Dennis J. Kerrigan

Greater improvement in cardiorespiratory fitness using higher-intensity interval training in the standard cardiac rehabilitation setting.

PURPOSE: We tested the hypothesis that higher-intensity interval training (HIIT) could be deployed into a standard cardiac rehabilitation (CR) setting and would result in a greater increase in cardiorespiratory fitness (ie, peak oxygen uptake, ) versus moderate-intensity continuous training (MCT). METHODS: Thirty-nine patients participating in a standard phase 2 CR program were randomized to HIIT or MCT; 15 patients and 13 patients in the HIIT and MCT groups, respectively, completed CR and baseline and followup cardiopulmonary exercise testing. RESULTS: No patients in either study group experienced an event that required hospitalization during or within 3 hours after exercise. The changes in resting heart rate and blood pressure at followup testing were similar for both HIIT and MCT. at ventilatory-derived anaerobic threshold increased more (P < .05) with HIIT (3.0 ± 2.8 mL·kg·−1min−1) versus MCT (0.7 ± 2.2 mL·kg·−1min−1). During followup testing, submaximal heart rate at the end of stage 2 of the exercise test was significantly lower within both the HIIT and MCT groups, with no difference noted between groups. Peak V˙o2 improved more after CR in patients in HIIT versus MCT (3.6 ± 3.1 mL·kg.−1·min−1 vs 1.7 ± 1.7 mL·kg.−1·min−1; P < .05). CONCLUSIONS: Among patients with stable coronary heart disease on evidence-based therapy, HIIT was successfully integrated into a standard CR setting and, when compared to MCT, resulted in greater improvement in peak exercise capacity and submaximal endurance.

Muscular strength and cardiorespiratory fitness are associated with health status in patients with recently implanted continuous-flow LVADs.

INTRODUCTION: Patient health status (PHS) and peak oxygen uptake ( O2) are important predictors of clinical outcomes in individuals with heart failure. Preliminary studies of individuals with left ventricular assist devices (LVADs) show improvements in both PHS and peak O2. However, the relationship between peak O2 and PHS in this population is not well described. Likewise, data regarding muscular strength are also lacking in this population. We sought to describe the association between peak O2, muscular strength, and PHS in patients with continuous-flow LVADs. METHODS: Subjects (n = 26; 7 women) completed a symptom-limited graded exercise test within an average of 82 days (range, 33-167 days) of LVAD implant. In addition, subjects underwent a 6-Minute Walk Test and an isokinetic knee extension strength test and completed the Kansas City Cardiomyopathy Questionnaire (KCCQ). Spearman correlation coefficients were performed, adjusting for body weight and gender, to examine relationships between variables. RESULTS: Muscular strength, as measured by peak torque, and peak O2 were both moderately associated with the KCCQ (r = 0.58, P = .006; r = 0.51, P = .019). A subanalysis revealed that muscular strength and peak O2 were related to different domains within the KCCQ. CONCLUSIONS: Leg muscle strength and peak O2 appear to be important factors related to PHS in patients with continuous-flow LVADs. This is likely partially a result of deconditioning due to recent hospitalization, as well as persistent heart failure–related peripheral maladaptations in skeletal muscle. Incorporating both a cardiovascular as well as strength training program before and after LVAD implant surgery may be beneficial.

Relationship Between Leg Muscle Endurance and OE/OCO2 Slope in Patients With Heart Failure

