CARDIOVASCULAR JOURNAL OF AFRICA • Vol 23, No 3, April 2012
140
AFRICA
features may be useful for differentiating between DCMO and
ischaemic CMO.
7
DCMO was characterised by higher RV
6
voltages and higher RV
6
/R
max
(leads I, II or III) ratios. The authors
stated that RV
6
voltage is determined by the distance from the
LV to the RV
6
chest lead and is a marker of LV dilatation. Limb
voltages in leads I, II, III are not affected by the distance of
the LV to the chest wall and are markers of voltage-producing
cardiac mass. In patients with DCMO, replacement fibrosis or
infiltrates reduce R-wave voltages in these limb leads.
When we compared TIC patients with DCMO patients, there
were no significant differences in RV
6
voltages and RV
6
/R
max
ratios between the two groups. By inference, RV
6
voltages and
RV
6
/R
max
ratios may be useful parameters to distinguish DCMO
or TIC from ischaemic CMO but not useful to distinguish
between DCMO and TIC.
A previous echocardiographic study by Jeong
et al
. showed
that TIC patients tended to have smaller LV mass indices, volume
dimensions and LV dimensions compared to patients with
DCMO.
8
They suggested that a LVIDd
≤
6.1 cm at presentation
predictedTIC with a sensitivity of 100% and a specificity of 71%.
Our study confirmed that pure TIC patients had significantly
smaller LVIDd, LVIDs and LA dimensions when compared to
DCMO patients at presentation. However, in contrast to their
study, we could not confirm a LVIDd dimension that predicted
TIC with a high degree of sensitivity and specificity.
In our study, we noted in four patients with AF (
n
= 2)
and AT (
n
= 2) that although pharmacological rate control
was suboptimal (according to the AFFIRM trial targets), LV
function improved in all patients at a slower rate over a year.
In contrast, we noticed that in patients who had AVNA and
PPM implanted for failed pharmacological rate control, the LV
function generally had maximal improvement by three to six
months. These findings suggest that although strict rate control
is required for optimal LV recovery, lenient rate control may still
result in improvement.
In the RACE II trial,
9
a randomised trial of optimal heart
rate control versus lenient heart rate control in patients with
permanent AF, researchers found no difference between the two
strategies. However, TIC patients were under-represented in this
trial. Currently, it seems that TIC patients may benefit from
stricter heart rate control.
A previous study showed that although the LVEF improved
significantly with control of the tachycardia, LV dimensions
and volumes remained significantly elevated when compared
to control patients late after control of the tachycardia.
10
When
Fig. 1. Group A (early recovery)
70
60
50
40
30
20
10
0
LVEF (%)
Presentation 3–6 months Last available
Patient 24
Patient 12
Patient 16
Patient 30
Patient 21
Patient 11
Patient 19
Fig. 2. Group B (late recovery)
70
60
50
40
30
20
10
0
LVEF (%)
Presentation 6–12 months Last available
Patient 33
Patient 22
Patient 1
Patient 4
Patient 15
Patient 17
TABLE 3. PRE- AND POST-TREATMENT ECHOCARDIOGRAPHIC PARAMETERS OF PUREAND IMPURE TIC
Pure TIC
at presentation
(
n
=
33)
Pure TIC
post-treatment
(
n
= 33)
p
-value
#
Impure TIC
at presentation
(
n
=
12)
Impure TIC
post-treatment
(
n
=
12)
p
-value
#
LVEF (%)
32.4
±
9.5
53.2
±
10.5
<
0.001
29.2
±
10.0
55.0
±
9.9
<
0.001
LVIDd (cm)
5.7
±
0.7
5.3
±
0.8
0.004
5.7
±
1.0
5.5
±
0.8
0.86
LVIDs (cm)
4.8
±
0.8
3.6 (2.2
-
4.6)
0.001
¶
4.8
±
0.8
3.8 (2.7
-
4.4)
0.04
¶
LA size (cm)
4.2
±
1.0
4.1
±
0.8
0.19
4.81
±
1.5
4.7
±
1.3
0.92
#
Student’s
t
-test,
¶
Mann-Whitney test.
Time
Time
TABLE 4. PURE TIC PATIENTSWITH LENIENT HEART
RATE CONTROLAND LATE IMPROVEMENT OF LEFT
VENTRICULAR FUNCTION
Patient nunber Average resting heart rate on treatment (beats/min)
Patient 33
111
Patient 1
92
Patient 15
100
Patient 4
96
TABLE 5. POST-TREATMENT ECHOCARDIOGRAPHIC
PARAMETERS OF PATIENTSWITH PURE TICWITH
COMPLETE LV IMPROVEMENT, AND NORMAL
CONTROLS MATCHED FORAGEAND LVEF
Pure TIC group
(
n
=
17)
Normal controls
(
n
=
17)
p
-value
#
LVEF (%)
58.9
±
8.9
60.4
±
9.2
0.5
LVIDd (cm)
5.2
±
0.6
4.8
±
0.5
0.06
LVIDs (cm)
3.5
±
0.5
3.2
±
0.6
0.18
LA size (cm)
4.2
±
0.7
3.9
±
0.5
0.19
#
Student’s
t
-test.
