2.1. Study Population and Study Design
We enlisted 60 patients with diagnosed CHF due to left ventricular systolic dysfunction, mean age 73 ± 6 years, ejection fraction 33 ± 9%, and M/F 51/9. All patients were in New York Heart Association (NYHA) functional class II. The cause of heart failure was ischaemic heart disease in 48 patients, idiopathic dilated cardiomyopathy in 12 patients. At the time of their enlistment all patients were out-hospital patients, attending to a cardiac rehabilitation program in our day hospital at IRCCS S. Raffaele Istitute of Rome. Inclusion criteria were age >65 years, CHF of more than one year duration due to ischemic or nonischemic dilated cardiomyopathy, left ventricular ejection fraction (LVEF) ≤45%, NYHA functional class II, stable clinical conditions and optimal HF treatment without changes for at least 3 months. Exclusion criteria were history of myocardial infarction or angina less than three months, decompensated heart failure, complex ventricular arrhythmia, angina, and neurological or orthopaedic conditions limiting the exercise protocol. This was an open randomized pilot study. After the completion of baseline testing participants were simply randomized by lot to either the CT group or the ET group. Thirty patients received CT treatment (Tai-Chi+ET) 3 times/week; 30 patients received ET treatment 3 times/week. All patients of the two groups were on top of their medical therapy.
All patients gave informed consent to participate in the study, which was approved by the local Ethics Committee and conforms to the principles outlined in the Declaration of Helsinki and to the GCP guidelines of the European Community.
2.2. Endurance Training
It was performed according to the AHA guidelines [11
]. Every exercise session included 10 minutes of warm-up, 10 minutes of cool-down and flexibility exercises, and 30 minutes of aerobic exercise with cycling or walking at 60%–70% of estimated VO2 max.
2.3. Tai Chi
In general, Tai Chi is a low-impact, weight-bearing exercise characterized by gentle movements designed to dissipate force throughout the body while the subject changes poses, with well-coordinated sequences of both isometric and isotonic segmental movements in the trunk and 4 extremities. Every session included 10 minutes of warm-up exercises, 30 minutes of Tai Chi practice, and 10 minutes of cooldown exercises. The Tai Chi programme was a modified 10-movement Yang style taught by an experienced Tai Chi instructor similar in style to the routine proposed by Wolf [12
]. One-to-two movements were taught each week for 8 weeks. The complete form was practised for the last 4 weeks of the study. Emphasis was placed on performing the movements in a slow, relaxed way. Tai Chi sessions were conducted by an expert Tai Chi trainer with a trained cardiac rehabilitation therapist also in attendance. During Tai Chi practice, subjects imitated the motions and postures of the Tai Chi instructor with the same speed.
In order to balance the total amount of exercise, exercise sessions were organized as follows: all subjects of both groups performed 4 sessions /week. Patients of the CT group performed Tai Chi for 30 minutes two times a week and cycling or walking for 30 minutes 2 times a week (in different days). Patients of the ET group performed cycling or walking for 30 minutes four times a week.
At baseline, in order to estimate their maximal exercise capacity, all subjects performed a symptoms-limited exercise test on a treadmill using a standard Bruce Modified protocol. A resting ECG was performed and repeated at the end of each stage during exercise and during the recovery phases. Data on heart rate and blood pressure were collected during these phases. Maximal oxygen uptake was estimated trough method of heart rate reserve and the training heart rate was estimated based on the following formula. Training heart rate = (maximum HR-resting HR) × desired intensity (%) + resting HR.
Changes on exercise tolerance
were evaluated by 6MWT. The test was performed at baseline and at the end of the study according to the standardized procedure [13
]. Each test was supervised by a physical therapist. Patients were asked to walk at their own maximal pace a 100
m long hospital corridor. Every minute a standard phrase of encouragement was told. Patients were allowed to stop if signs or symptoms of significant distress occurred (dyspnoea, angina) though they were instructed to resume walking as soon as possible. Results of 6MWT were expressed in distance walked (metres). The Borg scale was used to rate perceived exertion (RPE), and the perceived level of dyspnoea was rated on the Borg category ratio scale [14
During all the training sessions, HR was assessed in each subject (Polar Team System; Polar Electro Oy), and data were downloaded on a portable personal computer and analyzed using a dedicated software (Polar ProTrainer 5; Polar Electro Oy).
2.4. Quality of Life
All patients were administered at baseline and at follow-up examination a vertical visual analog scale to test their quality of life. The visual analog scale was a 10
cm line with a mark at each centimetre. Physical and social QOL were evaluated by MacNewQLMI [15
], a self-administered questionnaire previously validated in patients with MI [16
], angina [18
], and heart failure [19
]. MacNew included 27 items in three domains (physical, emotional, and social) with a Global score, has a 2-week duration, and is scored from 1 (low HRQL) to 7 (high HRQL).
2.5. Muscle Strength Measurement
Muscle strength measurement: to determine the maximal muscle strength, isometric dynamometry testing (REV9000, Tecno-Gym) of the quadriceps muscles was performed at baseline, and at the end of the study. All measurements were performed while the subject was seated on the device; the chest was fixed by 2 straps, the pelvis and knees flexed at an angle of 90°. The ankle of the tested leg was attached to the strength transducer by a Velcro strip and the patient then carried out 3 consecutive maximal voluntary extensions (contraction time 3
s—resting time 7
s); the highest value was considered as the maximal strength (MVC, N). The isokinetic muscle strength of the knee extensors was assessed by the same dynamometric system, recording the isokinetic strength as torque. Patients performed 5 consecutive knee extension movements with maximal effort and with an angular speed of 90°/s; with the dominant leg the highest value obtained was regarded as the peak torque (PTmax; Nm).
2.6. NT-pro BNP Assessment
At baseline and at 12 weeks Venous blood samples were withdrawn from an antecubital vein into chilled ethylene-diamine-tetraacetic acid Vacutainer test tubes after 20 minutes of rest with patients in a supine position. Samples were placed immediately on ice-cold water, and the tubes were then centrifuged at 4000
r.p.m. at 4°C for 15 minutes. NT-pro BNP was determined by a commercially available electrochemiluminescence immunoassay based on a polyclonal antibody-based sandwich chemiluminescence assay (Roche Diagnostics, Germany) using an autoanalyser (Elecsys 2010)
2.7. Statistical Analysis
Differences in baseline characteristics between CT and ET groups were evaluated by the chi-square and unpaired t test. Within-group changes in the reported variables were evaluated by the paired t-test or Wilcoxon signed rank test for nonnormally distributed variables. Between groups comparisons were performed by the unpaired t-test and Mann-Whitney rank sum test. The primary and secondary outcomes were evaluated comparing the delta (baseline—12 weeks) of CT versus ET using the Mann-Whitney test. Results are expressed as mean ± SD. A 2-tailed P value of <.05 was considered significant. All analyses were performed with a commercially available statistical package (SPSS for Windows version 12.0, Chicago, Illinois).