Biomedical Engineering, Vol. 46, No. 2, July, 2012, pp. 7578. Translated from Meditsinskaya Tekhnika, Vol. 46, No. 2, Mar.Apr., 2012, pp. 3438. Original article submitted April 12, 2011.
A Device for Estimating Risk of Occurrence of Cardiovascular Insufficiency during Exercise Stress D. A. Usanov1*, A. A. Protopopov2, I. O. Bugaeva2, A. V. Skripal1, A. P. Averyanov2, A. Yu. Vagarin1, A. A. Sagaydachnyi1, and E. O. Kashchavtsev1
Results of study of the occurrence of cardiovascular insufficiency in juvenile sportsmen during exercise stress are described. A method for screening diagnosis of the collapsoid complication risk is given. It is shown that the pres ence of anomaly in shape of the pulse wave in combination with vagotonic nervous regulation of the cardiovas cular system of the patient is a sign of collapsoid state during exercise stress. The results of comparative analysis of data obtained during estimation of cardiovascular insufficiency risk during exercise stress with data of detailed medical examinations of juvenile sportsmen are presented.
Studies of the cardiovascular system in juvenile sportsmen and adolescents have a central place in pedi atrics. The functional state of the system provides adapta tion of the human body to physical load [1]. Estimation of occurrence of cardiovascular insufficiency risk during exercise stress is a very important problem. Presently, this problem is solved using ECG, Dopplerechocardiography, rhythmoECG, bicycle ergometry, etc. The use of these methods requires skilled medical personnel [2, 3]. Analysis of the pulsation wave also provides information about the state of the cardio vascular system. Such information can be obtained using sphygmography, elastometry, etc. [4]. These methods can detect only pronounced pathology, but fail to diagnose collapsoid complications induced by physical load. It was reported in [5, 6] that maximal risk of cardio vascular insufficiency is inherent in dysplasia of conjunc tive tissue and autonomous nervous system disorder. Collapsoid reaction in children and adolescents is induced by a combination of these factors, even if each individual factor does not induce collapsoid reaction. These factors can be estimated using pulse wave, e.g. the slope angle of the systolic stage and catacrotic heart rate.
These factors provide information about elasticity of arte rial blood vessels and peripheral circulation resistance. Variability of cardiointervals can also be estimated. A device for rapid diagnosis of cardiovascular system state was developed at VolgaMetExpo, Ltd. in collabora tion with Chernyshevsky Saratov State University and Razumovsky Saratov State Medical University. This device diagnoses risk of cardiovascular insufficiency dur ing exercise stress [79]. The goal of this work was to test the device for esti mating risk of cardiovascular insufficiency during exercise stress in children and adolescents.
Monitoring System A block diagram and general view of the device for estimating risk of cardiovascular insufficiency during physical load are shown in Fig. 1. The cuff is attached to patient’s arm, and arterial pressure is measured using a manometer. The pressure in the cuff is measured using the tensometric Motorola MPX 2050 DP sensor 1 with two differential inputs. ADC 2 provides signal sampling; the resulting digital signal is stored in database 3. The amplitude of the pulsation wave is measured for 1530 sec (1530 cardiocycles). The results of the monitoring are processed using special software. The software recom mends or warns against physical load. The total time of diagnosis is ~1 min.
1
Chernyshevsky Saratov State University, Saratov, Russia; Email:
[email protected] 2 Razumovsky Saratov State Medical University, Saratov, Russia. * To whom correspondence should be addressed.
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00063398/12/46020075 © 2012 Springer Science+Business Media, Inc.
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Usanov et al.
a
b
Fig. 1. Block diagram (a) and general view (b) of device for estimating risk of cardiovascular insufficiency during physical load: 1) pressure sensor with cuff for monitoring arterial pressure; 2) ADC; 3) computer.
Signal Processing Algorithm Pulse wave parameters of processing are: systolic stage slope angle in fast and slow phases; catacrotic heart rate; and cardiac interval variability in the systolic stage. Pulse wave shape was analyzed using the first and second derivatives. Systolic elevation of the wave pulse can be divided into two phases (fast and slow). During systole, the fast stage time VNfast and slow stage time VNslow characterize heart stroke volume and vascular wall elasticity, respectively [2]. Anacrotic systolic wave time (VN) can be calculated from the moments of zeroing of the first derivative of the pulse wave (Fig. 2). The second derivative minimum reveals the transition from the fast to slow stage. The first
P1 = VNfast/Tpw; P2 = BN/Tpw. The amplitude parameter P3 was used in analysis of the pulse wave shape. This parameter was calculated at the catacrotic phase using the second derivative d2A/dt2: P3
VPmax
Derivatives
Amplitude, arb. units
Pulse wave First derivative Second derivative
VNfast VNslow VN
and second derivatives of the pulse wave reveal the pulse wave shape in the systolic elevation phase. Pulse wave slope angle was assessed using parameters VNfast, VNslow, and VPmax. The amplitude of the first deriv ative at moment VPmax is a parameter of maximal slope angle in the fast phase. Systolic elevation slope angle was calculated using the following parameters: fast phase time VNfast/pulse wave period Tpw (P1); anacrotic time/pulse wave period (P2):
Tpw
Fig. 2. Pulsation wave parameters of interest (patient No. 1).
