The Risk for CHD and CVD - Example

Physical Section: A meta-analysis research was carried out by Williams (2001) in which he reviewed various studies which involved measurement of the risk for CHD and CVD in relation to physical activity and physical fitness level. His study indicated that CHD and CVD are inversely proportional to physical activity levels. Furthermore, his findings indicated that CVD and CHD risk is inversely proportional to cardiovascular fitness although the risk of CVD and CHD declined precipitously in the initial 25th percentile of cardiovascular fitness that was absent in physical activity. Williams (2001) also reported a significant decrease in relative risk at all levels that was higher for cardiovascular fitness as compared to that of physical activity level. From these findings it can be suggested that cardiovascular activity is capable of decreasing CHD and CVD risk than physical activity. CHD Risk factors Section: Inflammation can be reduced by exercise training and hence it can reduce the rate of cardiovascular pathogenesis progression and atherosclerosis since inflammation has been implicated in aetiology of these conditions. A survey carried out between 1988 and1994 by the National Health and Nutrition Examination Survey (NHANES) III involving 13,748 adults from USA indicated that an increase in exercise intensity results in a corresponding decrease in C-reactive proteins, the white blood cell count and plasma fibrinogen (Ford, 2002). A randomly designed study aimed at evaluating the impact of physical activity on blood lipid levels was conducted in Attica basin from 2001 to 2002. The study had 2772 participants 50.3% of which were women. The evaluation of physical activity in this study included frequency, intensity and duration. The results of the study indicated that a decrease in physical activity was accompanied by an increase in blood lipids. In addition, the study indicated that light to moderate exercise intensity could result to emergence of inflammatory markers contrary to prior findings which indicated that strong physical exercise could help in prevention of cardiovascular condition. Various studies have indicated that physical exercises lower arterial blood pressure levels (Sesso et al., 2000; Thompson et al., 2003), decreases coagulation and inflammation markers (Lakka et al., 1994; Abramson et al., 2002; Wannamethee et al., 2002; Pitsavos et al., 2003) and hence lowers the risk of coronary thrombosis. A study carried out by Pawtucket Heart Study group (Eaton et al., 1995) showed that physical activity lowers body mass index and blood pressure and increases the level of HDL cholesterol. Hsieh et al (1998) also reported in a study involving 3000 Japanese men that physical activity is directly proportional and independently related to the level of HDL cholesterol. A combined analysis of three cohort studies in Europe involving aged men reported a significant proportionality between HDL-cholesterol and physical exercise (Bijnen et al., 1996). Cardiorespiratory Fitness Definition Section: Cardiorespiratory fitness refers to the ability of the body to carry oxygen to various muscles of the body during prolonged period of physical exercise and the ability of muscle cells to absorb and utilise oxygen for generation of energy in the form of ATP (adenosine triphosphate) through the process of respiration. Cardiorespiratory Fitness Section: The risk of death from coronary heart ailment can strongly be predicted by cardiorespiratory fitness (Myers et al., 2002). A study involving 2534 cardiovascular patients and 3679 healthy participants aimed at establishing the impact of exercise capacity on survival reported that peak exercise capacity was a strong risk predictor for both healthy and ailing participants. It was reported that a 12% survival improvement was conferred for every 3.5mlO 2 /kg/min (1 MET) increase in exercise capacity. From the study findings it is imperative that physical fitness is essential for symptomatic men. Different approaches CRF Section: The effect of exercise capacity improvements on the risk of death from cardiovascular diseases was also demonstrated by Kavanagh et al (2002) in a retrospective cohort study which was carried out between 1968 and 1994 and involved 12,169 who were undertaking cardiac rehabilitation. A progressive test using a cycle ergometer braked electrically was undertaken by the patients until they were subjectively exhausted, oxygen intake plateaued or they were contraindicated to continue (ACSM, 2000). The patients were followed up for about 7.9 years. The study findings indicated that VO 2 peak obtained through cardiac respiratory testing was the major single predictor of death from cardiac ailment in spite of the diagnosis of CABG, MI or ischemic heart disease (IHD). The findings indicated that mortality decreased by 9% for every 3.5mlO2 /kg/min improvement in fitness. Following this results, Kavanagh (2002) argued that CHD patient rehabilitation should involve assessment patient’s exercise capacity and cardiovascular fitness progression. Another study by Vanhees et al., (1994) sort to establish the