17 / 68
CARDIOVASCULAR JOURNAL OF AFRICA • Volume 26, No 3, May/June 2015
AFRICA
115
mechanical function have recently been identified as a potential
indicator of cardiac disease and arrhythmias.
14,15
Prolongation of
atrial electromechanical interval and impaired LA mechanical
function are associated with adverse clinical events, including
atrial fibrillation, stroke, diastolic dysfunction and left ventricular
failure.
16,17
LA mechanical function and atrial conduction abnormalities
have not been investigated in MP users and smokers. Therefore,
our study was planned to evaluate whether MP damages
intra- and inter-atrial conduction intervals and LA mechanical
function as much as cigarette smoking.
Methods
A total of 150 chronic MP users (50 males, mean age 32.5
±
5.4
years), cigarette smokers (50 males, mean age 32.1
±
6.0 years)
and controls (50 males, mean age 30.1
±
5.8 years) who referred
to various out-patient departments (cardiology clinic, public
health clinic, internal medicine clinic, cardiovascular surgery
clinic) and were matched for age and gender, were included in
the study. A medical history was taken and detailed physical
examinations were performed on all subjects.
The inclusion criterion was using MP for at least three years.
A package of MP was considered sufficient to provide use of the
powder for 20 occasions. Duration and frequency of MP use,
duration of cigarette smoking and number of cigarettes smoked
throughout the day were recorded. The entire study population’s
demographic characteristics, biochemical parameters, lipid
values and ECGs were obtained.
Exclusion criteria were: history of coronary artery disease,
arterial hypertension, hypercholesterolaemia, diabetes mellitus,
primary cardiomyopathy, valvular heart disease, left ventricular
ejection fraction (LVEF) less than 50%, bundle branch block,
LV wall motion abnormality, renal failure, atrioventricular
conduction abnormalities on electrocardiogram, thyroid
dysfunction, anaemia, electrolyte imbalance, pulmonary disease,
and poor-quality echocardiographic and electrocardiographic
imaging.
All patients were in sinus rhythm, and none was taking
medication such as anti-arrhythmics, antihistamines, tricyclic
antidepressants and antipsychotics. Written informed consent
was obtained from each subject. The institutional ethics
committee approved the study protocol.
Echocardiography
In this study, a Vingmed Vivid Seven Pro, Doppler
echocardiographic (GE Ultrasound, Horten, Norway) unit
with a 2–4 MHz FPA probe was used. Tissue Doppler (TDI)
echocardiography was performed with a transducer frequency of
3.5–4.0 MHz, adjusting the spectral pulsed Doppler signal filters
to obtain the Nyquist limit of 15–20 cm/s, and using the minimal
optimal gain setting. The monitor sweep speed was set at 50–100
mm/s to optimise the spectral display of myocardial velocities.
A 12-lead electrocardiogram recording obtained from the
same derivation (DII derivation) was recorded continuously
during the echocardiographic examination in all study
subjects. Two-dimensional, M-mode, pulsed and colour-flow
Doppler echocardiographic examinations were performed by a
cardiologist who was blinded to the clinical details and findings
of other examinations of each subject and control. During
echocardiography, continuous one-lead electrocardiographic
recordings were obtained. LA volumetric parameters were
measured by transthoracic echocardiography in the left lateral
position, in parasternal long axis, apical four chambers and two
chambers. M-mode measurements and conventional Doppler
echocardiographic examinations were performed according to
the guidelines of the American Society of Echocardiography.
18
All measurements were recorded as averages of three cardiac
cycles. LA dimension, LV end-systolic and end-diastolic
dimensions, diastolic ventricular septal thickness, and diastolic
LV posterior wall thickness were measured in the parasternal
long-axis view. LVEF was estimated using the Simpson’s rule.
All echocardiographic examinations were performed by the same
cardiologist.
LA volumes were measured echocardiographically using
the biplane area–length method in apical four-chamber and
two-chamber views. LA maximal volume (V
max
) was recorded
at the onset of mitral opening, LA minimal volume (V
min
) was
recorded at the onset of mitral closure, and LA pre-systolic
volume (V
p
) was recorded at the beginning of the atrial systole
(P wave on ECG). All volume measurements were corrected to
body surface area, expressed as ml/m
2
and the following LA
emptying function parameters were calculated:
19
LA passive emptying volume (LAPEV)
=
V
max
– V
p
LA passive emptying fraction (LAPEF)
=
LAPEV
_______
V
max
LA active emptying volume (LAAEV)
=
V
p
– V
min
LA active emptying fraction (LAAEF)
=
LAAEV
_______
V
p
LA total emptying volume (LATEV)
=
V
max
– V
min
LA total emptying fraction (LATEF)
=
LATEV
_______
V
max
All measurements were repeated during three consecutive heart
beats and the average of three consecutive measurements was
obtained.
Atrial electromechanical coupling measurements
For atrial electromechanical intervals in the apical four-chamber
view, the pulsed Doppler sample volume was placed at the level
of the LV lateral mitral annulus, septal mitral annulus and right
ventricular (RV) tricuspid annulus. Atrial electromechanical
intervals (PA) were measured as the time interval between the
onset of the P wave on the electrocardiogram and the beginning
of the late diastolic A wave at the lateral mitral annulus (lateral
PA), septal mitral annulus (septal PA), and RV tricuspid annulus
(RV PA). The difference between lateral PA and RV PA (lateral
PA–RV PA) was defined as inter-atrial dyssynchrony, and the
difference between septal PA and RV PA (septal PA–RV PA) as
intra-atrial dyssynchrony.
20
Reproducibility
Intra-observer variability was assessed in 20 subjects selected
randomly from the study groups by repeating the measurements