Physical Capacity at Cardiac Patients-Tests and Innovative Methods of Rehabilitation

Abstract

Cardiovascular diseases are the most common health problems in highly developed countries. After first rehabilitation stage, patients needs help with long-term recovery process. Physiotherapy for cardiac patients is multifaceted, but it is mainly based on physical capacity. Except physical activity also important are psycho condition and diet.

Actually, problems in patients after hospitalization are the lack of motivation to continue training (monotonous exercise) and the fear about pain (recurrence). Patients health during training should be monitored. One of the easiest and most available way is 6-minute walk test. Additionally patients need to have periodic, sensitive tests at clinic (exercise test on treadmill).

New scientific reports suggest extending classical rehabilitation ex. water activities, interval training, and more strength exercise. Variety of possible activity, which are safe for patients, will make rehabilitation more approachable.

Keywords: Efficiency; Physical capacity; Cardiac; Rehabilitation; Training

Introduction

Cardiovascular diseases, in particular ischemic heart disease and myocardial infarction, are the leading cause of death for people worldwide reported by WHO in 2019 [1]. Thus, the priority should be prevention, reducing the incidence of primary and subsequent diseases, preventing disability and untimely death. Physical activity and diet are the factors that the medical professionals have the most impact on during the cardiology patients treatment [2].

Physical exertion is any movement of the body caused by the work of large muscle groups including energy expenditure. Systematic physical activity has a beneficial effect on the cardiovascular system [3]. Physical activity with energy cost more than 4200kJ/week (1000kcal/ week) reduces overall mortality by 30% and the risk of coronary heart disease decreases from 30% to 50% depending on gender [4]. Physical activity of people with cardiovascular diseases is relatively small. Unfortunately, patients are often afraid of undertaking physical activity because of coronary pain [5,6]. According to research of CBOS organization, 51% of respondents aged 55-64 and 61% of those over 65 have not any physical activity in the last year [7]. This is a vicious circle of ischemic heart disease, as increasing sedentary behaviour increases the number of health problems and leads to more serious complications.

20 years of research has proven that people who train regularly have significantly higher levels of physical capacity, their cardiovascular system is more effective, and the incidence of coronary risk is lower [4]. The benefits of regular physical activity include ex. optimal heart rhythm, lower blood pressure values, longer diastolic heart phase, increase maximum minute capacity and cardiac ejection volume, increase number of coronary vessels and it’s diameter, increase coronary flow, increase physical capacity, improve quality of life, improve the respiratory system, decrease feelings of anxiety [8]. Physical activity should be considered as the main preventive and therapeutic method. Physical activity is the best way of prevention, which reduces the use of more radical and costly methods of treatment [2,9].

Physical Activity

To safely introduce the patient to the rhythm of physical activity, it is necessary to start with basic diagnostic tests (such as blood pressure measurement, blood count, urine test and ECG) and stress test with physical performance assessment. The subjectial interview should include questions about the subject’s experience of discomfort during movement and at rest, the occurrence of chest pain, loss of consciousness during exercise, or symptoms of exercise intolerance, such as nausea, vomiting, excessive unusual fatigue and prolonged muscle pain. It corresponds both to individual and supervised selection of the training program by the patients with coronary heart disease [10,11].

Physical activity undertaken by people with multiple risk factors for coronary heart disease or many concomitant diseases should not be too intense, aggravating or performed without the supervision of a physiotherapist and doctor. In order to more accurately arrange the appropriate schedule of activities, the society of cardiology recommends to use the four-stage scale of patients into cardiac groups used in rehabilitation.

Physical activity recommended for people with coronary heart disease is endurance training. It should be done systematically, at least 3 times a week, at an intensity level of at least 60% of the maximum heart rate (HRmax), and each training should last at least 30 minutes [11]. Endurance training should be complemented by additional strength training. Each workout should be preceded by a warm-up and ended with calming exercises.

Physical activity recommended for people with coronary heart disease is primarily an activity that patients will perform with pleasure. Lack of regularity will directly affect stagnation and even deterioration of health. It is also recommended to combine and intertwine different sports such as walks, Nordic Walking, cycling, swimming, team games, fitness, circuit training or ballroom dancing. This should be complemented by the physical activity of everyday life that includes climbing stairs instead of taking the elevator, walking or cycling instead of driving, limiting the time spent watching TV or in front of a computer [12].

Although physical activity is desirable in cardiac patients, there are contraindications to the use of physical training, which include unstable angina pectoris, suspected heart attack or acute myocardial infarction, uncontrolled arrhythmias that cause haemodynamic disorders, endocarditis, pericarditis and myocarditis, decompared heart failure, aortic aneurysm, lung disease during respiratory failure, thrombophlebitis, acute febrile diseases, uncompared hypertension at rest (systolic >180mmHg, diastolic >110mmHg), cerebral focal symptoms in the last 3 months, as well as other conditions requiring intensive patient supervision [11,12].

