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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 29, No 5, September/October 2018
AFRICA
269
related cardiomyopathy.
7-9
Recently, in addition to the classical
risk factors, there is an increasing body of evidence linking lone
AF to several novel genetic, molecular and pathophysiological
mechanisms, thereby making it a ‘not-so-lone AF’.
10,11
The autonomic nervous system plays an integral role in the
onset and offset of AF. Triggers for AF include adrenergic-
mediated states such as the alcohol-associated ‘holiday heart’,
12,13
caffeine
14
and dehydration.
15
This can be contrasted with vagally-
mediated states such as sleep, postprandial and post-exercise
situations that tend to be triggers for AF in tall, lean and
physically fit middle-aged males involved in endurance sports.
16-19
On the other hand, the pathophysiology of AF noted in
overweight patients has been linked to the inflammatory state
associated with the metabolic syndrome.
20,21
There are several
subsets of lone AF, including familial AF
22-24
and AF associated
with conduction system disorders, such as sick sinus syndrome
(SSS) or the bradycardia–tachycardia syndrome.
25
In the near
future it is hoped that elucidating the aetiology of lone AF
will lead to a more tailored and therapeutic approach to the
management of AF.
To the best of our knowledge, there are no studies to describe
the clinical characteristics and outcomes of patients with lone
AF in Africa and other developing regions of the world. The
purpose of this study was to describe the clinical characteristics
and outcomes of patients with lone AF attending Groote Schuur
Hospital (GSH) in Cape Town.
Methods
This study was a retrospective, descriptive study of the clinical
characteristics and outcomes of patients with lone AF who
attended GSH from January 1992 to December 2006. All
medical records of patients with AF over this 15-year period
were reviewed to identify those with lone AF. The patients had
presented to GSH Emergency Department, had already been
attending the Cardiac Clinic or had been referred to the Cardiac
Clinic from day hospitals or private medical institutions. The
medical records were reviewed for findings of their clinical
examinations, electrocardiograms, echocardiograms, chest
X-rays, laboratory results and, if clinically indicated, the 24-hour
Holter, exercise stress test and coronary angiograms.
Our inclusion and exclusion criteria were comparable to the
Mayo Clinic series,
2,3
the exception being the subset of patients
who had AF and concomitant SSS, which we included in the
study. Patients with any of the following at the initial diagnosis
of AF were excluded from the study: hypertension treated with
medication, or systolic blood pressure
>
160 mmHg or diastolic
blood pressure
>
90mmHg on two or more consecutive occasions;
coronary artery disease according to clinical or laboratory data;
hyperthyroidism as per laboratory data; left bundle branch
block or pre-excitation on electrocardiogram; valvular heart
disease; chronic obstructive airway disease; idiopathic dilated
cardiomyopathy; and patients who developed atrial fibrillation in
the context of an acute medical or surgical condition.
We included patients with systolic blood pressures recorded
between 140 and 160 mmHg or diastolic pressures between 80
and 90 mmHg on fewer than two consecutive occasions, as long
as there was no evidence of left ventricular hypertrophy on the
electrocardiogram or echocardiogram; elderly patients over
60 years, to assess their clinical characteristics and outcomes;
patients with documented AF and concomitant flutter or SSS;
and those with documented echocardiograms. More inclusion
criteria than those used in previous studies were chosen, to
investigate a population without any evidence of organic heart
disease at the first presentation, which may reflect what is
commonly found in clinical practice.
Although the Mayo Clinic series
2,3
did not include patients
with AF/SSS, a subsequent study
25
did include these subjects.
Patients who had symptoms and signs of heart failure and/
or a dilated left ventricle on echocardiogram in the absence of
classical risk factors or metabolic causes and with a normal QRS
duration and morphology at the initial diagnosis of AF (normal
apart from the AF) were included only if they demonstrated a
subsequent improvement of their symptoms and signs of heart
failure and left ventricular function on repeat echocardiogram,
once their rate was controlled.
The following baseline characteristics were entered into a
data-entry form: age at diagnosis, follow-up time, gender and race
(white, black or mixed race). The height and weight of patients
were noted and a body mass index of
<
25 kg/m
2
was considered
normal and
>
25 kg/m
2
was considered to be overweight. The
type of AF (paroxysmal or persistent) and the number of
patients who progressed from paroxysmal to permanent AF,
and subsets of patients with atrial flutter and conduction system
disease were noted. Family history was reviewed. Presenting
symptoms, their duration and possible triggering factors were
noted. Mortality rate and complications, including tachycardia-
related cardiomyopathy and thromboembolism were recorded.
Therapy instituted to control or terminate the AF was
reviewed. The indications and therapy chosen for prevention of
thromboembolism were reviewed. The number of patients who
developed bleeding complications while on anticoagulants was
also reviewed.
Baseline descriptive statistics were expressed as means and
range for continuous variables. Counts with percentages were
used for categorical variables.
Results
Of the 289 patients with AF in the period under review, 42 were
identified as having lone AF (15% of all patients with AF).
The mean follow-up time of these patients was 5.8 years. Males
comprised 57% (
n
=
24), and 43% (
n
=
18) were females. The
mean age of the males at diagnosis was 46 years with no males
being older than 60 years. The mean age of the females was 62.4
years; 55% (
n
=
10) were less than 65 years of age at the time of
diagnosis and they had a mean age of 45 years. The remaining
45% (
n
=
8) were older than 65 years.
The racial composition was 50% (
n
=
21) white, 36% (
n
=
15)
mixed race, 7% (
n
=
3) black and 7% (
n
=
3) not having their race
specified. Forty three per cent (
n
=
18) of patients were of normal
weight, 36% (
n
=
15) were overweight and 21% (
n
=
9) were not
specified.
At the time of diagnosis, 50% (
n
=
21) of the patients had
paroxysmal AF, 29% (
n
=
12) had persistent AF and 12% (
n
=
5)
progressed from paroxysmal to permanent AF over the follow-
up period. Subsets of AF included those with concomitant atrial
flutter (17%) (
n
=
7) and those with SSS (21%) (
n
=
9). A family
history of AF or palpitations was poorly documented in the
medical records.