Etching technologies

The 6MWT was performed according to the recommendations of the American Thoracic Society(119) on a long, flat, straight external ward corridor that was marked at 5m intervals measuring 30m where rapid, appropriate emergency response was possible.

Subjects were requested to eat light meals on the day of the test and wear light comfortable clothing. A stopwatch with a lap counter was used as a timing device for the duration of the test.

Minimally-assistive devices e.g. walking sticks were accepted and documented.

Subjects were instructed to walk the corridor from one end to the other, as many times as possible within the permitted time.

The test was performed under the supervision of the candidate and/or trained assistants who encouraged the subjects with remarks such as “you are doing well” at regular intervals. Subjects were allowed to stop and rest during the test, but were instructed to resume walking as soon as they felt able to do so.

At the end of the 6 min, the total distance walked by the patient was measured with a measuring tape.

The 6MWT was stopped immediately if any of the following was observed: chest pain, intolerable dyspnoea, leg cramps, staggering, diaphoresis, and a pale or ashen (bluish hue/cyanosed) appearance. Such subjects were then clinically evaluated including but not limited to an electrocardiogram and treatment instituted immediately where necessary.

b) Health Related Quality Of Life

The Minnesota Living with Heart Failure questionnaire (MLHFQ) was self-administered by recruited subjects with the help of the candidate or assistant where necessary. The questions were translated into Yoruba for those who did not understand English. The degree of help given by the candidate or assistant depended on each patient’s ability to read, write and comprehend the questions. If a patient showed difficulty for whatever reason, the candidate or assistant read the questions aloud and wrote down the oral responses given. Ample, uninterrupted time was provided for the patient to complete the questionnaire. The subjects answered the questions without being influenced by others such as their spouse or family members as much as possible. Respondents were made to understand they are to mark zero for any items that do not apply to them, rather than leave a blank in order to reduce bias and complicate analysis of missing data.

The MLHFQ contains 21 items with 6-point response scales ranging from 0 to 5. The MLHFQ includes sub-scales for physical (8 items) and emotional (5 items) HRQoL and 8 additional items that are part of the total MLHFQ(43,70).

The questionnaire was scored by summating the responses to all 21 questions to produce the total (global) HRQoL score. In addition, three subscale scores (dimensions) which reflect the physical

dimension (items 2, 3, 4, 5, 6, 7, 12, 13), emotional dimension (items 17, 18, 19, 20, 21) and the other items are related to financial, medication side-effects, and lifestyle considerations (overall dimensions) have been scored by simple summation to further characterize the effect of heart failure on a patient’s life.

The Behlouli et al.(132) MLHFQ score cut-offs determined by neural network approach was adopted where a score of < 24 on the MLHFQ represents a good HRQoL, a score between 24 and 45 represents a moderate HRQoL, and a score >45 represents a poor HRQoL.

c) Echocardiography

Two-dimensional (2-D) and two-dimensionally (2-D) directed M-mode echocardiography was performed on each subject in the left lateral decubitus position with simultaneous ECG recording using Toshiba Xario-XG and Nemio-XG (Toshiba Medical Systems, Tokyo, Japan) echocardiography machines equipped with a 3.5-4.5 MHz cardiac sector transducer probes.

LV internal diameter, inter-ventricular septal and posterior wall thickness was measured at end diastole and end systole. The LV end-diastolic and end-systolic dimensions was measured at the level of the mitral leaflet tips as the largest and smallest LV dimension, respectively according to the American Society of Echocardiography leading edge to leading edge criteria (58). Average measurements in three cardiac cycles were taken.

Left ventricular (LV) function was assessed by determining left ventricular ejection fraction and fractional shortening. LV ejection fraction was subsequently calculated using the Teichholz calculation formula(133) while fractional shortening was calculated from LV internal dimensions in diastole and systole (LVIDd, LVIDs) thus:

As proposed by Little and Applegate(134), left ventricular ejection fraction (LVEF) was considered normal if it was greater than 50% and impaired if it was less than 50%.

Cardiac output was determined from the product of calculated stroke volume (end-diastolic volume minus end-systolic function) and heart rate divided by 1000. The same was subsequently indexed with the body surface area in the calculation of the cardiac index and normal value taken to be 2.0 - 5.2 l/min/m²(135).

