DIASTOLIC TIMED VIBRATIONS FOR PRE-HOSPITALIZATION

TREATMENT OF MYOCARDIAL INFARCTION

Marcin Marzencki, Farzad Khosrow-Khavar, Syed Ammar Zaidi, Carlo Menon and Bozena Kaminska

Department of Engineering Science, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada

Keywords:

Heart attack, MI pre-hospitalization treatment, Coronary thrombosis.

Abstract:

Heart attack or myocardial infraction is the leading cause of deaths in the modern world. In order to increase

survival chance of patients, action should be taken during the ﬁrst hour from the onset of symptoms, which

is most often impossible with the current technology. To this end, we propose a method of heart attack

treatment based on low frequency diastolic timed vibrations. This method can be used in ambulatory setting

by unspecialized personnel as it is noninvasive and safe for the patient. It is based on applying low frequency

mechanical vibrations synchronized with the heart cycle of the subject along with application of thrombus

dissolving drugs. We present an analysis of the proposed methodology and provide experimental results

obtained with a prototype device.

1 INTRODUCTION

In the developed world, heart diseases are the leading

cause of death, presenting higher mortality rate than

cancer (American Heart Association Statistics, 2010).

In the United States alone, over 7 million men and

6 million women are living with some form of coro-

nary heart disease and over a million people suffer a

(new or recurrent) coronary attack every year. About

40% of heart attacks result in death (American Heart

Association Statistics, 2010). Myocardial Infarction

(MI) or heart attack is most often caused by forma-

tion of a blood clot (thrombus) blocking the arterial

vasculature surrounding the heart. MI refers to my-

ocardial cell death and occurs due to a complete coro-

nary obstruction which results in a profound blood

ﬂow impairment causing inadequate oxygen delivery

to the heart muscle. Once such an obstruction begins,

cell death can occur in as little as 20 minutes. Com-

plete death of all myocardial cells at risk can occur

in, at the earliest, 2 to 4 hours (Kostuk, 2008). Var-

ious methods have been developed to dissolve or re-

move thrombus before MI occurs. Preferred invasive

methods such as angioplasty require signiﬁcant setup

time and resources in order to be successful. Inci-

dentally, the most effective treatment occurs during

the ﬁrst 60 minutes of the symptoms known as the

golden hour. However, by the time an average pa-

tient reaches a hospital most deaths have already oc-

curred (Turner and Rosin, 2008). This is worsened

by the fact that those who manage to reach a hospital

spend additional time undergoing examinations or be-

ing transported to a cardiac cathlab before the actual

treatment can begin. As a result, speed of interven-

tion is the biggest factor in saving a patient’s life and

is the key to effective heart attack treatment. Thus, if

treatment could begin during transportation to a hos-

pital, it would play a key role in ensuring the survival

of patients.

To this end, we propose a method of treatment that

could be safely applied by unspecialized personnel

on-site or during patient transportation to the hospital.

We believe that this method could drastically improve

the survival rate of heart attack patients.

2 PROPOSED METHOD

We present a safe non-invasive method suitable for

treatment of heart attack and other states of low coro-

nary blood ﬂow. It is based on applying low level

mechanical vibrations in the chest area along with

application of clot dissolving drugs. By performing

vibrations during the diastolic period of the cardiac

cycle (the relaxation of the heart) it is expected that

coronary ﬂow is increased and thrombus dissolution

is achieved. In this study, we ﬁrst aim at developing a

vibrating system that is independently controlled by a

real-time ECG signal. The triggering of the vibrating

405

Marzencki M., Khosrow-Khavar F., Ammar Zaidi S., Menon C. and Kaminska B..

DIASTOLIC TIMED VIBRATIONS FOR PRE-HOSPITALIZATION TREATMENT OF MYOCARDIAL INFARCTION.

DOI: 10.5220/0003130604050408

In Proceedings of the International Conference on Bio-inspired Systems and Signal Processing (BIOSIGNALS-2011), pages 405-408

ISBN: 978-989-8425-35-5

 2011 SCITEPRESS (Science and Technology Publications, Lda.)

system should be synchronized with the ECG signal

in such a way so as to remain vibrating in the dias-

tole and cease all vibrations in the systole of the ECG

signal.

Our goal is to create a device for ﬁeld use - a Dias-

tolic Timed Vibrator (DTV) to be employed by med-

ical emergency personnel to remediate acute states of

low coronary blood ﬂow, such as those exhibited in

angina pectoris (chest discomfort secondary to coro-

nary artery narrowing) or heart attack (an acute block-

age of a coronary artery, usually by a blood clot). The

DTV will impose mechanical vibrations to the chest

of the patient in order to improve coronary blood ﬂow.

We aim at creating an inexpensive and portable sys-

tem requiring minimal intervention of specialized per-

sonnel.

