Time is Muscle

Toward a patient-centered approach to diagnosing heart attacks at the point of care

3D renders by Sam Bruce, project completed as part of James Intrilligator's Product Design course at Tufts University

Background

In the United States, someone has a heart attack every 40 seconds. About 735,000 people in the U.S. have heart attacks each year. Of those, about 120,000 die.

During an acute myocardial infarction (AMI), the medical term for heart attack, heart muscle becomes damaged by lack of oxygen, and unless blood flow returns within minutes, muscle damage increases and the heart’s ability to pump blood is compromised. If the clot can be dissolved within a few hours, damage to the heart can be reduced. Untreated heart attack symptoms can lead to serious complications or even death.
A biomarker called troponin is the gold standard for diagnosing heart attacks. When there is damage to the heart muscle, troponin is released into the blood. Taking troponin levels repeatedly over time can help differentiate other causes of heart damage from AMIs.

Today, high-sensitivity cardiac troponin (hsTn) in hospitals can identify a heart attack in under 3 hours, but hsTn levels are not taken early enough or often enough to facilitate such fast identification of AMI sufferers. This is due to the complexities in taking troponin: blood must be drawn, handled, and assessed in a lab. This requires the appropriate training of operators, quality control and quality assurance programs. This puts a strain of time and money on a system already strapped for both resources.

What is needed is a human-centered way to measure troponin in patients that provides accurate and consistent measurements of the cardiac biomarker.


User Research

There were a number of user wants and needs to consider here:

First, would patients be open to taking their troponin reading? Did those who were considered “at risk” for an AMI know what troponin was? Would we need to consider an educational campaign? How would HPs on the front lines feel about giving patients the ability to measure troponin?
Maybe most importantly, do cardiologists see significant value in fundamentally changing how AMIs are diagnosed?

Working with my colleague, a cardiologist and inventor himself, provided incredibly valuable insight in both the user needs, concerns, and pain points, but also in the current clinical workflows that are enacted when an AMI is suspected.

CLIMBER HCD analysis


Patients in black, healthcare providers (EMS, Cardiologists, etc) in blue

Customer

Fears
  • Dying of a heart attack
  • Suffering another heart attack
  • Not knowing if they are having a heart attack
  • Not being able to call for help when having a heart attack
  • Not getting a patient to the Cath-lab in time
  • ER filling up with patients, impeding care
Loves
  • Family, friends
  • Watching TV, eating junk food, being lazy
  • Not watching cholesterol
  • Caring for people
  • Having as much data about a patient as possible
Aspirations
  • Living a worry-free life
  • Living until 100 years old
  • Watching kids grow up
  • Success at work
  • Seeing cardiac care improve
Traits
  • Anxious about health
  • Not skilled in or excited about sampling own blood
  • Committed to providing the best care that they can to their patients

Life

Relations
  • Spending time with family
  • Spending time alone
  • Varied contact with healthcare providers
  • Tries to keep close tabs on patients
  • Communication with other HPs
Activities
  • Infrequent doctors visits
  • Exercises (or tries to)
  • Eats healthy (ya, right)
  • Long shifts, late nights, overwhelmingly busy
Mappings
  • Lines of communication between family members and friends about health
  • Lines of communication between other HPs and patients
Problems
  • High cholesterol
  • High blood pressure
  • Far from large hospital
  • Feels in the dark about own heart health
  • Too many patients to be able to provide adequate care to each
  • Feels personally responsible when patient does not have ideal outcome
  • Feels disconnected from patients both about their health, and communication

Insight

Brainstorm
  • How might we troponin measurements to patients?
  • How might we make it so that patients are able to measure troponin DURING a heart attack? · How might we do so without using blood samples?
  • What are the human factors involved in measuring blood biomarkers through the skin?
Analyze
  • The science behind measuring blood analytes noninvasively
  • How much time this could save a patient living in a rural community
  • Ways to make sure the alerts are perceived and heeded correctly
Synthesize
  • Raman stereoscopy research validates its use for measuring concentrations of troponin in blood
  • Research validates the use of transdermal Raman stereoscopy for measuring biomarker analytes in blood
  • The most ideal location to do so on the body are the fingertips
Examine
  • Pressure and location of fingertips on sensors to attain valid measurements
  • Duration of time required of fingertips on sensors to attain valid measurements
  • Ability of patients experiencing AMIs to attain valid measurements
  • Ways to best prompt users to take proper action in accordance with measurements attained

Mechanism

  • Mitigation of pressure application with pressure-sensing sensors to attain valid measurements
  • Assistance provided by integrated display to assist user in applying correct amount of pressure for correct amount of time to attain valid measurements
  • In attempt to eliminate concerns of loss of power, long flexible & resilient power cord included with device

User Flow

To illustrate how a POC troponin measurement device would affect the diagnosis of heart attacks, our colleague helped us develop a business model diagram (BPNM). A simplified version of the diagram can be seen here, depicting the disparity in “time to balloon” between the current system -without the Topopro - and with it would look for a patient experiencing an AMI in a rural setting.

Along with assistance from my colleague who gave insight on the cardiologist's portion of the flow, I interviewed several EMTs and folks who had suffered AMIs themselves or had a loved one who has.

Market Research

We reviewed two devices on the market to aid in the diagnosis of heart attacks. Both of these devices exist at the point of care (POC), but both fall short in making a meaningful dent in expediting the diagnosis of AMIs.

