HeartDiagnostic

Motivation: Case Scenario correlating increased Troponin measurements with Acute Coronary Syndrome

“Case Presentation: J.P. is an obese 55-year-old male with a history of gastroesophageal reflux disease who presents to the emergency department with substernal chest pain that he attributes to a “large meal.” J.P. is pale and diaphoretic. An ECG shows tachycardia with normal sinus rhythm. J.P.’s troponin levels (decision limit >0.04 μg/L) at presentation and at 6 and 12 hours after presentation are 0.09, 4.41, and 19.62 μg/L, respectively.” http://www.circ.ahajournals.org/content/116/18/e501.full

“J.P.’s presentation and troponin results are consistent with the diagnosis of ACS (Figure 1A). An additional cTnI measurement, 48 hours after admission, revealed a downward trend in his troponin level. Because of the improved sensitivity and precision at low cTnI concentrations, the initial cTnI result indicated myocardial injury and the subsequent diagnosis of ACS.”

http://www.circ.ahajournals.org/content/116/18/e501.full

Background

a) Acute Coronary Syndrome: Symptoms and Biomarkers

Acute coronary syndrome (ACS) is a disease attributed to obstruction of the coronary arteries. Heart attack or unstable angina are categorized as ACS. The immediate symptoms include chest pain and discomfort, pain in arms and legs, nausea, and sweating. Upon feeling any of the symptoms, it is important that patients go through the diagnostic process so that immediate care can be provided. However, current diagnosis of ACS is very time-demanding and unapproachable, necessitating the use of consecutive blood samples every 4-8 hours at the clinic to determine whether an upward trend in ACS biomarker concentrations is detected.

There are a few types of enzymes that are secreted in the serum of ACS patients. Those include “cardiac enzymes (including troponin and creatine kinase), C-reactive protein (CRP), fibrinogen, homocysteine, lipoproteins, triglycerides, brain natriuretic peptide (BNP) and prothrombin”[2]. These proteins are released from damaged heart muscle cells into the extracellular space, from which they diffuse into the bloodstream. Creatine kinase is one of the most commonly detected enzymes for ACS. However, it is not specific to cardiac diseases. Cardiac Troponin is a heart disease specific protein. Together, the detection of both creatine kinase and cardiac troponin may be used to diagnose with ACS.

b) Paper-Based Diagnostic Devices

There are several at-home diagnostic devices currently available such as glucose sensor and pregnancy tests. Glucose sensors detect the glucose levels by measuring the change in pH produced by reacting blood glucose with glucose-oxidase. This allows for range of output levels. On the other hands, pregnancy tests take advantage of the antibody-specificity and by measuring hCG (human chorionic gonadotrophin) gives a positive/negative binary output. It requires a pair of antibodies that specifically bind to hCG one of which is coupled to gold-nanoparticles as well as an antibody that bind to the antibody. The concept is widely applied to produce other diagnostic devices such as influenza diagnostic and malaria diagnostics. This is a very user-friendly diagnostic device since 1. it does not require any additional laboratory measurement devices, and 2. the result is shown in binary manner and does not require any additional computations or interpretations. Disadvantage might include unspecific binding of the antibodies, low substrate concentration and no accurate detection gradients can be measured. There are a few other biosensing measurement methods such as pH change detection (inspired by pH strips) , Western blotting, and colorimetric assay [5] in laboratory use. Application of those methods might also lead to accessible at home-base diagnostics. Home-based diagnostic examination can omit the trouble of visiting doctors for an examination, and save time since the results are rapidly displayed.

Our goal is to suggest a more approachable, at home diagnostic examination method that allows patients to more easily interpret whether their symptoms are ACS-relavant, to better assess the extent of cardiac muscle damage they have, and also to serve as a basis for long-term monitoring of ACS biomarkers.

Our Idea

In order to help people better assess the severity of their heart-attack-like symptoms (ex: chest pain), we propose engineering a paper-based diagnostic platform for acute coronary syndrome to help users better assess the risks associated with their symptoms and get to the hospital on time if indicated by the diagnostic platform. Currently, many patients are unsure of whether their symptoms of chest pain are significant and hesitate in going to the hospital. Our paper-based diagnostic platform may be used in all households, and especially with at-risk patients, helping them assess their cardiac troponin and CPK levels in a highly-accessible and easy manner. Furthermore, not only will it be of use in situations of acute symptoms, but it may also be used in long-term monitoring in at-risk patients.

We imagine our paper-based diagnostic to operate accordingly:

1. The paper-based diagnostic tool itself will be a small paper strip, similar to pregnancy strips.

2. It will be composed of a microfluidic chamber/filter which separates out plasma from blood drawn from a finger prick.

3. The plasma will then be assayed for the presence of ACS biomarkers such as cardiac Troponin and CPK via signal amplification of CPK and troponin [the mechanism for this is still in making].

4. The result of the signal amplification will be detected, whether as a gradient of colors, the presence of certain bands on the diagnostic strip, etc.

5. A control band should be shown on the strip to confirm that the strip is operational.

There may be a possibility of extending our proposed device to include multiplexing.