Scientific Study

1. 186 Indian Journal of Physiotherapy & Occupational Therapy. April-June 2013, Vol. 7, No. 2
Assessment of Cardiovascular Functional Capacity and
Response to Exercise in Normotensive Offsprings of
Hypertensive Parents
Tarpan Shah1
, Shailaja Modithaya2
, Harsha H N3
, A M Mirajkar4
, Sreekumaran P5
1
Asst.Prof, Shree Swaminarayan Physiotherapy College, Surat, Kadodara Char Rasta, NH No 8 & 6, Gujarat,
2
Associate Prof. Dept of Physiology K S Hegde Medical Academy, Medical College campus, NITTE University
Campus, Deralakatte, Mangalore, 3
Associate Prof. Dept of Physiology K S Hegde Medical Academy, 4
Prof. & Head,
Dept of Physiology, K.S Hegde Medical Academy, 5
Principal, College of Physiotherapy, Medical Trust Institute of
Medical Sciences, Cochin
ABSTRACT
Study compared the cardiovascular functional capacity as well as the heart rate (HR) and blood
pressure responses to a 6 minute walk test (6MWT) between normotensive offsprings of normotensive
parents (NTP) and hypertensive parents (HTP). 60 subjects within the age group of 18 to 25 years
were studied. Basal Heart Rate (BHR), Systolic Blood Pressure (SBP) and Diastolic Blood Pressure
(DBP) were noted before the 6MWT. After performing 6MWT, the peak HR, SBP, DBP and the recovery
pattern of these parameters and distance covered were recorded. The study revealed that resting
DBP was significantly higher in the offspring of hypertensive parents. There was decreased DBP
response to exercise in the offspring of the hypertensive parents. However, the cardiovascular
functional capacity as measured by the distance covered during the 6MWT did not differ between
the two study groups. The study concludes that there is an early trend in higher blood pressure in the
offspring of hypertensive parents. Offsprings of hypertensive parents also exhibit an abnormal pattern
of HR and BP recovery from the exercise.
Keywords: Heart Rate, Systolic Blood Pressure, Diastolic Blood Pressure, 6MWT
INTRODUCTION
Hypertension, a major Public Health problem, is a
complex disorder with both environmental and genetic
predisposing factors. 30-40% of variability in BP is
attributable to genetic factors1
.Genetic predisposition
to Hypertension is likely to involve multiple genes2
.
It is probable that genetic substratum may manifest
in form of physiological variations and abnormalities
before onset of clinical Hypertension. Normotensive
subjects with parental history of Hypertension provide
a model system for the study of genetic factors in
Hypertension. Several features related to Hypertension
have been reported in normotensive offspring of HTP,
for instance they have greater Body Mass Index (BMI)3
,
elevated BP4
and exaggerated BPresponses to exercise5
.
Reduced cardiovagal outflow and impairment in
baroreflex sensitivity has also been reported in them6
.
There is increased attention directedtowards using
exercise testing to measure therapeutic response to a
lifestyle, medical, or surgical intervention7
. Studies
have revealed significant correlation between
exaggerated BP response to exercise and risk of
developing Hypertension. Cardiovascular reactivity to
exercise has been investigated in the offspring of HTP
in a few studies.8
Many studies have shown that the children of
hypertensive parents are more likely to develop
Hypertension, but very few studies were done to find
out about the early outcome of genetic transmission.
This study aimed to determine the early outcome
among hypertensive patients so that appropriate
preventive and treatment measures can be taken.
DOI Number: 10.5958/j.0973-5674.7.2.039
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2. Indian Journal of Physiotherapy & Occupational Therapy. April-June 2013, Vol. 7, No. 2 187
MATERIALS AND METHODOLOGY
In this Cross-sectional study, a total of 60 healthy
male subjects, aged between 18-25 years were
recruited. from the student population of Nitte
University, Mangalore Based on the presence or
absence of parental history of Hypertension, subjects
were divided as control group which consisted of -
Normotensive offsprings of NTP (N=30)), and a study
group consisted normotensive offsprings of HTP
(N=30)). Subjects with known history of Hypertension,
Diabetes, Recent fractures of the lower limb or other
known medical conditions were excluded from the
study. Ethical clearance was obtained from the Ethical
Committee of the Institute. The Study was performed
in the Department of Physiology, K S Hegde Medical
Academy.Nitte University. Informed consent was
taken from subjects for voluntarily participation in the
study.