impact of training on patients recovering from coronary artery bypass graft (CABG) and myocardial infarction (MI). They established that mortality decreased progressively with aerobic power in patients with a V̇O2peak of 15.5 mL/kg per minute and 20% of patients with 32.3 mL/kg per minute aerobic fitness. It was established that patients in the upper 2/5 of category of highest fitness had greatest prognosis difference. The study established that cardiovascular mortally declined by 2% for every 1% peak VO2 increase after training. A study by Dorn et al., (1999) examined the impact of exercising on the risk of CVD death in 651 male myocardial infarction patients aged between 30 and 64 years. The study followed up the patients for a period of 19years until all had died. Initially the study involved randomised control trial exercise among the participants in which the intervention group underwent supervised exercise in a laboratory for eight weeks. The intervention group was then involved in cycling, jogging or swimming in a pool/gymnasium setting under guidance of personalised target heart rate. Control group participants did not to participate in regular exercises but maintained normal routines. The participants’ medical history was established through interviews, they underwent physical examination and multistage graded exercise test using a treadmill monitored using ECG prior to enrolment and after every six months till they died. The study established that the risk of CVD mortality declined by between 8% and 14% for every increase in exercise capacity by 1 MET and that initial exercise capacity does not however prevent death from CVD. One main shortcoming of the study was that no information was provided for the effect of the program on surgical procedures, hospitalization, quality of life, unstable angina and non-fatal events after MI. In addition, the study did not monitor exercise and other pharmaceutical or medical intervention or other lifestyle habits after the initial trial. 6MWT Section: Symptomatic HF patients highly reproduce the 6MWT. Quality of life and NYHA-FC are somehow related to 6MWT. A RESOLVD study indicated that NYHA-FC and 6MWT are comparable but less responsive to change than quality of life. Treadmill problem Section: Treadmill training has some shortcomings. The test requires costly equipments, patients unfamiliar with the test are usually anxious in initial stages, requires specialised training for the operator and the participants’ learning ability impacts on the test. Unlike free walking, treadmill walking is associated greater workload. Unlike treadmill walking, walking tests requires no training for both the patient and operator, are straight forward and cheap. However, the self paced nature of walking test is not able to clearly distinguish limited and minimally limited patients (Arnott, 1997). Singh et al (1992) argued that it is hard to standardise walking tests since they depend to some extend on the encouragement and motivation of the participant by the operator. ISWT test has managed to overcome the problem associated with self paced walking tests. In this test audio signal increments are used to determine increases in pace. Thus, the influence of the operator on the performance of the patient is limited and thus the patients can attain their VO2peak. Thus, the results obtained using ISWT are more valuable than any other tests (Singh et al, 1992). Validity Section: In a study involving 24 participants Kervio et al. (2004) sort to assess the 6-MWT validity by comparing it with treadmill exercise that was symptom limited and its reliability in moderate HF patients. The 6-MWT results indicated a similarity with sub-maximal treadmill exercise test which was equivalent to approximately 90% of VO2max and were reliable. The researchers found daily differences in maximal HR and VO2max which the argued were essential for HF patients’ functional capacity assessment. Thus, the researchers recommended that in order to obtain more accurate results, evaluation of HR and VO2max ought to be performed at a specified time of the day. Reliability Section: One of the most convenient functional capacity tests in HF patients is 6-MWT (Ingle et al., 2005). A questionnaire covering physical function aspects and a baseline performance of 6-MWT by patients and one follow up after a year were used to asses HF symptoms. Prognostic Section: An investigation by Fiorina et al. (2007) aimed at establishing the feasibility of measuring cardiac rehabilitation program using 6-MWT and at testing the impact of some demographic and clinical variables that were relevant on the performance of adult and older population on walking. The 6-MWT results of Fiorina et al. (2007) were reported in percentages of predicted values and absolute values based on Enright and Sherrill‟s (1998) equation that uses age, sex, weight and height variables. The study reported that repetition of 6-MWT among 348 patients after rehabilitation increased distance walked significantly to 411 ± 107 m (81 ± 20%) from 281 ± 90 m (55 ± 16%). A 10% increase was recorded between the fast and final test in distance walked among 