where N is pulse wave point number at which the second derivative was calculated. Parameters P1, P2, and P3 were averaged over the pulse wave periods. Pulse waves with abnormal shape are shown in Fig. 3. The figure also shows the first and second derivatives. Anomaly of the cardiovascular system was observed at P1 < 0.1 (Fig. 3a), P2 < 0.12 (Fig. 3b), or P3 < 55 (Fig. 3c). It follows from Fig. 3 that pulse wave parameters P1, P2, and P3 in the normal case and in the case of pathology are different, which is due to elasticity and peripheral resist ance of arteries. A decrease in arterial tonicity is accom panied by pulse wave shape change (systolic slope angle increase and systolic time decreases). The catacrotic sec ond derivative in the apparently healthy patient gradually
Estimating Risk of Occurrence of Cardiovascular Insufficiency during Exercise
a
Derivatives
Amplitude, arb. units
Pulse wave First derivative Second derivative
t, sec
b
Derivatives
Amplitude, arb. units
Pulse wave First derivative Second derivative
t, sec
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– Amo – mode amplitude: percentage of cardioint ervals typical of mode range representing sympathetic nervous system mobilization; – Dx – variation range: difference between maximal and minimal values of KI, sec; – CI – centralization index; – ARP – autonomous rhythm parameter. This parameter provides information about parasympathetic balance. The lower is ARP, the larger is the shift toward the parasympathetic site. Baevsky indices were calculated using pulse wave intervals between maximums (systole). Cardiac interval histograms and corresponding Baevsky indices for nor motonic (Fig. 4a) and vagotonic (Fig. 4b) autonomous regulation types are shown in Fig. 4. Excessive vascular tonicity and parasympathetic vas cular regulation are symptoms of risk of cardiovascular insufficiency during physical stress [5, 6].
Results Fortynine patients (1416 years old; mean age, 14.8) were tested. The patients were football players born in 19951997. Before the tests each patient was examined
c a Number of intervals
Derivatives
Amplitude, arb. units
Pulse wave First derivative Second derivative
CI ARP
Interval duration, sec t, sec
fluctuates around zero (Fig. 2). A gradual decrease in the catacrotic second derivative (parameters P3) is indicative of a trend toward linear shape. In each patient, activity of the autonomous nervous system was determined from the chronotropic structure of cardiac rhythm (Baevsky index) [10, 11]: – Mo – mode: RR interval time, which is an indi cation of domination of sinus activity;
Number of intervals
Fig. 3. Pulse waves with abnormal shape: a) patient No. 44 P1 = 0.09; b) patient No. 16 P2 = 0.11; c) patient No. 10 P3 = 41.6.
b
CI ARP
Interval duration, sec
Fig. 4. Cardiac interval histograms and corresponding Baevsky indices: a) normotonic autonomous regulation type; b) vagotonic autonomous regulation type.
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for arterial pressure and anthropometric parameters (height and body weight). Pulse wave was monitored using a special device for estimating the risk of cardiovascular insufficiency during exercise stress. Twelve patients had pathologies of the cardiovascular system of various types. Vagotonic regulation was observed in nine of the adolescents. A combination of the two factors was observed in six of the adolescents. A group of 15 adolescents was subjected to compre hensive examination. A combination of the two factors was observed in six of the adolescents. Pulse wave anom aly was observed in five subjects (second derivative d2A/dt2, parameter P3). Vagotonic nervous system without pulse wave deviation was observed in three of the subjects. The tests were performed at the Mirotvortsev Saratov Clinical Hospital by highly skilled physicians, specialists in pediatrics, exercise therapy, sports medicine, ECG, Dopplerechocardiography, etc. According to the comprehensive tests, nine of the subjects had autonomous dysfunctions, seven demon strated anomaly in the orthostatic test, and six demon strated anomaly in bicycle ergometry. Five of the subjects demonstrated abnormal ECG (accelerated repolarization); five showed cardiac rhythm deviation (sinus arrhythmia); one revealed supraventricu lar extra systole. Two of the subjects had right His band blockage; one had left His band blockage. Doppler echocardiography revealed mitral valve prolapse I in four of the subjects. Three demonstrated additional left ventri cle chords. The results of the tests demonstrated ECG anomaly in five adolescent sportsmen (ECG anomaly in combina tion with heart development anomaly). Two of the adoles cents demonstrated pathology of the cardiovascular sys tem; six showed abnormal regulation of the autonomous nervous system. Eight of the sportsmen were recom mended to modify the character of exercise training. Repeat testing was also recommended. No limit in the exercise training load was recommended for six of the sportsmen with deviation of pulse wave or cardiac inter val.
Usanov et al.
Conclusion A device for rapid screening of cardiovascular system state in juvenile sportsmen and adolescents was developed at the VolgaMetExpo, Ltd., in collaboration with Chernyshevsky Saratov State University and Razumovsky Saratov State Medical University. The device provides diagnosis of risk of cardiovascular insufficiency during exercise stress. The risk of exerciseinduced collapsoid reaction was prognosticated in the case of anomalous pulse wave shape in combination with vagotonic type of nervous regulation of the cardiovascular system.
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