Experimental Design & Methods:



A. Specific Aims

The second leading cause of death in the United States is heart disease. It still remains that woman are affected more than men. In 2003, despite the fact over 700,000 Americans died of this disease, only 148,000 were diagnosed that year. Thus, 552,000 Americans were either not diagnosed or misdiagnosed (1).

Many individuals remain unaware of the symptoms of heart attack or dismiss possible symptoms as being unrelated or not important enough to visit a doctor. Such was the case in 2002 with 11% of adults that were told by their physicians that they had previously had heart disease without knowing it (2).

This Phase I proposal presents a solution to this public health problem via a simple, over-the-counter tool that would provide the user with an analysis of risk of heart disease.

The Phase I goals of this plan are:

1. Design a device that will be used to continuously record an individual’s electrocardiogram (ECG) over a period long enough to accurately diagnose heart-related issues. This Phase I device will include a differential amplifier, a microcontroller, and a USB compatible storage device.

2. Develop a user-friendly computer interface, which will analyze the data retrieved from the ECG collection device. The program will use the results of accepted studies on ECG waveforms and heart disease in order to determine level of risk.

3. Fabricate a prototype of the ECG collection device.

4. Perform testing with patients not diagnosed with heart disease to assess basic functionality of the system. The result of this goal will aid in future adjustments to the device to achieve a more accurate analysis.

B. Significance

Heart disease is a major concern in America. There is a need for people to understand their risk for this disease and other heart related problems so that the necessary steps can be taken to prevent serious complications before they start. In times of increasing costs of healthcare and increasing risk of heart complications, cheap, at-home and portable heart diagnostic tools are becoming more and more critical in the early stages of personal healthcare.

Our device is for the general public mainly towards adults over the age of forty. There are four main factors that will help determine whether you are likely to develop heart disease. These are family history, hypertension, obesity, and hypertension. Based on the 2002 Census, 119,386,252 people (42% of the population) belonged in the appropriate age group. Hypertension, or high blood pressure, affects approximately 28 million adults. Obesity impacts the lives of 41 million people. 20 million adults over the age of 40 are smokers.

This device would potentially detect and diagnose several disorders. Arrhythmias are disorders of the regular rhythmic beating of the heart and are fairly common. While they can occur in a healthy individual and not cause a problem, they can also indicate a serious health problem and lead to disease, stroke, or death. There are two types of arrhythmia. One is ventricular fibrillation which is an often fatal form of arrhythmia characterized by rapid, irregular fibrillar twitching of the ventricles of the heart in place of normal contractions, resulting in a loss of pulse. The other is atrial fibrillation, which is fibrillation in which the normal rhythmical contractions of the cardiac atria are replaced by rapid irregular twitchings of the muscular wall that cause the ventricles to respond irregularly.

Heart murmurs are most often caused by defective heart valves. A stenotic heart valve has a smaller-than-normal opening and can't open completely. A valve may also be unable to close completely. This leads to regurgitation, which is blood leaking backward through the valve when it should be closed.

People with sinus tachycardia have an abnormally rapid sinus rhythm; specifically a rhythm at a rate greater than 100 beats per minute. Whereas those patients with sinus bradycardia have an abnormally slow sinus rhythm; a rhythm at a rate lower than 60 beats per minute.

Finally, the monitor should detect heart block. This is a condition in which faulty transmission of the impulses that control the heartbeat results in a lack of coordination in the contraction of the atria and ventricles of the heart.

While there are heart monitors on the market, these devices are used almost exclusively when directed by a physician. They also use wires to collect data. This device would be unique in two ways. One, it would be designed to be purchased over the counter. This way, anyone could assess their personal risk of heart problems. Second, this system would be wireless. This will minimize the chances of the device interfering with the person’s normal activities.

There is currently a system known as Holter monitor, in which the doctor gives the patient a monitor to take home. In this device, the leads connect to a small recorder. One of the major problems of this device is that it costs upwards of $6000 dollars. However, this device indicates that it is feasible for the investigators to design and market the Wireless Heart Monitor.

C. Relevant Experience

James Cook has extensive experience in computer programming—particularly applicable to this study are LabVIEW and Matlab. He also has experience in analog and digital circuit design. He has worked with human subjects in biomechanics studies of keyboarding and gait under Drs. Rakié Cham, Mark Redfern, and Nancy Baker at the University of Pittsburgh, and is currently developing a device for the early detection of diabetic retinopathy under Dr. Michael Gorin.

Carmen Hayes is a bioengineering student at the University of Pittsburgh. She has carried out research in angiography and musculoskeletal imaging. At the University of Wisconsin-Madison, she conducted research comparing two methods of imaging the carotid artery using the MRI.

Joe Konwinski has worked for the department of neurosurgery for the past year developing a miniature implantable EEG for wireless signal transmission. In the past, he has carried out research in The University of Pittsburgh’s Department of Orthopaedic Surgery and done a clinical rotation with The Bradford Regional Medical Center’s Department of Microbiology.

D. Experimental Design & Methods

1. Design a wireless device that will be used to continually record an individual’s electrocardiogram (ECG) over a 24-hour period.

This Phase I device will include electrodes, a differential amplifier, a microcontroller, power supply, and USB compatible flash memory will be integrated into the device. Size constraints will be determined by further testing, but from previous work with miniature amplifiers, power supplies, and A/D converters it is expected that the complete device will be no bigger than 4.0 in. x 2.0 in. x 0.5 in.

Electrode Placement and Viable ECG Recording

Our main task in manipulating a basic ECG circuit (fig. 1) was to develop a filtering system that would allow us to bring positive, negative, and grounded electrodes of a three-lead ECG closer together without losing viable ECG recording(fig.2). Because the main constraints of our phase 1 study are product size and power consumption, we have limited ourselves to interpretation of cardiac rhythm from just one recording. This differs severely from a clinical standard 12-lead system which produces multiple ECG recordings and allows clinicians to better see malfunction in all parts of the heart.

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Fig. 1. Basic ECG circuit (Differential Amplifier) that is used as a base-line for initial testing of electrode placement. (Taken and adapted from reference 1.)

The risk of bringing electrodes closer together is that it becomes more difficult to remove low-frequency noise ( ................
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