2.1 Mechanical Vibrations

There is strong experimental evidence that diastolic

mechanical vibrations on the chest wall increase coro-

nary blood ﬂow (CBF). In past studies, diastolic vi-

brations performed on patients with coronary arte-

rial disease (CAD) and on normal subjects resulted in

an immediate increase of CBF as measured by both

transesophageal doppler and coronary ﬂow wire. The

CBF increase in CAD patients was signiﬁcantly larger

than those of normal subjects (Taihei et al., 1994). In

addition, clinical studies performed on humans and

canines (Koiwa et al., 1997) have shown that exter-

nal diastolic vibrations can release incomplete relax-

ation (IR) and improve the systolic function of the

heart. Similar studies (Koiwa et al., 1997) consisting

of external vibrations applied on human patients with

aortic regurgitation (AR) and ischemic heart disease

(IHD) resulted in a decrease of left ventricle systole

pressure; proving that vibration induced depression

does occur in humans. Clinical studies have shown

that diastolic timed mechanical vibrations around 50

Hz improve coronary blood ﬂow and left ventricu-

lar (heart muscle) performance in human volunteers,

with and without coronary artery disease (Taihei et al.,

1994). Low frequency vibration is a known potent va-

sodilator, especially for arteries with a degree of ac-

tive tension or spasm, which is often the case in heart

attack (Oliva and Breckinridge, 1977), and it has fur-

ther been shown to signiﬁcantly enhance clot disso-

lution with or without a thrombolytic agent both in-

vitro and in commercially available catheter systems

(Evans et al., 2003).

2.2 ECG Synchronization

Our method provides a new technique for disrupting

and clearing the thrombus present in a patient’s ar-

terial vasculature surrounding the heart. During sys-

tole the heart is contracting and pressure needed for

driving the blood is being generated within the cham-

bers of the heart. As a result, vibrations should only

be applied in the diastole (Koiwa et al., 1997). Fur-

thermore, it has been demonstrated in clinical stud-

ies that vibrations timed exclusively to the diastole of

the cardiac cycle advantageously facilitate heart mus-

cle relaxation and paradoxically improve the strength

of the heart contractions and hence can be utilized

safely (Koiwa et al., 1994). In order to be able to

synchronize mechanical vibration with the heart cy-

cle, the ECG signal has to be analyzed and QRS com-

plexes indicating the onset of systole have to be iden-

tiﬁed. Automatic detection of QRS complexes has

been a subject of intensive research in the last several

decades. Proposed algorithms range from simple ﬁl-

ters to very calculation intensive machine learning al-

gorithms (Kohler et al., 2002). Currently, most algo-

rithms use a discrete or continuous wavelet transform

which gives both the time and frequency characteris-

tics of the signal. Machine learning algorithms such

as Hidden Markov Model, Neural Networks and/or

Support Vector Machine (SVM) are used to classify

different parts of the ECG signal. The extensive

amount of training that is required prior to use is a

serious limitation of these methods in certain cases.

We decided to use the widely employed ”Tompkins”

algorithm due to its implementation simplicity and ro-

bustness in ﬁnding abnormal QRS complexes.

2.3 System Architecture

The proposed system is composed of four main parts:

vibrator, accelerometer, ECG system, DC power sup-

ply, and a LabView VI containing signal processing

and control. Figure 1 schematizes the system archi-

tecture.

The mechanical vibrations were generated using

a commercially available massager device (Human

Touch HT-1280) driven by a DC voltage source inter-

faced with LabView. This setup generates the linear

movement of the plate attached to a patient. An active

damping stage is added to adjust the amplitude of gen-

erated vibrations and allow for rapid stopping of the

motor. In order to be able to generate vibrations only

in the desired periods of the heart cycle, an electro-

magnetic relay is introduced on the power line of the

motor. This setup allows for efﬁcient control of on-off

time of the motor along with its rotational frequency.

Furthermore, a MEMS accelerometer (LIS3L02AL)

has been integrated into the vibrating plate to provide

a feedback on the generated vibration amplitude and

BIOSIGNALS 2011 - International Conference on Bio-inspired Systems and Signal Processing

406

DC motor

massager

ECG electrodes

feedback

accelerometer

patient's

chest

ECG

DC power

supply

acceleration data

processing

ECG data

filtering

pulse

generator

QRS complex

detection

LabView VI

DAQ

motor

voltage

control

DAQ

Figure 1: Block diagram of the proposed diastolic vibration

system.

frequency.

An ECG acquisition system Burdick EK10 is em-

ployed to amplify and ﬁlter the ECG signal. The re-

sulting signal is digitalized by a DAQ at 14bit and

200Hz and further processed in LabView.

An algorithm has been developed to detect the

systole and diastole in a real time ECG signal in order

to allow diastolic timed vibration. We created a vir-

tual instrument using National Instruments LabView.

The VI software implements the real-time Hamilton

and Tompkins QRS complex detection algorithms.