As a result of systematic physical activity, the physical performance of the body increases. The term “physical capacity” according to the AHA (American Heart Association) is the ability to perform an exercise determined by maximum oxygen absorption, which in practice means the ability to conduct daily activity based on oxygen metabolism. Physical capacity can be divided into aerobic performance for long-term efforts, anaerobic performance for intensive but short-term efforts, and special capacity for a specific type of work performed.

Physical capacity depends on many factors such as the energy capabilities of the body (aerobic energy potential, anaerobic, energy reserves), physical condition (strength, speed, and body weight), diet, level of daily physical activity or mental state. One of the main factors determining physical capacity is the efficiency of the mechanisms of oxygen supply during work, that is, efficient absorption of oxygen from the environment (ventilation, lung capacity), efficient transport of oxygen (blood oxygen capacity, heart minute capacity), the amount of circulating blood and the supply of the tissues (adequate distribution of blood, diffusion of oxygen at the tissue level and disposal of oxygen by tissues). Beyond the objective criteria of physical capacity, the measure of physical capacity may be the amount of work done, the length of the walking distance, the number of floors or steps achieved by the test subject until objective or subjective symptoms of fatigue (Borgs scale) [11,13].

Objective Diagnostic Tests of Physical Capacity

The assessment of physical capacity can be measured by objective tests and subjective scales. The advantage of every evidence based medicine stress test is the repeatability and possibility of monitoring the heart work, which gives safety. Evaluating physical capacity during a stress test is very important because it allows to be classified according to the New York Heart Association (NYHA). NYHA functional classification takes into account the severity of symptoms and physical activity. Also actually and verify classification is classification of angina severity according to the Canadian Society of Cardiology (CCS) [13].

The 6-minute walking test (6-MWT) is one of the simplest, indirect tests for objective assessment of physical capacity. Made to the standards is a valuable tool for assessing the problem level and to verify progress of treatment at cardiac patients. It involves walking as long as possible (in meters) within 6 minutes [14]. This is a basic diagnostic test used to monitor the progress of cardiac patients in the United States, South America, Africa and Australia [15].

Electrocardiographic stress test is performed on a cycloergometer or trademill and enables indirect measurement of physical performance. To create stress test safety, the supervisor has to monitor some physical and physiology symptoms, which limit the tests, i.e. until the patient achieves high fatigue assessed by the Borgs scale or the onset of symptoms forcing the study to stop (ex. reaches HRmax, arrhythmia). The maximum effort shall be assessed in relation to duration and intensity. The intensity of effort on the cycloergometer is measured in Watts (W) and on the treadmill in Metabolic Equivalents (MET). These tests provide information about the patient’s body, not only an electrocardiographic of ischemia, but also in the response of heart rate and blood pressure to exercise. The stress tests are as a valuable tool for assessing physical performance in cardiac rehabilitation clinic [13].

The Bruce protocol is a type of electrocardiographic stress test. The second most popular, immediately after 6-MWT diagnostic test used in monitoring the progress of cardiac rehabilitation. Due to its exactness and safety are often used in Europe and the USA [15]. Carried out according to the original protocol, it is intended for patients with good capacity, so most cardiac laboratories use a modified version with an additional two low levels (from 2,3 MET instead 4,6 MET). This test is performed on a treadmill and lasts about 18 minutes. The patient begins the walk at a low speed 2.7km/h and 0 angle of inclination. Every 3 minutes, the lead increase. The end occurs when the patient achieves a Heart Rate (HR) at the level of HRmax adequate for his age and gender, or faster when the monitored parameters change adversely [16].

The Spiroergometric Exercise Test (CPX) is a reference method for assessing physical performance. In addition to the electrocardiographic test this test measures additionally oxygen absorption, respiratory volume and CO₂ excretion. Oxygen absorption at the anaerobic transformation threshold point (AT) is also assessed. In this exercise test, the measure of physical capacity is the maximum oxygen absorption (oxygen ceiling- vo2max, aerobic capacity of the system). In patients with cardiovascular disease, this test is modified and does not consist in achieving VO₂ max, but in the absorption of oxygen at the peak of exercise, with a high fatigue corresponding to 7-8 points on 10 grade Borgs scale. In addition to oxygen absorption and CO₂ excretion parameters, CPX gives the ability to assess ventilation – a minute ventilation ratio for CO₂ excretion (VE/VCO₂ slope) and an oxygen efficiency index (OUES) that characterizes the strong of respiratory response to exercise [13,16].