PURPOSE Ventilatory efficiency, as measured by the slope of the relationship between minute ventilation and carbon dioxide production (&OV0312;E/&OV0312;CO2 slope) during cardiopulmonary exercise (CPX) testing, is an important prognostic measure in patients with heart failure (HF). An abnormal slope is linked to the skeletal muscle metaboreflex. In addition, skeletal muscle endurance is reduced in patients with HF. However, the relationship between &OV0312;E/&OV0312;CO2 slope and skeletal muscle endurance is not known. This investigation tests the hypothesis that reduced knee extensor muscle endurance is inversely related to an elevated &OV0312;E/&OV0312;CO2 slope during CPX testing in patients with HF and that these variables are not related in normal subjects. METHODS Patients with HF (n = 32) and 6 age-matched normal subjects performed CPX testing and isokinetic dynamometry to determine the &OV0312;E/&OV0312;CO2 slope and knee extensor muscle endurance, respectively. RESULTS The &OV0312;E/&OV0312;CO2 slope and leg muscle endurance percentage were significantly related in patients with HF (r = −0.68, P < .001), but not in normal subjects (r = −0.11, P = .83). DISCUSSION Based on these data, abnormalities of skeletal muscle endurance of patients with HF partially account for (r2 = 0.46; standard error estimate = 6.6) abnormalities of ventilatory efficiency, as measured by the &OV0312;E/&OV0312;CO2 slope. This finding helps explain, in part, the factors that influence an established prognostic indicator, elevated &OV0312;E/&OV0312;CO2 slope. Future research is needed to determine whether the relationship between skeletal muscle dysfunction and ventilatory efficiency is directly mediated through the skeletal muscle ergoreflex.

Exercise Training Workloads Upon Exit From Cardiac Rehabilitation in Men and Women: THE HENRY FORD HOSPITAL EXPERIENCE.

Purpose: To describe exercise training workloads, estimated as metabolic equivalents of task (METs) both upon exit from cardiac rehabilitation (CR) and as the change in MET level following CR, stratified by age, sex, initial MET level, number of sessions completed, and qualifying event at entry into CR. Methods: A retrospective study involving 8319 (31% female) patients who completed ≥9 exercise training sessions in the early outpatient CR program at Henry Ford Hospital. Exercise training MET levels achieved during CR were estimated on the basis of the speed and grade recorded from a treadmill. Exercise training METs at the start of CR were defined as the average of the second and third sessions, whereas MET level upon exit from CR was determined from the average of the last 2 patient encounters. Results: The overall mean MET level while training just prior to exit from CR was 3.9 ± 1.4 (4.1 ± 1.4 and 3.3 ± 1.0 in men and women, respectively). The mean change in METs after CR was 1.3 ± 1.1 (+45% ± 37%) and 0.9 ± 0.7 (+40% ± 32%) in men and women, respectively. Conclusions: In a large and demographically diverse cohort of patients who participated in CR, increases in mean workload (ie, METs) during exercise training were observed that approximated 45% in men and 40% in women. These data could be considered when establishing benchmarks for program-related performance outcome measures.

Heart Rate and V˙O2 Concordance in Continuous-Flow Left Ventricular Assist Devices.

UNLABELLED The American College of Sports Medicine currently recommends the HR reserve (HRR) method to guide exercise in individuals who have heart failure with reduced ejection fraction. This recommendation is based on the known association between %HRR and percentage of V˙O2 reserve (%V˙O2R) in this population. However, to our knowledge, no studies exist regarding this relation in individuals with a left ventricular assist device (LVAD). PURPOSE This article aimed to describe the relation between V˙O2 and surrogate markers of exercise intensity among patients with LVAD. METHODS Patients with continuous-flow LVAD (n = 24, seven females) completed a symptom-limited graded exercise test on a treadmill. HR and V˙O2 were measured continuously and averaged every 20 s. Regression equations were determined using a generalized estimating equation to predict %V˙O2R from %HRR, Borg RPE, and LVAD flow, overall and stratified by presence of pacing. RESULTS Although the association between %HRR and %V˙O2R was good (R = 0.75), the slope and y-intercept for %HRR versus %V˙O2R was different from the line of identity (P = 0.002). However, when paced subjects were excluded (n = 8) from the analysis, there was no significant difference between the slope and y-intercept (= 0.036 + 0.937 × %HRR; SEE, 2%; P = 0.052). RPE showed a strong association with %V˙O2R (R = 0.84), whereas LVAD flow showed a weak (albeit statistically significant) association (R = 0.05). Both had slopes and y-intercepts that were different from the line of identity (P < 0.05). CONCLUSIONS In patients with LVAD who are not paced during exercise, the use of %HRR is a good predictor of %V˙O2R. However, for patients in this population who are also paced during exercise, RPE is a suitable surrogate measure of exercise intensity.