(Circulation. 2001;103:2949.)
© 2001 American Heart Association, Inc.
Clinical Investigation and Reports |
From the Centre de Médecine Préventive Cardiovasculaire, Hôpital Broussais, Paris, France.
Correspondence to Alain Simon, Centre de Médecine Préventive Cardiovasculaire, Hôpital Broussais, 96 Rue Didot, 75674 Paris, France. E-mail alain.simon{at}brs.ap-hop-paris.fr
| Abstract |
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Methods and ResultsThis study, ancillary to the
International Nifedipine GITS Study: Intervention as a Goal
in Hypertension Treatment (INSIGHT), involved nifedipine 30
mg or co-amilozide (hydrochlorothiazide 25 mg and
amiloride 2.5 mg) with optional subsequent titration. Among 439
randomized hypertensive patients, 324 had
1 year of follow-up
(intent-to-treat group), and 242 completed follow-up
(until-end-of-study group). Ultrasonography was performed at baseline,
4 months later, and then every year. Central computerized reading
provided far-wall IMT, diameter, and cross-sectional area IMT
(CSA-IMT). The primary outcome was IMT progression rate (slope of
IMT-time regression). Secondary outcomes were changes from baseline
(
) in IMT, diameter, and CSA-IMT. In the until-end-of-study
population, between-treatment differences existed in IMT progression
rate (P=0.002),
IMT
(P=0.001), and
CSA-IMT
(P=0.006), because IMT
progressed on co-amilozide but not on nifedipine. In the
intent-to-treat population, treatment differences existed in
IMT
(P=0.004) and
CSA-IMT
(P=0.04) but not in IMT
progression rate (P=0.09).
Patients with
2, 3, or 4 years of follow-up showed treatment
differences in IMT progression rate
(P=0.04, 0.004, 0.007,
respectively),
IMT
(P=0.005, 0.001, 0.005), and
CSA-IMT (P=0.025, 0.013,
0.015). Diameter decreased more on co-amilozide than on
nifedipine in the intent-to-treat population
(P<0.05), whereas blood
pressure decreased similarly on both
treatments.
ConclusionsA difference in early carotid wall changes is shown between 2 equally effective antihypertensive treatments.
Key Words: carotid arteries hypertrophy hypertension drugs
| Introduction |
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| Methods |
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1 of the following risk
factors: smoking, hypercholesterolemia,
diabetes mellitus, left ventricular
hypertrophy, history of cardiovascular
disease, family history of myocardial infarction, and proteinuria.
Patients with secondary or malignant hypertension, stroke, or
myocardial infarction within the previous 12 months were not eligible.
Of 469 subjects who met enrollment criteria, 439 fulfilled the blood
pressure criteria to be randomized. Randomization was done centrally,
including all centers participating, and respecting the randomization
criteria of INSIGHT,12
taking into account age, sex, risk factors, and inclusion in the
present study. Among randomized subjects, 324 had
1 year of
follow-up and 3 serial IMT measurements, thus allowing IMT progression
rate to be estimated (intent-to-treat population,
Figure 1
5 valid IMT measurements (until-end-of-study
population,
Figure 1
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Study Treatment
After 1 month of treatment with placebo (baseline),
patients were randomized in a double-blind fashion to receive
nifedipine gastrointestinal-transport-system (GITS) (30 mg)
or co-amilozide (amiloride 2.5 mg and
hydrochlorothiazide 25 mg) (monotherapy dose 1).
Medication titration could subsequently be adapted to obtain blood
pressure of 140/90 mm Hg. Three titration levels were performed:
(1) monotherapy dose 2, ie, twice monotherapy dose 1; (2) bitherapy,
adding atenolol 25 or 50 mg (or enalapril 5 or 10 mg if atenolol was
contraindicated); and (3) tritherapy, adding to the bitherapy any other
antihypertensive drug exclusive of calcium antagonists and
diuretics. Duration of follow-up of the until-end-of-study
population was on average 48 months, range 37 to 53 months
(Figure 1
).
