CARDIOVASCULAR JOURNAL OF AFRICA • Vol 21, No 2, March/April 2010
AFRICA
95
heart rates, and SBP and DBP at rest (Table 2). G2 patients had a
higher mean duration of diabetes than G1 (69.0
±
9.48 vs 18.7
±
8.7 months;
p
=
0.007). The patients’ characteristics at rest were
not statistically significantly different (Table 2).
As shown in Table 3, peak systolic blood pressure was signifi-
cantly higher in G2 subjects than in G1 (213.6
±
20.1 vs 200.0
±
15.3 mmHg;
p
=
0.04). The difference between resting systolic
and peak systolic blood pressure (
Δ
SBP) as well as resting pulse
pressure and pulse pressure during exercise (
Δ
PP) followed a
similar trend to that of peak systolic blood pressure. Exercise
capacity in G2 subjects was significantly lower than in G1 by
12.94% (7.4
±
1.1 vs 8.5
±
1.5 METs;
p
=
0.042). Although, there
was no statistically significant difference between the LV mass
index in the two groups, G2 subjects had significantly higher
relative wall thicknesses than those in G1 (0.53
±
0.03 vs 0.41
±
0.04;
p
<
0.001) (Table 4).
Discussion
The relationship of blood pressure response to exercise and end-
organ damage in hypertensive subjects is not clear. Studies on
this subject in diabetics are few, especially among blacks, who
unfortunately are at higher risk of developing cardiovascular-
related complications than their Caucasian counterparts.
15
This
study is the first in Nigeria to assess the relationship between
blood pressure response to exercise and abnormal LV geometry.
In this study, gender, age and BMI were comparable among
the patients with normal LV geometry and those with LV concen-
tric remodelling. The longer duration of diabetes in patients with
concentric LV remodelling supports the earlier assertion that
the longer the duration of diabetes, the more the likelihood that
the patient will develop cardiovascular complications. This was
despite the fact that short-term (FBG, two-hour post-prandial
blood glucose) glycaemic control was similar in both groups
in this study, suggesting that blood pressure response during
exercise may not have been much influenced by blood glucose
exposure.
It has been suggested that blood pressure response may be
related to blood glucose control.
16
Marfella
et al
. reported that
in the resting state, the presence of hyperglycaemia led to an
increase in SBP and DBP independently of endogenous insulin
in 20 patients with type 2 diabetes. A reduced availability of
nitric oxide was suggested as a possible explanation.
16
In our study, the peak systolic blood pressure during exercise
was significantly higher in patients with LV concentric remodel-
ling than in those with normal LV geometry. This however was
not the case with peak diastolic blood pressure. This was reflect-
ed in the significant change in pulse pressure (
Δ
PP) observed
during exercise. Pulse pressure provides a crude guide to stiff-
ness of the large conduit arteries.
17
Physiological parameters
related to blood pressure regulation and potential contributors to
reduced exercise capacity in type 2 diabetic individuals include
reduced LV systolic volume, altered myocardial and diastolic
functions and increased arterial stiffness.
5,18
The elevated peak
exercise SBP observed in patients with concentric left ventricular
remodelling in this study was probably partly associated with
arterial stiffness, as reflected by the higher
Δ
PP.
5,6
Exercise capacity was also reduced in patients with LV
concentric hypertrophy in our study. This may provide addi-
tional explanation for reduced exercise tolerance in normoten-
sive diabetes patients. It has been suggested that the voltage
on the ECG of left ventricular hypertrophy may be an early
marker of impaired exercise capacity.
19
Previous studies have
shown that left ventricular hypertrophy independently predicted
reduced exercise capacity.
20
This study has shown that type 2
diabetic patients with increased peak systolic blood pressure had
increased arterial stiffness, higher LVMI, abnormal LV geometry
and reduced exercise capacity.
Conclusion
Normotensive diabetics with concentric left ventricular remodel-
ling have increased systolic blood pressure reactivity to exercise.
It is probable, as suggested in earlier studies, that increased blood
pressure reactivity to exercise is an indicator of target-organ
damage, especially in normotensive diabetics.
References
Gottdierer JS, Brown J, Zoltick J, Fletcher RD. Left ventricular hyper-
1.
trophy in men with normal blood pressure: relation to exaggerated blood
pressure response to exercise.
Ann Intern Med
1990;
112
: 161–166.
Al’Absi M, Devereux RB, Lewis CE,
2.
et al
. Blood pressure responses to
acute stress and left ventricular mass.
Am J Cardiol
2002;
89
: 536–540.
Rostrup M, Smith G, Bjo¨ rnstad H, Westheim A, Stokland O, Eide
3.
I. Left ventricular mass and cardiovascular reactivity in young men.
Hypertension
1994;
23
(Suppl I): I168–I171.
Stewart KJ, Sung J, Silber HA,
4.
et al
. Exaggerated exercise blood
pressure is related to impaired endothelial vasodilator function.
Am J
Hypertens
2004;
17
(4): 314–320.
Devereux RB, Roman MJ, Paranicas M,
5.
et al
. Impact of diabetes on
cardiac structure and function: the Strong Heart Study.
Circulation
2000;
101
: 2271–2276.
TABLE 3. EXERCISE-INDUCED HAEMODYNAMIC
FACTORS
Parameters
Normal LV
geometry
(
n
=
19)
Concentric
LV remodel-
ling (
n
=
11)
p-value
(Student’s
t-test)
pHR (bpm)
167.8
±
10.9 162.8
±
21.7 0.405
pDBP (mmHg)
94.2
±
7.7 98.2
±
11.7 0.270
pSBP (mmHg)
200.0
±
15.3 213.6
±
20.1
0.045
Δ
HR (bpm)
75.7
±
18.4 72.7
±
28.1 0.725
Δ
DBP (mmHg)
21.5
±
14.1 24.0
±
13.3 0.596
Δ
SBP (mmHg)
81.5
±
14.1 98.9
±
20.1 0.010
Δ
PP (mmHg)
105.8
±
9.6 115.5
±
11.3 0.019
HR reserve
0.97
±
0.16 0.87
±
0.03 0.222
Exercise capacity (METs)
8.5
±
1.5
7.4
±
1.1 0.042
Statistical significance at
p
<
0.05
Values are expressed as mean
±
SD.
TABLE 4. ECHOCARDIOGRAPHIC PARAMETERS OF G1
AND G2 SUBJECTS
Parameters
Normal
LV geometry
(
n
=
19)
Concentric
LV remodelling
(
n
=
11)
p
-value
(Student’s
t-test)
LVMI (g/m
2
)
81.1
±
13.4
88.9
±
21.8
0.233
IVST (mm)
9.8
±
1.2
11.1
±
1.3
0.010
PWT (mm)
9.0
±
1.3
10.9
±
1.1
<
0.001
RWT
0.41
±
0.04
0.53
±
0.03
<
0.001
Statistical significance at
p
<
0.05
Values are expressed as mean
±
SD.
