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False Positive on Cardiac Stress Tests May Be True Indication of Heart Dysfunction

When patients fail cardiac stress tests but pass follow-up exams, doctors usually send them home, saying the stress test results must have been a fluke.

But researchers at the Cedars-Sinai Heart Institute have examined studies on false positives and determined they actually may be true early warnings of pending heart dysfunction. Using new imaging technology, they have identified “novel predictors” that may help determine which patients actually are at risk of developing heart dysfunction.

They presented their findings at the American Heart Association Scientific Sessions Monday, Nov. 15, 2010. The poster presentation, Mechanisms of False Positive Exercise Electrocardiographic Testing: An Investigation by Advanced Echocardiography, will be available from 9:30 to 11 a.m.

This is one of four Cedars-Sinai Heart Institute poster presentations scheduled for Monday. The other three are outlined below and focus on:

  • Exploring the mechanisms of sudden cardiac arrest
  • The role of socioeconomic status in cases of sudden cardiac arrest
  • Higher resting heart rates associated with increased risk of sudden cardiac arrest

Exploring the mechanisms of sudden cardiac arrest

Led by Sumeet Chugh, MD, chief of clinical cardiac electrophysiology at the Cedars-Sinai Heart Institute, cardiologists carrying out the Oregon Study, the largest ongoing population study on sudden cardiac arrest, will present new information on this mysterious and usually fatal disorder. Unlike heart attacks, which occur when the heart muscle is deprived of oxygen, sudden cardiac arrest is usually caused by defective electrical impulses. Patients often have little or no warning and the disorder results in instant death in more than 99 percent of cases.

“Lifetime Clinical History of Syncope is Associated with Future Pulseless Electrical Activity vs. Ventricular Fibrillation” will be a “Digital Dialogue” session presented at 9:45 to 9:53 a.m. (Session 16266/ADD 400.02.)

This study examined two types of sudden cardiac arrest onset, both involving the ventricles, the heart’s pumping chambers. “Pulseless electrical activity” describes a condition in which a patient is unresponsive and has no detectable pulse but there is ongoing organized electrical activity in the heart. In contrast, “ventricular fibrillation” occurs when electrical malfunctions interfere with the heart’s ability to pump. Pulseless electrical activity cases are increasing and have a much lower survival rate than those of ventricular fibrillation. In recent studies, the researchers found that patients suffering from pulseless electrical activity – compared with those with ventricular fibrillation – had a much higher prevalence of fainting or temporarily blacking out during their lifetimes.

Socioeconomic status and sudden cardiac arrest in the United States and Canada

“Socioeconomic Disparities and Burden of Sudden Cardiac Arrest in Metropolitan Areas: A USA-Canada Comparative Analysis” is a poster presentation that will be available from 3 to 4:30 p.m. Researchers from Cedars-Sinai and eight other organizations and medical facilities reviewed statistics on cardiac arrests in several large cities in the United States and Canada.
Sudden cardiac arrest incidence was consistently higher in poorer neighborhoods, and the disparity was more evident in the United States than in Canada. “These findings underscore the important association of socioeconomic status with sudden cardiac arrest, also suggesting that fundamental differences between the two countries may contribute to the greater adverse impact of socioeconomic status in the U.S.,” the researchers concluded. (Session 18723/204/APS 211.03.)

Higher resting heart rate associated with greater risk of sudden cardiac death

“Resting Heart Rate is a Significant Predictor of Sudden Death in the General Population” is a poster presentation that may be viewed from 3 to 4:30 p.m. (Session 18095/2049 APS 211.03.)

Researchers reviewed statistics on patients with coronary artery disease who suffered sudden cardiac arrest, comparing them with other heart disease patients who did not have sudden cardiac arrest. They found that patients with heart disease who went on to experience sudden cardiac arrest tended to have more incidents of atrial fibrillation (rhythm abnormalities) and higher resting heart rates. Heart rate was seen as a significant predictor of which patients were at higher risk for sudden cardiac arrest.

Citation: The American Heart Association Scientific Sessions 2010, Nov. 14-17, Chicago.