Carotid Ultrasonography
Investigation was performed in 13 centers with
high-resolution imagers,11
with 5- to 10-MHz probes, by sonographers who were vascular physicians
trained in IMT measurement (Appendix). Baseline ultrasound detection of
plaque was performed in both carotid arteries. The presence of plaque,
defined as a focal echogenic structure encroaching into the lumen with
a thickness of 50% of that of the surrounding walls, was positive if
1 plaques were found.13
Longitudinal scans of the right common carotid artery, 3 cm before the
bifurcation (flow divider), were performed at baseline, 4 months after
randomization, and every 1 year for the duration of follow-up. This
segment, close and parallel to the skin surface, is easy to image, with
a lumen-intima interface regular and parallel to the adventitia. The
same sonographer performed all scans of each patient throughout the
study. Minimum gain was adjusted to visualize the lumen-intimal
and media-adventitial interfaces defining IMT in the far wall along
1
cm of length. Then, the vessel image was frozen in
telediastole by ECG R-triggering and transferred to a
computer (Apple Macintosh) with a program of
image acquisition (Iôtec, IôDP). This program allowed the
image to be digitized and
stored.2 6 The
computerized generation of the anatomic situation (mask) of the
investigated area at baseline allowed superimposition of the real-time
echographic image under treatment and the mask of the first
investigation to improve the repeated identification of the carotid
sector.2 6
Central Reading
Images stored on disk were sent to the reading center
for off-line analysis by 1 reader blinded to treatment
assignment. Far-wall IMT was measured with an automated computerized
edge-detection program (Iô, IôDP) on the basis of gray-level
density and tissue-recognition
algorithms,2 3 6
locating echoes arising from IMT interfaces and calculating their
distance every 100 µm along
1 cm length. The program also located
the leading edges of far- and near-wall blood-intima interfaces
defining lumen diameter (D) and calculated their distance along the
same length as IMT.6 The
cross-sectional area of IMT (CSA-IMT) was calculated as
follows14 :
xIMTx(IMT+D).
Quality Control Program
Centers were visited before the study and annually
until its termination, with examination of a tissue-equivalent phantom
allowing the initial value of the settings to be maintained throughout
the study. Because the same phantom was examined, all units and
transducers were matched between centers. Images were read after
termination of the study, but the reader was not blind to the sequence
time of the tracings. Images were read on a field of measure that had
the same situation, with regard to the artery and surrounding
structure, at baseline and during treatment and was reader-independent
thanks to the automated program. Reproducibility of measurement was
assessed during the placebo period in 39 random subjects; the mean
absolute difference between repeat measures of IMT at 15-day intervals
by the same sonographer was 0.026 mm, in agreement with the
precision obtained on the basis of previous
studies.5 6
Study Outcomes
Primary outcome was the IMT progression rate
estimated in each patient as the slope of the least-squares regression
line relating IMT to the time since baseline ultrasonography throughout
the follow-up. A minimum of 3 serial IMT assessments (ie, 1 year of
follow-up) was required for obtaining a valid estimation of slope. In
the until-end-of-study population, the slope was estimated from IMT
measurements (
5) during the entire follow-up period. In the
intent-to-treat population, the slope was estimated independently of
whether the patient completed the planned follow-up. To analyze
how the slope may change as a function of follow-up duration,
intention-to-treat analysis was performed in patients who were
2 years,
3 years, or
4 years on treatment. Secondary outcomes
consisted of absolute change from baseline (last value under
treatment minus baseline value) in IMT, CSA-IMT, and diameter.
They were determined in the until-end-of-study population, in the
intent-to-treat population independently of whether the patient
completed the planned follow-up, and in patients with
2, 3, or 4
years on treatment.
Statistical Issues
Sample size was chosen to provide 90% power (with
2P=0.05) to detect a 0.0375-mm
difference in change from baseline in IMT after 3 years between
treatment groups, with an expected SD of the change of 0.105
mm.11 Accordingly, 165
patients were required per group, ie, a total of 330, which was
increased by
30% (430 patients) to take the withdrawals into
account. It was decided before unblinding that the primary
analysis would be done in the until-end-of-study population
because the precision of the primary outcome was greater than in
the intent-to-treat population. All patients of the until-end-of-study
population had
5 valid IMT assessments, whereas some patients in the
intent-to-treat population had only 3 IMT assessments.
Betweentreatment group differences in parameters were
tested with Students t test
for independent groups. Withintreatment group differences in
parameters from zero were tested with a paired
t test.