85% of patients. From these findings, Fiorina et al. (2007) argued that the 10% increase between the two tests was a true indication of functional capacity improvement in the intervention group (Schuler et al., 1992). Biomechanical Section: Biomechanical inefficient refers to abnormal gait cycle of a person in which a person excessively or slightly rolls his/her foot inward or outward while walking. Validity of the ISWT Section: Various studies have indicated that cardiorespiratory capacity can validly be measured using the SWT as opposed to measurements using gold standard. The validity of SWT was first evaluated by Singh et al. (1994) in which it was compared with treadmill test. Their study involved 29 participants and they established a strong correlation VO2max and exercise performance in airflow limited patients. Their initial experiment indicated a strong correlation (r=0.88) between the SWT and VO2max obtained during a treadmill test. They came up with a predictive equation for VO2max (VO2max= 4.19 × (1.12–7.17) + 0.025 × (0.018–0.031) × SWD) which had a 95% confidence intervals. A second experiment verified the high correlation (obtained r=0.81) between distance walked and VO2max through assessment of physiological responses to the SWT. Thus, they concluded that SWT was highly correlated to maximal oxygen consumption (functional capacity) thus it (SWT) can be used in the VO2max prediction. As a result they concluded that cardiorespiratory capacity can validly and safely be evaluated using SWT using simple maximal exercise tests in incremental steps. Another study aimed at establishing the reliability and validity of the SWT involved 39 patients who had undergone CABG within the past 6 to 8 weeks (Fowler et al., 2005). One week after enrolment the patients underwent a treadmill test and completed 3 SWTs. Eleven of the recruited patients attended a CR program which was hospital based for 6 weeks. The distances recorded in the 3 SWTs were strongly correlated and had no significant differences. However, higher maximum breathlessness and HRs scores were produced by treadmill tests that the SWT. This implied that SWT causes less physiological stress as compared to treadmill test. In addition, cardiorespiratory capacity changes were detected by SWT after the CR program. Thus, it was concluded that SWT has a high reliability, validity and sensitivity for the investigation of exercise tolerance patients recovering from CABG surgery. Even though a learning effect was established between the first and second SWT of a mean difference of 40m, non was found between the third and the second. Thus they suggested that prior to using SWT, a pre-practice test is essential although they recommended that the results need to be obtained on a stable baseline for clinical reasons. The authors suggested that another study ought to be undertaken since these results were obtained within a short span of time (one week) as opposed to the fact that MSWT is employed in assessing changes for a longer period of time (between 6 and 12 weeks) in CR program. A 95% CI was shown when a regression plot was drawn for MDW and VO2 peak in ml.kg.min. This resulted in the following equation: 7.81 + (0.03x ISWT distance (m)). SWT Reliability section: In a recent study, Jolly et al (2008) analysed 353 CR participants recruited from the Birmingham Rehabilitation Uptake Study (BRUM) to establish the necessity of ISWT. Singh et al., (1992) methodology was used to asses the practice and second ISWTs after 6 months of being recruited into the trial. The patients took the first ISWT practice and rested for 30 minutes prior to undertaking the second test. The distance walked, the peak HR and the reason for stopping the test were recorded. A follow up for 353 participants after 6 months provided paired ISWT data. The mean age for follow up participants was 61.6 (±10.2) years. A mean (S.D) of 414.8 m (±157.5) was obtained from the practice to the second walk which was a significant increase from a mean S.D of 385.3 m (±151.8). The RPE (rating of perceived exertion) and maximum HR scores were not significantly different in the two trials. Thus it was concluded that familiarization could be responsible for distance walked increase in second trial. However, the study could not rule out the presence of learning effect since a third test was not undertaken. SIX MINUTES WALK TEST PROBLEM: Compared to other exercise tests, 6-MWT is not strictly standardised and this creates variability in measurements obtained using it (Revill et al., 1999). Unlike SWT where patients are required to increase their output in terms of exercise intensity till they meet a predetermined criterion, severe cardiorespiratory patients undertaking 6-MWT are allowed to rest during the test. According to Turner et al. (2004), 6-MWT does not provoke cardiovascular responses like the SWT. In addition, according to Arnott, (1997) the self paced nature of walking test is not able to clearly distinguish limited and minimally limited patients. Singh et al (1992) argues that SWT test has managed to overcome the problem associated with self paced walking tests. Read More