessation, blood pressure control, nutrition/weight management, diabetes treatment, and psychosocial interventions.^9,10 It is also reported to reduce oxidized LDL, increase antioxidant activity, and improve endothelial function.^11–13 It is shown to be a very effective measure in improving QoL in CAD patients who undergo revascularization, and is a Class I recommendation in these patients.^14–16 PAD shares the same atherosclerotic substrate and risk factors and as thus, it is reasonable to expect benefit of CR in these patients. Despite the small sample size, our study was able to show that CR effectively improves walking ability in PAD patients who have undergone revascularization within 12 weeks.

Benefit of a supervised exercise therapy in patients with PAD after revascularization has been previously assessed in some studies which also reported improved walking distance and functional improvement.^17,18 However, these studies focused mostly on supervised exercise therapy (SET) and were not.

Although the QoL assessment (VascuQOL and SF-36) scores showed greater improvement in the CR group, these results did not reach statistical significance. The short follow-up (12 weeks), as well as the small sample size, could be contributory. Our results are hypothesis generating for future larger studies to address the therapeutic potential of CR in PAD patients following revascularization. Such studies will hopefully result in widespread utilization of CR facilities for these patients similar to that for CAD patients post revascularization.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iDs

Farhad Sami

Matthew Lippmann

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