EXPERIMENTAL PROCEDURE
As a pre-test assessment, parental history of
Hypertension was taken through a questionnaire. BMI,
BHR and SBP, DBP were assessed. To assess the fat
percentage, subjects’ skinfold thickness was measured
at four sites viz., Biceps, Triceps, Subscapular,
Suprailiac using a skinfold calliper. The subjects were
requested not to participate in any exercise or heavy
physical activity on the day of the test session. They
were requested to avoid eating a heavy meal two hours
prior to the test. Subjects wore comfortable,
nonrestrictive clothing. The subjects arrived at the test
room 15 minutes prior to the commencement of testing
procedure, to allow familiarization with the
environment and to establish a resting state. Their age
and cardiovascular parameters were noted. The
procedure was explained and Informed Consent was
obtained from the subject before the procedure. Then
the subject was made to sit on the chair for 10-15
minutes. Subjects were asked to inform immediately
of any of the following symptoms during the
procedure: chest pain, breathlessness, giddiness,
vomiting, nausea, and severe headache. The BP cuff
was applied to the arm and basal vital parameters like
Systolic and Diastolic Blood Pressure and Heart Rate
was recorded and the subject’s level of fatigue and
breathlessness were graded according to the Borg’s
scale.9, 10
Subjects were then instructed to perform 6MWT
according to standard ATS guidelines. At the end of 6
minutes the subjects were immediately made to sit on
the chair. HR and BP recordings were done at an
interval of 2 minutes until they return to pre-exercise
levels. The distance covered during the six minutes
was calculated from the number of laps completed and
the additional distance covered. Post test level of
dyspnea and fatigue was rated by using Borg’s Scale.
Statistical Analysis
Statistical analysis was performed with an SPSS
software package (Version 10.5). Normality of the
distribution for all the variables was assessed with the
Shapiro-Wilk test. Data are expressed as Mean ± SD.
Various variables between the two study groups were
compared using an independent t-test. Cardiovascular
responses within the subjects were compared with
repeated measure ANOVA. In all instances the null
hypothesis was rejected at P< 0.05.
Findings and Results
• Group 1 = Normotensive offspring’s of
Normotensive Parents
• Group 2 = Normotensive offsprings of
Hypertensive Parents
Table 1: Subject Characteristics and Anthropometric
Measurements
Variables Group 1N=30 Group 2N=30
Age (years) 21.30±2.77 21.10±2.73
Height (meter) 1.69±0.04 1.74±13.80
Weight (kg) 66.22±11.11 74.05±13.80
Body mass index (kg/m²) 22.74±4.84 23.12±6.40
Fat % 17.83±6.34 19.57±6.19
Fat Free Mass 53.37±6.83 59.22±8.67
Table 2: Comparison of Resting Cardiovascular
Parameters between Two Groups
Basal HR Basal SBP Basal DBP
GROUP 1 73.63±14.13 119.67±8.82 69.17±7.94
GROUP 2 73.57±12.41 122.20±9.74 73.97±6.84*
Values represent Mean ± SD
*Significantly different between the groups
Table 3: Six Minute Walk Distance
6Minute Walk
Distance
Group 1 729.20 ± 65.41
Group 2 728.32 ± 73.31
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3. 188 Indian Journal of Physiotherapy & Occupational Therapy. April-June 2013, Vol. 7, No. 2
Table 4: HR and Blood Pressure Responses to Six
Minute Walk Test
HR (%) SBP (%) DBP (%)
Group 1 51.94 ± 27.94 32.53 12.32 22.43 ± 13.37
Group 2 51.95 ± 32.85 30.14 10.47 15.38 ± 10.25*
Graph 3: Diastolic Pressure Response to 6MWT and
Post-Exercise Recovery in the offspring of NTP and
HTP
Graph 1: Values represent Mean ± SD. Repeated measure ANOVA
suggested significant differences within subjects and using
independent t-test, there is no significant difference between
groups.
