IMSS sped up heart-attack transfers with WhatsApp ECG sharing

A patient arriving at a low-specialty hospital with a severe heart attack (STEMI) often needs transfer to a high-specialty cardiac center for angioplasty, but that decision depends on a cardiologist elsewhere reviewing the ECG and confirming the transfer is worth the risk of moving the patient -- a review that historically happened over the phone, describing results verbally rather than showing them.

Mexico's Instituto Mexicano del Seguro Social (IMSS), the country's social security health system, needed a way to coordinate cross-hospital transfers fast across a fragmented public hospital network without waiting years for custom software to be built, procured, and rolled out to every site.

Starting in 2015, IMSS's Código Infarto protocol had doctors at low- and high-specialty hospitals form ordinary WhatsApp group chats, photographing and sending ECG scans through the same free consumer messaging app already installed on every physician's phone rather than commissioning purpose-built clinical software. A distant cardiologist could review the actual ECG image and confirm or decline a transfer within minutes, with no procurement cycle and no training curve, since the tool was already familiar to every doctor using it.

Used WhatsApp groups to send ECG photos, letting the specialist see the image directly with zero procurement delay and no training curve, as doctors already had the app.

Doctors already had WhatsApp installed and knew how to use it, so there was no training or adoption delay.

Sending ECG images let cardiologists see the actual data instead of relying on verbal descriptions, improving decision speed and accuracy.

Zero procurement and deployment cost allowed the program to scale across many hospitals quickly.

The familiar tool reduced friction, so doctors actually used it, unlike new software that might be ignored.

Before building custom software, check if an existing consumer tool everyone already uses can solve the coordination problem with zero adoption cost.

An academic evaluation by David Almog (Northwestern) and Ari Bronsoler (MIT), published as a 2025 working paper, found the group-chat coordination program significantly increased both transfer rates and survival for heart attack patients, with the largest survival gains at general hospitals with the biggest productivity gap relative to high-specialty centers, and among moderately ill patients well enough to survive a transfer but sick enough to need one. 6% reduction, bringing outcomes in line with 2019 OECD averages.