Cardiovascular Journal of Africa: Vol 26 No 3 (May/June 2015)

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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 26, No 3, May/June 2015 AFRICA 135
doses have been ingested. Although studies have compared
the efficacy of HS and NaHCO3 treatments in patients with
cardiotoxicity, the role of these therapies to prevent or reduce
cardiotoxicity in patients who may potentially develop severe
toxicity has not been investigated. The aim of this experimental
study was to compare the effect of early administration of HS or
NaHCO3 on preventing cardiotoxicity in rats that had received
toxic doses of amitriptyline.
Methods
The experiments were performed on adult female SpragueDawley
rats weighing 250 to 300 g that were obtained from the Ondokuz
Mayis University vivarium. The rats were kept in a vivarium
maintained at 22 ± 1°C with a 12-hour alternating light–dark
cycle. All the experiments were approved by the Institutional
Animal Care and Use Committee of Ondokuz Mayis University,
and adhered to the guidelines of the Committee on Human/
Animal Experimentation (institutional or regional), and the
Helsinki Declaration of 1975, as amended in 1983.
Amitriptyline was obtained from Sigma-Aldrich Chemical Co
(St Louis, Missouri, USA). It was dissolved in distilled water at a
concentration of 50 mg/4 ml. HS solution (3% sodium chloride,
sodium 512 mEq/l) and NaHCO3 8.4% (sodium 1 mEq/ml) were
used.
The animals were randomly divided into six groups, with each
group containing six rats. They were anesthetised (100 mg/kg
ketamine and 0.75 mg/kg chlorpromazine i.p.) and then prepared
for monitoring of electrocardiogram (ECG) parameters.
Their survival time was recorded by a data-acquisition system
(ML870/P, PowerLab 8/30, AD Instruments).
Amitriptyline was administered at a dose 50 mg/kg i.p. to
induce toxicity. The HS was administrated at a dose rate of
6 ml/kg, and the NaHCO3 was administrated at a dose rate of
3 mEq/kg. Both were administered via i.v. infusion and applied
simultaneously with amitriptyline over a period of five minutes.
To administer the dosage, i.v. cannulas were inserted into the tail
of the rats. The toxic doses and treatments given to the different
groups are shown in Table 1.
ECGs were recorded on each rat for 60 minutes after the
administration of the respective protocols. All records were
evaluated by a cardiologist. On the ECG records, the R–R
distance, height of the QRS and duration of the QT were
measured. The R–R is the interval from the onset of one QRS
complex to the onset of the next QRS complex, measured in
seconds. The heart rate and the corrected QT (QTc) interval were
calculated according to the R–R distance and the duration of the
QT. Heart rate was calculated by dividing the R–R interval by 60
(heart rate = 60/R–R interval).
The QRS duration was measured from the beginning of
the Q wave to the end of the S wave. The QT interval was
measured from the onset of the QRS complex to the end of the
T wave, defined as the return to the TP isoelectric line. The QT
interval was defined as the average of the QT intervals of three
consecutive beats in each of the ECG leads. The QT intervals
were also corrected for heart rate using Bazett’s formula. The
QTc is equal to the QT interval in seconds divided by the square
root of the preceding R–R interval in seconds. A decrease in the
heart rate below 100 beats/minutes or the presence of asystole
during recording was accepted as the exodus.
To measure serum levels of sodium and ionised calcium,
blood samples were obtained from the carotid arteries of the
living rats 60 minutes after the administration of amitriptyline
or other treatments, but immediately from the rats that had died.
Statistical analysis
Statistical analyses were performed with IBM SPSS 21.0
(Chicago, IL, USA). The Kolmogorov–Smirnov test was used
to evaluate the distribution of variables in relation to normal.
Descriptive statistics were presented as the mean ± standard
deviation. Statistical comparisons between all groups were
performed with one-way ANOVA with a Tukey post-hoc test.
Correlations between the quantitative data were analysed by the
Pearson correlation test. The level of statistical significance was
set at p < 0.05.
Results
The characteristics of the rats in all groups were similar. In group
1, all the rats died in the first 25 minutes. Therefore, the statistical
analyses with group 1 included data for only the first 25 minutes.
The other inter-group statistical analyses included data obtained
over 60 minutes.
The initial heart rate was similar among the groups. The
heart rates of the rats in groups 1, 2 and 3 decreased in direct
proportion to time, with the decrease more marked in group
1. The heart rates of the rats in groups 4, 5 and 6 did not show
significant change over time.
Hypertonic saline or NaHCO3 administration, along with
amitriptyline, ameliorated the reduction in the heart rates. There
was no significant difference in the heart rates between the HS
and NaHCO 3 groups. Table 2 shows a comparison of the heart
Table 1. Design of study and groups and chemicals used
Group Drugs
1 Only amitriptyline (50 mg/kg i.p.)
2 Amitriptyline (50 mg/kg i.p.) + 3 mEq/kg NaHCO3 (diluted with
normal saline of 1:1 ratio) during the five minutes (once)
3 Amitriptyline (50 mg/kg i.p.) + 6 ml/kg hypertonic saline during the
five minutes (once)
4 Only 6 ml/kg hypertonic saline during the five minutes (once)
5 Only 3 mEq/kg NaHCO 3 (diluted with normal saline of 1:1 ratio)
during the five minutes (once)
6 Control group (none of the drugs or treatment)
Table 2. Heart rate changes with time according to group
Group Start
5th
minute
10th
minute
15th
minute
20th
minute
25th
minute
1 353 ± 21* 300 ± 37c 269 ± 31c,d,e 242 ± 31a,c,d,e 217 ± 28a,b,c,d,e 201 ± 28a,b,c,d,e
2 350 ± 17* 321 ± 34g 304 ± 34g 294 ± 34a,g,h,i 281 ± 33a,g,h,i 277 ± 32a,g,h,i
3 345 ± 19* 327 ± 25* 309 ± 30j 290 ± 32j,k,l 285 ± 32b,j,k,l 285 ± 31b,j,k,l
4 368 ± 26* 373 ± 27* 371 ± 23c,g,j 375 ± 23c,j,g 379 ± 23c,g,j 377 ± 22c,g,j
5 346 ± 14* 343 ± 21* 344 ± 18d 345 ± 22d,h,k 346 ± 23d,h,k 347 ± 28d,h,k
6 352 ± 34* 346 ± 23c,g 344 ± 23e 352 ± 27e,i,l 348 ± 23e,i,l 347 ± 26e,i,l
Mean 352 ± 23 335 ± 35 324 ± 42 316 ± 53 309 ± 60 312 ± 61
p- value 0.542 0.003 0.000 0.000 0.000 0.000
* The group with no difference from the others, p < 0.05 ( acompared with groups
1 and 2, b compared with groups 1 and 3, ccompared with groups 1 and 4, dcom-
pared with groups 1 and 5, ecompared with groups 1 and 6, fcompared with
groups 2 and 3, g compared with groups 2 and 4, hcompared with groups 2 and 5,
i compared with groups 2 and 6, j compared with groups 3 and 4, k compared with
groups 3 and 5, lcompared with groups 3 and 6).