The iStat by Abbott

The iStat is a pretty amazing step forward in decreasing the time to take blood tests to diagnose AMIs. With a troponin cartridge, EMTs are able to measure the amount of the biomarker considered to be a gold standard in evaluating heart attacks. Utilizing the new high-sensitivity troponin I assay, the iStat is able to take quantitative measurements that give a window into the state of a patient's cardiac muscle within ten minutes, without leaving the patient’s side. Unfortunately, this is not enough. Due to the tactile adeptness and required risk of harm associated with both obtaining and analyzing samples and preparing them for measurement, a patient should never and would never be able to safely obtain a reading on their own, especially if suffering an AMI at the time. While bringing troponin measurements to the POC is beyond fantastic for healthcare professionals and patients, the fact that the measurements cannot be taken before healthcare professionals (HPs) arrive on the scene wastes precious time in attaining a first troponin reading, especially when considering the importance of serial troponin measurements.


The Kardiamobile by AliveCor

The Kardiamobile by AliveCor brings cardiac diagnostics home in a very user centered way. By utilizing recent AliveCor’s proprietary technology that converts electrical impulses from user’s fingertips into ultrasound signals transmitted to the mobile device’s microphone.

Portable and effective, the Kardiamobile can fit in your pocket and be used to record heart rhythms virtually anywhere, providing instant analysis for monitoring pathologies of all sorts, including Atrial Fibrillation, Bradycardia, and Tachycardia with an easy-to-understand app. The technology provides a lot of value when it comes to maintaining cardiac health, but when it comes to reliably diagnosing heart attacks, the Kardiamobile falls short: lots of heart attacks don’t present with an electrical signal recognized as an AMI (STEMI). In fact, the Kardiamo- bile is not cleared by the FDA to diagnose a heart attack.

Product Design


In his paper, Deng (2012) describes how human tissue at the fingertip is relatively “transparent” in the near infrared spectral range (NIR), providing the opportunity for NIR light to penetrate and measure blood analytes using Raman spectroscopy. With this knowledge and with information regarding the the requirements of placement, duration of application of finger to sensor, and pressure of application, our first iteration of the Topopro was born, shown below.

NIR Raman Spectroscopy

Raman spectroscopy is a non-destructive technique that analyzes the scattering of light to provide measurement of chemical compositions, such as the concentrations of analytes. Raman spectroscopic analysis of blood (left) has been present for more than four decades, and has recently proven useful in accurate analysis and measurement of cardiac troponin in blood samples. (Lee, 2019)
Small but mighty
We drew inspiration from AliveCor’s Kardiamobile personal ECG, but integrated a larger battery fixture as a base to support a more power-demanding technology. POC troponin measurements will be able to be taken by patients when they first experience symptoms of an AMI, and paving the way for faster heart attack diagnosis.
Stability clasp
Based off of our initial design but iterating to ensure that the hsTn measurement is reliable, a implemented a clasp that holds the user's thumb in place while reading through the (larger) fingernail, and can be used on a surface or while being held.

Human Factors Requirements and Standards

Below is a non-exhaustive list of applicable human factors standards that apply to the Topopro. Below that is a sample of human factors requirements developed for the Topopro to ensure it meets or exceeds the applicable standards.

Standards
  1. ISO 14971: Use alerts for hazardous conditions, such as a “low battery” alert when an un- expected loss of the device’s operation could cause harm or death.
  2. 4.5.3 Make systems error-resistant: Users shall be protected from making errors to the maximum possible extent. [Source: Martin & Dong, 1999]
Requirements
  1. Connectivity: When issued, the device shall be configured to wirelessly interface with the user’s healthcare team, including but not limited to their cardiologist and general practitioner. It shall also be configured to contact the nearest EMS when/if necessary, as described below.
  2. hsTn Memory: hsTn measurements must be stored in memory and not erased until explicitly directed to.
  3. hsTn Threshold: If the rule-in threshold for hsTn of (52 ng/L) is detected, user must not only be adequately alerted of the AMI diagnosis, but instructed with clarity as to what actions to take, their HP team must be alerted, and an ambulance automatically summoned to their location.
  4. Serial hsTn: The device shall prompt the users with a blinking green light in the power indicator and a repeated audible chirp to measure their troponin levels at specified time increments in accordance with the current ACC standards
  5. hsTn Delta: Even when the hsTn levels fall below the absolute rule-in threshold, if the disparity between hsTn measurements exceed ≥15 ng/L in 1 hour, the user must be alerted in accordance with HFR of the hsTn Threshold.
  6. Size and weight: The device will measure 7inx4in and weigh no more than 2lbs.
  7. Charging cord: The charging cord included with the device must be more than 2 meters long and provide enough flexibility and mechanical resilience to wrap around corners at angles exceeding 90 degrees.
  8. Full Charge: When fully charged and not plugged into a power source, device must be able to remain powered and functional for >2 weeks (>672 hrs)
  9. Low Battery: When battery is low and needs recharging (below 20% of full charge) the power indicator will flash orange the unit will sound a “chirp” every 15 seconds
  10. Placement Indicators: The device shall present clear indicators for where and how to place fingertips to attain a successful measurement of biomarker levels, and if fingers are not placed correctly, clear mitigations shall be presented to the user on the integrated digital display.
  11. Pressure Mitigation: To ensure that the proper pressure of the fingertips to sensors is applied, the device will offer resistance and give to compensate. If a pressure is applied that is not able to be mitigated with this means, clear instructions will be presented to the user as to how to readjust their pressure to attain a successful measurement of biomarkers on the digital display.

© 2019 David Pindrys