A maximal stress test is a progressive test performed on a cycloergometer or treadmill using a spirometric equipment to the patient’s refusal. Determining the basic values of the parameters by this method makes it possible to accurately determine the intensity of physical training and the professional and recreational opportunities of the patient (especially important for young adult patients). At first, heart rate and breathing at rest are measured. Then we proceed to exercise, during which the load increases. This includes further levels for increasing the load, up to the famous “refusal”, i.e. the end of the test. The load is increased smoothly and the moment of refusal is individual for the patient. The patient ends the test after reaching his maximum capabilities. During the test, we also study parameters such as maximum power, maximum oxygen uptake, maximum heart rate, heart rate in AT point. The test can be ended faster by the supervisor if symptoms from the group of contraindications will appear [17,18].

Load Echocardiography allows to differentiate diseases of the heart muscle and valves. This test assesses the morphology of the muscle, heart valves, large blood vessels, functions of contraction and diastolic of the heart, disorder of myocardial contractility, flow and pressure in the heart cavities. Making the echocardiographic tests at rest and at the peak of exercise shows changes in heart function during physical exertion with controlled load. Due to the need for additional medical equipment and a specifically trained medical staff, the method is less popular than CPX [13].

Spiroergoechocardiography (CPXE) involves one-time exercise echocardiography and spiroergometric test on a reclining cycloergometer. This allows you to correlate the functional changes evaluated during the imaging test with the dynamics of electrocardiographic, metabolic and ventilation parameters and allows you to objectify the degree of fatigue: achieving AT and RER ≥1 (Ratory Exchange Ratio). The benefits of using this exercise test are a combined cardiac, pulmonary and metabolic evaluation, functional evaluation of the patient’s heart function, increasing the prognostic value of exercise echocardiography by attaching spiroergometric parameters [13].

Surface Electromiography (sEMG), which has been used recently to monitor muscle work during exercise in athletes, has recently also attracted interest from cardiac rehabilitation teams. Abnormal heart function may cause peripheral perfusion disorders leading to dysfunction of many organs including muscles [34]. A precise functional and tissue assessment would increase the level of advisability of selected improvement processes. Electromiography is a measurement technique based on the bioelectricity of active muscles. Muscle work closely related to the change in the electrical potentials of cell membranes is detectable on the surface of the skin in an objective and repetitive manner. The signal is collected non-invasively through sensors from properly attached electrodes [31]. However, it should be noted that the place where the electrode is glued on the skin in the area of a given muscle is not accidental. Until now, a big challenge for scientists has been to denoise (neutralize overlapping of noise) the collected sEMG signal from other muscles and tissues. [33] Thanks to the recently created nonlinear noise reduction, the collected signal is more accurate and collected also from lower values [32]. Qualitative and quantitative information on muscle work can be used as a basis for assessing a patient’s readiness for a particular type of exercise.

Subjective Diagnostic Methods of Physical Capacity

Physical capacity in the absence of suitable conditions, for screening purposes or taking into account the subjective sensations of patients can be measured using the Borg Scale (10 – or 20 – gradual), which consists in determining the patient’s fatigue with the appropriate physical load [19]. Buckley’s et al. provided interesting conclusions, in which they showed that for the same physical capacity value determined in the stress test, the level of fatigue can vary in subsequent physical training sessions. The Borg scale is not as precise as the stress test, but it is easy and safe, allowing it to be used in all conditions and combined with selected stress tests [20]. The degree of physical capacity determined in this way in patients has a therapeutic and initial diagnostic significance. Evaluation in patients undergoing cardiac rehabilitation allows to determine the tense response to physical exertion, bioelectrical activity of the heart, exercise tolerance and physical capacity [21]. The result of the exercise test is the basis for determining the intensity of physical exertion undertaken for example during physical activity at home.

In 2013, the objective and subjective method of assessing physical fitness in people undergoing outpatient cardiac rehabilitation due to a heart attack were compared [19]. The study involved 40 patients - 9 women and 31 men aged 42-82 years who underwent coronary angioplasty surgery due to myocardial infarction and participated in outpatient cardiac rehabilitation. Rehabilitation consisted of 24 onehour sessions 2-3 times a week. Each session consisted of 20 minutes of general fitness exercises, 30 minutes of cycling and 10 minutes of calming exercises. Training on cycloergometers was an interval training with alternating periods of load and rest. They started training with a load of 20W, which was increased so that each time it caused fatigue 11-12 on the Borg scale. The results are shown in (Figure 1).

    

    

    Figure 1: The influence of cardiological outpatient rehabilitation of the physical efficiency of the subjects with a history of myocardial infarction. Results at the
beginning and at the end of rehabilitation. A: Efficiency; B: Time span of the effort stress; C: Work inducing relatively small exertion, *p<0,05 [19].