Multivariate analysis was used to test
betweentreatment group differences after adjustment for (1)
ultrasound center; (2) baseline covariates including age, sex, body
mass index, associated risk factors, ultrasound plaque, and
diastolic pressure; and (3) absolute change in
diastolic pressure (last value under treatment minus
baseline value). Statistical analysis was performed with an
SAS software package (V12) for Windows operating
system.
| Results |
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IMT Progression Rate
Until-End-of-Study Population
The IMT progression rate differed between treatment
groups before (P=0.002) and
after (P=0.003) adjustment for
center, baseline covariates, and diastolic pressure change.
Within-group comparison to zero showed that IMT progressed
significantly on co-amilozide
(P<0.001) but not on
nifedipine
(Table 3
).
|
Intent-to-Treat Population
In the whole intent-to treat population, the difference
in IMT progression rate between treatments did not reach statistical
significance (P=0.09)
(Table 3
), but in the subgroup of individuals who received
only the randomization medications (monotherapy dose 1 or 2), the
difference between nifedipine and co-amilozide was
significant (-0.0015±0.0033 versus 0.0078±0.0026 mm/y,
P<0.05). In patients with
2,
3, or
4 years of follow-up, the difference in IMT progression rate
was significant between treatments before adjustment
(P=0.04, 0.004, 0.007,
respectively) and after adjustment
(P=0.04, 0.003, 0.010)
(Table 3
). In the subgroup of patients receiving the
randomization medications (monotherapy), the difference between
nifedipine and co-amilozide was also significant in
subjects with
2 years of follow-up (-0.0016±0.0026 versus
0.0065±0.0022 mm/y,
P<0.05),
3 years of
follow-up (-0.0027±0.0026 versus 0.0065±0.0023 mm/y,
P<0.01), or
4 years of
follow-up (-0.0031±0.0028 versus 0.0063±0.0022 mm/y,
P<0.01). Within-group
comparison to zero showed that IMT progressed significantly on
co-amilozide in the whole intent-to-treat population
(P<0.05) and in patients with
2, 3, or 4 years of follow-up
(P<0.01,
P<0.001,
P<0.001) but did not on
nifedipine
(Table 3
).
Changes From Baseline in IMT and
CSA-IMT
Until-End-of-Study Population
Changes in IMT and CSA-IMT differed between treatments
before adjustment (P=0.001,
P=0.006) and after adjustment
(P=0.002,
P=0.005)
(Table 4
). Within-group comparison to zero showed that IMT
and CSA-IMT increased on co-amilozide
(P<0.001) but not on
nifedipine
(Table 4
).
|
Intent-to-Treat Population
In the whole intent-to-treat population, changes in IMT
and CSA-IMT differed between treatments before adjustment
(P=0.004,
P=0.037) and after adjustment
(P=0.008,
P=0.036)
(Table 4
). Changes in IMT and CSA-IMT differed between
treatments in patients with
2 years
(P=0.005,
P=0.025), 3 years
(P=0.001,
P=0.013), or 4 years
(P=0.005,
P=0.015) of follow-up, and such
differences persisted after adjustment
(Table 4
). Within-group comparisons showed that IMT
increased from baseline on co-amilozide in the whole intent-to-treat
population and in patients with
2, 3, or 4 years of follow-up
(P<0.001) but did not on
nifedipine
(Table 4
); CSA-IMT increased from baseline on co-amilozide
only in patients with
3 or 4 years of follow-up
(P<0.05) but did not on
nifedipine
(Table 4
).
Change in Diameter From Baseline
Until-End-of-Study Population
Diameter decreased on nifedipine
(P<0.05) and co-amilozide
(P<0.001), and diameter
changes did not differ between the 2 treatments
(Figure 4
).
|
Intent-to-Treat Population
Diameter decreased on co-amilozide in the whole
intent-to-treat population
(P<0.001) and in patients with
different duration of follow-up
(P<0.001) but did not change
on nifedipine except in patients with
4 years of
follow-up (P<0.05)
(Figure 4
). Diameter changes were different between drugs in
the whole intent-to-treat population
(P<0.05) and in patients with
3 years of follow-up
(P<0.05) but not in patients
with
1 or
4 years of follow-up
(Figure 4
).