Graph 2: SBP response to 6MWT and Post-Exercise
Recovery in the offspring of NTP and HTP
Graph 2: Values represent Mean ± SD. Repeated measures
ANOVA suggested significant within subjects but no between-
groups differences
Graph 1: HR response to 6MWT and post-exercise
recovery in the offspring of NTP and HTP
Graph 3: Values represent Mean ± SD. Analysis using repeated
measures ANOVA and Independent t-test. It has shown that the
recovery patterns were statistically significant both within
subjects and between-groups. The significant difference (P<0.05)
was observed for DBP at 4th, 10th
and 12th
minute of recovery from
6MWT.
DISCUSSION
Exaggerated blood pressure response to exercise is
independently associated with an increased risk of
future Hypertension, and therefore, may be an
important factor in determining Hypertension risk5
,
6MWT is currently the test of choice while using
functional walk tests for Clinical or Research
purposes.11, 12
The two study groups i.e., normotensive offsprings
of normotensive parents and normotensive offsprings
of hypertensive parents were matched for age, sex and
BMI. They differed only in the genetic propensity for
developing Hypertension in later life.
Resting BP HR
The study revealed that resting DBP was
significantly higher in normotensive offspring of HTP
compared to normotensive offspring of NTP.
Difference in resting SBP of both groups was not
statistically significant. However, resting HR was
comparable between the groups. Studies have
supported the findings, those who have a family
history of Hypertension, their resting DBP was higher
in preadolescent and adolescent groups. 13, 14
Previous
studies have found that individuals with high-normal
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4. Indian Journal of Physiotherapy & Occupational Therapy. April-June 2013, Vol. 7, No. 2 189
BP progress towards Hypertension twofold to
threefold more frequently than subjects with normal
BP on 26 years follow up 15
. A study suggested resting
higher BP to be a better predictor of future
Hypertension. 16
. Present study indicates that the
offspring of HTP have a higher risk of developing
future Hypertension.
Six minute walk distance
The 6MWT is useful measurement of functional
capacity for people with normal to moderately severe
impairment.17
In the present study; the six minute walk
distance covered by the two study groups did not show
any significant difference. Both the study groups
covered a distance which is comparable with values
reported in guidelines by ATS18
So history of
Hypertension in parents may not have significant
impact on cardio respiratory exercise capacity assessed
by 6MWT.
Cardiovascular Response
The present study showed a significant increment
in HR, SBP and DBP following 6MWT in the both study
groups. But a percentage of increment for DBP was
significantly lower in the offspring of HTP. A study
reported, BP response to treadmill testing between
normotensive offspring of HTP and normotensive
offspring of NTP showed that peak SBP and DBP was
higher.9
Other studies also supported that offsprings
of hypertensive parents have an exaggerated blood
pressure response to exercise.19,20,21
A study found total peripheral resistance in those
with exaggerated BP response did not fall adequately
to compensate for rise in cardiac output during exercise
and it has also been explained by increased peripheral
vascular resistance and impaired capacity for exercise
induced vasodilatation.22
Recovery pattern of cardiovascular response to
exercise shown to be one of the most important
markers for predicting Hypertension. In the present
study we found offspring of HTP were having higher
DBP at 4th
, 10th
and 12th
minutes following termination
of 6MWT compared to control group.
CONCLUSION
History of hypertension in parents may not have a
significant impact on cardio respiratory exercise
capacity assessed by 6MWT in the age group of 18-25
years. Higher resting diastolic blood pressure in
offsprings of hypertensive parents in this study
indicates that an early trend in higher blood pressure
that may be associated to the genetic risk. Decreased
diastolic blood pressure response to exercise in
offsprings of hypertensive indicates reduced reactivity
to exercise in offspring of hypertensive parents could
be due to impaired autonomic regulation of peripheral
resistance during exercise. The study also concludes
that there is abnormal pattern of recovery from the
exercise in offsprings of hypertensives.
ACKNOWLEDGEMENTS
We present sincere gratitude to Prof. Mohamed
Faisal CK. Vice principal NITTE Institute of
Physiotherapy and Dr .Hiral Gandhi, Lecturer, Shree
Swaminarayan Physiotherapy College Surat, for their
Guidance and Support and Encouragement
throughout the course of study.
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