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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 28, No 4, July/August 2017
222
AFRICA
black African patients with PE.
5
There are no studies evaluating
the incidence/prevalence of TB in HIV-infected patients with PE.
Correct diagnosis and prompt therapy can significantly
lower mortality rates of PE to between 2.5 and 8%.
1
Diagnostic
imaging of patients with clinical suspicion of PE is primarily
through CTPA, which is currently the gold standard for the
diagnosis of pulmonary emboli, as per the European Society
of Cardiology (ESC) guidelines on the management of acute
pulmonary embolism.
10
In reporting of PE, the presence and location of the clot,
with a rough visual estimate of the extent of the clot is usually
described but the magnitude can be calculated at CT by applying
a dedicated CT score.
11
The Qanadli score is an objective and
reproducible CT quantification of the severity of PE, based on
the location of the embolus and the degree of obstruction.
12
The severity of PE has an impact on management and
prognosis, and is determined by a number of factors, including
volume of the embolus, underlying cardiorespiratory function
and the degree of obstruction. Cardiac CT measurements
such as ratio of right-to-left ventricular (RV:LV) diameter have
shown good correlation with severity of PE. The ratio of RV:LV
diameter is an indicator of right ventricular strain/dysfunction.
11
The ratio of the diameter of the main pulmonary artery and the
aorta (PA:AO) has also been shown to correlate with severity of
acute PE by predicting pulmonary hypertension.
13
The prevalence and severity of PE in South African patients
undergoing CTPA requires investigation, particularly with regard
to HIV status and TB co-infection. The aim was to compare
HIV-infected and uninfected patients, regarding the presence,
distribution and extent of pulmonary emboli as found on
CTPA, and to compare findings of HIV-infected and uninfected
patients, with regard to the presence of parenchymal, pleural and
cardiovascular complications as well as TB co-infection.
Methods
This retrospective, descriptive study was undertaken at GF Jooste
Hospital, a public-sector regional hospital in Mannenberg,
Western Cape, South Africa. The Human Research Ethics
Committee of the Faculty of Health Sciences, University of
Cape Town (HREC REF: 361/2013) and the Provincial Ethics
Research Committee (RP 112/2013) provided ethical clearance.
CTPA scans spanning a two-year period from January 2011
to December 2012 from the Department of Radiology at the GF
Jooste Hospital CT scan database and CT request forms were
used for the radiological interpretation. The National Health
Laboratory Service database and patient folders were accessed
for the relevant laboratory results.
The inclusion criteria were patients referred for CTPA with
clinical suspicion of pulmonary embolus. The exclusion criteria
were patients with scans with no request form, non-retrievable
patient folders, absent clinical history regarding suspicion of PE,
and CT studies not performed as CTPA protocols.
The CTPA scans, as per standard protocol, were performed
on a six-slice Philips Brilliance CT scanner (Cleveland, Ohio,
USA) at GF Jooste Hospital. Approximately 90 ml of 370
mg/ml Omnipaque contrast was used, via an antecubital vein,
at a rate of 3.5–4.0 ml per second via an 18–20-G cannula,
using an automated power injector (Covidien Injection system,
Cincinnati, Ohio, USA).
DICOM CT data were viewed on a Siemens Syngo CT
workstation (Siemens Healthcare, Siemens Erlangen, Germany),
in the Radiology Department at Mitchell’s Plain Hospital,
using the Somaris/5 Syngo CT 2012E software with MPR
capabilities (Siemens Healthcare, Siemens Erlangen, Germany).
A consultant radiologist with more than five years’ experience
performed the reading of the CT scans according to a prescribed
data-collection sheet, using a previously externally validated
Qanadli severity scoring system.
12
Severity of the Qanadli score
was defined as a score
>
40%.
The Qanadli score or CT obstruction index, is reached by
regarding the arterial tree of each lung as having 10 segmental
arteries (three to the upper lobes, two to the middle lobe and lingula,
and five to the lower lobes) (Fig. 1). Embolus in a segmental artery
=
1 point; embolus in the most proximal arterial level
=
a value
equal to the number of segmental arteries arising distally.
Weighting factor (for residual perfusion)
=
the degree of
vascular obstruction (no thrombus
=
0; partially occlusive
thrombus
=
1; total occlusion
=
2). The maximal CT obstruction
index
=
40 for each patient (10
×
maximum weighting of 2
=
20
for each side). [Isolated sub-segmental embolus is considered
equal to a partially occluded segmental artery (value of 1)].
The percentage of vascular obstruction is calculated by
dividing the patient score by the maximal total score and by
multiplying the result by 100. Therefore, the CT obstruction
index can be expressed as:
Σ
(
n
×
d
)
_______
40
×
100
;
where
Σ
=
sum,
n
=
value of the proximal thrombus in the
pulmonary arterial tree equal to the number of segmental
branches arising distally (minimum 1; maximum 20),
d
=
degree
of obstruction (minimum 0; maximum 2). An example of how
the score is calculated from the images is provided in Fig. 2.
Cardiovascular complications were recorded. The heart was
evaluated for obvious right ventricular enlargement based on
RV:LV diameter ratio
>
1. Pulmonary artery enlargement was
evaluated by recording the diameter of the main pulmonary
artery, as well as the pulmonary artery:aorta (PA:AO) ratio
(abnormal ratio
>
1). Parenchymal complications were recorded
according to accepted radiological principles: atelectasis,
consolidation, wedge-shaped pleural-based density and ground-
glass opacity. The presence of pleural effusions was recorded
as right, left or bilateral. Additional or alternative findings
1 1
1
1
1
1
1
1 1
1
1 1
1
1
1
1
1
1 1
1
2
2
3
3
5
5
10
10
20
Fig. 1.
Schematic representation of the arterial tree of the
lung and the Qanadli score.