| Discussion |
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2, 3, or 4 years of follow-up, significant treatment differences
existed in IMT progression rate as well as in changes in IMT and
CSA-IMT. Thus, the nonsignificant treatment difference in IMT
progression rate of the intent-to-treat population was due to patients
who were only 1 year on treatment. This follow-up is not sufficiently
long to determine IMT progression rate with good precision, especially
because measurement at 4 months was taken too early. Different
treatment effects on IMT result because IMT progressed on co-amilozide,
whereas it did not on nifedipine. The possibility that
atenolol and hydrochlorothiazide both have negative
effects on IMT progression (ie, by increasing insulin resistance) has
been excluded by the analysis of those individuals who received
only the randomization medications (monotherapy) and who exhibited the
same different drug effects on IMT progression rate as the whole
population. Several points of these findings have to be considered. First, previous trials (especially MIDAS and VHAS9 10 ) have shown beneficial effects of calcium antagonists on carotid IMT compared with diuretic agents. The MIDAS study concluded that there was no difference in IMT effects of isradipine and hydrochlorothiazide, because there was no divergence in the IMT progression slope between treatments,9 but when data were analyzed as IMT change from baseline, differences existed favoring isradipine.9 The VHAS study found a greater effect of verapamil than chlorthalidone on IMT progression when the slope of IMT change was corrected by the initial IMT value.10 The VHAS analysis, however, took into account thicker lesions in the bifurcation and internal carotid artery; this may explain why we found progression with diuretics and no change with nifedipine but VHAS found regression with both drugs and greater regression with verapamil.10 Another point is the physiological meaning of the treatment effects on IMT change. This latter may be a result of medial hypertrophy or intimal thickening reflecting early atherosclerosis.15 We cannot distinguish between these mechanisms, because ultrasonography does not measure medial and intimal thickness separately. Thus, our interpretation is dependent on indirect arguments. Those for medial hypertrophy are that IMT has been measured in distal common carotid artery free of atherosclerotic plaque and that medial hypertrophy is specifically related to hypertension.1 Conversely, the implication of atherogenesis is supported (1) by the fact that IMT, even measured locally, may reflect a widespread atherosclerosis-related phenomenon (in particular in elderly high-risk patients)16 and (2) by previously demonstrated antiatherogenic properties of calcium antagonists.17 Arguments in favor of an atherogenic nature of IMT change would have been strengthened if investigation had been extended to plaques. Although the presence of plaque was analyzed at baseline as a part of risk stratification, the thickness of plaque and its change throughout the study were not assessed because our computerized measurement was inappropriate. Thus, our work does not permit us to assess whether the effects of treatments on IMT may reflect different effects on vascular hypertrophy rather than on atherosclerosis. A third point to discuss is the meaning of different effects on carotid IMT when the effects of 2 treatments on mortality-morbidity are equal in INSIGHT,12 as well as in our patients, with limitations due to the smallness of the sample. An explanation may be that early wall change, such as IMT, cannot predict relatively short-term occurrence of complications. In consideration of the well-recognized predictive value of IMT,16 the beneficial effects of nifedipine on IMT may announce a smaller incidence of complications in the longer term. The last findings are diameter changes that may influence wall thickness. They occur at the beginning of treatment (when pressure is reduced) and remain relatively stable without progression as the IMT changes, suggesting that they did not confound IMT progression over time. Furthermore, the decrease in diameter is more pronounced on co-amilozide than on nifedipine, probably because the latter vasodilates the carotid artery18 and counteracts the passive diameter decrease due to pressure lowering. Such a difference, however, disappears in patients with the longest follow-up.
In summary, we report clear-cut differences in early carotid wall changes between 2 equally effective antihypertensive strategies. The general applicability of the findings may be limited by the facts that our population was small and that the sample (until-end-of-study population) from which our main conclusions were drawn was smaller than the one estimated to give a 90% power to detect. Therefore, our findings would need to be confirmed by larger studies.
| Appendix 1 |
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Reader: J. Gariépy.
Technical assistance: M. Massonneau.
Bayer project leaders: J.C. Provost, A. Deverly.
Statistician: D. Moyse.
Management Committee: A. Simon, J. Levenson, J. Gariepy, J.L. Megnien, D. Moyse, A. Deverly, M. Massonneau.
| Acknowledgments |
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Received January 18, 2001; revision received March 28, 2001; accepted March 30, 2001.
| References |
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