Thursday, September 16, 2010

Heart Attacks: How Early Should We Intervene?


There you are sitting outside on a warm, sunny day having a leisurely picnic with your family. You hear an ambulance in the distance getting closer. You’re not on call.

Suddenly, the paramedics hop from the vehicle’s cabin and pronounce:
“Excuse me sir, your heart's not getting enough oxygen and you might develop a heart attack. Please, come with us.”
Sound far fetched? Well, maybe not.

A new device is being tested that might detect “silent” ischemia and notify the patient (or even call 911) that they are showing signs of heart ischemia on the wire installed in their chest:
The AngelMed system uses a device, similar in size to a pacemaker, which is implanted in the left pectoral region of the chest and has a lead with an electrode to the right ventricle. If there are ischemic changes of significance, an algorithm in the AngelMed Guardian system will identify these electrocardiographic ST changes and alert the patient. It is the same as a positive treadmill test or abnormal EKG, but can be identified much earlier in many patients. To notify the patient, the device will give either a “911” signal, which directs the patient to immediately go to the ER or call the paramedics, or a “Call your doctor” signal, which is a different signal pattern that originates with the implanted device and is sent via telemetry to a hand-held telemetry device carried by the patient. In addition, the signal provides an audible as well as vibratory ring under the skin, so if the patient has difficulty hearing, they can still sense the vibration and know when to call a physician.
Gee - just think how this device could reduce our door-to-balloon time!

On a more serious note, I have often wondered about patients’ acceptance of such “screening” cardiac devices. Will patients want to have such an invasive device that might interrupt their life at any time before they feel bad? What might be the psychologic implications of such a device?

Given what we know about our ability to predict heart attacks, the potential for underdetection (false negative) or overdetection (false positives) due to the many causes of ST segment shifts, and the need to now prove superiority (rather than just non-inferiority) of devices clinically, I wonder if this innovation ever stands a chance to catch on.

Still, Inspector Gadget would be proud.



CardioNP said...

I've encountered pts who would probably agree to such devices. Unfortunately they are the same ones who have had half a dozen coronary CT or full body CT scans before the age of 50.
Under future healthcare allocation schemes, see no way that these would be implanted unless paid for out of pocket.

Elaine Schattner, M.D. said...

I agree it would be hard to persuade people, even those who know they're at elevated risk, to take on a medical device like this. And it could have a paradoxical effect, by not working properly or "reassuring" people they're OK, when they're really ischemic. That said, the potential of this sort of device - for averting MIs - seems huge.