Left ventricular diastolic function was evaluated with the mitral inflow velocities which were measured from the apical four chamber view with pulsed-wave doppler and with the sampling volume positioned at the tip of the mitral valve leaflets. The inflow characteristics were quantified by measuring the trans-mitral "E" wave velocity (peak early mitral inflow velocity), "A" wave velocity (peak atrial mitral inflow velocity), the E/A ratio, deceleration time (time interval of peak E wave velocity to its extrapolation to the baseline) and the iso-volumic relaxation time (time interval from closure of the aortic valve to onset of LV filling by opening of the mitral valve).

d) NYHA Classification

NYHA classification was performed following a standard physician interview by the candidate to determine the level of functional limitation and immediately assign a functional class to the patient following NYHA classification as described below.

Table 3. New York Heart Association Classification(110)

NYHA CLASS

LIMITATIONS ON PHYSICAL ACTIVITY

SYMPTOMS WITH ORDINARY PHYSICAL ACTIVITY

STATUS AT REST

I none none comfortable

II slight symptomatic with ordinary

activities (when walking, climbing stairs etc)

comfortable

III marked symptomatic at less than ordinary levels of activity- walking short distances (20–100 m).

comfortable

IV unable to perform any activity

discomfort with any activity symptomatic at rest

e) Other Clinical Data

Socio-demographic data was obtained using a structured interviewer administered questionnaire.

Other relevant clinical data (e.g. co-morbidity, prior myocardial infarction, presumed HF aetiology) were obtained following review of the patient’s official hospital medical record.

Presumed HF aetiology was earlier determined and documented in the patient’s official hospital medical record by the attending consultant cardiologist based on clinical, laboratory, electrocardiographic and echocardiographic examination.

Hypertensive heart disease was considered present and the cause of HF if there was a combination of (a) documented hypertension (elevated blood pressure i.e. systolic BP ≥ 140 mmHg and/or diastolic BP ≥ 90 mmHg on two or more occasions during clinical examination or in the past; or on medications for hypertension); and (b) echocardiographic findings of left ventricular hypertrophy (indexed LV mass >51g/m^2.7), and dilated left atrium, a surrogate of impaired LV filling (left atrial diameter > 4.0 cm).

Ischaemic heart disease was considered present and the cause of HF when there was evidence of definite myocardial infarction from history, or if there was a long history of chronic stable angina with concurrent consistent findings on the ECG or echocardiogram.

Valvular heart disease was considered the primary cause of HF when there was echocardiographic evidence of valvular heart disease of more than moderate severity.

Dilated cardiomyopathy was diagnosed based on dilated cardiac chambers with increased left ventricular mass and normal wall thickness in the absence of documented hypertension (in the past, on medication for hypertension, or elevated blood pressure i.e. systolic BP ≥ 140 mmHg and/or diastolic BP ≥ 90 mmHg on two or more occasions).

Blood pressure was determined using a standard mercury sphygmomanometer adhering to guidelines by Pickering et al.(136) with the patient in the sitting position as stated below.

Precautions were taken to ensure patient had not exercised, smoked a cigarette or taken caffeine 30 minutes preceding the examination. An appropriately sized cuff was neatly applied to the arm and inflated to a level 20-30mmHg of mercury above which the radial pulse could not be palpated, and the level at which the pulse became palpable again noted during deflation of the cuff.

Following this, the cuff was inflated again to 20-30mmHg of mercury above aforementioned the point of pulse re-appearance and then slowly deflated at a rate of 2-3mmHg/sec while concurrently auscultating the brachial artery in the cubital fossa for the Korotkoff sounds. Systolic blood pressure was determined at the mercury level corresponding to the appearance of the first sound and diastolic pressure was determined at the point of disappearance of the sounds.

The patient’s weight and height were obtained using a standard clinical beam balance weighing scale and stadiometer respectively. Body mass index was calculated as the ratio of the patient’s weight to height squared (kg/m²)(137). Body surface area was calculated Mosteller's(138) formula

thus: √[weight (kg) x height (cm)/3600]and this was in turn used to index the cardiac output in the calculation of cardiac index.