A heart attack occurs when a part of the heart muscle is deprived of oxygenated blood. It’s usually the result of an accumulation of fatty deposits (plaque) that builds along the walls of the arteries. If a piece of the plaque ruptures, or breaks open, the body may sense this as an injury and try to repair the damage. Clots form over the break. These clots can accumulate and impede or block the flow of blood through the affected artery. A blockage can also occur if a piece of plaque becomes caught in a narrower portion of a coronary artery, or if the plaque builds up and closes off the vessel. No matter what causes the blockage, the heart muscle can only go for a few minutes without oxygen and the affected tissue will soon die. This is called a myocardial infarction, or heart attack.
This year, the American Heart Association estimates about 1,255,000 Americans will have a heart attack. In addition, another 195,000 silent heart attacks (i.e., the patient is unaware of the damage) are expected to occur. About 15 percent of those who have a heart attack die, many before they reach the hospital. Those who survive are 1.5 times more likely to die than those in the general population.
“Guarding” Against Future Heart Attacks
The sooner a heart attack is treated (i.e., blood flow is restored to the heart muscle), the less likely there will be damage to the heart and the greater the chance for patient survival. Unfortunately, many people with chest pain don’t seek help right away. Significant delays can lead to serious debilitation or death.
Roughly 37 percent of heart attacks in the U.S. occur in patients who have had a prior heart attack. Yet, even these patients may not recognize or feel the symptoms of another heart attack. Now, researchers are testing a device, called the AngelMed Guardian® System, which is designed to provide an early warning to a possible heart attack.
The Guardian system consists of several components. A wire lead is attached to the right ventricle (located at the bottom tip of the lower right chamber of the heart). The other end of the wire is connected to an implanted monitor. The monitor records the heart’s electrical signals 24 hours a day. The last component is a pager-type device carried by the patient.
The Guardian monitors a particular point in the heart rhythm cycle, called the ST-segment. An elevated ST-segment occurs when blood flow to a part of the heart is cut off. Ashish Pershad, M.D., Cardiologist with Banner Good Samaritan Medical Center in Phoenix, AZ, says the ST segment can become elevated before a patient has any warning signs or symptoms of a heart attack. If the Guardian system detects this elevation, the implanted monitor vibrates and sends a signal to the pager device, which then beeps and flashes.
The Guardian provides two different levels of alert. A low level warning is given when the heart beats too rapidly or in some other abnormal rhythm. This low warning lets the patient know that a physician should be consulted within 24 hours. The high warning is given when the monitor detects the ST-segment changes that imply an impending heart attack. Pershad says with the high warning, the pager will beep at a fast rate to signal the need for immediate medical attention.
The AngelMed Guardian system is being tested in Phase III clinical trial. Pershad says, the trial is open only to heart attack patients who are at high risk for recurrence. The trial is called, AngelMed for Early Recognition and Treatment of STEMI (ALERTS). For more information, go to http://clinicaltrials.gov, then type the trial identification number in the search box: NCT00781118.
AUDIENCE INQUIRYFor information about the clinical trial, go to http://clinicaltrials.gov, then type the trial identification number in the search box: NCT00781118.
For information about the AngelMed Guardian® System, go to http://www.angel-med.com
For general information on heart disease or heart attacks:
American Heart Association, http://www.heart.org
National Heart, Lung and Blood Institute, http://www.nhlbi.nih.gov
BIBLIOGRAPHYFischell, T., et al., “Real-time Detection and Alerting for Acute ST-Segment Elevation Myocardial Ischemia Using an Implantable, High-fidelity, Intracardiac Electrogram Monitoring System with Long-range Telemetry in an Ambulatory Porcine Model,” Journal of the American College of Cardiology, December 2006, Vol. 48, No. 11, pp. 2306-2314.
Fischell, Tim, M.D., et al., “Initial Clinical Results Using Intracardiac Electrogram Monitoring to Detect and Alert Patients During Coronary Plaque Rupture and Ischemia,” Journal of the American College of Cardiology, November 2010, Vol. 56, No. 4, pp. 1089-1098.
Hopenfeld, Bruce, Ph.D., et al., “The Guardian: An Implantable System for Chronic Ambulatory Monitoring of Acute Myocardial Infarction,” Journal of Electrocardiology, November 2009, Vol. 42, No. 6, pp. 481-486.
Krucoff, M., “From ST-Elevation Myocardial Infarction to ST Elevation with no Myocardial Infarction,” Journal of Electrocardiology, November-December 2009, Vol. 42, No. 6, pp. 487-493.