Figure 2 presents the stages of the algorithm. The

ECG signal is band-pass ﬁltered with a combination

of low and high pass ﬁlters to separate the high energy

QRS complex from the rest of the ECG signal. The

resulting signal is differentiated to extract the onset of

R-wave. Next, the signal is squared to make it posi-

tive prior to integration. The integrator sums the area

of the positive wave form. The width of the integra-

tor is chosen carefully to be long enough to consider

abnormally long QRS complexes and short enough so

that it does not overlap with the T-wave. The operator

can pick the window size and the detection threshold

in the software.

The frequency of QRS complexes is used to cal-

culate the heart beat rate and the period of the ECG

signal. Furthermore, lengths of two counters are cal-

culated which, in coordination with the R peak de-

tection, are time controlled to stop the vibrating sys-

tem during systole and enable it during diastole. Af-

ter detecting the R peak, systole counter is reset dis-

abling the vibrating system until the systole cycle is

complete. Once the systole counter reaches its limit

(which is derived from the period of ECG signal), the

vibrating system is enabled again for a duration deter-

n=32

n=1

Real-time ECG signal

acquistion

QRS complex detection

Heart rate calculation

Counter length

determination

Counter control and driving

pulse generation

Low pass filter

High pass filter

[]

Figure 2: Block diagram of the ECG signal processing used

to generate driving signal for mechanical vibrations syn-

chronized with the diastole of a cardiac cycle.

mined by the diastole counter. The diastole counter is

accordingly set to reach its limit before the beginning

of the systole cycle. In case where the two counters

overlap due to arrhythmic operation of the heart, the

systole counter has priority over the diastole counter;

thus ensuring that any detection of an R peak would

immediately disable the vibrating system. The sys-

tole counter duration was approximated based on the

QT interval calculations performed during past clini-

cal studies of heart disease patients (Alexander et al.,

1951).

3 EXPERIMENTAL RESULTS

In order to verify the accuracy of our predictions con-

cerning the effectiveness of diastole timed vibrations,

we built a prototype system. We concentrated on

proper synchronization of the mechanical vibrations

with the ECG signal.

Figure 3 shows mechanical vibrations generated

with the massager synchronized with a real-time ECG

signal. The overall period of the heart beat is 2 sec-

onds in which the PQRST region of the ECG lasts

for 0.55± 0.05s. Although the systole (QRST region)

only lasts for 0.41 ± 0.04 seconds, the vibrating sys-

tem is turned off before the PQRST region begins in

order to ensure that vibrations occur only when the

heart is in its relaxation state. During the diastolic cy-

cle, the DC motor is allowed to vibrate for 1.40 ± 0.04

seconds. The massager device has high rotary inertia,

therefore a special damping stage was introduced in

order to allow more precise timing of the generated

vibrations. The delay between the end of the driv-

ing pulse and the actual termination of the mechanical

vibrations was measured to be approximately 17ms .

Therefore, the vibration spill deﬁned as the amount

DIASTOLIC TIMED VIBRATIONS FOR PRE-HOSPITALIZATION TREATMENT OF MYOCARDIAL INFARCTION

407

-0.5

0.5

1.5

1 1.5 2 2.5 3 3.5 4 4.5 5 5.5

-1.5

-1

-0.5

0.5

Acceleration [g]

ECG [mV]

Time [s]

Acceleration

ECG

Vibration

trigger signals

Figure 3: Experimental results for mechanical vibrations

(represented by acceleration amplitude) synchronized with

diastolic period of the cardiac cycle.

of vibrations present in the systole is minimal. For

the most part, the QT interval was free of vibrations

and with the predictive termination of vibration based

on a regression algorithm, it was possible to com-

pletely avoid vibration spill on the QRS complex in

most cases.

4 CONCLUSIONS

The proposed diastolic timed vibration system is a

safe and innovative method for rapid treatment of

heart strokes and other low blood ﬂow cases. Clinical

studies have shown that mechanical vibrations help

increase the coronary blood ﬂow and aid in the im-

provement of the systolic function of the heart. In

case of a heart attack, mechanical vibrations along

with application of thrombolytic agents can improve

clot dissolution and thus increase chances of patient’s

survival. We presented a prototype of a diastolic

timed vibrator controlled by a custom LabView VI

and synchronized with a commercial ECG system.

We demonstrated that mechanical vibrations gener-

ated by a massager device can be synchronized with a

real time ECG signal from a patient. We developed al-

gorithms used in the control Labview VI used to trig-

ger the vibrator only in the diastole. The presented

results show that we can accurately control the me-

chanical vibrations and thus avoid application of vi-

brations in the critical part of the QT interval.

ACKNOWLEDGEMENTS

This project was supported by Simon Fraser Univer-

sity in collaboration with Ahof Biophysical Systems

Inc. The authors would like to thank Andrew Hoff-

man for valuable inputs to the project.

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